Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Ocean.

PubMed

Murton, Julian B; Bateman, Mark D; Dallimore, Scott R; Teller, James T; Yang, Zhirong

2010-04-01

The melting Laurentide Ice Sheet discharged thousands of cubic kilometres of fresh water each year into surrounding oceans, at times suppressing the Atlantic meridional overturning circulation and triggering abrupt climate change. Understanding the physical mechanisms leading to events such as the Younger Dryas cold interval requires identification of the paths and timing of the freshwater discharges. Although Broecker et al. hypothesized in 1989 that an outburst from glacial Lake Agassiz triggered the Younger Dryas, specific evidence has so far proved elusive, leading Broecker to conclude in 2006 that "our inability to identify the path taken by the flood is disconcerting". Here we identify the missing flood path-evident from gravels and a regional erosion surface-running through the Mackenzie River system in the Canadian Arctic Coastal Plain. Our modelling of the isostatically adjusted surface in the upstream Fort McMurray region, and a slight revision of the ice margin at this time, allows Lake Agassiz to spill into the Mackenzie drainage basin. From optically stimulated luminescence dating we have determined the approximate age of this Mackenzie River flood into the Arctic Ocean to be shortly after 13,000 years ago, near the start of the Younger Dryas. We attribute to this flood a boulder terrace near Fort McMurray with calibrated radiocarbon dates of over 11,500 years ago. A large flood into the Arctic Ocean at the start of the Younger Dryas leads us to reject the widespread view that Agassiz overflow at this time was solely eastward into the North Atlantic Ocean.

Rapid response of alpine timberline vegetation to the Younger Dryas climate oscillation in the Colorado Rocky Mountains, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reasoner, M.A.; Jodry, M.A.

2000-01-01

Paleobotanical records from two high-altitude (>3,300 m) sites in Colorado show a clear and immediate response to the Younger Dryas climate oscillation. The Black Mountain Lake and Sky Pond records indicate that alpine timberline migrated upslope to near-modern elevations during the late Bolling-Allerod (13.6--12.9 ka). Subsequent declines in arboreal pollen percentages and accumulation rates during the Younger Dryas interval (12.9--11.7 ka) reflect a downslope displacement of the alpine timberline ecotone of 60--120 m in elevation. This change translates to a cooling of summer temperature by {approximately}0.4--0.9 C and is consistent with proposed Younger Dryas advances of alpine glaciers in themore » Rocky Mountains to positions close to Little Ice Age maxima. Alpine timberline readvanced upslope to elevations above both sites between 11.7 and 11.4 ka. The concomitant response of temperature-sensitive alpine timberline vegetation in Colorado and late-glacial changes in North Atlantic thermohaline circulating implicates a rapid, widespread atmospheric transmission of the Younger Dryas climate oscillation.« less

Identification of contrasting seasonal sea ice conditions during the Younger Dryas

NASA Astrophysics Data System (ADS)

Cabedo-Sanz, P.; Belt, S. T.; Knies, J.

2012-12-01

The presence of the sea ice diatom biomarker IP25 in Arctic marine sediments has been used in previous studies as a proxy for past spring sea ice occurrence and as an indicator of wider palaeoenvironmental conditions for different regions of the Arctic over various timescales [e.g. 1, 2]. The current study focuses on high-resolution palaeo sea ice reconstructions for northern Norway during the last ca. 15 cal. kyr BP. Within this study, particular emphasis has been placed on the identification of the sea ice conditions during the Younger Dryas and the application of different biomarker-based proxies to both identify and quantify seasonal sea ice conditions. Firstly, the appearance of the specific sea ice diatom proxy IP25 at ca. 12.9 cal. kyr BP in a marine sediment core (JM99-1200) obtained from Andfjorden has provided an unambiguous but qualitative measure of seasonal sea ice and thus the onset of the Younger Dryas stadial. The near continuous occurrence of IP25 for the next ca. 1400 yr demonstrates seasonal sea ice during this interval, although variable abundances suggest that the recurrent conditions in the early-mid Younger Dryas (ca. 12.9 - 11.9 cal. kyr BP) changed significantly from stable to highly variable sea ice conditions at ca. 11.9 cal. kyr BP and this instability in sea ice prevailed for the subsequent ca. 400 yr. At ca. 11.5 cal. kyr BP, IP25 disappeared from the record indicating ice-free conditions that signified the beginning of the Holocene. Similarly, a high resolution record from the Kveithola Through, western Barents Sea, showed clearly higher IP25 concentrations during the Younger Dryas stadial compared to the Holocene. For both marine records, the IP25 concentrations were also combined with those of the open water phytoplankton biomarker brassicasterol to generate PBIP25 data from which more quantitative measurements of sea ice were determined. The contrasting seasonal sea ice conditions during the Younger Dryas were further verified

Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis.

PubMed

Israde-Alcántara, Isabel; Bischoff, James L; Domínguez-Vázquez, Gabriela; Li, Hong-Chun; DeCarli, Paul S; Bunch, Ted E; Wittke, James H; Weaver, James C; Firestone, Richard B; West, Allen; Kennett, James P; Mercer, Chris; Xie, Sujing; Richman, Eric K; Kinzie, Charles R; Wolbach, Wendy S

2012-03-27

We report the discovery in Lake Cuitzeo in central Mexico of a black, carbon-rich, lacustrine layer, containing nanodiamonds, microspherules, and other unusual materials that date to the early Younger Dryas and are interpreted to result from an extraterrestrial impact. These proxies were found in a 27-m-long core as part of an interdisciplinary effort to extract a paleoclimate record back through the previous interglacial. Our attention focused early on an anomalous, 10-cm-thick, carbon-rich layer at a depth of 2.8 m that dates to 12.9 ka and coincides with a suite of anomalous coeval environmental and biotic changes independently recognized in other regional lake sequences. Collectively, these changes have produced the most distinctive boundary layer in the late Quaternary record. This layer contains a diverse, abundant assemblage of impact-related markers, including nanodiamonds, carbon spherules, and magnetic spherules with rapid melting/quenching textures, all reaching synchronous peaks immediately beneath a layer containing the largest peak of charcoal in the core. Analyses by multiple methods demonstrate the presence of three allotropes of nanodiamond: n-diamond, i-carbon, and hexagonal nanodiamond (lonsdaleite), in order of estimated relative abundance. This nanodiamond-rich layer is consistent with the Younger Dryas boundary layer found at numerous sites across North America, Greenland, and Western Europe. We have examined multiple hypotheses to account for these observations and find the evidence cannot be explained by any known terrestrial mechanism. It is, however, consistent with the Younger Dryas boundary impact hypothesis postulating a major extraterrestrial impact involving multiple airburst(s) and and/or ground impact(s) at 12.9 ka.

Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis

USGS Publications Warehouse

Israde-Alcántara, Isabel; Bischoff, James L.; Domínguez-Vázquez, Gabriela; Li, Hong-Chun; DeCarli, Paul S.; Bunch, Ted E.; Wittke, James H.; Weaver, James C.; Firestone, Richard B.; West, Allen; Kennett, James P.; Mercer, Chris; Xie, Sujing; Richman, Eric K.; Kinzie, Charles R.; Wolbach, Wendy S.

2012-01-01

We report the discovery in Lake Cuitzeo in central Mexico of a black, carbon-rich, lacustrine layer, containing nanodiamonds, microspherules, and other unusual materials that date to the early Younger Dryas and are interpreted to result from an extraterrestrial impact. These proxies were found in a 27-m-long core as part of an interdisciplinary effort to extract a paleoclimate record back through the previous interglacial. Our attention focused early on an anomalous, 10-cm-thick, carbon-rich layer at a depth of 2.8 m that dates to 12.9 ka and coincides with a suite of anomalous coeval environmental and biotic changes independently recognized in other regional lake sequences. Collectively, these changes have produced the most distinctive boundary layer in the late Quaternary record. This layer contains a diverse, abundant assemblage of impact-related markers, including nanodiamonds, carbon spherules, and magnetic spherules with rapid melting/quenching textures, all reaching synchronous peaks immediately beneath a layer containing the largest peak of charcoal in the core. Analyses by multiple methods demonstrate the presence of three allotropes of nanodiamond: n-diamond, i-carbon, and hexagonal nanodiamond (lonsdaleite), in order of estimated relative abundance. This nanodiamond-rich layer is consistent with the Younger Dryas boundary layer found at numerous sites across North America, Greenland, and Western Europe. We have examined multiple hypotheses to account for these observations and find the evidence cannot be explained by any known terrestrial mechanism. It is, however, consistent with the Younger Dryas boundary impact hypothesis postulating a major extraterrestrial impact involving multiple airburst(s) and and/or ground impact(s) at 12.9 ka.

Evidence from Central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis

USGS Publications Warehouse

Israde-Alcántaraa, Isabel; Bischoff, James L.; Domínguez-Vázquez, Gabriela; Li, Hong-Chun; DeCarli, Paul S.; Bunch, Ted E.; Wittke, James H.; Weaver, James C.; Firestone, Richard B.; West, Allen; Kennett, James P.; Mercer, Chris; Xie, Sujing; Richman, Eric K.; Kinzie, Charles R.; Wolbach, Wendy S.; Stanley, Steven M.

2012-01-01

We report the discovery in Lake Cuitzeo in central Mexico of a black, carbon-rich, lacustrine layer, containing nanodiamonds, microspherules, and other unusual materials that date to the early Younger Dryas and are interpreted to result from an extraterrestrial impact. These proxies were found in a 27-m-long core as part of an interdisciplinary effort to extract a paleoclimate record back through the previous interglacial. Our attention focused early on an anomalous, 10-cm-thick, carbon-rich layer at a depth of 2.8 m that dates to 12.9 ka and coincides with a suite of anomalous coeval environmental and biotic changes independently recognized in other regional lake sequences. Collectively, these changes have produced the most distinctive boundary layer in the late Quaternary record. This layer contains a diverse, abundant assemblage of impact-related markers, including nanodiamonds, carbon spherules, and magnetic spherules with rapid melting/quenching textures, all reaching synchronous peaks immediately beneath a layer containing the largest peak of charcoal in the core. Analyses by multiple methods demonstrate the presence of three allotropes of nanodiamond: n-diamond, i-carbon, and hexagonal nanodiamond (lonsdaleite), in order of estimated relative abundance. This nanodiamond-rich layer is consistent with the Younger Dryas boundary layer found at numerous sites across North America, Greenland, and Western Europe. We have examined multiple hypotheses to account for these observations and find the evidence cannot be explained by any known terrestrial mechanism. It is, however, consistent with the Younger Dryas boundary impact hypothesis postulating a major extraterrestrial impact involving multiple airburst(s) and and/or ground impact(s) at 12.9 ka.

Oxygen Isotopes in Fresh Water Biogenic Opal: Northeastern US Alleroed-Younger Dryas Temperature Shift

NASA Technical Reports Server (NTRS)

Shemesh, Aldo; Peteet, Dorothy

1997-01-01

The first oxygen isotope analysis of biogenic opal from lake sediments, from the Allerod/Younger Dryas transition in a core from Linsley Pond, Connecticut, gives an average estimate of a 6 C drop in temperature during the Younger Dryas. This shift represents temperatures during the bloom season, and may be less than the winter temperature drop. The sharp transition itself, with a duration of about 200 years, suggests that the temperature decrease may have been as large as 12 C. Previous estimates of the Allerod/Younger Dryas temperature shifts are controversial, and range from 3-20 C, suggesting that further interdisciplinary research on the same samples is warranted. One way that global climate change manifests itself is by redistributing energy throughout the globe. The Northern Hemisphere latitudinal temperature gradient during the late-glacial is at present a controversial topic. The magnitude of air temperature shifts during the Allerod/Younger Dryas (YD) oscillation are estimated from mid-latitude pollen records surrounding the North Atlantic to be 3-5 C in Europe [Lowe et al., 19941 and 3-4 C in the eastern US [Peteet et al., 1993]. In contrast, lake temperatures estimates derived from aquatic midge larvae in the Canadian eastern maritimes and Maine range from 6-20 C, with larger shifts at more southern sites [Levesque et al., 1997]. The magnitude of YD cooling in Greenland ice cores ranges from at least 7 C from the Bolling warming [Dansgaard et al., 1989] to 15 C - a more recent estimate from borehole temperatures [Cuffey et al., 1995]. The ice core geochemical records reveal that massive frequent and short-term (decadal or less) changes in atmospheric composition occurred throughout this event, suggesting a very dynamic circulation [Mayewski et al., 1993).

The Younger Dryas phase of Great Salt Lake, Utah, USA

USGS Publications Warehouse

Oviatt, Charles G.; Miller, D.M.; McGeehin, J.P.; Zachary, C.; Mahan, S.

2005-01-01

Field investigations at the Public Shooting Grounds (a wildlife-management area on the northeastern shore of Great Salt Lake) and radiocarbon dating show that the Great Salt Lake rose to the Gilbert shoreline sometime between 12.9 and 11.2 cal ka. We interpret a ripple-laminated sand unit exposed at the Public Shooting Grounds, and dated to this time interval, as the nearshore sediments of Great Salt Lake deposited during the formation of the Gilbert shoreline. The ripple-laminated sand is overlain by channel-fill deposits that overlap in age (11.9-11.2 cal ka) with the sand, and by wetland deposits (11.1 to 10.5 cal ka). Consistent accelerator mass spectrometry radiocarbon ages were obtained from samples of plant fragments, including those of emergent aquatic plants, but mollusk shells from spring and marsh deposits yielded anomalously old ages, probably because of a variable radiocarbon reservoir effect. The Bonneville basin was effectively wet during at least part of the Younger Dryas global-cooling interval, however, conflicting results from some Great Basin locations and proxy records indicate that the regional effects of Younger Dryas cooling are still not well understood. ?? 2005 Elsevier B.V. All rights reserved.

Lateglacial landscape and vegetation change and the younger dryas climatic oscillation in New Zealand

NASA Astrophysics Data System (ADS)

McGlone, M. S.

Lateglacial sequences in New Zealand show progressive afforestation and landscape stabilization reflecting a warming climate. Between 14,500 BP and 11,500 BP, afforestation and landscape stability was achieved throughout most of the North Island and the northwest sector of the South Island. In the South Island, scrub and tree ferns were replacing previous grasslands in the east by 11,000 BP, and broadleaved forest was spreading in the west. No significant reversals of these trends occurred and afforestation was complete by 9500 BP. Glaciers of the high central part of the Southern Alps made a series of advances between 14,000 and 9000 BP Most of these advances are poorly dated but two moraines are of Younger Dryas age. Glacial advances in the face of the general Lateglacial warming trend may have been driven by stronger westerly winds increasing snowfall on high altitude névés, and by reduced ablation as a consequence of moist, cloudy, low insolation summers. The cause of the northern hemisphere Younger Dryas cooling is still uncertain, and expected Southern Hemisphere responses may differ according to the mechanism proposed for the cooling. Poor chronological resolution and apparent conflict between the various types of evidence for climatic change make detection of an unambiguous Younger Dryas in New Zealand problematical.

The record of deglaciation in the Sulu Sea: Evidence for the Younger Dryas Event in the tropical western Pacific

NASA Astrophysics Data System (ADS)

Linsley, Braddock K.; Thunell, Robert C.

1990-12-01

A high-resolution, accelerator mass spectroscopy 14C dated sediment record from the Sulu Sea clearly indicates that the Younger Dryas event affected the western equatorial Pacific. Planktonic foraminiferal δ18O and abundance data both record significant changes during Younger Dryas time. In particular, a 0.4‰ increase in the δ18O value of Globigerinoides ruber and the reappearance of the cool water planktonic foraminifera, Neogloboquadrina pachyderma, occur during the Younger Dryas at this location. These isotopic and faunal changes are a response to either surface water temperature or salinity changes, or some combination of the two. Changes in surface salinities could have been accomplished through either local or global processes. Intensification of the monsoon climate system and increased precipitation at approximately 11 ka is one mechanism that may have resulted in local changes in salinity. A meltwater pulse derived from the Tibetan Plateau is another mechanism which may have caused local changes in salinity. The presence of the Younger Dryas in the tropical western Pacific clearly indicates that this climatic event is not restricted to the North Atlantic or high latitudes, but rather is global in extent.

Glacier-derived climate for the Younger Dryas in Europe

NASA Astrophysics Data System (ADS)

Pellitero, Ramon; Rea, Brice R.; Spagnolo, Matteo; Hughes, Philip; Braithwaite, Roger; Renssen, Hans; Ivy-Ochs, Susan; Ribolini, Adriano; Bakke, Jostein; Lukas, Sven

2016-04-01

We have reconstructed and calculated the glacier equilibrium line altitudes (ELA) for 120 Younger Dryas palaeoglaciers from Morocco in the south to Svalbard in the north and from Ireland in the west to Turkey in the east. The chronology of these landform were checked and, when derived from cosmogenic dates, these were recalculated based on newer production rates. Frontal moraines/limits for the palaeoglaciers were used to reconstruct palaeoglacier extent by using a GIS tool which implements a discretised solution for the assumption of perfect-plasticity ice rheology for a single flowline and extents this out to a 3D ice surface. From the resulting equilibrium profile, palaeoglaciers palaeo-ELAs were calculated using another GIS tool. Where several glaciers were reconstructed in a region, a single ELA value was generated following the methodology of Osmaston (2005). In order to utilise these ELAs for quantitative palaeo-precipitation reconstructions an independent regional temperature analysis was undertaken. A database of 121 sites was compiled where the temperature was determined from palaeoproxies other than glaciers (e.g. pollen, diatoms, choleoptera, chironimids…) in both terrestrial and offshore environments. These proxy data provides estimates of average annual, summer and winter temperatures. These data were merged and interpolated to generate maps of average temperature for the warmest and coldest months and annual average temperature. From these maps the temperature at the ELA was obtained using a lapse rate of 0.65°C/100m. Using the ELA temperature range and summer maximum in a degree-day model allows determination of the potential melt which can be taken as equivalent to precipitation given the assumption a glacier is in equilibrium with climate. Results show that during the coldest part of the Younger Dryas precipitation was high in the British Isles, the NW of the Iberian Peninsula and the Vosges. There is a general trend for declining precipitation

Accumulation of impact markers in desert wetlands and implications for the Younger Dryas impact hypothesis.

PubMed

Pigati, Jeffrey S; Latorre, Claudio; Rech, Jason A; Betancourt, Julio L; Martínez, Katherine E; Budahn, James R

2012-05-08

The Younger Dryas impact hypothesis contends that an extraterrestrial object exploded over North America at 12.9 ka, initiating the Younger Dryas cold event, the extinction of many North American megafauna, and the demise of the Clovis archeological culture. Although the exact nature and location of the proposed impact or explosion remain unclear, alleged evidence for the fallout comes from multiple sites across North America and a site in Belgium. At 6 of the 10 original sites (excluding the Carolina Bays), elevated concentrations of various "impact markers" were found in association with black mats that date to the onset of the Younger Dryas. Black mats are common features in paleowetland deposits and typically represent shallow marsh environments. In this study, we investigated black mats ranging in age from approximately 6 to more than 40 ka in the southwestern United States and the Atacama Desert of northern Chile. At 10 of 13 sites, we found elevated concentrations of iridium in bulk and magnetic sediments, magnetic spherules, and/or titanomagnetite grains within or at the base of black mats, regardless of their age or location, suggesting that elevated concentrations of these markers arise from processes common to wetland systems, and not a catastrophic extraterrestrial impact event.

Accumulation of impact markers in desert wetlands and implications for the Younger Dryas impact hypothesis

PubMed Central

Pigati, Jeffrey S.; Latorre, Claudio; Rech, Jason A.; Betancourt, Julio L.; Martínez, Katherine E.; Budahn, James R.

2012-01-01

The Younger Dryas impact hypothesis contends that an extraterrestrial object exploded over North America at 12.9 ka, initiating the Younger Dryas cold event, the extinction of many North American megafauna, and the demise of the Clovis archeological culture. Although the exact nature and location of the proposed impact or explosion remain unclear, alleged evidence for the fallout comes from multiple sites across North America and a site in Belgium. At 6 of the 10 original sites (excluding the Carolina Bays), elevated concentrations of various “impact markers” were found in association with black mats that date to the onset of the Younger Dryas. Black mats are common features in paleowetland deposits and typically represent shallow marsh environments. In this study, we investigated black mats ranging in age from approximately 6 to more than 40 ka in the southwestern United States and the Atacama Desert of northern Chile. At 10 of 13 sites, we found elevated concentrations of iridium in bulk and magnetic sediments, magnetic spherules, and/or titanomagnetite grains within or at the base of black mats, regardless of their age or location, suggesting that elevated concentrations of these markers arise from processes common to wetland systems, and not a catastrophic extraterrestrial impact event. PMID:22529347

Accumulation of impact markers in desert wetlands and implications for the Younger Dryas impact hypothesis

USGS Publications Warehouse

Pigati, Jeffrey S.; Latorre, Claudio; Rech, Jason A.; Betancourt, Julio L.; Martinez, Katherine E.; Budahn, James R.

2012-01-01

The Younger Dryas impact hypothesis contends that an extraterrestrial object exploded over North America at 12.9 ka, initiating the Younger Dryas cold event, the extinction of many North American megafauna, and the demise of the Clovis archeological culture. Although the exact nature and location of the proposed impact or explosion remain unclear, alleged evidence for the fallout comes from multiple sites across North America and a site in Belgium. At 6 of the 10 original sites (excluding the Carolina Bays), elevated concentrations of various "impact markers" were found in association with black mats that date to the onset of the Younger Dryas. Black mats are common features in paleowetland deposits and typically represent shallow marsh environments. In this study, we investigated black mats ranging in age from approximately 6 to more than 40 ka in the southwestern United States and the Atacama Desert of northern Chile. At 10 of 13 sites, we found elevated concentrations of iridium in bulk and magnetic sediments, magnetic spherules, and/or titanomagnetite grains within or at the base of black mats, regardless of their age or location, suggesting that elevated concentrations of these markers arise from processes common to wetland systems, and not a catastrophic extraterrestrial impact event.

Decadal resolved leaf wax δD records of the Younger Dryas in central and eastern Europe

NASA Astrophysics Data System (ADS)

Aichner, Bernhard; Słowiński, Michał; Ott, Florian; Noryśkiewicz, Agnieszka M.; Wulf, Sabine; Brauer, Achim; Sachse, Dirk

2015-04-01

Annually laminated (varved) sediments with defined event-based age anchor points such as tephra layers enable the establishment of precise chronologies in lacustrine climate archives. This is especially useful to study subtle temporal differences in the consequences of mechanisms and feedbacks during abrupt climatic changes such as the Younger Dryas over larger spatial areas. To decipher the drivers of ecological changes across the Allerød/Younger Dryas transition in central Europe, we analyzed leaf wax biomarkers from Trzechowskie paleolake in northern Poland. Samples were taken in 10 years intervals across the onset of the Younger Dryas, with the Laacher See Tephra (12,880 yrs BP) as anchor point for age-calibration. Further, we applied compound specific hydrogen isotope analysis to infer past hydrological changes, in comparison to results from the well-dated Meerfelder Maar record located up 900 km to the southwest [1]. Between 12,750 and 12,600 yrs BP, ratios of terrestrial n-alkanes show a transition from a tree-dominated lake catchment (Pinus, Betula) to an environment mainly covered by Juniperus and grasses, which is in agreement with palynological data. δD values of n-alkanes indicate a rapid cooling and/or a change of moisture source together with a slight aridification between 12,680 and 12,600 yrs BP. This is synchronous to a rapid and strong aridification inferred for the beginning of the Younger Dryas at Meerfelder Maar (western Germany) [1] but ca. 170 yrs after the inferred onset of cooling at both Meerfelder Maar and the NGRIP ice core at 12,850 yrs BP. This highlights a different temporal succession and impact of hydrological and climatic changes in eastern compared to western Europe which could potentially be related to the stronger influence of the Fennoscandian icesheets and/or the Siberian High on atmospheric circulation patterns in the more continental climate influenced parts of eastern Europe. [1] Rach O, Brauer A, Wilkes H, Sachse D

Minimal geological methane emissions during the Younger Dryas-Preboreal abrupt warming event.

PubMed

Petrenko, Vasilii V; Smith, Andrew M; Schaefer, Hinrich; Riedel, Katja; Brook, Edward; Baggenstos, Daniel; Harth, Christina; Hua, Quan; Buizert, Christo; Schilt, Adrian; Fain, Xavier; Mitchell, Logan; Bauska, Thomas; Orsi, Anais; Weiss, Ray F; Severinghaus, Jeffrey P

2017-08-23

Methane (CH 4 ) is a powerful greenhouse gas and plays a key part in global atmospheric chemistry. Natural geological emissions (fossil methane vented naturally from marine and terrestrial seeps and mud volcanoes) are thought to contribute around 52 teragrams of methane per year to the global methane source, about 10 per cent of the total, but both bottom-up methods (measuring emissions) and top-down approaches (measuring atmospheric mole fractions and isotopes) for constraining these geological emissions have been associated with large uncertainties. Here we use ice core measurements to quantify the absolute amount of radiocarbon-containing methane ( 14 CH 4 ) in the past atmosphere and show that geological methane emissions were no higher than 15.4 teragrams per year (95 per cent confidence), averaged over the abrupt warming event that occurred between the Younger Dryas and Preboreal intervals, approximately 11,600 years ago. Assuming that past geological methane emissions were no lower than today, our results indicate that current estimates of today's natural geological methane emissions (about 52 teragrams per year) are too high and, by extension, that current estimates of anthropogenic fossil methane emissions are too low. Our results also improve on and confirm earlier findings that the rapid increase of about 50 per cent in mole fraction of atmospheric methane at the Younger Dryas-Preboreal event was driven by contemporaneous methane from sources such as wetlands; our findings constrain the contribution from old carbon reservoirs (marine methane hydrates, permafrost and methane trapped under ice) to 19 per cent or less (95 per cent confidence). To the extent that the characteristics of the most recent deglaciation and the Younger Dryas-Preboreal warming are comparable to those of the current anthropogenic warming, our measurements suggest that large future atmospheric releases of methane from old carbon sources are unlikely to occur.

Minimal geological methane emissions during the Younger Dryas-Preboreal abrupt warming event

NASA Astrophysics Data System (ADS)

Petrenko, Vasilii V.; Smith, Andrew M.; Schaefer, Hinrich; Riedel, Katja; Brook, Edward; Baggenstos, Daniel; Harth, Christina; Hua, Quan; Buizert, Christo; Schilt, Adrian; Fain, Xavier; Mitchell, Logan; Bauska, Thomas; Orsi, Anais; Weiss, Ray F.; Severinghaus, Jeffrey P.

2017-08-01

Methane (CH4) is a powerful greenhouse gas and plays a key part in global atmospheric chemistry. Natural geological emissions (fossil methane vented naturally from marine and terrestrial seeps and mud volcanoes) are thought to contribute around 52 teragrams of methane per year to the global methane source, about 10 per cent of the total, but both bottom-up methods (measuring emissions) and top-down approaches (measuring atmospheric mole fractions and isotopes) for constraining these geological emissions have been associated with large uncertainties. Here we use ice core measurements to quantify the absolute amount of radiocarbon-containing methane (14CH4) in the past atmosphere and show that geological methane emissions were no higher than 15.4 teragrams per year (95 per cent confidence), averaged over the abrupt warming event that occurred between the Younger Dryas and Preboreal intervals, approximately 11,600 years ago. Assuming that past geological methane emissions were no lower than today, our results indicate that current estimates of today’s natural geological methane emissions (about 52 teragrams per year) are too high and, by extension, that current estimates of anthropogenic fossil methane emissions are too low. Our results also improve on and confirm earlier findings that the rapid increase of about 50 per cent in mole fraction of atmospheric methane at the Younger Dryas-Preboreal event was driven by contemporaneous methane from sources such as wetlands; our findings constrain the contribution from old carbon reservoirs (marine methane hydrates, permafrost and methane trapped under ice) to 19 per cent or less (95 per cent confidence). To the extent that the characteristics of the most recent deglaciation and the Younger Dryas-Preboreal warming are comparable to those of the current anthropogenic warming, our measurements suggest that large future atmospheric releases of methane from old carbon sources are unlikely to occur.

The loess/paleosol record and the nature of the younger dryas climate in central China

USGS Publications Warehouse

Madsen, D.B.; Jingzen, L.; Elston, R.G.; Cheng, X.; Bettinger, R.L.; Kan, G.; Jeff, Brantingham P.; Kan, Z.

1998-01-01

The use of latest Pleistocene-Holocene paleosols in defining Chinese climatic sequences is plagued by poor chronological controls caused primarily by the use of radiocarbon dates derived from bulk soil carbon. Dating of a post-glacial aeolian/paleosol sequence in the Pigeon Mountain basin of north-central China, using culturally deposited charcoal, support a wide array of other data suggesting the Younger Dryas was a period of cooler dryer conditions marked by wide-spread aeolian deposition. Periods of soil formation and higher lake levels bracket this climatic event. Climatic variability immediately before, during and immediately after the Younger Dryas interval is associated with rapid technological elaboration and innovation in the production and use of chipped stone tools, and perhaps, ground stone. ?? 1998 John Wiley & Sons, Inc.

Increased hurricane frequency near Florida during Younger Dryas Atlantic Meridional Overturning Circulation slowdown

USGS Publications Warehouse

Toomey, Michael; Korty, Robert L.; Donnelly, Jeffrey P.; van Hengstum, Peter J.; Curry, William B.

2017-01-01

The risk posed by intensification of North Atlantic hurricane activity remains controversial, in part due to a lack of available storm proxy records that extend beyond the relatively stable climates of the late Holocene. Here we present a record of storm-triggered turbidite deposition offshore the Dry Tortugas, south Florida, USA, that spans abrupt transitions in North Atlantic sea-surface temperature and Atlantic Meridional Overturning Circulation (AMOC) during the Younger Dryas (12.9–11.7 ka). Despite potentially hostile conditions for cyclogenesis in the tropical North Atlantic at that time, our record and numerical experiments suggest that strong hurricanes may have regularly affected Florida. Less severe surface cooling at mid-latitudes (∼20°–40°N) than across much of the tropical North Atlantic (∼10°–20°N) in response to AMOC reduction may best explain strong hurricane activity during the Younger Dryas near the Dry Tortugas and possibly along the entire southeastern coast of the United States.

Bayesian chronological analyses consistent with synchronous age of 12,835-12,735 Cal B.P. for Younger Dryas boundary on four continents.

PubMed

Kennett, James P; Kennett, Douglas J; Culleton, Brendan J; Aura Tortosa, J Emili; Bischoff, James L; Bunch, Ted E; Daniel, I Randolph; Erlandson, Jon M; Ferraro, David; Firestone, Richard B; Goodyear, Albert C; Israde-Alcántara, Isabel; Johnson, John R; Jordá Pardo, Jesús F; Kimbel, David R; LeCompte, Malcolm A; Lopinot, Neal H; Mahaney, William C; Moore, Andrew M T; Moore, Christopher R; Ray, Jack H; Stafford, Thomas W; Tankersley, Kenneth Barnett; Wittke, James H; Wolbach, Wendy S; West, Allen

2015-08-11

The Younger Dryas impact hypothesis posits that a cosmic impact across much of the Northern Hemisphere deposited the Younger Dryas boundary (YDB) layer, containing peak abundances in a variable assemblage of proxies, including magnetic and glassy impact-related spherules, high-temperature minerals and melt glass, nanodiamonds, carbon spherules, aciniform carbon, platinum, and osmium. Bayesian chronological modeling was applied to 354 dates from 23 stratigraphic sections in 12 countries on four continents to establish a modeled YDB age range for this event of 12,835-12,735 Cal B.P. at 95% probability. This range overlaps that of a peak in extraterrestrial platinum in the Greenland Ice Sheet and of the earliest age of the Younger Dryas climate episode in six proxy records, suggesting a causal connection between the YDB impact event and the Younger Dryas. Two statistical tests indicate that both modeled and unmodeled ages in the 30 records are consistent with synchronous deposition of the YDB layer within the limits of dating uncertainty (∼ 100 y). The widespread distribution of the YDB layer suggests that it may serve as a datum layer.

Bayesian chronological analyses consistent with synchronous age of 12,835-12,735 Cal B.P. for Younger Dryas boundary on four continents

NASA Astrophysics Data System (ADS)

Kennett, James P.; Kennett, Douglas J.; Culleton, Brendan J.; Emili Aura Tortosa, J.; Bischoff, James L.; Bunch, Ted E.; Daniel, I. Randolph, Jr.; Erlandson, Jon M.; Ferraro, David; Firestone, Richard B.; Goodyear, Albert C.; Israde-Alcántara, Isabel; Johnson, John R.; Jordá Pardo, Jesús F.; Kimbel, David R.; LeCompte, Malcolm A.; Lopinot, Neal H.; Mahaney, William C.; Moore, Andrew M. T.; Moore, Christopher R.; Ray, Jack H.; Stafford, Thomas W., Jr.; Barnett Tankersley, Kenneth; Wittke, James H.; Wolbach, Wendy S.; West, Allen

2015-08-01

The Younger Dryas impact hypothesis posits that a cosmic impact across much of the Northern Hemisphere deposited the Younger Dryas boundary (YDB) layer, containing peak abundances in a variable assemblage of proxies, including magnetic and glassy impact-related spherules, high-temperature minerals and melt glass, nanodiamonds, carbon spherules, aciniform carbon, platinum, and osmium. Bayesian chronological modeling was applied to 354 dates from 23 stratigraphic sections in 12 countries on four continents to establish a modeled YDB age range for this event of 12,835-12,735 Cal B.P. at 95% probability. This range overlaps that of a peak in extraterrestrial platinum in the Greenland Ice Sheet and of the earliest age of the Younger Dryas climate episode in six proxy records, suggesting a causal connection between the YDB impact event and the Younger Dryas. Two statistical tests indicate that both modeled and unmodeled ages in the 30 records are consistent with synchronous deposition of the YDB layer within the limits of dating uncertainty (∼100 y). The widespread distribution of the YDB layer suggests that it may serve as a datum layer.

Widespread platinum anomaly documented at the Younger Dryas onset in North American sedimentary sequences

PubMed Central

Moore, Christopher R.; West, Allen; LeCompte, Malcolm A.; Brooks, Mark J.; Daniel, I. Randolph; Goodyear, Albert C.; Ferguson, Terry A.; Ivester, Andrew H.; Feathers, James K.; Kennett, James P.; Tankersley, Kenneth B.; Adedeji, A. Victor; Bunch, Ted E.

2017-01-01

Previously, a large platinum (Pt) anomaly was reported in the Greenland ice sheet at the Younger Dryas boundary (YDB) (12,800 Cal B.P.). In order to evaluate its geographic extent, fire-assay and inductively coupled plasma mass spectrometry (FA and ICP-MS) elemental analyses were performed on 11 widely separated archaeological bulk sedimentary sequences. We document discovery of a distinct Pt anomaly spread widely across North America and dating to the Younger Dryas (YD) onset. The apparent synchroneity of this widespread YDB Pt anomaly is consistent with Greenland Ice Sheet Project 2 (GISP2) data that indicated atmospheric input of platinum-rich dust. We expect the Pt anomaly to serve as a widely-distributed time marker horizon (datum) for identification and correlation of the onset of the YD climatic episode at 12,800 Cal B.P. This Pt datum will facilitate the dating and correlating of archaeological, paleontological, and paleoenvironmental data between sequences, especially those with limited age control. PMID:28276513

Widespread platinum anomaly documented at the Younger Dryas onset in North American sedimentary sequences

NASA Astrophysics Data System (ADS)

Moore, Christopher R.; West, Allen; Lecompte, Malcolm A.; Brooks, Mark J.; Daniel, I. Randolph; Goodyear, Albert C.; Ferguson, Terry A.; Ivester, Andrew H.; Feathers, James K.; Kennett, James P.; Tankersley, Kenneth B.; Adedeji, A. Victor; Bunch, Ted E.

2017-03-01

Previously, a large platinum (Pt) anomaly was reported in the Greenland ice sheet at the Younger Dryas boundary (YDB) (12,800 Cal B.P.). In order to evaluate its geographic extent, fire-assay and inductively coupled plasma mass spectrometry (FA and ICP-MS) elemental analyses were performed on 11 widely separated archaeological bulk sedimentary sequences. We document discovery of a distinct Pt anomaly spread widely across North America and dating to the Younger Dryas (YD) onset. The apparent synchroneity of this widespread YDB Pt anomaly is consistent with Greenland Ice Sheet Project 2 (GISP2) data that indicated atmospheric input of platinum-rich dust. We expect the Pt anomaly to serve as a widely-distributed time marker horizon (datum) for identification and correlation of the onset of the YD climatic episode at 12,800 Cal B.P. This Pt datum will facilitate the dating and correlating of archaeological, paleontological, and paleoenvironmental data between sequences, especially those with limited age control.

Younger Dryas glacial stillstands on the Bolivian Altiplano: pattern and climatic implications

NASA Astrophysics Data System (ADS)

Martin, Léo; Blard, Pierre-Henri; Lave, Jérôme; Premaillon, Melody; Charreau, Julien; Jomelli, Vincent; Brunstein, Daniel

2014-05-01

Modifications of the global climate during the last deglaciation have been characterized by regional reorganization that may have in turn amplified or attenuated the global changes. Notably, the respective influences of the Southern and Northern Hemispheres are poorly understood in the Tropics. This underlines the importance of studying past climate variations in the Tropics, particularly in the poorly documented tropical moutain areas. Cosmogenic exposure dating applied to the glacial landscapes provides temporal constraints on glacier fluctuations in response of climate variations. This permits high-resolution reconstructions of regional climates. In this work we present new cosmogenic ages from two different locations of the Bolivian Altiplano, the Nevado Sajama volcano (S18.11° - W66.88°) and the Zongo Valley (S16.25°- W68.11°). On the Sajama, new cosmogenic 3He dates support a late local glacial maximum, synchronous with the plaeolake Tauca highstand (ca. 16 ka) and contemporary to the north Atlantic Heinrich 1 (H1) event, with an equilibrium line altitude (ELA) at ca. 5200 m. Our data document also several recession episodes with the youngest one, characterized by an ELA of 5350 m, that seems to correspond to the Younger Dryas (YD) stadial (ca. 12 ka). In the Zongo valley, two recessional moraines have indistinguishable cosmogenic 10Be ages of ca. 17 ka, synchronous with the transgression of the Lake Tauca, with respective ELA of 4760 and 4640 m. Upstream, we identified an intermediate recessional moraine that could either be synchronous with Heinrich 1 or with the Antarctic Cold Reversal episode. Upward along the valley, a Younger Dryas stadial is clearly established by well-clustered cosmogenic 10Be ages, yielding a moraine age of ca. 12 ka, contemporary with the paleolake Coipasa highstand, with an ELA of 5000 m. These results confirm the sensitivity of South Hemisphere tropical glaciers to North Atlantic climate events, such as H1 or the YD. These

Quantifying the distribution of nanodiamonds in pre-Younger Dryas to recent age deposits along Bull Creek, Oklahoma Panhandle, USA

NASA Astrophysics Data System (ADS)

Bement, Leland C.; Madden, Andrew S.; Carter, Brian J.; Simms, Alexander R.; Swindle, Andrew L.; Alexander, Hanna M.; Fine, Scott; Benamara, Mourad

2014-02-01

High levels of nanodiamonds (nds) have been used to support the transformative hypothesis that an extraterrestrial (ET) event (comet explosion) triggered Younger Dryas changes in temperature, flora and fauna assemblages, and human adaptations [Firestone RB, et al. (2007) Proc Natl Acad Sci USA 104(41):16016-16021]. We evaluate this hypothesis by establishing the distribution of nds within the Bull Creek drainage of the Beaver River basin in the Oklahoma panhandle. The earlier report of an abundance spike of nds in the Bull Creek I Younger Dryas boundary soil is confirmed, although no pure cubic diamonds were identified. The lack of hexagonal nds suggests Bull Creek I is not near any impact site. Potential hexagonal nds at Bull Creek were found to be more consistent with graphene/graphane. An additional nd spike is found in deposits of late Holocene through the modern age, indicating nds are not unique to the Younger Dryas boundary. Nd distributions do not correlate with depositional environment, pedogenesis, climate perturbations, periods of surface stability, or cultural activity.

A new Calibrated Deglacial Drainage History for North America and Evidence for an Arctic Trigger for the Younger Dryas

NASA Astrophysics Data System (ADS)

Tarasov, L.; Peltier, W. R.

2004-05-01

We present a new deglacial drainage history for the North American ice complex using the 3D University of Toronto glacial systems model calibrated against a large set of RSL and geodetic data. During melt-water pulse 1a, large order 0.15 to 0.2 Sverdrup century-scale melt-water discharges into both the Gulf of Mexico and western Atlantic occur. During this period, it has generally been inferred that strong thermohaline overturning circulation (TOC) was maintained. As such, our results suggest that the TOC is relatively insensitive to injection of melt-water into the Western Atlantic. In contrast with past inferences, we find the periods of strongest combined melt-water and ice calving discharge (with peak flows of order 0.2 Sverdrups over a century) into the NW Arctic to be during both the onset of and within the Younger Dryas. Model results also show no significant freshwater flux into the Western Atlantic during the Younger Dryas onset period. Given that the Greenland-Iceland-Norwegian (GIN) seas basin was the only outlet route for Arctic waters at this time, we infer that some combination of reduced Canadian Basin sea surface salinities in combination with enhanced sea-ice export into the GIN seas basin played a critical role in triggering and sustaining the altered TOC that is believed to be responsible for the Younger Dryas cold interval. We also speculate that the prior lack of such large discharges into the Canadian Arctic Basin may explain the apparent uniqueness of the Younger Dryas interval.

Bayesian chronological analyses consistent with synchronous age of 12,835–12,735 Cal B.P. for Younger Dryas boundary on four continents

PubMed Central

Kennett, James P.; Kennett, Douglas J.; Culleton, Brendan J.; Aura Tortosa, J. Emili; Bischoff, James L.; Bunch, Ted E.; Daniel, I. Randolph; Erlandson, Jon M.; Ferraro, David; Firestone, Richard B.; Goodyear, Albert C.; Israde-Alcántara, Isabel; Johnson, John R.; Jordá Pardo, Jesús F.; Kimbel, David R.; LeCompte, Malcolm A.; Lopinot, Neal H.; Mahaney, William C.; Moore, Andrew M. T.; Moore, Christopher R.; Ray, Jack H.; Stafford, Thomas W.; Tankersley, Kenneth Barnett; Wittke, James H.; Wolbach, Wendy S.; West, Allen

2015-01-01

The Younger Dryas impact hypothesis posits that a cosmic impact across much of the Northern Hemisphere deposited the Younger Dryas boundary (YDB) layer, containing peak abundances in a variable assemblage of proxies, including magnetic and glassy impact-related spherules, high-temperature minerals and melt glass, nanodiamonds, carbon spherules, aciniform carbon, platinum, and osmium. Bayesian chronological modeling was applied to 354 dates from 23 stratigraphic sections in 12 countries on four continents to establish a modeled YDB age range for this event of 12,835–12,735 Cal B.P. at 95% probability. This range overlaps that of a peak in extraterrestrial platinum in the Greenland Ice Sheet and of the earliest age of the Younger Dryas climate episode in six proxy records, suggesting a causal connection between the YDB impact event and the Younger Dryas. Two statistical tests indicate that both modeled and unmodeled ages in the 30 records are consistent with synchronous deposition of the YDB layer within the limits of dating uncertainty (∼100 y). The widespread distribution of the YDB layer suggests that it may serve as a datum layer. PMID:26216981

Tree-ring records of near-Younger Dryas time in central North America - Preliminary results from the Lincoln quarry site, central Illinois, USA

USGS Publications Warehouse

Panyushkina, Irina P.; Leavitt, Steven W.; Wiedenhoeft, A.; Noggle, S.; Curry, B.; Grimm, E.

2004-01-01

The abrupt millennial-scale changes associated with the Younger Dryas (YD) event ("chronozone") near the dawn of the Holocene are at least hemispheric, if not global, in extent. Evidence for the YD cold excursion is abundant in Europe but fairly meager in central North America. We are engaged in an investigation of high-resolution environmental changes in mid-North America over several millennia (about 10,000 to 14,000 BP) during the Late Glacial-Early Holocene transition, including the YD interval. Several sites containing logs or stumps have been identified and we are in the process of initial sampling or re-sampling them for this project. Here, we report on a site in central Illinois containing a deposit of logs initially thought to be of YD age preserved in alluvial sands. The assemblage of wood represents hardwood (angiosperm) trees, and the ring-width characteristics are favorable to developing formal tree-ring chronologies. However, 4 new radiocarbon dates indicate deposition of wood may have taken place over at least 8000 14C yr (6000-14,000 BP). This complicates the effort to develop a single floating chronology of several hundred years at this site, but it may provide wood from a restricted region over a long period of time from which to develop a sequence of floating chronologies, the timing of deposition and preservation of which could be related to paleoclimatic events and conditions.

Climate variability at the onset of the Younger Dryas as reflected in annually resolved tree-ring stable isotope chronologies

NASA Astrophysics Data System (ADS)

Pieper, H.; Helle, G.; Brauer, A.; Kaiser, K. F.; Miramont, C.

2013-12-01

The Younger Dryas interval during the Last Glacial Termination was an abrupt return to glacial-like conditions punctuating the transition to a warmer, interglacial climate. Despite recent advances in the layer counting of ice-core records of the termination, the timing and length of the Younger Dryas remain controversial. Late Glacial and early Holocene tree-ring chronologies are rare, however, they contain valuable information about past environmental conditions at annual time resolution. Changes in tree-ring growth rates can be related to past climate anomalies and changes in the carbon and oxygen isotope composition of tree-ring cellulose reflect atmospheric and hydrospheric changes. We are investigating a 860-year (13200 - 12340 cal BP) dated dendrochronological record of Late Glacial and Early Holocene chronologies of scots pine (Pinus sylvestris L.) from subfossil tree remnants from Barbiers River (Moyenne Durance, Southern French Alps), as well as from Swiss (Dättnau, Landikon and Gänziloh) sites. Dendro-ecological parameters, such as ring width and stable isotope variations (δ 13C und δ 18O) are used to infer past environmental conditions. We will present our first carbon and oxygen isotope records from tree rings reflecting the environmental changes at the Alleröd/Younger Dryas -transition.

Abrupt release of terrigenous organic carbon to the Laptev Sea at termination of the Younger Dryas

NASA Astrophysics Data System (ADS)

Tesi, T.; Muschitiello, F.; Smittenberg, R.; Jakobsson, M.; Vonk, J.; Hill, P.; Dudarev, O.; Semiletov, I. P.; Kirchner, N.; Noormets, R.; Andersson, A.; Gustafsson, O.

2015-12-01

Based on analysis of a piston core collected in 2014 from the Lena River paleo delta, now Laptev Sea, we show that rapid and massive organic carbon (OC) deposition took place into the marine system at the termination of the Younger Dryas when the Arctic region experienced a large and extremely fast climate change. The highly laminated strata with absence of bioturbation further confirm the rapid event-driven emplacement of this deposit which was largely dominated by terrigenous OC as indicated by depleted δ13C values and high concentrations of terrestrial fossil biomarkers (lignin phenols and cutin-derived products). Moreover, the hydrogen isotopic composition (δ2H) of HMW n-alkanes indicates that this terrestrially-derived translocated OC was produced in the watershed during a relatively cold period. The OC appears to be a few thousand years old at time of deposition (ca. 4-5000 radiocarbon years; reservoir age corrected), consistent with the radiocarbon age of pre-aged OC currently supplied by the Lena river. Altogether our results indicate that fast climate warming exerts first-order control on large-scale carbon redistribution. Because the Younger Dryas-Preboreal transition occurred within a few decades, we infer that the abrupt and large release of terrigenous OC was essentially driven by rapid changes in the permafrost stability (i.e., thermal collapse/thawing) and increase in precipitation over the Siberian watershed. Interestingly, only surface and sub-surface carbon pools (i.e., active layer) were remobilized while deep and old sources (radiocarbon dead) did not seem to have substantially contributed to the total land-to-ocean flux during the Younger Dryas-Preboreal transition.

Warm summers during the Younger Dryas cold reversal.

PubMed

Schenk, Frederik; Väliranta, Minna; Muschitiello, Francesco; Tarasov, Lev; Heikkilä, Maija; Björck, Svante; Brandefelt, Jenny; Johansson, Arne V; Näslund, Jens-Ove; Wohlfarth, Barbara

2018-04-24

The Younger Dryas (YD) cold reversal interrupts the warming climate of the deglaciation with global climatic impacts. The sudden cooling is typically linked to an abrupt slowdown of the Atlantic Meridional Overturning Circulation (AMOC) in response to meltwater discharges from ice sheets. However, inconsistencies regarding the YD-response of European summer temperatures have cast doubt whether the concept provides a sufficient explanation. Here we present results from a high-resolution global climate simulation together with a new July temperature compilation based on plant indicator species and show that European summers remain warm during the YD. Our climate simulation provides robust physical evidence that atmospheric blocking of cold westerly winds over Fennoscandia is a key mechanism counteracting the cooling impact of an AMOC-slowdown during summer. Despite the persistence of short warm summers, the YD is dominated by a shift to a continental climate with extreme winter to spring cooling and short growing seasons.

The response of southern California ecosystems to Younger Dryas-like rapid climate change: Comparison of glacial terminations 1 and 5.

NASA Astrophysics Data System (ADS)

Heusser, L. E.; Hendy, I. L.

2015-12-01

The Younger Dryas is a well-known rapid climatic cooling that interrupted the Marine Isotope Stage (MIS) 1-2 deglacial warming of Termination 1. This cool event has been associated with ice sheet readvance, meridional overturning, circulation changes, and southward movement of the Intertropical Convergence Zone. In Southern California, the Younger Dryas has been associated with cooler SST, low marine productivity, a well-ventilated oxygen minimum zone, and a wetter climate. Similar rapid cooling events have been found at other terminations including Termination 5 at the MIS 11-12 deglaciation (~425 Ka) identified by ice rafting events in the North Atlantic. Here we present new pollen census data from a unique suite of cores taken from the sub-oxic sediments of Santa Barbara Basin (MV0508-15JC, MV0805-20JC, MV0508-33JC, 29JC and 21JC). These short cores, collected on a truncated anticline within SBB, provide the opportunity to examine the response of southern California terrestrial and marine ecosystems to rapid climate change during the MIS 11-12 deglaciation (Termination 5), which is identified by a bioturbated interval within a sequence of laminated sediments. During Termination 1, changes in Southern California precipitation are reflected in pollen- based reconstructions Southern California vegetation. The high precipitation of glacial montane-coniferous assemblages of pine (Pinus) and Juniper (Juniperus/Calocedrus) transitions into interglacial drought, as expresssed by arid oak (Quercus)/chaparral vegetation. The Younger Dryas interrupts the transition as a high-amplitude pulse in pine associated with increased Gramineae (grass). Termination 5 differs, as the high precipitation of glacial montane-coniferous assemblages do not transition into arid oak/chaparral vegetation. However, a Younger Dryas-like rapid climate event was associated with increased pine and grass.

Human Population Decline in North America during the Younger Dryas

NASA Astrophysics Data System (ADS)

Anderson, D. G.; Goodyear, A. C.; Stafford, T. W., Jr.; Kennett, J.; West, A.

2009-12-01

There is ongoing debate about a possible human population decline or contraction at the onset of the Younger Dryas (YD) at 12.9 ka. We used two methods to test whether the YD affected human population levels: (1) frequency analyses of Paleoindian projectile points, and (2) summed probability analyses of radiocarbon (14C) dates. The results suggest that a significant decline or reorganization of human populations occurred at 12.9 ka, continued through the initial centuries of the YD chronozone, then rebounded by the end of the YD. FREQUENCY ANALYSES: This method employed projectile point data from the Paleoindian Database of the Americas (PIDBA, http://pidba.utk.edu). We tallied diagnostic projectile points and obtained larger totals for Clovis points than for immediately post-Clovis points, which share an instrument-assisted fluting technique, typically using pressure or indirect percussion. Gainey, Vail, Debert, Redstone, and Cumberland point-styles utilized this method and are comparable to the Folsom style. For the SE U.S., the ratio of Clovis points (n=1993) to post-Clovis points (n=947) reveals a point decline of 52%. For the Great Plains, a comparison of Clovis and fluted points (n=4020) to Folsom points (n=2527) shows a point decline of 37%, which may translate into a population contraction of similar magnitude. In addition, eight major Clovis lithic quarry sites in the SE U.S. exhibit little to no evidence for immediate post-Clovis occupations, implying a major population decline. SUMMED PROBABILITIES: This method involved calibrating relevant 14C dates and combining the probabilities, after which major peaks and troughs in the trends are assumed to reflect changes in human demographics. Using 14C dates from Buchanan et al. (2008), we analyzed multiple regions, including the Southeast and Great Plains. Contrary to Buchanan et al., we found an abrupt, statistically significant decline at 12.9 ka, followed 200 to 900 years later by a rebound in the number of

Sensitivity of the Younger Dryas climate to changes in orbtial, greenhouse gas, and freshwater forcing in CESM1

NASA Astrophysics Data System (ADS)

Hughlett, T. M.; Winguth, A. M. E.; Rosenbloom, N. A.; He, F.

2016-12-01

The Younger Dryas cooling event ( 12,900 years before present) was the most recent abrupt climate change in the geologic record where climate for the Northern Hemisphere returned to a near-glacial state. The cause of this cooling event is widely controversial, and no consensus has been found as to why the onset of the cooling occurred. Of the several hypotheses proposed, the freshening of the North Atlantic Ocean due to meltwater discharge from the retreating Lake Agassiz and subsequent changes in Atlantic meridional oceanic circulation (AMOC) is the most widely accepted one. In this study, the Community Earth System Model version 1 was used to perform sensitivity experiments to test how the AMOC responds to a freshwater discharge into the Northern Atlantic Ocean over the course of 1,000 years. This study is the first fully coupled, moderate-resolution simulation that implements a 13.1ka ice sheet (ICE-5G) along with Younger Dryas boundary and initial conditions. With the addition of the 13.1ka ice sheet and a 0.3 Sverdrup (Sv) freshwater discharge into the Northern Atlantic Ocean, the AMOC reduces by approximately 20 Sv, coming to a substantially slowed-down state of approximately 5 Sv. This reduction of the AMOC causes a decrease in surface air temperature of approximately 15 °C, which is in agreement with surface air temperature reconstructions from the Greenland Ice Sheet Project 2. Overall, the simulation presented in this study accurately represents the climatic state of the Younger Dryas cooling event.

Nanodiamonds do not provide unique evidence for a Younger Dryas impact

PubMed Central

Tian, H.; Schryvers, D.; Claeys, Ph.

2011-01-01

Microstructural, δ13C isotope and C/N ratio investigations were conducted on excavated material from the black Younger Dryas boundary in Lommel, Belgium, aiming for a characterisation of the carbon content and structures. Cubic diamond nanoparticles are found in large numbers. The larger ones with diameters around or above 10 nm often exhibit single or multiple twins. The smaller ones around 5 nm in diameter are mostly defect-free. Also larger flake-like particles, around 100 nm in lateral dimension, with a cubic diamond structure are observed as well as large carbon onion structures. The combination of these characteristics does not yield unique evidence for an exogenic impact related to the investigated layer. PMID:21173270

Post-Clovis survival of American Mastodon in the southern Great Lakes Region of North America

USGS Publications Warehouse

Woodman, N.; Beavan, Athfield N.

2009-01-01

The end of the Pleistocene in North America was marked by a wave of extinctions of large mammals, with the last known appearances of many species falling between ca. 11,000-10,000??14C yr BP. Temporally, this period overlaps with the Clovis Paleoindian cultural complex (11,190-10,530??14C yr BP) and with sudden climatic changes that define the beginning of the Younger Dryas chronozone (ca. 11,000-10,000??14C yr BP), both of which have been considered as potential proximal causes of this extinction event. Radiocarbon dating of enamel and filtered bone collagen from an extinct American Mastodon (Mammut americanum) from northern Indiana, USA, by accelerator mass spectrometer yielded direct dates of 10,055 ?? 40??14C yr BP and 10,032 ?? 40??14C yr BP, indicating that the animal survived beyond the Clovis time period and into the late Younger Dryas. Although the late survival of this species in mid-continental North America does not remove either humans or climatic change as contributing causes for the late Pleistocene extinctions, neither Clovis hunters nor the climatic perturbations initiating the Younger Dryas chronozone were immediately responsible for driving mastodons to extinction. ?? 2009 University of Washington.

Post-Clovis survival of American Mastodon in the southern Great Lakes Region of North America

NASA Astrophysics Data System (ADS)

Woodman, Neal; Beavan Athfield, Nancy

2009-11-01

The end of the Pleistocene in North America was marked by a wave of extinctions of large mammals, with the last known appearances of many species falling between ca. 11,000-10,000 14C yr BP. Temporally, this period overlaps with the Clovis Paleoindian cultural complex (11,190-10,530 14C yr BP) and with sudden climatic changes that define the beginning of the Younger Dryas chronozone (ca. 11,000-10,000 14C yr BP), both of which have been considered as potential proximal causes of this extinction event. Radiocarbon dating of enamel and filtered bone collagen from an extinct American Mastodon ( Mammut americanum) from northern Indiana, USA, by accelerator mass spectrometer yielded direct dates of 10,055 ± 40 14C yr BP and 10,032 ± 40 14C yr BP, indicating that the animal survived beyond the Clovis time period and into the late Younger Dryas. Although the late survival of this species in mid-continental North America does not remove either humans or climatic change as contributing causes for the late Pleistocene extinctions, neither Clovis hunters nor the climatic perturbations initiating the Younger Dryas chronozone were immediately responsible for driving mastodons to extinction.

Younger Dryas cooling and the Greenland climate response to CO2.

PubMed

Liu, Zhengyu; Carlson, Anders E; He, Feng; Brady, Esther C; Otto-Bliesner, Bette L; Briegleb, Bruce P; Wehrenberg, Mark; Clark, Peter U; Wu, Shu; Cheng, Jun; Zhang, Jiaxu; Noone, David; Zhu, Jiang

2012-07-10

Greenland ice-core δ(18)O-temperature reconstructions suggest a dramatic cooling during the Younger Dryas (YD; 12.9-11.7 ka), with temperatures being as cold as the earlier Oldest Dryas (OD; 18.0-14.6 ka) despite an approximately 50 ppm rise in atmospheric CO(2). Such YD cooling implies a muted Greenland climate response to atmospheric CO(2), contrary to physical predictions of an enhanced high-latitude response to future increases in CO(2). Here we show that North Atlantic sea surface temperature reconstructions as well as transient climate model simulations suggest that the YD over Greenland should be substantially warmer than the OD by approximately 5 °C in response to increased atmospheric CO(2). Additional experiments with an isotope-enabled model suggest that the apparent YD temperature reconstruction derived from the ice-core δ(18)O record is likely an artifact of an altered temperature-δ(18)O relationship due to changing deglacial atmospheric circulation. Our results thus suggest that Greenland climate was warmer during the YD relative to the OD in response to rising atmospheric CO(2), consistent with sea surface temperature reconstructions and physical predictions, and has a sensitivity approximately twice that found in climate models for current climate due to an enhanced albedo feedback during the last deglaciation.

North Atlantic Storm Activity During the Younger Dryas

NASA Astrophysics Data System (ADS)

Toomey, M.

2015-12-01

The risks posed to cities along the Eastern Seaboard by a potential intensification of tropical cyclone activity over the coming decades remain poorly constrained, in part, due to a lack of available storm proxy records that extend beyond the relatively stable climates of the late Holocene. Previous work in the Bahamas shows that coarse-grained, high-energy event layers in carbonate bank margin sediments: (1) closely track recent historic hurricane events and (2) that the sensitivity of this proxy may be less affected by the deglacial changes in sea level that have limited our ability to reconstruct past hurricane activity using overwash records from back-barrier beach settings. Here we present a record of storm triggered turbidite deposition from a suite of well dated (e.g. Lynch-Stieglitz et al., 2011, Paleoceanography) jumbo piston cores taken offbank (300-500 mbsl) the Dry Tortugas, Florida, that spans abrupt transitions in North Atlantic sea surface temperature and thermohaline circulation during the Younger Dryas (12.9 - 11.5 kyr BP). This record, along with General Circulation Model output (TraCE: NCAR-CGD), indicates strong hurricane activity may have occurred along Southeastern US coasts through this interval despite considerably colder North Atlantic SSTs.

Precipitation variability in East Timor during Younger Dryas

NASA Astrophysics Data System (ADS)

Chen, J.; Shen, C.; Mii, H.; Sone, T.; Lin, Y.; Chen, Y.

2012-12-01

Here we present a δ18O record of stalagmite collected from Lekiraka cave, East Timor ( 8o47'10.8"S, 126o23'31.1"E; 626 m above sea level). This stalagmite stable oxygen isotope record, covering an age interval of 13.5-10.8 thousand years ago (ka, before 1950 AD) by an age model using 230Th dates. Featured with an increasing precipitation trend during Younger Dryas (YD), this record is similar to the Gunung Buda cave record in Borneo(Partin et al., Nature, 2007, 449, 452-455) and Liang Luar cave record from Flores(Griffiths et al., Nature Geosciences, 2009, 2, 636-639). However, the detailed YD precipitation variability in Lekiraka record is not completely consistent with that in the nearby Liang Luar record with a precipitation maximum at ~12.4 ka. We propose the intensified precipitation in YD period was attributed to an enhanced Australian-Indonesian summer monsoon and was responded to sea level rise and a southward shift of Intertropical Convergence Zone (ITCZ), which was driven by oceanic/atmospheric circulation change originally from the North Atlantic at the YD.

Spatial variability and trends in Younger Dryas equilibrium line altitudes across the European Alps using a hypsometrically based ELA model: results and implications

NASA Astrophysics Data System (ADS)

Keeler, D. G.; Rupper, S.; Schaefer, J. M.; Finkel, R. C.; Maurer, J. M.

2016-12-01

Alpine glaciers constitute an important component of terrestrial paleoclimate records due to, among other characteristics, their high sensitivity to climate change, near global extent, and their integration of myriad climate variables into a single, easily detected signal. Because the glacier equilibrium line altitude (ELA) provides a more explicit representation of climate than many other glacier properties, ELA methods allow for more direct comparisons of multiple glaciers within or between regions. Such comparisons allow for more complete investigations of the ultimate causes of mountain glaciation during specific events. Many studies however tend to focus on a limited number of sites, and employ a large variety of different techniques for ELA reconstruction between studies, making wider climate implications more tenuous. Methods of ELA reconstruction that can be rapidly and consistently applied to an arbitrary number of paleo-glaciers would provide a more accurate portrayal of the changes in climate across a given region. Here we present ELA reconstructions from Egesen Stadial moraines across the European Alps using an ELA model accounting for differences in glacier width, glacier shape, bed topography, ice thickness, and glacier length, including several glaciers constrained to the Younger Dryas using surface exposure dating techniques. We compare reconstructed Younger Dryas ELA values to modern ELA values using the same model, or using end of summer snowline estimates where no glacier is currently present. We further provide uncertainty estimates on the ΔELA using bootstrapped Monte Carlo simulations for the various input parameters. Preliminary results compare favorably to previous glacier studies of the European Younger Dryas, but provide greater context from many glaciers across the region as a whole. Such results allow for a more thorough investigation of the spatial variability and trends in climate during the Younger Dryas across the European Alps, and

The remnants of Younger Dryas lithalsas on the Hautes Fagnes Plateau in Belgium and elsewhere in the world

NASA Astrophysics Data System (ADS)

Pissart, Albert

2003-05-01

This paper summarizes all the available information about the "viviers" of the Hautes Fagnes, i.e., closed and ramparted depressions which are numerous above 500 m a.s.l. on the highest Belgian plateau. These features and cross-sections in the ramparts are described. The ramparts are the result of both mass wasting on the slopes of the mounds and toppling of inside material. 14C dating of a peat layer preserved under a rampart, Alleröd volcanic ashes and palynological studies have proved that the "viviers" formed their origin during the Younger Dryas. In the first place, the depressions were interpreted as excavations by prehistoric men; from 1956 on, they were interpreted as pingo remnants. The pingo hypothesis is now abandoned. The "viviers" are remnants of mineral palsas (lithalsas), features which nowadays exist in Hudsony (Canada). Present-day lithalsas are solely known in subarctic Quebec and in Lapland. They form in the discontinuous permafrost zone, close to the tree line, i.e., in zones where mean annual temperature (MAT) ranges from -4 to -6 °C and where the average temperature of the warmest month is between +9 and +11.5 °C. Such climatic conditions are rarely encountered nowadays in periglacial regions. Remnants of lithalsas are very infrequent, too. They appear like ramparted depressions forming clusters. Such traces, dating from the Younger Dryas, have been described only at elevation above 500 m a.s.l. on the Belgian Hautes Fagnes Plateau, around 250 m a.s.l. in Wales and at sea level in Ireland. In these few places, according to R. Isarin's palaeoclimatic results, climatic conditions during the Younger Dryas were similar to present-day conditions in subarctic Quebec, where lithalsas are numerous.

Origin and provenance of spherules and magnetic grains at the Younger Dryas boundary

PubMed Central

Wu, Yingzhe; Sharma, Mukul; LeCompte, Malcolm A.; Demitroff, Mark N.; Landis, Joshua D.

2013-01-01

One or more bolide impacts are hypothesized to have triggered the Younger Dryas cooling at ∼12.9 ka. In support of this hypothesis, varying peak abundances of magnetic grains with iridium and magnetic microspherules have been reported at the Younger Dryas boundary (YDB). We show that bulk sediment and/or magnetic grains/microspherules collected from the YDB sites in Arizona, Michigan, New Mexico, New Jersey, and Ohio have 187Os/188Os ratios ≥1.0, similar to average upper continental crust (= 1.3), indicating a terrestrial origin of osmium (Os) in these samples. In contrast, bulk sediments from YDB sites in Belgium and Pennsylvania exhibit 187Os/188Os ratios <<1.0 and at face value suggest mixing with extraterrestrial Os with 187Os/188Os of ∼0.13. However, the Os concentration in bulk sample and magnetic grains from Belgium is 2.8 pg/g and 15 pg/g, respectively, much lower than that in average upper continental crust (=31 pg/g), indicating no meteoritic contribution. The YDB site in Pennsylvania is remarkable in yielding 2- to 5-mm diameter spherules containing minerals such as suessite (Fe-Ni silicide) that form at temperatures in excess of 2000 °C. Gross texture, mineralogy, and age of the spherules appear consistent with their formation as ejecta from an impact 12.9 ka ago. The 187Os/188Os ratios of the spherules and their leachates are often low, but Os in these objects is likely terrestrially derived. The rare earth element patterns and Sr and Nd isotopes of the spherules indicate that their source lies in 1.5-Ga Quebecia terrain in the Grenville Province of northeastern North America. PMID:24009337

Carbon isotopes from fossil packrat pellets and elevational movements of Utah agave plants reveal the Younger Dryas cold period in Grand Canyon, Arizona

USGS Publications Warehouse

Cole, K.L.; Arundel, S.T.

2005-01-01

Carbon isotopes in rodent fecal pellets were measured on packrat (Neotoma spp.) middens from the Grand Canyon, Arizona. The pellet samples reflect the abundance of cold-intolerant C4 and Crassulacean acid metabolism (CAM) plant species relative to the predominant C3 vegetation in the packrat diet. The temporal sequence of isotopic results suggests a temperature decline followed by a sharp increase corresponding to the B??lling/Aller??d-Younger Dryas - early Holocene sequence. This pattern was then tested using the past distribution of Utah agave (Agave utahensis). Spatial analyses of the range of this temperature-sensitive CAM species demonstrate that its upper elevational limit is controlled by winter minimum temperature. Applying this paleotemperature proxy to the past elevational limits of Utah agave suggests that minimum winter temperatures were ???8??C below modern values during the Last Glacial Maximum, 4.5-6.5 ??C below modern during the B??lling/Aller??d, and 7.5-8.7 ??C below modern during the early Younger Dryas. As the Younger Dryas terminated, temperatures warmed ???4 ??C between ca. 11.8 ka and 11.5 ka. These extreme fluctuations in winter minimum temperature have not been generally accepted for terrestrial paleoecological records from the arid southwestern United States, likely because of large statistical uncertainties of older radiocarbon results and reliance on proxies for summer temperatures, which were less affected. ?? 2005 Geological Society of America.

An Arctic Ocean freshwater event as the trigger of the Younger Dryas stadial? Answers from Arctic deep-sea sediment cores

NASA Astrophysics Data System (ADS)

Spielhagen, Robert F.

2017-04-01

At ca. 12.8-11.5 ka the northern hemisphere climate experienced a dramatic fall-back to quasi-glacial conditions. Since the late 1980s, a major meltwater ejection to the North Atlantic through the Gulf of St.Lawrence was considered the most likely trigger for this "Younger Dryas event". It may have caused a slowdown of the Atlantic meridional overturning circulation (AMOC) and a diminished heat transport to the northern latitudes. However, field evidence from the potential meltwater route in North America has been discussed controversially in the last years, and the detection of a freshwater signal in marine sediments off the St.Lawrence river rendered difficult. More recently, the idea of an "Arctic route" of meltwater originating from proglacial lake Agassiz was put forward (Tarasov & Peltier, Nature 2005) and has gained further attraction through evidence from radiogenic isotopes (Not and Hillaire-Marcel; Nature Comm., 2012) and through modelling results of Condron and Winsor (PNAS, 2012) which showed that only a freshwater outflow through Fram Strait was capable of triggering a climate perturbation like the Younger Dryas. Here I present a review of isotopic records from the Arctic Ocean, the Fram Strait, and the Greenland Sea in search of evidence for a strong freshwater event in the Arctic Ocean at the onset of the Younger Dryas, supporting an Arctic origin of the trigger. A number of Arctic cores show a light planktic oxygen isotope spike at 13 ka. For several of them the age model is detailed enough to exclude a confusion with other deglacial spikes. On the central Arctic Lomonosov Ridge there is even evidence for a diminshed intermediate/bottom water circulation immediately following the freshwater event. On the other hand, there are many records which do not show a meltwater spike in the critical time interval, most likely because of low temporal resolution, a thick ice cover and/or a habitat change of the planktic foraminifers. The largest uncertainty is

The impact of climate and environmental processes on vegetation pattern in the Czechowskie lake catchment Czechowo Region (Northern Tuchola Pinewoods) during the Younger Dryas cooling

NASA Astrophysics Data System (ADS)

Noryśkiewicz, Agnieszka Maria; Kramkowski, Mateusz; Słowiński, Michał; Zawiska, Izabela; Lutyńska, Monika; Błaszkiewicz, Mirosław; Brauer, Achim

2014-05-01

Czechowskie lake is located in the northern part of the Tuchola Pinewoods District (Northern Poland) in a young glacial landscape. At present, the majority of the area is forested or used for agricultural purposes, but among them a high amount of basins filled with biogenic sediments are present. This area is very suitable for the postglacial vegetation development investigation because of the LST ash and laminated sediments which we found in the Trzechowskie palaeolake and Czechowskie Lake (Wulf et. all 2013). The aim of the research was to reconstruct the past landscape and vegetation response to Younger Dryas cooling and we present the results of the palinological analysis done for 6 core of biogenic sediments. Our main objective was to determine whether local factors such as topography and soil cover have a significant impact on the vegetation, eutrophy and sedimentation rate at this time. In the lake Czechowskie lake catchment we have six cores that cover postglacial succession (Lake Czechowskie small basin - profile JC-12-s; Lake Czechowskiego terrace - profile TK; Lake Czechowskie vicinity - profile "Oko and Cz/80; Trzechowskie paleolake - profile T/trz; Valley between paleolake Trzechowskie and Lake Czechowskie - profile DTCZ-4). The paleoecological research carried out involved an analysis of pollen, macrofossils, Cladocera, diatom, loss-on-ignition and CaCO3 content. The results show, that the dominant plant communities during the Youngers Dryas in the region nearby Lake Czechowskie are heliophytes xeric herb vegetation with juniper (Juniperus communis) shrubs and birch (Betula) and pine (Pinus sylvestris). In the pollen diagrams there was the difference noted in the participation of the dominant pollen, the juniper pollen was always high but varied from 18 to 37%, birch average pollen share was between 17-27%. The thickness and type of the sediment accumulated in Younger Dryas in the presented profiles differs significantly. In the profiles which

Younger Dryas equilibrium line altitudes and precipitation patterns in the Alps

NASA Astrophysics Data System (ADS)

Kerschner, Hanns; Moran, Andrew; Ivy-Ochs, Susan

2016-04-01

Moraine systems of the "Egesen Stadial" are widespread and easily identifiable features in the Alps. Absolute dating with terrestrial cosmogenic radionuclides shows that the maximum extent was reached during the early Younger Dryas (YD), probably as a reaction to the intense climatic downturn subsequent to Lateglacial Interstadial. In recent years, several new studies and the availability of high-quality laser-scan hillshades and orthophotos allowed a significant extension of the database of YD glaciers as "palaeoprecipitation gauges" to large hitherto unmapped regions in the Austrian and Swiss Alps. The equilibrium line altitude (ELA) of the glaciers and its lowering relative to the Little Ice Age ELA (dELA) shows a distinct and systematic spatial pattern. Along the northern slope of the Alps, dELAs are usually large (around 400 m and perhaps even more), while dELAs range around 200 m in the well sheltered areas of the central Alps, e.g. in the Engadine and in western Tyrol. Both stochastic glacier-climate models (e.g. Ohmura et al. 1992) and the heat- and mass balance equation (Kuhn 1981) allow the reconstruction of precipitation change under the assumption of a spatially constant summer temperature depression, which in turn can be estimated from biological proxies. This allows to draw the spatial pattern of precipitation change with considerable detail. Precipitation change is clearly controlled by the local relief like high mountain chains, deeply incised and long valleys and mountain passes. Generally the contrast between the northern fringe of the Alps and the interior was more pronounced than today. Climate in the Northern and and Northwestern Alps was rather wet with precipitation totals eventually exceeding modern annual sums. The central Alps received 20 - 30% less precipitation than today, mainly due to reduced winter precipitation. In the southern Alps, still scarce spatial information points to precipitation sums which were approximately similar to

Atmospheric dynamics over Europe during the Younger Dryas revealed by palaeoglaciers.

NASA Astrophysics Data System (ADS)

Rea, Brice; Pellitero, Ramon; Spagnolo, Matteo; Hughes, Philip; Braithwaite, Roger; Renssen, Hans; Ivy-Ochs, Susan; Ribolini, Adriano; Bakke, Jostein; Lukas, Sven

2017-04-01

A dataset of 120 palaeoglaciers ranging from Morocco in the south to Svalbard in the north and from Ireland in the west to Turkey in the east, has been assembled from the literature. A robust quality control on the chronology was undertaken and, when derived from cosmogenic nuclides, ages were recalculated using the most up-to-date production rates. All the reconstructed glaciers date to the Younger Dryas. Frontal moraines/limits were used to initiate the palaeoglacier reconstructions using GlaRe, a GIS tool which generates an equilibrium profile ice surface along a single flowline and extrapolates this to out to a 3D ice surface. From the resulting glacier surfaces palaeo-ELAs were calculated within the GIS. Where multiple glaciers were reconstructed within in a region, a single ELA value was generated. Results show that ELAs decrease with latitude but have a more complex pattern with longitude. A database of 121 sites, spanning the same geographical range as the palaeoglaciers, was compiled for Younger Dryas temperature, determined from palaeoproxies, for example pollen, diatoms, coleoptera, chironimids etc. These proxy data were merged and interpolated to generate maps of average temperature for the warmest and coldest months and annual average temperature. Results show that, in general, temperature decreases with latitude. Temperature at the palaeo-ELAs were determined from the temperature maps using a lapse rate of 0.65°C/100m and the precipitation required for equilibrium was calculated. Positive precipitation anomalies are found along much of the western seaboard of Europe, with the most striking positive anomalies present in the eastern Mediterranean. Negative precipitation anomalies appear on the northern side of the Alps. This pattern is interpreted to represent a southward displaced polar frontal jet stream with a concomitant track of Atlantic mid-latitude depressions, leading to more frequent incursions of low pressure systems especially over the

A new concept for paleohydrological evolution of the Younger Dryas in NE Brazil

NASA Astrophysics Data System (ADS)

Bouimetarhan, Ilham; Prange, Matthias; Gonzalez, Catalina; Dupont, Lydie

2016-04-01

The late deglacial interval from approximately 13 to 11 kyr BP contains some of the best documented abrupt climate changes in the Past, the Younger Dryas (YD). It is also an interval when the bipolar climatic signature of millennial-scale changes in the Atlantic meridional overturning circulation (AMOC) is well expressed. Here we present a high-resolution palynological record from core GeoB16205-4 (1°21.11'N, 43°05.80'W), retrieved off the Parnaíba River mouth, southeast of the Amazon River (~1955 m water depth). Pollen and organic-walled dinoflagellate cyst assemblages indicate a predominantly wet climate during the YD in the nowadays semi-arid Nordeste, whereby a second phase between ~12.3 and 11.7 kyr BP is wetter than the period before. This is recorded by a strong increase in the concentrations of river plume dinoflagellate cyst assemblages indicative of a stratified surface water column and reduced salinity environments, as well as a drop in grass pollen and microcharcoal particle concentrations along with strong fluctuations in the representation of rain forest, gallery forest and tree ferns suggesting year-round humid conditions. This shift from a relatively wet first phase to a much wetter second phase is in agreement with the transient TRACE-21k coupled climate model simulation which shows a first pluvial Parnaíba stage from ~12.8 to 12.3 kyr BP and a second stronger pluvial stage between ~12.3 and 11.7 kyr BP to be related to a very weak AMOC due to meltwater pulses in the North Atlantic. The AMOC variation induces a steep temperature gradient between the Southern and the Northern Hemisphere which forces a southward shift of the Intertropical Convergence Zone (ITCZ) and its associated rainfall. The two-step hydroclimatic and environmental evolution during the Younger Dryas has not been documented previously in this region.

Exploring the Human Ecology of the Younger Dryas Extraterrestrial Impact Event

NASA Astrophysics Data System (ADS)

Kennett, D. J.; Erlandson, J. M.; Braje, T. J.; Culleton, B. J.

2007-05-01

Several lines of evidence now exist for a major extraterrestrial impact event in North America at 12.9 ka (the YDB). This impact partially destabilized the Laurentide and Cordilleran ice sheets, triggered abrupt Younger Dryas cooling and extensive wildfires, and contributed to megafaunal extinction. This event also occurred soon after the well established colonization of the Americas by anatomically modern humans. Confirmation of this event would represent the first near-time extraterrestrial impact with significant effects on human populations. These likely included widespread, abrupt human mortality, population displacement, migration into less effected or newly established habitats, loss of cultural traditions, and resource diversification in the face of the massive megafaunal extinction and population reductions in surviving animal populations. Ultimately, these transformations established the context for the special character of plant and animal domestication and the emergence of agricultural economies in North America. We explore the Late Pleistocene archaeological record in North America within the context of documented major biotic changes associated with the YDB in North America and of the massive ecological affects hypothesized for this event.

Positive anomaly in platinum group elements and the presence of shocked diamonds: Two question marks at the Younger Dryas

NASA Astrophysics Data System (ADS)

Claeys, P. F.; Schryvers, D.; Tian, H.; Goderis, S.

2009-12-01

Recently, a large size impact was proposed as the cause of the global changes taking place at the Younger Dryas (YD) some 12,9 kyr ago. Impact evidence was reported in a C-rich black layer of broad geographic distribution. The impact markers consist of a large anomaly in the concentration of platinum group elements (PGE) and the presence of nanodiamonds, in particular lonsdaleite, which hexagonal structure is believed to be of shock origin. The impact is proposed to have occurred on the North American continent. A crater large enough (> 150 km) to induce a mass extinction some ~12.9 ka ago, formed in a geologically well-known area, is unlikely to have escaped detection. Therefore, an alternative hypothesis is that a cometary projectile exploded fully within the atmosphere spreading PGE and shock formed diamonds, without any target rock contribution, all around the Northern hemisphere. So far, PGE measurements failed to reproduce the elevated (> ppb) concentrations reported previously at Younger Dryas sites containing the black layer. In Lommel (Belgium) where the first study detected up to 117 ppb Ir, the Ir concentration is below the detection limit of the method (NiS fire assay + ICP-MS) used (0.06 ppb). At all sites analyzed the PGE pattern is typical of that of the continental crust. In several craters (Popigai, Ries) or at the KT boundary nanodiamonds have been reported associated with shocked materials. Several types of carbon components occur in the black layer of the Lommel section such as i) flakes reaching up to 1 µm, ii) nano particles of cubic diamond, 1 to 10 nm in size and iii) larger carbon onion-ring structures, which core can act as a nanoscopic pressure cell leading to the formation of nanodiamond by self- compression. The Lommel nanodiamonds present in the Younger Dryas layer do resemble nanodiamonds found in carbon spherules of unknown origin previously reported in top soil from several localities in Belgium and Germany. The C stable isotopic

Environmental Change recorded in Lacustrine Sediments from Tangra Yumco, Tibetan Plateau, at 16.5 ka cal BP and during the Younger Dryas Chronozone

NASA Astrophysics Data System (ADS)

Henkel, K.; Ahlborn, M.; Haberzettl, T.; Kasper, T.; Daut, G.; Ju, J.; Ma, Q.; Wang, J.; Zhu, L.; Maeusbacher, R.

2013-12-01

higher in the older part and changes around ~16,500 cal BP to a lower, constant one. At the same time, shifts in the Ti, K, Rb and Sr values can be observed, pointing to a hydrological change in the system. Regarding Ca and Sr values, a change in the authigenic carbonate production, reflecting a climatic change, coinciding with the timing of the Younger Dryas could be observed. This new record represents a promising archive for paleomonsoonal reconstruction on the TP with a high potential for a broad multi-proxy approach. Further analyses with different independent dating methods (i.e., U/Th, compound specific radiocarbon dating, OSL, magnetostratigraphy) as well as sedimentological (grain size, thin sections), geochemical (CNS, organic geochemistry, isotopes) and micropalaeontological (ostracods) parameters are in progress.

A temperature reversal within the rapid Younger Dryas-Holocene warming in the North Atlantic?

NASA Astrophysics Data System (ADS)

Vincent, Jessie H.; Cwynar, Les C.

