bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiocarbon Ages of Soils and Charcoal in Late Wisconsinan Loess, South-Central Nebraska
Authors: May David W. , Holen Steven R.
Published: October 2002

The Farmdale Soil occurs below late Wisconsinan loess throughout the U.S. Midwest. At the La Sena site in the central Great Plains, humates in the Farmdale Interstadial Soil have a corrected age of 21,000 yr B.P. Humates in a buried Bt horizon and a bulk sample of overlying loess 2.5 m above the Farmdale Interstadial Soil have ages of 17,000 and 19,000 yr B.P., respectively. In the Republican River Valley Picea (spruce) charcoal is common in the lower meter of Peoria loess. Near Bloomington, Nebraska, humates from burned organic matter only 60 cm above the base of Peoria loess have a corrected age of ca. 19,000 yr B.P.
Characteristics and Possible Source of a 1479 A.D. Volcanic Ash Layer in a Greenland Ice Core
Authors: Fiacco R. Joseph , Palais Julie M. , Germani Mark S. , Zielinski Gregory A. , Mayewski Paul A.
Published: October 2002

A microparticle concentration peak in a GISP2 ice core contains volcanic glass shards of rhyolitic composition that correspond in age to the 1479-1480 A.D. Mt. St. Helens Wn eruption. These glass shards are compositionally similar to the Wn tephra and constitute 83% of the total particle population. The shards are very coarse-grained (up to 40 μm diameter), suggesting rapid transport from their source to Greenland. A major sulfate peak in the ice occurs approximately 4 months after deposition of the glass shards. This difference in depositional timing suggests primarily tropospheric transport of the ash and stratospheric transport of the sulfate aerosol. Large-scale climatic perturbations following this eruption were evidently negligible. Glaciochemical seasonal indicators suggest a late-fall to early-winter 1479 A.D. eruption.
Optical Dating of Holocene Dune Sands in the Ferris Dune Field, Wyoming
Authors: Stokes Stephen , Gaylord David R.
Published: October 2002

Optical dating of late Quaternary quartz dune sands from the Clear Creek portion of Ferris dune field, Wyoming, demonstrates the considerable potential of the technique as a chronostratigraphic tool. A sequence of radiocarbon-dated Holocene interdune strata permit optical dating of the intercalated dune sand to be tested; the concordance is good. The optical dates for the aeolian deposits not datable by radiocarbon suggest that aeolian sedimentation at Clear Creek peaked during two relatively short phases at ca. 8500 and 4000 yr B.P. The dates indicate that aeolian accumulation maxima (at least in the Clear Creek area) may not be synchronous with previously defined phases of marked aridity.
A Vegetation History of the Far North of New Zealand during the Late Otira (Last) Glaciation
Authors: Newnham Rewi , Ogden John , Mildenhall Dallas
Published: October 2002

During the latter part of the last (Otira) glaciation the forest cover of New Zealand was much reduced. It has frequently been postulated, however, that diverse mixed forest communities survived in the far north of North Island. Pollen diagrams and radiocarbon dates from two last glacial and postglacial (Aranuian) sits on the Aupouri Peninsula in the far north of New Zealand are compared with other published palynological and plant macrofossil evidence from the region. Mixed kauri/podocarp/angiosperm forest was present at times during the late Otiran (and Aranuian) and no evidence was found for substantial loss of forest. However, radiocarbon samples from one site, at least, seem to have been contaminated with young carbon; this introduces uncertainty into the chronology established at that site. Possibly nondeposition or erosion has obscured part or all of the late Otiran record at all the sites studied so that very much reduced forest cover at that time cannot be ruled out.
Radiocarbon Ages from Two Submerged Strandline Features in the Western Gulf of Maine and a Sea-Level Curve for the Northeastern Massachusetts Coastal Region
Authors: Oldale Robert N. , Colman Steven M. , Jones Glen A.
Published: October 2002

New radiocarbon dates provide ages for two submerged strandline features on the Massachusetts inner shelf. These ages provide limited control on a relative sea-level (RSL) curve for the late Wisconsinan and Holocene. The curve indicates a late Wisconsinan high stand of RSL of +33 m about 14,000 yr ago and a very short-lived relative low stand of about -43 m at about 12,000 yr ago followed by a rise to present sea level. Rapid changes of RSL around 12,000 yr ago may be related to changes in global glacial meltwater discharge and eustatic sea-level change shown by dated corals off Barbados. Variations in the magnitude and timing of RSL change from south to north along the coast of the western Gulf of Maine are due to greater crustal depression and later deglaciation to the north.
Manganese Accumulation in Rock Varnish on a Desert Piedmont, Mojave Desert, California, and Application to Evaluating Varnish Development
Authors: Reneau Steven L.
Published: October 2002

