bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving TCP performance over mobile networks
Authors: Elaarag Hala
Published: October 2002

Transmission Control Protocol
(TCP) is the most commonly
used transport protocol on the Internet. All indications assure
that mobile computers and their wireless communication links will
be an integral part of the future internetworks. In this paper, we
present how regular TCP is well tuned to react to packet loss in
wired networks. We then define mobility and the problems associated
with it. We discuss why regular TCP is not suitable for mobile
hosts and their wireless links by providing simulation results that
demonstrate the effect of the high bit error rates of the wireless
link on TCP performance. We discuss and illustrate the problems
caused by the mobility of hosts using a graph tracing packets
between fixed and mobile hosts. We then present a survey of the
research done to improve the performance of TCP over mobile
wireless networks. We classify the proposed solutions into three
categories: link layer, end-to-end and split. We discuss the
intuition behind each solution and present example protocols of
each category. We discuss the protocols functionality, their
strengths and weaknesses. We also provide a comparison of the
different approaches in the same category and on the category
level. We conclude this survey with a recommendation of the
features that need to be satisfied in a standard mobile TCP
protocol.
Comparison of three machine-learning methods for Thai part-of-speech tagging
Authors: Murata Masaki , Ma Qing , Isahara Hitoshi
Published: October 2002

The elastic-input neuro-tagger and hybrid tagger, combined with a neural network and Brill's error-driven learning, have already been proposed to construct a practical tagger using as little training data as possible. When a small Thai corpus is used for training, these taggers have tagging accuracies of, respectively, 94.4% and 95.5% (accounting only for the ambiguous words that relate to the parts of speech). In this study, in order to construct more accurate taggers, we developed new tagging methods using three different machine-learning approaches: the decision list, maximum entropy, and the support vector machine methods. We then performed tagging experiments using them. Our results show that the support vector machine method has the best precision (96.1%), and that it is capable of improving the accuracy of tagging in the Thai language. The improvement in accuracy was also confirmed by using a statistical test (a sign test). Finally, we examined theoretically all these methods in an effort to determine how the improvements were achieved. We found that the improvements were due to our use of word information, which is helpful for tagging, and a support vector machine that performed well.
Old dogs and new tricks
Authors: Nelson H. James , Armstrong Deborah J. , Ghods Mehdi
Published: October 2002

A compact OO course teaches the expert procedural programmer to "think" OO without falling back into old habits.
A modular technique for the design of efficient distributed leader finding algorithms
Authors: Korach E. , Kutten S. , Moran S.
Published: October 2002

A general, modular technique for designing efficient leader finding algorithms in distributed, asynchronous networks is developed. This technique reduces the problem of efficient leader finding to a simpler problem of efficient serial traversing of the corresponding network. The message complexity of the resulting leader finding algorithms is bounded by [f(n) +n)(log2k+ 1) (or (f(m) +n)(log2k+ 1)], wherenis the number of nodes in the network [mis the number of edges in the network],kis the number of nodes that start the algorithm, andf(n) [f(m)] is the message complexity of traversing the nodes [edges] of the network. The time complexity of these algorithms may be as large as their message complexity. This technique does not require that the FIFO discipline is obeyed by the links. The local memory needed for each node, besides the memory needed for the traversal algorithm, is logarithmic in the maximal identity of a node in the network. This result achieves in a unified way the best known upper bounds on the message complexity of leader finding algorithms for circular, complete, and general networks. It is also shown to be applicable to other classes of networks, and in some cases the message complexity of the resulting algorithms is better by a constant factor than that of previously known algorithms.
Regulatory Principles of Developmental Signaling
Authors: Freeman M. , Gurdon J. B.
Published: October 2002

▪ Abstract  Signaling between cells is a widely used mechanism by which cell fate and tissue patterning is determined in development. We review the mechanisms by which signaling between cells is regulated so that a cell receives the right amount of signal, at the right time, to achieve its intended developmental fate and position. In nearly all cases, we find that the supply of signal factor (ligand) is the limiting step in initiating a signaling process. Ligand supply is regulated by the transcription and localization of RNA, the spread of ligand from a source, and by inhibitors that operate at several different levels. We emphasize the different regulatory strategies that operate for threshold as opposed to concentration-dependent (morphogen) signaling. Threshold signaling is extensively regulated by feedback mechanisms. Morphogen signaling is regulated quantitatively by receptor loading and transduction flow.
Control of Developmental Timing by MicroRNAs and Their Targets
Authors: Pasquinelli Amy E. , Ruvkun Gary
Published: October 2002