2016-12-01

The onset of the Holocene has been generally considered rapid and uninterrupted in the circum-Atlantic region. Loss-on-ignition (LOI - an index of organic carbon) profiles from 18 lateglacial-aged lakes in Nova Scotia, Canada, together with chironomid-inferred temperature reconstructions at 5 sites, demonstrate that the rapid warming from the Younger Dryas (GS-1) to the Holocene was interrupted by a cooling of 1.6-6.4 °C in summer surface lake water temperature. The resulting inflection or reversal on the rising temperature curve has also been identified at 35 sites outside Nova Scotia from terrestrial and marine settings, indicating that this cool step is a robust feature throughout the North Atlantic and is likely the result of major oceanic and atmospheric reorganization of the Holocene climate system.

Late Pleistocene Megafaunal Extinction Consistent With YDB Impact Hypothesis at Younger Dryas Onset

NASA Astrophysics Data System (ADS)

Kennett, J. P.; Kennett, D. J.

2008-12-01

At least 35 mammal and 19 bird genera became extinct across North America near the end of the Pleistocene. Modern increases in stratigraphic and dating resolution suggest that this extinction occurred relatively rapidly near 12.9 ka (11 radiocarbon kyrs). Within the context of a long-standing debate about its cause, Firestone et al., (2007) proposed that this extinction resulted from an extraterrestrial (ET) impact over North America at 12.9 ka. This hypothesis predicts that the extinction of most of these animals should have occurred abruptly at 12.9 ka. To test this hypothesis, we have critically examined radiocarbon ages and the extinction stratigraphy of these taxa. From a large data pool, we selected only radiocarbon dates with low error margins with a preference for directly dated biological materials (e.g., bone, dung, etc.) and modern chemical purification techniques. A relatively small number of acceptable dates indicate that at least 16 animal genera and several other species became extinct close to 12.9 ka. These taxa include the most common animals of the late Pleistocene such as horses, camels, and mammoths. Also, the remains of extinct taxa are reportedly found up to, but not above, the base of a widely distributed carbon-rich layer called the black mat. This stratum forms an abrupt, major biostratigraphic boundary at the Younger Dryas onset (12.9 ka), which also contains multiple ET markers comprising the impact layer (the YDB). Surviving animal populations were abruptly reduced at the YDB (e.g., Bison), with major range restrictions and apparent evolutionary bottlenecks. The abruptness of this major extinction is inconsistent with the hypotheses of human overkill and climatic change. We argue that extinction ages older than 12.9 ka for many less common species result from the Signor-Lipps effect, but the impact hypothesis predicts that as new dates are acquired, they will approach ever closer to 12.9 ka. The megafaunal extinction is strongly

Severe winter cooling during the Younger Dryas in northern Alaska - evidence from the stable isotope composition of a buried ice-wedge system

NASA Astrophysics Data System (ADS)

Meyer, Hanno; Schirrmeister, Lutz; Yoshikawa, Kenji; Opel, Thomas; Wetterich, Sebastian; Hubberten, Hans-W.; Brown, Jerry

2010-05-01

The Younger Dryas (YD) interval, from approximately 12.9 to 11.5 kyr cal BP, a rapid reversion to glacial climate conditions at the Pleistocene-Holocene transition, has generally been attributed to the release of meltwater from the Laurentide Ice Sheet to the North Atlantic or Arctic oceans. The reaction of the North Pacific region to this "shutdown" of the thermohaline circulation in the North Atlantic during Younger Dryas is, however, little understood. The YD cold interval is of great interest for understanding rapid natural climate change, especially with regard to recent global warming scenarios. Various archives such as glacier ice, tree rings, lacustrine and marine sediments provide evidence for strong climate variability during the Late Glacial-Holocene transition. In our study, we investigated a relict, buried ice-wedge system within the continuous permafrost zone near Barrow, northern Alaska (71°18'N, 156°40'W). The Barrow ice-wedge system is buried under about three meters of Late Glacial/early Holocene ice-rich sediments. The ice wedges are accessible through a shaft which extends into an underground excavation, where a detailed description and sampling with an electrical chain saw were carried out. Permafrost is not only susceptible to recent climate change, it also may store evidence of these changes in ground ice, especially in ice wedges. Ice wedges can be assessed by stable water isotope methods similar to glacier ice climate reconstructions. Ice wedges are assumed to be indicative of winter climate conditions, because the seasonality of thermal contraction cracking and of the infill of frost cracks are generally related to winter and spring, respectively. In this paper, we present a winter climate record from ice wedges in permafrost of northern Alaska, a region, where paleoclimate records extending beyond the Late Glacial-Holocene transition are generally rather sparse, often restricted to lake sediments and rely mostly on summer indicators

The Effect of the Younger Dryas on Paleoindian Occupations in Eastern North America Evidence from Artifactual, Pollen, and Radiocarbon Records

NASA Astrophysics Data System (ADS)

Anderson, D. G.; Meeks, S. C.; Miller, D. S.; Yerka, S. J.; Gillam, J. C.; Goodyear, A. C.; Johanson, E. N.; West, A.

2008-12-01

The Younger Dryas appears to have been a period when human populations in Eastern North America were undergoing significant stress. Attribute and locational data on Paleoindian materials from across the continent is available from the Paleoindian Database of the Americas or PIDBA, available on-line at http://pidba.utk.edu. Tallying the diagnostic projectile point sample from PIDBA in the on-line "entire sample" dated 24 April 2008, suggests that a population decline followed by a rebound may have occurred, particularly in southeastern North America. Following Clovis, fluted points with deeply indented bases and short to full flutes occur in many areas, such as the Redstone, Barnes, Cumberland, and Folsom types. In southeastern North America, these are thought to have been replaced by unfluted lanceolate and waisted forms, including the Beaver Lake, Suwannee/Simpson, and Quad types, which are in turn replaced by Dalton forms. Within the Southeast, a significant decline occurs between Clovis (N=1993 points) and presumably immediate post-Clovis full fluted forms (N=947 points). This may correspond to a similar decline in population, assuming the point types occurred for comparable periods of time, and were used in a similar fashion. Goodyear noted a similar pattern between Clovis (n=179) and presumed immediate post-Clovis Redstone (n=40) forms in South Carolina. Comparable declines have also been observed in North Carolina by Daniel and Goodyear ( and in Virginia by MacAvoy. In the PIDBA database across the Southeast, projectile point numbers increase following the immediate post Clovis decline, from 947 full fluted to 1717 unfluted and then 2594 Dalton points. The increase in the latter part of the Younger Dryas may actually be even more pronounced, since Dalton points, which are quite widespread, are only systematically recorded in a few states. Radiocarbon dates from Paleoindian and Early Archaic assemblages reveal a similar pattern. Dates falling in the initial

Evidence for an Extraterrestrial Impact Event 12,900 years ago that Contributed to Megafaunal Extinctions and the Younger Dryas Cooling

NASA Astrophysics Data System (ADS)

Firestone, R. B.; West, A.; Kennett, J. P.; Becker, L.; Bunch, T. E.; Revay, Z.; Schultz, P. H.; Belgya, T.; Dickenson, O. J.; Erlandson, J. M.; Goodyear, A. C.; Harris, R. S.; Howard, G. A.; Kennett, D. J.; Kloosterman, J. B.; Lechler, P.; Montgomery, J.; Poreda, R.; Darrah, T.; Que Hee, S. S.; Smith, A. R.; Stich, A.; Topping, W.; Wittke, J. H.; Wolbach, W. S.

2007-05-01

The Younger Dryas event boundary (YDB) is a thin sedimentary layer of 12.9 ka age containing an assemblage of materials formed due to a major ET impact centered over northern North America. The event coincided with the megafaunal extinctions and the Younger Dryas cooling episode. The YDB layer contains peaks in magnetic grains, microspherules, and iridium, in addition to charcoal and soot that resulted from extensive wildfires. Two impact-related carbon-rich markers, glass-like carbon and carbon spherules, have not been reported previously in North America. Vesicular, glass-like carbon, in pieces up to several cm, occurs in the YDB at 22 sites with concentrations ranging up to 16 g/kg. Their glassy texture suggests melting during formation, with some fragments grading into charcoal, and CF-IRMS analysis reveals a composition of >70 percent carbon. One sample exhibited a strong fullerene signature containing ET helium with a ratio of 84× that of air, comparable to the Tagish Lake meteorite (90×). Similar glass-like carbon has been reported from the Azuara crater in Spain (Ernstson, et al. 2001). Carbon spherules (0.15-2.5 mm) are black, highly vesicular, low-density, subspherical-to-spherical objects found in 18 widely distributed sites at varying concentrations up to 1500/kg. SEM analysis shows that the spherules have cracked and patterned surfaces, honeycombed cells, no inclusions, and sometimes display hollow cores. SEM/EDS and microprobe analyses show the carbon spherules to be >75 percent carbon. Similar carbon spherules are reported from the a crater in Germany (Rösler, et al., 2005). The carbon spherules most likely are either ablation products from the impactor or combustion products of the impact. Sediment samples were analyzed for Ir, and YDB samples from 9 sites exhibited elevated Ir values up to 3.75 ppb, while there was no detectable Ir above or below the YDB. Extracted magnetic grains have values up to 117 ppb, which is 25 percent that of typical

Heinrich 0 at the Younger Dryas Termination Offshore Newfoundland

NASA Astrophysics Data System (ADS)

Pearce, C.; Andrews, J. T.; Jennings, A. E.; Bouloubassi, I.; Seidenkrantz, M. S.; Kuijpers, A.; Hillaire-Marcel, C.

2014-12-01

The last deglaciation was marked by intervals of rapid climatic fluctuations accompanied by glacial advances and retreats along the eastern edge of the Laurentide ice sheet. The most severe of these events, the Younger Dryas cold reversal, was accompanied by the major detrital carbonate (DC) event generally referred to as "Heinrich event 0" (H0) in the westernmost and southern Labrador Sea. A detrital carbonate layer was observed in a high resolution marine sediment record from southern Newfoundland and the onset of the event was dated to 11,600 ± 70 cal. yrs. BP (local ΔR = 140 yrs.). A variety of different proxies was applied to investigate the transport mechanisms for deposition of the layer and provenance of the carbonates. Elevated concentrations of dolomite and calcite based on quantitative X-ray diffraction measurements, combined with the presence of several mature petrogenic biomarkers limit the source of the H0 detrital input to Palaeozoic carbonate outcrops in north-eastern Canada. The event is attributed to the rapid ice retreat from the Hudson Strait directly following the warming at the onset of the Holocene. Based on additional proxy data published earlier from the same record, the event succeeded the early Holocene resumption of the Atlantic Meridional Overturning Circulation (AMOC), indicating that the Hudson Strait meltwater event had probably no significant impact on the AMOC. The detrital carbonate layer can be found in other marine sediment records along the Labrador Current pathway, from Hudson Strait to the Grand Banks and the southern Newfoundland slope. By using the onset of deposition of the carbonates as a time-synchronous marker, the DC layer has great potential for improving marine chronologies of late glacial age in the region and evaluating spatial variations in ΔR values.

Differential proxy responses to late Allerød and early Younger Dryas climatic change recorded in varved sediments of the Trzechowskie palaeolake in Northern Poland

NASA Astrophysics Data System (ADS)

Słowiński, Michał; Zawiska, Izabela; Ott, Florian; Noryśkiewicz, Agnieszka M.; Plessen, Birgit; Apolinarska, Karina; Rzodkiewicz, Monika; Michczyńska, Danuta J.; Wulf, Sabine; Skubała, Piotr; Kordowski, Jarosław; Błaszkiewicz, Mirosław; Brauer, Achim

2017-02-01

High-resolution biological proxies (pollen, macrofossils, Cladocera and diatoms), geochemical data (μ-XRF element scans, TOC, C/N ratios, δ18Ocarb and δ13Corg values) and a robust chronology based on varve counting, AMS 14C dating and tephrochronology were applied to reconstruct lake system responses to rapid climatic and environmental changes of the Trzechowskie palaeolake (TRZ; Northern Poland) during the late Allerød - Younger Dryas (YD) transition. Palaeoecological and geochemical data at 5-15 years temporal resolution allowed tracing the dynamics of short-term shifts of the ecosystem triggered by abrupt climate change. The robust age control together with the high-resolution sampling allowed the detection of leads and lags between different proxies to the climate shift at the Allerød-Younger Dryas transition. Our results indicate (1) a water level decrease and an increase in wind activities during the late Allerød and the Allerød-YD transition, which caused intensified erosion in the catchment, (2) a two-decades delayed vegetation response in comparison to the lake depositional system. Comparison with the Lake Meerfelder Maar record revealed slightly different vegetation responses of the Trzechowskie palaeolake at the YD onset.

Radiocarbon dating with annual-resolution of subfossil trees from the Younger Dryas event in the southern French Alps

NASA Astrophysics Data System (ADS)

Capano, Manuela; Miramont, Cécile; Guibal, Frédéric; Kromer, Bernd; Tuna, Thibaut; Fagault, Yoann; Bard, Edouard

2017-04-01

Tree rings are an important archive for the calibration of radiocarbon data. The younger part of the IntCal curve is based essentially on tree-ring chronologies, absolutely dated by dendrochronological analysis. For the Northern Hemisphere (NH), a gap still exists between the absolutely dated sequences and a floating chronology. Based on the Southern Hemisphere (SH) tree-ring chronologies a link has been previously proposed (Reimer et al. 2013, Radiocarbon; see also update in Hogg et al. 2016, Radiocarbon). By measuring radiocarbon at annual resolution in French subfossil pines (Pinus sylvestris L.) we propose to improve the connection between the absolute chronology and the floating chronology. Several subfossil pines have been found in the Southern French Alps; they were buried by flood deposits, allowing their preservation. Some trees discovered in the Barbier riverbed were dated to the Younger Dryas periods by previous decadal radiocarbon measurements, performed in Heidelberg and Mannheim. The trees selected for our new study are Barb12 and Barb17 (analyzed sequences of 163 and 152 rings, respectively). These sequences were sampled at annual resolution when permitted by the ring width. As a first step, every third ring was pretreated for radiocarbon analysis. These samples were sliced in small pieces and pretreated by using the ABA-B method before being combusted, graphitized with the AGE system and measured with AixMICADAS (Bard et al. 2015, Nucl. Instr. Meth. B). From the comparison with the kauri sequence, the Barb12-17 sequence can be dated from about 12835 to 12606 cal. BP. It can also be used to calculate the interhemispheric gradient (IHG) over the overlapping period. In order to reduce the inter-annual variability, the Barb12-17 record was smoothed, grouped and averaged over the same decades as in the Kauri record. On the basis of twenty values, a mean IHG value of ca. 60 years was calculated. Quantification of the IHG around 50 yr is particularly

Bay of Bengal Exhibits Warming Trend During the Younger Dryas: Implications of AMOC

NASA Astrophysics Data System (ADS)

Panmei, Champoungam; Divakar Naidu, Pothuri; Mohtadi, Mahyar

2017-12-01

A sharp decline in temperature during the Younger Dryas (YD) preceding the current warmer Holocene is well documented in climate archives from the Northern Hemisphere high latitudes. Although the magnitude of YD cooling varied spatially, the response of YD cooling was well documented in the Atlantic and Pacific Oceans but not in the Indian Ocean. Here we investigate whether the modern remote forcing of tropical Indian Ocean sea surface temperature (SST) by Northern Hemisphere climate changes holds true for events such as the YD. Our SST reconstruction from the western Bay of Bengal exhibits an overall warming of ˜1.8°C during the YD. We further compared our data with other existing Mg/Ca-based SST records from the Northern Indian Ocean and found no significant negative SST anomalies in both the Arabian Sea and the Bay of Bengal compared to pre- and post-YD, suggesting that no apparent cooling occurred during the YD in the Northern Indian Ocean. In contrast, most part of the YD exhibits positive SST anomalies in the Northern Indian Ocean that coincide with the slowdown of the Atlantic Meridional Overturning Circulation during this period.

Meltwater and precipitation runoff to the North Atlantic, Arctic, and Gulf of Mexico from the Laurentide Ice Sheet and adjacent regions during the Younger Dryas

NASA Astrophysics Data System (ADS)

Teller, James T.

1990-12-01

Runoff from North America may have played a significant role in ocean circulation and climate change during the last deglaciation. Because the driving force behind such changes may have been related to salinity of the north flowing Atlantic Ocean conveyor circulation, it is critical to know the volume, timing, and location of fresh water entering the North Atlantic from the melting Laurentide Ice Sheet. During the Younger Dryas cold episode, 11,000-10,000 years B.P., there was a two-fold increase in the volume of meltwater plus precipitation runoff, to more than 1700 km³ yr-1, flowing through the St. Lawrence valley to the North Atlantic, mainly because retreating ice allowed the glacial Lake Agassiz basin to drain eastward into the Great Lakes at this time. There was a corresponding decline in discharge from Lake Agassiz through the Mississippi River to the Gulf of Mexico. Runoff to the Arctic Ocean also increased at about the beginning of the Younger Dryas, from 740 to 900 km³ yr-1, because of the capture of what is now the headwater region of the Mackenzie River watershed. This, in combination with rising sea level and warming climate, may have increased the amount of pack ice reaching the North Atlantic through the Norwegian Sea from the Arctic Ocean. At 10,000 years B.P., eastward overflow from the western interior of North America was blocked by advancing ice, again forcing overflow to the Gulf of Mexico and, possibly, to the northwest into the Arctic Ocean. Although total runoff to the oceans from all regions draining from the Laurentide Ice Sheet did not vary substantially between 12,000 and 9000 years B.P., if discharge to the Gulf of Mexico is excluded, fresh water reaching the North Atlantic averaged 4000 km³ yr-1 during the Younger Dryas, in contrast to 2870 km³ yr-1 just before this cold episode and 3440 km³ yr-1 just after it.

Paradigms and proboscideans in the southern Great Lakes region, USA

USGS Publications Warehouse

Saunders, J.J.; Grimm, E.C.; Widga, C.C.; Campbell, G.D.; Curry, B. Brandon; Grimley, D.A.; Hanson, P.R.; McCullum, J.P.; Oliver, J.S.; Treworgy, J.D.

2010-01-01

Thirteen new chronometric dates for Illinois proboscideans are considered in relation to well-dated pollen records from northeastern and central Illinois. These dates span an interval from 21,228 to 12,944 cal BP. When compared to pollen spectra, it is evident that Mammut americanum inhabited spruce (Picea) and black ash (Fraxinus nigra) forest during the B??lling-Aller??d (14,700-12,900 cal BP) and early Younger Dryas (12,900-11,650 cal BP) chronozones. Both Mammuthus jeffersonii and Mammuthus primigenius inhabited spruce dominated open-woodland during the Oldest Dryas chronozone, while M.??primigenius persisted in a forest of predominantly black ash during the Aller??d chronozone. A newly discovered specimen from Lincoln, IL, clarifies the taxonomic distinction between M. primigenius and M.??jeffersonii. Hitherto, a paradigm of proboscidean succession during the full- to late-glacial periods was based on the vegetation succession of steppe tundra-like vegetation to spruce forest to spruce-deciduous forest. The presumed proboscidean succession was that of cold, dry steppe-adapted M. primigenius succeeded by more mesic-tolerant M. jeffersonii that in turn was succeeded by the wet forest-adapted M.??americanum. Reported data do not support this view and indicate a need for re-evaluation of assumptions of proboscidean ecology and history, e.g., the environmental tolerances and habits of M.??primigenius in regions south of 55??N, and its dynamic relationship with other proboscidean taxa. ?? 2009 Elsevier Ltd and INQUA.

Field-Analytical approach of land-sea records for elucidating the Younger Dryas Boundary syndrome

NASA Astrophysics Data System (ADS)

Ge, T.; Courty, M. M.; Guichard, F.

2009-12-01

contrast, microfacies and debris composition of the recurrent fine dust/wildfire events would trace a series of a low energy airburst. Their record is expressed in the Audenge sequence by a series of water-laid laminae of charred pine residues formed of carbonaceous spherules wrapped by carbonaceous polymers that includes lonsdaleite crystals as detected by high resolution in situ micro-Raman analysis. This association suggests recurrent flash forest wildfires ignited by hot spray of carbon-rich debris, followed by heavy snow falls. The record from the Peruvian desert suggests a possible linkage between the repeated debris fall/wildfires during the Younger Dryas and the following irreversible aridity along the Peruvian cost. In contrast the Caspian record of the Younger Dryas period indicates more gradual changes, possibly buffered by the hydrological functioning of the Caspian sea in a complex region. The Audenge context offers the amplified signal needed to understand at local to global scales the spatio-temporal pattern of impact-airburst events.

A Younger Dryas re-advance of local glaciers in north Greenland

NASA Astrophysics Data System (ADS)

Larsen, Nicolaj K.; Funder, Svend; Linge, Henriette; Möller, Per; Schomacker, Anders; Fabel, Derek; Xu, Sheng; Kjær, Kurt H.

2016-09-01

The Younger Dryas (YD) is a well-constrained cold event from 12,900 to 11,700 years ago but it remains unclear how the cooling and subsequent abrupt warming recorded in ice cores was translated into ice margin fluctuations in Greenland. Here we present 10Be surface exposure ages from three moraines in front of local glaciers on a 50 km stretch along the north coast of Greenland, facing the Arctic Ocean. Ten ages range from 11.6 ± 0.5 to 27.2 ± 0.9 ka with a mean age of 12.5 ± 0.7 ka after exclusion of two outliers. We consider this to be a minimum age for the abandonment of the moraines. The ages of the moraines are furthermore constrained using Optically Stimulated Luminescence (OSL) dating of epishelf sediments, which were deposited prior to the ice advance that formed the moraines, yielding a maximum age of 12.4 ± 0.6 ka, and bracketing the formation and subsequent abandonment of the moraines to within the interval 11.8-13.0 ka ago. This is the first time a synchronous YD glacier advance and subsequent retreat has been recorded for several independent glaciers in Greenland. In most other areas, there is no evidence for re-advance and glaciers were retreating during YD. We explain the different behaviour of the glaciers in northernmost Greenland as a function of their remoteness from the Atlantic Meridional Overturning Circulation (AMOC), which in other areas has been held responsible for modifying the YD drop in temperatures.

Testing the Younger Dryas impact hypothesis with platinum-group elements (PGE), Re, and Os isotopes in sediments from Hall's Cave and Freidken Archaeological site, Texas

NASA Astrophysics Data System (ADS)

Sun, N.; Brandon, A. D.; Forman, S. L.

2017-12-01

The Younger Dryas impact hypothesis suggests that extraterrestrial (ET) object(s) hit and exploded over North America 12,900 years ago and triggered the onset of Younger Dryas (YD) cooling and widespread megafaunal extinctions and the demise of the Clovis archeological culture. Supporting signatures such as concentrated carbon spherules and enlogaes, magnetic grains and spherules, nanodiamonds, and Ir-enrichment have been reported, but over time their lack of reproducibility of results at different locations have brought into question the impact hypothesis. Among the impact signatures investigated by previous studies, only few researchers included Re and platinum group element (PGE: Os, Ir, Ru, Rh, Pt, and Pd) characteristic concentrations, and 187Os/188Os ratios for ET mixing in terrestrial materials. Less than 1% of ET materials can provide enriched PGE concentrations, such that PGE are a sensitive tool to identify ET input in terrestrial materials. Because of the large difference between chondritic and continental crust 187Os/188Os ratios, 0.127 and >1.4, respectively, the 187Os/188Os ratios are also highly sensitive indicators of an extraterrestrial component in terrestrial and marine sediments. In this study, we examine sediments associated with the YD from two reported sites in North America, Hall's Cave and the Freidken Archaeological site in Central Texas, using the PGE and Re geochemical approach to test the evidence of the extraterrestrial projectiles during Younger Dryas period. Our current data show at Hall's Cave the PGE concentrations and patterns do not confirm the presence of an elevated meteoritic contribution. However, the 187Os/188Os depth profile shows a sudden 187Os/188Os decrease from 2.28 2.45 to 1.64 at the YD boundary layer, consistent with an increase in material derived from ET projectiles with chondritic 187Os/188Os ratios contaminating the Earth surface at the time of the YD extinction. Additional samples from the YD boundary at the

Hydrological and vegetational response to the Younger Dryas climatic oscillations: a high resolution case study from Quoyloo Meadow, Orkney, Scotland

NASA Astrophysics Data System (ADS)

Maas, David; Abrook, Ashley; Timms, Rhys; Matthews, Ian; Palmer, Adrian; Milner, Alice; Candy, Ian; Sachse, Dirk

2016-04-01

The Younger Dryas (Loch Lomond) Stadial is a well defined period of cold climate that in North West Europe punctuated the climatic amelioration during the Last Glacial - Interglacial Transition (LGIT ca. 16-8 ka). A palaeolake record from Quoyloo Meadow, Orkney Islands (N59.067, E-3.309) has been analysed for pollen and stable isotopes on biomarker lipids. n-Alkanes from terrestrial and aquatic sources are present throughout the core. The average chain length (ACL) is relatively low during the interstadial (~28.0) and shows a distinct increase during the Younger Dryas (to 29.0 +), attributed to an increase in grasses and drought resistant shrubs (e.g. Artemisia, Castañeda et al., 2009, Bunting, 1994). At the beginning of the Holocene, the ACL rapidly drops to 28.3 and from thereon gently increases again to ~29.0. There is a continued odd-over-even n-alkane predominance, although even n-alkanes are present in greater quantities in the interstadial, indicating an increasing terrestrial contribution in the Holocene. Ongoing deuterium isotope measurements of the n-alkanes will give independent evidence for palaeohydrological changes and can be compared to the other proxy evidence within the same core. Using a combination of nC29 and nC23 (terrestrial and aquatic end-members, respectively), a change in relative humidity (rH) can be qualified. This is based on the idea that terrestrial vegetation is affected by evapotranspiration processes, whereas aquatic vegetation is not (Rach et al., 2014). This data is supported by a high resolution palynological study; the contiguously sampled record demonstrates ecosystem/environmental responses to millennial-scale climatic change and allows for the possible detection of vegetation shifts at the sub-millennial scale. Vegetation aside, the pollen data can further aid in the interpretation of the recorded n-alkanes and isotopic analyses. This data is placed within a chronological framework derived from a high resolution crypto- and

First Younger Dryas moraines in Greenland

NASA Astrophysics Data System (ADS)

Funder, Svend; Larsen, Nicolaj K.; Linge, Henriette; Möller, Per; Schomacker, Anders; Fabel, Derek; Kjær, Kurt H.; Xu, Sheng

2016-04-01

Over the Greenland ice sheet the Younger Dryas (YD) cold climate oscillation (12.9-11.7 kaBP) began with up to 10°C drop in temperatures and ended with up to 12°C abrupt warming. In the light of the present warming and melting of the ice sheet, and its importance for future climate change, the ice sheet's response to these dramatic changes in the past is of great interest. However, even though much effort has gone into charting YD ice margin behaviour around Greenland in recent years, no clear-cut signal of response to the oscillation has been uncovered. Here we show evidence to suggest that three major outlets from a local ice cap at Greenland's north coast advanced and retreated synchronously during YD. The evidence comprises OSL (optically stimulated luminescence) dates from a marine transgression of the coastal valleys that preceded the advance, and exposure ages from boulders on the moraines, formed by glaciers that overrode the marine sediment. The OSL ages suggest a maximum age of 12.4 ±0.6 kaBP for the marine incursion, and 10 exposure ages on boulders from the three moraines provide an average minimum age of 12.5 ±0.7 kaBP for the moraines, implying that the moraines were formed within the interval 11.8-13.0 kaBP. Elsewhere in Greenland evidence for readvance has been recorded in two areas. Most notably, in the East Greenland fjord zone outlet glaciers over a stretch of 800 km coast advanced through the fjords. In Scoresby Sund, where the moraines form a wide belt, an extensive 14C and exposure dating programme has shown that the readvance here probably culminated before YD, while cessation of moraine formation and rapid retreat from the moraine belt did not commence until c. 11.5 kaBP, but no moraines have so far been dated to YD. Readvance is also seen in Disko Bugt, the largest ice sheet outlet in West Greenland. However, here the advance and retreat of the ice stream took place in mid YD times, and lasted only a few hundred years, while YD in

Evidences of melting of terrestrial sediments and paleoenvironment changes during the Younger Dryas in tectonic lacustrine basins of Transmexican Volcanic Belt, Mexico.

NASA Astrophysics Data System (ADS)

Israde-Alcantara, I.

2017-12-01

It is well known in the sedimentary record of several parts of the world that during the Younger Dryas interval (YD) ocurred an abrupt environmental change between 12,900 and 11,700 cal yr BP (10,900 to 10,000 14C BP). In the lacustrine basins this changes are often preserved and in some Mexican lakes this is a distinctive stratigraphic marker for the YD. We analized the proxies of this event in cores of two lakes (Chapala, Cuitzeo) and three trenches of ex-lakes (Acambay,Texcoco and El Cedral). Deposits consist of fine detrital material with often Pleistocene fossil vertebrate assemblages. At the Chapala, Cuitzeo, Acambay, and Tocuila lacustrine environments are found in association with a distinctive dark organic layer showing sharp changes in the diatom, pollen, mineralogical and geochemical record. Includes also microscopic magnetic, Fe-rich spherules, silica melted droplets with aerodynamic shapes (tektites), followed by large amounts of charcoal, and sometimes nanodiamonds (Cuitzeo), that were deposited at the onset of the YD or in the limit Pleistocene-Holocene. These unusual materials are buried more than 2.50 meters and were not observed above or below the Younger Dryas sediments at these sites. The geochemistry of the microspherules indicates that they are not volcanic, anthropogenic or authigenic origin. A very distinctive feature is the shape of the spherules, ovoid, polygonal, filigreed or dendritic indicating melting and quenching infering that are product of an impact event. Their morphologies includes hollow shells caused by de-gassing of elements at very high temperatures causing a flattened side with a "skirt" structure by a high-velocity collision.Our results are consistent with the Firestone hypothesis.

Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska

USGS Publications Warehouse

Gaglioti, Benjamin V.; Mann, Daniel H.; Wooller, Matthew J.; Jones, Benjamin M.; Wiles, Gregory C.; Groves, Pamela; Kunz, Michael L.; Baughman, Carson; Reanier, Richard E.

2017-01-01

Declining sea-ice extent is currently amplifying climate warming in the Arctic. Instrumental records at high latitudes are too short-term to provide sufficient historical context for these trends, so paleoclimate archives are needed to better understand the functioning of the sea ice-albedo feedback. Here we use the oxygen isotope values of wood cellulose in living and sub-fossil willow shrubs (δ18Owc) (Salix spp.) that have been radiocarbon-dated (14C) to produce a multi-millennial record of climatic change on Alaska's North Slope during the Pleistocene-Holocene transition (13,500–7500 calibrated 14C years before present; 13.5–7.5 ka). We first analyzed the spatial and temporal patterns of δ18Owc in living willows growing at upland sites and found that over the last 30 years δ18Owc values in individual growth rings correlate with local summer temperature and inter-annual variations in summer sea-ice extent. Deglacial δ18Owcvalues from 145 samples of subfossil willows clearly record the Allerød warm period (∼13.2 ka), the Younger Dryas cold period (12.9–11.7 ka), and the Holocene Thermal Maximum (11.7–9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were ∼4.5‰, which is about 60% of the differences in δ18Owc between those willows growing during the last glacial period and today. Modeling of isotope-precipitation relationships based on Rayleigh distillation processes suggests that during the Younger Dryas these large shifts in δ18Owc values were caused by interactions between local temperature and changes in evaporative moisture sources, the latter controlled by seaice extent in the Arctic Ocean and Bering Sea. Based on these results and on the effects that sea-ice have on climate today, we infer that ocean-derived feedbacks amplified temperature changes and enhanced precipitation in coastal regions of Arctic Alaska during warm times in the past. Today, isotope values in willows on the North Slope of Alaska are

Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska

NASA Astrophysics Data System (ADS)

Gaglioti, Benjamin V.; Mann, Daniel H.; Wooller, Matthew J.; Jones, Benjamin M.; Wiles, Gregory C.; Groves, Pamela; Kunz, Michael L.; Baughman, Carson A.; Reanier, Richard E.

2017-08-01

Declining sea-ice extent is currently amplifying climate warming in the Arctic. Instrumental records at high latitudes are too short-term to provide sufficient historical context for these trends, so paleoclimate archives are needed to better understand the functioning of the sea ice-albedo feedback. Here we use the oxygen isotope values of wood cellulose in living and sub-fossil willow shrubs (δ18Owc) (Salix spp.) that have been radiocarbon-dated (14C) to produce a multi-millennial record of climatic change on Alaska's North Slope during the Pleistocene-Holocene transition (13,500-7500 calibrated 14C years before present; 13.5-7.5 ka). We first analyzed the spatial and temporal patterns of δ18Owc in living willows growing at upland sites and found that over the last 30 years δ18Owc values in individual growth rings correlate with local summer temperature and inter-annual variations in summer sea-ice extent. Deglacial δ18Owc values from 145 samples of subfossil willows clearly record the Allerød warm period (∼13.2 ka), the Younger Dryas cold period (12.9-11.7 ka), and the Holocene Thermal Maximum (11.7-9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were ∼4.5‰, which is about 60% of the differences in δ18Owc between those willows growing during the last glacial period and today. Modeling of isotope-precipitation relationships based on Rayleigh distillation processes suggests that during the Younger Dryas these large shifts in δ18Owc values were caused by interactions between local temperature and changes in evaporative moisture sources, the latter controlled by sea ice extent in the Arctic Ocean and Bering Sea. Based on these results and on the effects that sea-ice have on climate today, we infer that ocean-derived feedbacks amplified temperature changes and enhanced precipitation in coastal regions of Arctic Alaska during warm times in the past. Today, isotope values in willows on the North Slope of Alaska are similar

Oxygen Isotopes and Meltwater: Younger Dryas and 8.2 ka Event

NASA Astrophysics Data System (ADS)

Keigwin, L. D.

2015-12-01

Delta 18-O is one of our most powerful and widely used proxies, with, arguably, the fewest likely unknown unknowns. Here I will consider the d18-O evidence for the two best-known floods of mostly liquid water to the ocean, the Younger Dryas (YD) and the 8.2 ka event. The first d18-O signal of a meltwater flood in the ocean was reported 40 years ago by Kennett and Shackleton (1975) and that paper led directly to the meltwater diversion hypothesis for the origin of the YD cooling. It was later suggested by Rooth (1982) that such a flood could interrupt Nordic seas convection and trigger the YD cold episode. It was reported at this meeting last year that a candidate flood has been found in the Mackenzie River region of the western Arctic based on low d18-O and multiple other lines of evidence. The 8.2 ka event was about one-tenth the duration of the YD but with possibly higher transport, and is more difficult to detect in open marine sediments. As with the YD, it has been modeled by hosing and low salinities have been derived by temperature correcting the d18-O. The resulting low salinity was shown not to follow the prediction of the highest resolution modeling, and theory, that the fresh water would be transported mostly equatorward along the continental shelf. However, I report here that the low d18-O signal of the 8.2 ka flooding is present in new cores from near Logan Canyon on the Scotian shelf break, and in Jordan Basin, Gulf of Maine. These results substantially validate the modeling of Condron and Winsor that fresh water transport must have been along the continental shelf.

Lead and Lags of Lake System Responses to Late Allerød and Early Younger Dryas Climatic Fluctuation - an Example from Varved Lake Sediments from Northern Poland (Central Europe)

NASA Astrophysics Data System (ADS)

Slowinski, M. M.; Zawiska, I.; Ott, F.; Noryśkiewicz, A. M.; Plessen, B.; Apolinarska, K.; Lutyńska, M.; Michczynska, D. J.; Wulf, S.; Skubała, P.; Błaszkiewicz, M.; Brauer, A.

2014-12-01

The transition from the warmer Allerød to the cooler Younger Dryas period is well understood to represent sudden and extreme climate changes during the end of the last glaciation. Thus, lake sediment studies within paleoclimatic and paleoecological research on this transition are ideal to enhance the knowledge about "lead and lags" of lake system responses to abrupt climate changes through applying multi-proxy sediment analyses. In this study, we present the results of high-resolution studies on varved late glacial sediments from the Trzechowskie paleolake, located in the northern Poland (center Europe). High-resolution bio-proxies (pollen, macrofossils, Cladocera and diatoms), geochemical analyses (µ-XRF data, TOC, C/N ratios, δ18Ocarb and δ13Corg stable isotopes) and a robust chronology based on varve counting, AMS 14C dating and tephrochronology were used to reconstruct the lake system responses to rapid climatic and environmental changes of Trzechowskie paleolake during the late Allerød - Younger Dryas transition. Paleoecological and geochemical analyses, which were carried out in a 4 to 16 years temporal sample resolution, allowed to defining short-termed shifts of the ecosystem that were triggered by abrupt climate changes. The rapid and pronounced cooling at the beginning of the Younger Dryas had a major impact on the lake and its catchment as clearly reflected by not synchronous changes of both, biotic and geochemical proxies. The results of high-resolution analysis indicate (a) an increased precipitation during the Allerød-YD transition, which is responsible for an increase of soil erosion in the catchment during this period, (b) a delayed response of the vegetation compared to the lake depositional system at the YD onset of 20 years, and (c) a non-synchronicity of vegetation responses between Western (Lake Meerfelder Maar) and Eastern European sites (Trzechowskie palaeolake) at the YD onset. This study is a contribution to the Virtual Institute

Regional scale climatic trends derived from Younger Dryas glaciers in Britain.

NASA Astrophysics Data System (ADS)

Pearce, Danni; Pellitero, Ramon; Rea, Brice R.; Barr, Iestyn; Small, David; McDougall, Des

2016-04-01

In Britain, the glacial geomorphological record has been utilised to infer palaeo-glacier geometries and ice dynamics, with much of this work focussing on the Younger Dryas (YD; c. 12.9 - 11.7 ka BP). During the YD the West Highlands ice-cap covered the majority of the Scottish Highlands, which is thought to have affected accumulation rates beyond the ice-cap margins, resulting in a steep (c. 80%) easterly decline in precipitation and smaller ice-masses. We present multi-proxy data investigating YD glaciation in the Tweedsmuir Hills, Southern Uplands, Scotland (55°46' N, 03°34' W). The area forms the most easterly upland region in the Southern Uplands and south of the West Highlands ice-cap, reaching an altitude of 840 m and covering c. 300 km2. Results of air-photo interpretation and field mapping, which utilised a morphostratigraphic approach, have demonstrated a more extensive glaciation than previously mapped, suggesting conditions were less arid than previously thought. The reconstruction consists of two separate icefields covering an area c. 60 km2 and new 14C dates of basal contact organics place the ice-mass within the context of the YD but new Cosmogenic Nuclide Analysis (CNA) of bedrock and in situ boulders, imply limited erosion and resetting occurred during the YD. Equilibrium Line Altitudes are calculated to have ranged from c. 419 - 634 m. Palaeo-precipitation values were derived using two precipitation-temperature relationships and suggest slightly lower totals than YD ice-masses located on the west coast of Britain but do not support a significant easterly reduction in precipitation. Analysis of present-day (c. 30 year) meteorological data across Britain demonstrates a pronounced reduction in precipitation of c. 50% on the east coast. This disparity between present-day and glacier-based YD precipitation patterns is partly attributable to the methodology employed in glacier reconstruction and questions the steep precipitation gradients thought to

Testing Younger Dryas ET Impact (YDB) Evidence at Hall’s Cave, Texas

NASA Astrophysics Data System (ADS)

Stafford, T. W.; Lundelius, E.; Kennett, J.; Kennett, D. J.; West, A.; Wolbach, W. S.

2009-12-01

soot at 2400 ppm, magnetic spherules, and carbon spherules, all of which we interpret as evidence for a unique chronostratigraphic marker (YDB) in the Western Hemisphere. Because the age of this horizon is ~ 13,000 CAL BP, we interpret the age of the event as the beginning of the Younger Dryas cooling. Regional soil erosion began ~15,000 CAL BP and continued until 7000 CAL BP, but dating suggests that there is no discontinuity or hiatus in deposition, and thus, the exotic materials in that layer are not considered to be erosional accumulations. Future analyses include sub-centimeter sampling over the YD boundary, quantification of nanodiamonds and other event-proxies within 1000 yr of the boundary and in sediments several 1000 years older and younger, continued refinement of the AMS 14C record to determine within 50 yr the location of 12,900 CAL BP datum and high resolution analysis of small animal biostratigraphy.

A Tree-Ring Chronology and Paleoclimate Record for the Younger Dryas-Early Holocene Transition from Northeastern North America

NASA Technical Reports Server (NTRS)

Griggs, Carol; Peteet, Dorothy; Kromer, Bernd; Grote, Todd; Southon, John

2017-01-01

Spruce and tamarack logs dating from the Younger Dryas and Early Holocene (YDEH; approx. 12.9 - 11.3k cal a BP) were found at Bell Creek in the Lake Ontario lowlands of the Great Lakes region, North America. A 211-year tree-ring chronology dates to approx. 11 755 -11 545 cal a BP, across the YDEH transition. A 23-year period of higher year-to-year ring-width variability dates to around 11 650 cal a BP, infers strong regional climatic perturbations and may represent the end of the YD. Tamarack and spruce were dominant species throughout the YD - EH interval at the site, indicating that boreal conditions persisted into the EH, in contrast to geographical regions immediately south and east of the lowlands, but consistent with the Great Lakes interior lowlands. This infers that Bell Creek was at the eastern boundary of a boreal ecotone, perhaps a result of its lower elevation and the non-analog dynamics of the Laurentide Ice Sheet. This finding suggests that the ecotone boundary extended farther east during the YD - EH transition than previously thought.

Hunted gazelles evidence cooling, but not drying, during the Younger Dryas in the southern Levant

NASA Astrophysics Data System (ADS)

Hartman, Gideon; Bar-Yosef, Ofer; Brittingham, Alex; Grosman, Leore; Munro, Natalie D.

2016-04-01

The climatic downturn known globally as the Younger Dryas (YD; ∼12,900-11,500 BP) has frequently been cited as a prime mover of agricultural origins and has thus inspired enthusiastic debate over its local impact. This study presents seasonal climatic data from the southern Levant obtained from the sequential sampling of gazelle tooth carbonates from the Early and Late Natufian archaeological sites of Hayonim and Hilazon Tachtit Caves (western Galilee, Israel). Our results challenge the entrenched model that assumes that warm temperatures and high precipitation are synonymous with climatic amelioration and cold and wet conditions are combined in climatic downturns. Enamel carbon isotope values from teeth of human-hunted gazelle dating before and during the YD provide a proxy measure for water availability during plant growth. They reveal that although the YD was cooler, it was not drier than the preceding Bølling-Allerød. In addition, the magnitude of the seasonal curve constructed from oxygen isotopes is significantly dampened during the YD, indicating that cooling was most pronounced in the growing season. Cool temperatures likely affected the productivity of staple wild cereal resources. We hypothesize that human groups responded by shifting settlement strategies-increasing population mobility and perhaps moving to the warmer Jordan Valley where wild cereals were more productive and stable.

A link between Late Pliensbachian organic matter preservation and the Spinatum Chronozone icehouse event

NASA Astrophysics Data System (ADS)

Silva, Ricardo L.; Duarte, Luís. V.

2014-05-01

It is recognized today that the "greenhouse" Mesozoic Era includes several short-lived icehouse episodes. One occurred during the Spinatum Chronozone (Late Pliensbachian), which immediately preceded a 2nd-order extinction event and a major carbon cycle perturbation associated to the Early Toarcian Oceanic Anoxic Event. The Lower Jurassic hemipelagic carbonate series of the Lusitanian Basin (Portugal) mark the hinge zone between the Tethyan (Mediterranean) and Boreal (North-European) realms. Here, one of the most obvious features is the organic-rich nature of the majority of the Ibex-Margaritatus chronozones (Pliensbachian) series (Marly-limestones with organic-rich facies member of the Vale das Fontes Formation), capped by a regressive limestone unit of uppermost Margaritatus-lowermost Polymorphum (Toarcian) chronozones (Lemede Formation). The Pliensbachian organic-rich deposition (observed in several locations around the world) is coeval with a positive carbon isotopic excursion recorded in carbonates and organic substrates. For the Lusitanian Basin, evidences points toward the occurrence of brief "hot snaps" prior to the onset of the icehouse interval of Spinatum age. We demonstrate that cooling was preceded by several episodes of organic matter preservation, most likely driven by extreme warming, coupled with high oceanic productivity and stratified (thermally?) epeiric areas. These "hot snaps" allowed the rapid but short-lived expansion of Tethyan ammonites into Boreal domains. They also promoted widespread mucilage and microbial outbreaks preserved in the Lusitanian Basin as black shales, resulting in organic matter deposition and geological carbon storage. So far, the causes for these "hot snaps" remain unclear. This chain of events most likely triggered and/or amplified the Spinatum Chronozone icehouse event, which led to permafrost and/or methane gas hydrates in locations easily disturbed by the subsequent Early Toarcian warming, or/and increased volcanic

The Younger Dryas impact hypothesis: A requiem

NASA Astrophysics Data System (ADS)

Pinter, Nicholas; Scott, Andrew C.; Daulton, Tyrone L.; Podoll, Andrew; Koeberl, Christian; Anderson, R. Scott; Ishman, Scott E.

2011-06-01

The Younger Dryas (YD) impact hypothesis is a recent theory that suggests that a cometary or meteoritic body or bodies hit and/or exploded over North America 12,900 years ago, causing the YD climate episode, extinction of Pleistocene megafauna, demise of the Clovis archeological culture, and a range of other effects. Since gaining widespread attention in 2007, substantial research has focused on testing the 12 main signatures presented as evidence of a catastrophic extraterrestrial event 12,900 years ago. Here we present a review of the impact hypothesis, including its evolution and current variants, and of efforts to test and corroborate the hypothesis. The physical evidence interpreted as signatures of an impact event can be separated into two groups. The first group consists of evidence that has been largely rejected by the scientific community and is no longer in widespread discussion, including: particle tracks in archeological chert; magnetic nodules in Pleistocene bones; impact origin of the Carolina Bays; and elevated concentrations of radioactivity, iridium, and fullerenes enriched in 3He. The second group consists of evidence that has been active in recent research and discussions: carbon spheres and elongates, magnetic grains and magnetic spherules, byproducts of catastrophic wildfire, and nanodiamonds. Over time, however, these signatures have also seen contrary evidence rather than support. Recent studies have shown that carbon spheres and elongates do not represent extraterrestrial carbon nor impact-induced megafires, but are indistinguishable from fungal sclerotia and arthropod fecal material that are a small but common component of many terrestrial deposits. Magnetic grains and spherules are heterogeneously distributed in sediments, but reported measurements of unique peaks in concentrations at the YD onset have yet to be reproduced. The magnetic grains are certainly just iron-rich detrital grains, whereas reported YD magnetic spherules are

Enrichment in 13C of atmospheric CH4 during the Younger Dryas termination

NASA Astrophysics Data System (ADS)

Melton, J. R.; Schaefer, H.; Whiticar, M. J.

2012-07-01

The abrupt warming across the Younger Dryas termination (~11 600 yr before present) was marked by a large increase in the global atmospheric methane mixing ratio. The debate over sources responsible for the rise in methane centers on the roles of global wetlands, marine gas hydrates, and thermokarst lakes. We present a new, higher-precision methane stable carbon isotope ratio (δ13CH4) dataset from ice sampled at Påkitsoq, Greenland that shows distinct 13C-enrichment associated with this rise. We investigate the validity of this finding in face of known anomalous methane concentrations that occur at Påkitsoq. Comparison with previously published datasets to determine the robustness of our results indicates a similar trend in ice from both an Antarctic ice core and previously published Påkitsoq data measured using four different extraction and analytical techniques. The δ13CH4 trend suggests that 13C-enriched CH4 sources played an important role in the concentration increase. In a first attempt at quantifying the various contributions from our data, we apply a methane triple mass balance of stable carbon and hydrogen isotope ratios and radiocarbon. The mass balance results suggest biomass burning (42-66% of total methane flux increase) and thermokarst lakes (27-59%) as the dominant contributing sources. Given the high uncertainty and low temporal resolution of the 14CH4 dataset used in the triple mass balance, we also performed a mass balance test using just δ13C and δD. These results further support biomass burning as a dominant source, but do not allow distinguishing of thermokarst lake contributions from boreal wetlands, aerobic plant methane, or termites. Our results in both mass balance tests do not suggest as large a role for tropical wetlands or marine gas hydrates as commonly proposed.

A Digital 3D-Reconstruction of the Younger Dryas Baltic Ice Lake

NASA Astrophysics Data System (ADS)

Jakobsson, M.; Alm, G.; Bjorck, S.; Lindeberg, G.; Svensson, N.

2005-12-01

A digital 3D-reconstruction of the final stage of the ice dammed Baltic Ice Lake (BIL), dated to the very end of the Younger Dryas cold period (ca. 11 600 cal. yr BP) has been compiled using a combined bathymetric-topographic Digital Terrain Model (DTM), Scandinavian ice sheet limits, Baltic Sea Holocene bottom sediment thickness information, and a paleoshoreline database maintained at the Lund University. The combined bathymetric-topographic Digital Terrain Model (DTM) model used to reconstruct the ice dammed lake was compiled specifically for this study from publicly available data sets. The final DTM is in the form of a digital grid on Lamberts Equal Area projection with a resolution of 500 x 500 m, which permits a much more detailed reconstruction of the BIL than previously made. The lake was constructed through a series of experiments where mathematical algorithms were applied to fit the paleolake's surface through the shoreline database. The accumulated Holocene bottom sediments in the Baltic Sea were subsequently subtracted from the present bathymetry in our reconstruction. This allows us to estimate the Baltic Ice Lake's paleobathymetry, area, volume, and hypsometry, which will comprise key input data to lake/climate modeling exercises following this study. The Scandinavian ice sheet margin eventually retreated north of Mount Billingen, which was the high point in terrain of Southern central Sweden bordering to lower terrain further to the North. As a consequence, the BIL was catastrophically drained through this area, resulting in a 25 m drop of the lake level. With our digital BIL model we estimate that approximately 7, 800 km3 of water drained during this event and that the ice dammed lake area was reduced with ca 18 percent. The digital BIL reconstruction is analyzed using 3D-visualization techniques that provide new detailed information on the paleogeography in the area, both before and after the lake drainage, with implications for interpretations of

Lacustrine lignin biomarker record reveals a severe drought during the late Younger Dryas in southern Taiwan

NASA Astrophysics Data System (ADS)

Ding, Xiaodong; Bao, Hongyan; Zheng, Liwei; Li, Dawei; Kao, Shuh-Ji

2017-03-01

The Younger Dryas (YD) event, which punctuated the last glacial-Holocene transition period and had a profound impact on global climate, is the most well studied millennial-scale climate event although the triggering mechanism remains debate. Weakened Asian summer monsoon during the YD is recorded in oxygen isotopes of stalagmite from Mainland China. However, lacustrine climate record of the YD event has not been reported from the subtropical land-ocean boundary of the Asian continent near the Pacific warm pool. We provide a lignin biomarker record covering the last deglaciation and early Holocene (17-9 ka BP) from the Dongyuan Lake, southern Taiwan, located at the frontal zone of typhoon invasion. The lignin phenol ratio S/V shows that the vegetation in the catchments had shifted from gymnosperm dominant to angiosperm dominant plants since 12.2 ka BP. Significantly decreased lignin concentrations (TLP and λ8) and elevated lignin degradation parameters ((Ad/Al)v, P/(V + S), DHBA/V) in combination with other organic proxies (TOC, δ13Corg) during the late YD suggest a severe drought had occurred in southern Taiwan during this specific period. Changes in the lignin proxies from the Dongyuan Lake lagged the climate changes registered in stalagmite records by around 500-800 years, suggesting a slow response of vegetation and soil processes to rapid climate changes.

Environment and paleoecology of a 12 ka mid-North American Younger Dryas forest chronicled in tree rings

USGS Publications Warehouse

Panyushkina, Irina P.; Leavitt, Steven W.; Thompson, Todd A.; Schneider, Allan F.; Lange, Todd

2008-01-01

Until now, availability of wood from the Younger Dryas abrupt cooling event (YDE) in N. America ca. 12.9 to 11.6 ka has been insufficient to develop high-resolution chronologies for refining our understanding of YDE conditions. Here we present a multi-proxy tree-ring chronology (ring widths, “events” evidenced by microanatomy and macro features, stable isotopes) from a buried black spruce forest in the Great Lakes area (Liverpool East site), spanning 116 yr at ca. 12,000 cal yr BP. During this largely cold and wet period, the proxies convey a coherent and precise forest history including frost events, tilting, drowning and burial in estuarine sands as the Laurentide Ice Sheet deteriorated. In the middle of the period, a short mild interval appears to have launched the final and largest episode of tree recruitment. Ultimately the tops of the trees were sheared off after death, perhaps by wind-driven ice floes, culminating an interval of rising water and sediment deposition around the base of the trees. Although relative influences of the continental ice sheet and local effects from ancestral Lake Michigan are indeterminate, the tree-ring proxies provide important insight into environment and ecology of a N. American YDE boreal forest stand.

Too early and too northerly: evidence of temperate trees in northern Central Europe during the Younger Dryas.

PubMed

Robin, Vincent; Nadeau, Marie-Josée; Grootes, Pieter M; Bork, Hans-Rudolf; Nelle, Oliver

2016-10-01

This paper presents highly unexpected paleobotanical data. Eight (14) C-accelerator mass spectrometry (AMS) dates of soil macrocharcoal pieces, identified taxonomically, indicate the presence of oak and beech in the Younger Dryas, and pine in the Allerød, in the northernmost low mountain range of Central Europe, the Harz Mountains, in Germany. If the presence of pine at such latitude and periods is not surprising, the presence of temperate-adapted trees is highly improbable, because they are assumed to have reached the area from a southern location several thousand years later. Two hypotheses are postulated to explain this record. Both are related to the warm periods of the Bølling and Allerød: the classically 'short' duration of this warm period makes the migration of the temperate trees from the identified refuge areas in the southern location implausible, and so the presence of intermediary microrefugia at a medium latitude in Central Europe is postulated; recent data reveal that the warm period of the Late Glacial phase was much longer than considered in the classical view and, thus, would be long enough for a northward migration of temperate-adapted trees. Although our dataset does not permit disentanglement of these hypotheses, it provides significant innovative insights for the biogeography of Central Europe. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Warm ocean surface led to ice margin retreat in central-eastern Baffin Bay during the Younger Dryas

NASA Astrophysics Data System (ADS)

Oksman, Mimmi; Weckström, Kaarina; Miettinen, Arto; Juggins, Stephen; Divine, Dmitry; Jackson, Rebecca; Korsgaard, Niels J.; Telford, Richard; Kucera, Michal

2017-04-01

The Greenland ice sheet stability is linked to fast-flowing ice streams that are influenced by sea surface temperatures (SSTs) at their front. One of the largest ice streams in West Greenland is the Jakobshavn Isbræ, which has been shown to have collapsed at ca. 12.2 kyr BP in the middle of the Younger Dryas (YD) cold period (12.9-11.7 kyr BP). The cause for this collapse is still unknown yet hypotheses, such as warm Atlantic water inflow, have been put forward to explain it. Here we present the first diatom-based high-resolution reconstruction of sea surface conditions in the central-eastern Baffin Bay between 14.0 and 10.2 kyr BP. The sea surface temperatures reveal warmer conditions beginning at ca. 13.4 kyr BP and leading to intensive calving and iceberg discharge from Jakobshavn Isbræ visible as increased sedimentation rates and deposition of coarse-grained material in our sediment stratigraphy. The warm YD ocean surface conditions in Baffin Bay are out of phase with the δ18O record from the North Greenland Ice Core Project (NGRIP) and other SST records from northern North-Atlantic. We show that the ocean has had significant interactions with the Greenland ice sheet in the past and emphasize its importance under the current warming of the North Atlantic.

How Synchronous was the Transition into the Younger Dryas across the Euro-Atlantic Region?

NASA Astrophysics Data System (ADS)

Schenk, F.; Muschitiello, F.; Heikkilä, M. P.; Väliranta, M.; Tarasov, L.; Brandefelt, J.; Johansson, A. V.; Naslund, J. O.; Wohlfarth, B.

2015-12-01

Observations of a currently weakening subpolar gyre south of Greenland has again increased scientific attention regarding the role of the Atlantic Meridional Overturning Circulation (AMOC) for the regional to global climate. The rapid climate shift of the Younger Dryas (YD, GS-1) cold reversal during the last deglaciation is attributed to an abrupt slowdown or collapse of the AMOC due to a strong meltwater pulse and/or the rapid disintegration of the Laurentide Ice sheet. Although such a dramatic event is not expected for the future, the spatiotemporal climatic response to such a slowdown is an interesting test case. Two recently well dated proxy records around the North Sea region suggest a non-synchronous early cooling/onset of the YD compared to Greenland (NGRIP). Presentation #61803 discusses the hypothesis of a local cooling as a response to increased ice berg calving and/or meltwater from Fenno-Scandinavian Ice Sheet (FIS) during the late Alleröd warm phase (GI-1a). Here we study CCSM3 model output from the quasi-transient atmosphere-ocean simulation (TraCE) where no strong contribution from FIS is considered from the late Alleröd into the YD. We evaluate to which extent the spatiotemporal temperature response to the AMOC slowdown of the simulation is synchronous over the Euro-Atlantic region and how atmospheric teleconnections reorganize during the rapid shift into the YD. In addition, we run time-slice experiments at high spatial resolution of around 100 km with the Community Earth System Model CESM1.0.5 for the late Alleröd and YD to compare spatial climatic differences for both periods taking into account the regional influence from continental ice sheets in more detail.

Search for Extraterrestrial Osmium at the Allerod - Younger Dryas Boundary

NASA Astrophysics Data System (ADS)

Beets, C.; Sharma, M.; Kasse, K.; Bohncke, S.

2008-12-01

Ir and Os are excellent markers of extraterrestrial impact events, due to their high abundance in ET objects (Alvarez et al., 1980 Science; Turekian, 1982 Geol. Bull. Am. Spec. Pap.). Os has the advantage over Ir, in that the 187Os/188Os ratio also greatly differs between meteorites and upper continental crust (UCC). The combination of [Os] and 187Os/188Os analyses would be superior in detecting any ET contribution. Firestone et al (2007 PNAS) attributed a widespread 12.9 ka Ir containing black carbon layer to a potential extraterrestrial impact at the Allerød-Younger Dryas (A-YD) boundary. In order to test this inference, we measured [Os] and 187Os/188Os on a radiocarbon dated A-YD record (13.210 to 12.788 cal years BP) from the Netherlands. This location is close to Lommel, a Belgian site studied by Firestone et al.(2007). The organic-rich sequence was sampled continuously over a 12 cm interval at 2 cm resolution (~70 years). About 10 g samples were freeze-dried, ground and homogenized in a zirconia ball-mill. The samples mixed with 190Os tracer solutions were dissolved in carius tubes and Os extracted in liquid bromine. Os was further purified using micro-distillation. Os isotopes were measured using N-TIMS on Dartmouth Triton. The procedural blank was 7 fg/g Os with an isotopic composition of 0.41±0.01 The Allerød samples have an order of magnitude higher abundance than UCC (200 vs. 30 pg/g), but similar 187Os/188Os ratios, >1.1. The sample at the base of the YD (12.893±75 cal years BP) contains a similar amount of Os, but has a distinctly lower isotopic signature, 0.53±0.002. The high [Os] in the A-YD section possibly reflects enrichment by preferential partitioning into organic matter. The Os isotope composition of 0.53, sandwiched between values >1.1, implies contribution of a significant amount of non-radiogenic Os. Since the pollen spectra show no reworking, the non-radiogenic Os could only have been delivered as a discrete pulse at 12.893 cal yr BP

Evidence for a bi-partition of the Younger Dryas Stadial in East Asia associated with inversed climate characteristics compared to Europe.

PubMed

Schlolaut, Gordon; Brauer, Achim; Nakagawa, Takeshi; Lamb, Henry F; Tyler, Jonathan J; Staff, Richard A; Marshall, Michael H; Bronk Ramsey, Christopher; Bryant, Charlotte L; Tarasov, Pavel E

2017-03-31

The Younger Dryas Stadial (YDS) was an episode of northern hemispheric cooling which occurred within the Last Glacial Interglacial Transition (LGIT). A major driver for the YDS climate was a weakening of the Atlantic Meridional Overturning Circulation (AMOC). It has been inferred that the AMOC began to strengthen mid-YDS, producing a bipartite structure of the YDS in records from continental Europe. These records imply that the polar front and westerlies shifted northward, producing a warmer second phase of the YDS in Europe. Here we present multi-proxy data from the sediments of Lake Suigetsu (Japan), as evidence that a related bi-partition of the YDS also occurred in East Asia. Besides showing for the first time that the bi-partition was not limited to the North Atlantic/European region, the data also imply a climatic dipole between Europe and East Asia since the cold-warm characteristics are reversed at Lake Suigetsu. We suggest that changes in eastward moisture transport from the North Atlantic are the primary mechanism by which the teleconnection can be explained.

Climate Reconstructions of the Younger Dryas: An ELA Model Investigating Variability in ELA Depressions, Temperature, and Precipitation Changes for the Graubϋnden Alps

NASA Astrophysics Data System (ADS)

Keeler, D. G.; Rupper, S.; Schaefer, J. M.; Finkel, R. C.

2015-12-01

The high sensitivity of mountain glaciers to even small perturbations in climate, combined with a near global distribution, make alpine glaciers an important target for terrestrial paleoclimate reconstructions. The geomorphic remnant of past glaciers can yield important insights into past climate, particularly in regions where other methods of reconstruction are not possible. The quantitative conversion of these changes in geomorphology to a climate signal, however, presents a significant challenge. A particular need exists for a versatile climate reconstruction method applicable to diverse glacierized regions around the globe. Because the glacier equilibrium line altitude (ELA) provides a more explicit comparison of climate than properties such as glacier length or area, ELA methods lend themselves well to such a need, and allow for a more direct investigation of the primary drivers of mountain glaciations during specific events. Here, we present an ELA model for quantifying changes in climate based on changes in glacier extent, while accounting for differences in glacier width, glacier shape, bed topography, ice thickness, and glacier length. The model furthermore provides bounds on the ΔELA using Monte Carlo simulations. These methods are validated using published mass balances and ELA measurements from 4 modern glaciers in the European Alps. We then use this ELA model, combined with a surface mass and energy balance model, to estimate the changes in temperature/precipitation between the Younger Dryas (constrained by 10Be surface exposure ages) and the present day for three glacier systems in the Graubϋnden Alps. Our results indicate an ELA depression in this area of 257 m ±45 m during the Younger Dryas (YD) relative to today. This corresponds to a 1.3 °C ±0.36 °C decrease in temperature or a 156% ±30% increase in precipitation relative to today. These results indicate the likelihood of a predominantly temperature-driven change rather than a strong

Unravelling Younger Dryas glaciation in the Tweedsmuir Hills, Southern Uplands, Scotland.

NASA Astrophysics Data System (ADS)

Pearce, Danni; Rea, Brice; Barr, Iesytn; Everest, Jeremy; Primmer, Nick; Langdon, Pete; Edwards, Mary; McDougall, Des

2013-04-01

In Britain, the glacial geomorphological record has been widely utilised to infer palaeo-glacier geometries and ice dynamics with much of this work focussing on the Scottish Highlands during the Last Glacial Interglacial Transition (LGIT), in particular the Younger Dryas (YD; c. 12.9 - 11.7 ka BP). The Southern Uplands represents the largest upland area south of the Highlands but have received limited research attention over the last century. The Tweedsmuir Hills are located in the central Southern Uplands, which form an area of dissected plateau approximately 320 km2. Early research in the 1800s identified a range of glacial landforms thought to be associated with the YD. The majority of previous work has focussed on isolated valleys and ignored the potential for plateau icefield glaciation, which has significant implications for understanding of the dynamics and geometries of the YD ice masses. Recent numerical modelling experiments covering the period 38 - 10.4 ka BP (Hubbard et al., 2008 cf. E109B8 and E102b2) have predicted a significant body of ice for the Southern Uplands at the onset of and throughout the YD, which cannot be verified at present due to a lack of empirical data. This research aims to provide the first systematic mapping and climate reconstruction for the Tweedsmuir Hills. The results of air-photo interpretation and field mapping, which utilised a morphostratigraphic approach, has demonstrated a more extensive glaciation than previously mapped. This consists of two separate icefields over the southern and northern Tweedsmuir Hills which cover an area c. 45 km2 and 25 km2 respectively with Equilibrium Line Altitudes (ELAs) calculated to have ranged from c. 419 m to 634 m. For both icefields ELAs of individual outlets reflect topographic controls rather than steep precipitation gradients like those derived for other icefields in Scotland (e.g., the Monadhliath Mountains and Beinn Dearg). New radiocarbon dating of basal stratigraphies and

Regional scale climatic trends derived from Younger Dryas glaciers in the U.K.

NASA Astrophysics Data System (ADS)

Pearce, D.; Rea, B. R.; Barr, I.; Small, D.; McDougall, D.

2014-12-01

In the U.K., the glacial geomorphological record has been utilised to infer paleo-glacier geometries and ice dynamics, with much of this work focussing on the Scottish Highlands during the Younger Dryas (YD; c. 12.9 - 11.7 ka BP). During the YD the West Highlands Ice-cap covered the majority of the Scottish Highlands (c. 13,000 sq mi), which is thought to have affected accumulation rates beyond the ice-cap margins, resulting in a steep (c. 80%) easterly decline in precipitation and smaller ice-masses. We present multi-proxy data investigating YD glaciation in the Tweedsmuir Hills, Southern Uplands, Scotland (55°46' N, 03°34' W), suggesting conditions were less arid. The area forms the most easterly upland region in the Southern Uplands and south of the West Highlands Ice-cap, reaching an altitude of 840 m and covering c. 200 sq mi. Results of air-photo interpretation and field mapping, which utilised a morphostratigraphic approach, have demonstrated a more extensive glaciation than previously mapped. The reconstruction consists of two separate icefields covering an area c. 40 sq mi. and new 14C dates of basal contact organics place the ice-mass within the context of the YD but new Cosmogenic Nuclide Analysis (CNA) of bedrock and in situ boulders are inconclusive, implying limited erosion and limited resetting during the YD. Equilibrium Line Altitudes are calculated to have ranged from c. 419 - 634 m. Paleo-precipitation values were derived using two precipitation-temperature relationships and suggest slightly lower totals than YD ice-masses located on the west coast of the U.K. but do not support a significant easterly reduction in precipitation. Analysis of present-day (c. 30 year) meteorological data across the U.K. demonstrates a pronounced reduction in precipitation of c. 50% on the east coast. This disparity between present-day and glacier-based YD precipitation patterns is partly attributable to the methodology employed in glacier reconstruction and

Quartz microstructures in the Younger Dryas boundary layer ~12.9 ka.

NASA Astrophysics Data System (ADS)

van Hoesel, A.; Hoek, W. Z.; Pennock, G. M.; Drury, M. R.

2012-04-01

In 2007, Firestone et al. proposed that an extraterrestrial impact occurred at the end of the Allerød interstadial, destabilizing the North American ice sheet and initiating the colder Younger Dryas (YD) stadial. Up to now, the evidence for this proposed impact has been heavily debated (Pinter et al., 2011) and no one has been able to provide convincing evidence in favour of the hypothesis. Two years later, Mahaney et al. (2009) claimed that they had frequently found planar deformation features (PDFs) in quartz from a possible YD boundary layer in Venezuela. However, the data presented consisted of an SEM image of the surface of a quartz grain only, and in following work Mahaney et al. (2010) stated that they had found no irrefutable evidence of PDFs. Instead, they showed grains with oriented cracks along their edges, which they claimed to be related to the 'mass impact and extreme heat' from incoming ejecta material. However, oriented cracks are not accepted evidence for an impact (French, Koeberl, 2010). We investigate the quartz fraction of samples from the European Usselo horizon, an Allerød-YD age soil, as well as one sample from the North American Black Mat, which marks the onset of the YD. Possible shocked quartz grains were isolated using density separation, mounted in epoxy and polished. No evidence for oriented cracks along grain edges, like those reported by Mahaney et al. (2010), has been found so far. Transmitted light microscopy showed that a number of grains contained tectonic deformation lamellae. One grain from the Usselo horizon contains at least two sets of closely spaced, straight, and narrow lamellae, similar to PDFs. In SEM-CL imaging however, only some of these lamellae showed up as non-luminescent, while most had the same intensity as the host grain. This is not typical for PDFs (Hamers, Drury 2011). It is possible that these lamellae represent planar fractures, which also form by low pressure shock processes. It must be noted that even if

Reply to comment by E. Bard et al. on "Younger Dryas sea level and meltwater pulse 1B recorded in Barbados reef crest coral Acropora palmata" by N. A. Abdul et al.

NASA Astrophysics Data System (ADS)

Mortlock, Richard A.; Abdul, Nicole A.; Wright, James D.; Fairbanks, Richard G.

2016-12-01

Abdul et al. (2016) presented a detailed record of sea level at Barbados (13.9-9 kyr B.P.) tightly constraining the timing and amplitude during the Younger Dryas and Meltwater Pulse 1B (MWP-1B) based on U-Th dated reef crest coral species Acropora palmata. The Younger Dryas slow stand and the large (14 m) rapid sea level jump are not resolved in the Tahiti record. Tahiti sea level estimates are remarkably close to the Barbados sea level curve between 13.9 and 11.6 kyr but fall below the Barbados sea level curve for a few thousand years following MWP-1B. By 9 kyr the Tahiti sea level estimates again converge with the Barbados sea level curve. Abdul et al. (2016) concluded that Tahiti reefs at the core sites did not keep up with intervals of rapidly rising sea level during MWP-1B. We counter Bard et al. (2016) by showing (1) that there is no evidence for a hypothetical fault in Oistins Bay affecting one of the Barbados coring locations, (2) that the authors confuse the rare occurrences of A. palmata at depths >5 m with the "thickets" of A. palmata fronds representing the reef-crest facies, and (3) that uncertainties in depth habitat proxies largely account for differences in Barbados and Tahiti sea level differences curves with A. palmata providing the most faithful proxy. Given the range in Tahiti paleodepth uncertainties at the cored sites, the most parsimonious explanation remains that Tahiti coralgal ridges did not keep up with the sea level rise of MWP-1B.

Evidence for an extraterrestrial impact 12,900 years ago thatcontributed to megafaunal extinctions and the Younger Dryas cooling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Firestone, R.B.; West, A.; Kennett, J.P.

2007-08-06

A carbon-rich black layer, dating to ~;12.9 ka, has beenpreviously identified at ~;50 Clovis-age sites across North America andappears contemporaneous with the abrupt onset of Younger Dryas (YD)cooling. The in situ bones of extinct Pleistocene megafauna and Clovistool assemblages occur below this black layer but not within or above it.Causes for the extinctions, the YD cooling, and the termination of Clovisculture have long been controversial. In this paper, we provide evidencefor an extraterrestrial (ET) impact event at ?12.9 ka, which, wehypothesize, caused abrupt environmental changes that contributed to YDcooling, major ecological reorganization, broad-scale extinctions, andrapid human behavioral shifts at themore » end of the Clovis Period. Clovis-agesites in North American are overlain by a thin, discrete layer withvarying peak abundances of: (1) magnetic grains with iridium, (2)magnetic microspherules (3) charcoal, (4) soot, (5) carbon spherules, (6)glass-like carbon, and (7) fullerenes with ET helium, all of which areevidence for an ET impact and associated biomass burning at ~;12.9 ka.This layer also extends throughout at least fifteen Carolina Bays, whichare unique, elliptical wetlands, oriented to thenorthwest across theAtlantic Coastal Plain. We propose that one or more large, low-density ETobjects exploded over northern North America, partially destabilizing theLaurentide Ice Sheet and triggering YD cooling. The shock wave, thermalpulse, and event-related environmental effects (e.g., extensive biomassburning, food limitations) contributed to the end-Pleistocene megafaunalextinctions and adaptive shifts among PaleoAmericans in NorthAmerica.« less

Changes in El Nino - Southern Oscillation (ENSO) conditions during the Younger Dryas revealed by New Zealand tree-rings.

NASA Astrophysics Data System (ADS)

Palmer, Jonathan; Turney, Chris; Cook, Edward; Fenwick, Pavla; Thomas, Zoë; Helle, Gerhard; Jones, Richard; Clement, Amy; Hogg, Alan; Southon, John; Bronk Ramsey, Christopher; Staff, Richard; Muscheler, Raimund; Corrège, Thierry; Hua, Quan

2017-04-01

The warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in Greenland (Greenland Stadial 1 or GS-1) and Europe (Younger Dryas Stadial or YD). This reversal to glacial-like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remains uncertain. Whilst the wider Atlantic region has a network of high-resolution proxy records spanning the YD, the Pacific Ocean suffers from a scarcity of sub-decadally resolved sequences. Here we report the results from an investigation into a tree-ring chronology from northern New Zealand aimed at addressing the paucity of data. The conifer tree species kauri (Agathis australis) is known from contemporary studies to be sensitive to regional climate changes. An analysis of a 'historic' 452-year kauri chronology confirms a tropical-Pacific teleconnection via the El Niño - Southern Oscillation (ENSO). We then focus our study to a 1010-year subfossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring-width downturn between 12,500 to 12,380 cal BP within the YD. Wavelet analysis shows a marked increase in ENSO-like periodicities occurring after the downturn event. Comparison to low- and mid-latitude Pacific records suggests a coherency in the changes to ENSO and Southern Hemisphere westerly airflow during this period. The drivers for this climate event remain unclear but may be related to solar changes that subsequently led to establishment and/or increased expression of ENSO across the mid-latitudes of the Pacific, seemingly independent of the Atlantic and polar regions.

Glaciation style and the geomorphological record: evidence for Younger Dryas glaciers in the eastern Lake District, northwest England

NASA Astrophysics Data System (ADS)

McDougall, Derek

2013-08-01

The Younger Dryas (c. 12,900-11,700 years ago) in Britain witnessed renewed glaciation, with the readvance of ice masses that had survived the preceding Lateglacial Interstadial as well as the formation of new glaciers. The extents of these former glaciers have been mapped by many workers over the past fifty years, usually as a basis for palaeoclimatic investigations. It has frequently been asserted that the landform record is sufficiently clear to allow accurate ice mass reconstructions at or near maximum extents. Detailed geomorphological mapping in the eastern Lake District in NW England, however, demonstrates that this confidence may not always be warranted. Whereas previous workers have interpreted the well-developed moraines that exist in some locations as evidence for an alpine-style of glaciation, with ice restricted to a small number of valleys, this study shows that the most recent glaciation to affect the area was characterised by: (i) extensive summit icefields, which supplied ice to the surrounding valleys; and (ii) a much greater volume of ice in the valleys than previously thought. The discovery that summit icefields were relatively common at this time is consistent with recent studies elsewhere in the Lake District and beyond. More significant, however, is the recognition that changing glacier-topographic interactions over both space and time appears to have had a profound impact on valley-floor glacial landform development, with the absence of clear moraines not necessarily indicating ice-free conditions at this time. This complicates glacier reconstructions based solely on the geomorphological record. Similar geomorphological complexity may be present in other areas that previously supported summit icefields, and this needs to be taken into account in glacier reconstructions.

Low-latitude expressions of high-latitude forcing during Heinrich Stadial 1 and the Younger Dryas in northern South America

NASA Astrophysics Data System (ADS)

Bahr, André; Hoffmann, Julia; Schönfeld, Joachim; Schmidt, Matthew W.; Nürnberg, Dirk; Batenburg, Sietske J.; Voigt, Silke

2018-01-01

Changes in Atlantic Meridional Overturning Circulation (AMOC) strength exert a major influence on global atmospheric circulation patterns. However, the pacing and mechanisms of low-latitude responses to high-latitude forcing are insufficiently constrained so far. To elucidate the interaction of atmospheric and oceanic forcing in tropical South America during periods of major AMOC reductions (Heinrich Stadial 1 and the Younger Dryas) we generated a high-resolution foraminiferal multi-proxy record from off the Orinoco River based on Ba/Ca and Mg/Ca ratios, as well as stable isotope measurements. The data clearly indicate a three-phased structure of HS1 based on the reconfiguration of ocean currents in the tropical Atlantic Ocean. The initial phase (HS1a) is characterized by a diminished North Brazil Current, a southward displacement of the ITCZ, and moist conditions dominating northeastern Brazil. During subsequent HS1b, the NBC was even more diminished or yet reversed and the ITCZ shifted to its southernmost position. Hence, dryer conditions prevailed in northern South America, while eastern Brazil experienced maximally wet conditions. During the final stage, HS1c, conditions are similar to HS1a. The YD represents a smaller amplitude version of HS1 with a southward-shifted ITCZ. Our findings imply that the low-latitude continental climate response to high-latitude forcing is mediated by reconfigurations of surface ocean currents in low latitudes. Our new records demonstrate the extreme sensitivity of the terrestrial realm in tropical South America to abrupt perturbations in oceanic circulation during periods of unstable climate conditions.

A large drop in atmospheric [sup 14]C/[sup 12]C and reduced melting in the younger dryas, documented with [sup 230]Th ages of corals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edwards, R.L.; Beck, J.W.; Burr, G.S.

1993-05-14

Paired carbon-14 ([sup 14]C) and thorium-230 ([sup 230]Th) ages were determined on fossil corals from the Huon Peninsula, Papua New Guinea. The ages were used to calibrate part of the [sup 14]C time scale and to estimate rates of sea-level rise during the last deglaciation. An abrupt offset between the [sup 14]C and [sup 230]Th ages suggests that the atmospheric [sup 14]C/[sup 12]C ratio dropped by 15 percent during the latter part of and after the Younger Dryas (YD). This prominent drop coincides with greatly reduced rates of sea-level rise. Reduction of melting because of cooler conditions during the YDmore » may have caused an increase in the rate of ocean ventilation, which caused the atmospheric [sup 14]C/[sup 12]C ratio to fall. The record of sea-level rise also shows that globally averaged rates of melting were relatively high at the beginning of the YD. Thus, these measurements satisfy one of the conditions required by the hypothesis that the diversion of meltwater from the Mississippi to the St. Lawrence River triggered the YD event. 41 refs., 5 figs., 1 tab.« less

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling.

PubMed

Firestone, R B; West, A; Kennett, J P; Becker, L; Bunch, T E; Revay, Z S; Schultz, P H; Belgya, T; Kennett, D J; Erlandson, J M; Dickenson, O J; Goodyear, A C; Harris, R S; Howard, G A; Kloosterman, J B; Lechler, P; Mayewski, P A; Montgomery, J; Poreda, R; Darrah, T; Hee, S S Que; Smith, A R; Stich, A; Topping, W; Wittke, J H; Wolbach, W S

2007-10-09

A carbon-rich black layer, dating to approximately 12.9 ka, has been previously identified at approximately 50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at approximately equal 12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at approximately 12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

PubMed Central

Firestone, R. B.; West, A.; Kennett, J. P.; Becker, L.; Bunch, T. E.; Revay, Z. S.; Schultz, P. H.; Belgya, T.; Kennett, D. J.; Erlandson, J. M.; Dickenson, O. J.; Goodyear, A. C.; Harris, R. S.; Howard, G. A.; Kloosterman, J. B.; Lechler, P.; Mayewski, P. A.; Montgomery, J.; Poreda, R.; Darrah, T.; Hee, S. S. Que; Smith, A. R.; Stich, A.; Topping, W.; Wittke, J. H.; Wolbach, W. S.

2007-01-01

A carbon-rich black layer, dating to ≈12.9 ka, has been previously identified at ≈50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ≅12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ≈12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America. PMID:17901202

Evaluating the flux of extraterrestrial osmium at the onset of Younger Dryas in the GRIP ice core

NASA Astrophysics Data System (ADS)

Seo, J. H.; Han, C.; Hong, S.; Steffensen, J. P.; Sharma, M.

2016-12-01

The Younger Dryas (YD: 12.9-11.6 ka) was an abrupt cooling event during the last deglaciation. The mechanism behind the cooling is suggested to be a temporary slowdown of North Atlantic thermohaline circulation due to catastrophic release of meltwater from proglacial Lake Agassiz during the retreat of the Laurentide Ice Sheet [1]. An alternative hypothesis states that the cooling was directly/indirectly triggered by one or more cosmic airbursts/impacts [2]. While several papers have documented evidence for a YD extraterrestrial impact including microspherules, nanodiamonds, magnetic grains, and glass-like carbon [4-7], this hypothesis remains controversial [8-10]. In a recent study by Petaev et al. [11], an unusually high Pt/Ir ratio of 1200 was discovered in the GISP-2 ice core at the onset of YD, indicating a large Pt enriched iron meteorite impact. Such a high Pt/Ir in extraterrestrial materials has not been documented [12]. Thus, Petaev et al. [11] acknowledge that the interpretation of the Pt anomaly is based on circumstantial evidence. The distinct Os isotopic composition (187Os/188Os ratio) of the terrestrial (=1.26) and extraterrestrial (= 0.13) sources should allow us to evaluate if there was a meteorite impact at the YD boundary. These analyses are technically challenging owing to rather low concentration of Os in ice-melts ( 1x10-15g/g). Here, we will present Os isotope data from the GRIP ice core spanning the time period through YD to shed light on the meteorite/comet impact hypothesis. [1] Broecker et al. (1989) Nature 341, 318-321; [2] Firestone et al. (2007) PNAS. 104, 16016-16021; [3] Bunch et al. (2012) PNAS. 109, 1903-1912; [4] LeCompte et al. (2012) PNAS. 109, 2960-2969; [5] Wittke et al. (2013) PNAS 110, 2088-2097; [6] Wu et al. (2013) PNAS. 110, 3557-3566; [7] Kennett et al. (2015) PNAS 112, E4344-E4353; [8] Pinter et al. (2011) Earth Sci. Rev., 106, 247-264; [9] Holliday et al. (2014) J. Quat. Sci. 29, 515-530; [10] Meltzer et al. (2014) PNAS

Younger Dryas to Early Holocene paleoclimate in Cantabria (N Spain): Constraints from speleothem Mg, annual fluorescence banding and stable isotope records

NASA Astrophysics Data System (ADS)

Rossi, Carlos; Bajo, Petra; Lozano, Rafael P.; Hellstrom, John

2018-07-01

The Younger Dryas (YD) stadial represents the most abrupt climate change of the Earth's recent history. Thus, understanding its causes and different local responses is relevant for Quaternary paleoclimatology. We present a speleothem high-resolution proxy record of the Lateglacial to Early Holocene paleoclimate of the Cantabrian Cordillera (N Spain), a strategic location to evaluate the influence of North Atlantic events such as the YD on South-Western Europe. Fluorescence lamination, growth-rate, stable-isotope, and [Mg] records from stalagmite SIR-1 were dated using an age-depth model constrained by U-Th dates and annual-lamina counting. The YD is recorded as a prominent positive δ13C excursion whose chronology (12.95 ± 0.14 to 11.62 ± 0.16 ka) and shape closely agree with the GS-1 stadial as defined in Greenland ice, supporting the event synchronicity in both areas. A colder and drier YD climate limited soil productivity and dripwater availability, leading to higher δ13C and [Mg], reduced growth rate, and virtually absent fluorescence lamination. The early YD record (until ∼12.5 ka) reflects increasing aridity, whereas the late YD (from ∼12.2 ka on) shows the opposite trend. At the YD boundaries, temperature changes influenced the [Mg] record by modifying the Mg partition into calcite. However, this effect was superseded by major changes in dripwater Mg/Ca linked to rainfall variations. During the Early Holocene, the Arnero Sierra was forested and had a relatively warm and humid seasonal climate, indicated in SIR-1 by higher growth rates, lower δ13C and [Mg], and well-developed fluorescent lamination. Similar to other high-resolution stalagmitic records of the Cordillera, from ∼8.5 to 8.0 ka SIR-1 reflects a temporary trend of increasing aridity.