Rock varnish coatings tend to become thicker, darker, and more continuous over time, leading to the use of changes in overall varnish color and the percentage of clast surfaces covered by varnish as relative-age indicators. Manganese is the most characteristic element of subaerial rock varnishes, and the progressive development of varnish coats can be quantified by measuring the amount of Mn accumulated on a given area of rock surface. Manganese oxides were dissolved off varnished clasts collected from alluvial surfaces on the Soda Mountains piedmont in the Mojave Desert, California, and the amount of Mn was measured using inductively coupled plasma emission spectroscopy. On the distal piedmont, maximum varnish development increases from a mid- to late-Holocene surface, typically containing up to 0.15 mg/cm2of accumulated Mn, to an early- to mid-Holocene surface with up to 0.21 mg/cm2. However, varnish is less developed on a nearby late Pleistocene surface, suggesting extensive abrasion of clasts on the Pleistocene desert pavements or disturbance of the clasts. Varnish is better developed on the proximal piedmont, typically containing up to 0.30 mg/cm2of Mn, although varnish from a Pleistocene surface is again no better developed than from a nearby early- to mid-Holocene surface. These data demonstrate that rock varnish can show significant spatial variation in degree of development on geomorphic surfaces of similar age, and imply that collecting varnish as old as a geomorphic surface may be difficult on surfaces as young as late Pleistocene.
Geochronological Potential of Isoleucine Epimerization in Calcite Speleothems
Authors: Lauritzen Stein-Erik , Erik Haugen John , Løvlie Reidar , Gilje-Nielsen Helge
Published: October 2002

The extent of isoleucine epimerization in a calcite speleothem was determined to evaluate the amino acid racemization method in abiotic calcite. A 5.5-cm-thick flowstone slab from Hamarnesgrotta, northern Norway, was analyzed for amino acid concentration, composition, and isoleucine epimerization at 26 levels through the sequence. U-series dates provide an independent chronologic control. Epimerization increases monotonically with stratigraphic depth and linearily with U-series age, independent of amino acid concentrations. The rate of epimerization is calibrated against the U-series dates, and extrapolation into lower strata beyond the U-series limit yields absolute age estimates that are consistent with paleomagnetic data from the same speleothem. The results suggest that, if adequately calibrated, amino acid dating is applicable to speleothem material reaching time spans beyond the range of conventional dating methods. Amino acids in the speleothem were probably derived from surface soils and are associated with brown humic stains in the calcite.
Evidence of Atmospheric Paleocirculation over the Gulf of Guinea since the Last Glacial Maximum
Authors: Lezine Anne-Marie , Tastet Jean-Pierre , Leroux Marcel
Published: October 2002

High-resolution pollen and eolian input studies from core KS 84063 in the Gulf of Guinea record the response of the tropical atmospheric circulation to global paleoclimatic events during the last glacial/interglacial transition. Two depositional phases centered around 15,000 and 10,300 yr B.P. are characterized by maximum values of pollen concentration and of eolian activity index (EA1). Pollen spectra record the significant presence of Artemisia and Ephedra of Saharan origin and the scattered occurrence of Podocarpus from Guinean mountain forests; these demonstrate the intensity of the meridional atmospheric circulation over equatorial West Africa during dry periods. The early Holocene humid phase, ca. 8500 yr B.P., is marked by minima in pollen concentrations and EAI. Saharan taxa are absent and, in contrast, Podocarpus reached its highest relative values. This evidence has been interpreted as reflecting a weakening in the continentocean eolian transport and the importance of monsoonal fluxes. Downcore variations in Podocarpus percentages are used to identify the atmospheric circulation patterns over the low latitudes of West Africa during extreme (dry/humid) climatic conditions.
Isotopic Approach to Soil Carbonate Dynamics and Implications for Paleoclimatic Interpretations
Authors: Pendall Elise G. , Harden Jennifer W. , Trumbore Sue E. , Chadwick Oliver A.
Published: October 2002

The radiocarbon content and stable isotope composition of soil carbonate are best described by a dynamic system in which isotopic reequilibration occurs as a result of recurrent dissolution and reprecipitation. Depth of water penetration into the soil profile, as well as soil age, determines the degree of carbonate isotope reequilibration. We measured δ13C, δ18O and radiocarbon content of gravel rinds and fine (<2 mm) carbonate in soils of 3 .different ages (1000, 3800, and 6300 14 C yr B.P.) to assess the degree to which they record and preserve a climatic signal. In soils developing in deposits independently dated at 3800 and 6300 radiocarbon yr B.P., carbonate radiocarbon content above 40 cm depth suggests continual dissolution and reprecipitation, presumably due to frequent wetting events. Between 40 and 90 cm depth, fine carbonate is dissolved and precipitated as rinds that are not redissolved subsequently. Below 90 cm depth in these soils, radiocarbon content indicates that inherited, fine carbonate undergoes little dissolution and reprecipitation. In the 3800- and 6300-yr-old soils, δ13C in rind and fine carbonate follows a decreasing trend with depth, apparently in equilibrium with modern soil gas, as predicted by a diffusive model for soil CO2. δ18O also decreases with depth due to greater evaporative enrichment above 50 cm depth. In contrast, carbonate isotopes in a 1000-yr-old deposit do not reflect modern conditions even in surficial horizons; this soil has not undergone significant pedogenesis. There appears to be a lag of at least 1000 but less than 3800 yr before carbonate inherited with parent material is modified by ambient climatic conditions. Although small amounts of carbonate are inherited with the parent material, the rate of pedogenic carbonate accumulation indicates that Ca is derived primarily from eolian and rainfall sources. A model describing carbonate input and radiocarbon decay suggests that fine carbonate below 90 cm is mostly detrital (inherited) and that carbonate rinds have been forming pedogenically at a constant rate since alluvial fans were deposited.
Reversed-Polarity Glacial Sediments and Revised Glacial Chronology, West Branch Susquehanna River Valley, Central Pennsylvania
Authors: Gardner Thomas W. , Sasowsky Ira D. , Schmidt Victor A.
Published: October 2002