▪ Abstract  In Caenorhabditis elegans the timing of many developmental events is regulated by heterochronic genes. Such genes orchestrate the timing of cell divisions and fates appropriate for the developmental stage of an organism. Analyses of heterochronic mutations in the nematode C. elegans have revealed a genetic pathway that controls the timing of post-embryonic cell divisions and fates. Two of the genes in this pathway encode small regulatory RNAs. The 22 nucleotide (nt) RNAs downregulate the expression of protein-coding mRNAs of target heterochronic genes. Analogous variations in the timing of appearance of particular features have been noted among closely related species, suggesting that such explicit control of developmental timing may not be exclusive to C. elegans. In fact, some of the genes that globally pattern the temporal progression of C. elegans development, including one of the tiny RNA genes, are conserved and temporally regulated across much of animal phylogeny, suggesting that the molecular mechanisms of temporal control are ancient and universal. A very large family of tiny RNA genes called microRNAs, which are similar in structure to the heterochronic regulatory RNAs, have been detected in diverse animal species and are likely to be present in most metazoans. Functions of the newly discovered microRNAs are not yet known. Other examples of temporal programs during growth include the exquisitely choreographed temporal sequences of developmental fates in neurogenesis in Drosophila and the sequential programs of epidermal coloration in insect wing patterning. An interesting possibility is that microRNAs mediate transitions on a variety of time scales to pattern the activities of particular target protein-coding genes and in turn generate sets of cells over a period of time. Plasticity in these microRNA genes or their targets may lead to changes in relative developmental timing between related species, or heterochronic change. Instead of inventing new gene functions, even subtle changes in temporal expression of pre-existing control genes can result in speciation by altering the time at which they function.
In Vivo Evidence for a Role of Toll-Like Receptor 4 in the Development of Intimal Lesions
Authors: Vink Aryan , Schoneveld Arjan H. , van der Meer Jelger J. , van Middelaar Ben J. , Sluijter Joost P.G. , Smeets Mirjam B. , Quax Paul H.A. , Lim Sai Kiang , Borst Cornelius , Pasterkamp Gerard , de Kleijn Dominique P.V.
Published: October 2002

Background—

Inflammation plays an important role in atherogenesis. The toll-like receptor 4 (TLR4) is the receptor for bacterial lipopolysaccharides and also recognizes cellular fibronectin and heat shock protein 60, endogenous peptides that are produced in response to tissue injury. To explore a possible role for this receptor in arterial obstructive disease, we determined the expression of TLR4 in the atherosclerotic arterial wall, including adventitia, and studied the effect of adventitial TLR4 activation on neointima formation in a mouse model.

Methods and Results—

Localization of TLR4 was studied in human atherosclerotic coronary arteries by immunohistochemistry and detected in plaque and adventitia. In the adventitia, not all TLR4-positive cells colocalized with macrophages. In primary human adventitial fibroblasts, expression of TLR4 was demonstrated by immunofluorescence, Western blot, and reverse transcriptase-polymerase chain reaction. Adding lipopolysaccharide to these fibroblasts induced activation of NF-κB and an increase of mRNAs of various cytokines. The effect of adventitial stimulation of TLR4 was studied in a mouse model. A peri-adventitial cuff was placed around the femoral artery. Application of lipopolysaccharide between cuff and artery augmented neointima formation induced by the cuff (intimal area±SEM, 9134±1714 versus 2353±1076 μm
2
,
P
<0.01). In TLR4-defective mice, application of cuff and lipopolysaccharide resulted in a smaller neointima than in wild-type mice (intimal area, 3859±904 μm
2
,
P
=0.02 versus wild type).

Conclusions—

A functional TLR4 is expressed in human adventitial fibroblasts and macrophages. Adventitial TLR4 activation augmented neointima formation in a mouse model. These results provide evidence for a link between the immune receptor TLR4 and intimal lesion formation.
French Sociology and Time: Origin, Development, and Current Research
Authors: Gadéa Charles , Lallement Michel
Published: October 2002

For French sociology, time has never been the central subject of an independent field of research. Without being neglected, the theme of time remains nevertheless on the fringe. In this field, there are neither networks nor academic journals which are well recognized. If we exclude Temporalistes (a journal which appeared for the first time in 1984 but whose circulation remains private), we have no journal similar to Time and Society, a first class academic showcase for the promotion and recognition of work devoted to its theme.The division of work in the French scientific community is used to this absence of visible evidence; time is a subject of research in different fields: work, education, health and organisations, without the various threads ever being woven together to produce a framework of coherent analysis.
Surface Centres for CO Adsorption on Supported Platinum
Authors: Sarbak Zenon
Published: October 2002