The Rock Magnetic Record Across the 12.9 ka Younger Dryas Boundary: Evidence for Impact?

NASA Astrophysics Data System (ADS)

Nadel, M.; Feinberg, J. M.; Waters, M.

2012-12-01

The cause/s of the onset of the Younger Dryas (YD) climactic event at 12.9 ka and the corresponding extinction of Pleistocene megafauna and drastic changes in human subsistence patterns in the Americas remain a geologic mystery. Firestone et. al. (2007) proposed a bolide impact on the Laurentide ice sheet to explain these dramatic environmental changes, citing as evidence an increase in the concentration of magnetic spherules (MSp) and magnetic grains, among several other parameters. Over the five and a half years since the idea was first proposed it has evolved and matured, and many of the original lines of evidence are no longer argued. However, peaks in MSp concentrations (along with the presence of nanodiamonds) continue to be central to pro-impact arguments. Soils and lacustrine sediments are the most common recording media across the YD time interval, and the sample procedure used by previous workers to isolate the magnetic component is noteworthy. Disaggregated sediment was suspended in water and a plastic-covered hand magnet was used to stir the suspension and attract magnetic grains. Adhered grains were transferred into a separate container, and the process was repeated until grains were no longer attracted to the magnet. The total magnetic fraction was weighed and MSp were hand-picked under a microscope, to quantify concentration. Here we present an alternative approach that uses a comprehensive suite of highly sensitive rock magnetic measurements on in-situ samples to examine two early human archaeological sites: the Debra L. Friedkin site in central Texas and the Topper site in South Carolina (one of the original sites in the Firestone et al. (2007) study). The depositional history at both sites is constrained by optically stimulated luminescence ages, and the stratigraphic position of the 12.9 ka YD event is non-controversial. Two continuous soil profiles were collected at Friedkin, using 9 cm3 plastic boxes as well as a separate 20 cm U-channel core

Spatiotemporal Patterns of Hydrological Changes During the Younger Dryas Onset from Decadally-Resolved Lacustrine Biomarker Records: a W-E European Transect

NASA Astrophysics Data System (ADS)

Collins, J.; Aichner, B.; Engels, S.; Lane, C.; Maas, D.; Neugebauer, I.; Ott, F.; Slowinski, M. M.; Wulf, S.; Plessen, B.; Brauer, A.; Sachse, D.

2016-12-01

Future projections of European hydroclimate change remain uncertain, highlighting the need for an improved understanding of past abrupt European hydroclimate change, particularly in terms of identifying vulnerable regions. However, most existing continental paleohydrological records are not of sufficiently high resolution and/or sufficiently well dated for the assessment of leads and lags across the European continent and with the Greenland ice cores. To better understand mechanisms and feedbacks of hydrological changes during the last major abrupt climate change, the Younger Dryas (YD) cold period, we measured biomarker hydrogen isotopes (δD values) from terrestrial and aquatic sources on four high-resolution lacustrine sediment profiles. The sites span a 900km W-E transect from western Germany to eastern Poland and include: Meerfelder Maar, western Germany [MFM]; Hämelsee, northern-central Germany [HÄM]; Rehwiese, eastern Germany [RW]; Trzechowskie, central Poland [TRZ]. These sediments are annually laminated and contain common tephra layers, permitting a direct comparison of each site and allowing the identification of leads and lags in the response of the hydrological cycle to YD cooling on decadal timescales. We observed a decrease in biomarker δD values, likely reflecting cooling, that coincided with the onset of Greenland Stadial 1 in the NGRIP ice core at 12,846 years BP in the western European sites, with a progressive lag of several decades in the more easterly sites. Furthermore, we observed that the onset of aridification at all four sites occurred later but at roughly at the same time, coinciding with the biostratigraphically-defined onset of the YD at 12,679. A decrease in the magnitude of changes in biomarker δD values and aridification from W to E suggests a less strong aridification in eastern Europe. Our results suggest that hydrological changes at the onset of the YD were not uniform and were strongest and most abrupt in western Europe

Ziwundaschg - 10Be dating an Older Dryas cirque glacier moraine in the middle of the Eastern Alps

NASA Astrophysics Data System (ADS)

Moran, Andrew; Ivy-Ochs, Susan; Kerschner, Hanns

2017-04-01

Alpine glacier extents during the Oldest Dryas period (>14.7 ka) are still largely unknown. Moraines from that period are comparatively rare and usually attributed to the "Gschnitz Stadial", which marks the alpine glacier reaction to the first part of Heinrich event 1. In many valleys, in the absence of clear geomorphological evidence, estimates for the glacier extent during that period range between large dendritic valley glacier systems with a well defined, albeit unknown glacier end on the one hand and numerous local valley and cirque glaciers on the other hand. In this context well dated local glacier extents may play an important role, as they provide boundary conditions for the altitude of the equilibrium line (an important palaeoclimatic parameter) and thus limit possible speculations about glacier extents in their vicinity. "Ziwundaschg" is the place name for a cirque in the western Ötztal Mountains near the upper Inn valley and Reschenpass. It is situated more or less in the centre of the Eastern Alps. The cirque floor is at an altitude of about 2000 m and the highest mountains in the back of the cirque are around 2750 m. They were not glacierized during the Little Ice Age, and even a glacierization during the Younger Dryas cold phase was likely limited to a few small ice patches. Further down at the cirque floor, a beautifully developed end moraine with lateral moraines is preserved. 10Be ages from boulders on the moraine cluster around the transition from the Oldest Dryas to the Bølling Interstadial, suggesting moraine stabilization due to the rapid warming at that time. The ELA of the glacier was at about 2200 m a.s.l., roughly 600 - 650 m lower than during the LIA. This value can be taken as representative for the mountain ranges in its vicinity and can form the basis for estimates of glacier extent during the early Lateglacial period in the central Eastern Alps.

Reconstructing Younger Dryas plateau icefields in the Tweedsmuir Hills, Southern Uplands, Scotland: Style, dynamics and palaeo-climatic implications

NASA Astrophysics Data System (ADS)

Pearce, Danni; Rea, Brice; Bradwell, Tom; Barr, Iestyn; Small, David; McDougall, Des

2014-05-01

In Britain, the glacial geomorphological record has been widely utilised to infer palaeo-glacier geometries and ice dynamics, with much of this work focusing on the Scottish Highlands during the Last Glacial Interglacial Transition (LGIT), in particular the Younger Dryas (YD; c. 12.9 - 11.7 ka BP). The Southern Uplands represents the largest upland area south of the Highlands but has received limited research attention over the last century. The Tweedsmuir Hills are located in the central Southern Uplands, which form an area of dissected plateau approximately 320 km2. Early research in the 1800s identified moraines thought to be associated with the YD. However, the majority of previous work has focussed on isolated valleys and ignored the potential for plateau icefield glaciation, which has significant implications for the understanding of ice dynamics and geometries. Recent numerical modelling experiments covering the period 38 - 10.4 ka BP (Hubbard et al., 2008 cf. E109B8 and E102b2) have predicted a significant body of ice for the Southern Uplands at the onset of and throughout the YD, which cannot be verified at present due to a lack of empirical data. This research aims to provide the first systematic geomorphological mapping and Lateglacial climate reconstruction for the Tweedsmuir Hills. The results of air-photo interpretation and field mapping, which utilised a morphostratigraphic approach, have demonstrated a more extensive glaciation than previously mapped, reflecting more closely the Hubbard et al. (2009) modelled extent than earlier research. This consists of two separate icefields over the southern and northern Tweedsmuir Hills covering an area c. 45 km2 and 25 km2 respectively with Equilibrium Line Altitudes (ELAs) calculated to have ranged from c.419 m to 634 m. For both icefields ELAs of individual outlets reflect topographic controls rather than steep precipitation gradients similar to those derived for other icefields in Scotland (e.g., the

Surface-exposure ages of Front Range moraines that may have formed during the Younger Dryas, 8.2 cal ka, and Little Ice Age events

USGS Publications Warehouse

Benson, L.; Madole, R.; Kubik, P.; McDonald, R.

2007-01-01

Surface-exposure (10Be) ages have been obtained on boulders from three post-Pinedale end-moraine complexes in the Front Range, Colorado. Boulder rounding appears related to the cirque-to-moraine transport distance at each site with subrounded boulders being typical of the 2-km-long Chicago Lakes Glacier, subangular boulders being typical of the 1-km-long Butler Gulch Glacier, and angular boulders being typical of the few-hundred-m-long Isabelle Glacier. Surface-exposure ages of angular boulders from the Isabelle Glacier moraine, which formed during the Little Ice Age (LIA) according to previous lichenometric dating, indicate cosmogenic inheritance values ranging from 0 to ???3.0 10Be ka.11Surface-exposure ages in this paper are labeled 10Be; radiocarbon ages are labeled 14C ka, calendar and calibrated radiocarbon ages are labeled cal ka, and layer-based ice-core ages are labeled ka. 14C ages, calibrated 14C ages, and ice core ages are given relative to AD 1950, whereas 10Be ages are given relative to the sampling date. Radiocarbon ages were calibrated using CALIB 5.01 and the INTCAL04 data base Stuiver et al. (2005). Ages estimated using CALIB 5.01 are shown in terms of their 1-sigma range. Subangular boulders from the Butler Gulch end moraine yielded surface-exposure ages ranging from 5 to 10.2 10Be ka. We suggest that this moraine was deposited during the 8.2 cal ka event, which has been associated with outburst floods from Lake Agassiz and Lake Ojibway, and that the large age range associated with the Butler Gulch end moraine is caused by cosmogenic shielding of and(or) spalling from boulders that have ages in the younger part of the range and by cosmogenic inheritance in boulders that have ages in the older part of the range. The surface-exposure ages of eight of nine subrounded boulders from the Chicago Lakes area fall within the 13.0-11.7 10Be ka age range, and appear to have been deposited during the Younger Dryas interval. The general lack of inheritance in

Late-Glacial to Early Holocene Climate Changes from a Central Appalachians Pollen and Macrofossil Record

NASA Technical Reports Server (NTRS)

Kneller, Margaret; Peteet, Dorothy

1997-01-01

A Late-glacial to early Holocene record of pollen, plant macrofossils and charcoal, based on two cores, is presented for Browns Pond in the central Appalachians of Virginia. An AMS radiocarbon chronology defines the timing of moist and cold excursions, superimposed upon the overall warming trend from 14,200 to 7,500 C-14 yr B.P. This site shows cold, moist conditions from approximately 14,200 to 12,700 C-14 yr B.P., with warming at 12,730, 11,280 and 10,050 C-14 yr B.P. A decrease in deciduous broad-leaved tree taxa and Pinus strobus (haploxylon) pollen, simultaneous with a re-expansion of Abies denotes a brief, cold reversal from 12,260 to 12,200 C-14 yr B.P. A second cold reversal, inferred from increases in montane conifers, is centered at 7,500 C-14 yr B.P. The cold reversals at Browns Pond may be synchronous with climate change in Greenland, and northwestern Europe. Warming at 11,280 C-14 yr B.P. shows the complexity of regional climate responses during the Younger Dryas chronozone.

Evidence for insolation and Pacific forcing of late glacial through Holocene climate in the Central Mojave Desert (Silver Lake, CA)

NASA Astrophysics Data System (ADS)

Kirby, Matthew E.; Knell, Edward J.; Anderson, William T.; Lachniet, Matthew S.; Palermo, Jennifer; Eeg, Holly; Lucero, Ricardo; Murrieta, Rosa; Arevalo, Andrea; Silveira, Emily; Hiner, Christine A.

2015-09-01

Silver Lake is the modern terminal playa of the Mojave River in southern California (USA). As a result, it is well located to record both influences from the winter precipitation dominated San Bernardino Mountains - the source of the Mojave River - and from the late summer to early fall North American monsoon at Silver Lake. Here, we present various physical, chemical and biological data from a new radiocarbon-dated, 8.2 m sediment core taken from Silver Lake that spans modern through 14.8 cal ka BP. Texturally, the core varies between sandy clay, clayey sand, and sand-silt-clay, often with abrupt sedimentological transitions. These grain-size changes are used to divide the core into six lake status intervals over the past 14.8 cal ka BP. Notable intervals include a dry Younger Dryas chronozone, a wet early Holocene terminating 7.8 - 7.4 cal ka BP, a distinct mid-Holocene arid interval, and a late Holocene return to ephemeral lake conditions. A comparison to potential climatic forcings implicates a combination of changing summer - winter insolation and tropical and N Pacific sea-surface temperature dynamics as the primary drivers of Holocene climate in the central Mojave Desert.

Preliminary Cosmogenic Surface Exposure Ages on Laurentide Ice-sheet Retreat and Opening of the Eastern Lake Agassiz Outlets

NASA Astrophysics Data System (ADS)

Leydet, D.; Carlson, A. E.; Sinclair, G.; Teller, J. T.; Breckenridge, A. J.; Caffee, M. W.; Barth, A. M.

2015-12-01

The chronology for the eastern outlets of glacial Lake Agassiz holds important consequences for the cause of Younger Dryas cold event during the last deglaciation. Eastward routing of Lake Agassiz runoff was originally hypothesized to have triggered the Younger Dryas. However, currently the chronology of the eastern outlets is only constrained by minimum-limiting radiocarbon ages that could suggest the eastern outlets were still ice covered at the start of the Younger Dryas at ~12.9 ka BP, requiring a different forcing of this abrupt climate event. Nevertheless, the oldest radiocarbon ages are still consistent with an ice-free eastern outlet at the start of the Younger Dryas. Here we will present preliminary 10-Be cosmogenic surface exposure ages from the North Lake, Flat Rock Lake, glacial Lake Kaministiquia, and Lake Nipigon outlets located near Thunder Bay, Ontario. These ages will date the timing of the deglaciation of the Laurentide ice sheet in the eastern outlet region of glacial Lake Agassiz. This will provide an important constraint for the hypothesized freshwater forcing of the cause of Younger Dryas cold event.

Isotopic Evidence for C4 Grass Expansion During the Last Glacial Maximum and Younger Dryas in Northern Australia

NASA Astrophysics Data System (ADS)

Johnson, B. J.; Wakeham, S.; Gelinas, Y.; Luly, J.; Miller, G.

2004-12-01

In northern and central Australia, late Quaternary records of terrestrial environmental change are rare due to generally poor preservation of pollen grains and a derth of long-term, continuous lacustrine sedimentary deposits. The Wombe mound spring in the Keep River National Park, Northern Territory, is an organic mound and isolated patch of monsoon vine thicket thought to have formed tens of thousands of years ago. In an effort to obtain a record of paleovegetation and fire history from northern Australia, a 3.4 m sediment core was recovered from the Wombe mound spring and subject to multiple types of analyses. The core represents a continuous depositional sequence with radiocarbon ages spanning the last 35 ka cal years (hereafter referred to as 35 ka). Paleovegetation was reconstructed using a combination of pollen and carbon isotopes in bulk sediment and higher plant leaf wax (HPLW) lipid biomarkers. The fire history was reconstructed from paired graphitic black carbon (GBC) and polycyclic aromatic hydrocarbon (PAH) analyses of the core sediments. Between 35 and 11 ka, the bulk organic carbon (OC) isotope data fluctuate between -22 and -15%, with the most isotopically enriched values measured at 11.4 ka. Between 12.3 and 6.8 ka, OC isotope values decrease by 13%, and remain steady from 6.8 ka to the present at -28%. There are two distinct peaks of isotopic enrichment in the higher plant leaf wax biomarkers. These two peaks coincide with the Last Glacial Maximum (LGM; 21 ka) and the Younger Dryas (YD; 11.4 ka) and represent maximum increases in C4 grasses relative to C3 plants. Relative increases in C4 grasses during the LGM in other parts of the tropics (i.e., Sacred Lake, Mt. Kenya) have been attributed to the competitive advantage of C4 plants relative to C3 plants under reduced atmospheric pCO2 and is likely the cause for C4 expansion in northern Australia. The increase in C4 grasses during the YD is reflected in the bulk sediment and HPLW isotope data and is

Stable isotope (O and C) and pollen trends in eastern Lake Erie, evidence for a locally-induced climatic reversal of Younger Dryas age in the Great Lakes basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, C.F.M.; Anderson, T.W.

A cool period from about 11000 to 10500 BP (11 to 10.5 ka) is recognized in pollen records from the southern Great Lakes area by the return of Picea and Abies dominance and by the persistence of herbs. The area of cooling appears centred on the Upper Great Lakes. A high-resolution record (ca. 9 mm/y) from a borehole in eastern Lake Erie reveals, in the same time interval, this pollen anomaly, isotope evidence of melt-water presence (a-3 per mil shift in {delta} {sup 18}O and a + 1.1 per mil shift in {delta}{sup 13}C), increased sand, and reduced detrital calcitemore » content, all suggesting concurrent cooling of Lake Erie. The onset of cooling is mainly attributed to the effect of enhanced meltwater inflow on the relatively large upstream Main Lake Agassiz. Termination of the cooling coincides with drainage of Lake Algonquin, and is attributed to loss of its cooling effectiveness associated with a substantial reduction in its surface area. It is hypothesized that that the cold extra in-flow effectively prolonged the seasonal presence of lake ice and the period of spring overturn in Lake Algonquin. The deep mixing would have greatly increased the thermal conductive capacity of this extensive lake, causing suppression of summer surface lakewater temperatures and reduction of onshore growing-degree days. Alternatively, a rapid flow of meltwater, buoyed on sediment-charged (denser) lakewater, may have kept the lake surface cold in summer. Other factors such as wind-shifted pollen deposition and possible effects from the Younger Dryas North Atlantic cooling could have contributed to the Great Lakes climatic reversal, but further studies are needed to resolve their relative significance. 51 refs., 5 figs.« less

Radiocarbon dating and Dendrochronology for Statigraphic Units near Tebano, Senio Northern Apennines - Time frame of Climatic Fluctuation at the onset of the Younger Dryas

NASA Astrophysics Data System (ADS)

Eggenschwiler, Loren; Hajdas, Irka; Cherubini, Paolo; Picotti, Vincenzo; Saurer, Matthias

2017-04-01

The presence of Pinus [sylvestris] provides an insight into dramatic events due to climatic changes. Several major and minor climatic fluctuations have had a strong impact on terrestrial and marine environments since the last glacial period to present day (Ravazzi et al. 2006). This study aims to describe the response of a fluvial environment through the use of dendrochronology and stratigraphy. Here, we intend to get a better understanding of how these climatic fluctuations affect the behavior of the Senio River (Lotter et al. 1992). In Tebano, Italy, several Pinus sylvestris subfossil trunks were discovered during excavation for an irrigation pool. Subfossil samples were collected to analyze the climate during the Younger Dryas (11,000 years BP) in detail. Charcoal samples from the Bubano clay quarry extend our research to further to 35,500 cal. years BP. The combination of dendrochronology along with stratigraphy allowed us to examine the climate at a detailed local and apply it to a broader spectrum. Tree-ring measurements and cross dating provided a better understanding and verification of extreme events that occurred during the lifespans of the trees. The use of stable isotopes indicates the extreme conditions that occurred. Radiocarbon dating validates the age of the samples and what geological period they come from. Along with stratigraphy, we were able to compile depth data to create a sediment curve. Using various methods throughout this study, we discovered the climatic situation of Pinus 11,000 years BP and are able to compare them with samples from today. These present day samples mark two of the southernmost extents of the Pinus population. We were then able to comprehend the magnitude of sediment supply and precipitation. Through this collection of methods and data, we are able to understand the influence of climate change in the past and the potential changes of the future. REFERENCES Lotter, A. F.; Eicher, U.; Siegenthaler, U.; Birks, H. J. B

Deglacial palaeoclimate at Puerto del Hambre, subantarctic Patagonia, Chile

NASA Astrophysics Data System (ADS)

Heusser, Calvin J.; Heusser, Linda E.; Lowell, Thomas V.; Moreira M., Andrés; Moreira M., Simón

2000-02-01

The primary objective of this study is to further substantiate multistep climatic forcing of late-glacial vegetation in southern South America. A secondary objective is to establish the age of deglaciation in Estrecho de Magallanes-Bahía Inútil. Pollen assemblages at 2-cm intervals in a core of the mire at Puerto del Hambre (53°3621S, 70°5553W) provide the basis for reconstructing the vegetation and a detailed account of palaeoclimate in subantarctic Patagonia. Chronology over the 262-cm length of core is regulated by 20 AMS radiocarbon dates between 14 455 and 10 089 14C yr BP. Of 13 pollen assemblage zones, the earliest representing the Oldest Dryas chronozone (14 455-13 000 14C yr BP) records impoverished steppe with decreasing frequencies and loss of southern beech (Nothofagus). Successive 100-yr-long episodes of grass/herbs and of heath (Empetrum/Ericaceae) before 14 000 14C yr BP infer deglacial successional communities under a climate of increased continentality prior to the establishment of grass-dominated steppe. The Bølling-Allerød (13 000-11 000 14C yr BP) is characterised by mesic grassland under moderating climate that with abrupt change to heath dominance after 12 000 14C yr BP was warmer and not as humid. At the time of the Younger Dryas (11 000-10 000 14C yr BP), grass steppe expanded with a return of colder, more humid climate. Later, with gradual warming, communities were invaded by southern beech. The Puerto del Hambre record parallels multistep, deglacial palaeoclimatic sequences reported elsewhere in the Southern Andes and at Taylor Dome in Antarctica. Deglaciation of Estrecho de Magallanes-Bahía Inútil is dated close to 14 455 14C yr BP, invalidating earlier dates of between 15 800 and 16 590 14C yr BP.

Present day and Allerod - Younger Dryas marine 14C reservoir ages of surface waters in the North Atlantic-Norwegian Sea

NASA Astrophysics Data System (ADS)

Mangerud, J.; Bondevik, S.; Gulliksen, S.; Birks, H. H.; Reimer, P.; Hufthammer, A. K.; Hoisaeter, T.

2005-12-01

In order to compare radiocarbon dates on marine and terrestrial samples, the former have to be corrected for a marine reservoir age. We have calculated present day reservoir ages in this area by dating 22 whales collected AD 1860-1901 and 23 molluscs collected AD 1857-1926. Whales feed on pelagic organisms and will provide the reservoir age for the open ocean surface water. However, they travel large distances and integrate the reservoir ages of water masses along their way. Molluscs are stationary and monitor the sea water passing their living site. For the surface water in the N-Atlantic and Norwegian Sea we recommend to use the mean obtained for the two sets, i.e. reservoir ages of 400 +/- 40 and 375 +/- 30 years relative to tree rings of Intcal04 and British oak respectively, for the parts of the Holocene where specific time-dependent reservoir ages are not determined. The reservoir ages relative to British oak best reflects regional processes and we therefore prefer those, whereas IntCal04 ages are much more precisely determined, but dominated by trees from NW-USA in this time period. The reservoir ages for Allerod-Younger Dryas (YD) are obtained by dating parallel samples of terrestrial plant fragments and marine shells from sediment cores from the outermost western coast of Norway. The marine mud contains both plant fragments blown or washed in from adjacent land and in situ marine shells. In the earliest period (13,800-14,500 cal yrs BP) the reservoir age is 300-400 years, similar to present day values. This suggests that the exchange of CO2 between the atmosphere and the surface ocean was comparable to the present. During a short interval 13,200-13,500 cal yrs BP we found higher reservoir ages of 500-600 years coinciding with lower organic carbon content in our cores, and an inter-Allerod fluctuation seen in marine records. During the early YD the reservoir ages increased gradually from 400 to 650 years, causing a 700-14C year-long plateau, centred at 11

Chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12,800 years ago

NASA Astrophysics Data System (ADS)

Meltzer, David J.; Holliday, Vance T.; Cannon, Michael D.; Miller, D. Shane

2014-05-01

According to the Younger Dryas Impact Hypothesis (YDIH), ∼12,800 calendar years before present, North America experienced an extraterrestrial impact that triggered the Younger Dryas and devastated human populations and biotic communities on this continent and elsewhere. This supposed event is reportedly marked by multiple impact indicators, but critics have challenged this evidence, and considerable controversy now surrounds the YDIH. Proponents of the YDIH state that a key test of the hypothesis is whether those indicators are isochronous and securely dated to the Younger Dryas onset. They are not. We have examined the age basis of the supposed Younger Dryas boundary layer at the 29 sites and regions in North and South America, Europe, and the Middle East in which proponents report its occurrence. Several of the sites lack any age control, others have radiometric ages that are chronologically irrelevant, nearly a dozen have ages inferred by statistically and chronologically flawed age-depth interpolations, and in several the ages directly on the supposed impact layer are older or younger than ∼12,800 calendar years ago. Only 3 of the 29 sites fall within the temporal window of the YD onset as defined by YDIH proponents. The YDIH fails the critical chronological test of an isochronous event at the YD onset, which, coupled with the many published concerns about the extraterrestrial origin of the purported impact markers, renders the YDIH unsupported. There is no reason or compelling evidence to accept the claim that a cosmic impact occurred ∼12,800 y ago and caused the Younger Dryas.

Root tensile strength assessment of Dryas octopetala L. and implications for its engineering mechanism on lateral moraine slopes (Turtmann Valley, Switzerland)

NASA Astrophysics Data System (ADS)

Eibisch, Katharina; Eichel, Jana; Dikau, Richard

2015-04-01

Geomorphic processes and properties are influenced by vegetation. It has been shown that vegetation cover intercepts precipitation, enhances surface detention and storage, traps sediment and provides additional surface roughness. Plant roots impact the soil in a mechanical and hydrological manner and affect shear strength, infiltration capacity and moisture content. Simultaneously, geomorphic processes disturb the vegetation development. This strong coupling of the geomorphic and ecologic system is investigated in Biogeomorphology. Lateral moraine slopes are characterized by a variety of geomorphic processes, e. g. sheet wash, solifluction and linear erosion. However, some plant species, termed engineer species, possess specific functional traits which allow them to grow under these conditions and also enable them to influence the frequency, magnitude and even nature of geomorphic processes. For lateral moraine slopes, Dryas octopetala L., an alpine dwarf shrub, was identified as a potential engineer species. The engineering mechanism of D. octopetala, based on its morphological (e.g., growth form) and biomechanical (e.g., root strength) traits, yet remains unclear and only little research has been conducted on alpine plant species. The objectives of this study are to fill this gap by (A) quantifying D. octopetala root tensile strength as an important trait considering anchorage in and stabilization of the slope and (B) linking plant traits to the geomorphic process they influence on lateral moraine slopes. D. octopetala traits were studied on a lateral moraine slope in Turtmann glacier forefield, Switzerland. (A) Root strength of single root threads of Dryas octopetala L. were tested using the spring scale method (Schmidt et al., 2001; Hales et al., 2013). Measurement equipment was modified to enable field measurements of roots shortly after excavation. Tensile strength of individual root threads was calculated and statistically analyzed. First results show that

Late glacial and Early Holocene climatic conditions along the margin of the Greenland Ice Sheet, registered by glacial extents in Milne Land, east Greenland

NASA Astrophysics Data System (ADS)

Levy, L.; Kelly, M. A.; Lowell, T. V.

2010-12-01

Determining the mechanisms that caused past abrupt climate changes is important for understanding today’s rapidly warming climate and, in particular, whether we may be faced with abrupt climate change in the future. Scientists, policy makers and the public are concerned about ongoing warming because it is sending our climate into unprecedented territory at a rapid pace. The Younger Dryas cold event (~12,850-11,650 cal yr B.P.) was an abrupt climate event that occurred during the last transition from glacial to interglacial conditions. Due to its abrupt nature and the magnitude of temperature change that occurred, the Younger Dryas has been the focus of extensive research, however, the mechanisms that caused this cold event are still not well understood. Wide belts (up to 5 km) of moraines, known as the Milne Land stade moraines, are present in the Scoresby Sund region of central east Greenland. Previous work in the region using a combination of equilibrium line altitudes, surface exposure dating of moraines, and relative sea level changes indicates that mountain glacier advances during Younger Dryas time represent only moderate summer temperature cooling (~3-4C colder than at present). In contrast, Greenland ice cores, which register mean annual temperatures, indicate that Younger Dryas temperatures over the ice sheet were ~15C colder than at present. This mismatch between the two nearby paleoclimate records is interpreted to result from strong seasonality (very cold winters and only moderately cold summers) during Younger Dryas time. We are examining seasonality during Younger Dryas time by developing records of summer temperatures from local glaciers in Milne Land (71.0°N, 25.6°W). These mountain glaciers are located adjacent to the Greenland Ice Sheet, less than 50 km from the location of Renland Ice core and only ~250 km from the locations of the GISP2 and GRIP cores. We present new 10Be ages of local glacial extents in Milne Land. Ages range from 11,880 yr

A cosmogenic nuclide chronology of the last glacial transition in North-West Nelson, New Zealand-new insights in Southern Hemisphere climate forcing during the last deglaciation [rapid communication

NASA Astrophysics Data System (ADS)

Shulmeister, James; Fink, David; Augustinus, Paul C.

2005-05-01

We present a new glacial chronology for the last glacial interglacial transition, c. 20 to 10 ka, from the Cobb Valley, NW Nelson, New Zealand, based on a suite of 10Be and 26Al cosmogenic exposure ages. This chronology describes one of the most comprehensive deglaciation sequences from a late Quaternary valley system in the Southern Hemisphere. We chronicle the decay from the last (local) glacial maximum as follows: onset of the last deglaciation that commenced no earlier than 18-19 ka, followed by numerous short-term still-stands and/or minor re-advances over the ensuing 3-4 kyr, and complete evacuation of ice by 14 ka. We find no evidence to indicate a late glacial re-advance commensurate with the Northern Hemisphere Younger Dryas chronozone. The absence of a major glacial re-advance in this valley during the latter stages of the last glacial interglacial transition (LGIT) precludes a thermal decline in excess of about 3 °C and suggests no decline. The absence of late LGIT re-advances in the mountains of North-West Nelson, while deglacial readvances occurred in the main ranges of the Southern Alps can be best explained if westerly wind forcing rather than large-scale thermal decline is the primary control on glacier fluctuations, at least during the deglaciation. These findings challenge models of global climate change predicated on synchrony of millennial-scale glacial transitions due to thermal changes between Northern and Southern Hemispheres.

High resolution shallow geologic characterization of a late Pleistocene eolian environment using ground penetrating radar and optically stimulated luminescence techniques: North Carolina, USA

USGS Publications Warehouse

Mallinson, D.; Mahan, S.; Moore, Christine

2008-01-01

Geophysical surveys, sedimentology, and optically-stimulated luminescence age analyses were used to assess the geologic development of a coastal system near Swansboro, NC. This area is a significant Woodland Period Native American habitation and is designated the "Broad Reach" archaeological site. 2-d and 3-d subsurface geophysical surveys were performed using a ground penetrating radar system to define the stratigraphic framework and depositional facies. Sediment samples were collected and analyzed for grain-size to determine depositional environments. Samples were acquired and analyzed using optically stimulated luminescence techniques to derive the depositional age of the various features. The data support a low eolian to shallow subtidal coastal depositional setting for this area. Li-DAR data reveal ridge and swale topography, most likely related to beach ridges, and eolian features including low-relief, low-angle transverse and parabolic dunes, blowouts, and a low-relief eolian sand sheet. Geophysical data reveal dominantly seaward dipping units, and low-angle mounded features. Sedimentological data reveal mostly moderately-well to well-sorted fine-grained symmetrical to coarse skewed sands, suggesting initial aqueous transport and deposition, followed by eolian reworking and bioturbation. OSL data indicate initial coastal deposition prior to ca. 45,000 yBP, followed by eolian reworking and low dune stabilization at ca. 13,000 to 11,500 yBP, and again at ca. 10,000 yBP (during, and slightly after the Younger Dryas chronozone).

Northern peatland initiation lagged abrupt increases in deglacial atmospheric CH4

PubMed Central

Reyes, Alberto V.; Cooke, Colin A.

2011-01-01

Peatlands are a key component of the global carbon cycle. Chronologies of peatland initiation are typically based on compiled basal peat radiocarbon (14C) dates and frequency histograms of binned calibrated age ranges. However, such compilations are problematic because poor quality 14C dates are commonly included and because frequency histograms of binned age ranges introduce chronological artefacts that bias the record of peatland initiation. Using a published compilation of 274 basal 14C dates from Alaska as a case study, we show that nearly half the 14C dates are inappropriate for reconstructing peatland initiation, and that the temporal structure of peatland initiation is sensitive to sampling biases and treatment of calibrated 14C dates. We present revised chronologies of peatland initiation for Alaska and the circumpolar Arctic based on summed probability distributions of calibrated 14C dates. These revised chronologies reveal that northern peatland initiation lagged abrupt increases in atmospheric CH4 concentration at the start of the Bølling–Allerød interstadial (Termination 1A) and the end of the Younger Dryas chronozone (Termination 1B), suggesting that northern peatlands were not the primary drivers of the rapid increases in atmospheric CH4. Our results demonstrate that subtle methodological changes in the synthesis of basal 14C ages lead to substantially different interpretations of temporal trends in peatland initiation, with direct implications for the role of peatlands in the global carbon cycle. PMID:21368146

Northern peatland initiation lagged abrupt increases in deglacial atmospheric CH4.

PubMed

Reyes, Alberto V; Cooke, Colin A

2011-03-22

Peatlands are a key component of the global carbon cycle. Chronologies of peatland initiation are typically based on compiled basal peat radiocarbon (14C) dates and frequency histograms of binned calibrated age ranges. However, such compilations are problematic because poor quality 14C dates are commonly included and because frequency histograms of binned age ranges introduce chronological artefacts that bias the record of peatland initiation. Using a published compilation of 274 basal 14C dates from Alaska as a case study, we show that nearly half the 14C dates are inappropriate for reconstructing peatland initiation, and that the temporal structure of peatland initiation is sensitive to sampling biases and treatment of calibrated 14C dates. We present revised chronologies of peatland initiation for Alaska and the circumpolar Arctic based on summed probability distributions of calibrated 14C dates. These revised chronologies reveal that northern peatland initiation lagged abrupt increases in atmospheric CH4 concentration at the start of the Bølling-Allerød interstadial (Termination 1A) and the end of the Younger Dryas chronozone (Termination 1B), suggesting that northern peatlands were not the primary drivers of the rapid increases in atmospheric CH4. Our results demonstrate that subtle methodological changes in the synthesis of basal 14C ages lead to substantially different interpretations of temporal trends in peatland initiation, with direct implications for the role of peatlands in the global carbon cycle.

Late Quaternary dynamics of forest vegetation on northern Vancouver Island, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Lacourse, Terri

2005-01-01

Pollen analysis of radiocarbon-dated lake sediment from northern Vancouver Island, southwest British Columbia reveals regional changes in forest vegetation over the last 12,200 14C yr (14,900 cal yr). Between at least 12,200 and 11,700 14C yr BP (14,900-13,930 cal yr BP), open woodlands were dominated by Pinus contorta, Alnus crispa, and various ferns. As P. contorta decreased in abundance, Alnus rubra and more shade-tolerant conifers (i.e., Picea and Tsuga mertensiana) increased. Increases in T. mertensiana, P. contorta, and A. crispa pollen accumulation rates (PARs) between 10,600 and 10,400 14C yr BP (11,660-11,480 cal yr BP) reflect a cool and moist climate during the Younger Dryas chronozone. Orbitally induced warming around 10,000 14C yr BP (11,090 cal yr BP) allowed the northward extension of Pseudotsuga menziesii, although Picea, Tsuga heterophylla, and A. rubra dominated early Holocene forests. By 7500 14C yr BP (8215 cal yr BP), shade-tolerant T. heterophylla was the dominant forest tree. Cupressaceae ( Thuja plicata and Chamaecyparis nootkatensis) was present by 7500 14C yr BP but reached its maximum after 3500 14C yr BP (3600 cal yr BP), when a cooler and wetter regional climate facilitated the development of temperate rainforest. The highest rates of vegetation change are associated with Lateglacial climate change and species with rapid growth rates and short life spans.

A major advance of tropical Andean glaciers during the Antarctic cold reversal.

PubMed

Jomelli, V; Favier, V; Vuille, M; Braucher, R; Martin, L; Blard, P-H; Colose, C; Brunstein, D; He, F; Khodri, M; Bourlès, D L; Leanni, L; Rinterknecht, V; Grancher, D; Francou, B; Ceballos, J L; Fonseca, H; Liu, Z; Otto-Bliesner, B L

2014-09-11

The Younger Dryas stadial, a cold event spanning 12,800 to 11,500 years ago, during the last deglaciation, is thought to coincide with the last major glacial re-advance in the tropical Andes. This interpretation relies mainly on cosmic-ray exposure dating of glacial deposits. Recent studies, however, have established new production rates for cosmogenic (10)Be and (3)He, which make it necessary to update all chronologies in this region and revise our understanding of cryospheric responses to climate variability. Here we present a new (10)Be moraine chronology in Colombia showing that glaciers in the northern tropical Andes expanded to a larger extent during the Antarctic cold reversal (14,500 to 12,900 years ago) than during the Younger Dryas. On the basis of a homogenized chronology of all (10)Be and (3)He moraine ages across the tropical Andes, we show that this behaviour was common to the northern and southern tropical Andes. Transient simulations with a coupled global climate model suggest that the common glacier behaviour was the result of Atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration. During the Antarctic cold reversal, glaciers advanced primarily in response to cold sea surface temperatures over much of the Southern Hemisphere. During the Younger Dryas, however, northern tropical Andes glaciers retreated owing to abrupt regional warming in response to reduced precipitation and land-surface feedbacks triggered by a weakened Atlantic meridional overturning circulation. Conversely, glacier retreat during the Younger Dryas in the southern tropical Andes occurred as a result of progressive warming, probably influenced by an increase in atmospheric carbon dioxide. Considered with evidence from mid-latitude Andean glaciers, our results argue for a common glacier response to cold conditions in the Antarctic cold reversal exceeding that of the Younger Dryas.

Evaluating Pyemotes dryas (Vitzthum 1923)(Acari: Pyemotidae) as a parasite of the southern pine beetle

Treesearch

John C. Moser; B. Kielczewski; J. Wisniewski; S. Balazy

1978-01-01

Populations of Pyemotes dryas (Vitzthum 1923) from Poland were bioassayed for potential use in the biological control of the southern pine beetle in the United States. The mite apparently rides and attacks a wide range of European bark beetles that attack conifers and readily consumes brood of the southern pine beetle. However, it is not phoretic on...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stephan Harrison; Ann V. Rowan; Neil F. Glasser

It is widely believed that the last glaciers in the British Isles disappeared at the end of the Younger Dryas stadial (12.9–11.7 cal. kyr BP). Here, we use a glacier–climate model driven by data from local weather stations to show for the first time that glaciers developed during the Little Ice Age (LIA) in the Cairngorm Mountains. Our model is forced from contemporary conditions by a realistic difference in mean annual air temperature of -1.5 degrees C and an increase in annual precipitation of 10%, and confirmed by sensitivity analyses. These results are supported by the presence of small bouldermore » moraines well within Younger Dryas ice limits, and by a dating programme on a moraine in one cirque. As a result, we argue that the last glaciers in the Cairngorm Mountains (and perhaps elsewhere in upland Britain) existed in the LIA within the last few hundred years, rather than during the Younger Dryas.« less

Beringian Megafaunal Extinctions at ~37 ka B.P.: Do Micrometeorites Embedded in Fossil Tusks and Skulls Indicate an Extraterrestial Precursor to the Younger Dryas Event?

NASA Astrophysics Data System (ADS)

Hagstrum, J. T.; Firestone, R. B.; West, A.

2009-12-01

Studies of Late Pleistocene megafaunal fossils and their ancient DNA from Beringia (eastern Siberia, Alaska, and the emerged Bering Strait) indicate sharp declines in steppe bison population diversity and horse body size, extinction of the Alaskan wild ass, and local extinctions of brown bear and woolly mammoth genetic lines beginning at about 37 ka B.P. Beringia is also well known for its remarkably preserved Late Pleistocene frozen animal mummies. 14C ages of these mummies are bimodally distributed, having peaks coincident with the earlier ~37 ka B.P., and ~13 ka B.P. Younger Dryas, onset extinction events. Associated with the ~37 ka B.P. event are, for example, the Berezovka mammoth, headless Selerikan horse, steppe bison “Blue Babe”, and baby mammoths “Dima” and “Lyuba”. Analyses of these and other mummies indicate that they died instantly, in mostly healthy condition, with gut contents and high fat reserves indicative of a late summer to autumn season. An assortment of uneaten limbs and other body parts from a variety of species have also been found. Uniformitarian death scenarios inadequately account for the lack of evidence of normal predation and scavenging. Extensive internal injuries (e.g. large bone fractures, hemorrhaging) and apparent rapid burial of the mummies also indicate that something truly unusual happened at the time of these extinction events. We have discovered what appear to be micrometeorites embedded in seven Alaskan mammoth tusks and a Siberian bison skull acquired from commercial sources. 14C ages for five of these fossils have a weighted mean age of 33 ± 2 ka B.P. Laser ablation ICP-MS and XRF analyses of the particles indicate high Fe contents with compositions enriched in Ni and depleted in Ti, similar to Fe meteorites and unlike any natural terrestrial sources. Microprobe analyses of a Fe-Ni sulfide grain from tusk 2 also show that it contains between 3 and 20 weight percent Ni. SEM images and XRF analyses of a bison

Changes in El Niño - Southern Oscillation (ENSO) conditions during the Greenland Stadial 1 (GS-1) chronozone revealed by New Zealand tree-rings

NASA Astrophysics Data System (ADS)

Palmer, Jonathan G.; Turney, Chris S. M.; Cook, Edward R.; Fenwick, Pavla; Thomas, Zoë; Helle, Gerhard; Jones, Richard; Clement, Amy; Hogg, Alan; Southon, John; Bronk Ramsey, Christopher; Staff, Richard; Muscheler, Raimund; Corrège, Thierry; Hua, Quan

2016-12-01

The warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in Greenland (Greenland Stadial 1 or GS-1) and Europe (Younger Dryas Stadial or YD). This reversal to glacial-like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remain uncertain. Whilst the wider Atlantic region has a network of high-resolution proxy records spanning GS-1, the Pacific Ocean suffers from a scarcity of sub-decadally resolved sequences. Here we report the results from an investigation into a tree-ring chronology from northern New Zealand aimed at addressing the paucity of data. The conifer tree species kauri (Agathis australis) is known from contemporary studies to be sensitive to regional climate changes. An analysis of a 'historic' 452-year kauri chronology confirms a tropical-Pacific teleconnection via the El Niño - Southern Oscillation (ENSO). We then focus our study on a 1010-year sub-fossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring-width downturn between ∼12,500 and 12,380 cal BP within GS-1. Wavelet analysis shows a marked increase in ENSO-like periodicities occurring after the downturn event. Comparison to low- and mid-latitude Pacific records suggests a coherency with ENSO and Southern Hemisphere atmospheric circulation change during this period. The driver(s) for this climate event remain unclear but may be related to solar changes that subsequently led to establishment and/or increased expression of ENSO across the mid-latitudes of the Pacific, seemingly independent of the Atlantic and polar regions.

Terrestrial sensitivity to abrupt cooling recorded by aeolian activity in northwest Ohio, USA

USGS Publications Warehouse

Campbell, M.C.; Fisher, T.G.; Goble, R.J.

2011-01-01

Optically stimulated luminescence dated sand dunes and Pleistocene beach ridges in northwest Ohio are used to reconstruct landscape modification more than 5000. yr after deglaciation. Four of the OSL ages (13.3-11.1. ka) cluster around the Younger Dryas cold event, five ages (10.8-8.2. ka) cluster around the Preboreal, one young age (0.9-0.7. ka) records more recent aeolian activity, and one age of 15.1-13.1. ka dates a barrier spit in Lake Warren. In northwest Ohio, both landscape instability recorded by aeolian activity and a vegetation response recorded by pollen are coeval with the Younger Dryas. However, the climate conditions during the Preboreal resulting in aeolian activity are not recorded in the available pollen records. From this, we conclude that aeolian dunes and surfaces susceptible to deflation are sensitive to cooler, drier episodes of climate and can complement pollen data. Younger Dryas and Preboreal aged aeolian activity in northwestern Ohio coincides with aeolian records elsewhere in the Great Lakes region east of the prairie-forest ecotone. ?? 2011 University of Washington.

Episodes of low dissolved oxygen indicated by ostracodes and sediment geochemistry at Crystal Lake, Illinois, USA

USGS Publications Warehouse

Curry, B. Brandon; Filippelli, G.M.

2010-01-01

Low dissolved oxygen during the summer and early fall controls profundal continental ostracode distribution in Crystal Lake (McHenry County), Illinois, favoring Cypria ophthalmica and Physocypria globula at water depths from 6 to 13 m. These species also thrived in the lake's profundal zone from 14,165 to 9600 calendar year before present (cal yr b.p.) during the late Boiling, Allerod, and Younger Dryas chronozones, and early Holocene. Characterized by sand, cemented tubules, large aquatic gastropod shells, and littoral ostracode valves, thin (1-6 cm) tempestite deposits punctuate thicker deposits of organic gyttja from 16,080 to 11,900 cal yr b.p. The succeeding 2300 yr (11,900-9600 cal yr b.p.) lack tempestites, and reconstructed water depths were at their maximum. Deposition of marl under relatively well-oxygenated conditions occurred during the remainder of the Holocene until the arrival of Europeans, when the lake returned to a pattern of seasonally low dissolved oxygen. Such conditions are also indicated in the lake sediment by the speciation of phosphorus, high concentrations of organic carbon, and abundant iron and manganese occluded to mineral grains. Initial low dissolved oxygen was probably caused by the delivery of dissolved P and Fe in shallow groundwater, the chemistry of which was influenced by Spodosol pedogenesis under a spruce forest. The triggering may have been regionally warm and wet conditions associated with retreat of the Lake Michigan lobe (south-central Laurentide Ice Sheet). ?? 2010, by the American Society of Limnology and Oceanography Inc.

Problems with the Younger Dryas Boundary (YDB) Impact Hypothesis

NASA Astrophysics Data System (ADS)

Boslough, M.

2009-12-01

One breakthrough of 20th-century Earth science was the recognition of impacts as an important geologic process. The most obvious result is a crater. There are more than 170 confirmed terrestrial impact structures with a non-uniform spatial distribution suggesting more to be found. Many have been erased by tectonics and erosion. Deep water impacts do not form craters, and craters in ice sheets disappear when the ice melts. There is growing speculation that such hidden impacts have caused frequent major environmental events of the Holocene, but this is inconsistent with the astronomically-constrained population of Earth-crossing asteroids. Impacts can have consequences much more significant than excavation of a crater. The K/T boundary mass extinction is attributed to the environmental effects of a major impact, and some researchers argue that other extinctions, abrupt climate changes, and even civilization collapses have resulted from impacts. Nuclear winter models suggest that 2-km diameter asteroids exceed a "global catastrophe threshold" by injecting sufficient dust into the stratosphere to cause short-term climate changes, but would not necessarily collapse most natural ecosystems or cause mass extinctions. Globally-catastrophic impacts recur on timescales of about one million years. The 1994 collision of Comet Shoemaker-Levy 9 with Jupiter led us recognize the significance of terrestrial airbursts caused by objects exploding violently in Earth’s atmosphere. We have invoked airbursts to explain rare forms of non-volcanic glasses and melts by using high-resolution computational models to improve our understanding of atmospheric explosions, and have suggested that multiple airbursts from fragmented impactors could be responsible for regional effects. Our models have been cited in support of the widely-publicized YDB impact hypothesis. Proponents claim that a broken comet exploded over North America, with some fragments cratering the Laurentide Ice Sheet. They suggest an abrupt climate change caused by impact-triggered meltwater forcing, along with massive wildfires, resulted in megafaunal extinctions and collapse of the Clovis culture. We argue that the physics of fragmentation, dispersion, and airburst is not consistent with the hypothesis; that observations are no more compatible with impact than with other causes; and that the probability of the scenario is effectively nil. Moreover, millennial-scale climate events are far more frequent than catastrophic impacts, and pose a much greater threat to humanity. Sandia is a multiprogram laboratory operated by Sandia Corp, a Lockheed Martin Company, for the US DOE under Contract DE-AC04-94AL85000. Probability density for largest asteroid impact since Last Glacial Maximum based on power-law size distribution. Comets are orders of magnitude less likely. Grazing trajectory or recent fragmentation further reduces probability.

Nearly synchronous climate change in the Northern Hemisphere during the last glacial termination

USGS Publications Warehouse

Benson, L.; Burdett, J.; Lund, S.; Kashgarian, Michaele; Mensing, S.

1997-01-01

The climate of the North Atlantic region underwent a series of abrupt cold/warm oscillations when the ice sheets of the Northern Hemisphere retreated during the last glacial termination (17.711.5 kyr ago). Evidence for these oscillations, which are recorded in European terrestrial sediments as the Oldest Dryas/Bolling/Older Dryas/Allerod/Younger Dryas vegetational sequence, has been found in Greenland ice cores. The geographical extent of many of these oscillations is not well known, but the last major cold event (the Younger Dryas) seems to have been global in extent. Here we present evidence of four major oscillations in the hydrological balance of the Owens basin, California, that occurred during the last glacial termination. Dry events in western North America occurred at approximately the same time as cold events recorded in Greenland ice, with transitions between climate regimes in the two regions taking place within a few hundred years of each other. Our observations thus support recent climate simulations which indicate that cooling of the North Atlantic Ocean results in cooling of the North Pacific Ocean which, in turn, leads to a drier climate in western North America.

Late Pleistocene Climate Events and The Origin of Agriculture In SW Asia

NASA Astrophysics Data System (ADS)

Rossignol-Strick, M.

In the Eastern Mediterranean sea, the climate succession of the last deglaciation is documented and dated in marine cores by the d18-O variation of foraminiferal cal- cite and pollen records. The Last Glacial Maximum is identified by a large abundance of grass pollen from a prairie-type vegetal cover with low annual precipitation in the mountainous north and east borderlands of the sea, where the pollen mainly origi- nates. During the first phase of the last deglaciation, the Bolling/Allerod chronozone, the moisture availability increases and makes possible the spread of a deciduous for- est, as shown by the increasing pollen abundance of the deciduous oak. The cold and arid Younger Dryas is identified by a reversal to semi-desert conditions, with the in- crease of sage-brush (Artemisia) and the saline-tolerant Chenopodiaceae. The climate of the earliest Holocene is Optimum for at least 3000 years (9000-6000yr BP), with the largest spread of the deciduous forest at low-middle elevations signalling wet sum- mers and of the Pistacia woodland at low elevations signalling mild, no-frost winters. This is the time when the most recent sapropel deposited in the eastern Mediterranean under anoxic bottom conditions generated by a surface lid of lower salinity due to the concomitant largest floods of the Nile River fed by the strongest African monsoon rains in the Ethiopian Highlands. In SW Asia, the pollen records of lakes and marshes have been correlated with those of the marine cores, thereby obtaining a robust time-frame. In that area, the archaeo- logical data of human settlements are independently dated by 14C. Thus the archaeo- logical succession can be securely set against the well-dated climatic succession. The Late Palaeolithic populations of SW Asia were wandering hunter-gatherers in the prairies of the Last Glacial Maximum, where they already collected wild wheat, barley and fruit. With the Bolling/Allerod wetter and warmer climate, they began to settle in

Cosmogenic Surface-Exposure Dating of Boulders on Last-Glacial and Late-Glacial Moraines, Lago Buenos Aires, Argentina: Interpretive Strategies and Paleoclimate Implications

NASA Astrophysics Data System (ADS)

Douglass, D. C.; Singer, B. S.; Kaplan, M. R.; Mickelson, D. M.; Caffee, M.

2005-12-01

The most substantial and least quantifiable source of uncertainty in cosmogenic surface-exposure datasets is the variable exposure histories of boulders from the same landform. The development of precise and accurate chronologies requires distinguishing boulders that best reflect the age of the landform from those which are outliers. We use the Mean Square of Weighted Deviates statistic and cumulative frequency plots to identify groups of samples that have statistically similar ages based on the number of samples and the uncertainty associated with the analyses. This group of samples most likely represents the best estimate of the landform age. We use these tools to interpret 49 surface-exposure ages from six last-glacial and late-glacial moraines at Lago Buenos Aires, Argentina (LBA; 71.0W, 46.5S). Seven of the orty-nine samples are identified as anomalously young, and are interpreted to have been exhumed after moraine deposition. The remaining samples indicate that glacial advances or still-stands of the ice margin occurred at 22.7±0.9, 21.4±1.9, 19.8±1.1, 17.0±0.8, 15.7±0.6, and 14.4±0.9 ka (±2 σ). This maximum ice extent is roughly synchronous with maximum global ice volume and several of the re-advances are contemporaneous with Heinrich events and other Northern Hemisphere cold periods. The late-glacial readvance at ca. 14.4 ka is contemporaneous with the Antarctic Cold Reversal (ACR), and precedes the Younger Dryas Chronozone (YD). No evidence for a Younger Dryas glacial advance has been found in the Lago Buenos Aires basin. This precise glacial chronology indicates there were significant and important differences in climate across southern South America. The timing of maximum ice extent and onset of deglaciation at LBA occur ~4000 years later than in the Chilean Lake District (41S). Fossil pollen from the CLD area indicates cooler conditions between ca. 14.2 and 11.2, and increased silt in a nearby lake core provides indirect evidence for glacial

Reconstruction of the Amazon Basin effective moisture availability over the past 14,000 years.

PubMed

Maslin, M A; Burns, S J

2000-12-22

Quantifying the moisture history of the Amazon Basin is essential for understanding the cause of rain forest diversity and its potential as a methane source. We reconstructed the Amazon River outflow history for the past 14,000 years to provide a moisture budget for the river drainage basin. The oxygen isotopic composition of planktonic foraminifera recovered from a marine sediment core in a region of Amazon River discharge shows that the Amazon Basin was extremely dry during the Younger Dryas, with the discharge reduced by at least 40% as compared with that of today. After the Younger Dryas, a meltwater-driven discharge event was followed by a steady increase in the Amazon Basin effective moisture throughout the Holocene.

AMS radiocarbon dating and varve chronology of Lake Soppensee: 6000 to 12000 14C years BP

NASA Astrophysics Data System (ADS)

Hajdas, Irena; Ivy, Susan D.; Beer, Jürg; Bonani, Georges; Imboden, Dieter; Lotted, André F.; Sturm, Michael; Suter, Martin

1993-12-01

For the extension of the radiocarbon calibration curve beyond 10000 14C y BP, laminated sediment from Lake Soppensee (central Switzerland) was dated. The radiocarbon time scale was obtained using accelerator mass spectrometry (AMS) dating of terrestrial macrofossils selected from the Soppensee sediment. Because of an unlaminated sediment section during the Younger Dryas (10000 11000 14C y BP), the absolute time scale, based on counting annual layers (varves), had to be corrected for missing varves. The Soppensee radiocarbon-verve chronology covers the time period from 6000 to 12000 14C y BP on the radiocarbon time scale and 7000 to 13000 calendar y BP on the absolute time scale. The good agreement with the tree ring curve in the interval from 7000 to 11450 cal y BP (cal y indicates calendar year) proves the annual character of the laminations. The ash layer of the Vasset/Killian Tephra (Massif Central, France) is dated at 8230±140 14C y BP and 9407±44 cal y BP. The boundaries of the Younger Dryas biozone are placed at 10986±69 cal y BP (Younger Dryas/Preboreal) and 1212±86 cal y BP (Alleröd/Younger Dryas) on the absolute time scale. The absolute age of the Laacher See Tephra layer, dated with the radiocarbon method at 10 800 to 11200 14C y BP, is estimated at 12350 ± 135 cal y BP. The oldest radiocarbon age of 14190±120 14C y BP was obtained on macrofossils of pioneer vegetation which were found in the lowermost part of the sediment profile. For the late Glacial, the offset between the radiocarbon (10000 12000 14C y BP) and the absolute time scale (11400 13000 cal y BP) in the Soppensee chronology is not greater than 1000 years, which differs from the trend of the U/Th-radiocarbon curve derived from corals.

Evidence from Central Mexico Supporting the Younger Dryas Extraterrestrial Impact Hypothesis

DTIC Science & Technology

2012-03-05

identified glassy spherules, CSps, high- temperature melt- rocks , shocked quartz, and a YDB black mat analogue in the Venezuelan Andes. Those authors...debate, we have examined a diverse assemblage of YDB markers at Lake Cuitzeo using a more comprehensive array of analytical techniques than in previous...accelerator mass spectroscopy (AMS) 14C dates on bulk sediment and used in a linear interpolation with the YD onset identified at approximately 2.8 m. To

Late Pleistocene and Early Holocene lake-level fluctuations in the Lahontan Basin, Nevada: Implications for the distribution of archaeological sites

USGS Publications Warehouse

Adams, K.D.; Goebel, Thomas; Graf, K.; Smith, G.M.; Camp, A.J.; Briggs, R.W.; Rhode, D.

2008-01-01

The Great Basin of the western U.S. contains a rich record of late Pleistocene and Holocene lake-level fluctuations as well as an extensive record of human occupation during the same time frame. We compare spatial-temporal relationships between these records in the Lahontan basin to consider whether lake-level fluctuations across the Pleistocene-Holocene transition controlled distribution of archaeological sites. We use the reasonably well-dated archaeological record from caves and rockshelters as well as results from new pedestrian surveys to investigate this problem. Although lake levels probably reached maximum elevations of about 1230-1235 m in the different subbasins of Lahontan during the Younger Dryas (YD) period, the duration that the lakes occupied the highest levels was brief Paleoindian and early Archaic archaeological sites are concentrated on somewhat lower and slightly younger shorelines (???1220-1225 in) that also date from the Younger Dryas period. This study suggests that Paleoindians often concentrated their activities adjacent to large lakes and wetland resources soon after they first entered the Great Basin. ?? 2008 Wiley Periodicals, Inc.

The Schmidt hammer as a relative-age dating tool and its potential for calibrated-age dating in Holocene glaciated environments

NASA Astrophysics Data System (ADS)

Shakesby, Richard A.; Matthews, John A.; Owen, Geraint

2006-11-01

The Schmidt hammer is a relatively cheap, portable, sturdy instrument with proven value over the last two decades or so in rapidly dating coarse inorganic deposits of diverse origins. Early views were that its dating role was limited to distinguishing recently exposed from much older. Typically, either a few sites of possibly different ages or occasional older surfaces amongst many young sites were studied. More recently, calibration curves based on individual R-value means from small numbers (2-4) of sites of known ages have been used to estimate the ages of undated sites. We present Schmidt hammer rebound ( R-) values from 28 'Little Ice Age' (and younger), 23 Preboreal and 7 Younger Dryas glaciated surfaces in southern Norway in order, first, to test rigorously the robustness of the instrument as a relative-age dating tool. Despite being obtained from different surfaces (moraines, glaciofluvial deposits and bedrock) and varied metamorphic lithologies, the R-value overall means and 95% confidence intervals for the 'Little Ice Age', Preboreal and Younger Dryas age categories (respectively, 60.0±1.6, 41.6±1.4 and 34.2±2.0) are statistically significantly different. Only two outlying sites in the two younger age categories have overlapping confidence intervals, demonstrating remarkable robustness in differentiating early- and late-Holocene surfaces. The distinction between Preboreal and Younger Dryas sites (with terminal dates <2000 years apart) is less clear but still statistically significant, though possibly partly because of enhanced weathering conditions at the predominantly well vegetated Younger Dryas sites. Second, we examine the feasibility and desirability of controlling non-age-related factors, including some previously considered critical (instrument wear, operator bias, initial rock surface texture), which emerge either as less important than previously argued or as relatively unimportant, together with others previously unreported (e.g. long

Lake ecosystem response to late Allerød climatic fluctuation (northern Poland)

NASA Astrophysics Data System (ADS)

Słowiński, Michał; Zawiska, Izabela; Ott, Florian; Noryśkiewicz, Agnieszka M.; Plessen, Birgit; Apolinarska, Karina; Lutyńska, Monika; Michczyńska, Danuta J.; Wulf, Sabine; Skubała, Piotr; Błaszkiewicz, Mirosław; Brauer, Achim

2014-05-01

The aim of this study is a better understanding, how local lake ecosystems responded to climate changes during the late Allerød - Younger Dryas transition. Therefore, we carried out a detailed high-resolution multi-proxy case study on the partly laminated sediments from the Trzechowskie palaeolake, located in the Pomeranian Lakeland, northern Poland (53°52'40"N, 18°12'93"E). We reconstructed the ecosystem response to climatic and environmental changes using biotic proxies (macrofossils, pollen, Cladocera, diatoms) and classical geochemical proxies (δ18O, δ13C, loss-on-ignition, CaCO3 content) in combination with high-resolution µ-XRF element core scanning. The core chronology has been established by biostratigraphy, AMS 14C-dating on plant macro remains, varve counting within the laminated intervals and the Laacher See Tephra (12880 varve yrs BP) as a precise isochrone. Framework of our investigation is a period covering 367 varve years of the late Allerød and the beginning of the Younger Dryas period where varve preservation gradually ceases. The pronounced changes at the late Allerød - Younger Dryas transition is well-reflected in all environmental indicators but with conspicuous leads and lags reflecting complex responses of lake ecosystems to climate variation. This study is a contribution to the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analysis) funded by the Helmholtz Association. The research was supported by the National Science Centre Poland (grants No. NN 306085037 and NCN 2011/01/B/ST10/07367).

Irrational ideas. Older vs. younger inpatients.

PubMed

Hyer, L A; Jacobsen, R; Harrison, W R

1985-04-01

The relationship to age of irrational beliefs among psychiatric inpatients has not been explored using the rational-emotive model. This study addressed the following two questions: 1) Do older and younger psychiatric inpatients differ in irrational beliefs? 2) Do older depressives differ from older nondepressives in irrational beliefs? Upon admission to a large medical center, 58 younger (less than 45 years old) and 54 older (greater than 55 years old) subjects were assessed on a battery of psychological tests, including the Idea Inventory and the Beck Depression Inventory. Results showed that older and younger inpatients did not differ on irrational beliefs. Results also showed that older and younger groups of depressives did not differ on the irrationality scores. When a correlational analysis was used, depression was related to irrationality within the older group but not within the younger group.

The role of the Asian winter monsoon in the rapid propagation of abrupt climate changes during the last deglaciation

NASA Astrophysics Data System (ADS)

Chu, Guoqiang; Sun, Qing; Zhu, Qingzeng; Shan, Yabing; Shang, Wenyu; Ling, Yuan; Su, Youliang; Xie, Manman; Wang, Xishen; Liu, Jiaqi

2017-12-01

High-resolution temperature records spanning the last deglaciation from low latitudes are scarce; however, they are important for understanding the rapid propagation of abrupt climate events throughout the Northern Hemisphere and the tropics. Here, we present a branched GDGTs-based temperature reconstruction from the sediments of Maar Lake Huguangyan in tropical China. The record reveals that the mean temperature during the Oldest Dryas was 17.8 °C, which was followed by a two-step increase of 2-3 °C to the Bølling-Allerød, a decrease to 19.8 °C during the Younger Dryas, and a rapid warming at the onset of the Holocene. The Oldest Dryas was about 2 °C warmer than the Younger Dryas. The reconstructed temperature was weighted towards the wintertime since the lake is monomictic and the mixing process in winter supplies nutrients from the lake bottom to the entire water column, greatly promoting biological productivity. In addition, the winter-biased temperature changes observed in the study are more distinctive than the summer-biased temperature records from extra-tropical regions of East Asia. This implies that the temperature decreases during abrupt climatic events were mainly a winter phenomenon. Within the limits of the dating uncertainties, the broadly similar pattern of winter-weighted temperature change observed in both tropical Lake Huguangyan and in Greenland ice cores indicates the occurrence of tightly-coupled interactions between high latitude ice sheets and land areas in the tropics. We suggest that the winter monsoon (especially cold surges) could play an important role in the rapid transmission of the temperature signal from the Arctic to the tropics.

Older and Younger Adults’ Accuracy in Discerning Health and Competence in Older and Younger Faces

PubMed Central

Zebrowitz, Leslie A.; Franklin, Robert G.; Boshyan, Jasmine; Luevano, Victor; Agrigoroaei, Stefan; Milosavljevic, Bosiljka; Lachman, Margie E.

2015-01-01

We examined older and younger adults’ accuracy judging the health and competence of faces. Accuracy differed significantly from chance and varied with face age but not rater age. Health ratings were more accurate for older than younger faces, with the reverse for competence ratings. Accuracy was greater for low attractive younger faces, but not for low attractive older faces. Greater accuracy judging older faces’ health was paralleled by greater validity of attractiveness and looking older as predictors of their health. Greater accuracy judging younger faces’ competence was paralleled by greater validity of attractiveness and a positive expression as predictors of their competence. Although the ability to recognize variations in health and cognitive ability is preserved in older adulthood, the effects of face age on accuracy and the different effects of attractiveness across face age may alter social interactions across the life span. PMID:25244467

Last Glacial Maximum and Lateglacial in the Polish High Tatra Mountains - Revised deglaciation chronology based on the 10Be exposure age dating

NASA Astrophysics Data System (ADS)

Makos, Michał; Rinterknecht, Vincent; Braucher, Régis; Tołoczko-Pasek, Anna; Arnold, Maurice; Aumaître, Georges; Bourlès, Didier; Keddadouche, Karim; Aster Team

2018-05-01

Deglaciation chronology of the Polish High Tatra Mountains has been reconstructed based on 10Be exposure age dating. Fifty-seven rock samples were collected from boulders located on the terminal and lateral moraines that limit the horizontal extent of the LGM and the Lateglacial glaciers in the Biała Woda and Sucha Woda catchments. The uncertainty-weighted mean age of 21.5 ± 2.5 ka obtained for the maximum terminal moraine in the Sucha Woda Valley indicates that the oldest preserved moraines were formed during the global LGM. The age population ranges between 15.1 ± 1.0 and 28.3 ± 2.0 ka, and suggests that glaciers reached their maximum position (LGM I) as early as 28-25 ka and the final stabilization of the form occurred much later possibly after melting of buried dead ice. The younger glacial oscillation (LGM II) occurred no later than 20.5 ka and is represented by well-preserved termino-lateral moraine systems in the Pańszczyca Valley. The first Lateglacial stage (LG1) in the study area is documented in the Rybi Potok Valley at the RP1 moraine (1300 m a.s.l.), which was stable at around 16.6 ± 0.3 ka. The younger LG2 stage has no defined absolute age, however, it is constrained between 16.5 and 15.5 ka by the timing of the LG3 stage. This cold event is represented by well-formed moraines in the Roztoka/Pięć Stawów Polskich, Rybi Potok and Pańszczyca valleys of which exposure age indicates their deposition between 15.0 ± 0.5 and 15.6 ± 0.1 ka. The LG1, LG2 and LG3 stages likely occurred during the Oldest Dryas cold stage (Greenland Stadial 2.1a) related to the North Atlantic cooling Heinrich Event 1. The youngest glacial oscillation is evidenced by moraines in the Pusta and Pańszczyca valleys. These moraines are composed of very large granitic blocks of which exposure ages often exhibit isotope inheritance. This is reflected by the youngest P3 moraine in the Pańszczyca Valley with a mean age of deposition close to the LGM. The R4 moraine system in

Pregnant and parenting adolescents and their younger sisters: the influence of relationship qualities for younger sister outcomes.

PubMed

East, P L; Shi, C R

1997-04-01

On the basis of social modeling theory and a sibling interaction hypothesis, it was hypothesized that specific relationship qualities between a pregnant or parenting teen and her younger sister would be associated with permissive younger sister outcomes, such as permissive childbearing attitudes and permissive sexual behavior. Results indicated that negative relationship qualities, such as rivalry, competition, and conflict, were more closely related to younger sisters engaging in problem delinquent-like behavior and sexual behavior than were positive relationship qualities, such as warmth and closeness. Additionally, a shared friendship network with the older sister was found to be associated with extensive younger sister problem behavior and sexual behavior. Three potential explanatory processes are discussed.

Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA

USGS Publications Warehouse

Mason, J.A.; Miao, X.; Hanson, P.R.; Johnson, W.C.; Jacobs, P.M.; Goble, R.J.

2008-01-01

Various lines of evidence support conflicting interpretations of the timing, abruptness, and nature of climate change in the Great Plains during the Pleistocene-Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation spanned all or part of the B??lling-Aller??d episode (approximately 14.7-12.9 cal ka) and all of the Younger Dryas episode (12.9-11.5 cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5-9 cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10 cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial

The Big Chills

NASA Astrophysics Data System (ADS)

Bond, G. C.; Dwyer, G. S.; Bauch, H. A.

2002-12-01

At the end of the last glacial, the Earth's climate system abruptly shifted into the Younger Dryas, a 1500-year long cold snap known in the popular media as the Big Chill. Following an abrupt warming ending the Younger Dryas about 11,600 years ago, the climate system has remained in an interglacial state, thought to have been relatively stable and devoid, with possibly one or two exceptions, of abrupt climate change. A growing amount of evidence suggests that this benign view of interglacial climate is incorrect. High resolution records of North Atlantic ice rafted sediment, now regarded as evidence of extreme multiyear sea ice drift, reveal abrupt shifts on centennial and millennial time scales. These have been traced from the end of the Younger Dryas to the present, revealing evidence of significant climate variability through all of the last two millennia. Correlatives of these events have been found in drift ice records from the Arctic's Laptev Sea, in the isotopic composition of North Grip ice, and in dissolved K from the GISP2 ice core, attesting to their regional extent and imprint in proxies of very different origins. Measurements of Mg/Ca ratios in planktic foraminifera over the last two millennia in the eastern North Atlantic demonstrate that increases in drifting multiyear sea ice were accompanied by abrupt decreases in sea surface temperatures, especially during the Little Ice Age. Estimated rates of temperature change are on the order of two degrees centigrade, more than thirty percent of the regional glacial to interglacial change, within a few decades. When compared at the same resolution, these interglacial variations are as abrupt as the last glacial's Dansgaard-Oeschger cycles. The interglacial abrupt changes are especially striking because they occurred within the core of the warm North Atlantic Current. The changes may have been triggered by variations in solar irradiance, but if so their large magnitude and regional extent requires amplifying

Lung cancer in younger patients.

PubMed

Abbasowa, Leda; Madsen, Poul Henning

2016-07-01

Lung cancer remains a leading cause of cancer-related death. The incidence increases with age and the occurrence in young patients is relatively low. The clinicopathological features of lung cancer in younger patients have not been fully explored previously. To assess the age differences in the clinical characteristics of lung cancer, we conducted a retrospective analysis comparing young patients ≤ 65 years of age with an elderly group > 65 years of age. Among 1,232 patients evaluated due to suspicion of lung cancer in our fast-track setting from January-December 2013, 312 newly diagnosed lung cancer patients were included. Patients ≤ 65 years had a significantly higher representation of females (p = 0.0021), more frequent familial cancer aggregation (p = 0.028) and a lower incidence of squamous cell carcinoma (p = 0.0133). When excluding pure carcinoid tumours, a significantly higher proportion of the younger patients presented with advanced stage disease (p = 0.0392). Combined modality therapy was more common in younger patients (p = 0.0009), while chemotherapy appeared less prevalent among the elderly (p = 0.0015). Lung cancer in younger patients comprises a distinct clinicopathological entity with more frequent advanced stage disease and a significantly greater proportion with a family history of cancer. Implementing genetic background assessments and considering lung cancer as a possible diagnosis in younger, symptomatic patients, is of paramount importance. none. The study was approved by the -Danish Data Protection Agency.

Two episodes of meltwater influx from glacial Lake Agassiz into the Lake Michigan basin and their climatic contrasts

USGS Publications Warehouse

Colman, Steven M.; Keigwin, L.D.; Forester, R.M.

1994-01-01

Two episodes of meltwater influx from glacial Lake Agassiz are recorded as prominent sedimentologic, isotopic, magnetic, and faunal signatures in southern Lake Michigan profundal sediments. As a tributary to the main path of eastward Lake Agassiz flow, southern Lake Michigan recorded only the largest, catastrophic discharges. The distinctive Wilmette Bed, a massive gray mud that interrrupts laminated red glaciolacustrine clays, marks the first episode, which occurred near the beginning of the Younger Dryas cooling events. The associated discharge may have played a role in the inception or severity of the Younger Dryas event. An oxygen isotope excursion in biogenic carbonate and changes in ostracode assemblages mark the second episode, which appears to have had at least two pulses, dated by accelerator mass spectrometer 14C ages on biogenic carbonate at about 8.9 and 8.6 ka. The second episode occurred during the early Holocene peak in global meltwater discharge and apparently had little widespread climatic or oceanographic effect. The contrast between the effects associated with these two episodes of meltwater discharge emphasizes the complexity of the ice sheet-ocean-climate system. -Authors

Burnout in Australasian Younger Fellows.

PubMed

Benson, Sarah; Sammour, Tarik; Neuhaus, Susan J; Findlay, Bruce; Hill, Andrew G

2009-09-01

Burnout is the state of prolonged physical, emotional and psychological exhaustion characteristic of individuals working in human service occupations. This study examines the prevalence of burnout among Younger Fellows of the Royal Australasian College of Surgeons and its relationship to demographic variables. In March 2008, a survey was sent via email to 1287 Younger Fellows. This included demographic questions, a measure of burnout (Copenhagen Burnout Inventory), and an estimate of social desirability (Marlowe-Crowne Social Desirability Scale - Form C). Females exhibited higher levels of personal burnout (P < 0.001) and work-related burnout (P < 0.025), but no significant difference in patient-related burnout. Younger Fellows in hospitals with less than 50 beds reported significantly higher patient-related burnout levels (mean burnout 37.0 versus 22.1 in the rest, P = 0.004). An equal work division between public and private practice resulted in higher work-related burnout than concentration of work in one sector (P < 0.05). Younger Fellows working more than 60 hours per week reported significantly higher personal burnout than those who worked less than this (P < 0.05). There was no significant correlation between age, country of practice, surgical specialty and any of the burnout subscales. Female surgeons, surgeons that work in smaller hospitals, those that work more than 60 h per week, and those with practice division between the private and public sectors, are at a particularly high risk of burnout. Further enquiry into potentially remediable causes for the increased burnout in these groups is indicated.

Older Siblings Influence Younger Siblings' Motor Development

ERIC Educational Resources Information Center

Berger, Sarah E.; Nuzzo, Katie

2008-01-01

Evidence exists for two competing theories about the effects of having an older sibling on development. Previous research has found that having an older sibling has both advantages and disadvantages for younger siblings' development. This study examined whether and how older siblings influenced the onset of their own younger siblings' motor…

Breast cancer treatment costs in younger, privately insured women.

PubMed

Allaire, Benjamin T; Ekwueme, Donatus U; Poehler, Diana; Thomas, Cheryll C; Guy, Gery P; Subramanian, Sujha; Trogdon, Justin G

2017-07-01

Younger women (under age 45 years) diagnosed with breast cancer often face more aggressive tumors, higher treatment intensity, lower survival rates, and greater financial hardship. The purpose of this study was to estimate breast cancer costs by stage at diagnosis during the first 18 months of treatment for privately insured younger women. We analyzed North Carolina cancer registry data linked to claims data from private insurers from 2003 to 2010. Breast cancer patients were split into two cohorts: a younger and older group aged 21-44 and 45-64 years, respectively. We conducted a cohort study and matched women with and without breast cancer using age, ZIP, and Charlson Comorbidity Index. We calculated mean excess costs between breast cancer and non-breast cancer patients at 6, 12, and 18 months. For younger women, AJCC 6th edition stage II cancer was the most common at diagnosis (40%), followed by stage I (34%). On the other hand, older women had more stage I (46%) cancer followed by stage II (34%). The excess costs for younger and older women at 12 months were $97,486 (95% confidence interval [CI] $93,631-101,341) and $75,737 (95% CI $73,962-77,512), respectively. Younger breast cancer patients had both a higher prevalence of later-stage disease and higher within-stage costs. The study reports high costs of treatment for both younger and older women than a non-cancer comparison group; however, the estimated excess cost was significantly higher for younger women. The financial implications of breast cancer treatment costs for younger women need to be explored in future studies.

Salinity history of the northern Atlantic during the last deglaciation

NASA Astrophysics Data System (ADS)

Broecker, Wallace S.

1990-08-01

The claim has been made (see Broecker et al., 1988) that production of North Atlantic Deep Water terminated during Younger Dryas time and that the onset of this termination occurred about 11,000 years ago when the flow of meltwater from a large segment of the southern margin of the Laurentide ice sheet was diverted from the Mississippi to the St. Lawrence drainage. Fairbanks [1989] points out a serious weakness in this argument. Based on a sea level curve derived from radiocarbon dates on coral obtained from borings made off the Barbados coast, he suggests that a lull in the melting of the ice caps during Younger Dryas time may have more than compensated for the impact of the diversion. The purpose of this paper is to reassess the situation regarding the origin of the Younger Dryas in light of this new evidence. Currently the salinity of surface waters in the northern Atlantic is influenced by three fluxes. Water vapor transport from the Atlantic drainage basin to the Pacific-Indian basin tends to raise the salinity of the entire Atlantic. The excess over evaporation of precipitation and runoff poleward of 40°N tends to reduce the salinity of waters in this region relative to the Atlantic average. The conveyor circulation of the Atlantic trades more salty waters of the Atlantic with less salty waters outside the Atlantic tending to drive down the Atlantic's salinity. The conveyor circulation also flushes the northern Atlantic, pushing its salinity toward the mean for the Atlantic. During the period of deglaciation meltwater emanating from the Laurentide and Scandinavian ice sheets was also important. This flux tended to lower not only the salinity of the entire Atlantic but also the salinity of surface waters in the northern Atlantic relative to the Atlantic's mean. As deepwater formation in the northern Atlantic depends critically on the salinity of surface waters, the interactions among these fluxes can change the strength of the conveyor.

Inferring the Provenance of an Alien Species with DNA Barcodes: The Neotropical Butterfly Dryas iulia in Thailand

PubMed Central

Burg, Noah A.; Pradhan, Ashman; Gonzalez, Rebecca M.; Morban, Emely Z.; Zhen, Erica W.; Sakchoowong, Watana; Lohman, David J.

2014-01-01

The Neotropical butterfly Dryas iulia has been collected from several locations in Thailand and Malaysia since 2007, and has been observed breeding in the wild, using introduced Passiflora foetida as a larval host plant. The butterfly is bred by a butterfly house in Phuket, Thailand, for release at weddings and Buddhist ceremonies, and we hypothesized that this butterfly house was the source of wild, Thai individuals. We compared wing patterns and COI barcodes from two, wild Thai populations with individuals obtained from this butterfly house. All Thai individuals resemble the subspecies D. iulia modesta, and barcodes from wild and captive Thai specimens were identical. This unique, Thai barcode was not found in any of the 30 specimens sampled from the wild in the species' native range, but is most similar to specimens from Costa Rica, where many exporting butterfly farms are located. These data implicate the butterfly house as the source of Thailand's wild D. iulia populations, which are currently so widespread that eradication efforts are unlikely to be successful. PMID:25119899

Inferring the provenance of an alien species with DNA barcodes: the neotropical butterfly Dryas iulia in Thailand.

PubMed

Burg, Noah A; Pradhan, Ashman; Gonzalez, Rebecca M; Morban, Emely Z; Zhen, Erica W; Sakchoowong, Watana; Lohman, David J

2014-01-01

The Neotropical butterfly Dryas iulia has been collected from several locations in Thailand and Malaysia since 2007, and has been observed breeding in the wild, using introduced Passiflora foetida as a larval host plant. The butterfly is bred by a butterfly house in Phuket, Thailand, for release at weddings and Buddhist ceremonies, and we hypothesized that this butterfly house was the source of wild, Thai individuals. We compared wing patterns and COI barcodes from two, wild Thai populations with individuals obtained from this butterfly house. All Thai individuals resemble the subspecies D. iulia modesta, and barcodes from wild and captive Thai specimens were identical. This unique, Thai barcode was not found in any of the 30 specimens sampled from the wild in the species' native range, but is most similar to specimens from Costa Rica, where many exporting butterfly farms are located. These data implicate the butterfly house as the source of Thailand's wild D. iulia populations, which are currently so widespread that eradication efforts are unlikely to be successful.

Framing Effects in Younger and Older Adults

PubMed Central

Kim, Sunghan; Goldstein, David; Hasher, Lynn; Zacks, Rose T.

2006-01-01

A growing literature on decision making in older adults suggests that they are more likely to use heuristic processing than are younger adults. We assessed this tendency in the context of a framing effect, a decision-making phenomenon whereby the language used to describe options greatly influences the decision maker’s choice. We compared decision making under a standard (“heuristic”) condition and also under a “justification” condition known to reduce reliance on heuristics. In the standard condition, older adults were more susceptible than younger adults to framing but the two groups did not differ when participants were asked to provide a justification. Thus, although older adults may spontaneously rely more on heuristic processing than younger adults, they can be induced to take a more systematic approach to decision making. PMID:15980289

Framing effects in younger and older adults.

PubMed

Kim, Sunghan; Goldstein, David; Hasher, Lynn; Zacks, Rose T

2005-07-01

A growing literature on decision making in older adults suggests that they are more likely to use heuristic processing than are younger adults. We assessed this tendency in the context of a framing effect, a decision-making phenomenon whereby the language used to describe options greatly influences the decision maker's choice. We compared decision making under a standard ("heuristic") condition and also under a "justification" condition known to reduce reliance on heuristics. In the standard condition, older adults were more susceptible than younger adults to framing but the two groups did not differ when participants were asked to provide a justification. Thus, although older adults may spontaneously rely more on heuristic processing than younger adults, they can be induced to take a more systematic approach to decision making.