A new exposure of glacial and glaciolacustrine sediments at Antes Fort allows for revision of the chronology of pre-Wisconsinan glaciation in central Pennsylvania. Lacustrine sediments from a proglacial lake in the West Branch Susquehanna River valley have reversed remanent polarity with a site mean paleomagnetic declination of 193.8° and inclination of -13.1°. The magnetization is probably a true detrital remanence from the time of deposition and is not significantly affected by postdepositional diagenesis. We propose that the Antes Fort till was deposited during either pre-Illinoian glaciation F or G of G. M. Richmond and D. S. Fullerton (1986, "Quaternary Science Reviews," Vol. 5, 183-196) between 770,000 and 970,000 yr ago. We suggest that it is equivalent to the Penny Hill till in the West Branch Susquehanna River valley and tentatively correlate it westward with the reversed polarity terrace deposits and Minford Silt in western Pennsylvania, West Virginia, and Ohio; the West Lebanon till in Indiana; and the A4 tills (or possible B tills) in Iowa and Nebraska.
Late-Glacial and Early Holocene Sea-Level Fluctuations in the Central Puget Lowland, Washington, Inferred from Lake Sediments
Authors: Anundsen Karl , Abella Sally , Leopold Estella , Stuiver Minze , Turner Sheila
Published: October 2002

Analyses of sediments, diatoms, and pollen in a 12.65-m-long sediment core taken from Lake Carpenter in the central Puget Lowland, Washington, provide detailed information regarding the history of deglaciation and late-glacial/early Holocene sea-level changes. The lake outlet, now 8.2 m above sea level, has been lowered 1-1.5 m by postglacial erosion. The lithology and pollen record suggest that no lengthy hiatuses in sedimentation have occurred. The basal sediments are glacialmarine and contain shell fragments and brackish/marine diatoms. Freshwater sediments above the basal section are interrupted only by a short section containing few fossils, most of which are brackish to marine indicators, and by the Mazama tephra at 9.5 m. The pollen record in the basal 4 m reveals a Pinus zone (ca. 13,850-11,000 yr B.P.) with a brief peak of Picea at ca. 13,700 yr B.P., and an Alnus/Pseudotsuga zone (ca. 11,000-6500 yr B.P.). The chronology is based on nine radiocarbon ages. A relative lowering of sea level below the 9.5-m threshold is recorded in the core at 12.41 m and dates 13,850 to 13,700 yr B.P. A marine episode occurred about 13,600 yr B.P., implying that relative sea-level temporarily rose above 9.5 m. No subsequent transgressions above the 9.5-m level have been recorded. Comparison of six radiocarbon dates ≥13,600 yr B.P. suggest that the marine reservoir correction of 760 yr currently used for this area may be too high for this time period.
Evidence of Active Dune Sand on the Great Plains in the 19th Century from Accounts of Early Explorers
Authors: Muhs Daniel R. , Holliday Vance T.
Published: October 2002

Eolian sand is extensive over the Great Plains of North America, but is at present mostly stabilized by vegetation. Accounts published by early explorers, however, indicate that at least parts of dune fields in Nebraska, Colorado, Kansas, New Mexico, and Texas were active in the 19th century. Based on an index of dune mobility and a regional tree-ring record, the probable causes for these periods of greater eolian activity are droughts, accompanied by higher temperatures, which greatly lowered the precipitation-to-evapotranspiration ratio and diminished the cover of stabilizing vegetation. In addition, observations by several explorers, and previous historical studies, indicate that rivers upwind of Great Plains dune fields had shallow, braided, sandy channels, as well as intermittent flow in the 19th century. Wide, braided, sandy rivers that were frequently dry would have increased sand supplies to active dune fields. We conclude that dune fields in the Great Plains are extremely sensitive to climate change and that the potential for reactivation of stabilized dunes in the future is high, with or without greenhouse warming.
Warming at 18,000 yr B.P. in the Tropical Andes
Authors: Helmens Karin F. , Kuhry Peter , Rutter Nathaniel W. , Van Der Borg Klaas , De Jong Arie F. M.
Published: October 2002

Palynological, paleopedological, and glacial geomorphological evidence from the area of the high plain of Bogotá in the Colombian Eastern Cordillera indicates a significant climatic warming around 18,00014C yr B.P. Comparison of dated vegetation changes, pedogenic episodes, and glacier fluctuations provides the basis for defining the so-called “La Laguna Interstadial” that lasted from 19,500 to 17,000 yr B.P. During this interstadial period, mean annual temperatures in the tropical Andes were up to 4°C higher than during the preceding and following stadial periods, when full-glacial conditions prevailed and temperatures were up to 8°C colder than at present.
Vegetation History of Pleasant Island, Southeastern Alaska, since 13,000 yr B.P.
Authors: Hansen Barbara C. S. , Engstrom Daniel R.
Published: October 2002