Lateglacial vegetation dynamics in the eastern Baltic region between 14,500 and 11,400 cal yr BP: A complete record since the Bølling (GI-1e) to the Holocene

NASA Astrophysics Data System (ADS)

Veski, Siim; Amon, Leeli; Heinsalu, Atko; Reitalu, Triin; Saarse, Leili; Stivrins, Normunds; Vassiljev, Jüri

2012-04-01

This paper discusses a complete record of vegetation history since the Bølling (GI-1e) warming (14,500 cal yr BP) up to the Holocene in Latvia. To date, this is the only complete record of such age in the eastern Baltic area and the northernmost area for which Bølling records are present. Combining pollen evidence, pollen accumulation rates (PAR) and plant macrofossil data, we assess the local and regional vegetation development, and we attempt to separate the true Lateglacial vegetation signal by removing the obviously redeposited thermophilous pollen; however, we remove not only their signal, we discuss the possibilities of separating the redeposition signal of the so-called "local Lateglacial trees", pine and birch, by looking at their corrosion and degradation. The results show that the Bølling warming in the eastern Baltic area was a treeless tundra community consisting of the shrubs Betula nana, Dryas octopetala and Salix polaris. The Older Dryas cold spell is clearly recognised as a decline in the total concentration of plant macrofossils and PARs at between 14,200 and 13,500 cal yr BP. At 13,460 cal yr BP, the B. nana macrofossils disappear, and tree birch (Betula sect. Albae) appears, marking the start of tree birch forest. The presence of pine forest is confirmed by a variety of macrofossils, including bark, wood, needles and seeds, since 13,400 cal yr BP, at the same time at which pine stomata are found. The first identified pine stomata finds are associated with a Pinus PAR over 3000 grains cm-2 yr-1 and pine macrofossil finds with a Pinus PAR over 4000 grains cm-2 yr-1. During the warmest period of the GI-1a (Allerød) at 13,000-12,700 cal yr BP, a pine forest with deciduous trees (birch -Betula pendula and aspen -Populus tremula) developed in the study area. The Younger Dryas (GS-1) cooling strongly affected the floral composition in eastern Latvia. The PAR of the tree taxa declined abruptly from a maximum value at 12,700 to below 1000 grains cm-2

Mental health among younger and older caregivers of dementia patients.

PubMed

Koyama, Asuka; Matsushita, Masateru; Hashimoto, Mamoru; Fujise, Noboru; Ishikawa, Tomohisa; Tanaka, Hibiki; Hatada, Yutaka; Miyagawa, Yusuke; Hotta, Maki; Ikeda, Manabu

2017-03-01

Caregiver burden in dementia is an important issue, but few studies have examined the mental health of younger and older family caregivers by comparing them with age- and gender-matched community residents. We aimed to compare the mental health of dementia caregivers with that of community residents and to clarify factors related to mental health problems in younger and older caregivers. We studied 104 dementia caregivers; 46 were younger (<65 years) and 58 were older (≥65 years). A total of 104 community residents who were matched for age and gender were selected. We compared depression (Center for Epidemiologic Studies Depression Scale for younger participants; Geriatric Depression Scale for older participants), health-related quality of life (QOL) short-form health survey (SF-8), sleep problems, and suicidal ideation between the caregivers and community residents by age. Behavioural and psychological symptoms of dementia, activities of daily living (ADL), and instrumental ADL were assessed among patients with dementia using the Neuropsychiatric Inventory, Physical Self-Maintenance Scale, and Lawton Instrumental ADL Scale, respectively. According to SF-8 results, both younger and older caregivers had significantly worse mental QOL than community residents (younger caregivers: 46.3 vs community residents: 49.7, P = 0.017; older caregivers: 48.2 vs community residents: 51.1, P = 0.024) but were not more depressive. Sleep problems were significantly more frequent in younger caregivers (39.1%) than in community residents (17.0%) (P = 0.017). Multiple regression analysis revealed that caregivers' deteriorated mental QOL was associated with patients' behavioural and psychological symptoms of dementia in younger caregivers and with dementia patients' instrumental ADL and female gender in older caregivers. Dementia caregivers had a lower mental QOL than community residents. To maintain caregivers' mental QOL, it is necessary to provide younger

Evidence for seasonal low salinity surface waters in the Gulf of Mexico over the last 16,000 years

NASA Astrophysics Data System (ADS)

Spero, Howard J.; Williams, Douglas F.

1990-12-01

Oxygen isotopic analyses of individual Orbulina universa from Orca Basin core EN32-PC6 document the presence of low salinity surface waters in the northern Gulf of Mexico over the past 16 kyr. Isotopic data from an interval immediately following the Younger Dryas Event indicate the rapid decrease in δ18O values at the conclusion of the Younger Dryas was due to a year-round return of meltwater to the Gulf of Mexico. Data indicate periodic or seasonal low-salinity waters existed over the region of the Orca Basin prior to the initiation of the meltwater spike. Estimates suggest O. universa grew its shell in salinities at least 4.5 ‰ below ambient. Since O. universa may have calcified deep in the mixed layer during periods of low salinity, surface salinities could have been even lower. Comparison of the average of individual O. universa oxygen isotopic values with data from multiple shell samples of white Gs. ruber from the same core samples demonstrates that the two species record similar values during the late Holocene. In contrast, O. universa records lower oxygen isotopic values during the late glacial/deglacial intervals, possibly due to differences in seasonal distribution or shell ontogeny between the two species.

Immunization Uptake in Younger Siblings of Children with Autism Spectrum Disorder

ERIC Educational Resources Information Center

Kuwaik, Ghassan Abu; Roberts, Wendy; Zwaigenbaum, Lonnie; Bryson, Susan; Smith, Isabel M.; Szatmari, Peter; Modi, Bonnie M.; Tanel, Nadia; Brian, Jessica

2014-01-01

Background: Parental concerns persist that immunization increases the risk of autism spectrum disorder, resulting in the potential for reduced uptake by parents of younger siblings of children with autism spectrum disorder ("younger sibs"). Objective: To compare immunization uptake by parents for their younger child relative to their…

[A clinical study on pulmonary tuberculosis in younger age groups].

PubMed

Takahara, M; Suzuki, T; Toyota, E; Kobayashi, N; Kawada, H; Kudoh, K

2000-04-01

In 1997, the number of newly registered patients with pulmonary tuberculosis increased, compared with that in 1996, in Japan. The majority of the increase were occupied by elder patients 70 years of age or higher. But in younger group less than 30 years old, a reduction in the incidence of tuberculosis had been slowed down, until 1996. The purpose of this report is to elucidate the characteristics of these younger patients. 139 cases younger than 30 years of age, who were hospitalized in the tuberculous ward of IMCJ from April 1995 to March 1998, were investigated, and were compared with the control group (557 cases), 30-79 years old who were hospitalized during the same period. In the younger group, the proportion of women cases, discovered by health examination, foreigners, and contact with TB patients in the past was significantly higher than in the control group. But there were no difference between the both groups, concerning the proportion of those spending irregular life or living alone. The proportion of sputa smear negative cases was significantly higher in the younger group than in the control. For early diagnosis of TB among younger group, the application of bronchofiberscopy and nucleic acid diagnostic method, are encouraged.

Lacustrine Basal Ages Constrain the Last Deglaciation in the Uinta Mountains, Utah, USA

NASA Astrophysics Data System (ADS)

Munroe, Jeffrey; Laabs, Benjamin

2013-04-01

Basal radiocarbon ages from 21 high-elevation lakes limit the timing of final Pleistocene deglaciation in the Uinta Mountains of northeastern Utah, USA. The lakes are located in glacial valleys and cirques 5 to 20 km upstream from LGM terminal moraines at elevations from 2830 to 3475 m. Many are impounded behind recessional moraines. Cores were retrieved from a floating platform with a percussion corer driven to the point of refusal. All penetrated inorganic silty clay beneath gyttja. AMS radiocarbon analyses were made on terrestrial macrofossils, daphnia ephippia, pollen concentrates, and bulk sediment retrieved from the base of each core. No radiocarbon reservoir effect was observed when bulk dates were checked against terrestrial material. Radiocarbon results were converted to calendar years using the IntCal09 calibration curve in OxCal 4.1. Given the stratigraphy observed in the cores, these calibrated basal ages are considered close limits on the timing of the local deglaciation and lake formation. The oldest three lakes have basal radiocarbon ages that calibrate to a few centuries after the Bölling/Alleröd warming, indicating that the landscape was becoming ice free at this time. These are followed by an overlapping group of five lakes with basal ages between 13.5 and 13.0 ka BP. Five more cores, from four separate lakes, have basal ages tightly clustered between 13.0 and 12.5 ka BP. Three of these lakes are dammed by moraines, suggesting glacial activity during the early part of the Younger Dryas interval. The lone kettle lake in the study yielded a basal age of 12.3 ka BP, considerably younger than the basal age of 13.9 ka BP from a nearby lake filling a bedrock basin, indicating that buried ice may have been locally stable for more than a millennium after deglaciation. The remaining seven lakes have basal ages between 12.0 and 11.0 ka BP. Four of these lakes are also dammed by moraines. These two non-overlapping clusters of basal ages for moraine

Tropical Climate Variability From the Last Glacial Maximum to the Present

DTIC Science & Technology

2005-09-01

between the tropics and extrat- ropics remains an open question. Over the course of the glacial-interglacial cycles of the past 800,000 years, the high...roughly 80% of the total CSEs. The remaining 12 Younger Dryas in the Cariaco Basin. CSE peaks are consistently smaller than those mentioned [29] CSEs I...33] CSEs 8 and 15 remain unidentified. It is evident record. Identification and downcore analysis of these CSE from their downcore trends, however

Lateglacial retreat chronology of the Scandinavian Ice Sheet in Finnmark, northern Norway, reconstructed from surface exposure dating of major end moraines

NASA Astrophysics Data System (ADS)

Romundset, Anders; Akçar, Naki; Fredin, Ola; Tikhomirov, Dmitry; Reber, Regina; Vockenhuber, Christof; Christl, Marcus; Schlüchter, Christian

2017-12-01

We report results from a comprehensive surface exposure dating campaign in eastern Finnmark, located in the northernmost part of Norway and close to the Norwegian-Russian border. This is a palaeo-glaciologically important region as it sits near the proposed border-zone between the former Scandinavian and Barents Sea Ice Sheets. However, until now the deglaciation history has few direct dates onshore and the chronology of ice front retreat is instead found by correlating ice-marginal deposits with isostatically raised shorelines and marine sediment cores. We measured the content of 10Be (N = 22) and 36Cl (N = 17) from boulders located at the crest of major moraine ridges at four localities; Kjæs, Kongsfjorden, Vardø and Kirkenes. These are key localities of existing regional reconstructions of ice recession in this area. Despite some spread in age results from each locality due to methodological challenges associated with surface exposure dating, the large numbers of samples from each site except Kjæs still allow for obtaining clusters of similar ages which are used for arriving at a likely chronology of ice front retreat. Our results show that the Kongsfjorden and Vardø moraines were deposited 14.3 ± 1.7 ka and 13.6 ± 1.4 ka, respectively, and thus point to a Older Dryas age of the proposed 'Outer Porsanger' deglaciation sub-stage. Moraine ridges belonging to the 'Main' sub-stage near Kirkenes were dated to 11.9 ± 1.2 ka, corresponding well with the ice retreat chronology farther west in northern Norway and suggesting that the maximum Younger Dryas ice sheet extent was attained in the late Younger Dryas along a more than 500 km long stretch in northernmost Scandinavia.

Attitudes toward Younger and Older Adults: The German Aging Semantic Differential

ERIC Educational Resources Information Center

Gluth, Sebastian; Ebner, Natalie C.; Schmiedek, Florian

2010-01-01

The present study used the German Aging Semantic Differential (ASD) to assess attitudes toward younger and older adults in a heterogeneous sample of n = 151 younger and n = 143 older adults. The questionnaire was administered in two versions, one referring to the evaluation of younger adults, the other to the evaluation of older adults.…

How Arousal Affects Younger and Older Adults' Memory Binding

PubMed Central

Nashiro, Kaoru; Mather, Mara

2009-01-01

A number of recent studies have shown that associative memory for within-item features is enhanced for emotionally arousing items, whereas arousal-enhanced binding is not seen for associations between distinct items (for a review see Mather, 2007). The costs and benefits of arousal in memory binding have been examined for younger adults but not for older adults. The present experiment examined whether arousal would enhance younger and older adults' within-item and between-item memory binding. The results revealed that arousal improved younger adults' within-item memory binding but not that of older adults. Arousal worsened both groups' between-item memory binding. PMID:21240821

How arousal affects younger and older adults' memory binding.

PubMed

Nashiro, Kaoru; Mather, Mara

2011-01-01

A number of recent studies have shown that associative memory for within-item features is enhanced for emotionally arousing items, whereas arousal-enhanced binding is not seen for associations between distinct items (for a review, see Mather, 2007, Perspectives on Psychological Science, 2, 33-52). The costs and benefits of arousal in memory binding have been examined for younger adults but not for older adults. The present experiment examined whether arousal would enhance younger and older adults' within-item and between-item memory binding. The results revealed that arousal improved younger adults' within-item memory binding but not that of older adults. Arousal worsened both groups' between-item memory binding.

Media use by children younger than 2 years.

PubMed

Brown, Ari

2011-11-01

In 1999, the American Academy of Pediatrics (AAP) issued a policy statement addressing media use in children. The purpose of that statement was to educate parents about the effects that media--both the amount and the content--may have on children. In one part of that statement, the AAP recommended that "pediatricians should urge parents to avoid television viewing for children under the age of two years." The wording of the policy specifically discouraged media use in this age group, although it is frequently misquoted by media outlets as no media exposure in this age group. The AAP believed that there were significantly more potential negative effects of media than positive ones for this age group and, thus, advised families to thoughtfully consider media use for infants. This policy statement reaffirms the 1999 statement with respect to media use in infants and children younger than 2 years and provides updated research findings to support it. This statement addresses (1) the lack of evidence supporting educational or developmental benefits for media use by children younger than 2 years, (2) the potential adverse health and developmental effects of media use by children younger than 2 years, and (3) adverse effects of parental media use (background media) on children younger than 2 years.

Optimism for the Future in Younger and Older Adults.

PubMed

Durbin, Kelly A; Barber, Sarah J; Brown, Maddalena; Mather, Mara

2018-01-09

Research has suggested that older adults are less optimistic about their future than younger adults; however, a limitation of prior studies is that younger and older adults were forecasting to different ages and stages of life. To address this, we investigated whether there are age differences in future optimism when people project to the exact same age. We also tested whether optimism differs when projecting one's own future versus another person's future. Participants were 285 younger and 292 older adults recruited from Amazon Mechanical Turk. Participants completed writing and word-rating tasks in which they imagined their own future in 15 years, their own future at age 85, or the average person's future at age 85. Younger adults were more optimistic than older adults about their own future in 15 years. In contrast, both age groups were similarly optimistic about their future at age 85 and expected it to be more positive than others' future at age 85. Contrary to previous research, younger and older adults had comparable future forecasts when projecting to the exact same age. These findings emphasize the need to consider age and stage of life when examining age differences in future optimism. © The Author(s) 2018. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

OCCURRENCE OF COLORECTAL ADENOMAS IN YOUNGER ADULTS: AN EPIDEMIOLOGIC NECROPSY STUDY

PubMed Central

Pendergrass, Cheryl J.; Edelstein, Daniel L.; Hylind, Linda M.; Phillips, Blaine T.; Iacobuzio-Donahue, Christine; Romans, Katharine; Griffin, Constance A.; Cruz-Correa, Marcia; Tersmette, Anne C.; Offerhaus, G. Johan A.; Giardiello, Francis M.

2009-01-01

Background and Aims The colorectal adenoma is the precursor lesion in virtually all colorectal cancers. Occurrence of colorectal adenomas has been studied in older adults but analysis in younger adults is lacking. Methods The prevalence by age, sex, race, and location, and the number of colorectal adenomas detected was investigated using epidemiologic necropsy in 3558 persons aged 20–89 autopsied from 1985 to 2004 at the Johns Hopkins Hospital. Results were standardized to the general population. Younger adults 20–49 years old were compared to older adults 50 to 89 years old. Results The prevalence of colorectal adenomas in younger adults increased from 1.72% to 3.59% from the 3rd to 5th decade of life and then sharply increased after age 50. In younger adults, adenomas were more prevalent in men than women (RR= 1.09, CI 1.07–1.11) and whites than blacks (RR=1.28, CI 1.26–1.31). Overall, both younger and older adults had predominately left-sided adenomas, but blacks in both age groups had more right-sided adenomas. Occurrence of two or more adenomas in younger adults and five or more in older adults was greater than 2 standard deviations from the mean. Conclusions Colorectal adenomas infrequently occur in younger adults and are more prevalent in the left colon. Irrespective of age, blacks have more right-sided adenomas suggesting need for screening the entire colorectum. Two or more adenomas in younger adults and five or more in older adults represents polyp burden outside the normal expectation. PMID:18558514

How retellings shape younger and older adults' memories.

PubMed

Barber, Sarah J; Mather, Mara

2014-04-01

The way a story is retold influences the way it is later remembered; after retelling an event in a biased manner people subsequently remember the event in line with their distorted retelling. This study tested the hypothesis that this should be especially true for older adults. To test this, older and younger adults retold a story to be entertaining, to be accurate, or did not complete an initial retelling. Later, all participants recalled the story as accurately as possible. On this final test younger adults were unaffected by how they had previously retold the story. In contrast, older adults had better memory for the story's content and structure if they had previously retold the story accurately. Furthermore, for older adults, greater usage of storytelling language during the retelling was associated with lower subsequent recall. In summary, retellings exerted a greater effect on memory in older, compared with younger, adults.

Older (but Not Younger) Siblings Facilitate False Belief Understanding.

ERIC Educational Resources Information Center

Ruffman, Ted; Perner, Josef; Naito, Mika; Parkin, Lindsay; Clements, Wendy A.

1998-01-01

Four experiments and an analysis of pooled data from English and Japanese children show a linear increase in understanding false beliefs with number of older siblings; no such effect for children younger than 38 months; no helpful effect of younger siblings at any age; no effect of siblings' gender; and no helpful effect of siblings on a source…

The Effects of Feedback on Memory Strategies of Younger and Older Adults

PubMed Central

Zhang, Fan; Zhang, Xin; Luo, Meng; Geng, Haiyan

2016-01-01

Existing literature suggests that feedback could effectively reduce false memories in younger adults. However, it is unclear whether memory performance in older adults also might be affected by feedback. The current study tested the hypothesis that older adults can use immediate feedback to adjust their memory strategy, similar to younger adults, but after feedback is removed, older adults may not be able to maintain using the memory strategy. Older adults will display more false memories than younger adults due to a reduction in attentional resources. In Study 1, both younger and older adults adjusted gist processing and item-specific processing biases based on the feedback given (i.e., biased and objective feedback). In Study 2 after the feedback was removed, only younger adults with full attention were able to maintain the feedback-shaped memory strategy; whereas, both younger adults with divided attention and older adults had increased false memories after feedback was removed. The findings suggest that environmental support helps older adults as well as younger adults to adopt a memory strategy that demands high attentional resources, but when the support is removed, older adults can no longer maintain such a strategy. PMID:28033327

The Effects of Feedback on Memory Strategies of Younger and Older Adults.

PubMed

Zhang, Fan; Zhang, Xin; Luo, Meng; Geng, Haiyan

2016-01-01

Existing literature suggests that feedback could effectively reduce false memories in younger adults. However, it is unclear whether memory performance in older adults also might be affected by feedback. The current study tested the hypothesis that older adults can use immediate feedback to adjust their memory strategy, similar to younger adults, but after feedback is removed, older adults may not be able to maintain using the memory strategy. Older adults will display more false memories than younger adults due to a reduction in attentional resources. In Study 1, both younger and older adults adjusted gist processing and item-specific processing biases based on the feedback given (i.e., biased and objective feedback). In Study 2 after the feedback was removed, only younger adults with full attention were able to maintain the feedback-shaped memory strategy; whereas, both younger adults with divided attention and older adults had increased false memories after feedback was removed. The findings suggest that environmental support helps older adults as well as younger adults to adopt a memory strategy that demands high attentional resources, but when the support is removed, older adults can no longer maintain such a strategy.

How retellings shape younger and older adults’ memories

PubMed Central

Mather, Mara

2014-01-01

The way a story is retold influences the way it is later remembered; after retelling an event in a biased manner people subsequently remember the event in line with their distorted retelling. This study tested the hypothesis that this should be especially true for older adults. To test this, older and younger adults retold a story to be entertaining, to be accurate, or did not complete an initial retelling. Later, all participants recalled the story as accurately as possible. On this final test younger adults were unaffected by how they had previously retold the story. In contrast, older adults had better memory for the story’s content and structure if they had previously retold the story accurately. Furthermore, for older adults, greater usage of storytelling language during the retelling was associated with lower subsequent recall. In summary, retellings exerted a greater effect on memory in older, compared with younger, adults. PMID:25436107

Perceptions of emotion and age among younger, midlife, and older adults.

PubMed

Santorelli, Gennarina D; Ready, Rebecca E; Mather, Molly A

2018-03-01

Older adults report greater emotional well-being than younger persons, yet negative stereotypes about aging are pervasive. Little is known about age group perceptions of emotion in adulthood, particularly for familiar persons. Thus, this project determined perceptions of general affect in familiar younger and older adults. In two studies, participants (Study 1, younger adult n = 123, older adult n = 43; Study 2, younger adult n = 34, midlife adult n = 41, older adult n = 16) provided self-report data about their affect in general, as well as reported on the affect of a familiar younger person (aged 18--34) and a familiar older person (aged 65 or older). Emotion scales assessed high- and low-arousal positive and negative affect. Results suggest a less favorable perception of emotion experiences of older adults compared to younger adults. Specifically, participants of all age groups rated older adults as having lower positive emotions and higher negative emotions than is found in self-report data. Perceptions of emotion in older adulthood reflect stereotypes of negative functioning. Older adult participants were not immune to holding negative views about older adults. Negative perceptions about emotion experiences in later life may be detrimental to the physical and mental health of older adults.

Destination memory accuracy and confidence in younger and older adults.

PubMed

Johnson, Tara L; Jefferson, Susan C

2018-01-01

Background/Study Context: Nascent research on destination memory-remembering to whom we tell particular information-suggested that older adults have deficits in destination memory and are more confident on inaccurate responses than younger adults. This study assessed the effects of age, attentional resources, and mental imagery on destination memory accuracy and confidence in younger and older adults. Using computer format, participants told facts to pictures of famous people in one of four conditions (control, self-focus, refocus, imagery). Older adults had lower destination memory accuracy than younger adults, driven by a higher level of false alarms. Whereas younger adults were more confident in accurate answers, older adults were more confident in inaccurate answers. Accuracy across participants was lowest when attention was directed internally but significantly improved when mental imagery was used. Importantly, the age-related differences in false alarms and high-confidence inaccurate answers disappeared when imagery was used. Older adults are more likely than younger adults to commit destination memory errors and are less accurate in related confidence judgments. Furthermore, the use of associative memory strategies may help improve destination memory across age groups, improve the accuracy of confidence judgments in older adults, and decrease age-related destination memory impairment, particularly in young-old adults.

Mercury Concentrations in Coastal Sediment from Younger Lagoon, Central California

NASA Astrophysics Data System (ADS)

Hohn, R. A.; Ganguli, P. M.; Swarzenski, P. W.; Richardson, C. M.; Merckling, J.; Johnson, C.; Flegal, A. R.

2013-12-01

Younger Lagoon Reserve, located in northern Monterey Bay, is one of the few relatively undisturbed wetlands that remain along the Central Coast of California. This lagoon system provides protected habitat for more than 100 bird species and for populations of fish, mammals, and invertebrates. Total mercury (HgT) concentrations in water within Younger Lagoon appear to vary with rainfall conditions and range from about 5-15 pM. These concentrations are similar to HgT in water from six nearby lagoon systems. However, Younger Lagoon contains elevated concentrations of dissolved organic carbon (~1 mM) and monomethylmercury (MMHg, ~1 pM) relative to our comparison lagoon sites (DOC < 0.5 mM and MMHg < 0.5 pM). We attribute Younger Lagoon's high DOC and MMHg to its restricted connection to the ocean and minor riverine contribution. Coastal lagoons in this region typically form at the mouth of streams. They behave as small estuaries during the wet season when surface water discharge keeps the mouth of the stream open to the ocean, and then transition into lagoons in the dry season when a sand berm develops and effectively cuts off surface water exchange. At Younger Lagoon, the sand berm remains intact throughout the year, breaching only during particularly high tides or intense rain events. Therefore, the lagoon's connection to nearshore seawater is primarily via surface water - groundwater interaction through the sand berm. Because Younger Lagoon is largely isolated from a surface water connection with the ocean, runoff from upgradient urban and agricultural land has an enhanced impact on water (and presumably sediment) quality. As a result, the lagoon is eutrophic and experiences annual algal blooms. Groundwater surveys suggest surface water, groundwater, and coastal seawater are hydraulically connected at Younger Lagoon, and mixing among these water masses appears to influence water geochemistry. To date, no chemical analyses have been conducted on sediment from Younger

Older Adolescents' Positive Attitudes toward Younger Adolescents as Sexual Partners

ERIC Educational Resources Information Center

Hegna, Kristinn; Mossige, Svein; Wichstrom, Lars

2004-01-01

The prevalence of older adolescents' positive attitudes toward younger sexual partners was investigated through three measures of self-reported hypothetical likelihood of having sex with preadolescents and younger adolescents (LSA), using a school-based cluster sample of 710 Norwegian 18- to 19-year-olds attending nonvocational high schools in…

Numerical modeling of late Glacial Laurentide advance of ice across Hudson Strait: Insights into terrestrial and marine geology, mass balance, and calving flux

USGS Publications Warehouse

Pfeffer, W.T.; Dyurgerov, M.; Kaplan, M.; Dwyer, J.; Sassolas, C.; Jennings, A.; Raup, B.; Manley, W.

1997-01-01

A time-dependent finite element model was used to reconstruct the advance of ice from a late Glacial dome on northern Quebec/Labrador across Hudson Strait to Meta Incognita Peninsula (Baffin Island) and subsequently to the 9.9-9.6 ka 14C Gold Cove position on Hall Peninsula. Terrestrial geological and geophysical information from Quebec and Labrador was used to constrain initial and boundary conditions, and the model results are compared with terrestrial geological information from Baffin Island and considered in the context of the marine event DC-0 and the Younger Dryas cooling. We conclude that advance across Hudson Strait from Ungava Bay to Baffin Island is possible using realistic glacier physics under a variety of reasonable boundary conditions. Production of ice flux from a dome centered on northeastern Quebec and Labrador sufficient to deliver geologically inferred ice thickness at Gold Cove (Hall Peninsula) appears to require extensive penetration of sliding south from Ungava Bay. The discharge of ice into the ocean associated with advance and retreat across Hudson Strait does not peak at a time coincident with the start of the Younger Dryas and is less than minimum values proposed to influence North Atlantic thermohaline circulation; nevertheless, a significant fraction of freshwater input to the North Atlantic may have been provided abruptly and at a critical time by this event.

Comparison for younger and older adults: Stimulus temporal asynchrony modulates audiovisual integration.

PubMed

Ren, Yanna; Ren, Yanling; Yang, Weiping; Tang, Xiaoyu; Wu, Fengxia; Wu, Qiong; Takahashi, Satoshi; Ejima, Yoshimichi; Wu, Jinglong

2018-02-01

Recent research has shown that the magnitudes of responses to multisensory information are highly dependent on the stimulus structure. The temporal proximity of multiple signal inputs is a critical determinant for cross-modal integration. Here, we investigated the influence that temporal asynchrony has on audiovisual integration in both younger and older adults using event-related potentials (ERP). Our results showed that in the simultaneous audiovisual condition, except for the earliest integration (80-110ms), which occurred in the occipital region for older adults was absent for younger adults, early integration was similar for the younger and older groups. Additionally, late integration was delayed in older adults (280-300ms) compared to younger adults (210-240ms). In audition‑leading vision conditions, the earliest integration (80-110ms) was absent in younger adults but did occur in older adults. Additionally, after increasing the temporal disparity from 50ms to 100ms, late integration was delayed in both younger (from 230 to 290ms to 280-300ms) and older (from 210 to 240ms to 280-300ms) adults. In the audition-lagging vision conditions, integration only occurred in the A100V condition for younger adults and in the A50V condition for older adults. The current results suggested that the audiovisual temporal integration pattern differed between the audition‑leading and audition-lagging vision conditions and further revealed the varying effect of temporal asynchrony on audiovisual integration in younger and older adults. Copyright © 2017 Elsevier B.V. All rights reserved.

Cognitive Control and Lexical Access in Younger and Older Bilinguals

ERIC Educational Resources Information Center

Bialystok, Ellen; Craik, Fergus; Luk, Gigi

2008-01-01

Ninety-six participants, who were younger (20 years) or older (68 years) adults and either monolingual or bilingual, completed tasks assessing working memory, lexical retrieval, and executive control. Younger participants performed most of the tasks better than older participants, confirming the effect of aging on these processes. The effect of…

Neural basis for recognition confidence in younger and older adults.

PubMed

Chua, Elizabeth F; Schacter, Daniel L; Sperling, Reisa A

2009-03-01

Although several studies have examined the neural basis for age-related changes in objective memory performance, less is known about how the process of memory monitoring changes with aging. The authors used functional magnetic resonance imaging to examine retrospective confidence in memory performance in aging. During low confidence, both younger and older adults showed behavioral evidence that they were guessing during recognition and that they were aware they were guessing when making confidence judgments. Similarly, both younger and older adults showed increased neural activity during low- compared to high-confidence responses in the lateral prefrontal cortex, anterior cingulate cortex, and left intraparietal sulcus. In contrast, older adults showed more high-confidence errors than younger adults. Younger adults showed greater activity for high compared to low confidence in medial temporal lobe structures, but older adults did not show this pattern. Taken together, these findings may suggest that impairments in the confidence-accuracy relationship for memory in older adults, which are often driven by high-confidence errors, may be primarily related to altered neural signals associated with greater activity for high-confidence responses.

Neural basis for recognition confidence in younger and older adults

PubMed Central

Chua, Elizabeth F.; Schacter, Daniel L.; Sperling, Reisa A.

2008-01-01

Although several studies have examined the neural basis for age-related changes in objective memory performance, less is known about how the process of memory monitoring changes with aging. We used fMRI to examine retrospective confidence in memory performance in aging. During low confidence, both younger and older adults showed behavioral evidence that they were guessing during recognition, and that they were aware they were guessing when making confidence judgments. Similarly, both younger and older adults showed increased neural activity during low compared to high confidence responses in lateral prefrontal cortex, anterior cingulate cortex, and left intraparietal sulcus. In contrast, older adults showed more high confidence errors than younger adults. Younger adults showed greater activity for high compared to low confidence in medial temporal lobe structures, but older adults did not show this pattern. Taken together, these findings may suggest that impairments in the confidence-accuracy relationship for memory in older adults, which are often driven by high confidence errors, may be primarily related to altered neural signals associated with greater activity for high confidence responses. PMID:19290745

Longitudinal Links between Older Sibling Features and Younger Siblings’ Academic Adjustment during Early Adolescence

PubMed Central

Bouchey, Heather A.; Shoulberg, Erin K.; Jodl, Kathleen M.; Eccles, Jacquelynne S.

2010-01-01

This study investigated prospective relations between (1) older siblings’ support and academic engagement and (2) younger siblings’ academic adjustment from 7th to 8th grade. The study was unique in that it incorporated a sample of both African American and European American adolescents. Also investigated was the extent to which the gender constellation (same-sex vs. mixed-sex) of sibling dyads moderated prospective associations. Findings revealed that, in mixed-sex dyads only, younger siblings’ perceptions of support received from the older sibling and their positive image of the older sibling predicted declines in the younger sibling’s academic self-perceptions and performance over time, even after controlling for younger siblings’ background characteristics and support from parents. Older siblings’ reported support to younger siblings also predicted declines in younger siblings’ academic adjustment, whereas the older siblings’ own level of academic engagement predicted an increase in younger siblings’ academic adjustment over time. Overall, findings did not differ substantially for African and European American adolescents. PMID:20376283

Whole-Person Impairment in Younger Retired NFL Players

PubMed Central

Domb, Benjamin G.; Carter, Chris; Finch, Nathan A.; Hammarstedt, Jon E.; Dunne, Kevin F.; Stake, Christine E.

2014-01-01

Background: Professional American football is a physically demanding, high-impact sport with an elevated risk of injury. Orthopaedic injuries may impose acute, short-term or cumulative consequences throughout a player’s lifetime. Several studies have addressed health and psychosocial concerns of an older, retired population of players in the National Football League (NFL); however, minimal research has examined the orthopaedic toll on younger, retired players. Purpose: This study reports total whole-person impairment (WPI) percentages in a cohort of younger, retired NFL players who presented for disability evaluations based on the use of standardized American Medical Association (AMA) impairment guidelines. Study Design: Case series; Level of evidence, 4. Methods: During the study period of February 2011 to August 2013, 65 younger retired NFL players presented for impairment evaluations. The mean time between retirement and impairment evaluation was 3.1 years (range, 0.3-16.4 years). A complete history and physical examination was performed on all symptomatic joints. A retrospective chart review was conducted on 100% of presenting players to assess orthopaedic burden. Body-part impairment (BPI) percentage for each affected joint was generated. The impairment data for each extremity were then combined with spine impairment data to create WPI percentage. Player demographics, including age, position, and playing time, were also recorded. Results: The average WPI percentage was 37% (range, 19%-53%). Players participating in >30 games (n = 54) had a higher mean WPI percentage (38%) than those playing in <30 games (31%; n = 11) (P = .004). Players competing in >5 seasons (n = 46) were 2.4 times more likely to have a WPI of at least 37% (P = .007). The most common joints players reported as symptomatic were lumbar (n = 63; 97%) and cervical spine (n = 58; 89%). The mean age at evaluation was 33.5 years (range, 27-42 years), and the mean number of seasons played was 7

The effects of emotion on younger and older adults' monitoring of learning.

PubMed

Tauber, Sarah K; Dunlosky, John; Urry, Heather L; Opitz, Philipp C

2017-09-01

Age-related differences in memory monitoring appear when people learn emotional words. Namely, younger adults' judgments of learning (JOLs) are higher for positive than neutral words, whereas older adults' JOLs do not discriminate between positive versus neutral words. In two experiments, we evaluated whether this age-related difference extends to learning positive versus neutral pictures. We also evaluated the contribution of two dimensions of emotion that may impact younger and older adults' JOLs: valence and arousal. Younger and older adults studied pictures that were positive or neutral and either high or low in arousal. Participants made immediate JOLs and completed memory tests. In both experiments, the magnitude of older adults' JOLs was influenced by emotion, and both younger and older adults demonstrated an emotional salience effect on JOLs. As important, the magnitude of participants' JOLs was influenced by valence, and not arousal. Emotional salience effects were also evident on participants' free recall, and older adults recalled as many pictures as did younger adults. Taken together, these data suggest that older adults do not have a monitoring deficit when learning positive (vs. neutral) pictures and that emotional salience effects on younger and older adults' JOLs are produced more by valence than by arousal.

Differences in anxiety and depression symptoms: comparison between older and younger clinical samples.

PubMed

Wuthrich, Viviana M; Johnco, Carly J; Wetherell, Julie L

2015-09-01

Anxiety and depression symptoms change over the lifespan and older adults use different terms to describe their mental health, contributing to under identification of anxiety and depression in older adults. To date, research has not examined these differences in younger and older samples with comorbid anxiety and depression. One hundred and seven treatment-seeking participants (47 older, 60% female, and 60 younger, 50% female) with anxiety and mood disorders completed the Anxiety Disorders Interview Schedule and a symptom checklist to examine differences in symptom severity, symptom profiles and terms used to describe anxiety and mood. The findings indicated several key differences between the presentation and description of anxiety and depression in younger and older adults. Older adults with Social Phobia reported fearing a narrower range of social situations and less distress and interference. Older adults with Generalized Anxiety Disorder (GAD) reported less worry about interpersonal relationships and work/school than younger adults, however, there were no differences between age groups for behavioral symptoms endorsed. Further older adults reported phobia of lifts/small spaces more frequently than younger adults. Depressed older depressed adults also reported more anhedonia compared to younger adults, but no differences in terms of reported sadness were found. Finally, older and younger adults differed in their descriptions of symptoms with older adults describing anxiety as feeling stressed and tense, while younger adults described anxiety as feeling anxious, worried or nervous. Clinicians need to assess symptoms broadly to avoid missing the presence of anxiety and mood disorders especially in older adults.

Long-term outcomes in younger men following permanent prostate brachytherapy.

PubMed

Shapiro, Edan Y; Rais-Bahrami, Soroush; Morgenstern, Carol; Napolitano, Barbara; Richstone, Lee; Potters, Louis

2009-04-01

We reviewed the long-term outcomes in men undergoing permanent prostate brachytherapy with a focus on those presenting before age 60 years. Between 1992 and 2005 a total of 2,119 patients with clinical stage T1-T2, N0, M0 prostate cancer treated with permanent prostate brachytherapy were included in this study. Treatment regimens consisted of permanent prostate brachytherapy with or without hormone therapy, permanent prostate brachytherapy with external beam radiotherapy, or all 3 modalities. Biochemical recurrence was defined using the Phoenix definition. Multivariate analysis was performed to determine if age and/or other clinicopathological features were associated with disease progression. The Kaplan-Meier method was used to calculate rates of freedom from progression with the log rank test to compare patients younger than 60 vs 60 years or older. Median followup was 56.1 months. In the study population 237 patients were younger than 60 years at diagnosis (11%). The 5 and 10-year freedom from progression rates were 90.1% and 85.6%, respectively, for the entire population. Multivariate analysis demonstrated that prostate specific antigen (p <0.01), biopsy Gleason score (p <0.0001) and year of treatment (p <0.001) were associated with freedom from progression while age (p = 0.95) and clinical stage (p = 0.11) were not. There was no significant difference in freedom from progression between men younger than 60, or 60 years or older (log rank p = 0.46). In the younger cohort the 10-year freedom from progression for patients presenting with low, intermediate and high risk disease was 91.3%, 80.0% and 70.2% compared to 91.8%, 83.4% and 72.1%, respectively, for men 60 years or older. Our long-term results confirm favorable outcomes after permanent prostate brachytherapy in men younger than 60 years. Outcomes are impacted by disease related risk factors but not by age or clinical stage. Definitive treatment options for younger men with clinically localized prostate

Vegetation and climate variability in tropical and subtropical South America during the late Quaternary

NASA Astrophysics Data System (ADS)

Behling, H.

2013-05-01

Detailed palynological studies from different ecosystems in tropical and subtropical South America reflect interesting vegetation and climate dynamics, in particular during glacial and late glacial times. Records from ecosystems such as the Amazon rainforest, savanna, Caatinga, Atlantic rainforest, Araucaria forest and grasslands provide interesting insight of past climate variability. The influence of events such as Dansgaard-Oeschger, Heinnrich stadials, changes in the thermohaline circulation (THC) will be discussed. In particular the Younger Dryas (YD) period shows at different places distinct vegetational changes, revealing unexpected past climatic conditions.

Reconstructing lake evaporation history and the isotopic composition of precipitation by a coupled δ18O-δ2H biomarker approach

NASA Astrophysics Data System (ADS)

Hepp, Johannes; Tuthorn, Mario; Zech, Roland; Mügler, Ines; Schlütz, Frank; Zech, Wolfgang; Zech, Michael

2015-10-01

Over the past decades, δ18O and δ2H analyses of lacustrine sediments became an invaluable tool in paleohydrology and paleolimnology for reconstructing the isotopic composition of past lake water and precipitation. However, based on δ18O or δ2H records alone, it can be challenging to distinguish between changes of the precipitation signal and changes caused by evaporation. Here we propose a coupled δ18O-δ2H biomarker approach that provides the possibility to disentangle between these two factors. The isotopic composition of long chain n-alkanes (n-C25, n-C27, n-C29, n-C31) were analyzed in order to establish a 16 ka Late Glacial and Holocene δ2H record for the sediment archive of Lake Panch Pokhari in High Himalaya, Nepal. The δ2Hn-alkane record generally corroborates a previously established δ18Osugar record reporting on high values characterizing the deglaciation and the Older and the Younger Dryas, and low values characterizing the Bølling and the Allerød periods. Since the investigated n-alkane and sugar biomarkers are considered to be primarily of aquatic origin, they were used to reconstruct the isotopic composition of lake water. The reconstructed deuterium excess of lake water ranges from +57‰ to -85‰ and is shown to serve as proxy for the evaporation history of Lake Panch Pokhari. Lake desiccation during the deglaciation, the Older Dryas and the Younger Dryas is affirmed by a multi-proxy approach using the Hydrogen Index (HI) and the carbon to nitrogen ratio (C/N) as additional proxies for lake sediment organic matter mineralization. Furthermore, the coupled δ18O and δ2H approach allows disentangling the lake water isotopic enrichment from variations of the isotopic composition of precipitation. The reconstructed 16 ka δ18Oprecipitation record of Lake Panch Pokhari is well in agreement with the δ18O records of Chinese speleothems and presumably reflects the Indian Summer Monsoon variability.

Vaccination Patterns in Children After Autism Spectrum Disorder Diagnosis and in Their Younger Siblings.

PubMed

Zerbo, Ousseny; Modaressi, Sharareh; Goddard, Kristin; Lewis, Edwin; Fireman, Bruce H; Daley, Matthew F; Irving, Stephanie A; Jackson, Lisa A; Donahue, James G; Qian, Lei; Getahun, Darios; DeStefano, Frank; McNeil, Michael M; Klein, Nicola P

2018-05-01

In recent years, rates of vaccination have been declining. Whether this phenomenon disproportionately affects children with autism spectrum disorder (ASD) or their younger siblings is unknown. To investigate if children after receiving an ASD diagnosis obtain their remaining scheduled vaccines according to the Advisory Committee on Immunization Practices (ACIP) recommendations and to compare the vaccination patterns of younger siblings of children with ASD with the vaccination patterns of younger siblings of children without ASD. This investigation was a retrospective matched cohort study. The setting was 6 integrated health care delivery systems across the United States within the Vaccine Safety Datalink. Participants were children born between January 1, 1995, and September 30, 2010, and their younger siblings born between January 1, 1997, and September 30, 2014. The end of follow-up was September 30, 2015. Recommended childhood vaccines between ages 1 month and 12 years. The proportion of children who received all of their vaccine doses according to ACIP recommendations. The study included 3729 children with ASD (676 [18.1%] female), 592 907 children without ASD, and their respective younger siblings. Among children without ASD, 250 193 (42.2%) were female. For vaccines recommended between ages 4 and 6 years, children with ASD were significantly less likely to be fully vaccinated compared with children without ASD (adjusted rate ratio, 0.87; 95% CI, 0.85-0.88). Within each age category, vaccination rates were significantly lower among younger siblings of children with ASD compared with younger siblings of children without ASD. The adjusted rate ratios varied from 0.86 for siblings younger than 1 year to 0.96 for those 11 to 12 years old. Parents who had a child with ASD were more likely to refuse at least 1 recommended vaccine for that child's younger sibling and to limit the number of vaccines administered during the younger sibling's first year of life

Application of Alkenone 14C-Based chronostratigraphy in carbonate barren sediments on the Peru Margin.

NASA Astrophysics Data System (ADS)

Higginson, M. J.; Altabet, M. A.; Herbert, T. D.

2003-04-01

the timing of the Younger Dryas. We presume that the enlarged SST amplitude of these sites comes from the sensitivity of the Peru margin to the dominant upwelling signal and its proximity to the Andes, from which there is evidence for a Younger Dryas response. The appearance of a Bolling-Allerod/Younger Dryas SST reversal consistent with published dates is further verification of our chronostratigraphic methods.

Timing of last deglaciation in the Cantabrian Mountains (Iberian Peninsula; North Atlantic Region) based on in situ-produced 10Be exposure dating

NASA Astrophysics Data System (ADS)

Rodríguez-Rodríguez, Laura; Jiménez-Sánchez, Montserrat; Domínguez-Cuesta, María José; Rinterknecht, Vincent; Pallàs, Raimon; Aumaître, Georges; Bourlès, Didier L.; Keddadouche, Karim; Aster Team

2017-09-01

The Last Glacial Termination led to major changes in ice sheet coverage that disrupted global patterns of atmosphere and ocean circulation. Paleoclimate records from Iberia suggest that westerly episodes played a key role in driving heterogeneous climate in the North Atlantic Region. We used 10Be Cosmic Ray Exposure (CRE) dating to explore the glacier response of small mountain glaciers (ca. 5 km2) that developed on the northern slope of the Cantabrian Mountains (Iberian Peninsula), an area directly under the influence of the Atlantic westerly winds. We analyzed twenty boulders from three moraines and one rock glacier arranged as a recessional sequence preserved between 1150 and 1540 m above sea level (a.s.l.) in the Monasterio valley (Redes Natural Park). Results complement previous chronologic data based on radiocarbon and optically stimulated luminescence from the Monasterio valley, which suggest a local Glacial Maximum (local GM) prior to 33 ka BP and a long-standing glacier advance at 24 ka coeval to the global Last Glacial Maximum (LGM). Resultant 10Be CRE ages suggest a progressive retreat and thinning of the Monasterio glacier over the time interval 18.1-16.7 ka. This response is coeval with the Heinrich Stadial 1, an extremely cold and dry climate episode initiated by a weakening of the Atlantic Meridional Overturning Circulation (AMOC). Glacier recession continued through the Bølling/Allerød period as indicate the minimum exposure ages obtained from a cirque moraine and a rock glacier nested within this moraine, which yielded ages of 14.0 and 13.0 ka, respectively. Together, they suggest that the Monasterio glacier experienced a gradual transition from glacier to rock glacier activity as the AMOC started to strengthen again. Glacial evidence ascribable to the Younger Dryas cooling was not dated in the Monasterio valley, but might have occurred at higher elevations than evidence dated in this work. The evolution of former glaciers documented in the

Time constraints for post-LGM landscape response to deglaciation in Val Viola, Central Italian Alps

NASA Astrophysics Data System (ADS)

Scotti, Riccardo; Brardinoni, Francesco; Crosta, Giovanni Battista; Cola, Giuseppe; Mair, Volkmar

2017-12-01

Across the northern European Alps, a long tradition of Quaternary studies has constrained post-LGM (Last Glacial Maximum) landscape history. The same picture remains largely unknown for the southern portion of the orogen. In this work, starting from existing 10Be exposure dating of three boulders in Val Viola, Central Italian Alps, we present the first detailed, post-LGM reconstruction of landscape (i.e., glacial, periglacial and paraglacial) response south of the Alpine divide. We pursue this task through Schmidt-hammer exposure-age dating (SHD) at 34 sites including moraines, rock glaciers, protalus ramparts, rock avalanche deposits and talus cones. In addition, based on the mapping of preserved moraines and on the numerical SHD ages, we reconstruct the glacier extent of four different stadials, including Egesen I (13.1 ± 1.1 ka), Egesen II (12.3 ± 0.6 ka), Kartell (11.0 ± 1.4 ka) and Kromer (9.7 ± 1.4 ka), whose chronologies agree with available counterparts from north of the Alpine divide. Results show that Equilibrium Line Altitude depressions (ΔELAs) associated to Younger Dryas and Early Holocene stadials are smaller than documented at most available sites in the northern Alps. These findings not only support the hypothesis of a dominant north westerly atmospheric circulation during the Younger Dryas, but also suggest that this pattern could have lasted until the Early Holocene. SHD ages on rock glaciers and protalus ramparts indicate that favourable conditions to periglacial landform development occurred during the Younger Dryas (12.7 ± 1.1 ka), on the valley slopes above the glacier, as well as in newly de-glaciated areas, during the Early Holocene (10.7 ± 1.3 and 8.8 ± 1.8 ka). The currently active rock glacier started to develop before 3.7 ± 0.8 ka and can be associated to the Löbben oscillation. Four of the five rock avalanches dated in Val Viola cluster within the Early Holocene, in correspondence of an atmospheric warming phase. By contrast

Rapid Vegetational Change in Coastal North America: The Response to Climate Since the LGM

NASA Technical Reports Server (NTRS)

Peteet, Dorothy; Kneller, Margaret

1999-01-01

The late-glacial interval provided rapid shifts in climate which are mirrored by dramatic vegetational changes in North America. Through a transect of lake and mire sites from Connecticut to Virginia on the east coast and Kodiak Island on the western coast, we trace the warming following the LGM with the response of forests and tundra. A brief cold reversal in Virginia is seen from 12,260 to 12,200. The subsequent longer and extreme Younger Dryas event is marked in the southern New England - New Jersey region by dramatic boreal and deciduous forest changes. In the southeastern US, forests also change rapidly, with hemlock forest expansion suggesting increased moisture. In Kodiak Island, the warm, moist tundra of the Bolling/Allerod is replaced by colder, windswept Empetrum-dominated tundra during the Younger Dryas. The Pleistocene/Holocene shift in vegetation is remarkably pronounced in eastern North America as well as the Alaskan coastline. Response time of vegetation to climate change appears to be on the order of decades throughout these coastal locations, probably because of the proximity of sites to important ecotonal boundaries, and the magnitude of the events. Even in Virginia's Holocene record, a cold reversal inferred from increases in spruce and fir is noted at 7500 C14 yr BP. This response of the forests to a short-lived cooling shows the sensitivity of the biosphere to a rapid climate shifts.

Evidence for early postglacial warming in Mount Field National Park, Tasmania

NASA Astrophysics Data System (ADS)

Rees, Andrew B. H.; Cwynar, Les C.

2010-02-01

Situated between the Western Pacific Warm Pool to the north and Antarctica to the south, Tasmania is an ideal location to study both postglacial and Holocene paleoclimates. Few well-dated, quantitative temperature reconstructions exist for the region so that important questions about the occurrence and magnitude of events, such as the Antarctic Cold Reversal and Younger Dryas, in Tasmania remain unanswered. Here, we provide chironomid-based reconstructions of temperature of the warmest quarter (TWARM) for two small subalpine lakes, Eagle and Platypus Tarns, Mount Field National Park. Shortly after deglaciation, TWARM reached modern values by approximately 15 000 cal a BP and remained high until 13 000 cal a BP after which temperatures began to cool steadily, reaching a minimum by 11 100-10 000 cal a BP. These results are consistent with sea surface temperature (SST) reconstructions from south of Tasmania but are in stark contrast to temperature inferences drawn from vegetation reconstructions based on pollen data that indicate cool initial temperatures followed by a broad warm period between 11 600-6800 cal a BP (10 000-6000 14C a BP). The chironomid record broadly matches the summer insolation curve whereas the vegetation record and associated climate inferences mirror winter insolation. The Antarctic Cold Reversal and Younger Dryas cold events are not evident in the chironomid-inferred temperatures, but the Antarctic Cold Reversal is evident in the loss-on-ignition curves.

Termination of the Last Glaciation in the Iberian Peninsula Inferred from the Pollen Sequence of Quintanar de la Sierra

NASA Astrophysics Data System (ADS)

Peñalba, M. Cristina; Arnold, Maurice; Guiot, Joël; Duplessy, Jean-Claude; de Beaulieu, Jacques-Louis

1997-09-01

A 4.5-m-thick late-glacial pollen sequence, supported by 17 AMS 14C dates, has been investigated at the Quintanar de la Sierra marshland (Iberian cordillera, north-central Spain). Pollen zones were defined that correspond to successive phases in vegetation history during the end of the Late Würm, late-glacial interstade, and Younger Dryas periods. A transfer function approach has been adopted to derive quantitative climate estimates from the pollen assemblage data. A first expansion of Juniperusand Hippophae,about 13,500 14C yr B.P., indicates the beginning of the late-glacial interstade which is characterized by a Juniperus-Betula-Pinussuccession that suggests higher temperatures and moisture than during full-glacial time. The Younger Dryas interval is recorded by a 120-cm-thick sediment unit that is dominated by herbaceous pollen. Transfer function estimates suggest that the climate during this period was cold, with low precipitation during most of the year, although not in summer. The Holocene arboreal recolonization in the area started about 10,000 14C yr B.P., with a renewed Juniperus-Betula-Pinussuccession related to a strong increase in annual temperature and precipitation. The start of this process was synchronous with mean sea-surface temperature changes, as recorded from the nearby SU 81-18 marine core. The strong affinity with other European late-glacial pollen sequences demonstrates that the pattern of climatic changes during the last glacial-interglacial transition was similar in both northwestern and southwestern Europe.

Chronicles from the End of the Word: the Holocene climate variability in Tierra del Fuego

NASA Astrophysics Data System (ADS)

Waldmann, N.; Ariztegui, D.; Anselmetti, F.; Austin, J.; Moy, C.; Borromei, A.; Coronato, A.; Recasens, C.; Dunbar, R.; Martinez, M.; Olivera, D.

2008-12-01

Latest advances in the chronology and environmental importance of Antarctic paleoclimate records point towards a larger heterogeneity than previously thought. Thus, realistic inter-hemispheric correlations rely in the development of a tight array of well constrained records with a dense latitudinal coverage. Climatic records from southernmost Patagonia are hence critical corner-stones to link these Antarctic paleoclimatic archives with their South American counterparts. At 55° S on the Island of Tierra del Fuego, Lago Fagnano is located in one of the most substantially and extensively glaciated regions of southernmost South America during the Late Pleistocene. This elongated lake is the largest (~110 km long) and southernmost non-ice covered water body in the world. Existing on-shore geomorphological reconstructions combined with new lacustrine subsurface data, allowed us to better constrain the magnitude and chronology of the Fagnano glacier fluctuations since the LGM. The former Fagnano glacier flowed eastwards from the Darwin Cordillera fed by more than 50 tributary glaciers. The glacier spread over the low ranges and lowlands through three different lobes and was drained by four main outwash basins directly into the Atlantic Ocean. During the maximum ice-expansion, the ice-covered area was ca. 4000 km2 with a maximum length of ca. 132 km. A set of submerged frontal moraines covered by lacustrine infilling identified in the seismic survey suggests occasional eastward re-advances of the paleo-glacier within the overall westward deglaciation pattern. These re-advances may correspond to cold events such as the Antarctic Cold Reversal (ACR), the Huelmo- Mascardi Cold Event (HMCE) and/or the Younger Dryas Chronozone (YDC). The ongoing development of a robust age model blended with a multi-proxy dataset will potentially clarify remaining controversial issues dealing with the geographical extension and chronology of these cold episodes during the last deglaciation. A

Destination memory in social interaction: better memory for older than for younger destinations in normal aging?

PubMed

El Haj, Mohamad; Raffard, Stéphane; Fasotti, Luciano; Allain, Philippe

2018-05-01

Destination memory, a memory component allowing the attribution of information to its appropriate receiver (e.g., to whom did I lend my pen?), is compromised in normal aging. The present paper investigated whether older adults might show better memory for older destinations than for younger destinations. This hypothesis is based on empirical research showing better memory for older faces than for younger faces in older adults. Forty-one older adults and 44 younger adults were asked to tell proverbs to older and younger destinations (i.e., coloured faces). On a later recognition test, participants had to decide whether they had previously told some proverb to an older/younger destination or not. Prior to this task, participants reported their frequency of contact with other-age groups. The results showed lower destination memory in older adults than in younger adults. Interestingly, older adults displayed better memory for older than for younger destinations. The opposite pattern was seen in younger adults. The low memory for younger destinations, as observed in older adults, was significantly correlated with limited exposure to younger individuals. These findings suggest that for older adults, the social experience can play a crucial role in the destination memory, at least as far as exposure to other-age groups is concerned.

Climatic oscillations in central Italy during the Last Glacial-Holocene transition: the record from Lake Accesa

NASA Astrophysics Data System (ADS)

Magny, Michel; de Beaulieu, Jacques-Louis; Drescher-Schneider, Ruth; Vannière, Boris; Walter-Simonnet, Anne-Véronique; Millet, Laurent; Bossuet, Gilles; Peyron, Odile

2006-05-01

This paper presents an event stratigraphy based on data documenting the history of vegetation cover, lake-level changes and fire frequency, as well as volcanic eruptions, over the Last Glacial-early Holocene transition from a terrestrial sediment sequence recovered at Lake Accesa in Tuscany (north-central Italy). On the basis of an age-depth model inferred from 13 radiocarbon dates and six tephra horizons, the Oldest Dryas-Bølling warming event was dated to ca. 14 560 cal. yr BP and the Younger Dryas event to ca. 12 700-11 650 cal. yr BP. Four sub-millennial scale cooling phases were recognised from pollen data at ca. 14 300-14 200, 13 900-13 700, 13 400-13 100 and 11 350-11 150 cal.yrBP. The last three may be Mediterranean equivalents to the Older Dryas (GI-1d), Intra-Allerød (GI-1b) and Preboreal Oscillation (PBO) cooling events defined from the GRIP ice-core and indicate strong climatic linkages between the North Atlantic and Mediterranean areas during the last Termination. The first may correspond to Intra-Bølling cold oscillations registered by various palaeoclimatic records in the North Atlantic region. The lake-level record shows that the sub-millennial scale climatic oscillations which punctuated the last deglaciation were associated in central Italy with different successive patterns of hydrological changes from the Bølling warming to the 8.2ka cold reversal. Copyright

Late Glacial vegetation reconstruction based on leaf waxes from the Gemündener Maar, Germany

NASA Astrophysics Data System (ADS)

Wüthrich, Lorenz; Lutz, Selina; Zech, Michael; Hepp, Johannes; Sirocko, Frank; Zech, Roland

2015-04-01

Lake sediments are valuable archives for the reconstruction of past changes in climate and vegetation. In the present study, we analyse samples from the Gemündener Maar, a lake situated in the western Eiffel, Germany, for their leaf wax composition: In the bottom part of the core, corresponding to the Oldest Dryas (i.e. older than ~15 ka), n-alkanes have a high average chain length (ACL), which points to a vegetation dominated by grass. During the Bölling/Alleröd, a decrease of the ACL can be interpreted as signal of more deciduous trees. During the Younger Dryas (~12.8 to 11.5 ka), the ACL increases again. Trees probably became again less abundant, before finally, the ACL records the return of deciduous trees during the early Holocene. In general, the total concentrations of both, n-alkanes and sugar biomarkers are high enough to measure compound-specific isotopes on n-alkanes (deuterium) and sugars (18-O). Combined, these two isotopes might help to obtain more information about the relative humidity and mean air temperature during the late glacial.

Angle closure in younger patients.

PubMed Central

Chang, Brian M; Liebmann, Jeffrey M; Ritch, Robert

2002-01-01

PURPOSE: Angle-closure glaucoma is rare in children and young adults. Only scattered cases associated with specific clinical entities have been reported. We evaluated the findings in patients in our database aged 40 or younger with angle closure. METHODS: Our database was searched for patients with angle closure who were 40 years old or younger. Data recorded included age at initial consultation; age at the time of diagnosis; gender; results of slit-lamp examination, gonioscopy, and ultrasound biomicroscopy (from 1993 onward); clinical diagnosis; and therapy. Patients with previous incisional surgery were excluded, as were patients with anterior chamber proliferative mechanisms leading to angle closure. RESULTS: Sixty-seven patients (49 females, 18 males) met entry criteria. Mean age (+/- SD) at the time of consultation was 34.4 +/- 9.4 years (range, 3-68 years). Diagnoses included plateau iris syndrome (35 patients), iridociliary cysts (8 patients), retinopathy of prematurity (7 patients), uveitis (5 patients), isolated nanophthalmos (3 patients), relative pupillary block (2 patients), Weill-Marchesani syndrome (3 patients), and 1 patient each with Marfan syndrome, miotic-induced angle closure, persistent hyperplastic primary vitreous, and idiopathic lens subluxation. CONCLUSION: The etiology of angle closure in young persons is different from that in the older population and is typically associated with structural or developmental ocular anomalies rather than relative pupillary block. Following laser iridotomy, these eyes should be monitored for recurrent angle closure and the need for additional laser or incisional surgical intervention. PMID:12545694

Older and younger adults differently judge the similarity between negative affect terms.

PubMed

Ready, Rebecca E; Santorelli, Gennarina D; Mather, Molly A

2018-01-02

Theoretical models of aging suggest changes across the adult lifespan in the capacity to differentiate emotions. Greater emotion differentiation is associated with advantages in terms of emotion regulation and emotion resiliency. This study utilized a novel method that directly measures judgments of affect differentiation and does not confound affective experience with knowledge about affect terms. Theoretical predictions that older adults would distinguish more between affect terms than younger persons were tested. Older (n = 27; aged 60-92) and younger (n = 56; aged 18-32) adults rated the difference versus similarity of 16 affect terms from the Kessler and Staudinger ( 2009 ) scales; each of the 16 items was paired with every other item for a total of 120 ratings. Participants provided self-reports of trait emotions, alexithymia, and depressive symptoms. Older adults significantly differentiated more between low arousal and high arousal negative affect (NA) items than younger persons. Depressive symptoms were associated with similarity ratings across and within valence and arousal. Findings offer partial support for theoretical predictions that older adults differentiate more between affect terms than younger persons. To the extent that differentiating between negative affects can aid in emotion regulation, older adults may have an advantage over younger persons. Future research should investigate mechanisms that underlie age group differences in emotion differentiation.

Hypocaloric, high-protein nutrition therapy in older vs younger critically ill patients with obesity.

PubMed

Dickerson, Roland N; Medling, Theresa L; Smith, Ashley C; Maish, George O; Croce, Martin A; Minard, Gayle; Brown, Rex O

2013-01-01

Older patients require more protein than younger patients to achieve anabolism, but age-associated renal dysfunction may limit the amount of protein that can be safely provided. This study examined whether older, critically ill trauma patients with obesity can safely achieve nitrogen equilibrium and have positive clinical outcomes similar to younger obese patients during hypocaloric, high-protein nutrition therapy. Adult patients with traumatic injury and obesity (body mass index [BMI] >30 kg/m(2)), admitted to the Presley Trauma Center from January 2009 to April 2011, were evaluated. Patients were targeted to receive hypocaloric, high-protein nutrition therapy (<25 kcal/kg ideal body weight [IBW]/d and >2 g/kg IBW/d of protein) for >10 days. Patients were stratified as older (≥60 years) or younger (18-59 years). Seventy-four patients (33 older, 41 younger) were studied. Older and younger patients were similar in BMI and injury severity. When given isonitrogenous regimens (2.3 ± 0.2 g/kg IBW/d), nitrogen balance was similar between older and younger patients (-3.2 ± 5.7 g/d vs -4.9 ± 9.0 g/d; P = .363). Older patients experienced a greater mean serum urea nitrogen concentration than younger patients (30 ± 14 mg/dL vs 20 ± 9 mg/dL; P = .001) during nutrition therapy. Clinical outcomes were not different between groups. Older critically ill trauma patients exhibited an equivalent net protein response as younger patients during hypocaloric, high-protein nutrition therapy. Older patients are at greater risk for developing azotemia. Close monitoring is warranted.

Intelligibility of emotional speech in younger and older adults.

PubMed

Dupuis, Kate; Pichora-Fuller, M Kathleen

2014-01-01

Little is known about the influence of vocal emotions on speech understanding. Word recognition accuracy for stimuli spoken to portray seven emotions (anger, disgust, fear, sadness, neutral, happiness, and pleasant surprise) was tested in younger and older listeners. Emotions were presented in either mixed (heterogeneous emotions mixed in a list) or blocked (homogeneous emotion blocked in a list) conditions. Three main hypotheses were tested. First, vocal emotion affects word recognition accuracy; specifically, portrayals of fear enhance word recognition accuracy because listeners orient to threatening information and/or distinctive acoustical cues such as high pitch mean and variation. Second, older listeners recognize words less accurately than younger listeners, but the effects of different emotions on intelligibility are similar across age groups. Third, blocking emotions in list results in better word recognition accuracy, especially for older listeners, and reduces the effect of emotion on intelligibility because as listeners develop expectations about vocal emotion, the allocation of processing resources can shift from emotional to lexical processing. Emotion was the within-subjects variable: all participants heard speech stimuli consisting of a carrier phrase followed by a target word spoken by either a younger or an older talker, with an equal number of stimuli portraying each of seven vocal emotions. The speech was presented in multi-talker babble at signal to noise ratios adjusted for each talker and each listener age group. Listener age (younger, older), condition (mixed, blocked), and talker (younger, older) were the main between-subjects variables. Fifty-six students (Mage= 18.3 years) were recruited from an undergraduate psychology course; 56 older adults (Mage= 72.3 years) were recruited from a volunteer pool. All participants had clinically normal pure-tone audiometric thresholds at frequencies ≤3000 Hz. There were significant main effects of

CDC Vital Signs: Preventing Pregnancies in Younger Teens

MedlinePlus

... media and digital technology (e.g., cell phones, computers, tablets). Younger teens can Know both they and ... and condoms correctly every time. Top of Page Science Behind the Issue MMWR Science Clips Related Pages ...

The experience of demanding work environments in younger workers.

PubMed

Winding, T N; Labriola, M; Nohr, E A; Andersen, J H

2015-06-01

Investigating whether certain individual or background characteristics are associated with an increased risk of experiencing an excessively demanding work environment in younger workers may help to reduce future inequality in health and maximize their labour market participation. To describe the work environment of Danish 20- to 21-year olds and to investigate the influence of family socioeconomic background and individual characteristics at age 14-15 on later experience of physical and psychosocial work environments. We obtained information on subjects' school performance, vulnerability, health and parental socioeconomic status from registers and a questionnaire completed in 2004. A questionnaire concerning eight measures of subjects' psychosocial and physical work environment in 2010 was used to determine the outcomes of interest. The study population consisted of 679 younger workers aged 20-21. The psychosocial work environment was in general good but younger workers experienced more demanding physical work than the general working population. Overall, individual as well as family factors had a limited impact on their assessment of the work environment. Low self-esteem at age 14-15 was associated with experiencing high demands and lack of trust and fairness at work, whereas low parental socioeconomic status was associated with a demanding physical work environment. This study showed a social gradient in experiencing a demanding physical work environment at age 20-21. The psychosocial work environment experienced by younger workers was generally good, but vulnerable young people may need special attention to protect them from or prepare them for psychosocially demanding jobs later in life. © The Author 2015. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Both younger and older adults have difficulty updating emotional memories.

PubMed

Nashiro, Kaoru; Sakaki, Michiko; Huffman, Derek; Mather, Mara

2013-03-01

The main purpose of the study was to examine whether emotion impairs associative memory for previously seen items in older adults, as previously observed in younger adults. Thirty-two younger adults and 32 older adults participated. The experiment consisted of 2 parts. In Part 1, participants learned picture-object associations for negative and neutral pictures. In Part 2, they learned picture-location associations for negative and neutral pictures; half of these pictures were seen in Part 1 whereas the other half were new. The dependent measure was how many locations of negative versus neutral items in the new versus old categories participants remembered in Part 2. Both groups had more difficulty learning the locations of old negative pictures than of new negative pictures. However, this pattern was not observed for neutral items. Despite the fact that older adults showed overall decline in associative memory, the impairing effect of emotion on updating associative memory was similar between younger and older adults.

Computer-based training for safety: comparing methods with older and younger workers.

PubMed

Wallen, Erik S; Mulloy, Karen B

2006-01-01

Computer-based safety training is becoming more common and is being delivered to an increasingly aging workforce. Aging results in a number of changes that make it more difficult to learn from certain types of computer-based training. Instructional designs derived from cognitive learning theories may overcome some of these difficulties. Three versions of computer-based respiratory safety training were shown to older and younger workers who then took a high and a low level learning test. Younger workers did better overall. Both older and younger workers did best with the version containing text with pictures and audio narration. Computer-based training with pictures and audio narration may be beneficial for workers over 45 years of age. Computer-based safety training has advantages but workers of different ages may benefit differently. Computer-based safety programs should be designed and selected based on their ability to effectively train older as well as younger learners.

Infliximab therapy in pediatric patients 7 years of age and younger.

PubMed

Kelsen, Judith R; Grossman, Andrew B; Pauly-Hubbard, Helen; Gupta, Kernika; Baldassano, Robert N; Mamula, Petar

2014-12-01

Infliximab (IFX) is efficacious for induction and maintenance of remission in pediatric patients with moderate-to-severe inflammatory bowel disease (IBD). It has, however, not been studied in patients 7 years old and younger. Our aim was to characterize efficacy and safety of IFX therapy in this cohort. This was a retrospective study of patients with IBD ages 7 years and younger, treated with IFX between 1999 and 2011. Medical records were reviewed for age of diagnosis, disease phenotype, therapy, surgery, IFX infusion dates, dose, and intervals. Outcome measures included physician global assessment, corticosteroid requirement, and adverse events. Thirty-three children (ages 2.4-7 years) were included. Twenty patients had Crohn disease, 4 had ulcerative colitis, and 9 had indeterminate colitis. Maintenance of IFX therapy at 1, 2, and 3 years was 36%, 18%, and 12%, respectively. Patients of age 5 years and younger had the lowest rates of maintenance of therapy at 25% at year 1, and 10% at years 2 and 3 combined. Nine percent of all of the patients demonstrated response measured by the physician global assessment and were steroid free at 1 year. There were 8 infusion reactions. There were no malignancies, serious infections, or deaths. IFX demonstrated a modest response rate and a low steroid-sparing effect in patients with IBD 7 years old and younger. Although this is a limited study, there appears to be a trend for decreased sustained efficacy with IFX in this age group, particularly in children 5 years old and younger, when compared with the previously published literature in older children.

Diffusion of Technology: Frequency of Use for Younger and Older Adults

PubMed Central

Olson, Katherine E.; O’Brien, Marita A.; Rogers, Wendy A.; Charness, Neil

2012-01-01

Objectives When we think of technology-savvy consumers, older adults are typically not the first persons that come to mind. The common misconception is that older adults do not want to use or cannot use technology. But for an increasing number of older adults, this is not true (Pew Internet and American Life Project, 2003). Older adults do use technologies similar to their younger counterparts, but perhaps at different usage rates. Previous research has identified that there may be subgroups of older adults, “Silver Surfers”, whose adoption patterns mimic younger adults (Pew Internet and American Life Project, 2003). Much of the previous research on age-related differences in technology usage has only investigated usage broadly -- from a “used” or “not used” standpoint. The present study investigated age-related differences in overall usage of technologies, as well as frequency of technology usage (i.e., never, occasional, or frequent). Methods The data were gathered through a questionnaire from younger adults (N=430) and older adults (N=251) in three geographically separate and ethnically diverse areas of the United States. Results We found that younger adults use a greater breadth of technologies than older adults. However, age-related differences in usage and the frequency of use depend on the technology domain. Conclusion This paper presents technology usage and frequency data to highlight age-related differences and similarities. The results provide insights into older and younger adults’ technology-use patterns, which in turn provide a basis for expectations about knowledge differences. Designers and trainers can benefit from understanding experience and knowledge differences. PMID:22685360

Lung cancer in patients younger than 40 years in a multiracial Asian country.

PubMed

Liam, C K; Lim, K H; Wong, C M

2000-12-01

This study aimed to determine whether the clinicopathological features of lung cancer in patients younger than 40 years differ from that of older patients in an Asian country. We undertook a review of the clinicopathological data of all patients with confirmed primary lung cancer at the Department of Medicine, University of Malaya Medical Centre, Kuala Lumpur, Malaysia, from October 1991 to September 1999. Of the 580 patients with lung cancer, 36 (6.2%; 23 males, 13 females) were 21-39 years old at diagnosis. The percentage of people who had never smoked was higher among the younger patients (58.3% vs 19.1%, P < 0.001). Although adenocarcinoma was the most common cell type in both groups, its incidence was higher in the younger patients (24/36 (66.7%) vs 228/544 (41.9%), P = 0.007). The mean World Health Organization performance status at presentation was worse in the younger patients (2.4 vs 2, P = 0.007). In the case of non-small cell lung cancer, all the younger patients presented with either stage IIIb or metastatic disease compared to 77.2% of the older patients (P < 0.001). Younger lung cancer patients were more likely than older patients to have never smoked, to have adenocarcinoma, and to present with poorer performance status and with more advanced-stage non-small cell lung cancer.

Association Between Indoor Tanning and Melanoma in Younger Men and Women.

PubMed

Lazovich, DeAnn; Isaksson Vogel, Rachel; Weinstock, Martin A; Nelson, Heather H; Ahmed, Rehana L; Berwick, Marianne

2016-03-01

In the United States and Minnesota, melanoma incidence is rising more steeply among women than men younger than 50 years. To our knowledge, no study has examined age- and sex-specific associations between indoor tanning and melanoma to determine if these trends could be due to greater indoor tanning use among younger women. To examine associations between indoor tanning and melanoma among men and women younger than 50 years. Population-based case-control study conducted in Minnesota of 681 patients (465 [68.3%] women) diagnosed as having melanoma between 2004 and 2007, and 654 controls (446 [68.2%] women), ages 25 to 49 years. Indoor tanning, defined as any use, first age of use, and total sessions. Crude and adjusted odds ratios (ORs) and 95% CIs were calculated for melanoma in relation to indoor tanning exposure for men and women by diagnosis or reference age (<30, 30-39, 40-49 years). Sex-specific associations for indoor tanning and melanoma by anatomic site were examined. Compared with women aged 40 to 49 years, women younger than 40 years initiated indoor tanning at a younger age (16 vs 25 years, P < .001) and reported more frequent indoor tanning (median number of sessions, 100 vs 40, P < .001). Women younger than 30 years were 6 times more likely to be in the case than the control group if they tanned indoors (crude OR, 6.0; 95% CI, 1.3-28.5). Odds ratios were also significantly elevated among women, ages 30 to 49 years (adjusted OR, 3.5; 95% CI, 1.2-9.7 for women 30-39 years; adjusted OR, 2.3; 95% CI, 1.4-3.6 for women 40-49 years); a dose response was observed among women regardless of age. Among men, results by age were inconsistent. The strongest OR for indoor tanning by anatomic site was for melanomas arising on the trunk of women (adjusted OR, 3.7; 95% CI, 1.9-7.2). Indoor tanning is a likely factor for the steeper increase in melanoma rates in the United States among younger women compared with men, given the timing of when women initiated indoor

Limnocytherid Ostracod Paleoecology and Stable Isotope Chemistry: Evidence of Climate Change Derived From Lough Monreagh Sediment, Western Ireland

NASA Astrophysics Data System (ADS)

Mc Kenzie, S. M.; Patterson, W. P.; Holmden, C.; Tibert, N. E.

2008-12-01

Biota preserved in marl lakes of western Ireland represent an excellent record of climatic variability in Western Europe and the North Atlantic Region. Oxygen isotope values of lacustrine biota conflate source precipitation and temperature variability while carbon isotope values serve as a proxy for Late Pleistocene and Early Holocene changes in vegetation and lake carbon cycling. Blanket bog carbonate sediments from Lough Monreagh in County Clare, Ireland, contain abundant ostracoda instars of Limnocytherina sanctipatricii and Metacypris cordata that were analyzed for stable oxygen and carbon isotope values. Basal marl (extrapolated age 18.3-17.9Kyr) contains an interval of benthic, cold water (4-5°C), Linmocytherina sanctipatricii with high δ13C values (-1 to +1‰VPDB) and low δ18O values (-7‰VPDB) suggesting Viséan bedrock control of lake water carbon chemistry and a moisture source with low δ18O values. This Limnocytherid bed represents a time when lake waters warmed to ~4°C (the preferred temperature for this species). Limnocytherina sanctipatricii make a second appearance at ~15.1 Kyr, in advance of Younger Dryas cold period represented by a clay layer in the core. They persist until 12.8Kyr when temperatures presumably became too cool for this species. As before, the ostracoda exhibit high δ13C values (0 to +2‰VPDB) through this period indicating relatively little terrestrial vegetation between deglaciation and the Younger Dryas. However, δ18O values are much higher than before (0 to - 3‰VPDB) indicating that the moisture source has changed. Limnocytherids return for a third time at 11.7Kyr, immediately following the Younger Dryas cold interval, when the climate had warmed enough to allow for recolonization. Their reappearance was short lived, however, and by 11.3Kyr steadily increasing temperatures caused their decline, while at the same time allowing for colonization by warm-water Paracandona euplectella and other Candonids. Lower δ13C and

[Characteristics of emergency poisoning cases in elderly versus younger patients].

PubMed

Supervía Caparrós, August; Pallàs Villaronga, Oriol; Clemente Rodríguez, Carlos; Aranda Cárdenas, María Dolores; Pi-Figueras Valls, María; Cirera Lorenzo, Isabel

2017-10-01

To compare cases of poisoning according to age to detect differences in frequency of visits to the emergency department, patient characteristics, case management, and immediate outcome in terms of related mortality. Descriptive study of a retrospective series of patients who visited a university hospital emergency department for treatment of poisoning between 2009 and 2014. We collected patient characteristics and data related to the event, case management, and poisoning-related death. Patients were grouped according to age (cut-off 65 y). Of a total of 3847 poisoning episodes, 341 (8.9%) were in patients aged 65 years or older. The percentage of women among these older patients (61.3%) was greater than among younger patients (36.3%; P<.001). Poisoning was accidental in older patients more often than younger ones (64.4% vs 9.5%, respectively; P<.001), occurred more often in the home (82.1% vs 37%, P<.001), and more often required active treatment (73.3% vs 57.4%; P<.001) and admission to hospital (21.4% vs 7.3%, P<.001). The related mortality rate was also higher in the older patients (2.1% vs 0.1% in younger patients, P<.001). The percentage of poisonings in patients aged 65 years or older is not negligible. Poisoning in patients of advanced age tends to be accidental and take place in the home. Older patients more often require active treatment and hospital admission; poisoning-related death is more common in older patients than younger ones.

Understanding the effect of workload on automation use for younger and older adults.

PubMed

McBride, Sara E; Rogers, Wendy A; Fisk, Arthur D

2011-12-01

This study examined how individuals, younger and older, interacted with an imperfect automated system. The impact of workload on performance and automation use was also investigated. Automation is used in situations characterized by varying levels of workload. As automated systems spread to domains such as transportation and the home, a diverse population of users will interact with automation. Research is needed to understand how different segments of the population use automation. Workload was systematically manipulated to create three levels (low, moderate, high) in a dual-task scenario in which participants interacted with a 70% reliable automated aid. Two experiments were conducted to assess automation use for younger and older adults. Both younger and older adults relied on the automation more than they complied with it. Among younger adults, high workload led to poorer performance and higher compliance, even when that compliance was detrimental. Older adults' performance was negatively affected by workload, but their compliance and reliance were unaffected. Younger and older adults were both able to use and double-check an imperfect automated system. Workload affected how younger adults complied with automation, particularly with regard to detecting automation false alarms. Older adults tended to comply and rely at fairly high rates overall, and this did not change with increased workload. Training programs for imperfect automated systems should vary workload and provide feedback about error types, and strategies for identifying errors. The ability to identify automation errors varies across individuals, thereby necessitating training.

Reducing the framing effect in older and younger adults by encouraging analytic processing.

PubMed

Thomas, Ayanna K; Millar, Peter R

2012-03-01

The present study explored whether the framing effect could be reduced in older and younger adults using techniques that influenced the accessibility of information relevant to the decision-making processing. Accessibility was manipulated indirectly in Experiment 1 by having participants engage in concurrent tasks, and directly in Experiment 2, through an instructions manipulation that required participants to maintain a goal of analytic processing throughout the experimental trial. We tested 120 older and 120 younger adults in Experiment 1. Participants completed 28 decision trials while concurrently either performing a probability calculation task or a memory task. In Experiment 2, we tested 136 older and 136 younger adults. Participants completed 48 decision trials after either having been instructed to "think like a scientist" or base decisions on "gut reactions." Results demonstrated that the framing effect was reduced in older and younger adults in the probability calculation task in Experiment 1 and under the "think like a scientist" instructions manipulation in Experiment 2. These results suggest that when information relevant to unbiased decision making was made more accessible, both older and younger adults were able to reduce susceptibility to the framing effect.

Evaluation of a workplace engagement project for people with younger onset dementia.

PubMed

Robertson, Jacinta; Evans, David

2015-08-01

In 2011, a workplace project was established to provide a small group of people who had younger onset dementia with the opportunity to return to the workplace. The project sought to explore the feasibility and safety of engaging these younger people in workplace activities if an appropriate framework of support was provided. Opportunities to engage in meaningful activities are quite limited for younger people with dementia because services are targeted at an older client population. A qualitative exploratory approach was used for the project evaluation. Participants were people who were 65 years or younger and had a diagnosis of dementia. They attended a large metropolitan hardware store one day per week and worked beside a store employee for a four hour work shift. Evaluation of the project included observation of participant's engagement in the workplace, adverse events and a qualitative analysis that used participant-nominated good project outcomes. Nine people with a mean age of 58·8 years participated in the project. Six of these participants have been engaged at the workplace for more than two years. All participants were able to gain the skills needed to complete their respective work duties. Participants initially assisted with simple work tasks, but over time, they were able to expand their range of duties to include more complex activities such as customer sales. Participants achieved their nominated good outcomes of improved well-being, engaging in worthwhile activities, contributing to society and socialisation. The evaluation has shown that this workplace programme is a viable model of engagement for younger people with dementia. This evaluation offers a practical demonstration that it is feasible and safe to provide opportunities for younger people with dementia to engage in meaningful activities in the community if appropriate support is provided. © 2015 John Wiley & Sons Ltd.

The visual discrimination of negative facial expressions by younger and older adults.

PubMed

Mienaltowski, Andrew; Johnson, Ellen R; Wittman, Rebecca; Wilson, Anne-Taylor; Sturycz, Cassandra; Norman, J Farley

2013-04-05

Previous research has demonstrated that older adults are not as accurate as younger adults at perceiving negative emotions in facial expressions. These studies rely on emotion recognition tasks that involve choosing between many alternatives, creating the possibility that age differences emerge for cognitive rather than perceptual reasons. In the present study, an emotion discrimination task was used to investigate younger and older adults' ability to visually discriminate between negative emotional facial expressions (anger, sadness, fear, and disgust) at low (40%) and high (80%) expressive intensity. Participants completed trials blocked by pairs of emotions. Discrimination ability was quantified from the participants' responses using signal detection measures. In general, the results indicated that older adults had more difficulty discriminating between low intensity expressions of negative emotions than did younger adults. However, younger and older adults did not differ when discriminating between anger and sadness. These findings demonstrate that age differences in visual emotion discrimination emerge when signal detection measures are used but that these differences are not uniform and occur only in specific contexts.

Memory-guided force control in healthy younger and older adults.

PubMed

Neely, Kristina A; Samimy, Shaadee; Blouch, Samantha L; Wang, Peiyuan; Chennavasin, Amanda; Diaz, Michele T; Dennis, Nancy A

2017-08-01

Successful performance of a memory-guided motor task requires participants to store and then recall an accurate representation of the motor goal. Further, participants must monitor motor output to make adjustments in the absence of visual feedback. The goal of this study was to examine memory-guided grip force in healthy younger and older adults and compare it to performance on behavioral tasks of working memory. Previous work demonstrates that healthy adults decrease force output as a function of time when visual feedback is not available. We hypothesized that older adults would decrease force output at a faster rate than younger adults, due to age-related deficits in working memory. Two groups of participants, younger adults (YA: N = 32, mean age 21.5 years) and older adults (OA: N = 33, mean age 69.3 years), completed four 20-s trials of isometric force with their index finger and thumb, equal to 25% of their maximum voluntary contraction. In the full-vision condition, visual feedback was available for the duration of the trial. In the no vision condition, visual feedback was removed for the last 12 s of each trial. Participants were asked to maintain constant force output in the absence of visual feedback. Participants also completed tasks of word recall and recognition and visuospatial working memory. Counter to our predictions, when visual feedback was removed, younger adults decreased force at a faster rate compared to older adults and the rate of decay was not associated with behavioral performance on tests of working memory.

Marine Early Bajocian Deposits of the Lower Volga Region (Volgograd Region) and Their Belemnite-Based Stratigraphy

NASA Astrophysics Data System (ADS)

Ippolitov, A. P.

2018-05-01

A representative early Bajocian belemnite assemblage containing four genera and 11 species (two identified in open nomenclature and five new: Eocylindroteuthis weisi sp. nov., E. mariottii sp. nov., E. yarkovi sp. nov., Homaloteuthis volgogradensis sp. nov., and Hastites orphana sp. nov.) is described from a section near the Dubovoi hamlet in the Greater Don Bend area (southern termination of the Don-Medveditsa dislocations). Some members of this assemblage were previously known from the Caucasus; however, it is possible to state the discovery of a Euroboreal belemnite fauna completely new for Russia, previously described only from Central Europe and almost unknown for Eastern Europe. The age of the studied assemblage collected from the lower part of the section, traditionally considered to be Upper Bajocian, corresponds to the Laeviuscula ammonite Chronozone and is the first reliable evidence of marine settings in the Volga Region for the early Bajocian. Two new biostratigraphic units, Beds with Eocylindroteuthis weisi and Beds with H. orphana, are introduced. The former, judging from the occurrences of its characteristic species in Western Europe, has a broad correlative potential. On the basis of datings obtained, the scheme of the formational subdivision of the Middle Jurassic of the Volga Region near Volgograd is revised, and the formerly abandoned Bakhtemir Formation is reinstated as a valid unit. Its total range is reestablished as corresponding to the upper part of the Discites (?)/Laeviuscula Chronozone (lower Bajocian)-Garantiana Chronozone (upper Bajocian).

Older Adults Make Less Advantageous Decisions than Younger Adults: Cognitive and Psychological Correlates

PubMed Central

Fein, George; McGillivray, Shannon; Finn, Peter

2007-01-01

This study tested the hypotheses that older adults make less advantageous decisions than younger adults on the Iowa gambling task (IGT). Less advantageous decisions, as measured by the IGT, are characterized by choices that favor larger versus smaller immediate rewards, even though such choices may result in long-term negative consequences. The IGT, and measures of neuropsychological function, personality, and psychopathology were administered to 164 healthy adults 18–85 years of age. Older adults performed less advantageously on the IGT compared with younger adults. Additionally, a greater number of older adult’s IGT performances were classified as ‘impaired’ when compared to younger adults. Less advantageous decisions were associated with obsessive symptoms in older adults and with antisocial symptoms in younger adults. Performance on the IGT was positively associated with auditory working memory and psychomotor function in young adults, and in immediate memory in older adults. PMID:17445297

Understanding the Effect of Workload on Automation Use for Younger and Older Adults

PubMed Central

McBride, Sara E.; Rogers, Wendy A.; Fisk, Arthur D.

2018-01-01

Objective This study examined how individuals, younger and older, interacted with an imperfect automated system. The impact of workload on performance and automation use was also investigated. Background Automation is used in situations characterized by varying levels of workload. As automated systems spread to domains such as transportation and the home, a diverse population of users will interact with automation. Research is needed to understand how different segments of the population use automation. Method Workload was systematically manipulated to create three levels (low, moderate, high) in a dual-task scenario in which participants interacted with a 70% reliable automated aid. Two experiments were conducted to assess automation use for younger and older adults. Results Both younger and older adults relied on the automation more than they complied with it. Among younger adults, high workload led to poorer performance and higher compliance, even when that compliance was detrimental. Older adults’ performance was negatively affected by workload, but their compliance and reliance were unaffected. Conclusion Younger and older adults were both able to use and double-check an imperfect automated system. Workload affected how younger adults complied with automation, particularly with regard to detecting automation false alarms. Older adults tended to comply and rely at fairly high rates overall, and this did not change with increased workload. Application Training programs for imperfect automated systems should vary workload and provide feedback about error types, and strategies for identifying errors. The ability to identify automation errors varies across individuals, thereby necessitating training. PMID:22235529

Smartphone Text Input Method Performance, Usability, and Preference With Younger and Older Adults.

PubMed

Smith, Amanda L; Chaparro, Barbara S

2015-09-01

User performance, perceived usability, and preference for five smartphone text input methods were compared with younger and older novice adults. Smartphones are used for a variety of functions other than phone calls, including text messaging, e-mail, and web browsing. Research comparing performance with methods of text input on smartphones reveals a high degree of variability in reported measures, procedures, and results. This study reports on a direct comparison of five of the most common input methods among a population of younger and older adults, who had no experience with any of the methods. Fifty adults (25 younger, 18-35 years; 25 older, 60-84 years) completed a text entry task using five text input methods (physical Qwerty, onscreen Qwerty, tracing, handwriting, and voice). Entry and error rates, perceived usability, and preference were recorded. Both age groups input text equally fast using voice input, but older adults were slower than younger adults using all other methods. Both age groups had low error rates when using physical Qwerty and voice, but older adults committed more errors with the other three methods. Both younger and older adults preferred voice and physical Qwerty input to the remaining methods. Handwriting consistently performed the worst and was rated lowest by both groups. Voice and physical Qwerty input methods proved to be the most effective for both younger and older adults, and handwriting input was the least effective overall. These findings have implications to the design of future smartphone text input methods and devices, particularly for older adults. © 2015, Human Factors and Ergonomics Society.

Self-management of health-behaviors among older and younger workers with chronic illness.

PubMed

Munir, Fehmidah; Khan, Hafiz T A; Yarker, Joanna; Haslam, Cheryl; Long, Helen; Bains, Manpreet; Kalawsky, Katryna

2009-10-01

To examine the self-management of health behaviors carried out by older (aged 50-69 years) and younger workers (aged 20-49 years) with a chronic illness. Questionnaire data was collected from 759 employees with a diagnosed chronic illness. Four categories of self-managing health behaviors were examined: using prescribed medication, monitoring and responding to symptoms, managing an appropriate diet and exercising. The majority of participants (56-97%) reported being advised to carry out health behaviors at home and at work. Controlling for confounding factors, medication use was associated with younger and older workers. Managing an appropriate diet was associated with younger workers with asthma, musculoskeletal pain or diabetes. Exercising was associated with younger workers with asthma and with older workers with heart disease, arthritis and rheumatism or diabetes. The findings indicate that there are differences in diet and exercise activities among younger and older workers. To increase self-management in health behaviors at work, improved communication and understanding between the different health professions and the patient/employee is required so that different tailored approaches can be effectively targeted both by age and within the context of the working environment, to those managing asthma, heart disease, diabetes and arthritis and rheumatism. 2009 Elsevier Ireland Ltd.

Teen responses when a younger school-age sibling has been bullied

PubMed Central

Honig, Alice Sterling; Zdunowski-Sjoblom, Nicole

2015-01-01

The prevalence of bullying among children, and the sometimes tragic consequences as a result, has become a major concern in schools. The larger research for this study reported on in-depth interviews with 28 elementary and middle school-age boys and girls (7–12 years) who had experienced various forms of bullying and relational aggression by their peers, mostly on school grounds, and the responses of their parents and teachers. Responses of the children's teen siblings to the younger child's revelations of being bullied are the focus of this report. In-depth interviews with each teen sibling (n = 28) and with each bullied child revealed how the children viewed the teen siblings' supportive strategies. Almost all the children (89%) reported that their older siblings talked with them and offered advice. The teen siblings shared with the younger ones that they too (71%) had been bullied, or they knew someone who had been bullied (18%). Teens gave the advice to ‘bully back’ to 11% and advice to ‘tell someone’ to 32% of the younger children. The children felt quite positive about their older siblings' advice (89%), which did differ depending on the bullied child's gender. Teen siblings gave advice to ‘avoid bullies’ to 77% of female and to 27% of male younger children. PMID:25931644

Walking through doorways causes forgetting: Younger and older adults.

PubMed

Radvansky, Gabriel A; Pettijohn, Kyle A; Kim, Joonsung

2015-06-01

Previous research on event cognition has found that walking through doorways can cause forgetting. The explanation for this finding is that there is a competition between event models, producing interference, and depressing performance. The current study explored the degree to which this might be affected by the natural aging process. This is of interest because there is some evidence that older adults have trouble coordinating sources of interference, which is what is thought to underlie this effect. This would suggest that older adults should do worse on this task. Alternatively, there is also evidence that older adults are typically not disrupted at the event level of processing per se. This would suggest that older adults should perform similarly to younger adults on this task. In the study reported here, younger and older participants navigated through a virtual environment, and memory was tested with probes either before or after a shift and for objects that were associated with the participant (i.e., just picked up). In general, both younger and older adults had memory disrupted after walking through a doorway. Importantly, the magnitude of this disruption was similar in the 2 age groups. This is consistent with the idea that processing at the event level is relatively unaffected by the natural aging process. (PsycINFO Database Record (c) 2015 APA, all rights reserved).

Paleohydrology of China Lake basin and the context of early human occupation in the northwestern Mojave Desert, USA

NASA Astrophysics Data System (ADS)

Rosenthal, Jeffrey S.; Meyer, Jack; Palacios-Fest, Manuel R.; Young, D. Craig; Ugan, Andrew; Byrd, Brian F.; Gobalet, Ken; Giacomo, Jason

2017-07-01

Considerable prior research has focused on the interconnected pluvial basins of Owens Lake and Searles Lake, resulting in a long record of paleohydrological change in the lower Owens River system. However, the published record is poorly resolved or contradictory for the period encompassing the terminal Pleistocene (22,000 to 11,600 cal BP) and early Holocene (11,600-8200 cal BP). This has resulted in conflicting interpretations about the timing of lacustrine high stands within the intermediate basin of China Lake, which harbors one of the most extensive records of early human occupation in the western Great Basin and California. Here, we report a broad range of radiocarbon-dated paleoenvironmental evidence, including lacustrine deposits and shoreline features, tufa outcrops, and mollusk, ostracode, and fish bone assemblages, as well as spring and other groundwater-related deposits (a.k.a. "black mats") from throughout China Lake basin, its outlet, and inflow drainages. Based on 98 radiocarbon dates, we develop independent evidence for five significant lake-level oscillations between 18,000 and 13,000 cal BP, and document the persistence of groundwater-fed wetlands from the beginning of the Younger Dryas through the early Holocene (12,900-8200 cal BP); including the transition from ground-water fed lake to freshwater marsh between about 13,000 and 12,600 cal BP. Results of this study support and refine existing evidence that shows rapid, high-amplitude oscillations in the water balance of the Owens River system during the terminal Pleistocene, and suggest widespread human use of China Lake basin began during the Younger Dryas.

On the paleoenvironmental potential of 253 newly discovered pine stumps from Zurich, Switzerland

NASA Astrophysics Data System (ADS)

Reinig, Frederick; Nievergelt, Daniel; Esper, Jan; Friedrich, Michael; Helle, Gerhard; Hellmann, Lena; Kromer, Bernd; Morganti, Sandro; Pauly, Maren; Sookdeo, Adam; Tegel, Willy; Treydte, Kerstin; Wacker, Lukas; Büntgen, Ulf

2017-04-01

The transition from the last Ice Age to the early Holocene 15'000-10'000 BP represents a close natural analog to the ongoing and predicted rates of anthropogenic climate change. A reduced quality and quantity of high-resolution proxy archives during this period, however, limits our understanding of the magnitude and pace of Late Glacial (LG) environmental variability. Here, we present the world's best preserved, most replicated and oldest forest remains: A total of 253 subfossil pine stumps were recently discovered in Zurich. The combined approach of tree-ring and radiocarbon (14C) measurements results in an absolutely dated Preboreal Swiss tree-ring width chronology and eight floating chronologies. With tree ages ranging between 41 and 506 years, often including pith and bark, and a mean segment length of 163 years, this exceptional find is distributed over nearly 2'000 years between the Allerød and the Preboreal. Together with 200 previously collected LG pines from the greater Zurich region, this study sets a benchmark in terms of sample replication and dating precision for stable more dynamic climatic periods such as the Laacher See eruption, the Older and Younger Dryas. The paleoenvironmental significance would even increase when annually resolved 14C-measurements help fixing a major, Northern Hemispheric gap in the absolutely dated dendro time series during the Younger Dryas. While overcoming this interlude, our results further emphasize the importance of interdisciplinary research on these striking LG climatic shifts to better understand and assess their ecological and environmental impact.

Category learning strategies in younger and older adults: Rule abstraction and memorization.

PubMed

Wahlheim, Christopher N; McDaniel, Mark A; Little, Jeri L

2016-06-01

Despite the fundamental role of category learning in cognition, few studies have examined how this ability differs between younger and older adults. The present experiment examined possible age differences in category learning strategies and their effects on learning. Participants were trained on a category determined by a disjunctive rule applied to relational features. The utilization of rule- and exemplar-based strategies was indexed by self-reports and transfer performance. Based on self-reported strategies, the frequencies of rule- and exemplar-based learners were not significantly different between age groups, but there was a significantly higher frequency of intermediate learners (i.e., learners not identifying with a reliance on either rule- or exemplar-based strategies) in the older than younger adult group. Training performance was higher for younger than older adults regardless of the strategy utilized, showing that older adults were impaired in their ability to learn the correct rule or to remember exemplar-label associations. Transfer performance converged with strategy reports in showing higher fidelity category representations for younger adults. Younger adults with high working memory capacity were more likely to use an exemplar-based strategy, and older adults with high working memory capacity showed better training performance. Age groups did not differ in their self-reported memory beliefs, and these beliefs did not predict training strategies or performance. Overall, the present results contradict earlier findings that older adults prefer rule- to exemplar-based learning strategies, presumably to compensate for memory deficits. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Unpleasant Situations Elicit Different Emotional Responses in Younger and Older Adults

PubMed Central

Charles, Susan Turk; Carstensen, Laura L.

2008-01-01

Older adults report less distress in response to interpersonal conflicts than do younger adults, yet few researchers have examined factors that may contribute to these age differences. Emotion regulation is partially determined by the initial cognitive and emotional reactions that events elicit. We examined reported thoughts and emotions of younger and older adults (N = 195) while they listened to three different audio-taped conversations in which people were ostensibly making disparaging remarks about them. At four points during each scenario, the tape paused and participants engaged in a talk-aloud procedure and rated their level of anger and sadness. Findings revealed that older adults reported less anger but equal levels of sadness compared to younger adults, and their comments were judged by coders as less negative. Older adults made fewer appraisals about the people speaking on the tape and expressed less interest in learning more about their motives. Together, findings are consistent with age-related increases in processes that promote disengagement from offending situations. PMID:18808240

Sleep Environment Risks for Younger and Older Infants

PubMed Central

Collie-Akers, Vicki; Schunn, Christy; Moon, Rachel Y.

2014-01-01

OBJECTIVE: Sudden infant death syndrome and other sleep-related causes of infant mortality have several known risk factors. Less is known about the association of those risk factors at different times during infancy. Our objective was to determine any associations between risk factors for sleep-related deaths at different ages. METHODS: A cross-sectional study of sleep-related infant deaths from 24 states during 2004–2012 contained in the National Center for the Review and Prevention of Child Deaths Case Reporting System, a database of death reports from state child death review teams. The main exposure was age, divided into younger (0–3 months) and older (4 months to 364 days) infants. The primary outcomes were bed-sharing, objects in the sleep environment, location (eg, adult bed), and position (eg, prone). RESULTS: A total of 8207 deaths were analyzed. Younger victims were more likely bed-sharing (73.8% vs 58.9%, P < .001) and sleeping in an adult bed/on a person (51.6% vs 43.8%, P < .001). A higher percentage of older victims had an object in the sleep environment (39.4% vs 33.5%, P < .001) and changed position from side/back to prone (18.4% vs 13.8%, P < .001). Multivariable regression confirmed these associations. CONCLUSIONS: Risk factors for sleep-related infant deaths may be different for different age groups. The predominant risk factor for younger infants is bed-sharing, whereas rolling into objects in the sleep area is the predominant risk factor for older infants. Parents should be warned about the dangers of these specific risk factors appropriate to their infant’s age. PMID:25022735

The HVTN503/Phambili HIV vaccine trial: a comparison of younger and older participants

PubMed Central

Volk, Jonathan E.; Hessol, Nancy A.; Gray, Glenda E.; Kublin, James G.; Churchyard, Gavin J.; Mlisana, Koleka; Nchabeleng, Maphoshane; Buchbinder, Susan P.; Bekker, Linda-Gail

2014-01-01

By comparing younger to older participants enrolled in a HIV vaccine efficacy trial, we aimed to gain insights into the inclusion of adolescents in future trials. This was a sub-analysis of a multisite HIV vaccine randomized clinical trial in South Africa, conducted January-September, 2007. Motivations for trial enrollment, social harms, adverse events, and loss to follow-up were compared between younger (18-20 years old) and older participants (21-35 years old). Both younger (n=238) and older participants (n=563) were equally likely to report enrolling for altruistic reasons. Younger females were less likely than older participants to join for trial reimbursement (p=0.005), while younger males were more likely to enroll because the vaccine may provide protection from HIV-acquisition (p<0.001). There were no significant differences in the number of social harms reported. Compared to males over 20 years-old, 18-20-year-old females were less likely to experience adverse events (OR=0.1, CI 0.01-0.80) and no more likely to be lost to follow up (OR=0.7, CI 0.39-1.25), while 18-20-year-old males were no more likely to experience adverse events (OR=1.3, CI 0.58-2.83) or loss to follow-up (OR=0.8, CI 0.51-1.41). Our data support the inclusion of younger participants who are at risk for HIV in future HIV vaccine efficacy trials. PMID:24104693

A Group-Based Program of Emotional Recovery for Younger Women Following Myocardial Infarction

ERIC Educational Resources Information Center

Bowers, Michele J.; Buchanan, Marla J.

2007-01-01

Heart disease is the leading cause of illness, disability, and death among women in Canada. Myocardial infarction (MI) accounts for almost half of these deaths yearly. The purpose of this study was to understand younger women's experience of recovery from MI. A purposive sample consisting of six younger women diagnosed with MI participated in …

Profiles in driver distraction : effects of cell phone conversations on younger and older drivers

DOT National Transportation Integrated Search

2004-01-01

Synopsis Younger and older drivers conversing on a hands-free cell phone were found to have slower responses to random braking by the vehicle ahead. Cell phone use slowed the younger drivers responses to an extent that they were equivalent t...

Testing the Limits of Optimizing Dual-Task Performance in Younger and Older Adults

PubMed Central

Strobach, Tilo; Frensch, Peter; Müller, Herrmann Josef; Schubert, Torsten

2012-01-01

Impaired dual-task performance in younger and older adults can be improved with practice. Optimal conditions even allow for a (near) elimination of this impairment in younger adults. However, it is unknown whether such (near) elimination is the limit of performance improvements in older adults. The present study tests this limit in older adults under conditions of (a) a high amount of dual-task training and (b) training with simplified component tasks in dual-task situations. The data showed that a high amount of dual-task training in older adults provided no evidence for an improvement of dual-task performance to the optimal dual-task performance level achieved by younger adults. However, training with simplified component tasks in dual-task situations exclusively in older adults provided a similar level of optimal dual-task performance in both age groups. Therefore through applying a testing the limits approach, we demonstrated that older adults improved dual-task performance to the same level as younger adults at the end of training under very specific conditions. PMID:22408613

Quality of Life in the Nursing Home: Perspectives of Younger and Older Residents

ERIC Educational Resources Information Center

Watt, Ashli; Konnert, Candace

2007-01-01

Adults aged 65 and younger make up a significant proportion of nursing-home residents. To date, however, there is no research examining their quality of life (QOL), including how their perceptions of QOL compare to those of older nursing-home residents. This study used a multidimensional approach to (a) assess the QOL of younger nursing-home…

The -Younger-Minority Boy" as a Clue to the Source of Achievement Orientation.

ERIC Educational Resources Information Center

Kammeyer, Kenneth C. W.

This study is a follow-up of the work by Morris Rosenberg who found that younger-minority boys tend to have high self-esteem, but a relatively low achievement orientation and low grades in school. Sampling a total 898 high school senior boys, this study found that younger minority boys do have lower grades and lower occupational and educational…

Expanded record of Quaternary oceanographic change: Amerasian Arctic Ocean

USGS Publications Warehouse

Ishman, S.E.; Polyak, L.V.; Poore, R.Z.

1996-01-01

Four sediment cores collected from the Northwind and Mendeleyev ridges, Arctic Ocean, from 1089 m to 1909 m water depth, provide an oceanographic record extending back into the Matuyama reversed polarity chron. Benthic foraminiferal analyses show four prominent assemblage zones: Bolivina arctica, Cassidulina teretis, Bulimina aculeata, and Oridorsalis tener from the upper Matuyama reversed polarity chronozone through the Brunhes normal polarity chronozone. These assemblage zones represent depth-dependent benthic foraminiferal biofacies changes associated with oceanographic events that occurred in the Amerasian basin at ??? 780 and 300 ka, and indicate oceanographic influence from the North Atlantic. Recognition of these benthic assemblage zones in Arctic cores from the Alpha Ridge indicates that the benthic foraminiferal zonations in intermediate to deep water (>1000 m) Arctic cores may be more useful than preexisting lithostratigraphic zonations and should provide important information pertaining to the Quaternary paleoceanographic evolution of the Arctic Ocean.

Icon arrays help younger children's proportional reasoning.

PubMed

Ruggeri, Azzurra; Vagharchakian, Laurianne; Xu, Fei

2018-06-01

We investigated the effects of two context variables, presentation format (icon arrays or numerical frequencies) and time limitation (limited or unlimited time), on the proportional reasoning abilities of children aged 7 and 10 years, as well as adults. Participants had to select, between two sets of tokens, the one that offered the highest likelihood of drawing a gold token, that is, the set of elements with the greater proportion of gold tokens. Results show that participants performed better in the unlimited time condition. Moreover, besides a general developmental improvement in accuracy, our results show that younger children performed better when proportions were presented as icon arrays, whereas older children and adults were similarly accurate in the two presentation format conditions. Statement of contribution What is already known on this subject? There is a developmental improvement in proportional reasoning accuracy. Icon arrays facilitate reasoning in adults with low numeracy. What does this study add? Participants were more accurate when they were given more time to make the proportional judgement. Younger children's proportional reasoning was more accurate when they were presented with icon arrays. Proportional reasoning abilities correlate with working memory, approximate number system, and subitizing skills. © 2018 The British Psychological Society.

A qualitative study of younger men's experience of heart attack (myocardial infarction).

PubMed

Merritt, Christopher J; de Zoysa, Nicole; Hutton, Jane M

2017-09-01

The effects of heart attack, or myocardial infarction (MI), across psychosocial domains may be particularly acute in younger adults, for whom serious health events are non-normative. MI morbidity is declining in Western countries, but in England MI numbers have plateaued for the under-45 cohort, where approximately 90% of patients are male. Qualitative research on younger adults' experience of MI is limited, and no study has sampled exclusively under-45s. This study aimed to understand how a sample of men under 45 adjusted to and made sense of MI. Qualitative research design based on semi-structured in-depth interviews. Ten men aged under 45 who had experienced MI in the past 3-6 months were purposively recruited and interviewed. Interviews were transcribed verbatim and analysed using interpretative phenomenological analysis. Seven superordinate themes were identified. This article focuses in depth on the three most original themes: (1) 'I'm less of a man', which described experiences of losing 'maleness' (strength, independence, ability to provide) post-MI; (2) 'Shortened horizons', which covered participants' sense of foreshortened future and consequent reprioritization; and (3) 'Life loses its colour', describing the loss of pleasure from lifestyle-related changes. Themes broadly overlapped with the qualitative literature on younger adult MI. However, some themes (e.g., loss of 'maleness' post-MI, and ambivalence towards MI risk factors) appeared unique to this study. Themes were also discussed in relation to risk factors for anxiety and depression and how this might inform clinical care for a younger, male population. Statement of contribution What is already known on this subject? Myocardial infarction (MI) morbidity is not declining in England for under-45s. Adjustment to MI is particularly challenging for younger adults, perhaps because it is non-normative. However, little is known about the experience of MI in younger adults. What does this study add? This

The hypercorrection effect in younger and older adults.

PubMed

Eich, Teal S; Stern, Yaakov; Metcalfe, Janet

2013-01-01

ABSTRACT The hypercorrection effect, which refers to the finding that errors committed with high confidence are more likely to be corrected than are low confidence errors, has been replicated many times, and with both young adults and children. In the present study, we contrasted older with younger adults. Participants answered general-information questions, made confidence ratings about their answers, were given corrective feedback, and then were retested on questions that they had gotten wrong. While younger adults showed the hypercorrection effect, older adults, despite higher overall accuracy on the general-information questions and excellent basic metacognitive ability, showed a diminished hypercorrection effect. Indeed, the correspondence between their confidence in their errors and the probability of correction was not significantly greater than zero, showing, for the first time, that a particular participant population is selectively impaired on this error correction task. These results potentially offer leverage both on the mechanisms underlying the hypercorrection effect and on reasons for older adults' memory impairments, as well as on memory functions that are spared.

The Effect of Stimulus Valence on Lexical Retrieval in Younger and Older Adults.

PubMed

Blackett, Deena Schwen; Harnish, Stacy M; Lundine, Jennifer P; Zezinka, Alexandra; Healy, Eric W

2017-07-12

Although there is evidence that emotional valence of stimuli impacts lexical processes, there is limited work investigating its specific impact on lexical retrieval. The current study aimed to determine the degree to which emotional valence of pictured stimuli impacts naming latencies in healthy younger and older adults. Eighteen healthy younger adults and 18 healthy older adults named positive, negative, and neutral images, and reaction time was measured. Reaction times for positive and negative images were significantly longer than reaction times for neutral images. Reaction times for positive and negative images were not significantly different. Whereas older adults demonstrated significantly longer naming latencies overall than younger adults, the discrepancy in latency with age was far greater when naming emotional pictures. Emotional arousal of pictures appears to impact naming latency in younger and older adults. We hypothesize that the increase in naming latency for emotional stimuli is the result of a necessary disengagement of attentional resources from the emotional images prior to completion of the naming task. We propose that this process may affect older adults disproportionately due to a decline in attentional resources as part of normal aging, combined with a greater attentional preference for emotional stimuli.

Pioglitazone is equally effective for diabetes prevention in older versus younger adults with impaired glucose tolerance.

PubMed

Espinoza, Sara E; Wang, Chen-Pin; Tripathy, Devjit; Clement, Stephen C; Schwenke, Dawn C; Banerji, Mary Ann; Bray, George A; Buchanan, Thomas A; Henry, Robert R; Kitabchi, Abbas E; Mudaliar, Sunder; Stentz, Frankie B; Reaven, Peter D; DeFronzo, Ralph A; Musi, Nicolas

2016-12-01

To determine the efficacy of pioglitazone to prevent type 2 diabetes in older compared to younger adults with pre-diabetes. Six hundred two participants with impaired glucose tolerance (IGT) were randomized in double blind fashion to placebo or pioglitazone for diabetes prevention in the ACT NOW study (NEJM 364:1104-1115, 2011). Cox proportional hazard regression was used to compare time to development of diabetes over a mean of 2 years between older (≥61 years) and younger participants. We compared effects of pioglitazone versus placebo on metabolic profiles, inflammatory markers, adipokines, β cell function (disposition index), insulin sensitivity (Matsuda index), and body composition by ANOVA. Diabetes incidence was reduced by 85 % in older and 69 % in younger subjects (p = 0.41). β cell function (disposition index) increased by 35.0 % in the older and 26.7 % in younger subjects (p = 0.83). Insulin sensitivity (Matsuda index) increased by 3.07 (5.2-fold) in older and by 2.54 (3.8-fold) in younger participants (p = 0.58). Pioglitazone more effectively increased adiponectin in older versus younger subjects (22.9 ± 3.2 μg/mL [2.7-fold] vs. 12.7 ± 1.4 μg/mL [2.2-fold], respectively; p = 0.04). Younger subjects tended to have a greater increase in whole body fat mass compared to older subjects (3.6 vs. 3.1 kg; p = 0.061). Younger and older subjects had similar decreases in bone mineral density (0.018 ± 0.0071 vs. 0.0138 ± 0.021 g/cm 2 ). Younger and older pre-diabetic adults taking pioglitazone had similar reductions in conversion to diabetes and older adults had similar or greater improvements in metabolic risk factors, demonstrating that pioglitazone is useful in preventing diabetes in older adults.

Biogenic silica from the BDP93 drill site and adjacent areas of the Selenga Delta, Lake Baikal, Siberia

USGS Publications Warehouse

Colman, Steven M.; Peck, John A.; Hatton, Josephine; Karabanov, Eugene B.; King, John W.

1999-01-01

Biogenic silica contents of sediments on the lower Selenga Delta and Buguldeika saddle in Lake Baikal show distinct fluctuations that reflect changes in diatom productivity, and ultimately, climate. The pattern of the upper 50 m of the section, dating from about 334 ka, is similar to that of the marine oxygen-isotope record, increasingly so as the younger sediments become progressively finer grained and less locally derived with time. The last two interglaciations are marked by biogenic silica abundances similar to those of the Holocene. The equivalent of marine oxygen-isotope stage 3 is distinctly intermediate in character between full glacial and full interglacial biogenic silica values. Following near-zero values during the last glacial maximum, biogenic silica began to increase at about 13 ka. The rise in biogenic silica to Holocene values was interrupted by an abrupt decrease during Younger Dryas time, about 11 to 10 14C ka.

Exploring Interhemispheric Collaboration in Older Compared to Younger Adults

ERIC Educational Resources Information Center

Cherry, Barbara J.; Yamashiro, Mariana; Anderson, Erin; Barrett, Christopher; Adamson, Maheen M.; Hellige, Joseph B.

2010-01-01

Physical and Name Identity letter-matching tasks were used to explore differences in interhemispheric collaboration in younger and older adults. To determine whether other factors might also be related to across/within-hemisphere processing or visual field asymmetries, neuropsychological tests measuring frontal/executive functioning were…

Situation Selection and Modification for Emotion Regulation in Younger and Older Adults.

PubMed

Livingstone, Kimberly M; Isaacowitz, Derek M

2015-11-01

This research investigated age differences in use and effectiveness of situation selection and situation modification for emotion regulation. Socioemotional selectivity theory suggests stronger emotional well-being goals in older age; emotion regulation may support this goal. Younger and older adults assigned to an emotion regulation or "just view" condition first freely chose to engage with negative, neutral, or positive material (situation selection), then chose to view or skip negative and positive material (situation modification), rating affect after each experience. In both tasks, older adults in both goal conditions demonstrated pro-hedonic emotion regulation, spending less time with negative material compared to younger adults. Younger adults in the regulate condition also engaged in pro-hedonic situation selection, but not modification. Whereas situation selection was related to affect, modification of negative material was not. This research supports more frequent pro-hedonic motivation in older age, as well as age differences in use of early-stage emotion regulation.

The effects of sleep on episodic memory in older and younger adults.

PubMed

Aly, Mariam; Moscovitch, Morris

2010-04-01

Evidence on sleep-dependent benefits for episodic memory remains elusive. Furthermore we know little about age-related changes on the effects of sleep on episodic memory. The study we report is the first to compare the effects of sleep on episodic memories in younger and older adults. Memories of stories and personal events were assessed following a retention interval that included sleep and following an equal duration of wakefulness. Both older and younger adults have superior memory following sleep compared to following wakefulness for both types of material. Amount of forgetting of personal events was less during wakefulness in older adults than in younger adults, possibly due to spontaneous rehearsal. Amount of time spent sleeping correlated highly with sleep benefit in older adults, suggesting that quantity of total sleep, and/or time spent in some stages of sleep, are important contributors to age-related differences in memory consolidation or protection from interference during sleep.

Situation Selection and Modification for Emotion Regulation in Younger and Older Adults

PubMed Central

Livingstone, Kimberly M.; Isaacowitz, Derek M.

2016-01-01

This research investigated age differences in use and effectiveness of situation selection and situation modification for emotion regulation. Socioemotional selectivity theory suggests stronger emotional well-being goals in older age; emotion regulation may support this goal. Younger and older adults assigned to an emotion regulation or “just view” condition first freely chose to engage with negative, neutral, or positive material (situation selection), then chose to view or skip negative and positive material (situation modification), rating affect after each experience. In both tasks, older adults in both goal conditions demonstrated pro-hedonic emotion regulation, spending less time with negative material compared to younger adults. Younger adults in the regulate condition also engaged in pro-hedonic situation selection, but not modification. Whereas situation selection was related to affect, modification of negative material was not. This research supports more frequent pro-hedonic motivation in older age, as well as age differences in use of early-stage emotion regulation. PMID:26998196

Exploration of older and younger British adults' performance on The Awareness of Social Inference Test (TASIT).

PubMed

Burdon, Paul; Dipper, Lucy; Cocks, Naomi

2016-09-01

Social perception is an important skill. One assessment that is commonly used to assess social perception abilities is The Awareness of Social Inference Test (TASIT). The only normative data available for this test are for Australian younger adults. Despite no normative data being available for British adults, the test is widely used in the UK with older and younger adults. There is a growing body of research that suggests that older adults have difficulty with skills associated with social perception. There is therefore a need to determine whether British adults, and more specifically British older adults, perform similarly to the Australian normative TASIT scores available in the manual. To explore the differences between older and younger British adults' performance on TASIT, and to determine whether younger and older British adults perform similarly to the data from Australian adults in TASIT manual. TASIT was administered to a total of 42 native British English speaking participants. The participants were split into two age groups 18-45 and 60-90 years. Comparisons were made between the two groups and the Australian data in TASIT manual. The younger British and Australian adults obtained similar scores on all parts of TASIT. The older British adults though, obtained significantly lower scores than the Australian younger adults on all parts of TASIT and when education was controlled for they obtained significantly lower scores than the British younger adults. The findings are discussed in the light of previous research that has found that older adults are worse than younger adults at social inferences. The findings of the current study suggest that caution should be used when using TASIT with older British adults to assess social perception abilities. © 2016 Royal College of Speech and Language Therapists.

The younger siblings of teenage mothers: a follow-up of their pregnancy risk.

PubMed

East, P L; Jacobson, L J

2001-03-01

This study followed 243 younger brothers and younger sisters of parenting teens and nonparenting teens across a 1.5-year period. The average age of siblings was 13.6 years at Time 1 and 15 years at Time 2. Relative to other youths, the sisters of parenting teens exhibited a sharp increase in drug and alcohol use and partying behavior across time and had the highest pregnancy rate at Time 2 (15%). The siblings of parenting teens spent 10 hr a week caring for their sisters' children, and, for girls, many hours of child care was associated with negative outcomes including permissive sexual behavior. Findings suggest that the younger sisters of parenting teens are at very high risk of early pregnancy and that this risk becomes increasingly pronounced across time.

The Younger Siblings of Teenage Mothers: A Follow-Up of Their Pregnancy Risk

PubMed Central

East, Patricia L.; Jacobson, Leanne J.

2013-01-01

This study followed 243 younger brothers and younger sisters of parenting teens and nonparenting teens across a 1.5-year period. The average age of siblings was 13.6 years at Time 1 and 15 years at Time 2. Relative to other youths, the sisters of parenting teens exhibited a sharp increase in drug and alcohol use and partying behavior across time and had the highest pregnancy rate at Time 2 (15%). The siblings of parenting teens spent 10 hr a week caring for their sisters’ children, and, for girls, many hours of child care was associated with negative outcomes including permissive sexual behavior. Findings suggest that the younger sisters of parenting teens are at very high risk of early pregnancy and that this risk becomes increasingly pronounced across time. PMID:11269393

Younger Children's (Three to Five Years) Perceptions of Being in a Health-Care Situation

ERIC Educational Resources Information Center

Stålberg, Anna; Sandberg, Anette; Söderbäck, Maja

2016-01-01

Younger children are common users of health-care services. Their perspective on a health-care situation and their ways of communication differ from that of adults. There is a shortness of research of younger children's perceptions of health-care situations. The knowledge that exists indicates the importance of involving the child's perspective to…

The Experiences of the Younger Supervisor: Implications for Organizations

ERIC Educational Resources Information Center

Hanson, Lea

2012-01-01

With four generations in today's workforce, roles are being redefined to include a growing number of younger supervisor/older subordinate relationships, referred to as the intergenerational dyad. What current and limited literature exists about the intergenerational dyad exclusively addresses the issues of generational workplace differences…

Trends in colorectal cancer incidence among younger adults-Disparities by age, sex, race, ethnicity, and subsite.

PubMed

Crosbie, Amanda B; Roche, Lisa M; Johnson, Linda M; Pawlish, Karen S; Paddock, Lisa E; Stroup, Antoinette M

2018-06-22

Millennials (ages 18-35) are now the largest living generation in the US, making it important to understand and characterize the rising trend of colorectal cancer incidence in this population, as well as other younger generations of Americans. Data from the New Jersey State Cancer Registry (n = 181 909) and Surveillance, Epidemiology, and End Results program (n = 448 714) were used to analyze invasive CRC incidence trends from 1979 to 2014. Age, sex, race, ethnicity, subsite, and stage differences between younger adults (20-49) and screening age adults (≥50) in New Jersey (NJ) were examined using chi-square; and, we compared secular trends in NJ to the United States (US). Whites, men, and the youngest adults (ages 20-39) are experiencing greater APCs in rectal cancer incidence. Rates among younger black adults, overall, were consistently higher in both NJ and the US over time. When compared to older adults, younger adults with CRC in NJ were more likely to be: diagnosed at the late stage, diagnosed with rectal cancer, male, non-white, and Hispanic. Invasive CRC incidence trends among younger adults were found to vary by age, sex, race, ethnicity, and subsite. Large, case-level, studies are needed to understand the role of genetics, human papillomavirus (HPV), and cultural and behavioral factors in the rise of CRC among younger adults. Provider and public education about CRC risk factors will also be important for preventing and reversing the increasing CRC trend in younger adults. © 2018 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

Category Learning Strategies in Younger and Older Adults: Rule Abstraction and Memorization

PubMed Central

Wahlheim, Christopher N.; McDaniel, Mark A.; Little, Jeri L.

2016-01-01

Despite the fundamental role of category learning in cognition, few studies have examined how this ability differs between younger and older adults. The present experiment examined possible age differences in category learning strategies and their effects on learning. Participants were trained on a category determined by a disjunctive rule applied to relational features. The utilization of rule- and exemplar-based strategies was indexed by self-reports and transfer performance. Based on self-reported strategies, both age groups had comparable frequencies of rule- and exemplar-based learners, but older adults had a higher frequency of intermediate learners (i.e., learners not identifying with a reliance on either rule- or exemplar-based strategies). Training performance was higher for younger than older adults regardless of the strategy utilized, showing that older adults were impaired in their ability to learn the correct rule or to remember exemplar-label associations. Transfer performance converged with strategy reports in showing higher fidelity category representations for younger adults. Younger adults with high working memory capacity were more likely to use an exemplar-based strategy, and older adults with high working memory capacity showed better training performance. Age groups did not differ in their self-reported memory beliefs, and these beliefs did not predict training strategies or performance. Overall, the present results contradict earlier findings that older adults prefer rule- to exemplar-based learning strategies, presumably to compensate for memory deficits. PMID:26950225

Efficacy and safety of tofacitinib in older and younger patients with rheumatoid arthritis.

PubMed

Curtis, Jeffrey R; Schulze-Koops, Hendrik; Takiya, Liza; Mebus, Charles A; Terry, Ketti K; Biswas, Pinaki; Jones, Thomas V

2017-01-01

Tofacitinib is an oral Janus kinase inhibitor for the treatment of rheumatoid arthritis (RA). We evaluated the efficacy and safety of tofacitinib 5 or 10 mg twice daily (BID), in patients with moderate to severe RA, aged ≥65 and <65 years. Data were pooled from five Phase 3 trials and, separately, from two open-label long-term extension (LTE) studies (data cut-off April, 2012). Patients received tofacitinib, or placebo (Phase 3 only), with/without conventional synthetic DMARDs (mainly methotrexate). Clinical efficacy outcomes from Phase 3 studies were evaluated at Month 3. Safety evaluations using pooled Phase 3 data (Month 12) and pooled LTE data (Month 24) compared exposure-adjusted incidence rates (IRs; with 95% confidence intervals [CIs]), in older versus younger patients. In Phase 3 and LTE studies, 15.3% (475/3111) and 16.1% (661/4102) of patients, respectively, were aged ≥65 years. Consequently, exposure to tofacitinib was lower in older versus younger patients in Phase 3 (259.2 vs. 1554.9 patient years [pt-yrs]) and LTE (962.1 vs. 5071.7 pt-yrs) studies. Probability ratios for ACR responses and HAQ-DI improvement from baseline ≥0.22 (Month 3) favoured tofacitinib and were similar in older and younger patients, with overlapping CIs. IRs for SAEs and discontinuations due to AEs were generally numerically higher in older versus younger patients, irrespective of treatment. Older patients receiving tofacitinib 5 or 10 mg BID had a similar probability of ACR20 or ACR50 response and, due to comorbidities, a numerically higher risk of SAEs and discontinuations due to AEs compared with younger patients.

Training Attentional Control and Working Memory--Is Younger, Better?

ERIC Educational Resources Information Center

Wass, S. V.; Scerif, G.; Johnson, M. H.

2012-01-01

Authors have argued that various forms of interventions may be more effective in younger children. Is cognitive training also more effective, the earlier the training is applied? We review evidence suggesting that functional neural networks, including those subserving attentional control, may be more unspecialised and undifferentiated earlier in…

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago.

PubMed

Bunch, Ted E; Hermes, Robert E; Moore, Andrew M T; Kennett, Douglas J; Weaver, James C; Wittke, James H; DeCarli, Paul S; Bischoff, James L; Hillman, Gordon C; Howard, George A; Kimbel, David R; Kletetschka, Gunther; Lipo, Carl P; Sakai, Sachiko; Revay, Zsolt; West, Allen; Firestone, Richard B; Kennett, James P

2012-07-10

It has been proposed that fragments of an asteroid or comet impacted Earth, deposited silica- and iron-rich microspherules and other proxies across several continents, and triggered the Younger Dryas cooling episode 12,900 years ago. Although many independent groups have confirmed the impact evidence, the hypothesis remains controversial because some groups have failed to do so. We examined sediment sequences from 18 dated Younger Dryas boundary (YDB) sites across three continents (North America, Europe, and Asia), spanning 12,000 km around nearly one-third of the planet. All sites display abundant microspherules in the YDB with none or few above and below. In addition, three sites (Abu Hureyra, Syria; Melrose, Pennsylvania; and Blackville, South Carolina) display vesicular, high-temperature, siliceous scoria-like objects, or SLOs, that match the spherules geochemically. We compared YDB objects with melt products from a known cosmic impact (Meteor Crater, Arizona) and from the 1945 Trinity nuclear airburst in Socorro, New Mexico, and found that all of these high-energy events produced material that is geochemically and morphologically comparable, including: (i) high-temperature, rapidly quenched microspherules and SLOs; (ii) corundum, mullite, and suessite (Fe(3)Si), a rare meteoritic mineral that forms under high temperatures; (iii) melted SiO(2) glass, or lechatelierite, with flow textures (or schlieren) that form at > 2,200 °C; and (iv) particles with features indicative of high-energy interparticle collisions. These results are inconsistent with anthropogenic, volcanic, authigenic, and cosmic materials, yet consistent with cosmic ejecta, supporting the hypothesis of extraterrestrial airbursts/impacts 12,900 years ago. The wide geographic distribution of SLOs is consistent with multiple impactors.

Climate change, adaptive cycles, and the persistence of foraging economies during the late Pleistocene/Holocene transition in the Levant.

PubMed

Rosen, Arlene M; Rivera-Collazo, Isabel

2012-03-06

Climatic forcing during the Younger Dryas (∼12.9-11.5 ky B.P.) event has become the theoretical basis to explain the origins of agricultural lifestyles in the Levant by suggesting a failure of foraging societies to adjust. This explanation however, does not fit the scarcity of data for predomestication cultivation in the Natufian Period. The resilience of Younger Dryas foragers is better illustrated by a concept of adaptive cycles within a theory of adaptive change (resilience theory). Such cycles consist of four phases: release/collapse (Ω); reorganization (α), when the system restructures itself after a catastrophic stimulus through innovation and social memory--a period of greater resilience and less vulnerability; exploitation (r); and conservation (K), representing an increasingly rigid system that loses flexibility to change. The Kebarans and Late Natufians had similar responses to cold and dry conditions vs. Early Natufians and the Pre-Pottery Neolithic A responses to warm and wet climates. Kebarans and Late Natufians (α-phase) shifted to a broader-based diet and increased their mobility. Early Natufian and Pre-Pottery Neolithic A populations (r- and K-phases) had a growing investment in more narrowly focused, high-yield plant resources, but they maintained the broad range of hunted animals because of increased sedentism. These human adaptive cycles interlocked with plant and animal cycles. Forest and grassland vegetation responded to late Pleistocene and early Holocene climatic fluctuations, but prey animal cycles reflected the impact of human hunting pressure. The combination of these three adaptive cycles results in a model of human adaptation, showing potential for great sustainability of Levantine foraging systems even under adverse climatic conditions.

A regional tephrostratigraphic framework for central and southern European climate archives during the Last Glacial to Interglacial transition: comparisons north and south of the Alps

NASA Astrophysics Data System (ADS)

Lane, C. S.; Blockley, S. P. E.; Lotter, A. F.; Finsinger, W.; Filippi, M. L.; Matthews, I. P.

2012-03-01

This paper summarises the results of tephrochronological investigations into a suite of central and southern European records, which include: Rotmeer, southern Germany; Soppensee and Rotsee, central Swiss Plateau; Lago di Lavarone and Lago Piccolo di Avigliana, Italian southern Alpine foreland. These sites provide records of palaeoenvironmental changes for the Last Glacial to Interglacial Transition (LGIT) at the boundary between North Atlantic and Mediterranean climatic influences. Chemical characterisation of glass shards in volcanic ash layers indicates that multiple volcanic sources have contributed to the central European tephra record. Amongst other volcanic markers, the Laacher See Tephra, originating from the Eifel region of Germany c. 12.9 ± 0.1 ka, and the Vedde Ash from Iceland c. 12.1 ± 0.1 ka, are found co-located within the sediments of Rotmeer, Soppensee, Rotsee and Lago Piccolo di Avigliana. These key horizons, which bracket the onset of the Younger Dryas stadial, provide precise calendrically-dated tie points around which a detailed picture of the timing of local and regional environmental transitions can be constructed. Using the co-located tephra layers the re-colonisation of Northern Italian catchment areas by Quercus is shown to occur just prior to the deposition of the Laacher See Tephra layer, whereas to the North of the Alps Quercus and other thermophilous trees do not reappear until several centuries after the deposition of the Vedde Ash. Furthermore, the discovery of the Vedde Ash in Lago Piccolo di Avigliana and Lago di Lavarone is indicative of atmospheric transport of polar air into southern Europe during the Younger Dryas stadial, matching evidence proposed for such transport of polar air during the Last Glacial Maximum (LGM).

Post-glacial flooding of the Bering Land Bridge dated to 11 cal ka BP based on new geophysical and sediment records

NASA Astrophysics Data System (ADS)

Jakobsson, Martin; Pearce, Christof; Cronin, Thomas M.; Backman, Jan; Anderson, Leif G.; Barrientos, Natalia; Björk, Göran; Coxall, Helen; de Boer, Agatha; Mayer, Larry A.; Mörth, Carl-Magnus; Nilsson, Johan; Rattray, Jayne E.; Stranne, Christian; Semiletov, Igor; O'Regan, Matt

2017-08-01

The Bering Strait connects the Arctic and Pacific oceans and separates the North American and Asian landmasses. The presently shallow ( ˜ 53 m) strait was exposed during the sea level lowstand of the last glacial period, which permitted human migration across a land bridge today referred to as the Bering Land Bridge. Proxy studies (stable isotope composition of foraminifera, whale migration into the Arctic Ocean, mollusc and insect fossils and paleobotanical data) have suggested a range of ages for the Bering Strait reopening, mainly falling within the Younger Dryas stadial (12.9-11.7 cal ka BP). Here we provide new information on the deglacial and post-glacial evolution of the Arctic-Pacific connection through the Bering Strait based on analyses of geological and geophysical data from Herald Canyon, located north of the Bering Strait on the Chukchi Sea shelf region in the western Arctic Ocean. Our results suggest an initial opening at about 11 cal ka BP in the earliest Holocene, which is later than in several previous studies. Our key evidence is based on a well-dated core from Herald Canyon, in which a shift from a near-shore environment to a Pacific-influenced open marine setting at around 11 cal ka BP is observed. The shift corresponds to meltwater pulse 1b (MWP1b) and is interpreted to signify relatively rapid breaching of the Bering Strait and the submergence of the large Bering Land Bridge. Although the precise rates of sea level rise cannot be quantified, our new results suggest that the late deglacial sea level rise was rapid and occurred after the end of the Younger Dryas stadial.

Archaeal community changes in Lateglacial lake sediments: Evidence from ancient DNA

NASA Astrophysics Data System (ADS)

Ahmed, Engy; Parducci, Laura; Unneberg, Per; Ågren, Rasmus; Schenk, Frederik; Rattray, Jayne E.; Han, Lu; Muschitiello, Francesco; Pedersen, Mikkel W.; Smittenberg, Rienk H.; Yamoah, Kweku Afrifa; Slotte, Tanja; Wohlfarth, Barbara

2018-02-01

The Lateglacial/early Holocene sediments from the ancient lake at Hässeldala Port, southern Sweden provide an important archive for the environmental and climatic shifts at the end of the last ice age and the transition into the present Interglacial. The existing multi-proxy data set highlights the complex interplay of physical and ecological changes in response to climatic shifts and lake status changes. Yet, it remains unclear how microorganisms, such as Archaea, which do not leave microscopic features in the sedimentary record, were affected by these climatic shifts. Here we present the metagenomic data set of Hässeldala Port with a special focus on the abundance and biodiversity of Archaea. This allows reconstructing for the first time the temporal succession of major Archaea groups between 13.9 and 10.8 ka BP by using ancient environmental DNA metagenomics and fossil archaeal cell membrane lipids. We then evaluate to which extent these findings reflect physical changes of the lake system, due to changes in lake-water summer temperature and seasonal lake-ice cover. We show that variations in archaeal composition and diversity were related to a variety of factors (e.g., changes in lake water temperature, duration of lake ice cover, rapid sediment infilling), which influenced bottom water conditions and the sediment-water interface. Methanogenic Archaea dominated during the Allerød and Younger Dryas pollen zones, when the ancient lake was likely stratified and anoxic for large parts of the year. The increase in archaeal diversity at the Younger Dryas/Holocene transition is explained by sediment infilling and formation of a mire/peatbog.

Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago

USGS Publications Warehouse

Wittke, James H.; Weaver, James C.; Bunch, Ted E.; Kennett, James P.; Kennett, Douglas J.; Moore, Andrew M.T.; Hillman, Gordon C.; Tankersly, Kenneth B.; Goodyear, Albert C.; Moore, Christopher R.; Daniel, I. Randolph; Ray, Jack H.; Lopinot, Neal H.; Ferraro, David; Israde-Alcántara, Isabel; Bischoff, James L.; DeCarli, Paul S.; Hermes, Robert E.; Kloosterman, Johan B.; Revay, Zsolt; Howard, George A.; Kimbel, David R.; Kletetschka, Gunther; Nabelek, Ladislav; Lipo, Carl P.; Sakai, Sachiko; West, Allen; Firestone, Richard B.

2013-01-01

Airbursts/impacts by a fragmented comet or asteroid have been proposed at the Younger Dryas onset (12.80 ± 0.15 ka) based on identification of an assemblage of impact-related proxies, including microspherules, nanodiamonds, and iridium. Distributed across four continents at the Younger Dryas boundary (YDB), spherule peaks have been independently confirmed in eight studies, but unconfirmed in two others, resulting in continued dispute about their occurrence, distribution, and origin. To further address this dispute and better identify YDB spherules, we present results from one of the largest spherule investigations ever undertaken regarding spherule geochemistry, morphologies, origins, and processes of formation. We investigated 18 sites across North America, Europe, and the Middle East, performing nearly 700 analyses on spherules using energy dispersive X-ray spectroscopy for geochemical analyses and scanning electron microscopy for surface microstructural characterization. Twelve locations rank among the world’s premier end-Pleistocene archaeological sites, where the YDB marks a hiatus in human occupation or major changes in site use. Our results are consistent with melting of sediments to temperatures >2,200 °C by the thermal radiation and air shocks produced by passage of an extraterrestrial object through the atmosphere; they are inconsistent with volcanic, cosmic, anthropogenic, lightning, or authigenic sources. We also produced spherules from wood in the laboratory at >1,730 °C, indicating that impact-related incineration of biomass may have contributed to spherule production. At 12.8 ka, an estimated 10 million tonnes of spherules were distributed across ∼50 million square kilometers, similar to well-known impact strewnfields and consistent with a major cosmic impact event.

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago

USGS Publications Warehouse

Bunch, Ted E.; Hermes, Robert E.; Moore, Andrew M.T.; Kennett, Douglas J.; Weaver, James C.; Wittke, James H.; DeCarli, Paul S.; Bischoff, James L.; Hillman, Gordon C.; Howard, George A.; Kimbel, David R.; Kletetschka, Gunther; Lipo, Carl P.; Sakai, Sachiko; Revay, Zsolt; West, Allen; Firestone, Richard B.; Kennett, James P.

2012-01-01

It has been proposed that fragments of an asteroid or comet impacted Earth, deposited silica-and iron-rich microspherules and other proxies across several continents, and triggered the Younger Dryas cooling episode 12,900 years ago. Although many independent groups have confirmed the impact evidence, the hypothesis remains controversial because some groups have failed to do so. We examined sediment sequences from 18 dated Younger Dryas boundary (YDB) sites across three continents (North America, Europe, and Asia), spanning 12,000 km around nearly one-third of the planet. All sites display abundant microspherules in the YDB with none or few above and below. In addition, three sites (Abu Hureyra, Syria; Melrose, Pennsylvania; and Blackville, South Carolina) display vesicular, high-temperature, siliceous scoria-like objects, or SLOs, that match the spherules geochemically. We compared YDB objects with melt products from a known cosmic impact (Meteor Crater, Arizona) and from the 1945 Trinity nuclear airburst in Socorro, New Mexico, and found that all of these high-energy events produced material that is geochemically and morphologically comparable, including: (i) high-temperature, rapidly quenched microspherules and SLOs; (ii) corundum, mullite, and suessite (Fe3,/sup>Si), a rare meteoritic mineral that forms under high temperatures; (iii) melted SiO2 glass, or lechatelierite, with flow textures (or schlieren) that form at > 2,200 °C; and (iv) particles with features indicative of high-energy interparticle collisions. These results are inconsistent with anthropogenic, volcanic, authigenic, and cosmic materials, yet consistent with cosmic ejecta, supporting the hypothesis of extraterrestrial airbursts/impacts 12,900 years ago. The wide geographic distribution of SLOs is consistent with multiple impactors.

Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago

PubMed Central

Wittke, James H.; Weaver, James C.; Bunch, Ted E.; Kennett, James P.; Kennett, Douglas J.; Moore, Andrew M. T.; Hillman, Gordon C.; Tankersley, Kenneth B.; Goodyear, Albert C.; Moore, Christopher R.; Daniel, I. Randolph; Ray, Jack H.; Lopinot, Neal H.; Ferraro, David; Israde-Alcántara, Isabel; Bischoff, James L.; DeCarli, Paul S.; Hermes, Robert E.; Kloosterman, Johan B.; Revay, Zsolt; Howard, George A.; Kimbel, David R.; Kletetschka, Gunther; Nabelek, Ladislav; Lipo, Carl P.; Sakai, Sachiko; West, Allen; Firestone, Richard B.

2013-01-01

Airbursts/impacts by a fragmented comet or asteroid have been proposed at the Younger Dryas onset (12.80 ± 0.15 ka) based on identification of an assemblage of impact-related proxies, including microspherules, nanodiamonds, and iridium. Distributed across four continents at the Younger Dryas boundary (YDB), spherule peaks have been independently confirmed in eight studies, but unconfirmed in two others, resulting in continued dispute about their occurrence, distribution, and origin. To further address this dispute and better identify YDB spherules, we present results from one of the largest spherule investigations ever undertaken regarding spherule geochemistry, morphologies, origins, and processes of formation. We investigated 18 sites across North America, Europe, and the Middle East, performing nearly 700 analyses on spherules using energy dispersive X-ray spectroscopy for geochemical analyses and scanning electron microscopy for surface microstructural characterization. Twelve locations rank among the world’s premier end-Pleistocene archaeological sites, where the YDB marks a hiatus in human occupation or major changes in site use. Our results are consistent with melting of sediments to temperatures >2,200 °C by the thermal radiation and air shocks produced by passage of an extraterrestrial object through the atmosphere; they are inconsistent with volcanic, cosmic, anthropogenic, lightning, or authigenic sources. We also produced spherules from wood in the laboratory at >1,730 °C, indicating that impact-related incineration of biomass may have contributed to spherule production. At 12.8 ka, an estimated 10 million tonnes of spherules were distributed across ∼50 million square kilometers, similar to well-known impact strewnfields and consistent with a major cosmic impact event. PMID:23690611

Reflections of Distraction in Memory: Transfer of Previous Distraction Improves Recall in Younger and Older Adults

PubMed Central

Thomas, Ruthann C.; Hasher, Lynn

2012-01-01

Three studies explored whether younger and older adults’ free recall performance can benefit from prior exposure to distraction that becomes relevant in a memory task. Participants initially read stories that included distracting text. Later, they studied a list of words for free recall, with half of the list consisting of previously distracting words. When the memory task was indirect in its use of distraction (Study 1), only older adults showed transfer, with better recall of previously distracting compared with new words, which increased their recall to match that of younger adults. However, younger adults showed transfer when cued about the relevance of previous distraction both before studying the words (Study 2) and before recalling the words (Study 3) in the memory test. Results suggest that both younger and older adults encode distraction, but younger adults require explicit cueing to use their knowledge of distraction. In contrast, older adults transfer knowledge of distraction in both explicitly cued and indirect memory tasks. Results are discussed in terms of age differences in inhibition and source-constrained retrieval. PMID:21843024

Reflections of distraction in memory: transfer of previous distraction improves recall in younger and older adults.

PubMed

Thomas, Ruthann C; Hasher, Lynn

2012-01-01

Three studies explored whether younger and older adults' free recall performance can benefit from prior exposure to distraction that becomes relevant in a memory task. Participants initially read stories that included distracting text. Later, they studied a list of words for free recall, with half of the list consisting of previously distracting words. When the memory task was indirect in its use of distraction (Study 1), only older adults showed transfer, with better recall of previously distracting compared with new words, which increased their recall to match that of younger adults. However, younger adults showed transfer when cued about the relevance of previous distraction both before studying the words (Study 2) and before recalling the words (Study 3) in the memory test. Results suggest that both younger and older adults encode distraction, but younger adults require explicit cueing to use their knowledge of distraction. In contrast, older adults transfer knowledge of distraction in both explicitly cued and indirect memory tasks. Results are discussed in terms of age differences in inhibition and source-constrained retrieval.

Short-term and long-term collaboration benefits on individual recall in younger and older adults

PubMed Central

Stern, Yaakov

2011-01-01

A recent study of younger adults suggests that, compared to repeated individual recall trials, repeated collaborative recall trials produce better individual recall after a short delay (Blumen & Rajaram, 2008). Our study was designed to determine if such collaboration benefits would remain after a one-week delay, in both younger and older adults. Sixty younger (M age = 24.60) and 60 older (M age = 67.35) adults studied a list of words and then completed either two collaborative recall trials followed by two individual recall trials, or four individual recall trials. A five-min delay was inserted between the first three recall trials. The fourth recall trial was administered 1 week later. Collaborative recall was completed in groups of three individuals working together. Both younger and older adults benefitted from repeated collaborative recall trials to a greater extent than repeated individual recall trials, and such collaboration benefits remained after a one-week delay. This is the first demonstration of collaboration benefits on later individual recall at delays as long as 1 week, in both younger and older adults. Findings are discussed within the context of the negative effects of collaboration associated with group memory (collaborative inhibition) and the positive effects of collaboration associated with later individual memory (collaboration benefits). PMID:21264617

Short-term and long-term collaboration benefits on individual recall in younger and older adults.

PubMed

Blumen, Helena M; Stern, Yaakov

2011-01-01

A recent study of younger adults suggests that, compared to repeated individual recall trials, repeated collaborative recall trials produce better individual recall after a short delay (Blumen & Rajaram, 2008). Our study was designed to determine if such collaboration benefits would remain after a one-week delay, in both younger and older adults. Sixty younger (M age = 24.60) and 60 older (M age = 67.35) adults studied a list of words and then completed either two collaborative recall trials followed by two individual recall trials, or four individual recall trials. A five-min delay was inserted between the first three recall trials. The fourth recall trial was administered 1 week later. Collaborative recall was completed in groups of three individuals working together. Both younger and older adults benefitted from repeated collaborative recall trials to a greater extent than repeated individual recall trials, and such collaboration benefits remained after a one-week delay. This is the first demonstration of collaboration benefits on later individual recall at delays as long as 1 week, in both younger and older adults. Findings are discussed within the context of the negative effects of collaboration associated with group memory (collaborative inhibition) and the positive effects of collaboration associated with later individual memory (collaboration benefits).

Time perspective and social preference in older and younger adults: Effects of self-regulatory fatigue.

PubMed

Segerstrom, Suzanne C; Geiger, Paul J; Combs, Hannah L; Boggero, Ian A

2016-09-01

Socioemotional selectivity theory predicts that when perceived time in life is limited, people will prefer emotionally close social partners over less emotionally rewarding partners. Regulating social choices with regard to time perspective can make the best use of time with regard to well-being. However, doing so may depend on the self-regulatory capacity of the individual. Two studies, 1 with younger adults (N = 101) and 1 with younger (N = 42) and older (N = 39) adults, experimentally tested the effects of time perspective and self-regulatory fatigue on preferences for emotionally close partners and knowledgeable partners. In both studies and across younger and older adults, when self-regulatory fatigue was low, the perception of limited time resulted in a greater preference for close social partners relative to knowledgeable social partners. However, this shift was eliminated by self-regulatory fatigue. In Study 2, when fatigued, younger adults preferred close social partners to knowledgeable partners across time perspectives; older adults preferred close and knowledgeable partners more equally across time perspectives. These findings have implications for social decision-making and satisfaction among people who experience chronic self-regulatory fatigue. They also contradict previous suggestions that only younger adults are susceptible to self-regulatory fatigue. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Time Perspective and Social Preference in Older and Younger Adults: Effects of Self-Regulatory Fatigue

PubMed Central

Segerstrom, Suzanne C.; Geiger, Paul J.; Combs, Hannah L.; Boggero, Ian A.

2016-01-01

Socioemotional selectivity theory predicts that when perceived time in life is limited, people will prefer emotionally close social partners over less emotionally rewarding partners. Regulating social choices with regard to time perspective can make the best use of time with regard to well-being. However, doing so may depend on the self-regulatory capacity of the individual. Two studies, one with younger adults (N = 101) and one with younger (N = 42) and older (N = 39) adults, experimentally tested the effects of time perspective and self-regulatory fatigue on preferences for emotionally close partners and knowledgeable partners. In both studies and across younger and older adults, when self-regulatory fatigue was low, the perception of limited time resulted in a greater preference for close social partners relative to knowledgeable social partners. However, this shift was eliminated by self-regulatory fatigue. In Study 2, when fatigued, younger adults preferred close social partners to knowledgeable partners across time perspectives; older adults preferred close and knowledgeable partners more equally across time perspectives. These findings have implications for social decision-making and satisfaction among people who experience chronic self-regulatory fatigue. They also contradict previous suggestions that only younger adults are susceptible to self-regulatory fatigue. PMID:27243763

Positive Outcomes Enhance Incidental Learning for Both Younger and Older Adults

PubMed Central

Mather, Mara; Schoeke, Andrej

2011-01-01

Previous studies suggest that memory encoding is enhanced when people are anticipating a potential reward, consistent with the idea that dopaminergic systems that respond to motivationally relevant information also enhance memory for that information. In the current study, we examined how anticipating and receiving rewards versus losses affect incidental learning of information. In addition, we compared the modulatory effects of reward anticipation and outcome on memory for younger and older adults. Forty-two younger (aged 18–33 years) and 44 older (aged 66–92 years) adults played a game involving pressing a button as soon as they saw a target. Gain trials began with a cue that they would win $0.25 if they pressed the button fast enough, loss trials began with a cue that they would avoid losing $0.25 if they pressed the button fast enough, and no-outcome trials began with a cue indicating no monetary outcome. The target was a different photo-object on each trial (e.g., balloon, dolphin) and performance outcomes were displayed after the photo disappeared. Both younger and older adults recalled and recognized pictures from trials with positive outcomes (either rewarding or loss avoiding) better than from trials with negative outcomes. Positive outcomes were associated with not only enhanced memory for the picture just seen in that trial, but also with enhanced memory for the pictures shown in the next two trials. Although anticipating a reward also enhanced incidental memory, this effect was seen only in recognition memory of positive pictures and was a smaller effect than the outcome effect. The fact that older adults showed similar incidental memory effects of reward anticipation and outcome as younger adults suggests that reward–memory system interactions remain intact in older age. PMID:22125509

Postural adjustment errors during lateral step initiation in older and younger adults

PubMed Central

Sparto, Patrick J.; Fuhrman, Susan I.; Redfern, Mark S.; Perera, Subashan; Jennings, J. Richard; Furman, Joseph M.

2016-01-01

The purpose was to examine age differences and varying levels of step response inhibition on the performance of a voluntary lateral step initiation task. Seventy older adults (70 – 94 y) and twenty younger adults (21 – 58 y) performed visually-cued step initiation conditions based on direction and spatial location of arrows, ranging from a simple choice reaction time task to a perceptual inhibition task that included incongruous cues about which direction to step (e.g. a left pointing arrow appearing on the right side of a monitor). Evidence of postural adjustment errors and step latencies were recorded from vertical ground reaction forces exerted by the stepping leg. Compared with younger adults, older adults demonstrated greater variability in step behavior, generated more postural adjustment errors during conditions requiring inhibition, and had greater step initiation latencies that increased more than younger adults as the inhibition requirements of the condition became greater. Step task performance was related to clinical balance test performance more than executive function task performance. PMID:25595953

Postural adjustment errors during lateral step initiation in older and younger adults

PubMed Central

Sparto, Patrick J.; Fuhrman, Susan I.; Redfern, Mark S.; Perera, Subashan; Jennings, J. Richard; Furman, Joseph M.

2014-01-01

The purpose was to examine age differences and varying levels of step response inhibition on the performance of a voluntary lateral step initiation task. Seventy older adults (70 – 94 y) and twenty younger adults (21 – 58 y) performed visually-cued step initiation conditions based on direction and spatial location of arrows, ranging from a simple choice reaction time task to a perceptual inhibition task that included incongruous cues about which direction to step (e.g. a left pointing arrow appearing on the right side of a monitor). Evidence of postural adjustment errors and step latencies were recorded from vertical ground reaction forces exerted by the stepping leg. Compared with younger adults, older adults demonstrated greater variability in step behavior, generated more postural adjustment errors during conditions requiring inhibition, and had greater step initiation latencies that increased more than younger adults as the inhibition requirements of the condition became greater. Step task performance was related to clinical balance test performance more than executive function task performance. PMID:25183162

Goal-setting, self-efficacy, and memory performance in older and younger adults.

PubMed

West, R L; Thorn, R M

2001-01-01

Research in field and laboratory settings has shown that goals lead to improved self-efficacy and performance, especially when individuals also receive positive feedback. The present study extended goal-setting theory to examine self-set goals and feedback in relation to younger and older adults' memory performance and self-efficacy. Following a baseline recall trial, participants completed three shopping list recall trials. Half of the participants were instructed to set goals for the three experimental trials, and half in each goal condition received performance feedback after each trial. Young adults' self-efficacy, clustering, and recall exceeded that of older adults. Goal setting increased self-efficacy for younger but not older adults, and it did not affect performance. Younger adults and participants in the feedback condition increased their goals across trials, as did participants for whom feedback indicated success. These data provide a first look at the motivational impact of feedback and self-set recall goals in memory aging. Additional study is needed to understand the interactive effects of type of feedback, memory task difficulty, and type of goal setting at different ages.

The effect of exercise on affective and self-efficacy responses in older and younger women.

PubMed

Barnett, Fiona

2013-01-01

This study examined the self-efficacy and affective responses to an acute exercise bout in sedentary older and younger women to determine whether aging has an effect on affective states. Twenty-five sedentary younger (mean age = 19.9 yrs) and 25 older (mean age = 55.7 yrs) women completed an acute bout of exercise. Affective responses were measured before, during, and immediately following exercise. Self-efficacy responses were measured before and immediately following exercise. Positive engagement, revitalization, tranquility, Felt Arousal and Feeling Scale responses, and self-efficacy were all higher immediately following compared with before or during exercise for both groups of women. In addition, older women experienced higher overall positive engagement and lower physical exhaustion compared with younger women as well as higher tranquility and Feeling Scale responses immediately following exercise. This investigation found that an acute bout of moderate-intensity exercise produced more positive and fewer negative affective states in both younger and older women.

The Impact of Presentation Format on Younger and Older Adults' Self-Regulated Learning.

PubMed

Price, Jodi

2017-01-01

Background/Study Context: Self-regulated learning involves deciding what to study and for how long. Debate surrounds whether individuals' selections are influenced more by item complexity, point values, or if instead people select in a left-to-right reading order, ignoring item complexity and value. The present study manipulated whether point values and presentation format favored selection of simple or complex Chinese-English pairs to assess the impact on younger and older adults' selection behaviors. One hundred and five younger (M age  = 20.26, SD = 2.38) and 102 older adults (M age  = 70.28, SD = 6.37) participated in the experiment. Participants studied four different 3 × 3 grids (two per trial), each containing three simple, three medium, and three complex Chinese-English vocabulary pairs presented in either a simple-first or complex-first order, depending on condition. Point values were assigned in either a 2-4-8 or 8-4-2 order so that either simple or complex items were favored. Points did not influence the order in which either age group selected items, whereas presentation format did. Younger and older adults selected more simple or complex items when they appeared in the first column. However, older adults selected and allocated more time to simpler items but recalled less overall than did younger adults. Memory beliefs and working memory capacity predicted study time allocation, but not item selection, behaviors. Presentation format must be considered when evaluating which theory of self-regulated learning best accounts for younger and older adults' study behaviors and whether there are age-related differences in self-regulated learning. The results of the present study combine with others to support the importance of also considering the role of external factors (e.g., working memory capacity and memory beliefs) in each age group's self-regulated learning decisions.

The prone bridge test: Performance, validity, and reliability among older and younger adults.

PubMed

Bohannon, Richard W; Steffl, Michal; Glenney, Susan S; Green, Michelle; Cashwell, Leah; Prajerova, Kveta; Bunn, Jennifer

2018-04-01

The prone bridge maneuver, or plank, has been viewed as a potential alternative to curl-ups for assessing trunk muscle performance. The purpose of this study was to assess prone bridge test performance, validity, and reliability among younger and older adults. Sixty younger (20-35 years old) and 60 older (60-79 years old) participants completed this study. Groups were evenly divided by sex. Participants completed surveys regarding physical activity and abdominal exercise participation. Height, weight, body mass index (BMI), and waist circumference were measured. On two occasions, 5-9 days apart, participants held a prone bridge until volitional exhaustion or until repeated technique failure. Validity was examined using data from the first session: convergent validity by calculating correlations between survey responses, anthropometrics, and prone bridge time, known groups validity by using an ANOVA comparing bridge times of younger and older adults and of men and women. Test-retest reliability was examined by using a paired t-test to compare prone bridge times for Session1 and Session 2. Furthermore, an intraclass correlation coefficient (ICC) was used to characterize relative reliability and minimal detectable change (MDC 95% ) was used to describe absolute reliability. The mean prone bridge time was 145.3 ± 71.5 s, and was positively correlated with physical activity participation (p ≤ 0.001) and negatively correlated with BMI and waist circumference (p ≤ 0.003). Younger participants had significantly longer plank times than older participants (p = 0.003). The ICC between testing sessions was 0.915. The prone bridge test is a valid and reliable measure for evaluating abdominal performance in both younger and older adults. Copyright © 2017 Elsevier Ltd. All rights reserved.

Older and Younger Workers: The Equalling Effects of Health

ERIC Educational Resources Information Center

Beck, Vanessa; Quinn, Martin

2012-01-01

Purpose: The purpose of this paper is to consider the statistical evidence on the effects that ill health has on labour market participation and opportunities for younger and older workers in the East Midlands (UK). Design/methodology/approach: A statistical analysis of Labour Force Survey data was undertaken to demonstrate that health issues…

Fatigue in Younger and Older Drivers: Effectiveness of an Alertness-Maintaining Task.

PubMed

Song, Woojin; Woon, Fu L; Doong, Alice; Persad, Carol; Tijerina, Louis; Pandit, Pooja; Cline, Carol; Giordani, Bruno

2017-09-01

The aim of this study was to examine the effects of an alertness-maintaining task (AMT) in older, fatigued drivers. Fatigue during driving increases crash risk, and previous research suggests that alertness and driving in younger adults may be improved using a secondary AMT during boring, fatigue-eliciting drives. However, the potential impact of an AMT on driving has not been investigated in older drivers whose ability to complete dual tasks has been shown to decline and therefore may be negatively affected with an AMT in driving. Younger ( n = 29) and older drivers ( n = 39) participated in a 50-minute simulated drive designed to induce fatigue, followed by four 10-minute sessions alternating between driving with and without an AMT. Younger drivers were significantly more affected by fatigue on driving performance than were older drivers but benefitted significantly from the AMT. Older drivers did not demonstrate increased driver errors with fatigue, and driving did not deteriorate significantly during participation in the AMT condition, although their speed was significantly more variable with the AMT. Consistent with earlier research, an AMT applied during fatiguing driving is effective in improving alertness and reducing driving errors in younger drivers. Importantly, older drivers were relatively unaffected by fatigue, and use of an AMT did not detrimentally affect their driving performance. These results support the potential use of an AMT as a new automotive technology to improve fatigue and promote driver safety, though the benefits of such technology may differ between different age groups.

The impact of breast cancer-specific birth cohort effects among younger and older Chinese populations.

PubMed

Sung, Hyuna; Rosenberg, Philip S; Chen, Wan-Qing; Hartman, Mikael; Lim, Wei-Yen; Chia, Kee Seng; Wai-Kong Mang, Oscar; Tse, Lapah; Anderson, William F; Yang, Xiaohong R

2016-08-01

Historically low breast cancer incidence rates among Asian women have risen worldwide; purportedly due to the adoption of a "Western" life style among younger generations (i.e., the more recent birth cohorts). However, no study has simultaneously compared birth cohort effects between both younger and older women in different Asian and Western populations. Using cancer registry data from rural and urban China, Singapore and the United States (1990-2008), we estimated age-standardized incidence rates (ASR), annual percentage change (EAPC) in the ASR, net drifts, birth cohort specific incidence rates and cohort rate ratios (CRR). Younger (30-49 years, 1943-1977 birth cohorts) and older women (50-79 years; 1913-1957 birth cohorts) were assessed separately. CRRs among Chinese populations were estimated using birth cohort specific rates with US non-Hispanic white women (NHW) serving as the reference population with an assigned CRR of 1.0. We observed higher EAPCs and net drifts among those Chinese populations with lower ASRs. Similarly, we observed the most rapidly increasing cohort-specific incidence rates among those Chinese populations with the lowest baseline CRRs. Both trends were more significant among older than younger women. Average CRRs were 0.06-0.44 among older and 0.18-0.81 among younger women. Rapidly rising cohort specific rates have narrowed the historic disparity between Chinese and US NHW breast cancer populations particularly in regions with the lowest baseline rates and among older women. Future analytic studies are needed to investigate risk factors accounting for the rapid increase of breast cancer among older and younger women separately in Asian populations. © 2016 UICC.

Comparison and evaluation of dietary quality between older and younger Mexican-American women.

PubMed

Pignotti, Giselle A P; Vega-López, Sonia; Keller, Colleen; Belyea, Michael; Ainsworth, Barbara; Nagle Williams, Allison; Records, Kathie; Coonrod, Dean; Permana, Paska

2015-10-01

To compare and evaluate the dietary quality of young and older sedentary Mexican-American women. Understanding key dietary concerns, while considering developmental transition periods and cultural relevance, can provide insight for developing appropriate nutrition interventions. Cross-sectional dietary data were collected using unannounced 24 h diet recalls to assess nutrient intake adequacy (Estimated Average Requirement cut-point method) and dietary quality (Healthy Eating Index (HEI) 2010). Mujeres en Acción and Madres para la Salud, two community-based physical activity interventions. Participants were 139 young (28 (sd 6) years) and 124 older (55 (sd 7) years) overweight/obese sedentary Mexican-American women (BMI=25·0-35·0 kg/m2) of low socio-economic status. Older women consumed less Ca, Fe, folate, empty calories and energy from carbohydrate, but more fruit, vegetables, greens and beans, and fibre than younger women (all P<0·05). Over 60 % of all participants had an intake below recommendations for fibre, Ca, vitamin E, vitamin C and folate. Both groups had low total HEI-2010 scores (62 for older and 63 for younger women; NS), with 57 % of older and 48 % of younger women classified as having a poor diet. Despite differences in nutrient requirements according to developmental transition periods (childbearing v. perimenopausal), overall, older and younger Mexican-American women generally had low-quality diets and may benefit from dietary quality improvement.

Task Inhibition and Response Inhibition in Older vs. Younger Adults: A Diffusion Model Analysis

PubMed Central

Schuch, Stefanie

2016-01-01

Differences in inhibitory ability between older (64–79 years, N = 24) and younger adults (18–26 years, N = 24) were investigated using a diffusion model analysis. Participants performed a task-switching paradigm that allows assessing n−2 task repetition costs, reflecting inhibitory control on the level of tasks, as well as n−1 response-repetition costs, reflecting inhibitory control on the level of responses. N−2 task repetition costs were of similar size in both age groups. Diffusion model analysis revealed that for both younger and older adults, drift rate parameters were smaller in the inhibition condition relative to the control condition, consistent with the idea that persisting task inhibition slows down response selection. Moreover, there was preliminary evidence for task inhibition effects in threshold separation and non-decision time in the older, but not the younger adults, suggesting that older adults might apply different strategies when dealing with persisting task inhibition. N−1 response-repetition costs in mean RT were larger in older than younger adults, but in mean error rates tended to be larger in younger than older adults. Diffusion-model analysis revealed longer non-decision times in response repetitions than response switches in both age groups, consistent with the idea that motor processes take longer in response repetitions than response switches due to persisting response inhibition of a previously executed response. The data also revealed age-related differences in overall performance: Older adults responded more slowly and more accurately than young adults, which was reflected by a higher threshold separation parameter in diffusion model analysis. Moreover, older adults showed larger non-decision times and higher variability in non-decision time than young adults, possibly reflecting slower and more variable motor processes. In contrast, overall drift rate did not differ between older and younger adults. Taken together

Self-Regulated Learning in Younger and Older Adults: Does Aging Affect Metacognitive Control?

PubMed Central

Price, Jodi; Hertzog, Christopher; Dunlosky, John

2011-01-01

Two experiments examined whether younger and older adults’ self-regulated study (item selection and study time) conformed to the region of proximal learning (RPL) model when studying normatively easy, medium, and difficult vocabulary pairs. Experiment 2 manipulated the value of recalling different pairs and provided learning goals for words recalled and points earned. Younger and older adults in both experiments selected items for study in an easy-to-difficult order, indicating the RPL model applies to older adults’ self-regulated study. Individuals allocated more time to difficult items, but prioritized easier items when given less time or point values favoring difficult items. Older adults studied more items for longer but realized lower recall than did younger adults. Older adults’ lower memory self-efficacy and perceived control correlated with their greater item restudy and avoidance of difficult items with high point values. Results are discussed in terms of RPL and agenda-based regulation models. PMID:19866382

Younger Veterans - Older Veterans: A Comparison of Perceptions of Hospital Treatment, Problem Areas and Needs.

ERIC Educational Resources Information Center

Dickman, Harold R.; Pearson, Helen J.

The contention that younger veterans differ from their elders in their attitudes and expectations was shown to be an inaccurate generalization on the basis of this reported inquiry. Three general classes of informational data were collected from both younger and older veterans: (1) perception of hospital services; (2) patient problems and services…

Comparison of Autism Screening in Younger and Older Toddlers

ERIC Educational Resources Information Center

Sturner, Raymond; Howard, Barbara; Bergmann, Paul; Stewart, Lydia; Afarian, Talin E.

2017-01-01

This study examined the effect of age at completion of an autism screening test on item failure rates contrasting older (>20 months) with younger (<20 months) toddlers in a community primary care sample of 73,564 children. Items related to social development were categorized into one of three age sets per criteria from Inada et al.…

Early social-communicative and cognitive development of younger siblings of children with autism spectrum disorders.