A 13,000-year history of late-Quaternary vegetational and climatic change has been derived from lacustrine sediments from Pleasant Island in the Glacier Bay region of southeastern Alaska. Early arrival of lodgepole pine and mountain hemlock, indicated by the presence of pollen and conifer stomata, suggests expansion from refugia in the Alexander Archipelago. A short-term climatic reversal, possibly correlated with the European Younger Dryas, is inferred from the expansion of tundra elements and deposition of inorganic sediments between 10,600 and 9900 14C yr B.P. Two peat cores from the lake catchment verify Holocene vegetation changes and aid in the separation of biogenic from climatic forces affecting vegetation history. Differences in pollen representation among the three cores illustrate the variation among pollen-collecting substrates, as well as the spatial heterogeneity of peatland development and its dependence on local hydrology. Initial peat accumulation and soil paludification, occasioned by increases in temperature and precipitation in the early Holocene, allowed western and mountain hemlock to replace sitka spruce 8500–8000 yr B. P. Open muskeg became widespread about 7000 yr B. P. and allowed lodgepole pine to reinvade the region after a 2000-yr absence. The extensive replacement of fen elements by bog taxa at 3400 yr B. P. suggests increased paludification due to changing hydrologic conditions; its correlation with the upland expansion of Tsuga heterophylla suggests the onset of a cooler/wetter Neoglacial climate in southeastern Alaska.
Paleohydrology and Paleoclimate of the Past 33,000 Years at the Tamanduá River, Central Brazil
Authors: Turcq Bruno , Pressinotti Marcia M.N. , Martin Louis
Published: October 2002

Deposits of the Tamanduá River contain evidence for four major paleohydrologic stages in the last 33,000 years. A wet period between 33,000 and 20,00014C yr B.P. produced a high water table that allowed organic-rich deposition in the Tamanduá valley. A dry interval 17,000-10,00014C yr B.P. produced sandy deposits of braided channels and alluvial fans. River aggradation during this period probably resulted from a high sediment load promoted by intense slope erosion and from flash floods. A wet period after 10,000 and before 600014C yr B.P. was marked by reduced slope erosion and by high discharge that led to erosion of the valley fill. During that time forests developed widely in Brazil. A drier climate after 600014C yr B.P. caused a reduction of discharge but allowed a high water table to be maintained.
Paleosol Stable Isotope Evidence for Early Hominid Occupation of East Asian Temperate Environments
Authors: Wang Hong , Ambrose Stanley H. , Liu Chao-Li Jack , Follmer Leon R.
Published: October 2002

Hominids left Africa and occupied mainland Asia by 1.8 myr ago. About 1.15 myr agoHomo erectusand an associatedStegodon–Ailuropodafauna migrated from subtropical China across the Qinling Mountains into the temperate Loess Plateau. This migration may be an evolutionary milestone in human adaptability because it may represent the first occupation of a nontropical environment. Loess–paleosol stable isotope ratios from the last interglacial–glacial cycle provide comparative data for reconstructing the hominid paleoenvironments. The climate during Gongwangling hominid occupation about 1.15 myr ago was influenced by both Siberian–Mongolian winter and Indian summer monsoon systems characterized as a cold/cool, dry winter and warm/mild, semihumid summer and fall. The Gongwangling hominids preyed mainly on warm-climate-adapted animals such asStegodon–Ailuropodafauna, suggesting a warm season occupation. The stable isotope ratios also indicate that the Chenjiawo hominids occupied an environment similar to that of the Gongwangling about 650,000 yr ago. The associated fauna, with a mixture of forest and steppe, warm- and cold/cool-climate-adapted animal assemblage's, suggests a permanent occupation by this time. Thus, the reliable earliest and permanent occupation of temperate environments may have occurred 150,000 yr earlier in eastern Asia rather than in Europe.
Palynological Evidence for Climatic Change and Human Activity during the Holocene on Minorca (Balearic Islands)
Authors: Yll Errikarta-Imanol , Perez-Obiol Ramon , Pantaleon-Cano Jose , Roure Joan Maria
Published: October 2002

Four pollen diagrams from Minorca (Balearic Islands) have been correlated with other previously studied sequences from Majorca and Minorca to define a Holocene landscape sequence for the region from 8000 yr B.P. to the present. The lower part of the pollen diagrams reflects a climatic phase with more rain and less-marked seasonality than today. Significant quantities of Corylus, Buxus, and mesophilous taxa are found. In the middle part, between 5000 and 4000 yr B.P., a strong change is recorded in composition and structure of the vegetational landscape, with vegetation appearing that was adapted to Mediterranean conditions. This episode coincided with the first human colonization of the island and also with a widespread climatic change in the western Mediterranean region. The change in taxa was complex and some sclerophyllous taxa such Olea played an important role in the transformation of the landscape physiognomy from the mid-Holocene until the present. Although human activities have removed much of the Mediterranean vegetation on the Balearic Islands, it seems clear that the changes have been brought about, in part, by increasing dryness.
Deposits and Soils of the Past 130,000 Years at the Desert–Loess Transition in Northern China
Authors: Sun Jimin , Ding Zhongli
Published: October 2002

The desert–loess transitional zone in north-central China has long been thought sensitive to Quaternary climatic change. However, reconstruction of Quaternary climates in this area has been hindered by incompleteness of geological sections. Here we report the analytical results of two recently found sand–loess–soil sections. Both sections have thick eolian deposits from the last interglacial–glacial cycle and can be correlated with one another. Field observations, thermoluminescence dating, and other laboratory analyses show that the last interglacial period produced three paleosols and two intercalated loess layers. Loess from the last glacial period is interbedded with three sand horizons that represent desert extension. The expansion and contraction of desert in northern China may have been forced by the east Asia monsoon.
Holocene Lakes from Ramlat as-Sab'atayn (Yemen) Illustrate the Impact of Monsoon Activity in Southern Arabia
Authors: Lézine Anne-Marie , Saliège Jean-François , Robert Christian , Wertz Frédéric , Inizan Marie-Louise
Published: October 2002