PubMed

Stone, Wendy L; McMahon, Caitlin R; Yoder, Paul J; Walden, Tedra A

2007-04-01

To compare the early social-communicative development of younger siblings of children with autism spectrum disorders (ASDs) with that of younger siblings of children with typical development, using parental report and child-based measures. Group comparison. Vanderbilt University, between July 1, 2003, and July 31, 2006. Younger siblings of children with ASD (n = 64) and younger siblings of children with typical development (n = 42) between the ages of 12 and 23 months (mean, 16 months). Main Exposure Having a sibling with an ASD. Child-based measures included a cognitive assessment; an interactive screening tool assessing play, imitation, and communication; and a rating of autism symptoms. Parental report measures were an interview of social-communicative interactions and a questionnaire assessing language and communication skills. Younger siblings of children with ASD demonstrated weaker performance in nonverbal problem solving (mean difference [MD], 5.91; 95% confidence interval [CI], 2.48-9.34), directing attention (MD, 0.52; 95% CI, 0.07-0.97), understanding words (MD, 33.30; 95% CI, 3.11-63.48), understanding phrases (MD, 4.56; 95% CI, 1.85-7.27), gesture use (MD, 1.49; 95% CI, 0.51-2.47), and social-communicative interactions with parents (MD, 1.32; 95% CI, 0.27-2.37), and had increased autism symptoms (MD, 2.54; 95% CI, 1.05-4.03), relative to control siblings. A substantial minority of the ASD sibling group exhibited lower performance relative to controls. Significant correlations between child-based measures and parental reports assessing similar constructs were found (r = -0.74 to 0.53; P range, .000-.002). The weaker performance found for children in the ASD sibling group may represent early-emerging features of the broader autism phenotype, thus highlighting the importance of developmental surveillance for younger siblings.

Comparing older and younger Japanese primiparae: fatigue, depression and biomarkers of stress.

PubMed

Mori, Emi; Maehara, Kunie; Iwata, Hiroko; Sakajo, Akiko; Tsuchiya, Miyako; Ozawa, Harumi; Morita, Akiko; Maekawa, Tomoko; Saeki, Akiko

2015-03-01

This cohort study of primiparae was conducted to answer the following questions: Do older (≧ 35 years) and younger (20-29 years) Japanese primiparous mothers differ when comparing biomarkers of stress and measures of fatigue and depression? Are there changes in fatigue, depression and stress biomarkers when comparing older and younger mothers during the postpartum period? The Postnatal Accumulated Fatigue Scale and the Edinburgh Postnatal Depression Scale were administered in a time-series method four times: shortly after birth and monthly afterwards. Assays to measure biomarkers of stress, urinary 17-ketosteroids, urinary 17-hydroxycorticosteroids and salivary chromogranin-A, were collected shortly after delivery and at 1 month postpartum in both groups and a third time in older mothers at the 4th month. Statistical testing showed very little difference in fatigue, depression or stress biomarkers between older and younger mothers shortly after birth or 1 month later. Accumulated fatigue and depression scores of older mothers were highest 1 month after delivery. Additional cohort studies are required to characterize physical/psychological well-being of older Japanese primiparae. © 2015 Wiley Publishing Asia Pty Ltd.

Revised Quaternary glacial succession and post-LGM recession, southern Wind River Range, Wyoming, USA

NASA Astrophysics Data System (ADS)

Dahms, Dennis; Egli, Markus; Fabel, Derek; Harbor, Jon; Brandová, Dagmar; de Castro Portes, Raquel; Christl, Marcus

2018-07-01

allostratigraphic units in the cirques of Stough Basin and Cirque of the Towers show general equivalence to the stadial event just prior to the onset of the Bølling interstadial (17.5-14.7 ka) and to the Intra-Allerød Cold Period-Younger Dryas stadial phase (13.9-11.7 ka), respectively. From this evidence, the Temple Lake Alloformation of the Wind River Mountains now should correspond to the INTIMATE GS-2.1a (Oldest Dryas) stadial event while the Alice Lake Alloformation should correspond to the INTIMATE GS-2 stadial (IACP-Younger Dryas). Thus, we consider that evidence no longer exists for early-to mid-Holocene glacial events in the southern Wind River Range.

Body image after mastectomy: A thematic analysis of younger women's written accounts.

PubMed

Grogan, Sarah; Mechan, Jayne

2017-09-01

This study investigated younger women's body image after mastectomy. In all, 49 women, aged 29-53 years (mean age: 39 years) who had had bilateral ( n = 8) or unilateral ( n = 41) mastectomy responded to open-ended questions online. Inductive thematic analysis revealed that aesthetics were less important than survival between diagnosis and mastectomy. Following mastectomy, women negotiated new body identities. Treatment effects such as weight gain were significant concerns. However, impacts on body confidence varied, and some participants rejected mainstream body shape ideals and reported feeling proud of their scars. Implications for supporting younger women post-mastectomy, including promotion of body acceptance, are discussed.

Migraine in a pediatric population: a clinical study in children younger than 7 years of age.

PubMed

Raieli, Vincenzo; Pitino, Renata; Giordano, Giuliana; Spitalieri, Chiara; Consolo, Flavia; Puma, Domenico; Santangelo, Giuseppe; Vanadia, Francesca; D'Amelio, Marco

2015-06-01

Migraines in children younger than 7 years of age have received limited attention in the published literature. The aim of this study is to describe the characteristics of migraine phenotypes in children younger than 7 years, and to compare them with migraines in children older than 7 years of age. We reviewed all standard clinical files, collected over 4 years, related to children with a diagnosis of primary headache. We included all children younger than 7 years diagnosed with migraine in our study. A total of 374 children (188 males, 186 females) were affected by migraine with/without aura: 40 of these patients (10.7%; 20 males, 20 females; mean age 5y 7mo, SD 1y 2mo) where younger than 7 years old. The frequencies of the main migraine features in the younger age group were similar to those of children older than 7 years, with the exception of a shorter duration of migraine and reduced frequency of attacks. In children younger than 7 years of age, the clinical phenotype of migraine is similar to that seen in older children. We propose that there is a general genetic migraine susceptibility that, in the presence of activating environmental factors, may induce typical attacks of migraine in individuals already predisposed to migraine attacks. Therefore, different modules induce different clinical features within the different age groups, but there is no difference in the frequencies of clinical phenotypes between the two age groups. © 2015 Mac Keith Press.

The Effects of Prior Exposure on Face Processing in Younger and Older Adults

PubMed Central

Heisz, Jennifer J.; Ryan, Jennifer D.

2011-01-01

Older adults differ from their younger counterparts in the way they view faces. We assessed whether older adults can use past experience to mitigate these typical face-processing differences; that is, we examined whether there are age-related differences in the use of memory to support current processing. Eye movements of older and younger adults were monitored as they viewed faces that varied in the type/amount of prior exposure. Prior exposure was manipulated by including famous and novel faces, and by presenting faces up to five times. We expected that older adults may have difficulty quickly establishing new representations to aid in the processing of recently presented faces, but would be able to invoke face representations that have been stored in memory long ago to aid in the processing of famous faces. Indeed, younger adults displayed effects of recent exposure with a decrease in the total fixations to the faces and a gradual increase in the proportion of fixations to the eyes. These effects of recent exposure were largely absent in older adults. In contrast, the effect of fame, revealed by a subtle increase in fixations to the inner features of famous compared to non-famous faces, was similar for younger and older adults. Our results suggest that older adults’ current processing can benefit from lifetime experience, however the full benefit of recent experience on face processing is not realized in older adults. PMID:22007169

Teasing in younger and older children with microtia before and after ear reconstruction.

PubMed

Johns, Alexis L; Lewin, Sheryl L; Im, Daniel D

2017-06-01

This study prospectively measured teasing and emotional adjustment before and after ear reconstruction in younger and older children with microtia. Participants with isolated microtia (n = 28) were divided into two groups by age at surgery, with a younger group aged 3-5 years (n = 13) with a mean age of 4.0 (0.71) years at the time of surgery and an older group aged 6-10 years old (n = 15) with a mean age of 7.87 (1.30) years. Children and their parents were interviewed preoperatively and a year after surgery about teasing and emotions about their ear(s). Teasing began between the ages of 2.4-4.8 years. A third of the younger group and all of the older group reported preoperative teasing. Before surgery, the older group reported higher rates of negative emotions about their ear(s) and teasing was correlated for all ages with feeling sad, worried, and mad about their ear(s). After surgery, teasing and negative emotions significantly decreased with increased happiness about their ear(s). Postoperative teasing was correlated with trying to hide their ear(s). There were significant interactions from before to after surgery based on surgery age for frequency of teasing, sadness, and feeling mad, with the older group showing relatively greater change postoperatively. Teasing and negative emotions about their ear(s) decreased for all ages after surgery, with a potential protective factor seen in younger surgery age.

The cognitive control of emotional versus value-based information in younger and older adults.

PubMed

Eich, Teal S; Castel, Alan D

2016-08-01

We investigated age-related changes in the cognitive control of value-based and emotionally valenced information. In 2 experiments, participants completed a selectivity task in which to-be-recalled words differed in value and emotional salience. In Experiment 1, all low-valued words were emotional, and emotional valence (positive/negative) was manipulated between subjects. In Experiment 2, valence was manipulated within subjects, with the addition of a control condition in which all words (emotional and neutral) were equally valued. We found that older and younger adults recalled more neutral words than emotional words in both experiments when emotional words were low-valued, and more emotional words than neutral words in the control condition. Emotion did not interact with age in either experiment, suggesting that the impact of emotional saliency on memory is age-invariant. We also found that the number of items recalled was lower for older compared to younger adults in both experiments. Despite this, older and younger adults showed equivalent selectivity in terms of which words they recalled. These results suggest that older adults employ strategic control and use value-based information to guide memory processes equivalently to younger adults, even in the face of salient emotional information. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Otological diagnoses and probable age-related auditory neuropathy in "younger" and "older" elderly persons.

PubMed

Rosenhall, Ulf; Hederstierna, Christina; Idrizbegovic, Esma

2011-09-01

Audiological data from a population based epidemiological investigation were studied on elderly persons. Specific diagnoses of otological and audiological disorders, which can result in hearing loss, were searched for. A retrospective register study. Three age cohorts, 474 70- and 75-year olds ("younger"), and 252 85-year olds ("older"), were studied. Clinical pure tone and speech audiometry was used. Data from medical files were included. Conductive hearing loss was diagnosed in 6.1% of the "younger" elderly persons, and in 10.3% of the "older" ones. Specific diagnoses (chronic otitis media and otosclerosis) were established in about half of the cases. Sensorineural hearing loss, other than age-related hearing loss and noise induced hearing loss, was diagnosed in 3.4 % and 5.2% respectively. Severely impaired speech recognition, possibly reflecting age-related auditory neuropathy, was found in 0.4% in the "younger" group, and in 10% in the "older" group. Bilateral functional deafness was present in 3.2% of the 85-year-old persons, but was not present in the 70-75-year group. The incidence of probable age-related auditory neuropathy increases considerably from 70-75 to 85 years. There are marked differences between "younger" and "older" elderly persons regarding hearing loss that severely affects oral communication.

Addressing Younger Workers' Needs: The Promoting U through Safety and Health (PUSH) Trial Outcomes.

PubMed

Rohlman, Diane S; Parish, Megan; Elliot, Diane L; Hanson, Ginger; Perrin, Nancy

2016-08-10

Most younger workers, less than 25 years old, receive no training in worker safety. We report the feasibility and outcomes of a randomized controlled trial of an electronically delivered safety and health curriculum for younger workers entitled, PUSH (Promoting U through Safety and Health). All younger workers (14-24 years old) hired for summer work at a large parks and recreation organization were invited to participate in an evaluation of an online training and randomized into an intervention or control condition. Baseline and end-of-summer online instruments assessed acceptability, knowledge, and self-reported attitudes and behaviors. One-hundred and forty participants (mean age 17.9 years) completed the study. The innovative training was feasible and acceptable to participants and the organization. Durable increases in safety and health knowledge were achieved by intervention workers (p < 0.001, effect size (Cohen's d) 0.4). However, self-reported safety and health attitudes did not improve with this one-time training. These results indicate the potential utility of online training for younger workers and underscore the limitations of a single training interaction to change behaviors. Interventions may need to be delivered over a longer period of time and/or include environmental components to effectively alter behavior.

Addressing Younger Workers’ Needs: The Promoting U through Safety and Health (PUSH) Trial Outcomes

PubMed Central

Rohlman, Diane S.; Parish, Megan; Elliot, Diane L.; Hanson, Ginger; Perrin, Nancy

2016-01-01

Most younger workers, less than 25 years old, receive no training in worker safety. We report the feasibility and outcomes of a randomized controlled trial of an electronically delivered safety and health curriculum for younger workers entitled, PUSH (Promoting U through Safety and Health). All younger workers (14–24 years old) hired for summer work at a large parks and recreation organization were invited to participate in an evaluation of an online training and randomized into an intervention or control condition. Baseline and end-of-summer online instruments assessed acceptability, knowledge, and self-reported attitudes and behaviors. One-hundred and forty participants (mean age 17.9 years) completed the study. The innovative training was feasible and acceptable to participants and the organization. Durable increases in safety and health knowledge were achieved by intervention workers (p < 0.001, effect size (Cohen’s d) 0.4). However, self-reported safety and health attitudes did not improve with this one-time training. These results indicate the potential utility of online training for younger workers and underscore the limitations of a single training interaction to change behaviors. Interventions may need to be delivered over a longer period of time and/or include environmental components to effectively alter behavior. PMID:27517968

The effect of foveal and parafoveal masks on the eye movements of older and younger readers.

PubMed

Rayner, Keith; Yang, Jinmian; Schuett, Susanne; Slattery, Timothy J

2014-06-01

In the present study, we examined foveal and parafoveal processing in older compared with younger readers by using gaze-contingent paradigms with 4 conditions. Older and younger readers read sentences in which the text was either a) presented normally, b) the foveal word was masked as soon as it was fixated, c) all of the words to the left of the fixated word were masked, or d) all of the words to the right of the fixated word were masked. Although older and younger readers both found reading when the fixated word was masked quite difficult, the foveal mask increased sentence reading time more than 3-fold (3.4) for the older readers (in comparison with the control condition in which the sentence was presented normally) compared with the younger readers who took 1.3 times longer to read sentences in the foveal mask condition (in comparison with the control condition). The left and right parafoveal masks did not disrupt reading as severely as the foveal mask, though the right mask was more disruptive than the left mask. Also, there was some indication that the younger readers found the right mask condition relatively more disruptive than the left mask condition. PsycINFO Database Record (c) 2014 APA, all rights reserved.

Liver Transplantation With Older Donors: A Comparison With Younger Donors in a Context of Organ Shortage.

PubMed

Barbier, Louise; Cesaretti, Manuela; Dondero, Federica; Cauchy, François; Khoy-Ear, Linda; Aoyagi, Takeshi; Weiss, Emmanuel; Roux, Olivier; Dokmak, Safi; Francoz, Claire; Paugam-Burtz, Catherine; Sepulveda, Ailton; Belghiti, Jacques; Durand, François; Soubrane, Olivier

2016-11-01

Older liver grafts have been considered in the past decade due to organ shortage. The aim was to compare outcomes after liver transplantation with either younger or older donors. Patients transplanted in our center between 2004 and 2014 with younger donors (younger than 60 years; n = 253) were compared with older donors (older than 75 years; n = 157). Multiorgan transplantations, split grafts, or non-heart-beating donors were not included. Donors in the older group were mostly women deceased from stroke, and only 3 patients had experienced cardiac arrest. Liver tests were significantly better in the older group than in the younger group. There was no difference regarding cold ischemia time, model for end-stage liver disease score, and steatosis. There was no significant difference regarding primary nonfunction and dysfunction, hepatic artery and biliary complications, and retransplantation rates. Graft survival was not different (65% and 64% in the older and younger groups, P = 0.692). Within the older group, hepatitis C infection, retransplantation, and emergency transplantation were associated with poor graft survival. Provided normal liver tests and the absence of cardiac arrest in donors, older liver grafts (>75 years) may be safely attributed to non-hepatitis C-infected recipients in the setting of a first and nonurgent transplantation.

Vaccination of day-care center attendees reduces carriage of Streptococcus pneumoniae among their younger siblings.

PubMed

Givon-Lavi, Noga; Fraser, Drora; Dagan, Ron

2003-06-01

We conducted a study to determine whether administration of a pneumococcal conjugate vaccine to toddlers attending day-care centers (DCCs) could prevent acquisition of Streptococcus pneumoniae of the vaccine serotypes (VT) by their younger siblings. In a double blind study, 262 DCC attendees ages 12 to 35 months were randomized to receive a 9-valent pneumococcal conjugate vaccine (PnCRM9; n = 132), or a control vaccine (meningococcus C vaccine; n = 130). It was planned to follow the groups for 2 years with monthly nasopharyngeal pneumococcal cultures during the first follow-up year and every 2 months during the second year. Forty-six younger siblings of the above described children, age <18 months (23 siblings of the PnCRM9 recipients and 23 of the controls), were also enrolled, and nasopharyngeal cultures were obtained monthly until the children reached the age of 18 months or started to attend DCC, if before the age of 18 months. Pneumococcal isolates were serotyped and tested for antibiotic susceptibility. Of the 3748 cultures obtained from the DCC attendees, 2450 (65%) were positive for S. pneumoniae. Of 306 cultures obtained from the younger siblings, 151 (49%) were positive. Among the PnCRM9 recipients, cultures were significantly less frequently positive for the VT S. pneumoniae than among the controls (13% vs. 21%, respectively; P < 0.001). The same pattern was seen in the younger siblings of PnCRM9 recipients vs. the siblings of controls (21% vs. 34%, respectively; P = 0.017). The reverse trend was seen for non-VT strains in both the DCC attendees (44% vs. 34%, respectively; P < 0.001) and their younger siblings (19% vs. 13%, respectively; P = 0.15). There was a significant decrease in the carriage rate of antibiotic-resistant S. pneumoniae in both the PnCRM9 recipients and their younger siblings. The relative risks (and 95% confidence intervals) to carry S. pneumoniae penicillin-nonsusceptible, resistant to > or =1, > or =2 and > or =3 antibiotic

Variability in reaction time performance of younger and older adults.

PubMed

Hultsch, David F; MacDonald, Stuart W S; Dixon, Roger A

2002-03-01

Age differences in three basic types of variability were examined: variability between persons (diversity), variability within persons across tasks (dispersion), and variability within persons across time (inconsistency). Measures of variability were based on latency performance from four measures of reaction time (RT) performed by a total of 99 younger adults (ages 17--36 years) and 763 older adults (ages 54--94 years). Results indicated that all three types of variability were greater in older compared with younger participants even when group differences in speed were statistically controlled. Quantile-quantile plots showed age and task differences in the shape of the inconsistency distributions. Measures of within-person variability (dispersion and inconsistency) were positively correlated. Individual differences in RT inconsistency correlated negatively with level of performance on measures of perceptual speed, working memory, episodic memory, and crystallized abilities. Partial set correlation analyses indicated that inconsistency predicted cognitive performance independent of level of performance. The results indicate that variability of performance is an important indicator of cognitive functioning and aging.

Late Pleistocene glacial stratigraphy of the Kumara-Moana region, West Coast of South Island, New Zealand

NASA Astrophysics Data System (ADS)

Barrows, Timothy T.; Almond, Peter; Rose, Robert; Keith Fifield, L.; Mills, Stephanie C.; Tims, Stephen G.

2013-08-01

On the South Island of New Zealand, large piedmont glaciers descended from an ice cap on the Southern Alps onto the coastal plain of the West Coast during the late Pleistocene. The series of moraine belts and outwash plains left by the Taramakau glacier are used as a type section for interpreting the glacial geology and timing of major climatic events of New Zealand and also as a benchmark for comparison with the wider Southern Hemisphere. In this paper we review the chronology of advances by the Taramakau glacier during the last or Otira Glaciation using a combination of exposure dating using the cosmogenic nuclides 10Be and 36Cl, and tephrochronology. We document three distinct glacial maxima, represented by the Loopline, Larrikins and Moana Formations, separated by brief interstadials. We find that the Loopline Formation, originally attributed to Oxygen Isotope Chronozone 4, is much younger than previously thought, with an advance culminating around 24,900 ± 800 yr. The widespread late Pleistocene Kawakawa/Oruanui tephra stratigraphically lies immediately above it. This Formation has the same age previously attributed to the older part of the Larrikins Formation. Dating of the Larrikins Formation demonstrates there is no longer a basis for subdividing it into older and younger phases with an advance lasting about 1000 years between 20,800 ± 500 to 20,000 ± 400 yr. The Moana Formation represents the deposits of the last major advance of ice at 17,300 ± 500 yr and is younger than expected based on limited previous dating. The timing of major piedmont glaciation is restricted to between ˜25,000 and 17,000 yr and this interval corresponds to a time of regionally cold sea surface temperatures, expansion of grasslands at the expense of forest on South Island, and hemisphere wide glaciation.

OLDER ADULTS CATCH UP TO YOUNGER ADULTS ON A LEARNING AND MEMORY TASK THAT INVOLVES COLLABORATIVE SOCIAL INTERACTION

PubMed Central

Derksen, B.J.; Duff, M.C.; Weldon, K.; Zhang, J.; Zamba, G.; Tranel, D.; Denburg, N.L.

2014-01-01

Learning and memory abilities tend to decline as people age. The current study examines the question of whether a learning situation that emphasizes collaborative social interaction might help older persons overcome age-related learning and memory changes and thus perform similarly to younger persons. Younger and Older participants (n = 34 in each group) completed the Barrier Task, a game-like social interaction where partners work together to develop labels for a set of abstract tangrams. Participants were also administered standard clinical neuropsychological measures of memory, on which the Older group showed expected inferiority to the Younger group. On the Barrier Task, the Older group performed less well than the Younger group early on, but as the task progressed, the performance of the Older group caught up and became statistically indistinguishable from that of the Younger group. These results can be taken to suggest that a learning milieu characterized by collaborative social interaction can attenuate some of the typical memory disadvantages associated with being older. PMID:24841619

Older adults catch up to younger adults on a learning and memory task that involves collaborative social interaction.

PubMed

Derksen, B J; Duff, M C; Weldon, K; Zhang, J; Zamba, K D; Tranel, D; Denburg, N L

2015-01-01

Learning and memory abilities tend to decline as people age. The current study examines the question of whether a learning situation that emphasises collaborative social interaction might help older persons overcome age-related learning and memory changes and thus perform similarly to younger persons. Younger and Older participants (n = 34 in each group) completed the Barrier Task (BT), a game-like social interaction where partners work together to develop labels for a set of abstract tangrams. Participants were also administered standard clinical neuropsychological measures of memory, on which the Older group showed expected inferiority to the Younger group. On the BT, the Older group performed less well than the Younger group early on, but as the task progressed, the performance of the Older group caught up and became statistically indistinguishable from that of the Younger group. These results can be taken to suggest that a learning milieu characterised by collaborative social interaction can attenuate some of the typical memory disadvantages associated with being older.

Evaluating authentication options for mobile health applications in younger and older adults

PubMed Central

Khan, Hassan; Hengartner, Urs; Ong, Stephanie; Logan, Alexander G.; Vogel, Daniel; Gebotys, Robert; Yang, Jilan

2018-01-01

Objective Apps promoting patient self-management may improve health outcomes. However, methods to secure stored information on mobile devices may adversely affect usability. We tested the reliability and usability of common user authentication techniques in younger and older adults. Methodology Usability testing was conducted in two age groups, 18 to 30 years and 50 years and older. After completing a demographic questionnaire, each participant tested four authentication options in random order: four-digit personal identification number (PIN), graphical password (GRAPHICAL), Android pattern-lock (PATTERN), and a swipe-style Android fingerprint scanner (FINGERPRINT). Participants rated each option using the Systems Usability Scale (SUS). Results A total of 59 older and 43 younger participants completed the study. Overall, PATTERN was the fastest option (3.44s), and PIN had the fewest errors per attempt (0.02). Participants were able to login using PIN, PATTERN, and GRAPHICAL at least 98% of the time. FINGERPRINT was the slowest (26.97s), had an average of 1.46 errors per attempt, and had a successful login rate of 85%. Overall, PIN and PATTERN had higher SUS scores than FINGERPRINT and GRAPHICAL. Compared to younger participants, older participants were also less likely to find PATTERN to be tiring, annoying or time consuming and less likely to consider PIN to be time consuming. Younger participants were more likely to rate GRAPHICAL as annoying, time consuming and tiring than older participants. Conclusions On mobile devices, PIN and pattern-lock outperformed graphical passwords and swipe-style fingerprints. All participants took longer to authenticate using the swipe-style fingerprint compared to other options. Older participants also took two to three seconds longer to authenticate using the PIN, pattern and graphical passwords though this did not appear to affect perceived usability. PMID:29300736

Evaluating authentication options for mobile health applications in younger and older adults.

PubMed

Grindrod, Kelly; Khan, Hassan; Hengartner, Urs; Ong, Stephanie; Logan, Alexander G; Vogel, Daniel; Gebotys, Robert; Yang, Jilan

2018-01-01

Apps promoting patient self-management may improve health outcomes. However, methods to secure stored information on mobile devices may adversely affect usability. We tested the reliability and usability of common user authentication techniques in younger and older adults. Usability testing was conducted in two age groups, 18 to 30 years and 50 years and older. After completing a demographic questionnaire, each participant tested four authentication options in random order: four-digit personal identification number (PIN), graphical password (GRAPHICAL), Android pattern-lock (PATTERN), and a swipe-style Android fingerprint scanner (FINGERPRINT). Participants rated each option using the Systems Usability Scale (SUS). A total of 59 older and 43 younger participants completed the study. Overall, PATTERN was the fastest option (3.44s), and PIN had the fewest errors per attempt (0.02). Participants were able to login using PIN, PATTERN, and GRAPHICAL at least 98% of the time. FINGERPRINT was the slowest (26.97s), had an average of 1.46 errors per attempt, and had a successful login rate of 85%. Overall, PIN and PATTERN had higher SUS scores than FINGERPRINT and GRAPHICAL. Compared to younger participants, older participants were also less likely to find PATTERN to be tiring, annoying or time consuming and less likely to consider PIN to be time consuming. Younger participants were more likely to rate GRAPHICAL as annoying, time consuming and tiring than older participants. On mobile devices, PIN and pattern-lock outperformed graphical passwords and swipe-style fingerprints. All participants took longer to authenticate using the swipe-style fingerprint compared to other options. Older participants also took two to three seconds longer to authenticate using the PIN, pattern and graphical passwords though this did not appear to affect perceived usability.

Return to Sport in the Younger Patient With Anterior Cruciate Ligament Reconstruction

PubMed Central

Webster, Kate E.; Feller, Julian A.; Whitehead, Timothy S.; Myer, Gregory D.; Merory, Peter B.

2017-01-01

Background: Although anterior cruciate ligament (ACL) reconstruction is generally regarded as a successful procedure, only 65% of patients return to their preinjury sport. While return-to-sport rates are likely higher in younger patients, there is a paucity of data that focus on the younger patient and their return-to-sport experience after ACL reconstruction. Purpose: To investigate a range of return-to-sport outcomes in younger athletes who had undergone ACL reconstruction surgery. Study Design: Case series; Level of evidence, 4. Methods: A group of 140 young patients (<20 years old at surgery) who had 1 ACL reconstruction and no subsequent ACL injuries completed a survey regarding details of their sport participation at a mean follow-up of 5 years (range, 3-7 years). Results: Overall, 76% (95% CI, 69%-83%) of the young patient group returned to the same preinjury sport. Return rates were higher for males than females (81% vs 71%, respectively; P > .05). Of those who returned to their sport, 65% reported that they could perform as well as before the ACL injury and 66% were still currently participating in their respective sport. Young athletes who never returned to sport cited fear of a new injury (37%) or study/work commitments (30%) as the primary reasons for dropout. For those who had successfully returned to their preinjury sport but subsequently stopped participating, the most common reason cited for stopping was study/work commitments (53%). At a mean 5-year follow-up, 48% of female patients were still participating in level I (jumping, hard pivoting) sports, as were 54% of males. Conclusion: A high percentage of younger patients return to their preinjury sport after ACL reconstruction surgery. For patients in this cohort who had not sustained a second ACL injury, the majority continue to participate and are satisfied with their performance. PMID:28473996

Medication adherence and rejection rates in older versus younger adult liver transplant recipients

PubMed Central

Leven, Emily A.; Annunziato, Rachel; Helcer, Jacqueline; Lieber, Sarah R.; Knight, Christopher S.; Wlodarkiewicz, Catherine; Soriano, Rainier P.; Florman, Sander S.; Schiano, Thomas D.; Shemesh, Eyal

2017-01-01

A growing number of older adults are undergoing liver transplantation (LT) in the US. In some settings, it is thought that adherence declines with age. This retrospective study examined adherence and clinical outcomes in older versus younger adult LT recipients. Medical records of adult LT recipients from 2009–2012 from a single urban center were reviewed. The medication level variability index (MLVI) was the pre-defined primary outcome, with nonadherence defined as MLVI >2.5. The secondary outcome was incidence of rejection. Outcomes were evaluated starting one year post-LT until 2015. 42/248 patients were ≥65 at transplant. Older adults had significantly better adherence than younger ones (65% ≥65 were adherent vs. 42% younger adults; Chi-Square two-tailed p=0.02). Survival analyses of rejection between age groups censored by time since transplant showed no difference among the four age groups (χ2 = 0.84, p=0.84). Older age was not found to be a risk factor for reduced adherence or graft rejection in patients surviving at least one year post-LT. PMID:28370346

[Health promotion in families with paramyloidosis: the role of elders with younger family members].

PubMed

Oliveira, Carla Roma; Mendes, Álvaro; Sousa, Liliana

2017-06-12

Citizens are now partners in the formal health promotion system. In the management of hereditary diseases, the role of family members is a vital source of support. Elders play a crucial role due to their long relationship with the disease and with patients in the family. However, this role has still been insufficiently explored, particularly in genetic disorders like paramyloidosis. This exploratory qualitative study analyzes the role of elders in families with paramyloidosis, in health promotion for younger members. The critical incidents technique was applied using a semi-structured interview. The study involved 18 participants who reported 76 critical incidents. The interviews were taped and submitted to content analysis. The principal results suggest the following roles for elders with younger family members: act as role models (in behaviors), encourage, inform, and support. The older generations can be mobilized by health professionals as partners to support younger generations in families with paramyloidosis.

[Drowning mortality trends in children younger than 5 years old in Mexico, 1979-2008].

PubMed

Báez-Báez, Guadalupe Laura; Orozco-Valerio, María de Jesús; Dávalos-Guzmán, Julio César; Méndez-Magaña, Ana Cecilia; Celis, Alfredo

2012-01-01

To describe mortality trends from drowning in children younger than 5 years old. Mortality records of children younger than 5 years old were obtained from the National Health Information (SINAIS) system of Mexico from 1979 to 2008. Cause of death by asphyxia was established according to the International Classification of Diseases (ICD 9th and 10th). We analyzed age, sex, federal state, year and place where the event occurred. Fatal drowning diminished from 7.64 in 1979 to 3.59 deaths per 100,000 in 2008. This trend was observed throughout the assessment period and in all federal states. Children younger than 2 years showed the highest rate of death. Mortality was higher in males than females (1.7:1). A great proportion of events happen at home. Drowning mortality among children less than 5 years old in Mexico shows a downward trend in all states.

Do Correlates of Pain-Related Stoicism and Cautiousness Differ in Younger and Older People With Advanced Cancer?

PubMed

Mah, Kenneth; Tran, Kim T; Gauthier, Lynn R; Rodin, Gary; Zimmermann, Camilla; Warr, David; Librach, S Lawrence; Moore, Malcolm; Shepherd, Frances A; Gagliese, Lucia

2018-03-01

Age differences are not evident in pain-related stoicism and cautiousness in people with cancer pain. Little is known about the factors associated with these pain-related attitudes or age-related patterns in these associations. The present cross-sectional study investigated the biopsychosocial correlates of the attitudes in younger and older patients with advanced cancer. Pain-related stoicism (fortitude, concealment, superiority) and cautiousness (self-doubt, reluctance) were assessed using the Pain Attitudes Questionnaire-Revised (PAQ-R). Participants, 155 younger (younger than 60 years old) and 114 older (60 years old or older) patients with advanced cancer completed the PAQ-R and measures of sociodemographic and medical characteristics, pain intensity, cognitive-affective pain-related responses, physical functioning, psychological distress and well-being, and psychosocial functioning. Backwards regression analyses identified correlates for each PAQ-R factor separately for younger and older patients. Activity engagement was a frequent correlate, but its relationship with concealment was the only association common to both age groups. Younger and older patients exhibited different avoidance-related constructs suggesting relational challenges in the former group (avoidant attachment) and intrapersonal fear in the latter (cognitive avoidance). Medical correlates also showed age differences: younger patients showed symptom-focused correlates, whereas older patients showed aging-related correlates. Findings support a biopsychosocial framework of cancer-pain adaptation incorporating a lifespan-developmental perspective. To our knowledge, this article is the first to identify biopsychosocial correlates of stoic and cautious attitudes toward cancer pain in younger and older patients with advanced cancer. Findings highlight possible age-related motivations for greater pain-related stoicism or cautiousness and can potentially inform interventions addressing challenges in

Screening for Dyslipidemia in Younger Adults: A Systematic Review for the U.S. Preventive Services Task Force.

PubMed

Chou, Roger; Dana, Tracy; Blazina, Ian; Daeges, Monica; Bougatsos, Christina; Jeanne, Thomas L

2016-10-18

Dyslipidemia may occur in younger adults (defined as persons aged 21 to 39 years) and is an important risk factor for cardiovascular disease. Screening might identify younger adults with asymptomatic dyslipidemia who may benefit from lipid-lowering therapies. To update the 2008 U.S. Preventive Services Task Force review on dyslipidemia screening in younger adults. The Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and MEDLINE through May 2016, and reference lists. Randomized, controlled trials; cohort studies; and case-control studies on screening for or treatment of asymptomatic dyslipidemia in adults aged 21 to 39 years. The plan was for 1 investigator to abstract data and a second to check their accuracy, and for 2 investigators to independently assess study quality; however, no studies met the inclusion criteria. No study evaluated the effects of lipid screening versus no screening, treatment versus no treatment, or delayed versus earlier treatment on clinical outcomes in younger adults. In addition, no study evaluated the diagnostic yield of alternative screening strategies (such as targeted screening of persons with a family history of hyperlipidemia vs. general screening) in younger adults. No direct relevant evidence. Direct evidence on the benefits and harms of screening for or treatment of dyslipidemia in younger adults remains unavailable. Estimating the potential effects of screening for dyslipidemia in this population requires extrapolation from studies performed in older adults. Agency for Healthcare Research and Quality.

After total knee replacement younger patients demonstrate superior balance control compared to older patients when recovering from a forward fall.

PubMed

Street, Brian D; Gage, William

2017-05-01

National joint replacement registries have reported a substantial growth in younger knee osteoarthritic patients (<55years old) undergoing total knee replacement, however this younger population is generally understudied. Importantly, studies examining experimentally controlled perturbation have shown age-related differences between younger and older healthy adults, whether similar age-related differences exist among total knee replacement patients is unknown. A total of 59 participants, including 29 unilateral total knee replacement patients (six-months post-surgery) made up the four experimental groups: 1) younger patient (54.3 (SD 7.9) years), 2) younger control (55.2 (SD 4.0) years), 3) older patient (76.9 (SD 4.7) years), and 4) older control (77.7 (SD 4.1) years). Using a tether-release method to perturb balance and simulate a forward fall, center of mass and stepping characteristics were analyzed. Younger patients recovered following the perturbation with a significantly smaller center of mass displacement compared to the older patients (14.85 (SD 0.01) v. 18.13 (SD 0.02) %ht, p=0.02); utilizing a longer (0.43 (SD 0.02) v. 0.39 (SD 0.03) m, p<0.001) and higher velocity (2.01 (SD 0.2) v. 1.59 (SD 0.2) m/s, p=0.001) recovery step. Importantly, younger patients did not differ significantly from the younger controls in center of mass displacement or recovery step characteristics (p>0.05). The younger patients demonstrated superior center of mass control in response to a forward perturbation, suggesting that younger patients would be at a reduced risk of falling when recovering from a forward-directed postural perturbation compared to older patients. Copyright © 2017 Elsevier Ltd. All rights reserved.

Reduced impact of alcohol use on next-day tiredness in older relative to younger adults: A role for sleep duration.

PubMed

Lydon-Staley, David M; Ram, Nilam; Brose, Annette; Schmiedek, Florian

2017-11-01

Recent work has suggested that older adults may be less susceptible to the next-day effects of alcohol relative to younger adults. The effects of alcohol in younger adults may be mediated by sleep duration, but due to age differences in the contexts of alcohol use, this mediation process may not generalize to older adults. The present study examined age-group (younger vs. older adults) differences in how alcohol use influenced next-day tiredness during daily life. Reports of alcohol use, sleep duration, and next-day tiredness obtained on ∼101 days from 91 younger adults (ages 20-31 years) and 75 older adults (ages 65-80 years) were modeled using a multilevel, moderated mediation framework. Findings indicated that (a) greater-than-usual alcohol use was associated with greater-than-usual tiredness in younger adults only, (b) greater-than-usual alcohol use was associated with shorter-than-usual sleep duration in younger adults only, and (c) shorter-than-usual sleep duration was associated with greater tiredness in both younger and older adults. For the prototypical younger adult, a significant portion (43%) of the association between alcohol use and next-day tiredness could be explained assuming mediation through sleep duration, whereas there was no evidence of mediation for the prototypical older adult. Findings of age differences in the mediation process underlying associations among alcohol use, sleep, and tiredness provide insight into the mechanisms driving recent observations of reduced next-day effects of alcohol in older relative to younger adults. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Binaural Advantage for Younger and Older Adults with Normal Hearing

ERIC Educational Resources Information Center

Dubno, Judy R.; Ahlstrom, Jayne B.; Horwitz, Amy R.

2008-01-01

Purpose: Three experiments measured benefit of spatial separation, benefit of binaural listening, and masking-level differences (MLDs) to assess age-related differences in binaural advantage. Method: Participants were younger and older adults with normal hearing through 4.0 kHz. Experiment 1 compared spatial benefit with and without head shadow.…

Expectations of younger patients concerning activities after knee arthroplasty: are we asking the right questions?

PubMed

Witjes, Suzanne; van Geenen, Rutger C I; Koenraadt, Koen L M; van der Hart, Cor P; Blankevoort, Leendert; Kerkhoffs, Gino M M J; Kuijer, P Paul F M

2017-02-01

Indications for total and unicondylar knee arthroplasty (KA) have expanded to younger patients, in which Patient-Reported Outcome Measures (PROMs) often show ceiling effects. This might be due to higher expectations. Our aims were to explore expectations of younger patients concerning activities in daily life, work and leisure time after KA and to assess to what extent PROMs meet and evaluate these activities of importance. Focus groups were performed among osteoarthritis (OA) patients <65 years awaiting KA, in which they indicated what activities they expected to perform better in daily life, work and leisure time after KA. Additionally, 28 activities of daily life, 17 of work and 27 of leisure time were depicted from seven PROMS, which were rated on importance, frequency and bother. A total score, representing motivation for surgery, was also calculated. Data saturation was reached after six focus groups including 37 patients. Younger OA patients expect to perform better on 16 activities after KA, including high-impact leisure time activities. From the PROMs, daily life and work activities were rated high in both importance and motivation for surgery, but for leisure time activities importance varied highly between patients. All seven PROMs score activities of importance, but no single PROM incorporates all activities rated important. Younger patients expect to perform better on many activities of daily life, work and leisure time after KA, and often at demanding levels. To measure outcomes of younger patients, we suggest using PROMs that include work and leisure time activities besides daily life activities, in which preferably scored activities can be individualized.

The effects of value on context-item associative memory in younger and older adults.

PubMed

Hennessee, Joseph P; Knowlton, Barbara J; Castel, Alan D

2018-02-01

Valuable items are often remembered better than items that are less valuable by both older and younger adults, but older adults typically show deficits in binding. Here, we examine whether value affects the quality of recognition memory and the binding of incidental details to valuable items. In Experiment 1, participants learned English words each associated with a point-value they earned for correct recognition with the goal of maximizing their score. In Experiment 2, value was manipulated by presenting items that were either congruent or incongruent with an imagined state of physiological need (e.g., hunger). In Experiment 1, point-value was associated with enhanced recollection in both age groups. Memory for the color associated with the word was in fact reduced for high-value recollected items compared with low-value recollected items, suggesting value selectively enhances binding of task-relevant details. In Experiment 2, memory for learned images was enhanced by value in both age groups. However, value differentially enhanced binding of an imagined context to the item in younger and older adults, with a strong trend for increased binding in younger adults only. These findings suggest that value enhances episodic encoding in both older and younger adults but that binding of associated details may be reduced for valuable items compared to less valuable items, particularly in older adults. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Timing of Pleistocene glaciations in the High Atlas, Morocco: New 10Be and 36Cl exposure ages

NASA Astrophysics Data System (ADS)

Hughes, Philip D.; Fink, David; Rodés, Ángel; Fenton, Cassandra R.; Fujioka, Toshiyuki

2018-01-01

This paper presents data from 42 new samples yielding Late Pleistocene cosmogenic 10Be and 36Cl exposure ages of moraine boulders across a series of glaciated valleys in the Toubkal Massif (4167 m a.s.l.), High Atlas, Morocco. This represents the first comprehensive Pleistocene glacial chronology in North Africa and one of the largest datasets from the Mediterranean region. The timing of these glacier advances has major implications for understanding the influence of Atlantic depressions on moisture supply to North Africa and the Mediterranean basin during the Pleistocene. The oldest and lowest moraines which span elevations from ∼1900 to 2400 m a.s.l. indicate that the maximum glacier advance occurred from MIS 5 to 3 with a combined mean 10Be and 36Cl age of 50.2 ± 19.5 ka (1 SD; n = 12, 7 outliers). The next moraine units up-valley at higher elevations (∼2200-2600 m a.s.l.) yielded exposure ages close to the global Last Glacial Maximum (LGM) with a combined mean 10Be and 36Cl age of 22.0 ± 4.9 ka (1 SD; n = 9, 7 outliers). The youngest exposure ages are from moraines that were emplaced during the Younger Dryas with a combined mean 10Be and 36Cl age of 12.3 ± 0.9 ka (1 SD; n = 7, no outliers) and are found in cirques at the highest elevations ranging from ∼2900 to 3300 m a.s.l. From moraines predating the Younger Dryas, a large number of young outliers are spread evenly between 6 and 13 ka suggesting a continuing process of exhumation or repositioning of boulders during the early to mid-Holocene. This attests to active seismic processes and possibly intense erosion during this period.

Deglacial Neodymium Isotopic Ratios in the Florida Straits and the Response of Intermediate Waters to Reduced Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

Marcantonio, F.; Schmidt, M. W.; Franklin, A.; Lynch-Stieglitz, J. M.

2009-12-01

Neodymium behaves quasi-conservatively in seawater, and its isotopic signature can be used as a tracer for oceanic water masses. By analyzing Nd in the authigenic ferromanganese oxide component of marine sediments, past changes in water mass movements have been hypothesized. In the Atlantic Ocean, Nd isotope analysis has been used to trace the variable strength of the meridional overturning circulation (MOC) during the last deglaciation (e.g., Pahnke et al., 2008). Here, we use Nd isotopes to investigate whether a decrease in the strength of the past MOC manifests itself as a reduction (Came et al., 2008) or an increase (Pahnke et al., 2008) in the northward incursion of Antarctic Intermediate Water (AAIW) into the North Atlantic. Sediments from two core sites currently bathed by AAIW within the Florida Straits (546 m and 751 m water depth) are well suited for profiling authigenic Nd isotope ratios. Because the Florida Current represents a major pathway of the Atlantic MOC surface return flow, the Florida Strait sites can shed light on how variations in AAIW are related to changes in Atlantic MOC strength. The sediments range in age from 0 to 25 kyr, and the high sedimentation rates (8 - 200 cm/kyr) ensure that millennial climate events during the deglaciation are captured. The range in ɛNd measured in the shallower core thus far is low (~ 1.5 epsilon units), but significant. There is a trend in the data which suggests more unradiogenic values during the Younger Dryas event when Atlantic MOC slowed down. Such a trend supports the idea based on benthic foraminiferal Cd/Ca data (Came et al., 2008) that, during the Younger Dryas, there was a reduction within the Florida Current of the flow of intermediate, southern-sourced waters. Came et al., 2008, Paleoceanography 23, PA1217. Pahnke et al., 2008, Nature Geoscience 1, 870-874.

Post-glacial flooding of the Bering Land Bridge dated to 11 cal ka BP based on new geophysical and sediment records

USGS Publications Warehouse

Jakobsson, Martin; Pearce, Christof; Cronin, Thomas M.; Backman, Jan; Anderson, Leif G.; Barrientos, Natalia; Bjork, Goran; Coxhall, Helen; de Boer, Agatha; Mayer, Larry; Morth, Carl-Magnus; Nilsson, Johan; Rattray, Jayne; Sranne, Christian; Semiletov, Igor; O'Regan, Matt

2017-01-01

The Bering Strait connects the Arctic and Pacific oceans and separates the North American and Asian landmasses. The presently shallow ( ∼  53 m) strait was exposed during the sea level lowstand of the last glacial period, which permitted human migration across a land bridge today referred to as the Bering Land Bridge. Proxy studies (stable isotope composition of foraminifera, whale migration into the Arctic Ocean, mollusc and insect fossils and paleobotanical data) have suggested a range of ages for the Bering Strait reopening, mainly falling within the Younger Dryas stadial (12.9–11.7 cal ka BP). Here we provide new information on the deglacial and post-glacial evolution of the Arctic–Pacific connection through the Bering Strait based on analyses of geological and geophysical data from Herald Canyon, located north of the Bering Strait on the Chukchi Sea shelf region in the western Arctic Ocean. Our results suggest an initial opening at about 11 cal ka BP in the earliest Holocene, which is later than in several previous studies. Our key evidence is based on a well-dated core from Herald Canyon, in which a shift from a near-shore environment to a Pacific-influenced open marine setting at around 11 cal ka BP is observed. The shift corresponds to meltwater pulse 1b (MWP1b) and is interpreted to signify relatively rapid breaching of the Bering Strait and the submergence of the large Bering Land Bridge. Although the precise rates of sea level rise cannot be quantified, our new results suggest that the late deglacial sea level rise was rapid and occurred after the end of the Younger Dryas stadial.

Extent, timing, and climatic significance of latest Pleistocene and Holocene glaciation in the Sierra Nevada, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, Douglas Howe

Despite more than a century of study, scant attention has been paid to the glacial record in the northern end of the Sierra Nevada, and to the smaller moraines deposited after the retreat of the Tioga (last glacial maximum) glaciers. Equilibrium-line altitude (ELA) estimates of the ice fields indicate that the Tioga ELA gradients there are consistent with similar estimates for the southern half of the range, and with an intensification of the modern temperature/precipitation pattern in the region. The Recess Peak advance has traditionally been considered to be mid-Neoglacial age, about 2--3,000 yr B.P., on the basis of relativemore » weathering estimates. Sediment cores of lakes dammed behind moraines correlative with Recess Peak in four widely spaced sites yields a series of high-resolution AMS radiocarbon dates which demonstrate that Recess Peak glaciers retreated before ~13,100 cal yr B.P.. This minimum limiting age indicates that the advance predates the North Atlantic Younger Dryas cooling. It also implies that there have been no advances larger than the Matthes in the roughly 12,000 year interval between it and the Recess Peak advance. This finding casts doubt on several recent studies that claim Younger Dryas glacier advances in western North America. The 13,100 cal yr B.P. date is also a minimum age for deglaciation of the sample sites used to calibrate the in situ production rates of cosmogenic 10Be and 26Al. The discrepancy between this age and the 11,000 cal yr B.P. exposure age assumed in the original calibration introduces a large (> 19%) potential error in late-Pleistocene exposure ages calculated using these production rates.« less

Deglacial climatic oscillations in the Gulf of California

NASA Astrophysics Data System (ADS)

Keigwin, L. D.; Jones, G. A.

1990-12-01

A high-resolution, accelerator radiocarbon dated climate record of the interval 8,000-18,000 years B.P. from Deep Sea Drilling Project site 480 (Guaymas Basin, Gulf of California) shows geochemical and lithological oscillations of oceanographic and climatic significance during deglaciation. Nonlaminated sediments are associated with cooler climatic conditions during the late glacial (up to 13,000 years B.P.), and from 10,300 to 10,800 years B.P., equivalent to the Younger Dryas event of the North Atlantic region. We propose that the changes from laminated (varved) to nonlaminated sediments resulted from increased oxygen content in Pacific intermediate waters during the glacial and the Younger Dryas episodes, and that the forcing for the latter event was global in scope. Prominent events of low δ18O are recorded in benthic foraminifera from 8,000 to 10,000 and at 12,000 years B.P.; evidence for an earlier event between 13,500 and 15,000 years B.P. is weaker. Maximum δ18O is found to have occurred 10,500, 13,500, and 15,000 years ago (and beyond). Oxygen isotopic variability most likely reflects changing temperature and salinity characteristics of Pacific waters of intermediate depth during deglaciation or environmental changes within the Gulf of California region. Several lines of evidence suggest that during deglaciation the climate of the American southwest was marked by increased precipitation that could have lowered salinity in the Gulf of California. Recent modelling studies show that cooling of the Gulf of Mexico due to glacial meltwater injection, which is believed to have occurred at least twice during deglaciation, would have resulted in increased precipitation with respect to evaporation in the American southwest during summertime. The timing of deglacial events in the Gulf of Mexico and the Gulf of California supports such an atmospheric teleconnection.

Pollen-based evidence of extreme drought during the last Glacial (32.6-9.0 ka) in coastal southern California

NASA Astrophysics Data System (ADS)

Heusser, Linda E.; Kirby, Matthew E.; Nichols, Jonathan E.

2015-10-01

High resolution pollen analyses of sediment core LEDC10-1 from Lake Elsinore yield the first well-dated, terrestrial record of sub-centennial-scale ecologic change in coastal southern California between ˜32 and 9 ka. In the Lake Elsinore watershed, the initial, mesic montane conifer forests dominated by Pinus, and Cupressaceae with trace amounts of Abies and Picea were replaced by a sequence of multiple, extended severe mega-droughts between ˜27.5 and ˜25.5 ka, in which halophytic and xerophytic herbs and shrubs occupied an ephemeral lake. This prolonged and extended dry interval, which corresponds with warm waters offshore, imply strengthening of the North Pacific High and persistent below-average winter precipitation. The subsequent, contrasting monotonic occurrence of montane conifers reflects little variation in cold, mesic climate until ˜15 ka. Postglacial development of Quercus woodland and chaparral mark the return to more xeric, warmer conditions at this time. A brief reversal at ˜13.1-˜12.1 ka, as reflected by an expansion of Pinus, is correlative with the Younger Dryas and interrupts development of warm, postglacial climate. Subsequent gradual expansion of xeric vegetation post - Younger Dryas denotes the establishment of a winter hydroclimate regime in coastal southern California that is more similar to modern conditions. Pollen-based reconstructions of temperature and precipitation at Lake Elsinore are generally correlative with pollen-based paleoclimatic reconstructions and foraminifera-based sea surface temperatures from Santa Barbara Basin in marine core ODP 893. The conspicuous absence of the ˜27.5-˜25.5 ka glacial "mega-drought" in the Santa Barbara Basin pollen record highlights the sensitivity of Lake Elsinore to hydroclimate change, and thus, the importance of this new record that indicates that mega-drought can occur during the full glacial when climatic boundary conditions and forcings differed substantially from the present.

Atomoxetine Treatment for ADHD: Younger Adults Compared with Older Adults

ERIC Educational Resources Information Center

Durell, Todd; Adler, Lenard; Wilens, Timothy; Paczkowski, Martin; Schuh, Kory

2010-01-01

Objective: Atomoxetine is a nonstimulant medication for treating child, adolescent, and adult ADHD. This meta-analysis compared the effects in younger and older adults. Method: A post hoc analysis was conducted using data from two double-blind, placebo-controlled clinical trials. Data from patients aged 18-25 years were compared with data from…

Regional chronostratigraphic and depositional hydrocarbon trends in offshore Louisiana State waters

DOE Office of Scientific and Technical Information (OSTI.GOV)

John, C.J.; Jones, B.J.; Harder, B.J.

1996-09-01

Successful exploration for hydrocarbons in the Northern Gulf of Mexico basin requires a systematic understanding of hydrocarbon producing trends, sand body geometries and the geologic, engineering and reservoir parameters of the producing sands. This study forms part of the Offshore Atlas project in progress at the University of Texas at Austin, Bureau of Economic Geology, Texas, in co-operation with the U.S. Department of Interior, Minerals Management Service, and the Geological Survey of Alabama, and is aimed at achieving this goal. In this study, 26 chronozones were grouped into 12 sub-groups. The chronozones were defined on the basis of the benthicmore » foraminiferal biostratigraphic zones and were correlated across the Gulf using well log and seismic data and were projected from the Federal offshore into the State waters. The chronozones on each well log in the 22 cross sections constructed from West Cameron area eastward to the Chandeleur, Breton Sound and Main Pass areas, were subdivided as applicable into four depositional groups consisting of aggradational, progradational, transgressive and submarine fan facies based primarily on SP log shapes. In the Louisiana State waters there are 86 fields containing 679 reservoirs. This includes 212 oil, 344 gas, 33 condensate and 90 combination type reservoirs. Total combined cumulative production (1975-1995) is 454,335,217 barrels of oil, 114,327,696 barrels of condensate and 5,436,623,888 thousand cubic feet of gas. Total assigned production shows the progradational facies to be most productive yielding 51.69% oil 93.84% condensate, and 77.47% gas. The aggradational facies sands produced 46.96% oil, 1.70% condensate and 17.78%. gas. The submarine fan facies yielded 1.21% oil, 4.45% condensate, and 6.74% gas. Production from the transgressive facies sands was less than 0.2% of the total assigned production of oil, gas and condensate.« less

Neurocognitive and Behavioral Outcomes of Younger Siblings of Children with Autism Spectrum Disorder at Age Five

ERIC Educational Resources Information Center

Warren, Zachary E.; Foss-Feig, Jennifer H.; Malesa, Elizabeth E.; Lee, Evon Batey; Taylor, Julie Lounds; Newsom, Cassandra R.; Crittendon, Julie; Stone, Wendy L.

2012-01-01

Later-born siblings of children with Autism Spectrum Disorders (ASD) are at increased risk for ASD as well as qualitatively similar traits not meeting clinical cutoffs for the disorder. This study examined age five neurocognitive and behavioral outcomes of 39 younger siblings of children with ASD (Sibs-ASD) and 22 younger siblings of typically…

Memory Dynamics and Decision Making in Younger and Older Adults

ERIC Educational Resources Information Center

Lechuga, M. Teresa; Gomez-Ariza, Carlos J.; Iglesias-Parro, Sergio; Pelegrina, Santiago

2012-01-01

The main aim of this research was to study whether memory dynamics influence older people's choices to the same extent as younger's ones. To do so, we adapted the retrieval-practice paradigm to produce variations in memory accessibility of information on which decisions were made later. Based on previous results, we expected to observe…

Screening for Autism in Older and Younger Toddlers with the Modified Checklist for Autism in Toddlers

ERIC Educational Resources Information Center

Pandey, Juhi; Verbalis, Alyssa; Robins, Diana L.; Boorstein, Hilary; Klin, Ami; Babitz, Tammy; Chawarska, Katarzyna; Volkmar, Fred; Green, James; Barton, Marianne; Fein, Deborah

2008-01-01

The Modified Checklist for Autism in Toddlers (M-CHAT) was used to screen younger (16-23 months) versus older (24-30 months) high- and low-risk toddlers. Refusal rates for follow-up interview showed no group differences, but parents of younger/low-risk children were more likely to refuse evaluation than parents of high-risk children. PPP for an…

Younger and Sicker: Comparing Micronesians to Other Ethnicities in Hawaii.

PubMed

Hagiwara, Megan Kiyomi Inada; Miyamura, Jill; Yamada, Seiji; Sentell, Tetine

2016-03-01

We compared the age at admission and the severity of illness of hospitalized Micronesians with 3 other racial/ethnic groups in Hawaii. With Hawaii Health Information Corporation inpatient data, we determined the age at admission and the severity of illness for 162,152 adult, non-pregnancy-related hospital discharges in Hawaii from 2010 to 2012. We performed multivariable linear regression analyses within major disease categories by racial/ethnic group. We created disease categories with all patient refined-diagnosis related groups. Hospitalized Micronesians were significantly younger at admission than were comparison racial/ethnic groups across all patient refined-diagnosis related group categories. The severity of illness for Micronesians was significantly higher than was that of all comparison racial/ethnic groups for cardiac and infectious diseases, higher than was that of Whites and Japanese for cancer and endocrine hospitalizations, and higher than was that of Native Hawaiians for substance abuse hospitalizations. Micronesians were hospitalized significantly younger and often sicker than were comparison populations. Our results will be useful to researchers, state governments, and hospitals, providers, and health systems for this vulnerable group.

Comparison of tinnitus and psychological aspects between the younger and older adult patients with tinnitus.

PubMed

Park, So Young; Han, Jung Ju; Hwang, Jae Hyung; Whang, Eul Sung; Yeo, Sang Won; Park, Shi Nae

2017-04-01

To explore the differences in various tinnitus-related features and psychological aspects between the younger and older adult patients with tinnitus. We retrospectively reviewed the clinical data of the adult patients who visited our tinnitus clinic in 2013 and completed full tinnitus assessment including audiometry, tinnitus matching, standardized tinnitus questionnaires, and psychometric questionnaires. The younger group included patients aged 20-45 years (n=64), and the older group, those older than 65 years (n=76). Clinical features, hearing levels, matched tinnitus pitches and loudness, self-report tinnitus severity scores, Beck depression inventory scores, and stress scores were compared between the groups. Tinnitus duration was longer in the older group (p=0.002). Mean PTAs were 16dB HL in the younger, and 38dB HL in the older groups (p<0.001). Eighty-nine percent of the younger patients had normal hearing, while 82% of the older patients had hearing loss (p<0.001). Matched tinnitus loudness was greater in the older group (64dB HL vs. 36dB HL, p<0.001). All of the self-report tinnitus, depression, and stress scores did not differ between the groups. The older patients seemed to be more receptive to tinnitus. The majority of older tinnitus patients had concomitant hearing loss, and thus hearing rehabilitation should be considered preferentially for tinnitus management in this age group. Subjective tinnitus severity, depressive symptoms, and the stress levels were similar between the younger and older tinnitus patients. Therefore, treatment could be planned based upon the comprehensive understanding of the tinnitus characteristics and psychological aspects in each patient irrespective of age. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Allograft Augmentation of Hamstring Autograft for Younger Patients Undergoing Anterior Cruciate Ligament Reconstruction.

PubMed

Jacobs, Cale A; Burnham, Jeremy M; Makhni, Eric; Malempati, Chaitu S; Swart, Eric; Johnson, Darren L

2017-03-01

Younger patients and those with smaller hamstring autograft diameters have been shown to be at significantly greater risk of graft failure after anterior cruciate ligament (ACL) reconstruction. To date, there is no information in the literature about the clinical success and/or cost-effectiveness of increasing graft diameter by augmenting with semitendinosus allograft tissue for younger patients. Hybrid hamstring grafts are a cost-effective treatment option because of a reduced rate of graft failure. Cohort study (economic and decision analysis); Level of evidence, 3. We retrospectively identified patients younger than 18 years who had undergone ACL reconstruction by a single surgeon between 2010 and 2015. During this period, the operating surgeon's graft selection algorithm included the use of bone-patellar tendon-bone (BTB) autografts for the majority of patients younger than 18 years. However, hamstring autografts (hamstring) or hybrid hamstring autografts with allograft augment (hybrid) were used in skeletally immature patients and in those whom the surgeon felt might have greater difficulty with postoperative rehabilitation after BTB graft harvest. Patient demographics, graft type, graft diameter, the time the patient was cleared to return to activity, and the need for secondary surgical procedures were compared between the hamstring and hybrid groups. The clinical results were then used to assess the potential cost-effectiveness of hybrid grafts in this select group of young patients with an ACL injury or reconstruction. This study comprised 88 patients (hamstring group, n = 46; hybrid group, n = 42). The 2 groups did not differ in terms of age, sex, timing of return to activity, or prevalence of skeletally immature patients. Graft diameters were significantly smaller in the hamstring group (7.8 vs 9.9 mm; P < .001), which corresponded with a significantly greater rate of graft failure (13 of 46 [28.3%] vs 5 of 42 [11.9%]; P = .049). As a result of the

Expression of emotions related to the experience of cancer in younger and older Arab breast cancer survivors.

PubMed

Goldblatt, Hadass; Cohen, Miri; Azaiza, Faisal

2016-12-01

Researchers have suggested that older adults express less negative emotions. Yet, emotional expression patterns in older and younger breast cancer survivors, have barely been examined. This study aimed to explore types and intensity of negative and positive emotional expression related to the breast cancer experience by younger and older Arab breast cancer survivors. Participants were 20 younger (aged 32-50) and 20 older (aged 51-75) Muslim and Christian Arab breast cancer survivors (stages I-III), currently free of disease. Data were gathered through in-depth semi-structured interviews. Mixed methods analyses were conducted, including: (1) frequency analysis of participants' emotional expressions; (2) content analysis of emotional expressions, categorized according to negative and positive emotions. Three emotional expression modalities were revealed: (1) Succinct versus comprehensive accounts; (2) expression of emotions versus avoidance of emotions; (3) patterns of expression of positive emotions and a sense of personal growth. Younger women provided more detailed accounts about their illness experiences than older women. Older women's accounts were succinct, action-focused, and included more emotion-avoiding expressions than younger women. Understanding the relationships between emotional expression, emotional experience, and cancer survivors' quality of life, specifically of those from traditional communities, is necessary for developing effective psycho-social interventions.

Neurophysiological and Behavioral Differences between Older and Younger Adults When Processing Violations of Tonal Structure in Music

PubMed Central

Lagrois, Marie-Élaine; Peretz, Isabelle; Zendel, Benjamin Rich

2018-01-01

Aging is associated with decline in both cognitive and auditory abilities. However, evidence suggests that music perception is relatively spared, despite relying on auditory and cognitive abilities that tend to decline with age. It is therefore likely that older adults engage compensatory mechanisms which should be evident in the underlying functional neurophysiology related to processing music. In other words, the perception of musical structure would be similar or enhanced in older compared to younger adults, while the underlying functional neurophysiology would be different. The present study aimed to compare the electrophysiological brain responses of younger and older adults to melodic incongruities during a passive and active listening task. Older and younger adults had a similar ability to detect an out-of-tune incongruity (i.e., non-chromatic), while the amplitudes of the ERAN and P600 were reduced in older adults compared to younger adults. On the other hand, out-of-key incongruities (i.e., non-diatonic), were better detected by older adults compared to younger adults, while the ERAN and P600 were comparable between the two age groups. This pattern of results indicates that perception of tonal structure is preserved in older adults, despite age-related neurophysiological changes in how melodic violations are processed. PMID:29487498

Neurophysiological and Behavioral Differences between Older and Younger Adults When Processing Violations of Tonal Structure in Music.

PubMed

Lagrois, Marie-Élaine; Peretz, Isabelle; Zendel, Benjamin Rich

2018-01-01

Aging is associated with decline in both cognitive and auditory abilities. However, evidence suggests that music perception is relatively spared, despite relying on auditory and cognitive abilities that tend to decline with age. It is therefore likely that older adults engage compensatory mechanisms which should be evident in the underlying functional neurophysiology related to processing music. In other words, the perception of musical structure would be similar or enhanced in older compared to younger adults, while the underlying functional neurophysiology would be different. The present study aimed to compare the electrophysiological brain responses of younger and older adults to melodic incongruities during a passive and active listening task. Older and younger adults had a similar ability to detect an out-of-tune incongruity (i.e., non-chromatic), while the amplitudes of the ERAN and P600 were reduced in older adults compared to younger adults. On the other hand, out-of-key incongruities (i.e., non-diatonic), were better detected by older adults compared to younger adults, while the ERAN and P600 were comparable between the two age groups. This pattern of results indicates that perception of tonal structure is preserved in older adults, despite age-related neurophysiological changes in how melodic violations are processed.

Strategies adopted by younger and older adults while operating a non-pedal tricycle.

PubMed

Calve, Tatiane; Russo Júnior, Douglas Vicente; Barela, Ana Maria Forti

Exercises that could prevent gait impairment of older adults should be implemented in such a way that practitioners can keep motivation and adherence independent of older adults fitness levels. This study describes how younger and older adults use a non-pedal tricycle to transport their bodies along a pathway. Nine younger (24±4.9y) and nine older (66±4.0y) adults participated in this study. They moved along a straight pathway at a self-selected comfortable speed with reflective markers on their main lower limb landmarks. A computerized gait analysis system with infrared cameras was used to obtain kinematic data to calculate spatial-temporal parameters and lower limb angles. Overall, participants from both groups were able to perform the task moving at a similar mean speed, with similar stride length and ankle joint excursion. Older adults had higher cadence (mean difference of 17steps/min; 95% CI=0.99-1.15) and hip excursion (mean difference of 12°; 95% CI=28-33), longer stance duration (mean difference of 3.4%; 95% CI=56.2-59.5), and lower knee excursion (mean difference of 6°; 95% CI=47.9-53.8) than younger adults. Older adults were able to transport their body with a non-pedal tricycle with more hip and less knee excursion than younger adults. Professionals that work with the older population should look at and take into consideration the use of non-pedal tricycles in exercise protocols and investigate the long-term impacts. Copyright © 2017 Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia. Publicado por Elsevier Editora Ltda. All rights reserved.

Digital Clock Drawing: differentiating "thinking" versus "doing" in younger and older adults with depression.

PubMed

Cohen, Jamie; Penney, Dana L; Davis, Randall; Libon, David J; Swenson, Rodney A; Ajilore, Olusola; Kumar, Anand; Lamar, Melissa

2014-10-01

Psychomotor slowing has been documented in depression. The digital Clock Drawing Test (dCDT) provides: (i) a novel technique to assess both cognitive and motor aspects of psychomotor speed within the same task and (ii) the potential to uncover subtleties of behavior not previously detected with non-digitized modes of data collection. Using digitized pen technology in 106 participants grouped by Age (younger/older) and Affect (euthymic/unmedicated depressed), we recorded cognitive and motor output by capturing how the clock is drawn rather than focusing on the final product. We divided time to completion (TTC) for Command and Copy conditions of the dCDT into metrics of percent of drawing (%Ink) versus non-drawing (%Think) time. We also obtained composite Z-scores of cognition, including attention/information processing (AIP), to explore associations of %Ink and %Think times to cognitive and motor performance. Despite equivalent TTC, %Ink and %Think Command times (Copy n.s.) were significant (AgeXAffect interaction: p=.03)-younger depressed spent a smaller proportion of time drawing relative to thinking compared to the older depressed group. Command %Think time negatively correlated with AIP in the older depressed group (r=-.46; p=.02). Copy %Think time negatively correlated with AIP in the younger depressed (r=-.47; p=.03) and older euthymic groups (r=-.51; p=.01). The dCDT differentiated aspects of psychomotor slowing in depression regardless of age, while dCDT/cognitive associates for younger adults with depression mimicked patterns of older euthymics.

An exploration of the patient navigator role: perspectives of younger women with breast cancer.

PubMed

Pedersen, Allison E; Hack, Thomas F; McClement, Susan E; Taylor-Brown, Jill

2014-01-01

To delineate the role of the oncology patient navigator, drawing from the experiences and descriptions of younger women with breast cancer. Interpretive, descriptive, qualitative research design. Participants' homes, researcher's home, and via telephone, all in Winnipeg, Manitoba, Canada. 12 women aged 50 years or younger who were diagnosed with breast cancer within the last three years. Face-to-face semistructured interviews explored patient experiences with the cancer care system, including problems encountered, unmet needs, and opinions about the functions of the patient navigator role. The audio-recorded interviews were transcribed and data were broken down and inductively coded into four categories. Constant comparative techniques also were used during analysis. The role of the oncology patient navigator included two facets: "Processual facets," with the subthemes assigned to me at diagnosis, managing the connection, mapping the process, practical support, and quarterbacking my entire journey; and "Personal qualities: The essentials," with the subthemes empathetic care tenor, knowing the cancer system, and understanding the medical side of breast cancer. Despite the tremendous effort directed toward enhancing care for younger women undergoing treatment for breast cancer, gaps continue to exist. Younger women with breast cancer require a care approach providing ongoing dialogue, teaching, and emotional support from the point of diagnosis through treatment, including transitions of care within the oncology setting and back to their primary care practitioner. Oncology nurse navigators are well positioned to provide patients with anticipatory guidance from diagnosis to the end of treatment.

Clear speech and lexical competition in younger and older adult listeners.

PubMed

Van Engen, Kristin J

2017-08-01

This study investigated whether clear speech reduces the cognitive demands of lexical competition by crossing speaking style with lexical difficulty. Younger and older adults identified more words in clear versus conversational speech and more easy words than hard words. An initial analysis suggested that the effect of lexical difficulty was reduced in clear speech, but more detailed analyses within each age group showed this interaction was significant only for older adults. The results also showed that both groups improved over the course of the task and that clear speech was particularly helpful for individuals with poorer hearing: for younger adults, clear speech eliminated hearing-related differences that affected performance on conversational speech. For older adults, clear speech was generally more helpful to listeners with poorer hearing. These results suggest that clear speech affords perceptual benefits to all listeners and, for older adults, mitigates the cognitive challenge associated with identifying words with many phonological neighbors.

Late Pleistocene-Holocene deglaciation history in the Baffin Bay from radiogenic isotope provenance studies

NASA Astrophysics Data System (ADS)

Kirillova, V.; Lucassen, F.; Kasemann, S.

2016-12-01

Ice sheets dynamics as well as corresponding meltwater pulses and iceberg calving events play a major role in the delivery and dispersion of continental detritus into the ocean in glaciated environments. To trace Greenland, and potentially, Innuitian and Laurentian ice sheet history and freshwater routing during late Pleistocene to Holocene climate transition, we generate strontium (Sr), neodymium (Nd) and lead (Pb) isotope records as proxies for the provenance of continental detritus on sediment cores from the Baffin Bay: GeoTÜ SL 170, from the Greenland side, covering the last 18.000 years of climate history and GeoTÜ SL 174, close to the western coast, covering 48.000 years. For SL 170, a pronounced shift can be observed in all three isotope systems at 12 ka, what coincides with the Younger Dryas cold event. 87Sr/86Sr is around 0.74 before the event and reaches up to 0.72 during it. Nd isotope composition (IC) changes from ɛNd -32 to -26, and the 206Pb/204Pb values range from 18 to 17. The shift suggests a change in the continental sources from the Archean Southern West Greenland to a slightly younger Proterozoic source of the Nagssugtoqidian Mobile Belt in the Central West Greenland. These results allow us to estimate patterns and timings of deglaciation for different regions of the western Greenland Ice Sheet. In core SL174 variations in ɛNd ( -24 to -30) and 206Pb/204Pb ( 17 to 19) provide no clear evidence for a change of the sediment source within the Younger Dryas, despite the similar range of the values as in core SL 170. 87Sr/86Sr is more radiogenic than in SL 170, reaching values of up to 0.75, but without a systematic relation to the deposition age. Since SL 174 core is located closer to the coast and to the LGM (last glacial maximum) ice sheet border, it was possibly exposed to the direct influence of the marine-terminating ice sheet, which supplied material from enhanced glacial and subglacial erosion. Therefore, radiogenic isotope results for

A prospective follow-up study of younger and older subjects with pathological gambling.

PubMed

Black, Donald W; Coryell, William; McCormick, Brett; Shaw, Martha; Allen, Jeff

2017-10-01

Pathological gambling (PG) is a common and costly public health problem associated with impaired quality of life and high suicide rates. Despite its frequency in the general population, PG course is poorly understood in older adults who are especially vulnerable to its devastating consequences. We enrolled 175 subjects in a longitudinal study of gambling behavior: our case group of 53 older adults with PG (≥ 60 years), and two comparison groups including 72 younger adults with PG (< 40 years) and 50 older adults without PG (≥ 60 years). Subjects with PG met lifetime criteria for DSM-IV PG and had a South Oaks Gambling Screen (SOGS) and National Opinion Research Center DSM Screen for Gambling Problems (NODS) scores ≥ 5. Subjects were evaluated at intake and reassessed every 6 months and drop outs were replaced. Follow-up lasted a mean (SD) of 2.6 (1.4) years. At intake older PGs were more likely to be female, Caucasian, divorced, and to have a lower level of education. Older and younger PGs were similar in gambling severity, but older PGs were more likely to have sought PG treatment. Older PGs had lower rates of lifetime drug use disorders, attention deficit/hyperactivity disorder, and obsessive-compulsive disorder. They preferred slots, were more likely to receive PG treatment, and were less likely to discontinue participation in the study. Week by week gambling activity levels showed a significant general downward movement for older and younger PGs, although there were no differences between the groups. Elders without PG had no change in their level of gambling activity. We conclude that younger and older PGs moved toward a reduced level of gambling activity during follow-up. Our data challenge the notion that PG is chronic and progressive. Copyright © 2017 Elsevier B.V. All rights reserved.

Differing Effects of Younger and Older Human Plasma on C2C12 Myocytes in Vitro.

PubMed

Kalampouka, Ifigeneia; van Bekhoven, Angel; Elliott, Bradley T

2018-01-01

Ageing is associated with a general reduction of physiological function and a reduction of muscle mass and strength. Endocrine factors such as myostatin, activin A, growth and differentiation factor 11 (GDF-11) and their inhibitory peptides influence muscle mass in health and disease. We hypothesised that myocytes cultured in plasma from older and younger individuals would show an ageing effect, with reduced proliferation and differentiation in older environments. C2C12 myoblasts were grown as standard and stimulated with media conditioned with 5% plasma from healthy male participants that were either younger ( n = 6, 18-35 years of age) or older ( n = 6, >57 years of age). Concentration of plasma myostatin (total and free), follistatin-like binding protein (FLRG), GDF-11 and activin A were quantified by ELISA. Both FLRG and activin A were elevated in older individuals (109.6 and 35.1% increase, respectively), whilst myostatin (free and total) and GDF-11 were not. Results indicated that plasma activin A and FLRG were increased in older vs. younger participants, GDF11 and myostatin did not differ. Myoblasts in vitro showed no difference in proliferation rate between ages, however scratch closure was greater in younger vs. older plasma stimulated myoblasts (78.2 vs. 87.2% of baseline scratch diameter, respectively). Myotube diameters were larger in cells stimulated with younger plasma than with older at 24 and 48 h, but not at 2 h. A significant negative correlation was noted between in vivo plasma FLRG concentration and in vitro myotube diameter 48 h following plasma stimulation ( r 2 = 0.392, p = 0.030). Here we show that myoblasts and myotubes cultured in media conditioned with plasma from younger or older individuals show an ageing effect, and further this effect moderately correlates with circulating FLRG concentration in vivo . The effect of ageing on muscle function may not be innate to the tissue, but involve a general cellular environment change. Further

Comparable perioperative mortality outcomes in younger patients undergoing elective open and endovascular abdominal aortic aneurysm repair.

PubMed

Liang, Nathan L; Reitz, Katherine M; Makaroun, Michel S; Malas, Mahmoud B; Tzeng, Edith

2018-05-01

Evidence for benefit of endovascular aneurysm repair (EVAR) over open surgical repair for de novo infrarenal abdominal aortic aneurysms (AAAs) in younger patients remains conflicting because of heterogeneous study populations and small sample sizes. The objective of this study was to compare perioperative and short-term outcomes for EVAR and open surgery in younger patients using a large national disease and procedure-specific data set. We identified patients 65 years of age or younger undergoing first-time elective EVAR or open AAA repair from the Vascular Quality Initiative (2003-2014). We excluded patients with pararenal or thoracoabdominal aneurysms, those medically unfit for open repair, and those undergoing EVAR for isolated iliac aneurysms. Clinical and procedural characteristics were balanced using inverse propensity of treatment weighting. A supplemental analysis extended the study to those younger than 70 years. We identified 2641 patients, 73% (n = 1928) EVAR and 27% (n = 713) open repair. The median age was 62 years (interquartile range, 59-64 years), and 13% were female. The median follow-up time was 401 days (interquartile range, 357-459 days). Unadjusted perioperative survival was 99.6% overall (open repair, 99.1%; EVAR, 99.8%; P < .001), with 97.4% 1-year survival overall (open repair, 97.3%; EVAR, 97.4%; P = .9). Unadjusted reintervention rates were five (open repair) and seven (EVAR) reinterventions per 100 person-years (P = .8). After propensity weighting, the absolute incidence of perioperative mortality was <1% in both groups (open repair, 0.9%, EVAR, 0.2%; P < .001), and complication rates were low. Propensity-weighted survival (hazard ratio, 0.88; 95% confidence interval, 0.56-1.38; P = .6) and reintervention rates (open repair, 6; EVAR, 8; reinterventions per 100 person-years; P = .8) did not differ between the two interventions. The analysis of those younger than 70 years showed similar results. In this study of younger

Age Differences in Emotion Regulation Choice: Older Adults Use Distraction Less Than Younger Adults in High-Intensity Positive Contexts.

PubMed

Martins, Bruna; Sheppes, Gal; Gross, James J; Mather, Mara

2018-04-16

Previous research demonstrates that younger and older adults prefer distraction over engagement (reappraisal) when regulating high-intensity negative emotion. Older adults also demonstrate a greater bias for positive over negative information in attention and memory compared with younger adults. In this study, we investigated whether emotion regulation choice preferences may differ as a function of stimulus valence with age. The effect of stimulus intensity on negative and positive emotion regulation strategy preferences was investigated in younger and older men. Participants indicated whether they favored distraction or reappraisal to attenuate emotional reactions to negative and positive images that varied in intensity. Men in both age-groups preferred distraction over reappraisal when regulating high-intensity emotion. As no age-related strategic differences were found in negative emotion regulation preferences, older men chose to distract less from high-intensity positive images than did younger men. Older men demonstrated greater engagement with highly positive emotional contexts than did younger men. Thus, age differences in emotion regulation goals when faced with intense emotional stimuli depend on the valence of the emotional stimuli.

State-based versus reward-based motivation in younger and older adults.

PubMed

Worthy, Darrell A; Cooper, Jessica A; Byrne, Kaileigh A; Gorlick, Marissa A; Maddox, W Todd

2014-12-01

Recent decision-making work has focused on a distinction between a habitual, model-free neural system that is motivated toward actions that lead directly to reward and a more computationally demanding goal-directed, model-based system that is motivated toward actions that improve one's future state. In this article, we examine how aging affects motivation toward reward-based versus state-based decision making. Participants performed tasks in which one type of option provided larger immediate rewards but the alternative type of option led to larger rewards on future trials, or improvements in state. We predicted that older adults would show a reduced preference for choices that led to improvements in state and a greater preference for choices that maximized immediate reward. We also predicted that fits from a hybrid reinforcement-learning model would indicate greater model-based strategy use in younger than in older adults. In line with these predictions, older adults selected the options that maximized reward more often than did younger adults in three of the four tasks, and modeling results suggested reduced model-based strategy use. In the task where older adults showed similar behavior to younger adults, our model-fitting results suggested that this was due to the utilization of a win-stay-lose-shift heuristic rather than a more complex model-based strategy. Additionally, within older adults, we found that model-based strategy use was positively correlated with memory measures from our neuropsychological test battery. We suggest that this shift from state-based to reward-based motivation may be due to age related declines in the neural structures needed for more computationally demanding model-based decision making.

Visual feature binding in younger and older adults: encoding and suffix interference effects.

PubMed

Brown, Louise A; Niven, Elaine H; Logie, Robert H; Rhodes, Stephen; Allen, Richard J

2017-02-01

Three experiments investigated younger (18-25 yrs) and older (70-88 yrs) adults' temporary memory for colour-shape combinations (binding). We focused upon estimating the magnitude of the binding cost for each age group across encoding time (Experiment 1; 900/1500 ms), presentation format (Experiment 2; simultaneous/sequential), and interference (Experiment 3; control/suffix) conditions. In Experiment 1, encoding time did not differentially influence binding in the two age groups. In Experiment 2, younger adults exhibited poorer binding performance with sequential relative to simultaneous presentation, and serial position analyses highlighted a particular age-related difficulty remembering the middle item of a series (for all memory conditions). Experiments 1-3 demonstrated small to medium binding effect sizes in older adults across all encoding conditions, with binding less accurate than shape memory. However, younger adults also displayed negative effects of binding (small to large) in two of the experiments. Even when older adults exhibited a greater suffix interference effect in Experiment 3, this was for all memory types, not just binding. We therefore conclude that there is no consistent evidence for a visual binding deficit in healthy older adults. This relative preservation contrasts with the specific and substantial deficits in visual feature binding found in several recent studies of Alzheimer's disease.

Younger and Older Adults’ Associative Memory for Social Information: The Role of Information Importance

PubMed Central

Hargis, Mary B.; Castel, Alan D.