Paleoecology and paleohydrology of the Ramlat as-Sab'atayn (Southern Arabia) are reconstructed from a comparative study including sedimentology, mineralogy, stable isotope ratios of carbonates, and palynology of lacustrine sediments recovered from the al-Hawa depression. The section dates from 8700 to 7200 yr B.P. and records an early phase of flooding followed by distinct lacustrine development from 7800 to 7200 yr B.P., coeval with maximum activity of the Indian monsoon. Comparison of the pollen record with modern pollen deposition suggests that regional vegetation was then already of desert type and was related to strong seasonal trade winds.
Chevron Ridges and Runup Deposits in the Bahamas from Storms Late in Oxygen-Isotope Substage 5e
Authors: Hearty Paul J. , Neumann A.Conrad , Kaufman Darrell S.
Published: October 2002

Landward-pointing V-shaped sand ridges several kilometers long are common along the windward margin of the Bahama Islands. Their axes share a northeast–southwest trend. Internally, the ridges contain low-angle oolitic beds with few erosional truncations. Commonly interbedded are tabular, fenestrae-rich beds such as those formed by the sheet flow of water over dry sand. Defined here as “chevron ridges,” these landforms appear to have originated in the rapid remobilization of bank margin ooid bodies by the action of long-period waves from a northeasterly source. Deposits along adjacent coastlines also preserve evidence of the impact of large waves. Reworked eolian sand bodies preserve beach fenestrae and hydraulic scour traces up to +40 m on older ridges. On cliffed coasts, 1000-ton boulders have been thrown well inland, recording the impact of large waves. Amino acid ratios confirm a correlation of the ridges across the archipelago, while stratigraphy, spacing, and cross-cutting relationships indicate emplacement as sea level fell rapidly from the substage 5e maximum at or above +6 m.
Effects of Climate Change on Soils in Glacial Deposits, Wind River Basin, Wyoming
Authors: Hall Robert D.
Published: October 2002

Soil chronofunctions are often quasilinear, but those relationships may be only gross, fortuitous generalizations that ignore changes in soils resulting from climatic and other cyclic external influences that govern soil formation or soil degradation. In the Rocky Mountains, soil development has been extensively used to estimate the age of sediments, but the number of soils is usually few, and large ranges in values for soil data may be dismissed as “normal variation.” In a detailed study of soils in the Wind River Range and Wind River Basin, characteristics of near-surface horizons do not follow age trends. However, the underlying carbonate-bearing horizons do have age-related characteristics. This “soil paradox” may be related to glacial–interglacial cycles in which (1) wind erodes near-surface horizons and then provides new parent material and (2) cryoturbation disrupts carbonate horizons, remobilizing carbonate and changing carbonate morphology but with only minimal loss of carbonate from the soil.
Wet Conditions during the Last Glaciation in the Chihuahuan Desert, Alta Babicora Basin, Mexico
Authors: Metcalfe Sarah , Say Alison , Black Stuart , McCulloch Robert , O'Hara Sarah
Published: October 2002

A 467-cm core (B94/3) from the Alta Babicora basin in the Chihuahuan Desert, northern Mexico (29°N, 108°W), documents lake-level and climate changes over the past ca. 65,000 yr. Chronological control is provided by four accelerator mass spectrometry14C dates and five U-series dates on diatom silica. The core has been analyzed for magnetic susceptibility, loss-on-ignition, carbonate content, sediment chemistry and mineralogy, and pollen and diatom composition. The basin was occupied by a deep freshwater lake throughout the late Pleistocene which, based on shoreline evidence, was at least 19 m deeper than today. The lake shallowed after ca. 57,000 yr B.P. High variability typified the period between 54,600 and 38,000 yr B.P., probably with periodic desiccation and deflation. A deep-water lake was reestablished after 38,000 yr B.P. and persisted until ca. 29,000 yr B.P. Shallowing occurred through the last glacial maximum, although the lake was still deeper than at present. The Pleistocene–Holocene transition was marked by a distinctive change in the diatom flora. There is no diatom record for much of the Holocene, but other proxies indicate generally dry, stable catchment conditions. The Babicora record is more akin to those from the southwest United States than it is to Central America and northern South America. Wet conditions in the late Pleistocene are attributed to winter rainfall from midlatitudes in contrast to the modern, tropical, summer rainfall regime.
Current value of intraoperative sonography during surgery for hepatic neoplasms
Authors: Zacherl Johannes , Scheuba Christian , Imhof Martin , Zacherl Maximilian , Längle Friedrich , Pokieser Peter , Wrba Fritz , Wenzl Etienne , Mühlbacher Ferdinand , Jakesz Raimund , Steininger Rudolf
Published: October 2002