2017-01-01

The ability to associate items in memory is critical for social interactions. Older adults show deficits in remembering associative information, but can sometimes remember high-value information. In two experiments, younger and older participants studied faces, names, and occupations that were of differing social value. There were no age differences in the recall of important information in Experiment 1, but age differences were present for less important information. In Experiment 2, when younger adults’ encoding time was reduced, age differences were largely absent. These findings are considered in light of value-directed strategies when remembering social associative information. PMID:28581330

Younger and Sicker: Comparing Micronesians to Other Ethnicities in Hawaii

PubMed Central

Miyamura, Jill; Yamada, Seiji; Sentell, Tetine

2016-01-01

Objectives. We compared the age at admission and the severity of illness of hospitalized Micronesians with 3 other racial/ethnic groups in Hawaii. Methods. With Hawaii Health Information Corporation inpatient data, we determined the age at admission and the severity of illness for 162 152 adult, non–pregnancy-related hospital discharges in Hawaii from 2010 to 2012. We performed multivariable linear regression analyses within major disease categories by racial/ethnic group. We created disease categories with all patient refined–diagnosis related groups. Results. Hospitalized Micronesians were significantly younger at admission than were comparison racial/ethnic groups across all patient refined–diagnosis related group categories. The severity of illness for Micronesians was significantly higher than was that of all comparison racial/ethnic groups for cardiac and infectious diseases, higher than was that of Whites and Japanese for cancer and endocrine hospitalizations, and higher than was that of Native Hawaiians for substance abuse hospitalizations. Conclusions. Micronesians were hospitalized significantly younger and often sicker than were comparison populations. Our results will be useful to researchers, state governments, and hospitals, providers, and health systems for this vulnerable group. PMID:26691107

Action Prediction in Younger versus Older Adults: Neural Correlates of Motor Familiarity

PubMed Central

Diersch, Nadine; Mueller, Karsten; Cross, Emily S.; Stadler, Waltraud; Rieger, Martina; Schütz-Bosbach, Simone

2013-01-01

Generating predictions during action observation is essential for efficient navigation through our social environment. With age, the sensitivity in action prediction declines. In younger adults, the action observation network (AON), consisting of premotor, parietal and occipitotemporal cortices, has been implicated in transforming executed and observed actions into a common code. Much less is known about age-related changes in the neural representation of observed actions. Using fMRI, the present study measured brain activity in younger and older adults during the prediction of temporarily occluded actions (figure skating elements and simple movement exercises). All participants were highly familiar with the movement exercises whereas only some participants were experienced figure skaters. With respect to the AON, the results confirm that this network was preferentially engaged for the more familiar movement exercises. Compared to younger adults, older adults recruited visual regions to perform the task and, additionally, the hippocampus and caudate when the observed actions were familiar to them. Thus, instead of effectively exploiting the sensorimotor matching properties of the AON, older adults seemed to rely predominantly on the visual dynamics of the observed actions to perform the task. Our data further suggest that the caudate played an important role during the prediction of the less familiar figure skating elements in better-performing groups. Together, these findings show that action prediction engages a distributed network in the brain, which is modulated by the content of the observed actions and the age and experience of the observer. PMID:23704980

Action prediction in younger versus older adults: neural correlates of motor familiarity.

PubMed

Diersch, Nadine; Mueller, Karsten; Cross, Emily S; Stadler, Waltraud; Rieger, Martina; Schütz-Bosbach, Simone

2013-01-01

Generating predictions during action observation is essential for efficient navigation through our social environment. With age, the sensitivity in action prediction declines. In younger adults, the action observation network (AON), consisting of premotor, parietal and occipitotemporal cortices, has been implicated in transforming executed and observed actions into a common code. Much less is known about age-related changes in the neural representation of observed actions. Using fMRI, the present study measured brain activity in younger and older adults during the prediction of temporarily occluded actions (figure skating elements and simple movement exercises). All participants were highly familiar with the movement exercises whereas only some participants were experienced figure skaters. With respect to the AON, the results confirm that this network was preferentially engaged for the more familiar movement exercises. Compared to younger adults, older adults recruited visual regions to perform the task and, additionally, the hippocampus and caudate when the observed actions were familiar to them. Thus, instead of effectively exploiting the sensorimotor matching properties of the AON, older adults seemed to rely predominantly on the visual dynamics of the observed actions to perform the task. Our data further suggest that the caudate played an important role during the prediction of the less familiar figure skating elements in better-performing groups. Together, these findings show that action prediction engages a distributed network in the brain, which is modulated by the content of the observed actions and the age and experience of the observer.

The ‘apparent clearance’ of free phenytoin in elderly vs. younger adults

PubMed Central

Wright, Daniel F B; Begg, Evan J

2010-01-01

AIMS To test the hypothesis that the ‘apparent clearance’ of free phenytoin is reduced in elderly patients. METHODS Two separate studies were conducted comparing free phenytoin ‘apparent clearance’ in elderly vs. younger adults. The first study was a retrospective analysis of free phenytoin concentrations measured at Christchurch Hospital from 1997 to 2006. In the second study free phenytoin concentrations were measured prospectively in ambulatory subjects who were taking phenytoin regularly. RESULTS In the retrospective study (n = 29), free phenytoin ‘apparent clearance’ was 0.27 ± 0.04 l kg−1 day−1 (95% CI 0.19, 0.34) in the elderly cohort vs. 0.37 ± 0.06 l kg−1 day−1 (95% CI 0.22, 0.52) in younger adults, but the difference was not statistically significant. In the prospective study, free phenytoin ‘apparent clearance’ showed a non-significant trend to being reduced in the elderly patients (0.12 ± 0.02 l kg−1 day−1, 95% CI 0.07, 0.17) compared with the younger cohort (0.18 ± 0.07 l kg−1 day−1, 95% CI 0.09, 0.26) in those not taking interacting drugs (n = 21). CONCLUSIONS This research does not prove the hypothesis that the ‘apparent clearance’ of free phenytoin is reduced in the elderly. However, the trends found in these two studies are supported by trends in the same direction in other published studies, suggesting an age effect. PMID:20642556

Younger and older adults' collaborative recall of shared and unshared emotional pictures.

PubMed

Barber, Sarah J; Castrellon, Jaime J; Opitz, Philipp; Mather, Mara

2017-07-01

Although a group of people working together recalls more items than any one individual, they recall fewer unique items than the same number of people working apart whose responses are combined. This is known as collaborative inhibition, and it is a robust effect that occurs for both younger and older adults. However, almost all previous studies documenting collaborative inhibition have used stimuli that were neutral in emotional valence, low in arousal, and studied by all group members. In the current experiments, we tested the impact of picture-stimuli valence, picture-stimuli arousal, and information distribution in modulating the magnitude of collaborative inhibition. We included both younger and older adults because there are age differences in how people remember emotional pictures that could modulate any effects of emotion on collaborative inhibition. Results revealed that when information was shared (i.e., studied by all group members), there were robust collaborative inhibition effects for both neutral and emotional stimuli for both younger and older adults. However, when information was unshared (i.e., studied by only a single group member), these effects were attenuated. Together, these results provide mixed support for the retrieval strategy disruption account of collaborative inhibition. Supporting the retrieval strategy disruption account, unshared study information was less susceptible to collaborative inhibition than shared study information. Contradicting the retrieval strategy disruption account, emotional valence and arousal did not modulate the magnitude of collaborative inhibition despite the fact that participants clustered the emotional, but not neutral, information together in memory.

Goals-feedback conditions and episodic memory: Mechanisms for memory gains in older and younger adults.

PubMed

West, Robin L; Dark-Freudeman, Alissa; Bagwell, Dana K

2009-02-01

Research has established that challenging memory goals always lead to score increases for younger adults, and can increase older adults' scores under supportive conditions. This study examined beliefs and on-task effort as potential mechanisms for these self-regulatory gains, in particular to learn whether episodic memory gains across multiple trials of shopping list recall are controlled by the same factors for young and old people. Goals with feedback led to higher recall and strategic categorisation than a control condition. Strategy usage was the strongest predictor of gains over trials for both age groups. Age, goal condition, and effort also predicted scores across the entire sample. Older adults' gains, but not younger adults' gains, were affected significantly by the interaction of self-efficacy beliefs and goal condition, and condition interacted with locus of control to predict younger adult gains. These results emphasise the importance of self-regulatory effort and positive beliefs for facilitating goal-related memory gains.

Cardiovascular reactivity of younger and older adults to positive-, negative-, and mixed-emotion cognitive challenge.

PubMed

Hogan, Michael J; James, Jack E; McCabe, Tadhg R; Kilmartin, Liam; Howard, Siobhán; Noone, Chris

2012-03-01

Although aging is associated with progressive increases in blood pressure level, previous research has been inconsistent as to whether older adults show greater or lesser cardiovascular reactivity (CVR) to emotion than do younger adults. There is reason to believe that these inconsistencies could be clarified by examining age-related differences in hemodynamic profile revealed by measuring the pattern of cardiac output and total peripheral resistance associated with changes in blood pressure reactivity. Accordingly, the present study examined the performance, CVR, and hemodynamic profile of younger and older adults during encoding and recognition of word pairs involving four valence types: positive, negative, mixed (positive/negative), and neutral word pairs. Results revealed higher baseline blood pressure, increased CVR characterized by a vascular hemodynamic profile, and more rapid recovery (especially during encoding) for older than for younger participants. Results are discussed in light of research and theory on the relationship between aging and cardiovascular health. Copyright © 2012 Elsevier B.V. All rights reserved.

Predicting Spanking of Younger and Older Children by Mothers and Fathers.

ERIC Educational Resources Information Center

Day, Randal D.; Peterson, Gary W.; McCracken, Coleen

1998-01-01

Parents' characteristics that influence the incidence of spanking are investigated. Differences between boys and girls, mothers and fathers, older and younger children, Black and White, and married versus single women, as well as attributes of the child, the parent, and the social context are explored using multiple regression analysis. Profiles…

From older to younger: intergenerational promotion of health behaviours in Portuguese families affected by familial amyloid polyneuropathy

PubMed Central

Oliveira, Carla Roma; Mendes, Alvaro; Sousa, Liliana

2017-01-01

The role of older generations in families with hereditary diseases has been recognised and associated to their function as guardians of the family's medical history. However, research is scarce in examining the roles that older generations play in terms of health promotion and risk management towards younger generations, which is particularly evident with incurable genetically inherited disorders such as familial amyloid polyneuropathy (FAP) ATTR Val30Met. This qualitative exploratory study examines the roles that older generations play towards younger generations, in terms of health promotion and risk management, in families with FAP. It also explores the intergenerational flow by analysing who from the older generation plays what role(s) towards whom from the younger generation. This study adopts the critical incidents technique. The sample comprises 18 participants that reported 76 critical incidents. The interviews were audio-taped and submitted for content analysis with the main findings suggesting four roles performed by the older family members towards the younger ones: modelling, encouraging, informing and supporting. The intergenerational flow takes place mostly between women, from mother to daughter, and from older affected individuals to young pre-symptomatic carriers. The older generations can be involved in the clinical practice as partners in supporting younger relatives in families with FAP. Clinical genetic services and the health-care system more broadly might want to consider these roles and the intergenerational flow of support so that this information can be used to maximise health promotion behaviours in at-risk families. PMID:28327574

Memory for general and specific value information in younger and older adults: measuring the limits of strategic control.

PubMed

Castel, Alan D; Farb, Norman A S; Craik, Fergus I M

2007-06-01

The ability to selectively remember important information is a critical function of memory. Although previous research has suggested that older adults are impaired in a variety of episodic memory tasks, recent work has demonstrated that older adults can selectively remember high-value information. In the present research, we examined how younger and older adults selectively remembered words with various assigned numeric point values, to see whether younger adults could remember more specific value information than could older adults. Both groups were equally good at recalling point values when recalling the range of high-value words, but younger adults outperformed older adults when recalling specific values. Although older adults were more likely to recognize negative value words, both groups exhibited control by not recalling negative value information. The findings suggest that although both groups retain high-value information, older adults rely more on gist-based encoding and retrieval operations, whereas younger adults are able to remember specific numeric value information.

Younger and Older Adults' "Good-Enough" Interpretations of Garden-Path Sentences

ERIC Educational Resources Information Center

Christianson, Kiel; Williams, Carrick C.; Zacks, Rose T.; Ferreira, Fernanda

2006-01-01

We report 3 experiments that examined younger and older adults' reliance on "good-enough" interpretations for garden-path sentences (e.g., "While Anna dressed the baby played in the crib") as indicated by their responding "Yes" to questions probing the initial, syntactically unlicensed interpretation (e.g., "Did Anna dress the baby?"). The…

Health Services Utilization between Older and Younger Homeless Adults.(author Abstract)

ERIC Educational Resources Information Center

Nakonezny, Paul A.; Ojeda, Michael

2005-01-01

Purpose: Our purpose in the current study was to examine the relationship between health services utilization delivered by means of the Homeless Outreach Medical Services (HOMES) program and health services utilization delivered by means of the Parkland emergency room and inpatient units among a sample of older and younger homeless adults being…

Prevalence of Elevated Blood Lead Levels and Risk Factors Among Residents Younger Than 6 Years, Puerto Rico--2010.

PubMed

Dignam, Timothy; Rivera García, Brenda; De León, Maridali; Curtis, Gerald; Creanga, Andreea A; Azofeifa, Alejandro; OʼNeill, Maureen; Blanton, Curtis; Kennedy, Chinaro; Rullán, Maria; Caldwell, Kathy; Rullán, John; Brown, Mary Jean

2016-01-01

Limited data exist about blood lead levels (BLLs) and potential exposures among children living in Puerto Rico. The Puerto Rico Department of Health has no formal blood lead surveillance program. We assessed the prevalence of elevated BLLs (≥5 micrograms of lead per deciliter of blood), evaluated household environmental lead levels, and risk factors for BLL among children younger than 6 years of age living in Puerto Rico in 2010. We used a population-based, cross-sectional sampling strategy to enroll an island-representative sample of Puerto Rican children younger than 6 years. We estimated the island-wide weighted prevalence of elevated BLLs and conducted bivariable and multivariable linear regression analyses to ascertain risk factors for elevated BLLs. The analytic data set included 355 households and 439 children younger than 6 years throughout Puerto Rico. The weighted geometric mean BLL of children younger than 6 years was 1.57 μg/dL (95% confidence interval [CI], 1.27-1.88). The weighted prevalence of children younger than 6 years with BLLs of 5 μg/dL or more was 3.18% (95% CI, 0.93-5.43) and for BLLs of 10 μg/dL or more was 0.50% (95% CI, 0-1.31). Higher mean BLLs were significantly associated with data collection during the summer months, a lead-related activity or hobby of anyone in the residence, and maternal education of less than 12 years. Few environmental lead hazards were identified. The prevalence of elevated BLLs among Puerto Rican children younger than 6 years is comparable with the most recent (2007-2010) US national estimate (BLLs ≥5 μg/dL = 2.6% [95% CI = 1.6-4.0]). Our findings suggest that targeted screening of specific higher-risk groups of children younger than 6 years can replace island-wide or insurance-specific policies of mandatory blood lead testing in Puerto Rico.

Clinical spectrum of Kawasaki disease in infants younger than 6 months of age.

PubMed

Burns, J C; Wiggins, J W; Toews, W H; Newburger, J W; Leung, D Y; Wilson, H; Glodé, M P

1986-11-01

We report an unselected series of eight patients younger than 6 months of age with Kawasaki disease evaluated between January 1982 and May 1984. The incidence of coronary artery aneurysms (six patients) and the mortality (two patients) were unusually high in this small series. Because of the confusing clinical presentation in three patients, diagnosis was delayed until pathologic or echocardiographic evidence of coronary vasculitis or aneurysm was discovered. The currently accepted clinical criteria for Kawasaki disease may not always identify patients with the pathologic findings of the syndrome who are younger than 6 months of age. The diagnosis of Kawasaki disease and echocardiographic evaluation of the coronary arteries should be considered in young infants with prolonged fever of unknown origin.

Relationship between perceptual learning in speech and statistical learning in younger and older adults

PubMed Central

Neger, Thordis M.; Rietveld, Toni; Janse, Esther

2014-01-01

Within a few sentences, listeners learn to understand severely degraded speech such as noise-vocoded speech. However, individuals vary in the amount of such perceptual learning and it is unclear what underlies these differences. The present study investigates whether perceptual learning in speech relates to statistical learning, as sensitivity to probabilistic information may aid identification of relevant cues in novel speech input. If statistical learning and perceptual learning (partly) draw on the same general mechanisms, then statistical learning in a non-auditory modality using non-linguistic sequences should predict adaptation to degraded speech. In the present study, 73 older adults (aged over 60 years) and 60 younger adults (aged between 18 and 30 years) performed a visual artificial grammar learning task and were presented with 60 meaningful noise-vocoded sentences in an auditory recall task. Within age groups, sentence recognition performance over exposure was analyzed as a function of statistical learning performance, and other variables that may predict learning (i.e., hearing, vocabulary, attention switching control, working memory, and processing speed). Younger and older adults showed similar amounts of perceptual learning, but only younger adults showed significant statistical learning. In older adults, improvement in understanding noise-vocoded speech was constrained by age. In younger adults, amount of adaptation was associated with lexical knowledge and with statistical learning ability. Thus, individual differences in general cognitive abilities explain listeners' variability in adapting to noise-vocoded speech. Results suggest that perceptual and statistical learning share mechanisms of implicit regularity detection, but that the ability to detect statistical regularities is impaired in older adults if visual sequences are presented quickly. PMID:25225475

Relationship between perceptual learning in speech and statistical learning in younger and older adults.

PubMed

Neger, Thordis M; Rietveld, Toni; Janse, Esther

2014-01-01

Within a few sentences, listeners learn to understand severely degraded speech such as noise-vocoded speech. However, individuals vary in the amount of such perceptual learning and it is unclear what underlies these differences. The present study investigates whether perceptual learning in speech relates to statistical learning, as sensitivity to probabilistic information may aid identification of relevant cues in novel speech input. If statistical learning and perceptual learning (partly) draw on the same general mechanisms, then statistical learning in a non-auditory modality using non-linguistic sequences should predict adaptation to degraded speech. In the present study, 73 older adults (aged over 60 years) and 60 younger adults (aged between 18 and 30 years) performed a visual artificial grammar learning task and were presented with 60 meaningful noise-vocoded sentences in an auditory recall task. Within age groups, sentence recognition performance over exposure was analyzed as a function of statistical learning performance, and other variables that may predict learning (i.e., hearing, vocabulary, attention switching control, working memory, and processing speed). Younger and older adults showed similar amounts of perceptual learning, but only younger adults showed significant statistical learning. In older adults, improvement in understanding noise-vocoded speech was constrained by age. In younger adults, amount of adaptation was associated with lexical knowledge and with statistical learning ability. Thus, individual differences in general cognitive abilities explain listeners' variability in adapting to noise-vocoded speech. Results suggest that perceptual and statistical learning share mechanisms of implicit regularity detection, but that the ability to detect statistical regularities is impaired in older adults if visual sequences are presented quickly.

Expiratory flow limitation and operating lung volumes during exercise in older and younger adults.

PubMed

Smith, Joshua R; Kurti, Stephanie P; Meskimen, Kayla; Harms, Craig A

2017-06-01

We determined the effect of aging on expiratory flow limitation (EFL) and operating lung volumes when matched for lung size. We hypothesized that older adults will exhibit greater EFL and increases in EELV during exercise compared to younger controls. Ten older (5M/5W; >60years old) and nineteen height-matched young adults (10M/9W) were recruited. Young adults were matched for%predicted forced vital capacity (FVC) (Y-matched%Pred FVC; n=10) and absolute FVC (Y-matched FVC; n=10). Tidal flow-volume loops were recorded during the incremental exercise test with maximal flow-volume loops measured pre- and post-exercise. Compared to younger controls, older adults exhibited more EFL at ventilations of 26, 35, 51, and 80L/min. The older group had higher end-inspiratory lung volume compared to Y-matched%Pred FVC group during submaximal ventilations. The older group increased EELV during exercise, while EELV stayed below resting in the Y-matched%Pred FVC group. These data suggest older adults exhibit more EFL and increase EELV earlier during exercise compared to younger adults. Copyright © 2017 Elsevier B.V. All rights reserved.

Is the Risk of Autism in Younger Siblings of Affected Children Moderated by Sex, Race/Ethnicity, or Gestational Age?

PubMed

Xie, Fagen; Peltier, Morgan; Getahun, Darios

2016-10-01

To evaluate the recurrence risk of autism spectrum disorders (ASD) in younger siblings of affected children and determine how it is modified by race/ethnicity and sex. Medical records of children born in a large health maintenance organization (Kaiser Permanent Southern California) hospitals from January 1, 2001, through December 31, 2010, and who remained in our system until 2 to 11 years of age were used to assess the risk of recurrence of ASD in younger siblings. Children born at <28 or >42 weeks gestation, multiple births, or those who were not active members for ≥3 months were excluded. ASD diagnosis was ascertained from DSM-IV codes, and the magnitude of the association was estimated using adjusted relative risks (aRRs). Among eligible younger siblings, 592 (1.11%) had the diagnosis of ASD. The ASD rates were 11.30% and 0.92% for younger siblings of older affected and unaffected siblings, respectively (aRR: 14.27; 95% confidence interval, 11.41-17.83). This association remained after adjusting for potential confounding factors. Race/ethnicity- and gestational age-specific analyses revealed a positive association of similar magnitude across groups. Risk remained higher in younger boys than girls regardless of the sex of affected older siblings. The findings of this study suggest that the risk of ASD in younger siblings is higher if the older sibling has ASD. The risk of ASD in younger siblings of older affected siblings was comparable across gestational age at birth and child's race/ethnicity groups. However, risk remains higher for boys. This study contributes to a better understanding of the influence of race/ethnicity, sex, and gestational age at birth in identifying children at higher risk of ASD.

Younger and older adults' associative memory for social information: The role of information importance.

PubMed

Hargis, Mary B; Castel, Alan D

2017-06-01

The ability to associate items in memory is critical for social interactions. Older adults show deficits in remembering associative information but can sometimes remember high-value information. In two experiments, younger and older participants studied faces, names, and occupations that were of differing social value. There were no age differences in the recall of important information in Experiment 1, but age differences were present for less important information. In Experiment 2, when younger adults' encoding time was reduced, age differences were largely absent. These findings are considered in light of value-directed strategies when remembering social associative information. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

A noninterventional study evaluating the effectiveness of rotigotine and levodopa combination therapy in younger versus older patients with Parkinson's disease.

PubMed

Woitalla, Dirk; Dunac, Antoine; Safavi, Ali; Ceravolo, Maria-Gabriella; Gomez Esteban, Juan Carlos; Pavese, Nicola; Asgharnejad, Mahnaz; Joeres, Lars; Schuller, Jan-Christof; Chaudhuri, K Ray

2018-06-19

PD0013 was a 6-month noninterventional study in clinical practice comparing effectiveness/tolerability of rotigotine+levodopa in younger (<70 years) vs. older (≥70 years) Parkinson's disease (PD) patients. Patients previously received levodopa for ≥6 months as monotherapy/in combination with another dopamine-agonist (DA). Primary variable: Unified PD Rating Scale (UPDRS) Part-II change from baseline to end-of-observation-period (EOP). 91 younger/99 older patients started rotigotine; 68 younger/62 older patients completed the study. Most switched from levodopa+another DA. Addition of rotigotine as first DA was more common in older patients (20.2% vs.15.4%). Mean ± SD rotigotine-exposure: 6.1 ± 3.4 mg/24h younger vs. 4.9 ± 2.4 mg/24h older. Eleven patients changed levodopa dose. At EOP, improvement in mean UPDRS-II was greater in younger patients (p = 0.0289). UPDRS-II responder-rate (≥20% decrease in UPDRS-II score) was higher in younger patients (42.3% vs. 25.9%). Improvement across age groups was similar on PD Sleep Scale-2 and Clinical Global Impressions-Improvement Scale. Adverse drug reactions (ADRs), and discontinuations because of ADRs, were more common among older patients. There were no new safety signals. Despite low rotigotine doses, when added to levodopa/switched from levodopa+another DA, rotigotine led to greater improvement in UPDRS-II in younger patients (<70 years). Individual patient data revealed clinically meaningful improvements in UPDRS-II in both groups.

Local Medicaid Home- and Community-Based Services Spending and Nursing Home Admissions of Younger Adults

PubMed Central

Keohane, Laura; Mor, Vincent

2014-01-01

We used fixed-effect models to examine the relationship between local spending on home- and community-based services (HCBSs) for cash-assisted Medicaid-only disabled (CAMOD) adults and younger adult admissions to nursing homes in the United States during 2001 through 2008, with control for facility and market characteristics and secular trends. We found that increased CAMOD Medicaid HCBS spending at the local level is associated with decreased admissions of younger adults to nursing homes. Our findings suggest that states’ efforts to expand HCBS for this population should continue. PMID:25211711

Local Medicaid home- and community-based services spending and nursing home admissions of younger adults.

PubMed

Thomas, Kali S; Keohane, Laura; Mor, Vincent

2014-11-01

We used fixed-effect models to examine the relationship between local spending on home- and community-based services (HCBSs) for cash-assisted Medicaid-only disabled (CAMOD) adults and younger adult admissions to nursing homes in the United States during 2001 through 2008, with control for facility and market characteristics and secular trends. We found that increased CAMOD Medicaid HCBS spending at the local level is associated with decreased admissions of younger adults to nursing homes. Our findings suggest that states' efforts to expand HCBS for this population should continue.

Relationship of blood pressure, behavioral mood state, and physical activity following caffeine ingestion in younger and older women.

PubMed

Arciero, Paul J; Ormsbee, Michael J

2009-08-01

The purpose of this study was to examine the age-related differences in blood pressure, heart rate, and behavioral mood state after caffeine ingestion in younger and older women. Using a placebo-controlled, double-blind design, 10 younger (Y; 18-22 years) and 10 older (O; 50-67 years) healthy women who were moderate consumers of caffeine (self-reported mean intake: Y, 139 +/- 152 mg.day-1; O, 204 +/- 101 mg.day-1) were investigated. All volunteers were characterized for fasting plasma glucose, insulin, free-fatty acids and caffeine levels, body composition, cardiovascular fitness, physical activity, and energy intake. Before and after placebo and caffeine ingestion (5 mg.kg-1 fat-free mass; approximately 208-270 mg) test days, the following variables were measured in all subjects: plasma caffeine levels, heart rate, blood pressure, and behavioral mood state. Results showed that, following caffeine ingestion: (i) both systolic and diastolic blood pressure (SBP and DBP, respectively) increased significantly (p < 0.05) in the older women (SBP, 128.4 +/- 14.2 vs. 132.1 +/- 13.0 mm Hg (3%); DBP, 80.2 +/- 6.9 vs. 83.4 +/- 7.5 mm Hg (4%), whereas only DBP increased in the younger women (67.1 +/- 4.7 vs. 69.9 +/- 5.4 mm Hg (4.2%); p < 0.05); (ii) heart rate decreased significantly (Y, 59.2 +/- 8.7 to 53.9 +/- 10.6 beats.min-1 (p < 0.05); O, 61.9 +/- 9.2 to 59.2 +/- 8.4 beats.min-1 (p < 0.05)) in both groups; and (iii) self-reported feelings of tension and vigor increased and feelings of fatigue decreased (p < 0.05) in younger women, whereas depression decreased (p < or = 0.05) in older women. Self-reported level of physical activity was inversely related to change in DBP following caffeine ingestion in younger women. In conclusion, blood pressure response is augmented and subjective feelings of behavioral mood state are attenuated to a greater degree in older than in younger women following acute caffeine ingestion. Less physically active younger women are more vulnerable

Using warnings to reduce categorical false memories in younger and older adults.

PubMed

Carmichael, Anna M; Gutchess, Angela H

2016-07-01

Warnings about memory errors can reduce their incidence, although past work has largely focused on associative memory errors. The current study sought to explore whether warnings could be tailored to specifically reduce false recall of categorical information in both younger and older populations. Before encoding word pairs designed to induce categorical false memories, half of the younger and older participants were warned to avoid committing these types of memory errors. Older adults who received a warning committed fewer categorical memory errors, as well as other types of semantic memory errors, than those who did not receive a warning. In contrast, young adults' memory errors did not differ for the warning versus no-warning groups. Our findings provide evidence for the effectiveness of warnings at reducing categorical memory errors in older adults, perhaps by supporting source monitoring, reduction in reliance on gist traces, or through effective metacognitive strategies.

Attitudinal and Intentional Acceptance of Domestic Robots by Younger and Older Adults

PubMed Central

Ezer, Neta; Fisk, Arthur D.; Rogers, Wendy A.

2014-01-01

A study was conducted to examine the expectations that younger and older individuals have about domestic robots and how these expectations relate to robot acceptance. In a questionnaire participants were asked to imagine a robot in their home and to indicate how much items representing technology, social partner, and teammate acceptance matched their robot. There were additional questions about how useful and easy to use they thought their robot would be. The dependent variables were attitudinal and intentional acceptance. The analysis of the responses of 117 older adults (aged 65–86) and 60 younger adults (aged 18–25) indicated that individuals thought of robots foremost as performance-directed machines, less so as social devices, and least as unproductive entities. The robustness of the Technology Acceptance Model to robot acceptance was supported. Technology experience accounted for the variance in robot acceptance due to age. PMID:25584365

Outcomes of Laparoscopic Colectomy in Younger and Older Patients: An Analysis of Nationwide Readmission Database.

PubMed

Mehta, Hemalkumar B; Hughes, Byron D; Sieloff, Eric; Sura, Sneha O; Shan, Yong; Adhikari, Deepak; Senagore, Anthony

2018-04-01

Prior studies report safety and effectiveness of laparoscopic colectomy in older patients. The study aimed to examine the impact of laparoscopic colectomy on 30-day readmissions, discharge destination, hospital length of stay, and cost in younger (19-65 years) and older adults (>65 years). We used the nationwide readmission database from 2013 to study adults undergoing elective colectomy. The outcomes were 30-day readmissions, discharge destination for the index hospitalization (routine, skilled nursing facility [SNF]/intermediate care facility [ICF], home healthcare), length of stay, and cost. Multivariable analyses were conducted to determine the association of laparoscopic colectomy on outcome; logistic regression for 30-day readmission, multinomial logistic regression for discharge destination, and linear regression for length of stay and cost. An interaction between age and colectomy approach was included, and all models controlled gender, income, insurance status, All Patients Refined Diagnosis Related Groups (APR-DRG), Elixhauser comorbidities, hospital bed size, ownership, and teaching status. Of 79,581 colectomies, 40.2% were laparoscopic. Laparoscopic colectomy was more frequent in younger patients (41.9% versus 38.5%, p < .0001). Regardless of age, patients undergoing laparoscopic colectomy were 20% less likely to be readmitted within 30 days (odds ratio [OR] 0.80, confidence interval [95% CI] 0.75-0.85). For postdischarge destination, laparoscopic colectomy offered higher benefits to younger patients (SNF/ICF: OR 0.42, 95% CI 0.36-0.49; home health: OR 0.32, 95% CI 0.30-0.35) than older patients (SNF/ICF: OR 0.50, 95% CI 0.47-0.54; home health: OR 0.59, 95% CI 0.55-0.62). Regardless of age, laparoscopic colectomy resulted in 1.46 days (p < .0001) shorter hospital stays compared to open colectomy. Laparoscopic colectomy had significantly lower cost compared to open approach, particularly in younger ($1,466) versus older ($632) patients

Incidental Memory of Younger and Older Adults for Objects Encountered in a Real World Context

PubMed Central

Qin, Xiaoyan; Bochsler, Tiana M.; Aizpurua, Alaitz; Cheong, Allen M. Y.; Koutstaal, Wilma; Legge, Gordon E.

2014-01-01

Effects of context on the perception of, and incidental memory for, real-world objects have predominantly been investigated in younger individuals, under conditions involving a single static viewpoint. We examined the effects of prior object context and object familiarity on both older and younger adults’ incidental memory for real objects encountered while they traversed a conference room. Recognition memory for context-typical and context-atypical objects was compared with a third group of unfamiliar objects that were not readily named and that had no strongly associated context. Both older and younger adults demonstrated a typicality effect, showing significantly lower 2-alternative-forced-choice recognition of context-typical than context-atypical objects; for these objects, the recognition of older adults either significantly exceeded, or numerically surpassed, that of younger adults. Testing-awareness elevated recognition but did not interact with age or with object type. Older adults showed significantly higher recognition for context-atypical objects than for unfamiliar objects that had no prior strongly associated context. The observation of a typicality effect in both age groups is consistent with preserved semantic schemata processing in aging. The incidental recognition advantage of older over younger adults for the context-typical and context-atypical objects may reflect aging-related differences in goal-related processing, with older adults under comparatively more novel circumstances being more likely to direct their attention to the external environment, or age-related differences in top-down effortful distraction regulation, with older individuals’ attention more readily captured by salient objects in the environment. Older adults’ reduced recognition of unfamiliar objects compared to context-atypical objects may reflect possible age differences in contextually driven expectancy violations. The latter finding underscores the theoretical and

Comparing Effects of Intrinsic and Extrinsic Social Values Between Younger and Older Employees.

PubMed

Yeung, Dannii Y; Fung, Helene H; Chan, Darius K-S

2016-08-17

Socioemotional selectivity theory proposes that older adults emphasize emotional goals and interpersonal closeness to a greater extent than do younger adults, suggesting that holding social work-related values (SWVs) may be beneficial to older employees. This project aimed at examining two dimensions of SWVs, intrinsic and extrinsic SWVs, and tested whether age and work situation would moderate their effects on self-rated job performance. A cross-sectional survey (Study 1, N = 357) and a 14-day experience sampling study (Study 2, N = 77) were conducted among Chinese managerial employees. Study 1 showed that the direct effect of intrinsic SWVs on self-rated job performance was stronger in older employees than in younger employees. Study 2 demonstrated that older employees who valued intrinsic SWVs while being in social situations performed much better than when they did not value intrinsic SWVs but being in social situations; however such positive effect was not shown in younger employees. Findings of this project reveal that the effect of SWVs varies across locus of effect (intrinsic versus extrinsic), age, and work situation. Among older employees, the positive effect of intrinsic SWVs is more crucial than that of extrinsic SWVs on self-rated job performance. Findings of this project imply that intrinsically rewarding incentives would be more effective in motivating older employees to reach peak performance.

Impact of age-relevant goals on future thinking in younger and older adults.

PubMed

Lapp, Leann K; Spaniol, Julia

2017-10-01

This study investigated how personal goals influence age differences in episodic future thinking. Research suggests that personal goals change with age and like autobiographical memory, future thinking is thought to be organised and impacted by personal goals. It was hypothesised that cueing older adults with age-relevant goals should modulate age differences in episodic details and may also influence phenomenological characteristics of imagined scenarios. Healthy younger and older adults completed the Future Thinking Interview [Addis, D. R., Wong, A. T., & Schacter, D. L. (2008). Age-related changes in the episodic simulation of future events. Psychological Science, 19(1), 33-41. doi: 10.1111/j.1467-9280.2008.02043.x ] adapted to activate age-appropriate goals. Narratives were scored with an established protocol to obtain objective measures of episodic and semantic details. Subjective features such as emotionality and personal significance showed age differences as a function of goal domain while other features (e.g., vividness) were unaffected. However, consistent with prior reports, older adults produced fewer episodic details than younger adults and this was not modulated by goal domain. The results do not indicate that goal activation affects level of episodic detail. With respect to phenomenological aspects of future thinking, however, younger adults show more sensitivity to goal activation, compared with older adults.

An Item Response Theory Analysis of DSM–IV Personality Disorder Criteria Across Younger and Older Age Groups

PubMed Central

Balsis, Steve; Gleason, Marci E. J.; Woods, Carol M.; Oltmanns, Thomas F.

2015-01-01

Many of the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM–IV; American Psychiatric Association, 1994) personality disorder (PD) diagnostic criteria focus on a younger social and occupational context. The absence of age-appropriate criteria for older adults forces researchers and clinicians to draw conclusions based on existing criteria, which are likely inadequate. To explore which DSM–IV PD criteria contain age group measurement bias, the authors report 2 analyses of data on nearly 37,000 participants, ages 18–98 years, taken from a public data set that includes 7 of the 10 PDs (antisocial, avoidant, dependent, histrionic, obsessive–compulsive, paranoid, and schizoid). The 1st analysis revealed that older age groups tend to endorse fewer PD criteria than younger age groups. The 2nd analysis revealed that 29% of the criteria contain measurement bias. Although the latent variable structure for each PD was quite similar across younger and older age groups, some individual criteria were differentially endorsed by younger and older adults with equivalent PD pathology. The presence of measurement bias for these criteria raises questions concerning the assessment of PDs in older adults and the interpretation of existing data. PMID:17385993

Injury risk among children in motor vehicle crashes: older versus younger drivers.

PubMed

Bromfield, Samantha G; McGwin, Gerald

2014-11-01

To explore the relationship between injury risk among child occupants involved in motor vehicle collisions according to the age of the vehicle driver. The National Automotive Sampling System Crashworthiness Data System 2000-2009 (n = 10 797) was used to identify demographic, vehicle-, collision- and injury-related characteristics among motor vehicle collision occupants ≤15 years of age. The association between the age of the driver (older vs. younger, defined as individuals <50 years of age vs. individuals ≥50 years of age, respectively) and injury occurrence was estimated using logistic regression adjusting for the potentially confounding effect of occupant, vehicle and collision characteristics. Of the child occupants in motor vehicle collisions, 2.9% were driving with an older driver, and approximately 2.9% were injured while driving with a younger driver (odds ratio 1.03; 95% confidence interval 0.55-1.91). After adjusting for child occupant age, gender, restraint use, seat position and vehicle type, there remained no significant association between the age of the driver (older vs. younger) and the risk of injury (odds ratio 0.92; 95% confidence interval 0.49-1.74). These findings add to the body of literature indicating no difference in injury risk found among children when considering the age of the driver. Research is needed to ascertain the association and further evaluate characteristics more specific to the relationship being explored in this study. © 2014 The Authors. Journal of Paediatrics and Child Health © 2014 Paediatrics and Child Health Division (Royal Australasian College of Physicians).

Phoneme categorization and discrimination in younger and older adults: a comparative analysis of perceptual, lexical, and attentional factors.

PubMed

Mattys, Sven L; Scharenborg, Odette

2014-03-01

This study investigates the extent to which age-related language processing difficulties are due to a decline in sensory processes or to a deterioration of cognitive factors, specifically, attentional control. Two facets of attentional control were examined: inhibition of irrelevant information and divided attention. Younger and older adults were asked to categorize the initial phoneme of spoken syllables ("Was it m or n?"), trying to ignore the lexical status of the syllables. The phonemes were manipulated to range in eight steps from m to n. Participants also did a discrimination task on syllable pairs ("Were the initial sounds the same or different?"). Categorization and discrimination were performed under either divided attention (concurrent visual-search task) or focused attention (no visual task). The results showed that even when the younger and older adults were matched on their discrimination scores: (1) the older adults had more difficulty inhibiting lexical knowledge than did younger adults, (2) divided attention weakened lexical inhibition in both younger and older adults, and (3) divided attention impaired sound discrimination more in older than younger listeners. The results confirm the independent and combined contribution of sensory decline and deficit in attentional control to language processing difficulties associated with aging. The relative weight of these variables and their mechanisms of action are discussed in the context of theories of aging and language. (c) 2014 APA, all rights reserved.

Israeli Arabs develop diverticulitis at a younger age and are more likely to require surgery than Jews.

PubMed

Itai, Ghersin; Slijper, Nadav; Sroka, Gideon; Matter, Ibrahim

2015-01-01

Only few studies have examined the impact of racial differences on the age of onset, course and outcomes of diverticulitis. To provide data about the epidemiology of diverticulitis in northern Israel, and to determine whether ethnicity is a predictor of age of onset, complications, and need for surgery. Was conducted a retrospective review of the charts of all patients diagnosed with a first episode of diverticulitis in our hospital between 2005 and 2012. Were found 638 patients with a first episode of acute diverticulitis in the eight year interval. Israeli Arabs developed a first episode of diverticulitis at a younger age compared to Jews (51.2 vs 63.8 years, p<0.01). Arabs living in rural areas developed diverticulitis at a younger age than Arabs living in urban centers (49.4 vs 54.5 years, P=0.03). Jewish and Arabic men developed diverticulitis at younger age compared to their female counterparts (59.9 vs 66.09, p<0.01, and 47.31 vs 56.93, p<0.01, respectively). Arabs were more likely [odds ratio (OR)=1.81 ,95% confidence interval (CI)1.12-2.90, p=0.017] than Jews to require surgical treatment (urgent or elective) for diverticulitis. Israeli Arabs tend to develop diverticulitis at a younger age and are more likely to require surgical treatment for diverticulitis compared to Jews. Arabs living in rural areas develop diverticulitis at a younger age than Arabs living in urban centers. These findings highlight a need to address the root cause for ethnic differences in onset, course and outcome of acute diverticulitis.

Mortality of Geriatric and Younger Patients with Schizophrenia in the Community

ERIC Educational Resources Information Center

Ran, Mao-Sheng; Chan, Cecilia Lai-Wan; Chen, Eric Yu-Hai; Tang, Cui-Ping; Lin, Fu-Rong; Li, Li; Li, Si-Gan; Mao, Wen-Jun; Hu, Shi-Hui; Schwab, Gerhard; Conwell, Yeates

2008-01-01

Little is known about the differences in mortality among non-institutionalized geriatric and younger patients with schizophrenia. In this study long-term mortality and suicidal behavior of all the geriatric (age greater than or equal to 65 years), middle-age (age 41-64 years), and young (age 15-40 years) subjects with schizophrenia living in a…

Gaze Behavior Consistency among Older and Younger Adults When Looking at Emotional Faces

PubMed Central

Chaby, Laurence; Hupont, Isabelle; Avril, Marie; Luherne-du Boullay, Viviane; Chetouani, Mohamed

2017-01-01

The identification of non-verbal emotional signals, and especially of facial expressions, is essential for successful social communication among humans. Previous research has reported an age-related decline in facial emotion identification, and argued for socio-emotional or aging-brain model explanations. However, more perceptual differences in the gaze strategies that accompany facial emotional processing with advancing age have been under-explored yet. In this study, 22 young (22.2 years) and 22 older (70.4 years) adults were instructed to look at basic facial expressions while their gaze movements were recorded by an eye-tracker. Participants were then asked to identify each emotion, and the unbiased hit rate was applied as performance measure. Gaze data were first analyzed using traditional measures of fixations over two preferential regions of the face (upper and lower areas) for each emotion. Then, to better capture core gaze changes with advancing age, spatio-temporal gaze behaviors were deeper examined using data-driven analysis (dimension reduction, clustering). Results first confirmed that older adults performed worse than younger adults at identifying facial expressions, except for “joy” and “disgust,” and this was accompanied by a gaze preference toward the lower-face. Interestingly, this phenomenon was maintained during the whole time course of stimulus presentation. More importantly, trials corresponding to older adults were more tightly clustered, suggesting that the gaze behavior patterns of older adults are more consistent than those of younger adults. This study demonstrates that, confronted to emotional faces, younger and older adults do not prioritize or ignore the same facial areas. Older adults mainly adopted a focused-gaze strategy, consisting in focusing only on the lower part of the face throughout the whole stimuli display time. This consistency may constitute a robust and distinctive “social signature” of emotional

Origin of increased terrigenous supply to the NE South American continental margin during Heinrich Stadial 1 and the Younger Dryas

NASA Astrophysics Data System (ADS)

Zhang, Yancheng; Chiessi, Cristiano M.; Mulitza, Stefan; Zabel, Matthias; Trindade, Ricardo I. F.; Hollanda, Maria Helena B. M.; Dantas, Elton L.; Govin, Aline; Tiedemann, Ralf; Wefer, Gerold

2015-12-01

We investigate the redistribution of terrigenous materials in the northeastern (NE) South American continental margin during slowdown events of the Atlantic Meridional Overturning Circulation (AMOC). The compilation of stratigraphic data from 108 marine sediment cores collected across the western tropical Atlantic shows an extreme rise in sedimentation rates off the Parnaíba River mouth (about 2°S) during Heinrich Stadial 1 (HS1, 18-15 ka). Sediment core GeoB16206-1, raised offshore the Parnaíba River mouth, documents relatively constant 143Nd/144Nd values (expressed as εNd(0)) throughout the last 30 ka. Whereas the homogeneous εNd(0) data support the input of fluvial sediments by the Parnaíba River from the same source area directly onshore, the increases in Fe/Ca, Al/Si and Rb/Sr during HS1 indicate a marked intensification of fluvial erosion in the Parnaíba River drainage basin. In contrast, the εNd(0) values from sediment core GeoB16224-1 collected off French Guiana (about 7°N) suggest Amazon-sourced materials within the last 30 ka. We attribute the extremely high volume of terrigenous sediments deposited offshore the Parnaíba River mouth during HS1 to (i) an enhanced precipitation in the catchment region and (ii) a reduced North Brazil Current, which are both associated with a weakened AMOC.

Cold Reversal on Kodiak Island, Alaska, Correlated with the European Younger Dryas by Using Variations of Atmospheric C-14 Content

NASA Technical Reports Server (NTRS)

Hajdas, Irka; Bonani, Georges; Boden, Per; Peteet, Dorothy M.; Mann, Daniel H.

1999-01-01

High-resolution AMS (accelerator-mass-spectrometer) radiocarbon dating was performed on late-glacial macrofossils in lake sediments from Kodiak Island, Alaska, and on shells in marine sediments from southwest Sweden. In both records, a dramatic drop in radiocarbon ages equivalent to a rise in the atmospheric C-14 by approximately 70%. coincides with the beginning of the cold period at 11000 yr B.P. (C-14 age). Thus our results show that a close correlation between climatic records around the globe is possible by using a global signature of changes in atmospheric C-14 content.

Leg Strength Comparison between Younger and Middle-age Adults

PubMed Central

Kim, Sukwon; Lockhart, Thurmon; Nam, Chang S.

2009-01-01

Although a risk of occupational musculoskeletal diseases has been identified with age-related strength degradation, strength measures from working group are somewhat sparse. This is especially true for the lower extremity strength measures in dynamic conditions (i.e., isokinetic). The objective of this study was to quantify the lower extremity muscle strength characteristics of three age groups (young, middle, and the elderly). Total of 42 subjects participated in the study: 14 subjects for each age group. A commercial dynamometer was used to evaluate isokinetic and isometric strength at ankle and knee joints. 2 × 2 (Age group (younger, middle-age, and older adult groups) × Gender (male and female)) between-subject design and Post-hoc analysis were performed to evaluate strength differences among three age groups. Post-hoc analysis indicated that, overall, middle-age workers’ leg strengths (i.e. ankle and knee muscles) were significantly different from younger adults while middle-age workers’ leg strengths were virtually identical to older adults’ leg strengths. These results suggested that, overall, 14 middle-age workers in the present study could be at a higher risk of musculoskeletal injuries. Future studies looking at the likelihood of musculoskeletal injuries at different work places and from different working postures at various age levels should be required to validate the current findings. The future study would be a valuable asset in finding intervention strategies such that middle-age workers could stay healthier longer. PMID:20436934

Similarity to the Self Affects Memory for Impressions of Others in Younger and Older Adults

PubMed Central

Park, Jung M.; Gutchess, Angela H.

2015-01-01

Objectives. Similarity to the self has been shown to affect memory for impressions in younger adults, suggesting a self-reference effect in person memory. Because older adults show comparable self-reference effects, but prioritize memory for positive over negative information relative to young adults, we examined age differences in self-similarity effects on memory for positive and negative impressions. Method. Younger and older adults formed positive and negative impressions of others differing in the degree of similarity to the self (high, medium, low). Results. For positive impressions, both groups showed enhanced memory for self-similar others relative to dissimilar others, whereas for negative impressions, memory was poorer for those similar to the self. When collapsed across similarity to the self, younger adults remembered negative impressions better than older adults, but interestingly, older adults exhibited a trend for better memory for the positive impressions. Discussion. Results suggest that self-reference effects in impression memory are preserved with age and that older adults exhibit positivity effects in person memory consistent with previous findings. PMID:24389124

Story Processing Ability in Cognitively Healthy Younger and Older Adults

PubMed Central

Wright, Heather Harris; Capilouto, Gilson J.; Srinivasan, Cidambi; Fergadiotis, Gerasimos

2012-01-01

Purpose The purpose of the study was to examine the relationships among measures of comprehension and production for stories depicted in wordless pictures books and measures of memory and attention for 2 age groups. Method Sixty cognitively healthy adults participated. They consisted of two groups—young adults (20–29 years of age) and older adults (70–89 years of age). Participants completed cognitive measures and several discourse tasks; these included telling stories depicted in wordless picture books and answering multiple-choice comprehension questions pertaining to the story. Results The 2 groups did not differ significantly for proportion of story propositions conveyed; however, the younger group performed significantly better on the comprehension measure as compared with the older group. Only the older group demonstrated a statistically significant relationship between the story measures. Performance on the production and comprehension measures significantly correlated with performance on the cognitive measures for the older group but not for the younger group. Conclusions The relationship between adults’ comprehension of stimuli used to elicit narrative production samples and their narrative productions differed across the life span, suggesting that discourse processing performance changes in healthy aging. Finally, the study’s findings suggest that memory and attention contribute to older adults’ story processing performance. PMID:21106701

Memory for staged events: Supporting older and younger adults' memory with SenseCam.

PubMed

Mair, Ali; Poirier, Marie; Conway, Martin A

2018-03-01

Two experiments measured the effect of retrieval support provided by a wearable camera, SenseCam, on older and younger adults' memory for a recently experienced complex staged event. In each experiment, participants completed a series of tasks in groups, and the events were recalled 2 weeks later, after viewing SenseCam images (experimental condition) or thinking about the event (control condition). When IQ and education were matched, young adults recalled more event details than older adults, demonstrating an age-related deficit for novel autobiographical material. Reviewing SenseCam images increased the number of details recalled by older and younger adults, and the effect was similar for both groups. These results suggest that memory can be supported by the use of SenseCam, but the age-related deficit is not eliminated.

Preferences for emotional information in older and younger adults: a meta-analysis of memory and attention tasks.

PubMed

Murphy, Nora A; Isaacowitz, Derek M

2008-06-01

The authors conducted a meta-analysis to determine the magnitude of older and younger adults' preferences for emotional stimuli in studies of attention and memory. Analyses involved 1,085 older adults from 37 independent samples and 3,150 younger adults from 86 independent samples. Both age groups exhibited small to medium emotion salience effects (i.e., preference for emotionally valenced stimuli over neutral stimuli) as well as positivity preferences (i.e., preference for positively valenced stimuli over neutral stimuli) and negativity preferences (i.e., preference for negatively valenced stimuli to neutral stimuli). There were few age differences overall. Type of measurement appeared to influence the magnitude of effects; recognition studies indicated significant age effects, where older adults showed smaller effects for emotion salience and negativity preferences than younger adults.

Relate it! Objective and subjective evaluation of mediator-based strategies for improving source memory in younger and older adults.

PubMed

Kuhlmann, Beatrice G; Touron, Dayna R

2017-06-01

The present study examined younger and older adults' ability to improve their source memory for different types of sources through imaginal and verbal (sentence) mediators. Younger (18-29 years) and older (60-75 years) adults' strategy use and source memory for either text-type (bold vs italic) or person (woman vs man) sources was assessed; strategy use was either spontaneous or the generation of imaginal mediators was instructed before encoding. Younger and older adults did not differ in spontaneous use of mediator-based strategies; however, older adults generated more images but fewer verbal mediators than younger adults. Participants were able to increase mediator generation when instructed to, resulting in substantial increases in both item and source memory for the instructed conditions in both age groups. Use of verbal mediators was more likely for the more concrete person sources for which source memory was generally better. Importantly, these objective benefits of mediator-based strategies translated into subjective benefits for both younger and older adults: Increased use of either mediator type was correlated with lower experienced task difficulty; the instructions to use imaginal mediators resulted in a significant decrease in difficulty ratings on the group level. Participants were generally able to monitor mediator benefits to both item and source memory and accurately judged mediator strategies (especially imagery) as more effective than repetition; older adults, however, rated all strategies as less effective than younger adults. Implications of these findings, especially for neuropsychological studies on source monitoring, are discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Cross-Sectional Analysis of Per Capita Supply of Doctors of Chiropractic and Opioid Use in Younger Medicare Beneficiaries.

PubMed

Weeks, William B; Goertz, Christine M

2016-05-01

The purpose of this study was to determine whether the per-capita supply of doctors of chiropractic (DCs) or Medicare spending on chiropractic care was associated with opioid use among younger, disabled Medicare beneficiaries. Using 2011 data, at the hospital referral region level, we correlated the per-capita supply of DCs and spending on chiropractic manipulative therapy (CMT) with several measures of per-capita opioid use by younger, disabled Medicare beneficiaries. Per-capita supply of DCs and spending on CMT were strongly inversely correlated with the percentage of younger Medicare beneficiaries who had at least 1, as well as with 6 or more, opioid prescription fills. Neither measure was correlated with mean daily morphine equivalents per opioid user or per chronic opioid user. A higher per-capita supply of DCs and Medicare spending on CMT were inversely associated with younger, disabled Medicare beneficiaries obtaining an opioid prescription. However, neither measure was associated with opioid dosage among patients who obtained opioid prescriptions. Copyright © 2016. Published by Elsevier Inc.

Impacts of suppression on emotional responses and performance outcomes: an experience-sampling study in younger and older workers.

PubMed

Yeung, Dannii Y; Fung, Helene H

2012-11-01

Past studies have demonstrated that older adults used less emotional suppression to regulate their emotions than did younger adults, but the effectiveness of using this emotion regulatory strategy on psychosocial well-being across age remains largely unexplored. The present study adopted an experience-sampling method to examine whether the impacts of momentary employment of emotional suppression on momentary positive and negative emotions and job performance would be different by age. Eighty-seven Chinese insurance workers, aged between 18 and 61 years, participated in a 5-day sampling study. Their affective responses at work, momentary task performance, and sales productivity were recorded. Results showed that older workers' greater use of suppression at work was associated with lower intensity of negative emotions, whereas such association was not found among younger workers. Moreover, greater use of suppression over the sampling period was significantly predictive of sales productivity of older workers, but such a positive association was not shown in younger workers. These findings reveal that the use of suppression at work may be more effective for older workers than for younger workers.

Superior Recognition Performance for Happy Masked and Unmasked Faces in Both Younger and Older Adults

PubMed Central

Svärd, Joakim; Wiens, Stefan; Fischer, Håkan

2012-01-01

In the aging literature it has been shown that even though emotion recognition performance decreases with age, the decrease is less for happiness than other facial expressions. Studies in younger adults have also revealed that happy faces are more strongly attended to and better recognized than other emotional facial expressions. Thus, there might be a more age independent happy face advantage in facial expression recognition. By using a backward masking paradigm and varying stimulus onset asynchronies (17–267 ms) the temporal development of a happy face advantage, on a continuum from low to high levels of visibility, was examined in younger and older adults. Results showed that across age groups, recognition performance for happy faces was better than for neutral and fearful faces at durations longer than 50 ms. Importantly, the results showed a happy face advantage already during early processing of emotional faces in both younger and older adults. This advantage is discussed in terms of processing of salient perceptual features and elaborative processing of the happy face. We also investigate the combined effect of age and neuroticism on emotional face processing. The rationale was previous findings of age-related differences in physiological arousal to emotional pictures and a relation between arousal and neuroticism. Across all durations, there was an interaction between age and neuroticism, showing that being high in neuroticism might be disadvantageous for younger, but not older adults’ emotion recognition performance during arousal enhancing tasks. These results indicate that there is a relation between aging, neuroticism, and performance, potentially related to physiological arousal. PMID:23226135

The choices we make: An examination of situation selection in younger and older adults

PubMed Central

Rovenpor, Daniel R.; Skogsberg, Nikolaus J.; Isaacowitz, Derek M.

2013-01-01

The current study examined the effects of age and control beliefs on the use of situation selection. Younger and older adults spent 15 minutes in a room containing multiple affective streams that varied in emotional valence, and were given free choice to engage with whatever they wanted. No significant main effect of age emerged on the number of choices of, or time spent with, material of each valence. However, age and beliefs interacted such that older adults with strong emotion regulation self-efficacy and general control beliefs chose fewer negative stimuli, whereas younger adults with strong beliefs chose more negative stimuli. Results are discussed from aging and individual differences perspectives. PMID:23088197

Pharmacokinetics and effect on the corrected QT interval of single-dose escitalopram in healthy elderly compared with younger adults.

PubMed

Chung, Hyewon; Kim, Anhye; Lim, Kyoung Soo; Park, Sang-In; Yu, Kyung-Sang; Yoon, Seo Hyun; Cho, Joo-Youn; Chung, Jae-Yong

2017-01-01

Escitalopram is the (S)-enantiomer of citalopram that has a potential QT prolonging effect. In this study, 12 healthy elderly individuals received a single oral dose of escitalopram (20 mg), and their pharmacokinetics and QT effect data were compared with data from 33 younger adults obtained in a previous study. Serial blood samples for pharmacokinetic analysis were collected and ECG was performed up to 48 h postdose. The elderly and younger adults showed similar pharmacokinetic profiles. The geometric mean ratios (90% confidence interval) of the elderly compared with the younger adults were 1.02 (0.89-1.17) and 1.01 (0.86-1.17) for the maximum plasma concentration and area under the concentration-time curve, respectively. The mean baseline-adjusted QT (dQT) time profiles were similar and the mean values of maximum dQT were not significantly different between the elderly and the younger adults. The linear mixed-effect model indicated a weak but positive relationship between the escitalopram concentration and dQT, with an estimated coefficient of concentration of 0.43-0.54. In conclusion, the pharmacokinetics and QT effect of a single dose of escitalopram observed in the elderly without comorbidities and younger adults were generally similar.

Age Differences in Attachment Orientations among Younger and Older Adults: Evidence from Two Self-Report Measures of Attachment

ERIC Educational Resources Information Center

Segal, Daniel L.; Needham, Tracy N.; Coolidge, Frederick L.

2009-01-01

The attachment patterns of younger and older adults were studied using two-dimensional self-report measures of adult attachment. Community-dwelling younger (n = 144, M = 22.5 years, SD = 3.6) and older (n = 106, M = 68.6 years, SD = 8.3) adults completed the Measure of Attachment Qualities (MAQ; Carver, 1997) and the Relationship Style…

Family Caregivers' Experiences of Caring for a Relative With Younger Onset Dementia: A Qualitative Systematic Review.

PubMed

Cabote, Christy Joy; Bramble, Marguerite; McCann, Damhnat

2015-08-01

Family caregiving for people with younger onset dementia affects everyone in the family unit. This article presents findings of a qualitative systematic review exploring the experiences of family caregivers of persons with younger onset dementia. A systematic search resulted in the inclusion of five relevant articles, and two groups within the family unit were identified-child caregivers and adult and spousal caregivers. Using the thematic synthesis approach, five themes emerged: dementia damage, grief for loss of relationship, changes in family roles, positive and negative impacts of family caregiving, and transition to formal care. The review findings support increasing evidence that despite the stress of caring for a person with dementia damage, family members have the capacity to cope, adapt, and grow through their experiences. Nurses can assist families to identify their unique strengths and enhance family resiliency so they can navigate the "lonely road" of younger onset dementia. © The Author(s) 2015.

Inertial Sensor Based Analysis of Lie-to-Stand Transfers in Younger and Older Adults

PubMed Central

Schwickert, Lars; Boos, Ronald; Klenk, Jochen; Bourke, Alan; Becker, Clemens; Zijlstra, Wiebren

2016-01-01

Many older adults lack the capacity to stand up again after a fall. Therefore, to analyse falls it is relevant to understand recovery patterns, including successful and failed attempts to get up from the floor in general. This study analysed different kinematic features of standing up from the floor. We used inertial sensors to describe the kinematics of lie-to-stand transfer patterns of younger and healthy older adults. Fourteen younger (20–50 years of age, 50% men) and 10 healthy older community dwellers (≥60 years; 50% men) conducted four lie-to-stand transfers from different initial lying postures. The analysed temporal, kinematic, and elliptic fitting complexity measures of transfer performance were significantly different between younger and older subjects (i.e., transfer duration, angular velocity (RMS), maximum vertical acceleration, maximum vertical velocity, smoothness, fluency, ellipse width, angle between ellipses). These results show the feasibility and potential of analysing kinematic features to describe the lie-to-stand transfer performance, to help design interventions and detection approaches to prevent long lies after falls. It is possible to describe age-related differences in lie-to-stand transfer performance using inertial sensors. The kinematic analysis remains to be tested on patterns after real-world falls. PMID:27529249

The Lateglacial to Holocene transition as recorded by glacier fluctuations

NASA Astrophysics Data System (ADS)

Schindelwig, I.; Akçar, N.; Kubik, P. W.; Schlüchter, C.

2009-04-01

Examination of glacier associated records may contribute to a better understanding of the ice-continent-ocean-atmosphere interactions, since glacial deposits related to short-term temperature fluctuations, driven by climate change, might be preserved. Surface exposure dating (SED) of such glacial deposits can improve the chronology of climate records. The western Swiss Alps repeatedly hosted mountain glaciers during the Pleistocene, and even during the Last Glacial-Interglacial transition, with abundant stadial and interstadial transitions during the Lateglacial (e.g. Björck et al. 1998). In this study, the adjacent valleys of Belalp and Great Aletsch (catchment area is generally south facing) in the western Swiss Alps are investigated. The slow responding Great Aletsch valley glacier shows only one confirmed moraine ridge related to the Lateglacial (Egesen stadial) (Kelly et al. 2004). However, the rather fast responding Unnerbäch cirque (recent) glacier at the Belalp (a similarly exposed - and tributary - valley to the Great Aletsch valley), features 6 individual lateral-terminal moraine ridges related to Lateglacial and early Holocene times. In the Belalp valley, 22 erratic boulders from four out of six well-preserved moraines were sampled in order to establish a detailed chronological framework. From the Great Aletsch valley four samples (boulder and ice moulded bedrock) of the lateral moraine were collected for SED. Our 10Be exposure dates suggest a stabilization of the Great Aletsch moraine related to the Egesen advance in the beginning of the Younger Dryas, assuming that the ages of the oldest erratic boulders on a single moraine ridge are representative for the time of moraine stabilization (Putkonen & Swanson, 2003). According to our investigations on the right-lateral moraine and the dataset (recalculated from Kelly et al. 2004) for the left-lateral moraine, the Egesen stadial is the first preserved re-advance after the last deglaciation. In contrast

Cardiac pathologic findings reveal a high rate of sudden cardiac death of undetermined etiology in younger women.

PubMed

Chugh, Sumeet S; Chung, Kiyon; Zheng, Zhi-Jie; John, Benjamin; Titus, Jack L

2003-10-01

Between 1989 and 1998 there was a 21% increase in estimated sudden cardiac death among US women aged 35 to 44 years. In contrast, the sudden cardiac death rate in age-matched men showed a decreasing trend (-2.8%). Due to under-representation of younger adults in published autopsy series, etiologies of sudden cardiac death merit further investigation. We reviewed autopsy and detailed cardiac pathologic findings in younger women (age 35-44 years) from a 270-patient, 13-year (1984-1996) autopsy series of sudden cardiac death, and performed comparisons with findings in age-matched men. Women aged 35 to 44 years constituted 32% of all women in the series compared to men, who constituted 24% of total men (P =.004 vs women). A presumptive cause of sudden cardiac death could not be determined in 13 women (50%). Among women, 6 cases (22%) had significant coronary artery disease. Findings in others included coronary artery anomalies (n = 3), myocarditis (n = 2), hypertrophic cardiomyopathy (n = 1), coronary artery dissection (n = 1) and accessory pathway (n = 1). In younger men, a presumptive cause of sudden cardiac death remained undetermined in only 24% (P =.025 vs younger women), and coronary artery disease accounted for 40% of cases. In younger women, despite autopsy and detailed cardiac pathologic examination, an attributable cause of sudden cardiac death was not determined in 50% of cases; a 2-fold increase compared to men of the same age. Given the dynamic and multifactorial nature of sudden cardiac death, comprehensive population-based investigations are likely to be necessary to further investigate this unexpected sex-based disparity.

Cannabis Use Patterns and Motives: A Comparison of Younger, Middle-Aged, and Older Medical Cannabis Dispensary Patients

PubMed Central

Haug, Nancy A.; Padula, Claudia B.; Sottile, James E.; Vandrey, Ryan; Heinz, Adrienne J.; Bonn-Miller, Marcel O.

2017-01-01

Introduction Medical cannabis is increasingly being used for a variety of health conditions as more states implement legislation permitting medical use of cannabis. Little is known about medical cannabis use patterns and motives among adults across the lifespan. Methods The present study examined data collected at a medical cannabis dispensary in San Francisco, California. Participants included 217 medical cannabis patients who were grouped into age-defined cohorts (younger: 18–30, middle-aged: 31–50, and older: 51–72). The age groups were compared on several measures of cannabis use, motives and medical conditions using one-way ANOVAs, chi-square tests and linear regression analyses. Results All three age groups had similar frequency of cannabis use over the past month; however, the quantity of cannabis used and rates of problematic cannabis use were higher among younger users relative to middle-aged and older adults. The association between age and problematic cannabis use was moderated by age of regular use initiation such that earlier age of regular cannabis use onset was associated with more problematic use in the younger users, but not among older users. Middle-aged adults were more likely to report using medical cannabis for insomnia, while older adults were more likely to use medical cannabis for chronic medical problems such as cancer, glaucoma and HIV/AIDS. Younger participants reported cannabis use when bored at a greater rate than middle-aged and older adults. Conclusions Findings suggest that there is an age-related risk for problematic cannabis use among medical cannabis users, such that younger users should be monitored for cannabis use patterns that may lead to deleterious consequences. PMID:28340421

Cannabis use patterns and motives: A comparison of younger, middle-aged, and older medical cannabis dispensary patients.

PubMed

Haug, Nancy A; Padula, Claudia B; Sottile, James E; Vandrey, Ryan; Heinz, Adrienne J; Bonn-Miller, Marcel O

2017-09-01

Medical cannabis is increasingly being used for a variety of health conditions as more states implement legislation permitting medical use of cannabis. Little is known about medical cannabis use patterns and motives among adults across the lifespan. The present study examined data collected at a medical cannabis dispensary in San Francisco, California. Participants included 217 medical cannabis patients who were grouped into age-defined cohorts (younger: 18-30, middle-aged: 31-50, and older: 51-72). The age groups were compared on several measures of cannabis use, motives and medical conditions using one-way ANOVAs, chi-square tests and linear regression analyses. All three age groups had similar frequency of cannabis use over the past month; however, the quantity of cannabis used and rates of problematic cannabis use were higher among younger users relative to middle-aged and older adults. The association between age and problematic cannabis use was moderated by age of regular use initiation such that earlier age of regular cannabis use onset was associated with more problematic use in the younger users, but not among older users. Middle-aged adults were more likely to report using medical cannabis for insomnia, while older adults were more likely to use medical cannabis for chronic medical problems such as cancer, glaucoma and HIV/AIDS. Younger participants reported cannabis use when bored at a greater rate than middle-aged and older adults. Findings suggest that there is an age-related risk for problematic cannabis use among medical cannabis users, such that younger users should be monitored for cannabis use patterns that may lead to deleterious consequences. Copyright © 2017 Elsevier Ltd. All rights reserved.

Israeli Arabs develop diverticulitis at a younger age and are more likely to require surgery than Jews

PubMed Central

Itai, GHERSIN; SLIJPER, Nadav; SROKA, Gideon; MATTER, Ibrahim

2015-01-01

Background Only few studies have examined the impact of racial differences on the age of onset, course and outcomes of diverticulitis. Aim To provide data about the epidemiology of diverticulitis in northern Israel, and to determine whether ethnicity is a predictor of age of onset, complications, and need for surgery. Methods Was conducted a retrospective review of the charts of all patients diagnosed with a first episode of diverticulitis in our hospital between 2005 and 2012. Results Were found 638 patients with a first episode of acute diverticulitis in the eight year interval. Israeli Arabs developed a first episode of diverticulitis at a younger age compared to Jews (51.2 vs 63.8 years, p<0.01). Arabs living in rural areas developed diverticulitis at a younger age than Arabs living in urban centers (49.4 vs 54.5 years, P=0.03). Jewish and Arabic men developed diverticulitis at younger age compared to their female counterparts (59.9 vs 66.09, p<0.01, and 47.31 vs 56.93, p<0.01, respectively). Arabs were more likely [odds ratio (OR)=1.81 ,95% confidence interval (CI)1.12-2.90, p=0.017] than Jews to require surgical treatment (urgent or elective) for diverticulitis. Conclusions Israeli Arabs tend to develop diverticulitis at a younger age and are more likely to require surgical treatment for diverticulitis compared to Jews. Arabs living in rural areas develop diverticulitis at a younger age than Arabs living in urban centers. These findings highlight a need to address the root cause for ethnic differences in onset, course and outcome of acute diverticulitis. PMID:26176244

Examining the Usability of Touch Screen Gestures for Older and Younger Adults.

PubMed

Gao, Qin; Sun, Qiqi

2015-08-01

We examined the usability issues associated with four touch screen gestures (clicking, dragging, zooming, and rotating) among older and younger users. It is especially important to accommodate older users' characteristics to ensure the accessibility of information and services that are important to their quality of life. Forty older and 40 younger participants completed four experiments, each of which focused on one gesture. The effects of age, type of touch screen (surface acoustic wave vs. optical), inclination angle (30°, 45°, 60°, and 75°), and user interface factors (clicking: button size and spacing; dragging: dragging direction and distance; zooming: design of zooming gesture; rotating: design of rotating gesture) on user performance and satisfaction were examined. Button sizes that are larger than 15.9 × 9.0 mm led to better performance and higher satisfaction. The effect of spacing was significant only when the button size was notably small or large. Rightward and downward dragging were preferred to leftward and upward dragging, respectively. The younger participants favored direct manipulation gestures using multiple fingers, whereas the older participants preferred the click-to design. The older participants working with large inclination angles of 60° to 75° reported a higher level of satisfaction than the older participants working with smaller angles. We proposed a set of design guidelines for touch screen user interfaces and discussed implications for the selection of appropriate technology and the configuration of the workspace. The implications are useful for the design of large touch screen applications, such as desktop computers, information kiosks, and health care support systems. © 2015, Human Factors and Ergonomics Society.

Motivating Millennials: Improving Practices in Recruiting, Retaining, and Motivating Younger Library Staff

ERIC Educational Resources Information Center

Smith, Sara D.; Galbraith, Quinn

2012-01-01

Working with younger staff and student employees can be a challenge for library supervisors in a multigenerational workplace. Because members of the Millennial Generation have different work expectations, managers need to adjust to best meet their needs. By surveying its five hundred student employees, Brigham Young University's Harold B. Lee…

Listening effort in younger and older adults: A comparison of auditory-only and auditory-visual presentations

PubMed Central

Sommers, Mitchell S.; Phelps, Damian

2016-01-01

One goal of the present study was to establish whether providing younger and older adults with visual speech information (both seeing and hearing a talker compared with listening alone) would reduce listening effort for understanding speech in noise. In addition, we used an individual differences approach to assess whether changes in listening effort were related to changes in visual enhancement – the improvement in speech understanding in going from an auditory-only (A-only) to an auditory-visual condition (AV) condition. To compare word recognition in A-only and AV modalities, younger and older adults identified words in both A-only and AV conditions in the presence of six-talker babble. Listening effort was assessed using a modified version of a serial recall task. Participants heard (A-only) or saw and heard (AV) a talker producing individual words without background noise. List presentation was stopped randomly and participants were then asked to repeat the last 3 words that were presented. Listening effort was assessed using recall performance in the 2-back and 3-back positions. Younger, but not older, adults exhibited reduced listening effort as indexed by greater recall in the 2- and 3-back positions for the AV compared with the A-only presentations. For younger, but not older adults, changes in performance from the A-only to the AV condition were moderately correlated with visual enhancement. Results are discussed within a limited-resource model of both A-only and AV speech perception. PMID:27355772

Lower subcortical gray matter volume in both younger smokers and established smokers relative to non-smokers

PubMed Central

Hanlon, Colleen A.; Owens, Max M.; Joseph, Jane E.; Zhu, Xun; George, Mark S.; Brady, Kathleen T.; Hartwell, Karen J.

2014-01-01

Although established adult smokers with long histories of nicotine dependence have lower neural tissue volume than non-smokers, it is not clear if lower regional brain volume is also observed in younger, less established smokers. The primary goal of this study was to investigate neural tissue volume in a large group of smokers and non-smokers, with a secondary goal of measuring the impact of age on these effects. We used voxel-based morphometry to compare regional gray matter volume in 118 individuals (59 smokers, 59 age- and gender-matched non-smokers). Younger smokers had significantly lower gray matter volume in the left thalamus and the left amygdala than their non-smoking peers (family-wise error-corrected clusters, P < 0.05). There was no correlation between smoking use variables and tissue volume among younger smokers. Established smokers had significantly lower gray matter volume than age-matched non-smokers in the insula, parahippocampal gyrus and pallidum. Medial prefrontal cortex gray matter volume was negatively correlated with pack-years of smoking among the established smokers, but not the younger smokers. These data reveal that regional tissue volume differences are not limited exclusively to established smokers. Deficits in young adults indicate that cigarette smoking may either be deleterious to the thalamus and amygdala at an earlier age than previously reported, or that pre-existing differences in these areas may predispose individuals to the development of nicotine dependence. PMID:25125263

Treatment Costs of Breast Cancer Among Younger Women Aged 19-44 Years Enrolled in Medicaid.

PubMed

Ekwueme, Donatus U; Allaire, Benjamin T; Guy, Gery P; Arnold, Sarah; Trogdon, Justin G

2016-02-01

A few studies have examined the costs of breast cancer treatment in a Medicaid population at the state level. However, no study has estimated medical costs for breast cancer treatment at the national level for women aged 19-44 years enrolled in Medicaid. A sample of 5,542 younger women aged 19-44 years enrolled in fee-for-service Medicaid with diagnosis codes for breast cancer in 2007 were compared with 4.3 million women aged 19-44 years enrolled in fee-for-service Medicaid without breast cancer. Nonlinear regression methods estimated prevalent treatment costs for younger women with breast cancer compared with those without breast cancer. Individual medical costs were estimated by race/ethnicity and by type of services. Analyses were conducted in 2013 and all medical treatment costs were adjusted to 2012 U.S. dollars. The estimated monthly direct medical costs for breast cancer treatment among younger women enrolled in Medicaid was $5,711 (95% CI=$5,039, $6,383) per woman. The estimated monthly cost for outpatient services was $4,058 (95% CI=$3,575, $4,541), for inpatient services was $1,003 (95% CI=$708, $1,298), and for prescription drugs was $539 (95% CI=$431, $647). By race/ethnicity, non-Hispanic white women had the highest monthly total medical costs, followed by Hispanic women and non-Hispanic women of other race. Cost estimates demonstrate the substantial medical costs associated with breast cancer treatment for younger Medicaid beneficiaries. As the Medicaid program continues to evolve, the treatment cost estimates could serve as important inputs in decision making regarding planning for treatment of invasive breast cancer in this population. Published by Elsevier Inc.

Characteristics of Emergency Department Visits by Older Versus Younger Homeless Adults in the United States

PubMed Central

Steinman, Michael A.

2013-01-01

Objectives. We compared the characteristics of emergency department (ED) visits of older versus younger homeless adults. Methods. We analyzed 2005–2009 data from the National Hospital Ambulatory Medical Care Survey, a nationally representative survey of visits to hospitals and EDs, and used sampling weights, strata, and clustering variables to obtain nationally representative estimates. Results. The ED visits of homeless adults aged 50 years and older accounted for 36% of annual visits by homeless patients. Although demographic characteristics of ED visits were similar in older and younger homeless adults, clinical and health services characteristics differed. Older homeless adults had fewer discharge diagnoses related to psychiatric conditions (10% vs 20%; P = .002) and drug abuse (7% vs 15%; P = .003) but more diagnoses related to alcohol abuse (31% vs 23%; P = .03) and were more likely to arrive by ambulance (48% vs 36%; P = .02) and to be admitted to the hospital (20% vs 11%; P = .003). Conclusions. Older homeless adults’ patterns of ED care differ from those of younger homeless adults. Health care systems need to account for these differences to meet the needs of the aging homeless population. PMID:23597348

Age differences in emotion regulation effort: Pupil response distinguishes reappraisal and distraction for older but not younger adults.

PubMed

Martins, Bruna; Florjanczyk, Jan; Jackson, Nicholas J; Gatz, Margaret; Mather, Mara

2018-03-01

In previous research, older adults show greater emotional benefits from distracting themselves than from reappraising an event when strategically regulating emotion. Older adults also demonstrate an attentional preference to avoid, while younger adults show a bias toward approaching negative stimuli. This suggests a possible age-related differentiation of cognitive effort across approach and avoidance of negative stimuli during emotion regulation. In this study, we tracked cognitive effort via pupil dilation during the use of distraction (avoidance) and reappraisal (approach) strategies across age. Forty-eight younger adults (M = 20.94, SD = 1.78; 19 men) and 48 older adults (M = 68.82, SD = 5.40; 15 men) viewed a slideshow of negative images and were instructed to distract, reappraise, or passively view each image. Older adults showed greater pupil dilation during reappraisal than distraction, but younger adults displayed no difference between conditions-an effect that survived when controlling for gaze patterns. Gaze findings revealed that older adults looked less within images during active emotion regulation compared with passive viewing (no difference between distraction and reappraisal), and younger adults showed no difference across strategies. Younger adults gazed less within the most emotional image areas during distraction, but this did not significantly contribute to pupil response. Our findings support that distraction is less cognitively effortful than reinterpreting negative information in later life. These findings could be explained by older adults' motivational bias to disengage from negative information because of the age-related positivity effect, or compensation for decreased working memory resources across the life span. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Memory, priority encoding, and overcoming high-value proactive interference in younger and older adults.

PubMed

Friedman, Michael C; Castel, Alan D

2013-01-01

It is often necessary to remember important information while directing attention away from encoding less valuable information. To examine how aging influences the ability to control and update the encoding of high-value information, younger and older adults studied six lists of words that varied in terms of the point values associated with each word. The words were paired with the same high and low point values for three study-test cycles, but on the fourth and subsequent cycles the value-word pairings were switched such that the lowest value pairs became the highest values (and vice versa). For the first three study-test cycles, younger adults outperformed older adults in terms of the number of words recalled and overall point totals, but performance was similar in terms of selectively remembering high-value words. When the values were switched, both groups displayed substantial interference from the previous pairings. Although both groups improved with additional study-test cycles, only younger adults were able to fully recover from the interference effects. A similar, and more pronounced, set of results were obtained when positive and negative point values were paired with the words. The findings are interpreted in a value-directed remembering framework, emphasizing the role of benefits and costs of strategic encoding and age-related differences in the effects of interference on memory.

Acute stress disorder in older, middle-aged and younger adults in reaction to the second Lebanon war.

PubMed

Cohen, Miri

2008-01-01

To compare rate of acute stress disorder (ASD) and intensity of acute stress symptoms (ASS) in younger, middle-aged and older Israeli citizens exposed to missile attacks during the second Lebanon war. A telephone survey of a random sample of residents in the northern area of Israel was conducted in July 2006, during the third week of Lebanon war. Respondents were divided into groups aged 18-40, 41-69 and 70+. ASD and ASS were measured by the Acute Stress Interview questionnaire and by war-related exposure variables and demographic data. Exposure variables were similar in the three age groups. Older respondents reported lower intensity of ASS and obtained lower means for each of the symptoms criteria than the young adults, while the middle-aged adults were in between the younger and the older group. ASD criteria were met by 13.2% of the younger, 4.7% of middle-aged and 4.3% of older respondents (p > 0.05), and subsyndromal ASD was found in 20.5%, 14.1% and 4.4% (p < 0.05) respectively. Twenty-two percent of ASS variance was explained by younger age, female gender and higher perceived proximity to missile falling. Older adults reacted to the war situation with lower level of acute stress symptoms. Long-term effects of war on different age groups should be further studied.

Time-for-Money Exchanges between Older and Younger Generations in Swedish Families

ERIC Educational Resources Information Center

Lennartsson, Carin; Silverstein, Merril; Fritzell, Johan

2010-01-01

Despite the maturation of welfare states, family solidarity continues to be strong and a growing body of research has shown that substantial financial transfers are passed from older to younger generations within the family. At the same time, family solidarity in terms of instrumental and social support is found to be mutual. This study examines…

Physicians' response to sexual dysfunction presented by a younger vs. An older adult.

PubMed

Gewirtz-Meydan, Ateret; Ayalon, Liat

2017-12-01

The aim of this study is to determine whether physicians have an age bias regarding sexual dysfunction presented by older vs. younger patients in terms of attributed diagnosis, etiology, proposed treatment and perceived prognosis. An on-line survey consisting of one of two, randomly administered, case vignettes, which differed only by the age of the patient (28 or 78). In both cases, the patient was described as suffering from occasional erectile dysfunction with a clear psychosocial indication. A total of 236 physicians responded to the survey. Overall, 110 physicians received an "old" vignette and 126 physicians received a "young" vignette. Even though both cases presented with a clear psychosocial etiology, the "older" vignette was more likely to be diagnosed with erectile dysfunction whereas the "younger" vignette was more likely to be diagnosed with performance anxiety. The "older" vignette's dysfunction was more likely to be attributed to hormonal changes, health problems and decreased sexual desire. Physicians were more likely to recommend testosterone replacement therapy (TRT) and PDE5 inhibitors (PDE5i; such as Sildenafil; Vardenafil; Tadalafil) as well as a referral to urology to the "older" vignette. In contrast, the "younger" vignette was more often referred to a sexologist and received a more positive prognosis than the older patient. This study demonstrates an age bias among physicians regarding sexuality in later life. Of particular note is the tendency to prescribe PDE5i to the older patient, despite the clear psychosocial indication presented in the case vignette. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Street crossing behavior in younger and older pedestrians: an eye- and head-tracking study.

PubMed

Zito, G A; Cazzoli, D; Scheffler, L; Jäger, M; Müri, R M; Mosimann, U P; Nyffeler, T; Mast, F W; Nef, T

2015-12-29

Crossing a street can be a very difficult task for older pedestrians. With increased age and potential cognitive decline, older people take the decision to cross a street primarily based on vehicles' distance, and not on their speed. Furthermore, older pedestrians tend to overestimate their own walking speed, and could not adapt it according to the traffic conditions. Pedestrians' behavior is often tested using virtual reality. Virtual reality presents the advantage of being safe, cost-effective, and allows using standardized test conditions. This paper describes an observational study with older and younger adults. Street crossing behavior was investigated in 18 healthy, younger and 18 older subjects by using a virtual reality setting. The aim of the study was to measure behavioral data (such as eye and head movements) and to assess how the two age groups differ in terms of number of safe street crossings, virtual crashes, and missed street crossing opportunities. Street crossing behavior, eye and head movements, in older and younger subjects, were compared with non-parametric tests. The results showed that younger pedestrians behaved in a more secure manner while crossing a street, as compared to older people. The eye and head movements analysis revealed that older people looked more at the ground and less at the other side of the street to cross. The less secure behavior in street crossing found in older pedestrians could be explained by their reduced cognitive and visual abilities, which, in turn, resulted in difficulties in the decision-making process, especially under time pressure. Decisions to cross a street are based on the distance of the oncoming cars, rather than their speed, for both groups. Older pedestrians look more at their feet, probably because of their need of more time to plan precise stepping movement and, in turn, pay less attention to the traffic. This might help to set up guidelines for improving senior pedestrians' safety, in terms of

Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins

NASA Astrophysics Data System (ADS)

Cronin, Thomas M.; O'Regan, Matt; Pearce, Christof; Gemery, Laura; Toomey, Michael; Semiletov, Igor; Jakobsson, Martin

2017-09-01

Deglacial (12.8-10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-MC1 (4-MC1), and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20-GC1). Cores 4-PC1 and 20-GC were taken at 120 and 115 m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM; ˜ 24 kiloannum or ka) minimum sea level of ˜ 125-130 meters below sea level (m b.s.l.). Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1) followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal) period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka ( ˜ 400 cm of core depth) is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108 m b.s.l. at the 4-PC1 site and 102 m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42-47 m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geographical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas.

Arctic sea ice variability during the last deglaciation: a biomarker approach

NASA Astrophysics Data System (ADS)

Müller, J.; Stein, R. H.

2014-12-01

The last transition from full glacial to current interglacial conditions was accompanied by distinct short-term climate fluctuations caused by changes in the global ocean circulation system. Most palaeoceanographic studies focus on the documentation of the behaviour of the Atlantic Meridional Overturning Circulation (AMOC) during the last deglaciation in response to freshwater forcing events. In this respect, the role of Arctic sea ice remained relatively unconsidered - primarily because of the difficulty of its reconstruction. Here we present new proxy data on late glacial (including the Last Glacial Maximum; LGM) and deglacial sea ice variability in the Arctic Ocean and its main gateway - the Fram Strait - and how these changes in sea ice coverage contributed to AMOC perturbations observed during Heinrich Event 1 and the Younger Dryas. Recurrent short-term advances and retreats of sea ice in Fram Strait, prior and during the LGM, are in line with a variable (or intermittent) North Atlantic heat flow along the eastern corridor of the Nordic Seas. Possibly in direct response to the initial freshwater discharge from melting continental ice-sheets, a permanent sea ice cover established only at about 19 ka BP (i.e. post-LGM) and lasted until 17.6 ka BP, when an abrupt break-up of this thick ice cover and a sudden discharge of huge amounts of sea ice and icebergs through Fram Strait coincided with the weakening of the AMOC during Heinrich Event 1. Similarly, another sea ice maximum at about 12.8 ka BP is associated with the slowdown of the AMOC during the Younger Dryas. The new data sets clearly highlight the important role of Arctic sea ice for the re-organisation of the oceanographic setting in the North Atlantic during the last deglaciation. Further studies and sensitivity experiments to identify crucial driving (and feedback) mechanisms within the High Latitude ice-ocean-atmosphere system will contribute the understanding of rapid climate changes.

Vegetation and Climate Change during the Last Deglaciation in the Great Khingan Mountain, Northeastern China

PubMed Central

Wu, Jing; Liu, Qiang; Wang, Luo; Chu, Guo-qiang; Liu, Jia-qi

2016-01-01

The Great Khingan Mountain range, Northeast China, is located on the northern limit of modern East Asian Summer Monsoon (EASM) and thus highly sensitive to the extension of the EASM from glacial to interglacial modes. Here, we present a high-resolution pollen record covering the last glacial maximum and the early Holocene from a closed crater Lake Moon to reconstruct vegetation history during the glacial-interglacial transition and thus register the evolution of the EASM during the last deglaciation. The vegetation history has gone through distinct changes from subalpine meadow in the last glacial maximum to dry steppe dominated by Artemisia from 20.3 to 17.4 ka BP, subalpine meadow dominated by Cyperaceae and Artemisia between 17.4 and 14.4 ka BP, and forest steppe dominated by Betula and Artemisia after 14.4 ka BP. The pollen-based temperature index demonstrates a gradual warming trend started at around 20.3 ka BP with interruptions of several brief events. Two cold conditions occurred around at 17.2–16.6 ka BP and 12.8–11.8 ka BP, temporally correlating to the Henrich 1 and the Younger Dryas events respectively, 1and abrupt warming events occurred around at 14.4 ka BP and 11.8 ka BP, probably relevant to the beginning of the Bølling-Allerød stages and the Holocene. The pollen-based moisture proxy shows distinct drought condition during the last glacial maximum (20.3–18.0 ka BP) and the Younger Dryas. The climate history based on pollen record of Lake Moon suggests that the regional temperature variability was coherent with the classical climate in the North Atlantic, implying the dominance of the high latitude processes on the EASM evolution from the Last Glacial Maximum (LGM) to early Holocene. The local humidity variability was influenced by the EASM limitedly before the Bølling-Allerød warming, which is mainly controlled by the summer rainfall due to the EASM front covering the Northeast China after that. PMID:26730966

A Detailed 31,000-Year Record of Climate and Vegetation Change, from the Isotope Geochemistry of Two New Zealand Speleothems

NASA Astrophysics Data System (ADS)

Hellstrom, John; McCulloch, Malcolm; Stone, John

1998-09-01

Uranium-series dating and stable isotope analyses of two speleothems from northwest Nelson, New Zealand, record changes in regional climate and local forest extent over the past 31,000 years. Oxygen isotope variation in these speleothems primarily represents changes in the meteoric waters falling above the caves, possibly responding to latitudinal changes in the position of the Subtropical Front in the Tasman Sea. Seven positive excursions can be identified in the oxygen isotope record, which coincide with periods of glacier advance, known to be sensitive to northward movement of the Subtropical Front. Four glacier advances occurred during oxygen isotope stage 2, with the most extreme glacial conditions centered on 19,000 cal yr B.P. 2An excursion in the oxygen isotope record from 13,800 to 11,700 cal yr B.P. provides support for a previously identified New Zealand glacier advance at the time of the Younger Dryas Stade, but suggests it began slightly before the Younger Dryas as recorded in Greenland ice cores. Carbon isotope variations in the speleothems record changes in forest productivity, closely matching existing paleovegetation records. On the basis of vegetation changes, stage 2 glacial climate conditions terminated abruptly in central New Zealand, from 15,700 to 14,200 cal yr B.P. Evidence of continuous speleothem growth at one site suggests that depression of the local treeline was limited to 600-700 m below its present altitude, throughout the last 31,000 years. All ages reported or cited in this paper are in calendar years before present, expressed as "cal yr B.P." With the exception of the U-series dates of Williams (1996), all ages cited for events in New Zealand were reported by the sources cited as radiocarbon ages. In this paper, these radiocarbon ages have been corrected to calendar years before present using the 1993 calibration data set of Stuiver and Reimer (1993), or, for ages of greater than 19,000 14C yr B.P., by the addition of 4000 yr, on

Vegetation and Climate Change during the Last Deglaciation in the Great Khingan Mountain, Northeastern China.

PubMed

Wu, Jing; Liu, Qiang; Wang, Luo; Chu, Guo-qiang; Liu, Jia-qi

2016-01-01

The Great Khingan Mountain range, Northeast China, is located on the northern limit of modern East Asian Summer Monsoon (EASM) and thus highly sensitive to the extension of the EASM from glacial to interglacial modes. Here, we present a high-resolution pollen record covering the last glacial maximum and the early Holocene from a closed crater Lake Moon to reconstruct vegetation history during the glacial-interglacial transition and thus register the evolution of the EASM during the last deglaciation. The vegetation history has gone through distinct changes from subalpine meadow in the last glacial maximum to dry steppe dominated by Artemisia from 20.3 to 17.4 ka BP, subalpine meadow dominated by Cyperaceae and Artemisia between 17.4 and 14.4 ka BP, and forest steppe dominated by Betula and Artemisia after 14.4 ka BP. The pollen-based temperature index demonstrates a gradual warming trend started at around 20.3 ka BP with interruptions of several brief events. Two cold conditions occurred around at 17.2-16.6 ka BP and 12.8-11.8 ka BP, temporally correlating to the Henrich 1 and the Younger Dryas events respectively, 1and abrupt warming events occurred around at 14.4 ka BP and 11.8 ka BP, probably relevant to the beginning of the Bølling-Allerød stages and the Holocene. The pollen-based moisture proxy shows distinct drought condition during the last glacial maximum (20.3-18.0 ka BP) and the Younger Dryas. The climate history based on pollen record of Lake Moon suggests that the regional temperature variability was coherent with the classical climate in the North Atlantic, implying the dominance of the high latitude processes on the EASM evolution from the Last Glacial Maximum (LGM) to early Holocene. The local humidity variability was influenced by the EASM limitedly before the Bølling-Allerød warming, which is mainly controlled by the summer rainfall due to the EASM front covering the Northeast China after that.

A ~25 ka Indian Ocean monsoon variability record from the Andaman Sea

USGS Publications Warehouse

Rashid, H.; Flower, B.P.; Poore, R.Z.; Quinn, T.M.

2007-01-01

Recent paleoclimatic work on terrestrial and marine deposits from Asia and the Indian Ocean has indicated abrupt changes in the strength of the Asian monsoon during the last deglaciation. Comparison of marine paleoclimate records that track salinity changes from Asian rivers can help evaluate the coherence of the Indian Ocean monsoon (IOM) with the larger Asian monsoon. Here we present paired Mg/Ca and δ18O data on the planktic foraminifer Globigerinoides ruber (white) from Andaman Sea core RC12-344 that provide records of sea-surface temperature (SST) and δ18O of seawater (δ18Osw) over the past 25,000 years (ka) before present (BP). Age control is based on nine accelerator mass spectrometry (AMS) dates on mixed planktic foraminifera. Mg/Ca-SST data indicate that SST was ∼3 °C cooler during the last glacial maximum (LGM) than the late Holocene. Andaman Sea δ18Osw exhibited higher than present values during the Lateglacial interval ca 19–15 ka BP and briefly during the Younger Dryas ca 12 ka BP. Lower than present δ18Osw values during the BØlling/AllerØd ca 14.5–12.6 ka BP and during the early Holocene ca 10.8–5.5 ka BP are interpreted to indicate lower salinity, reflect some combination of decreased evaporation–precipitation (E–P) over the Andaman Sea and increased Irrawaddy River outflow. Our results are consistent with the suggestion that IOM intensity was stronger than present during the BØlling/AllerØd and early Holocene, and weaker during the late glaciation, Younger Dryas, and the late Holocene. These findings support the hypothesis that rapid climate change during the last deglaciation and Holocene included substantial hydrologic changes in the IOM system that were coherent with the larger Asian monsoon.

Tropical Indo-Pacific hydroclimate response to North Atlantic forcing during the last deglaciation as recorded by a speleothem from Sumatra, Indonesia

NASA Astrophysics Data System (ADS)

Wurtzel, Jennifer B.; Abram, Nerilie J.; Lewis, Sophie C.; Bajo, Petra; Hellstrom, John C.; Troitzsch, Ulrike; Heslop, David

2018-06-01

Abrupt changes in Atlantic Meridional Overturning Circulation are known to have affected the strength of the Indian and Asian Monsoons during glacial and deglacial climate states. However, there is still much uncertainty around the hydroclimate response of the Indo-Pacific Warm Pool (IPWP) region to abrupt climate changes in the North Atlantic. Many studies suggest a mean southward shift in the intertropical convergence zone (ITCZ) in the IPWP region during phases of reduced Atlantic meridional overturning, however, existing proxies have seasonal biases and conflicting responses, making it difficult to determine the true extent of North Atlantic forcing in this climatically important region. Here we present a precisely-dated, high-resolution record of eastern Indian Ocean hydroclimate variability spanning the last 16 ky (thousand years) from δ18O measurements in an aragonite-calcite speleothem from central Sumatra. This represents the western-most speleothem record from the IPWP region. Precipitation arrives year-round at this site, with the majority sourced from the local tropical eastern Indian Ocean and two additional long-range seasonal sources associated with the boreal and austral summer monsoons. The Sumatran speleothem demonstrates a clear deglacial structure that includes 18O enrichment during the Younger Dryas and 18O depletion during the Bølling-Allerød, similar to the pattern seen in speleothems of the Asian and Indian monsoon realms. The speleothem δ18O changes at this site are best explained by changes in rainfall amount and changes in the contributions from different moisture pathways. Reduced rainfall in Sumatra during the Younger Dryas is most likely driven by reductions in moisture transport along the northern or southern monsoon transport pathways to Sumatra. Considered with other regional proxies, the record from Sumatra suggests the response of the IPWP to North Atlantic freshwater forcing is not solely driven by southward shifts of the

Deglacial and Holocene sea-ice variability north of Iceland and response to ocean circulation changes

NASA Astrophysics Data System (ADS)

Xiao, Xiaotong; Zhao, Meixun; Knudsen, Karen Luise; Sha, Longbin; Eiríksson, Jón; Gudmundsdóttir, Esther; Jiang, Hui; Guo, Zhigang

2017-08-01

Sea-ice conditions on the North Icelandic shelf constitute a key component for the study of the climatic gradients between the Arctic and the North Atlantic Oceans at the Polar Front between the cold East Icelandic Current delivering Polar surface water and the relatively warm Irminger Current derived from the North Atlantic Current. The variability of sea ice contributes to heat reduction (albedo) and gas exchange between the ocean and the atmosphere, and further affects the deep-water formation. However, lack of long-term and high-resolution sea-ice records in the region hinders the understanding of palaeoceanographic change mechanisms during the last glacial-interglacial cycle. Here, we present a sea-ice record back to 15 ka (cal. ka BP) based on the sea-ice biomarker IP25, phytoplankton biomarker brassicasterol and terrestrial biomarker long-chain n-alkanols in piston core MD99-2272 from the North Icelandic shelf. During the Bølling/Allerød (14.7-12.9 ka), the North Icelandic shelf was characterized by extensive spring sea-ice cover linked to reduced flow of warm Atlantic Water and dominant Polar water influence, as well as strong meltwater input in the area. This pattern showed an anti-phase relationship with the ice-free/less ice conditions in marginal areas of the eastern Nordic Seas, where the Atlantic Water inflow was strong, and contributed to an enhanced deep-water formation. Prolonged sea-ice cover with occasional occurrence of seasonal sea ice prevailed during the Younger Dryas (12.9-11.7 ka) interrupted by a brief interval of enhanced Irminger Current and deposition of the Vedde Ash, as opposed to abruptly increased sea-ice conditions in the eastern Nordic Seas. The seasonal sea ice decreased gradually from the Younger Dryas to the onset of the Holocene corresponding to increasing insolation. Ice-free conditions and sea surface warming were observed for the Early Holocene, followed by expansion of sea ice during the Mid-Holocene.

Early Holocene humidity patterns in the Iberian Peninsula reconstructed from lake, pollen and speleothem records

NASA Astrophysics Data System (ADS)

Morellón, Mario; Aranbarri, Josu; Moreno, Ana; González-Sampériz, Penélope; Valero-Garcés, Blas L.

2018-02-01

Comparison of selected, well-dated, lacustrine, speleothem and terrestrial pollen records spanning the Holocene onset and the Early Holocene (ca. 11.7-8 cal kyrs BP) in the Iberian Peninsula shows large hydrological fluctuations and landscape changes with a complex regional pattern in timing and intensity. Marine pollen records from Alboran, the Mediterranean and off shore Atlantic sites show a step-wise increase in moisture and forest during this transition. However, available continental records point to two main patterns of spatial and temporal hydrological variability: i) Atlantic-influenced sites located at the northwestern areas (Enol, Sanabria, Lucenza, PRD-4), characterized by a gradual increase in humidity from the end of the Younger Dryas to the Mid Holocene, similarly to most North Atlantic records; and ii) continental and Mediterranean-influenced sites (Laguna Grande, Villarquemado, Fuentillejo, Padul, Estanya, Banyoles, Salines), with prolonged arid conditions of variable temporal extension after the Younger Dryas, followed by an abrupt increase in moisture at 10-9 cal kyrs BP. Different local climate conditions influenced by topography or the variable sensitivity (gradual versus threshold values) of the proxies analyzed in each case are evaluated. Vegetation composition (conifers versus mesothermophilous taxa) and resilience would explain a subdued response of vegetation in central continental areas while in Mediterranean sites, insufficient summer moisture availability could not maintain high lake levels and promote mesophyte forest, in contrast to Atlantic-influenced areas. Comparison with available climate models, Greenland ice cores, North Atlantic marine sequences and continental records from Central and Northern Europe and the whole Mediterranean region underlines the distinctive character of the hydrological changes occurred in inner Iberia throughout the Early Holocene. The persistent arid conditions might be explained by the intensification

Post-glacial variability of sea ice cover, river run-off and biological production in the western Laptev Sea (Arctic Ocean) - A high-resolution biomarker study

NASA Astrophysics Data System (ADS)

Hörner, T.; Stein, R.; Fahl, K.; Birgel, D.

2016-07-01

Multi-proxy biomarker measurements were applied on two sediment cores (PS51/154, PS51/159) to reconstruct sea ice cover (IP25), biological production (brassicasterol, dinosterol) and river run-off (campesterol, β-sitosterol) in the western Laptev Sea over the last ∼17 ka with unprecedented temporal resolution. The absence of IP25 from 17.2 to 15.5 ka, in combination with minimum concentration of phytoplankton biomarkers, suggests that the western Laptev Sea shelf was mostly covered with permanent sea ice. Very minor river run-off and restricted biological production occurred during this cold interval. From ∼16 ka until 7.5 ka, a long-term decrease of terrigenous (riverine) organic matter and a coeval increase of marine organic matter reflect the gradual establishment of fully marine conditions in the western Laptev Sea, caused by the onset of the post-glacial transgression. Intensified river run-off and reduced sea ice cover characterized the time interval between 15.2 and 12.9 ka, including the Bølling/Allerød warm period (14.7-12.9 ka). Prominent peaks of the DIP25 Index coinciding with maximum abundances of subpolar foraminifers, are interpreted as pulses of Atlantic water inflow on the western Laptev Sea shelf. After the warm period, a sudden return to severe sea ice conditions with strongest ice-coverage between 11.9 and 11 ka coincided with the Younger Dryas (12.9-11.6 ka). At the onset of the Younger Dryas, a distinct alteration of the ecosystem (reflected in a distinct drop in terrigenous and phytoplankton biomarkers) was detected. During the last 7 ka, the sea ice proxies reflect a cooling of the Laptev Sea spring/summer season. This cooling trend was superimposed by a short-term variability in sea ice coverage, probably representing Bond cycles (1500 ± 500 ka) that are related to solar activity changes. Hence, atmospheric circulation changes were apparently able to affect the sea ice conditions on the Laptev Sea shelf under modern sea level

Cosmogenic nuclide production within the atmosphere and long period comets

NASA Astrophysics Data System (ADS)

Overholt, Andrew C.

The Earth is constantly bombarded by cosmic rays. These high energy particles collide with target nuclei, producing a shower of secondary particles. These secondaries contribute significantly to the radiation background at sea level and in the atmosphere, as well as producing rare cosmogenic nuclides. This contribution is variable over long time scales as astrophysical events change the cosmic ray flux incident on the Earth. Our work re-examines a previously proposed climate effect of increased cosmic ray flux due to galactic location. Although our work does not support this effect, cosmic ray secondaries remain a threat to terrestrial biota. We calculate the cosmogenic neutron flux within the atmosphere as a function of primary spectrum. This work is pivotal in determining the radiation dose due to any arbitrary astrophysical event where the primary spectrum is known. Additionally, this work can be used to determine the cosmogenic nuclide production from such an event. These neutrons are the fundamental source of cosmogenic nuclides within our atmosphere and extraterrestrial matter. We explore the idea that excursions in 14C and 10Be abundances in the atmosphere may arise from direct deposition by long-period comet impacts, and those in 26Al from any bolide. We find that the amount of nuclide mass on large long-period comets entering the Earth's atmosphere may be sufficient for creating anomalies in the records of 14C and 10Be from past impacts. In particular, the estimated mass of the proposed Younger Dryas comet is consistent with its having deposited sufficient isotopes to account for recorded nuclide increases at that time. The 26Al/10Be ratio is much larger in extraterrestrial objects than in the atmosphere, and so, we note that measuring this ratio in ice cores is a suitable further test for the Younger Dryas impact hypothesis. This portion of our work may be used to find possible impact events in the geologic record as well as determination of a large

The Late Quaternary tephrostratigraphy of annually laminated sediments from Meerfelder Maar, Germany

NASA Astrophysics Data System (ADS)

Lane, Christine S.; Brauer, Achim; Martín-Puertas, Celia; Blockley, Simon P. E.; Smith, Victoria C.; Tomlinson, Emma L.

2015-08-01

The record of Late Quaternary environmental change within the sediments of Meerfelder Maar in the Eifel region of Germany is renowned for its high precision chronology, which is annually laminated throughout the Last Glacial to Interglacial transition (LGIT) and most of the Holocene. Two visible tephra layers are prominent within the floating varve chronology of Meerfelder Maar. An Early Holocene tephra layer, the Ulmener Maar Tephra (∼11,000 varve years BP), provides a tie-line of the Meerfelder Maar record to the varved Holocene record of nearby Lake Holzmaar. The Laacher See Tephra provides another prominent time marker for the late Allerød, ∼200 varve years before the transition into the Younger Dryas at 12,680 varve years BP. Further investigation has now shown that there are also 15 cryptotephra layers within the Meerfelder Maar LGIT-Holocene stratigraphy and these layers hold the potential to make direct comparisons between the Meerfelder Maar record and other palaeoenvironmental archives from across Europe and the North Atlantic. Most notable is the presence of the Vedde Ash, the most widespread Icelandic eruption known from the Late Quaternary, which occurred midway through the Younger Dryas. The Vedde Ash has also been found in the Greenland ice cores and can be used as an isochron around which the GICC05 and Meerfelder Maar annual chronologies can be compared. Near the base of the annual laminations in Meerfelder Maar a cryptotephra is found that correlates to the Neapolitan Yellow Tuff, erupted from Campi Flegrei in southern Italy, 1200 km away. This is the furthest north that the Neapolitan Yellow Tuff has been found, highlighting its importance in the construction of a European-wide tephrostratigraphic framework. The co-location of cryptotephra layers from Italian, Icelandic and Eifel volcanic sources, within such a precise chronological record, makes Meerfelder Maar one of the most important tephrostratotype records for continental Europe during

Pleistocene glacial evolution of Fuentes Carrionas (Cantabrian Range, NW Spain)

NASA Astrophysics Data System (ADS)

Pellitero, Ramon

2014-05-01

Fuentes Carrionas is a massif situated at the N of Spain, between Castilla y Leon and Cantabria regions. It is the second highest mountain massif of the Cantabrian Range after Picos de Europa, with peaks over 2500 m.a.s.l. and valleys well over 1000 m.a.s.l. Fuentes Carrionas was glaciated during Quaternary, and even during the Holocene and as far as Little Ice Age the presence of glaciers, or at least permafrost is controversial. Results from glacial geomorphology analysis of Fuentes Carrionas Massif are presented. Based on the interpretation of glacial landforms, glacial evolution since the Last Glacial Maximum until Pleistocene deglaciation is described. Four different glacial equilibrium phases are identified, the last one divided into two pulsations. Deglaciation process took place between 36 ka BP and 11 ka BP. Local Last Glacial Maximum is dated back to 36-38 ka. BP, therefore earlier than LGM. Glaciers reached 15 km. long and occupied valleys down to 1250 m.a.s.l. during this phase. By European LGM (20-18 ka.BP) glaciers had substantially retreated to fronts about 1700 m.a.s.l. A final stage with two marked pulsations shows only small glaciers located at cirques above 2000 m.a.s.l. and, finally, only small cirque glaciers at North and Northeast orientation above 2200 m.a.s.l. Both these phases have been correlated to Oldest and Younger Dryas, although no dates have been done yet. A palaeoenvironmental reconstruction is proposed, based on ELA (Equilibrium Line Altitude) rise. ELA has been calculated with the AAR method and 0.67 ratio. This reconstruction shows that temperatures ranged between 9°C and 10°C lower than present ones at the end of Pleistocene, depending on a precipitations variation between 30% higher and 20% lower than current ones. Further research will focus on these retreat phases, especially on Younger Dryas identification and reconstruction for this site and the rest of Cantabrian Range.

Digital clock drawing: Differentiating ‘thinking’ versus ‘doing’ in younger and older adults with depression

PubMed Central

Cohen, Jamie; Penney, Dana L.; Davis, Randall; Libon, David J.; Swenson, Rodney A.; Ajilore, Olusola; Kumar, Anand; Lamar, Melissa

2015-01-01

Objective Psychomotor slowing has been documented in depression. The digital Clock Drawing Test (dCDT) provides: i) a novel technique to assess both cognitive and motor aspects of psychomotor speed within the same task and ii) the potential to uncover subtleties of behavior not previously detected with non-digitized modes of data collection. Method Using digitized pen technology in 106 participants grouped by Age (younger/older) and Affect (euthymic/unmedicated depressed), we recorded cognitive and motor output by capturing how the clock is drawn rather than focusing on the final product. We divided time to completion (TTC) for Command and Copy conditions of the dCDT into metrics of percent of drawing (%Ink) versus non-drawing (%Think) time. We also obtained composite z-scores of cognition, including attention/ information processing (AIP), to explore associations of %Ink and %Think times to cognitive and motor performance. Results Despite equivalent TTC, %Ink and %Think Command times (Copy n.s.) were significant (AgeXAffect interaction:p=.03)—younger depressed spent a smaller proportion of time drawing relative to thinking compared to the older depressed group. Command %Think time negatively correlated with AIP in the older depressed group (r=−.46;p=.02). Copy %Think time negatively correlated with AIP in the younger depressed (r=−.47;p=.03) and older euthymic groups (r=−.51;p=.01). Conclusion The dCDT differentiated aspects of psychomotor slowing in depression regardless of age, while dCDT/cognitive associates for younger adults with depression mimicked patterns of older euthymics. PMID:25222513

Self-confidence in financial analysis: a study of younger and older male professional analysts.

PubMed

Webster, R L; Ellis, T S

2001-06-01

Measures of reported self-confidence in performing financial analysis by 59 professional male analysts, 31 born between 1946 and 1964 and 28 born between 1965 and 1976, were investigated and reported. Self-confidence in one's ability is important in the securities industry because it affects recommendations and decisions to buy, sell, and hold securities. The respondents analyzed a set of multiyear corporate financial statements and reported their self-confidence in six separate financial areas. Data from the 59 male financial analysts were tallied and analyzed using both univariate and multivariate statistical tests. Rated self-confidence was not significantly different for the younger and the older men. These results are not consistent with a similar prior study of female analysts in which younger women showed significantly higher self-confidence than older women.

Feelings towards Older vs. Younger Adults: Results from the European Social Survey

ERIC Educational Resources Information Center

Ayalon, Liat

2013-01-01

The study evaluated the association of modernization (at the macro/societal-level) and modernity (at the micro/individual-level) with feelings towards older vs. younger adults. Analysis was based on the fourth wave of the European Social Survey, which includes a rotated module on ageism. The sample consisted of 28 countries and a total of 54,988…

Movement Skills of Younger versus Older Adults with and without Down Syndrome

ERIC Educational Resources Information Center

Carmeli, Eli; Ariav, Claudette; Bar-Yossef, Tamar; Levy, Ran; Imam, Bita

2012-01-01

Adults with Down syndrome (DS) are often physically inactive, which may accelerate the onset of disease and aging symptoms. Eight older persons with DS (aged 54-61), and 10 younger persons with DS (aged 26-35) living in a residential care center were examined. Eighteen age- and gender-matched individuals without DS served as control groups.…

Respiratory and Laryngeal Changes with Vocal Loading in Younger and Older Individuals

ERIC Educational Resources Information Center

Sundarrajan, Anusha; Huber, Jessica E.; Sivasankar, M. Preeti

2017-01-01

Purpose: The objective of the current study was to investigate the effects of age and vocal loading on the respiratory and laryngeal systems. Method: Fourteen younger (M = 20 years) and 13 older (M = 75 years) healthy individuals participated in a 40-min vocal loading challenge in the presence of 70-dB background noise. Respiratory kinematic and…

Emotional expressivity in older and younger adults' descriptions of personal memories.

PubMed

Schryer, Emily; Ross, Michael; St Jacques, Peggy; Levine, Brian; Fernandes, Myra

2012-01-01

BACKGROUND/STUDY CONTEXT: According to the socioemotional selectivity theory (SST; Mather & Carstensen, 2003, Psychological Sciences, 14, 409-415), aging is associated with greater motivation to regulate emotions. The authors propose that the language people use to describe personal memories provides an index of age differences in emotional self-regulation. In the present article, the authors reanalyzed three previously published studies in which older (aged 60-88) and younger (aged 17-33) participants described emotional and neutral memories from their recent and distant pasts. The authors analyzed the language of the memories using Pennebaker, Booth, and Francis's (2007) Linguistic Inquiry Word Count program (Austin, TX: LIWC Inc.), which calculates the percentage of positive and negative emotion words. In Studies 1 and 2, older adults used more positive emotion words than did younger adults to describe their autobiographical memories from the recent past, particularly when these were of a neutral valence. In Study 3, older adults used more positive emotion words when describing more recent memories (from the past 5 years) but not when describing distant childhood or adolescent memories. The authors suggest that these age differences in emotional expressivity support SST, and represent an as-yet unreported age difference that may stem from differences in motivation to regulate emotion.

Influence of refractive condition on retinal vasculature complexity in younger subjects.

PubMed

Azemin, Mohd Zulfaezal Che; Daud, Norsyazwani Mohamad; Ab Hamid, Fadilah; Zahari, Ilyanoon; Sapuan, Abdul Halim

2014-01-01

The aim of this study was to compare the retinal vasculature complexity between emmetropia, and myopia in younger subjects. A total of 82 patients (24.12 ± 1.25 years) with two types of refractive conditions, myopia and emmetropia were enrolled in this study. Refraction data were converted to spherical equivalent refraction. These retinal images (right eyes) were obtained from NAVIS Lite Image Filing System and the vasculature complexity was measured by fractal dimension (D f ), quantified using a computer software following a standardized protocol. There was a significant difference (P < 0.05) in the value of D f between emmetropic (1.5666 ± 0.0160) and myopic (1.5588 ± 0.0142) groups. A positive correlation (rho = 0.260, P < 0.05) between the D f and the spherical equivalent refraction was detected in this study. Using a linear model, it was estimated that 6.7% of the variation in D f could be explained by spherical equivalent refraction. This study provides valuable findings about the effect of moderate to high myopia on the fractal dimension of the retinal vasculature network. These results show that myopic refraction in younger subjects was associated with a decrease in D f , suggesting a loss of retinal vessel density with moderate to high myopia.

Risk of Secondary Injury in Younger Athletes After Anterior Cruciate Ligament Reconstruction

PubMed Central

Wiggins, Amelia J.; Grandhi, Ravi K.; Schneider, Daniel K.; Stanfield, Denver; Webster, Kate E.; Myer, Gregory D.

2017-01-01

Background Injury to the ipsilateral graft used for reconstruction of the anterior cruciate ligament (ACL) or a new injury to the contralateral ACL are disastrous outcomes after successful ACL reconstruction (ACLR), rehabilitation, and return to activity. Studies reporting ACL reinjury rates in younger active populations are emerging in the literature, but these data have not yet been comprehensively synthesized. Purpose To provide a current review of the literature to evaluate age and activity level as the primary risk factors in reinjury after ACLR. Study Design Systematic review and meta-analysis. Methods A systematic review of the literature was conducted via searches in PubMed (1966 to July 2015) and EBSCO host (CINAHL, Medline, SPORTDiscus [1987 to July 2015]). After the search and consultation with experts and rating of study quality, 19 articles met inclusion for review and aggregation. Population demographic data and total reinjury (ipsilateral and contralateral) rate data were recorded from each individual study and combined using random-effects meta-analyses. Separate meta-analyses were conducted for the total population data as well as the following subsets: young age, return to sport, and young age + return to sport. Results Overall, the total second ACL reinjury rate was 15%, with an ipsilateral reinjury rate of 7% and contralateral injury rate of 8%. The secondary ACL injury rate (ipsilateral + contralateral) for patients younger than 25 years was 21%. The secondary ACL injury rate for athletes who return to a sport was also 20%. Combining these risk factors, athletes younger than 25 years who return to sport have a secondary ACL injury rate of 23%. Conclusion This systematic review and meta-analysis demonstrates that younger age and a return to high level of activity are salient factors associated with secondary ACL injury. These combined data indicate that nearly 1 in 4 young athletic patients who sustain an ACL injury and return to high-risk sport

Testing enhances subsequent learning in older but not in younger elementary school children.

PubMed

Aslan, Alp; Bäuml, Karl-Heinz T

2016-11-01

In adults, testing can enhance subsequent learning by reducing interference from the tested information. Here, we examined this forward effect of testing in children. Younger and older elementary school children and adult controls studied four lists of items in anticipation of a final cumulative recall test. Following presentation of each of the first three lists, participants were immediately tested on the respective list, or the list was re-presented for additional study. Results revealed that, compared to additional study, immediate testing of Lists 1-3 enhanced memory for the subsequently studied List 4 in adults and older elementary school children, but not in younger elementary school children. The findings indicate that the forward effect of testing is a relatively late-maturing phenomenon that develops over middle childhood and is still inefficient in the early elementary school years. Together with the results of other recent studies, these findings point to a more general problem in young children in combating interference. © 2015 John Wiley & Sons Ltd.

[Rheumatic cardiopathy in children younger than 6 years of age].

PubMed

Vázquez-Antona, C; Calderón-Colmenero, J; Attié, F; Zabal, C; Buendía-Hernández, A; Díaz-Medina, L H; Bialkowski, J; García Arenal, F

1991-01-01

Most of the published papers on Rheumatic Fever (RF) have not included the younger population. We selected 211 cases of children with RF younger than 6 years of age from 9,471 clinical files from 1944 to 1982. These were followed retrospectively to identify the presence of rheumatic activity, subsequent attacks and penicillin profilaxis. From de 211 cases, 209 had carditis; 57% of them were girls and 43% boys. There were no previous infections of the upper respiratory tract in 36% of the patients. The number of cases with RF increased abruptly after 3 years of age and continued increasing until 5 years of age when 70.5% of the population had there first clinically recognized attack. Lesions were present in the mitral valve in 80% of the cases, in the aortic valve in 12%, in the tricuspid in 5% and in the pulmonary valve in 3%. The death rate during the first attack was 20% being refractory heart failure the main cause of death. Thirteen cases suffered rheumatic pneumonia, 9 of whom died (69.2%). 1) The incidence of acute rheumatic fever in children under 6 years of age has decreased with time. 2) The death rate as well as the valvular damage decreased with the parents cooperation with the treatment. 3) The changes in the clinical picture and the severity of valve sequelea may be due to penicillin profilaxis and the better understanding of the disease.

Paleolimnology of Lake Ontario: AN Assessment of Glacial Meltwater Influx

NASA Astrophysics Data System (ADS)

Hladyniuk, R.; Longstaffe, F. J.

2010-12-01

The timing and extent of glacial meltwater outbursts from the Laurentide Ice Sheet (LIS) may provide insight into their potential role in initiating and/or sustaining the Younger Dryas (YD) cooling event. It has been previously proposed that meltwater from the LIS suppressed thermohaline circulation in the Atlantic Ocean, leading to an abrupt change in climate (Broecker et al. 1989). Several pathways for transport of glacial meltwater to the Atlantic Ocean have been suggested in the past, including eastern flow through the St. Lawrence River system and discharge into the Arctic Ocean via a northwestern outlet (Murton et al. 2010). Glacial meltwater contributions to Lake Ontario and its ancient equivalents during the last ~14,000 cal BP have been evaluated using the oxygen-isotope compositions of ostracode shells from three sediment cores in Lake Ontario. Glacial Lake Iroquois (~12,500 cal BP) δ18O values as low as -18‰ suggest significant contribution of glacial meltwater runoff from the LIS. This glacial sediment is characterized by occasional grains of sand and gravel. These ice-rafted particles indicate how far icebergs floated and suggest close proximity to the LIS. Early Lake Ontario sediment (~12,000 cal BP) exhibits thicker laminations, suggestive of increased winter ice cover and perhaps a colder climate, and is characterized by slightly lower δ18O values (-19.5‰). The end of glacial-dominated sedimentation at ~11,800 cal BP is demarcated by a significant increase in lakewater δ18O values (-12.0‰), reflecting mixing between regional precipitation in the watershed and upstream inflow into Lake Ontario. At ~10,800 cal BP, the δ18O value of Lake Ontario decreased to ~-15‰. This change reflects the main Algonquin highstand in Lake Huron, which flooded into Lake Ontario from both the Fenelon Falls and Port Huron outlets at this time. Shortly thereafter, the opening of the North Bay outlet and isostatic rebound at the Port Huron outlet limited

Diatoms as paleoecological indicators of environmental change in the Lake Czechowskie catchments ecosystem (Northern Tuchola Pinewoods, Poland)

NASA Astrophysics Data System (ADS)

Rzodkiewicz, Monika; Zawiska, Izabela; Noryśkiewicz, Agnieszka Maria; Obremska, Milena; Ott, Florian; Kramkowski, Mateusz; Słowiński, Michał; Błaszkiewicz, Mirosław; Brauer, Achim

2016-04-01

In this study we investigated four cores of biogenic sediments from the lakes located in close vicinity. Three cores are situated along a transect in the Lake Czechowskie basin from its deepest point towards a former lake bay. The fourth sediment core was retrieved from the nearby Trzechowskie paleolake. Lake Czechowskie is located in the northern part of the Tuchola Pinewoods District (Northern Poland) in a young glacial landscape. At present, the majority of the area is forested or used for agriculture. The main focus was of the study was Late Glacial and early Holocene period. We performed diatom, Cladocera and pollen analyses, the chronology was established by varve counting, confirmed by AMS 14C dating and Laacher See Tephra (Wulf et. all 2013). In this study we focused on the results of diatom analyses. Diatom assemblages are integrated indicators of environmental change because their distributions are closely linked to water quality parameters including such as nutrient availability. At the beginning of Allerød there are more eutrophic diatom taxa such as Staurosira construens, Pseudostaurosira brevistriata, Staurosira pinnata. These species are widely distributed in the littoral mainly freshwater, many of which are species of epiphytic, preferring water rich in nutrients. At the end of the Allerød we observe significant changes within diatom assemblages. The increase of planktonic Cyclotella comensis together with the decrease of benthic Stauroseria construens indicate the shortening of time with ice cove on the lake and longer time with summer stratification. In the Younger Dryas cooling we can see the increase of the abundance of diatom Staurosira construens which indicate cold spring and late ice-out (Bradbury et al., 2002). At the early Holocene planktonic diatoms increase in particular Cyclotella comensis, Punciculata radiosa and Cyclotella praetermissa. Some of Aulacoseira species at the end of Younger Dryas. The Holocene sediments showed no

High resolution water stable isotope profiles of abrupt climate transitions in Greenland ice with new observations from NEEM

NASA Astrophysics Data System (ADS)

Popp, T. J.; White, J. W. C.; Gkinis, V.; Vinther, B. M.; Johnsen, S. J.

2012-04-01

In 1989 Willi Dansgaard and others, using the DYE3 ice core, showed that the abrupt termination of the Younger Dryas expressed in water stable isotope ratios and deuterium excess was completed in less than 50 years. A few years later, using the GISP2 ice core, Richard Alley and others proposed that snow accumulation at the site doubled in as little as 1-3 years across the same climate transition at the end of the Younger Dryas. Over the next two decades, in large part due to such observations from Greenland ice cores, a paradigm of linked, abrupt changes in the North Atlantic region has been developed around North Atlantic deep water formation, North Atlantic sea ice extent, and widespread atmospheric circulation changes occurring repeatedly during the last glacial period in response to changing freshwater fluxes to the region, or perhaps other causes. More recently, with the NGRIP ice core, using a suite of high resolution proxy data, and in particular deuterium excess, it was observed again that certain features in the climate system can switch modes from one year to the next, while other proxies can take from decades to centuries to completely switch modes. Thus, an event seen in the proxy records such as the abrupt end of the Younger Dryas (or other interstadial events) may comprise multiple climatic or oceanic responses with different relative timing and duration which potentially follow a predictable sequence of events, in some cases separated by only a few years. Today, the search continues for these emerging patterns through isotopic and other highly resolvable proxy data series from ice cores. With the recent completion of the drilling at NEEM, many abrupt transitions have now been measured in detail over a geographic transect with drilling sites spanning from DYE3 in Southern Greenland, GISP2 in the central summit region, and up to NGRIP and NEEM in the far north. The anatomy of abrupt climate transitions can therefore be examined both spatially and

THA Using Metal-on-Metal Articulation in Active Patients Younger Than 50 Years

PubMed Central

Bonnomet, François; Clavert, Philippe; Laffargue, Philippe; Migaud, Henri

2008-01-01

The main concern of patients with longer life expectancies and of patients who are younger and more active is the longevity of their total hip arthroplasty. We retrospectively reviewed 83 cementless total hip arthroplasties in 73 patients implanted with metal-on-metal articulation. All patients were younger than 50 years old (average age, 41 years) at the time of the index procedure, and 80% of the patients had an activity level graded 4 or 5 when measured with the system of Devane et al. A 28-mm Metasul articulation was used with three different cementless titanium acetabular components. At the most recent followup (average, 7.3 years), the average Merle d’Aubigné-Postel score improved from a preoperative 11.1 points to 17.4 points. We observed no radiographic evidence of component loosening. Ten acetabular components had lucency limited to one zone. The 10-year survivorship with the end point of revision (ie, exchange of at least one prosthetic or bearing component) was 100% (95% confidence interval, 90%–100%). Metasul bearings with cementless acetabular components remain promising in this high-risk younger patient population. However, additional followup strategies are recommended to determine any possible long-term deleterious effects associated with the dissemination of metallic ions. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:18196415

Factors Associated with Contraceptive Use Differ between Younger and Older African-American Female Adolescents.

PubMed

Clarke, Kristie Elizabeth North; Kraft, Joan Marie; Wiener, Jeffrey B; Hatfield-Timajchy, Kendra; Kottke, Melissa; Sales, Jessica M; Goedken, Peggy; Kourtis, Athena P

2016-10-01

To examine differences in factors associated with contraceptive use between younger and older adolescent age groups, which has not previously been well described. Age group-specific analyses were performed on cross-sectional survey data to identify factors associated with any contraceptive use at last sex among younger (14- to 16-year-old) and older (17- to 19-year-old) sexually active African American female adolescents; interaction analyses were used to assess whether these associations differed by age. Adolescent reproductive health clinic in Atlanta, Georgia. Sexually active African American female adolescents 14-19 years of age. No intervention tested; cross-sectional design. Self-reported contraceptive use during most recent vaginal sex with a male partner. The prevalence of contraceptive use at last sex was identical in both groups; however, factors associated with contraceptive use differed according to age. The only factor associated with contraceptive use in both age groups was involvement in decisions about sexual health in the most recent relationship. Associations between factors and contraceptive use significantly differed according to age. History of sexually transmitted infection, age difference with partner, discussion of condoms with partner, and concurrent partners were important factors among younger adolescents; worry about pregnancy and discussion of birth control with partner were important among older adolescents. Factors associated with contraceptive use at last sex differ according to adolescent age; this should be considered when designing counseling and interventions for teens, as well as research. Published by Elsevier Inc.

Does one size fit all? Assessing the preferences of older and younger people for attributes of quality of life.

PubMed

Ratcliffe, Julie; Lancsar, Emily; Flint, Thomas; Kaambwa, Billingsley; Walker, Ruth; Lewin, Gill; Luszcz, Mary; Cameron, Ian D

2017-02-01

To systematically compare, via ranking and best worst tasks, the relative importance of key dimensions of quality of life for younger and older people. A web-based survey was developed for administration to two Australia-wide community-based samples comprising younger people aged 18-64 years and older people aged 65 years and above. Respondents were asked to rank 12 quality of life dimensions. Respondents also completed a successive best worst task using the same 12 quality of life dimensions. The relative importance of the quality of life dimensions differed for younger and older person samples. For older people, the ability to be independent and to have control over their daily lives were particularly important for their overall quality of life whereas for younger people, mental health was considered most important. Many interventions accessed by older people in geriatric medicine and aged care sectors have a broader impact upon quality of life beyond health status. The findings from this study indicate that a focus on broader aspects of quality of life may also be consistent with the preferences of older people themselves as to what constitutes quality of life from their perspective.

Amphetamine modulates brain signal variability and working memory in younger and older adults.

PubMed

Garrett, Douglas D; Nagel, Irene E; Preuschhof, Claudia; Burzynska, Agnieszka Z; Marchner, Janina; Wiegert, Steffen; Jungehülsing, Gerhard J; Nyberg, Lars; Villringer, Arno; Li, Shu-Chen; Heekeren, Hauke R; Bäckman, Lars; Lindenberger, Ulman

2015-06-16

Better-performing younger adults typically express greater brain signal variability relative to older, poorer performers. Mechanisms for age and performance-graded differences in brain dynamics have, however, not yet been uncovered. Given the age-related decline of the dopamine (DA) system in normal cognitive aging, DA neuromodulation is one plausible mechanism. Hence, agents that boost systemic DA [such as d-amphetamine (AMPH)] may help to restore deficient signal variability levels. Furthermore, despite the standard practice of counterbalancing drug session order (AMPH first vs. placebo first), it remains understudied how AMPH may interact with practice effects, possibly influencing whether DA up-regulation is functional. We examined the effects of AMPH on functional-MRI-based blood oxygen level-dependent (BOLD) signal variability (SD(BOLD)) in younger and older adults during a working memory task (letter n-back). Older adults expressed lower brain signal variability at placebo, but met or exceeded young adult SD(BOLD) levels in the presence of AMPH. Drug session order greatly moderated change-change relations between AMPH-driven SD(BOLD) and reaction time means (RT(mean)) and SDs (RT(SD)). Older adults who received AMPH in the first session tended to improve in RT(mean) and RT(SD) when SD(BOLD) was boosted on AMPH, whereas younger and older adults who received AMPH in the second session showed either a performance improvement when SD(BOLD) decreased (for RT(mean)) or no effect at all (for RT(SD)). The present findings support the hypothesis that age differences in brain signal variability reflect aging-induced changes in dopaminergic neuromodulation. The observed interactions among AMPH, age, and session order highlight the state- and practice-dependent neurochemical basis of human brain dynamics.

Amphetamine modulates brain signal variability and working memory in younger and older adults

PubMed Central

Garrett, Douglas D.; Nagel, Irene E.; Preuschhof, Claudia; Burzynska, Agnieszka Z.; Marchner, Janina; Wiegert, Steffen; Jungehülsing, Gerhard J.; Nyberg, Lars; Villringer, Arno; Li, Shu-Chen; Heekeren, Hauke R.; Bäckman, Lars; Lindenberger, Ulman

2015-01-01

Better-performing younger adults typically express greater brain signal variability relative to older, poorer performers. Mechanisms for age and performance-graded differences in brain dynamics have, however, not yet been uncovered. Given the age-related decline of the dopamine (DA) system in normal cognitive aging, DA neuromodulation is one plausible mechanism. Hence, agents that boost systemic DA [such as d-amphetamine (AMPH)] may help to restore deficient signal variability levels. Furthermore, despite the standard practice of counterbalancing drug session order (AMPH first vs. placebo first), it remains understudied how AMPH may interact with practice effects, possibly influencing whether DA up-regulation is functional. We examined the effects of AMPH on functional-MRI–based blood oxygen level-dependent (BOLD) signal variability (SDBOLD) in younger and older adults during a working memory task (letter n-back). Older adults expressed lower brain signal variability at placebo, but met or exceeded young adult SDBOLD levels in the presence of AMPH. Drug session order greatly moderated change–change relations between AMPH-driven SDBOLD and reaction time means (RTmean) and SDs (RTSD). Older adults who received AMPH in the first session tended to improve in RTmean and RTSD when SDBOLD was boosted on AMPH, whereas younger and older adults who received AMPH in the second session showed either a performance improvement when SDBOLD decreased (for RTmean) or no effect at all (for RTSD). The present findings support the hypothesis that age differences in brain signal variability reflect aging-induced changes in dopaminergic neuromodulation. The observed interactions among AMPH, age, and session order highlight the state- and practice-dependent neurochemical basis of human brain dynamics. PMID:26034283

Below-baseline suppression of competitors during interference resolution by younger but not older adults.

PubMed

Healey, M Karl; Ngo, K W Joan; Hasher, Lynn

2014-01-01

Resolving interference from competing memories is a critical factor in efficient memory retrieval, and several accounts of cognitive aging suggest that difficulty resolving interference may underlie memory deficits such as those seen in the elderly. Although many researchers have suggested that the ability to suppress competitors is a key factor in resolving interference, the evidence supporting this claim has been the subject of debate. Here, we present a new paradigm and results demonstrating that for younger adults, a single retrieval attempt is sufficient to suppress competitors to below-baseline levels of accessibility even though the competitors are never explicitly presented. The extent to which individual younger adults suppressed competitors predicted their performance on a memory span task. In a second experiment, older adults showed no evidence of suppression, which supports the theory that older adults' memory deficits are related to impaired suppression.

Whole-Person Impairment in Younger Retired NFL Players: The Orthopaedic Toll of a Professional Football Career.

PubMed

Domb, Benjamin G; Carter, Chris; Finch, Nathan A; Hammarstedt, Jon E; Dunne, Kevin F; Stake, Christine E

2014-05-01

Professional American football is a physically demanding, high-impact sport with an elevated risk of injury. Orthopaedic injuries may impose acute, short-term or cumulative consequences throughout a player's lifetime. Several studies have addressed health and psychosocial concerns of an older, retired population of players in the National Football League (NFL); however, minimal research has examined the orthopaedic toll on younger, retired players. This study reports total whole-person impairment (WPI) percentages in a cohort of younger, retired NFL players who presented for disability evaluations based on the use of standardized American Medical Association (AMA) impairment guidelines. Case series; Level of evidence, 4. During the study period of February 2011 to August 2013, 65 younger retired NFL players presented for impairment evaluations. The mean time between retirement and impairment evaluation was 3.1 years (range, 0.3-16.4 years). A complete history and physical examination was performed on all symptomatic joints. A retrospective chart review was conducted on 100% of presenting players to assess orthopaedic burden. Body-part impairment (BPI) percentage for each affected joint was generated. The impairment data for each extremity were then combined with spine impairment data to create WPI percentage. Player demographics, including age, position, and playing time, were also recorded. The average WPI percentage was 37% (range, 19%-53%). Players participating in >30 games (n = 54) had a higher mean WPI percentage (38%) than those playing in <30 games (31%; n = 11) (P = .004). Players competing in >5 seasons (n = 46) were 2.4 times more likely to have a WPI of at least 37% (P = .007). The most common joints players reported as symptomatic were lumbar (n = 63; 97%) and cervical spine (n = 58; 89%). The mean age at evaluation was 33.5 years (range, 27-42 years), and the mean number of seasons played was 7.5 (range, 3-14 seasons). The mean number of games played

Some new forms of pyemotes (Acarina:pyemotidae) from forest insects, with remarks on polymorphism

Treesearch

Earle A. Cross; John C. Moser; Gisela Rack

1981-01-01

Three new species of Pyemotes, P. giganticus, P. tuberculatus and P. emarginatus are described, as is the male of P. dryas (Vitzthum, 1923). Male P. dryas and both sexes of P. giganticus are polymorphic. A short, general discussion of...

Some new forms of Pysmotes (Acarina: Pyemotidae) from forest insects with remarks on polymorphism

Treesearch

Earle A. Cross; John C. Moser; Gisela Rack

1981-01-01

Three new species of Pyemotes, P. giganticus, P. tuberculatus and P. emarginatus are described, as is the male of P. dryas (Vitzthum, 1923). Male P. dryas and both sexes of P. giganticus are polymorphic. A short, general discussion of...

The Influence of Emotional Material on Encoding and Retrieving Intentions: An ERP Study in Younger and Older Adults

PubMed Central

Hering, Alexandra; Kliegel, Matthias; Bisiacchi, Patrizia S.; Cona, Giorgia

2018-01-01

Prospective memory is a cognitive process that comprises the encoding and maintenance of an intention until the appropriate moment of its retrieval. It is of highly relevance for an independent everyday life, especially in older adults; however, there is ample evidence that prospective memory declines with increasing age. Because most studies have used neutral stimuli, it is still an open question how emotional factors influence age-related differences in prospective remembering. The aim of the study was to investigate the influence of emotional material on prospective memory encoding, monitoring, maintaining, and retrieval in younger and older adults using behavioral and electrophysiological measures. We tested 24 younger adults (M = 26.4 years) and 20 older adults (M = 68.1 years) using a picture one-back task as ongoing activity with an embedded prospective memory instruction. The experimental task consisted of three sessions. In each session, participants had to encode series of images that represented the prospective memory cues for the consecutive block. The images were either of pleasant, unpleasant, or neutral valence. The pictures used in the ongoing task were likewise of pleasant, unpleasant, or neutral valence. Event-related potentials (ERPs) were recorded to assess the neural correlates of intention encoding, maintenance, and self-initiated retrieval. We did not find age differences between younger and older adults on the behavioral level. However, the ERP results revealed an interesting pattern that suggested for both age groups elevated attentional processing of emotional cues during encoding indicated by an elevated LPP for the emotional cues. Additionally, younger adults showed increased activity for unpleasant cues. During the maintenance phase, both age groups engaged in strategic monitoring especially for pleasant cues, which led to enhanced sustained positivity. During retrieval, older adults showed increased activity of ERP components related

The efficacy of problem solving therapy to reduce post stroke emotional distress in younger (18-65) stroke survivors.

PubMed

Chalmers, Charlotte; Leathem, Janet; Bennett, Simon; McNaughton, Harry; Mahawish, Karim

2017-11-26

To investigate the efficacy of problem solving therapy for reducing the emotional distress experienced by younger stroke survivors. A non-randomized waitlist controlled design was used to compare outcome measures for the treatment group and a waitlist control group at baseline and post-waitlist/post-therapy. After the waitlist group received problem solving therapy an analysis was completed on the pooled outcome measures at baseline, post-treatment, and three-month follow-up. Changes on outcome measures between baseline and post-treatment (n = 13) were not significantly different between the two groups, treatment (n = 13), and the waitlist control group (n = 16) (between-subject design). The pooled data (n = 28) indicated that receiving problem solving therapy significantly reduced participants levels of depression and anxiety and increased quality of life levels from baseline to follow up (within-subject design), however, methodological limitations, such as the lack of a control group reduce the validity of this finding. The between-subject results suggest that there was no significant difference between those that received problem solving therapy and a waitlist control group between baseline and post-waitlist/post-therapy. The within-subject design suggests that problem solving therapy may be beneficial for younger stroke survivors when they are given some time to learn and implement the skills into their day to day life. However, additional research with a control group is required to investigate this further. This study provides limited evidence for the provision of support groups for younger stroke survivors post stroke, however, it remains unclear about what type of support this should be. Implications for Rehabilitation Problem solving therapy is no more effective for reducing post stroke distress than a wait-list control group. Problem solving therapy may be perceived as helpful and enjoyable by younger stroke survivors. Younger stroke

Evaluating suggestibility to additive and contradictory misinformation following explicit error detection in younger and older adults.

PubMed

Huff, Mark J; Umanath, Sharda

2018-06-01

In 2 experiments, we assessed age-related suggestibility to additive and contradictory misinformation (i.e., remembering of false details from an external source). After reading a fictional story, participants answered questions containing misleading details that were either additive (misleading details that supplemented an original event) or contradictory (errors that changed original details). On a final test, suggestibility was greater for additive than contradictory misinformation, and older adults endorsed fewer false contradictory details than younger adults. To mitigate suggestibility in Experiment 2, participants were warned about potential errors, instructed to detect errors, or instructed to detect errors after exposure to examples of additive and contradictory details. Again, suggestibility to additive misinformation was greater than contradictory, and older adults endorsed less contradictory misinformation. Only after detection instructions with misinformation examples were younger adults able to reduce contradictory misinformation effects and reduced these effects to the level of older adults. Additive misinformation however, was immune to all warning and detection instructions. Thus, older adults were less susceptible to contradictory misinformation errors, and younger adults could match this misinformation rate when warning/detection instructions were strong. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Ultra-long pharmacokinetic properties of insulin degludec are comparable in elderly subjects and younger adults with type 1 diabetes mellitus.

PubMed

Korsatko, S; Deller, S; Mader, J K; Glettler, K; Koehler, G; Treiber, G; Urschitz, M; Wolf, M; Hastrup, H; Søndergaard, F; Haahr, H; Pieber, T R

2014-01-01

Management of diabetes in elderly subjects is complex and careful management of glucose levels is of particular importance in this population because of an increased risk of diabetes-related complications and hypoglycaemia. The aim of this study was to evaluate the pharmacokinetic and pharmacodynamic properties of insulin degludec (IDeg), a basal insulin with an ultra-long duration of action, in elderly subjects with type 1 diabetes compared with younger adults. This trial was a randomised, double-blind, two-period, crossover trial conducted in a single centre and included both inpatient and outpatient periods. Subjects were men and women aged 18-35 years inclusive (younger adult group) or ≥65 years (elderly group) with type 1 diabetes who received IDeg (0.4 U/kg) via subcutaneous injection in the thigh once-daily for six days. Following 6-day dosing, a 26-hour euglycaemic glucose clamp procedure was conducted to evaluate the steady-state pharmacodynamic effects of IDeg. Blood samples were taken for pharmacokinetic analysis up to 120 h post-dose. Pharmacokinetic endpoints included the total exposure of IDeg, ie the area under the IDeg serum concentration curve during one dosing interval at steady state (AUC(IDeg,τ,SS)) (τ = 0-24 h, equal to one dosing interval) and the maximum IDeg serum concentration at steady state (C(max,IDeg,SS)). Pharmacodynamic endpoints included the total glucose-lowering effect of IDeg, ie the area under the glucose infusion rate (GIR) curve at steady state (AUC(GIR,τ,SS)), and the maximum GIR at steady state (GIR(max,IDeg,SS)). Total exposure (AUC(IDeg,τ,SS)) and maximum concentration (C(max,IDeg,SS)) of IDeg were comparable between elderly subjects and younger adults. Estimated mean age group ratios (elderly/younger adult) for AUC(IDeg,τ,SS) and C(max,IDeg,SS) and corresponding two-sided 95 % confidence intervals (CIs) were 1.04 (95 % CI 0.73-1.47) and 1.02 (95 % CI 0.74-1.39), respectively. Mean AUC(IDeg,0-12h

Inconsistency in serial choice decision and motor reaction times dissociate in younger and older adults.

PubMed

Bunce, David; MacDonald, Stuart W S; Hultsch, David F

2004-12-01

Intraindividual variability (inconsistency) in reaction time (RT) latencies was investigated in a group of younger (M=25.46 years) and older (M=69.29 years) men. Both groups performed 300 trials in 2-, 4-, and 8-choice RT conditions where RTs for decision and motor components of the task were recorded separately. A dissociation was evident in that inconsistency was greater in older adults for decision RTs when task demands relating to the number of choices and fatigue arising from time-on-task were high. For younger persons, a weak trend toward greater inconsistency in motor RTs was evident. The results are consistent with accounts suggesting that inconsistency in neurobiological mechanisms increases with age, and that attentional lapses or fluctuations in executive control contribute to RT inconsistency.

Thirst for Knowledge: The Effects of Curiosity and Interest on Memory in Younger and Older Adults

PubMed Central

McGillivray, Shannon; Murayama, Kou; Castel, Alan D.

2015-01-01

Given age-related memory impairments, one’s level of curiosity or interest could enhance memory for certain information. In the current study, younger and older adults read trivia questions, rated how curious they were to learn each answer, provided confidence and interest ratings, and judgments of learning (JOL) after learning the answer. No age-related differences in memory were found. Analyses indicated that curiosity and interest contributed to the formation of JOLs. Additionally, interest had a unique increasing relationship with older, but not younger, adults’ memory performance after a week. The results suggest that subjective interest may serve to enhance older adults’ memory. PMID:26479013

Thirst for knowledge: The effects of curiosity and interest on memory in younger and older adults.

PubMed

McGillivray, Shannon; Murayama, Kou; Castel, Alan D

2015-12-01

Given age-related memory impairments, one's level of curiosity or interest could enhance memory for certain information. In the current study, younger and older adults read trivia questions, rated how curious they were to learn each answer, provided confidence and interest ratings, and judgments of learning after learning the answer. No age-related differences in memory were found. Analyses indicated that curiosity and interest contributed to the formation of judgments of learning. Additionally, interest had a unique increasing relationship with older, but not younger, adults' memory performance after a one-week delay. The results suggest that subjective interest may serve to enhance older adults' memory. (c) 2015 APA, all rights reserved).

The Effect of Stimulus Valence on Lexical Retrieval in Younger and Older Adults

ERIC Educational Resources Information Center

Blackett, Deena Schwen; Harnish, Stacy M.; Lundine, Jennifer P.; Zezinka, Alexandra; Healy, Eric W.

2017-01-01

Purpose: Although there is evidence that emotional valence of stimuli impacts lexical processes, there is limited work investigating its specific impact on lexical retrieval. The current study aimed to determine the degree to which emotional valence of pictured stimuli impacts naming latencies in healthy younger and older adults. Method: Eighteen…

Contrasting outcomes of older versus middle-aged and younger adult chemical dependency patients in a managed care program.

PubMed

Satre, Derek D; Mertens, Jennifer; Areán, Patricia A; Weisner, Constance

2003-07-01

This study examined how well older chemical dependency patients succeed in treatment relative to middle-aged and younger patients in a mixed-age private HMO outpatient program. To predict successful outcome, we tested a model incorporating age group differences in individual, treatment and extratreatment factors. The sample included 89 patients aged 55 and over, 379 patients aged 40 to 54, and 736 patients aged 18-39 (N = 1,204). Baseline measures included DSM-IV substance misuse diagnoses, Addiction Severity Index (ASI), psychiatric symptom checklist, sources of suggestion to enter treatment, treatment history and motivation. Outcome measures were abstinence rates and ASI score 6 months posttreatment. At baseline, older adults showed higher levels of alcohol dependence, lower rates of drug dependence and lower psychiatric symptoms relative to younger individuals. Source of suggestions to enter treatment differed by age. Older and middle-aged patients were more likely to have an abstinence goal and to stay in treatment longer than younger adults. At 6 months posttreatment, 55% of older adults reported abstinence in the preceding 30 days, versus 59% of middle-aged adults and 50% of younger adults (p = .035). Lower rates of dependence and hostility, and greater abstinence motivation and length of stay in treatment--all of which were associated with greater age--positively affect prognosis of older adults in treatment.

Exploring the experience of episodic past, future, and counterfactual thinking in younger and older adults: A study of a Colombian sample.

PubMed

De Brigard, Felipe; Rodriguez, Diana Carolina; Montañés, Patricia

2017-05-01

Although extant evidence suggests that many neural and cognitive mechanisms underlying episodic past, future, and counterfactual thinking overlap, recent results have uncovered differences among these three processes. However, the extent to which there may be age-related differences in the phenomenological characteristics associated with episodic past, future and counterfactual thinking remains unclear. This study used adapted versions of the Memory Characteristics Questionnaire and the Autobiographical Interview in younger and older adults to investigate the subjective experience of episodic past, future and counterfactual thinking. The results suggest that, across all conditions, younger adults generated more internal details than older adults. However, older adults generated more external details for episodic future and counterfactual thinking than younger adults. Additionally, younger and older adults generated more internal details, and gave higher sensory and contextual ratings, for memories rather than future and counterfactual thoughts. Methodological and theoretical consequences for extant theories of mental simulation are discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

A transversal pilot study of oropharyngeal carriage of Kingella kingae in healthy children younger than 6 months.

PubMed

Spyropoulou, Vasiliki; Brändle, Gabriel; Maggio, Albane Bertha Rosa; Anderson Della Llana, Rebecca; Cherkaoui, Abdessalam; Renzi, Gesuele; Schrenzel, Jacques; Manzano, Sergio; Ceroni, Dimitri

2017-12-01

The aim of this pilot study was to investigate the extent of oropharyngeal Kingella kingae carriage during the first 6 months of life. We conducted a monocentric transversal pilot study on healthy children younger than 6 months in order to define the oropharyngeal carriage rate. Participants were recruited between December 2013 and September 2015 among children without symptoms or signs of invasive infections. We demonstrated an oropharyngeal carriage rate of 0.67% in children younger than 6 months. Due to the really low carriage rate, it was not possible to draw statistically significant conclusion about any other characteristic of our population. The present study suggests that the oropharyngeal carriage of Kingella kingae among a Swiss population of healthy infants younger than 6 months is exceptional. The scarcity of colonization and disease in the early months of life suggests thus that defense against mucosal carriage and invasive infection is above all provided by vertically acquired immunity. Limited exposure of the neonates due to limited social contacts may also represent another factor avoiding neonates' mucosal Kingella kingae carriage.

Testing Enhances Subsequent Learning in Older but Not in Younger Elementary School Children

ERIC Educational Resources Information Center

Aslan, Alp; Bäuml, Karl-Heinz T.

2016-01-01

In adults, testing can enhance subsequent learning by reducing interference from the tested information. Here, we examined this forward effect of testing in children. Younger and older elementary school children and adult controls studied four lists of items in anticipation of a final cumulative recall test. Following presentation of each of the…

Temporo-spatial gait parameters during street crossing conditions: a comparison between younger and older adults.

PubMed

Vieira, Edgar R; Lim, Hyun-Hwa; Brunt, Denis; Hallal, Camilla Z; Kinsey, Laura; Errington, Lisa; Gonçalves, Mauro

2015-02-01

Most traffic accidents involving pedestrians happen during street crossing. Safe street crossing by older adults requires complex planning and imposes high cognitive demands. Understanding how street crossing situations affect younger and older adults' gait is important to create evidence-based policies, education and training. The objective of this study was to develop and test a method to evaluate temporo-spatial gait parameters of younger and older adults during simulated street crossing situations. Twenty-two younger (25±2 years old) and 22 older adults (73±6 years old) who lived independently in the community completed 3 walking trials at preferred gait speed and during simulated street crossing with regular and with reduced time. There were significant differences between groups (p<0.001) and conditions (p<0.001). Older adults' street crossing walking speed was higher than their preferred speed (p<0.001). Gait during simulated street crossing resulted in significant and progressive gait changes. The methods developed and tested can be used to (1) evaluate if people are at risk of falls and accidents during street crossing situations, (2) to compare among different groups, and (3) to help establish appropriate times for older pedestrians to cross streets safely. The current time to cross streets is too short even for healthy older adults. Copyright © 2014 Elsevier B.V. All rights reserved.

EXPLAINING THE GAP IN ANTENATAL CARE SERVICE UTILIZATION BETWEEN YOUNGER AND OLDER MOTHERS IN GHANA.

PubMed

Boamah, Sheila A; Amoyaw, Jonathan; Luginaah, Isaac

2016-05-01

Over two-thirds of pregnant women (69%) have at least one antenatal care (ANC) coverage contact in sub-Saharan Africa. However, to achieve the full life-saving potential that ANC promises for women and babies, a nuanced understanding of age-specific gaps in utilization of ANC services is required. Using the 2008 Ghana Demographic and Health Survey of 1456 individuals, this study examined the disparities in the use of ANC services between younger and older mothers by applying four counterfactual decomposition techniques. The results show that cross-group differences in the explanatory variables largely account for the differentials in ANC service utilization between younger and older mothers. Birth order (parity) accounts for the largest share of the contribution to the overall explained gap in ANC utilization between the younger and older mothers, suggesting that ANC differentials between the two groups are probably due to biosocial factors. To a lesser extent, wealth status of the two groups also contributes to the overall explained gap in ANC service utilization. The policy implications of these findings are that in order to bridge the ANC service utilization gap between the two groups, policymakers must systematically address gaps in cross-group differences in the explanatory variables in order to increase the utilization of ANC to attain the minimum recommendation of four visits as per World Health Organization guidelines.

Valuation of active blind spot detection systems by younger and older adults.

PubMed

Souders, Dustin J; Best, Ryan; Charness, Neil

2017-09-01

Due to their disproportional representation in fatal crashes, younger and older drivers both stand to benefit from in-vehicle safety technologies, yet little is known about how they value such technologies, or their willingness to adopt them. The current study investigated older (aged 65 and greater; N=49) and younger (ages 18-23; N=40) adults' valuation of a blind spot monitor and asked if self-reported visual difficulties while driving predicted the amount participants were willing to pay for a particular system (BMW's Active Blind Spot Detection System) that was demonstrated using a short video. Large and small anchor values ($250 and $500, respectively) were used as between subjects manipulations to examine the effects of initial valuation, and participants proceeded through a short staircase procedure that offered them either the free installation of the system on their current vehicle or a monetary prize ($25-$950) that changed in value according to which option they had selected in the previous step of the staircase procedure. Willingness to use other advanced driver assistance systems (lane-departure warning, automatic lane centering, emergency braking, adaptive cruise control, and self-parking systems) was also analyzed, additionally controlling for prior familiarity of those systems. Results showed that increased age was associated with a higher valuation for the Active Blind Spot Detection System in both the large and small anchor value conditions controlling for income, gender, and technology self-efficacy. Older adults valued blind spot detection about twice as much ($762) as younger adults ($383) in the large anchor condition, though both groups' values were in the range for the current cost of an aftermarket system. Similarly, age was the most robust positive predictor of willingness to adopt other driving technologies, along with system familiarity. Difficulties with driving-related visual factors also positively predicting acceptance levels for

Icons improve older and younger adults' comprehension of medication information.

PubMed

Morrow, D G; Hier, C M; Menard, W E; Leirer, V O

1998-07-01

We examined whether timeline icons improved older and younger adults' comprehension of medication information. In Experiment 1, comprehension of instructions with the icon (icon/text format) and without the icon (text-only format) was assessed by questions about information that was (a) implicit in the text but depicted explicitly by the icon (total dose in a 24 hour period), (b) stated and depicted in the icon/text condition (medication dose and times), and (c) stated but not depicted by the icon (e.g., side effects). In a separate task, participants also recalled medication instructions (with or without the icon) after a study period. We found that questions about dose and time information were answered more quickly and accurately when the icon was present in the instructions. Notably, icon benefits were greater for information that was implicit rather than stated in the text. This finding suggests that icons can improve older and younger adults' comprehension by reducing the need to draw some inferences. The icon also reduced effective study time (study time per item recalled). In Experiment 2, icon benefits did not occur for a less integrated version of the timeline icon that, like the text, required participants to integrate dose and time information in order to identify the total daily dose. The integrated version of the icon again improved comprehension, as in Experiment 1, as well as drawing inferences from memory. These findings show that integrated timeline icons improved comprehension primarily by aiding the integration of dose and time information. These findings are discussed in terms of a situation model approach to comprehension.

Designing an information search interface for younger and older adults.

PubMed

Pak, Richard; Price, Margaux M

2008-08-01

The present study examined Web-based information retrieval as a function of age for two information organization schemes: hierarchical organization and one organized around tags or keywords. Older adults' performance in information retrieval tasks has traditionally been lower compared with younger adults'. The current study examined the degree to which information organization moderated age-related performance differences on an information retrieval task. The theory of fluid and crystallized intelligence may provide insight into different kinds of information architectures that may reduce age-related differences in computer-based information retrieval performance. Fifty younger (18-23 years of age) and 50 older (55-76 years of age) participants browsed a Web site for answers to specific questions. Half of the participants browsed the hierarchically organized system (taxonomy), which maintained a one-to-one relationship between menu link and page, whereas the other half browsed the tag-based interface, with a many-to-one relationship between menu and page. This difference was expected to interact with age-related differences in fluid and crystallized intelligence. Age-related differences in information retrieval performance persisted; however, a tag-based retrieval interface reduced age-related differences, as compared with a taxonomical interface. Cognitive aging theory can lead to interface interventions that reduce age-related differences in performance with technology. In an information retrieval paradigm, older adults may be able to leverage their increased crystallized intelligence to offset fluid intelligence declines in a computer-based information search task. More research is necessary, but the results suggest that information retrieval interfaces organized around keywords may reduce age-related differences in performance.

Typography manipulations can affect priming of word stem completion in older and younger adults.

PubMed

Gibson, J M; Brooks, J O; Friedman, L; Yesavage, J A

1993-12-01

The experiments reported here investigated whether changes of typography affected priming of word stem completion performance in older and younger adults. Across all experiments, the typeface in which a word appeared at presentation either did or did not match that of its 3-letter stem at test. In Experiment 1, no significant evidence of a typography effect was found when words were presented with a sentence judgment or letter judgment task. However, subsequent experiments revealed that, in both older and younger adults, only words presented with a syllable judgment task gave rise to the typography effect (Experiments 2-4). Specifically, performance was greater, when the presentation and test typeface matched than when they did not. Experiment 5, which used stem-cued recall, did not reveal a difference between syllable and letter judgment tasks. These findings highlight the complex nature of word stem completion performance.

Risk of traumatic brain injuries in children younger than 24 months with isolated scalp hematomas.

PubMed

Dayan, Peter S; Holmes, James F; Schutzman, Sara; Schunk, Jeffrey; Lichenstein, Richard; Foerster, Lillian A; Hoyle, John; Atabaki, Shireen; Miskin, Michelle; Wisner, David; Zuspan, SallyJo; Kuppermann, Nathan

2014-08-01

We aimed to determine the association between scalp hematoma characteristics and traumatic brain injuries in young children with blunt head trauma who have no other symptoms or signs suggestive of traumatic brain injuries (defined as "isolated scalp hematomas"). This was a secondary analysis of children younger than 24 months with minor blunt head trauma from a prospective cohort study in 25 Pediatric Emergency Care Applied Research Network emergency departments. Treating clinicians completed a structured data form. For children with isolated scalp hematomas, we determined the prevalence of and association between scalp hematoma characteristics and (1) clinically important traumatic brain injury (death, neurosurgery for traumatic brain injury, intubation >24 hours for traumatic brain injury, or positive computed tomography (CT) scan in association with hospitalization ≥2 nights for traumatic brain injury); and (2) traumatic brain injury on CT. Of 10,659 patients younger than 24 months were enrolled, 2,998 of 10,463 (28.7%) with complete data had isolated scalp hematomas. Clinically important traumatic brain injuries occurred in 12 patients (0.4%; 95% confidence interval [CI] 0.2% to 0.7%); none underwent neurosurgery (95% CI 0% to 0.1%). Of 570 patients (19.0%) for whom CTs were obtained, 50 (8.8%; 95% CI 6.6% to 11.4%) had traumatic brain injuries on CT. Younger age, non-frontal scalp hematoma location, increased scalp hematoma size, and severe injury mechanism were independently associated with traumatic brain injury on CT. In patients younger than 24 months with isolated scalp hematomas, a minority received CTs. Despite the occasional presence of traumatic brain injuries on CT, the prevalence of clinically important traumatic brain injuries was very low, with no patient requiring neurosurgery. Clinicians should use patient age, scalp hematoma location and size, and injury mechanism to help determine which otherwise asymptomatic children should undergo

Sleepiness and Cognitive Performance among Younger and Older Adolescents across a 28-Hour Forced Desynchrony Protocol.

PubMed

Wu, Lora J; Acebo, Christine; Seifer, Ronald; Carskadon, Mary A

2015-12-01

Quantify the homeostatic and circadian effects on sleepiness and performance of adolescents. Examine age-related changes in homeostatic and circadian regulation of sleepiness and performance by comparing younger and older adolescent groups. Three-week laboratory study including 12 cycles of a 28-h forced desynchrony protocol. Controlled laboratory environment with individual sleep and performance testing rooms and shared common areas. Twenty-seven healthy adolescents including 16 females. Ages ranged from 9.6-15.2 years and participants were split into younger (n = 14 ages 9-12) and older (n = 13 ages 13-15) groups based on median age split of 13.0 years. N/A. Testing occurred every 2 h during scheduled wake periods. Measures included sleep latency during repeated nap opportunities and scores from a computerized neurobehavioral assessment battery including a 10-min psychomotor vigilance task, a digit symbol substitution task, and the Karolinska Sleepiness Scale. Significant main effects of circadian and homeostatic factors were observed, as well as several circadian and homeostatic interaction effects. Age group did not have a significant main effect on sleep and performance data. A significant interaction of circadian phase and age group was found for sleep latency, with younger adolescents showing greater circadian modulation than older teens during the circadian night. Adolescents demonstrated a similar pattern of response to forced desynchrony as reported for adults. Sleepiness and performance were affected by homeostatic and circadian factors, and age group did not interact with homoeostatic and circadian factors for subjective sleepiness and most performance metrics. Younger adolescents had a shorter latency to sleep onset than older during the circadian bin spanning 4 to 8 h after the onset of melatonin secretion. © 2015 Associated Professional Sleep Societies, LLC.

Will elderly patients stand aside for younger patients in the queue for cardiac services?

PubMed

Mariotto, A; De Leo, D; Buono, M D; Favaretti, C; Austin, P; Naylor, C D

1999-08-07

Fair management of queues for hospital-based services requires consideration of clinical need, but there is no information on public attitudes towards non-clinical factors such as age or work status as determinants of priority. We asked elderly residents of Padova, Italy, whether, if they were awaiting cardiac surgery or an outpatient cardiology consultant, they would give up their place in line for a younger or self-employed individual. We also elicited responses from a convenience sample of younger health workers asked to imagine themselves as elderly persons facing the same choices. The eligible response rate was 72% (443/616). About half deemed it right to give up their place in line for cardiac surgery to a 45-year-old (51%, 95% CI 46-56) or self-employed person (47%, 95% CI 42-51) Proportions were significantly higher for an outpatient consultation (68%, 95% CI 63-72). In multivariate analyses, married respondents, those closer to age 65, university graduates, and those who were formerly self-employed were significantly less likely to respond affirmatively. In significant contrast for all four scenarios (p<0.0001), the overwhelming majority of non-elderly respondents refused to give up their places in line. The majority of elderly citizens were hypothetically willing to cede priority in accessing cardiac care to younger or self-employed persons, but this willingness was attenuated among the "young" elderly and more privileged respondents. Non-elderly respondents were much less self-sacrificing, suggesting that ageing baby-boomers may be more assertive about their continuing rights to health care.

The Accuracy of Older and Younger Australians' Understanding of Mental Health and Aging.

ERIC Educational Resources Information Center

Peterson, Candida C.

1993-01-01

Administered quiz about positive and negative aspects of mental health in old age to 250 Australian adults (ages 17-81). Retirees scored lowest, with no significant differences among younger students versus nonstudents. Age was more important mediator of retirees' low scores than was gender, living with older person, or self-definition as retired.…

Receptive Vocabulary, Cognitive Flexibility, and Inhibitory Control Differentially Predict Older and Younger Adults' Success Perceiving Speech by Talkers with Dysarthria

ERIC Educational Resources Information Center

Ingvalson, Erin M.; Lansford, Kaitlin L.; Fedorova, Valeriya; Fernandez, Gabriel

2017-01-01

Purpose: Previous research has demonstrated equivocal findings related to the effect of listener age on intelligibility ratings of dysarthric speech. The aim of the present study was to investigate the mechanisms that support younger and older adults' perception of speech by talkers with dysarthria. Method: Younger and older adults identified…

Why are faces denser in the visual experiences of younger than older infants?

PubMed Central

Jayaraman, Swapnaa; Fausey, Caitlin M.; Smith, Linda B.

2017-01-01

Recent evidence from studies using head cameras suggests that the frequency of faces directly in front of infants declines over the first year and a half of life, a result that has implications for the development of and evolutionary constraints on face processing. Two experiments tested two opposing hypotheses about this observed age-related decline in the frequency of faces in infant views. By the People-input hypothesis, there are more faces in view for younger infants because people are more often physically in front of younger than older infants. This hypothesis predicts that not just faces but views of other body parts will decline with age. By the Face-input hypothesis, the decline is strictly about faces, not people or other body parts in general. Two experiments, one using a time-sampling method (84 infants 3 to 24 months in age) and the other analyses of head camera images (36 infants 1 to 24 months) provide strong support for the Face-input hypothesis. The results suggest developmental constraints on the environment that ensure faces are prevalent early in development. PMID:28026190

Sexual activity and prostate cancer risk in men diagnosed at a younger age.

PubMed

Dimitropoulou, Polyxeni; Lophatananon, Artitaya; Easton, Douglas; Pocock, Richard; Dearnaley, David P; Guy, Michelle; Edwards, Steven; O'Brien, Lynne; Hall, Amanda; Wilkinson, Rosemary; Eeles, Rosalind; Muir, Kenneth R

2009-01-01

To examine, in a case-control study, the association between the frequency of sexual activity (intercourse, masturbation, overall) and prostate cancer risk in younger men diagnosed at < or = 60 years old. In all, 431 prostate cancer cases and 409 controls participated and provided information on their sexual activity. In particular, the frequencies of intercourse and masturbation during the participants' different age decades (20s, 30s, 40s, 50s) were collected. Whereas frequent overall sexual activity in younger life (20s) increased the disease risk, it appeared to be protective against the disease when older (50s). Alone, frequent masturbation activity was a marker for increased risk in the 20s and 30s but appeared to be associated with a decreased risk in the 50s, while intercourse activity alone was not associated with the disease. These findings could imply different mechanisms by which sexual activity is involved in the aetiology of prostate cancer at different ages. Alternatively, there is a possibility of reverse causation in explaining part of the protective effect seen for men in their 50s.

The psychosocial needs of breast cancer survivors; a qualitative study of the shared and unique needs of younger versus older survivors.

PubMed

Thewes, B; Butow, P; Girgis, A; Pendlebury, S

2004-03-01

Due to improvements in medical treatment and survival following breast cancer, researchers have turned their attention to investigating the needs of breast cancer survivors. There is disagreement about the extent to which survivors continue to experience psychological morbidity after treatment ends. Whilst the majority of women adjust well to breast cancer, some may have continued psychosocial needs. Available research suggests that younger pre-menopausal women are at increased risk of psychological morbidity following breast cancer. The present study aimed to gather preliminary qualitative data on the psychosocial needs of breast cancer survivors and to identify the shared and unique needs of younger versus older survivors. A qualitative methodology was chosen as this was a relatively unexplored area of enquiry. Patients treated for early-stage breast cancer who had completed their hospital-based treatment 6-24 months prior to participation were recruited. Sampling was discontinued when informational redundancy was achieved. Eighteen telephone interviews were conducted. A wide variety of on-going psychosocial and information needs were reported by breast cancer survivors including support needs, psychological needs, practical needs, physical needs and information needs. Younger women reported more needs than their older counterparts. Several needs reported by younger women were directly related to being of younger age or pre-menopausal at the time of diagnosis. Clinical implications are discussed. Copyright 2003 John Wiley & Sons, Ltd.

Renal Tumors in Children Younger Than 12 Months of Age: A 65-Year Single Institution Review.

PubMed