Noninvasive liver imaging has developed rapidly resulting in increased accuracy for detecting primary and secondary hepatic tumors. Intraoperative ultrasonography (IOUS) was commonly considered to be the gold standard for liver staging, but the current value of IOUS is unknown in view of more sophisticated radiologic tools. The purpose of this prospective study was to evaluate the impact of IOUS on the treatment of 149 patients undergoing liver surgery for malignant disease (colorectal metastasis, 61 patients; hepatoma, 52 patients; other hepatic malignant tumors, 36 patients). The sensitivities of computed tomography (CT), helical CT, magnetic resonance imaging, and IOUS in patients with colorectal metastases were 69.2%, 82.5%, 84.9%, and 95.2% in a segment‐by‐segment analysis; in patients with hepatoma their sensitivities were 76.9%, 90.9%, 93.0%, and 99.3%; and in patients with other hepatic malignancies they were 66.7%, 89.6%, 93.3%, and 98.9%, respectively. Additional malignant lesions (AMLs) were first detected by inspection and palpation in 20 patients (13.4%). In another 18 patients (12.1%) IOUS revealed at least one AML. Overall, the findings obtained only by IOUS changed the surgical strategy in 34 cases (22.8%). It was concluded that IOUS, having undergone some refinement as well, still has immense diagnostic value in hepatectomy candidates. Frequently avoiding palliative liver resection and occasionally disproving unresectability as assessed by preoperative imaging, IOUS still has a significant impact on surgical decision making and should still be considered the gold standard.
Pyloric motility after pylorus‐preserving gastrectomy with or without the pyloric branch of the vagus nerve
Authors: Nakabayashi Toshihiro , Mochiki Erito , Garcia Moises , Haga Norihiro , Suzuki Tomoaki , Asao Takayuki , Kuwano Hiroyuki
Published: October 2002

An attempt was made to examine gastropyloric motility after pylorus‐preserving gastrectomy (PPG) and to determine the influence of the pyloric branch of the vagus nerve in the dog. Fifteen dogs were divided into three groups of five. PPG with preservation (PPPG) and resection of the pyloric branch of the vagus (RPPG) were performed, and controls were prepared. Interdigestive and digestive gastropyloroduodenal motility was recorded after a 2‐week recovery period using strain‐gauge force transducers (SG). Radiopaque markers (ROMs) were used to assess gastric emptying. No significant differences were found between PPPG and RPPG in terms of gastropyloroduodenal motility during either the interdigestive or the postprandial state. During phase III of the interdigestive state, pyloric relaxation correlated with contraction of the gastric body after both PPPG and RPPG. During the first month it was accompanied by tonic and phasic pyloric contractions after feeding and delayed gastric emptying in two groups. By the end of the first month these pyloric contractions had diminished, and the rate of gastric emptying was similar to that of the controls. We concluded that it is not necessary to preserve the pyloric branch of the vagus for gastropyloroduodenal motility after PPG. Gastric stasis during the early postoperative period is due to tonic and phasic contractions of the pylorus.
Antiseptic wick: Does it reduce the incidence of wound infection following appendectomy?
Authors: McGreal Gerald T. , Joy Aislinn , Manning Brian , Kelly John L. , O’Donnell Joseph A. , William W. , Kirwan O. , Redmond H. Paul
Published: October 2002

The role of prophylactic antibiotics is well established for contaminated wounds, but the use of antiseptic wound wicks is controversial. The aim of this work was to study the potential use of wound wicks to reduce the rate of infection following appendectomy. This prospective randomized controlled clinical trial was conducted at a university hospital in the department of surgery. The subjects were patients undergoing appendectomy for definite acute appendicitis. They were randomized by computer to primary subcuticular wound closure or use of an antiseptic wound wick. For the latter, ribbon gauze soaked in povidone‐iodine was placed between interrupted nylon skin sutures. Wicks were soaked daily and removed on the fourth postoperative day. All patients received antibiotic prophylaxis. They were reviewed while in hospital and 4 weeks following operation for evidence of wound infection. The main outcome measures were wound infection, wound discomfort, and cosmetic result. The overall wound infection rate was 8.6% (15/174). In patients with wound wicks it was 11.6% (10/86) compared to 5.6% (5/88) in those whose wounds were closed by subcuticular sutures (p=NS). We concluded that the use of wound wicks was not associated with decreased wound infection rates following appendectomy. Subcuticular closure is therefore appropriate in view of its greater convenience and safety.
Short‐ and long‐term outcome and health‐related quality of life after severe peritonitis
Authors: Scheingraber Stefan , Kurz Tanja , Dralle Henning
Published: October 2002

The short‐form survey 36 (SF‐36) is a useful and qualified instrument for measurement of health‐related quality of life (HRQL) in critically ill patients. In this study we determined hospital mortality, hospital discharge mortality, and HRQL of 136 patients with severe peritonitis admitted to our hospital between January 1996 and May 1999. Hospital mortality was 46% and hospital discharge mortality 10%. The HRQL‐questionnaire was answered completely by 97% of the patients who where still alive during the study period. Age significantly reduced physical functions in these patients. Patients with cancer had significant impaired physical functions in the first year, followed by significant impairment in emotion. Generally, patients who survived peritonitis and had no malignancy had an acceptable outcome when compared to individuals from a large normal population. Health‐related quality of life measurements in peritonitis patients justify the high efforts in the treatment of these patients, but they do not provide a useful tool in the outcome prediction for individual patients.
Impact of the latest TNM classification for gastric cancer: Retrospective analysis on 94 D2 gastrectomies
Authors: D’Ugo Domenico , Pacelli Fabio , Persiani Roberto , Pende Vito , lanni Andrea , Papa Valerio , Doglietto Giovanni Battista , Picciocchi Aurelio
Published: October 2002

The aim of this study was to determine whether the latest edition of tumor‐node‐metastasis (TNM) classification provides reliable prognostic information. The fifth edition of TNM Classification of Malignant Tumors has introduced for gastric cancer the numeric count of involved lymph nodes whereas their topographic location was considered in earlier editions. For our study, data from 94 patients who underwent D2‐gastrectomy were reviewed. The N‐factor was scored according to both the Japanese Research Society for Gastric Cancer (JRSGC) classification (n) and, retrospectively, the latest TNM classification (N). Actuarial survival was calculated for both groups. The two staging systems showed similar stratification of actuarial survival with relation to N‐stage; in the JRSGC classification no statistical differences were observed between nl and n2 patients (62.7% vs. 52.5%; p=NS), whereas the 5th TNM classification showed a significant difference between Nl and N2 patients (68.5% vs. 45.0%; p=0.04), and between Nl and the new category of N3 patients (68.5% vs. 45.0%, p=0.03). It appears, therefore, that the numeric count of involved nodes may represent a more reliable indicator for single‐case prognosis. Reclassification of all node‐positive patients in our series caused an overall stage modification in 32.9% (31/94); 22 of those patients were reclassified to a less favorable stage (23.4%). In addition, 11.7% of patients (6/51) who were previously designated nl were reclassified as N2, shifting from an expected actuarial survival after 72 months of 62.7% to 33.3%.
Impact of grade of dysplasia in villous adenomas of vater’s papilla
Authors: Heidecke Claus‐Dieter , Robert Rosenberg , Bauer Markus , Martin Werner , Weigert Norbert , Ulm Kurt , Roder Jürgen D. , Siewert Jórg‐Rüdiger
Published: October 2002

Therapeutic strategies for villous adenoma of the papilla of Vater remain controversial. This study evaluates the accuracy of preoperative histopathologic diagnosis and the impact of the grade of dysplasia on recurrence as well as on potential alteration of the surgical approach. A series of 32 patients with an adenoma of Vater’s papilla who underwent local resection or pylorus‐preserving pancreaticoduodenectomy between January 1990 and August 2000 were reviewed retrospectively. Multiple endoscopic biopsies had been performed preoperatively. The histopathology of the preoperatively obtained biopsy specimens and subsequent surgical specimens were evaluated for grade of dysplasia by two pathologists and correlated with the clinical course after operative treatment. Altogether, 3 of 11 patients (27%) with a low‐grade (LG) dysplasia adenoma and 6 of 21 patients (29%) with a high‐grade (HG) dysplasia adenoma in the initial endoscopic biopsy specimens exhibited invasive carcinoma at the postoperative histologic examination (NS). Recurrence was not observed in the 6 patients from the LG dysplasia adenoma group following local resection and benign postoperative histology. In contrast, recurrence of villous adenoma was discovered in 2 of 12 patients (17%) and development of invasive carcinoma in 5 of 12 patients (42%) from the preoperative HG dysplasia group (p<0.05). The overall risk of carcinoma after primary diagnosis of an HG dysplasia adenoma was 44% (14/32). Adenoma of the papilla of Vater including HG dysplasia appears to be associated with a high risk of exhibiting invasive carcinoma postoperatively and a high rate of recurrence. Therefore pylorus‐preserving pancreaticoduodenectomy should be offered to patients with an HG dysplasia adenoma.
Minilaparotomy approach to terminal ileal Crohn’s disease
Authors: Nakagoe Tohru , Sawai Terumitsu , Tsuji Takashi , Jibiki Masa‐aki , Nanashima Atsushi , Yamaguchi Hiroyuki , Yasutake Toru , Ayabe Hiroyoshi
Published: October 2002

The feasibility and safety of a minilaparotomy approach to terminal ileal Crohn’s disease have not been fully elucidated. The purpose of this study was to compare early outcomes utilizing this technique as an alternative to conventional approaches. Nine patients with terminal ileal Crohn’s disease (but no complicating enteric fístulas) who underwent minilaparotomy between January 1998 and September 2000 were studied prospectively. The minilaparotomy approach entails a complete surgical procedure performed through a skin incision of less than 7 cm. Ten similar patients who underwent conventional laparotomy between January 1995 and December 1997 served as the control group. Age, gender, body weight, height, body mass index, number of prior laparotomies, operating times, operative blood loss, and types of operative procedure were similar for cases and controls. The length of the laparotomy incision in the minilaparotomy approach group was significantly shorter than that in the conventional approach group (median length 6.0 vs. 16.5 cm; p<0.05). Postoperative intervals until initial standing and walking were significantly shorter for minilaparotomy patients than conventional surgery patients (p<0.05 andp<0.05, respectively), whereas postoperative intervals until passing flatus, urinary catheter removal, and tolerance of liquids and solids did not differ for the two groups, nor did the analgesic requirement or postoperative hospital stay. Postoperative complications developed in two conventional‐group patients; none was noted with the minilaparotomy approach. Our data suggest that the minilaparotomy approach to terminal ileal Crohn’s disease without an enteric fistula is feasible, safe, and less invasive than the conventional approach.
A small circle of friends: Cohort groups as learning communities
Authors: Lipson Lawrence Randee
Published: October 2002

Cohort groups in adult and higher education programs provide the skills needed to build and maintain learning communities, which are needed for healthy and sustainable societies.
False memories and source‐monitoring problems: criterion differences
Authors: Hekkanen Steve T. , McEvoy Cathy
Published: October 2002

A source‐monitoring/memory suggestion experiment was used to produce false memories and a signal‐detection analysis was conducted to determine if criterion differences could help explain their production. The procedure and stimuli were adapted from Zaragoza and Lane (1994). Participants saw slides depicting a crime and then answered questions about the slides with some of the questions containing suggested or misleading information. After a brief delay filled with several assessment tests, a list of items was presented and the participants were asked to identify whether each item came from the slides, the questions, both or neither. The results showed that all participants produced false memories but those who adopted more lenient criteria produced more false memories. In addition, those with stricter criteria scored lower on an assessment of dissociative experiences. These results were interpreted within a source‐monitoring framework. Copyright © 2002 John Wiley & Sons, Ltd.
Children's memory for television advertising: effects of programme–advertisement congruency
Authors: Gunter Barrie , Baluch Bahman , Duffy Linda J. , Furnham Adrian
Published: October 2002

The effects of the surrounding programme environment and level of involvement upon children's memory (year 6 primary school, mean age 11.1, SD = 0.4, 48 boys and 69 girls) for television advertisements was examined by manipulating the degree of congruency between the production genre of the programme and the advertisements embedded within it. In Experiment One (n = 56) the ad‐break comprised either all cartoons (n = 4) or all non‐cartoons (n = 4). In Experiment Two (n = 61) cartoon and non‐cartoon advertisements were equally represented in each ad‐break. After viewing, participants provided evaluative ratings of the programme and completed memory tests for advertisements, using prompted recall and brand‐recognition tasks. Memory performance overall was better for cartoon advertisements than for non‐cartoon advertisements, with the latter being poorly remembered when presented in the non‐cartoon programme. In Experiment Two, the programme had no effect on overall recall of advertising, but was related to brand recognition, which was better for advertisements placed in the cartoon programme. Free recall of non‐cartoon advertisements was best when placed in the cartoon programme, while free recall only of cartoon advertisements was best when placed in the non‐cartoon programme. The measures of audience involvement (programme ratings) did not show any significant correlation with memory for advertising. Copyright © 2002 John Wiley & Sons, Ltd.
Participants' free‐hand drawings of a target face can influence recognition accuracy and the confidence–accuracy correlation
Authors: McClure Kimberley A. , Shaw John S.
Published: October 2002

Two experiments were conducted to examine the effects of participants' free‐hand drawings on recognition accuracy and confidence for targets presented in a standard recognition paradigm and a lineup identification task. For both experiments, drawing a target influenced recognition accuracy and the confidence–accuracy correlation. In Experiment 1, the confidence–accuracy correlation was higher for participants completing a drawing than controls. Experiment 2 examined the drawings in relation to participants' decision to choose from the lineups. Once choosing was statistically controlled, the confidence–accuracy correlation for drawers was not higher than controls. These results suggest that the drawing influences the confidence–accuracy correlation by decreasing the likelighood of erroneously rejecting a target‐present lineup. Copyright © 2002 John Wiley & Sons, Ltd.
Memory for television advertisements as a function of advertisement–programme congruity
Authors: Furnham Adrian , Bergland Jenny , Gunter Barrie
Published: October 2002

An experiment tested memory for a beer advertisement (placed either at the beginning or the end of the centre advertisement break) within four programme contexts featuring beer drinking either before and after, before or after the centre break, or not at all. The relationship between subjective audience evaluation of the programme and memory for advertisements was also investigated. The sample consisted of students (N = 79) aged 17 to 26 years. Brand recognition of the beer advertisement was significantly related to programme content, showing memory for the advertisement being enhanced when relevant programme material followed the break. Congruent material shown before the centre break had the reverse effect of impairing memory for the advertisement. Increased levels of programme involvement were found to be associated with improved recall and recognition of embedded advertisements but higher rated ‘happiness’ of the programme was associated with poorer memory for advertisement content. Copyright © 2002 John Wiley & Sons, Ltd.
Adaptive inverse control of unmodeled stable SISO and MIMO linear systems
Authors: Plett Gregory L.
Published: October 2002

Adaptive‐signal‐processing techniques have been employed with great success in such applications as: system identification, channel equalization, statistical prediction and noise/echo cancellation. From a mathematical point of view, there is little difference between these applications and the types of operations required by control systems to control a dynamical system. This paper presents an approach to control systems calledadaptive inverse controlin which adaptive‐signal‐processing techniques are used throughout.

Adaptive inverse control comprises three simultaneous processes. The plant is automatically modeled using adaptive system identification techniques. The dynamic response of the system is adaptively controlled using the resulting model and methods related to channel equalization. Adaptive disturbance canceling is performed using methods similar to noise canceling.

The method applies directly to stable single‐input single‐output (SISO) and multi‐input multi‐output (MIMO) plants, and does not require ana priorimodel of the system. If the plant is unstable, it must first be stabilized using conventional feedback. This implies that at least a rudimentary model need be made if the plant is unstable. Once the plant is stabilized, adaptive inverse control may be applied to the stabilized system. Copyright © 2002 John Wiley & Sons, Ltd.
Self‐tuning PID controller using δ‐model identification
Authors: Bobál Vladimír , Sysel Martin , Dostál Petr
Published: October 2002

This contribution presents an application of a self‐tuning digital PID controller for process control modelled by δ‐models. The process is identified by the regression (ARX) model using the recursive least‐squares method (RLSM) with LD decomposition and applied directional forgetting. Controller synthesis is designed on the basis of a modified Ziegler–Nichols criterion for digital PID control loops. The ultimate (critical) proportional gain and period of oscillations have been derived for the second‐order δ‐model. Control results obtained using digital PID controller on the basic δ‐models and z‐models are compared. Copyright © 2002 John Wiley & Sons, Ltd.