Adsorption centres of platinum supported on low- and high-surface area γ-Al2O3 (LSA and HAS, respectively), as well as on SiO2, are described. The interaction between platinum and CO was characterised and the platinum dispersion determined.
Comparison between Different Keratin-composed Biosorbents for the Removal of Heavy Metal Ions from Aqueous Solutions
Authors: Banat Fawzi , Al-Asheh Sameer , Al-Rousan Dheaya‘
Published: October 2002

This study examined and compared the ability of chicken feathers, human hair and animal horns, as keratin-composed biosorbents, for the removal of Zn2+ and Cu2+ ions from single metal ion aqueous solutions under different operating conditions. The three biosorbents investigated in this study were all capable of adsorbing Zn2+ and Cu2+ ions from aqueous solutions. The biosorbent showing the highest uptake of Zn2+ and Cu2+ ions was animal horns. Chicken feathers showed a higher Cu2+ ion uptake and a lower Zn2+ ion compared to human hair. Increasing the initial concentration of Zn2+ or Cu2+ ions, or increasing the initial pH value, increased the metal ion uptake. Such uptake decreased when the temperature was raised from 25°C to 50°C for all adsorbent/metal ion combinations except for Zn2+ ion/human hair where the uptake increased with temperature. It was demonstrated that the addition of NaCl salt to the metal ion solution depressed the metal ion uptake. The Freundlich isotherm model was found to be applicable to the adsorption data for Cu2+ and Zn2+ ions.
Secondary chemistry of cultured mycobionts: formation of a complete chemosyndrome by the lichen fungus of Lobaria spathulata
Authors: Stocker-Wörgötter Elfie , Elix John A.
Published: October 2002

The study aimed to optimize culture conditions and nutrient requirements for theproduction of secondary metabolites by the cultured mycobiont Lobaria spathulata. This species proved to be an excellent model system for such studies, as the complete chemosyndromefound in the natural lichen thallus was repeatedly formed in the cultured mycobiont with differentiated, aerial mycelia. Nutrient media containing the disaccharide, sucrose, were found to favour both rapid growth and the production of typical lichen substances. Higher proportions of the secondary compounds were detected in the developing mycobiont than in mature lichen thalli.
Stratigraphic Context of Old Crow Tephra, Holitna Lowland, Interior Southwest Alaska
Authors: Waythomas Christopher F. , Lea Peter D. , Walter Robert C.
Published: October 2002

A thick deposit of Old Crow tephra was discovered in a bluff exposure along the middle Holitna River near the Kulukbuk Hills (61°20′N latitude, 157°10′W longitude) in interior southwest Alaska. This locality is the southwesternmost-known deposit of Old Crow tephra in Alaska. Thickness and grain-size data from this site support a source volcano in the eastern Aleutian arc. Pleistocene stratigraphic sequences in the lowland are dominated by upward-fining eolian sand-sheet deposits and loess separated by organic silt. These deposits record at least two episodes of regional glaciation and an intervening nonglacial period (marine oxygen isotope stage 3, stage 5, or both). Old Crow tephra crops out near the top of the lower upward-fining eolian unit, indicating that the ash erupted near the end of an interval of periglacial eolian sedimentation. The sequence of eolian deposits that contain Old Crow tephra probably accumulated during the latter part of marine oxygen isotope stage 6, whereas the overlying eolian sequence formed during the last glaciation (stage 2). This stratigraphic position is consistent with other stratigraphic contexts for the tephra and with fission-track and thermoluminescence ages of ca. 140,000 ± 10,000 yr B.P.
Holocene Coral Reef Terraces and Coseismic Uplift of Huon Peninsula, Papua New Guinea
Authors: Ota Y. , Chappell J. , Kelley R. , Yonekura N. , Matsumoto E. , Nishimura T. , Head J.
Published: October 2002

As many as six levels of emerged Holocene coral terraces occur along 40 km of coastline on the Huon Peninsula, Papua New Guinea, recording uplift history since culmination of the postglacial transgression. The Holocene reef crest, ca. 6000 yr B.P., is tilted down to the northwest, parallel to the coast and concordant with the deformation of the last interglacial coral reef terrace, and descends from 23 to 12 m in the study area. The pattern and rate of deformation have been uniform in the late Quaternary because average uplift rates have remained the same since the last interglaciation. The Holocene terraces described here are erosional features with regressive encrusting corals, developed upon the Holocene transgressive reef. The multiple levels represent episodic, probably coseismic uplift, which has occurred repeatedly in the last ca. 6000 yr. Significant longshore variation in the age of the lowest terrace, from 1700 to 2500 yr B.P., suggests independent coseismic uplift on different sectors of the coast. This is supported by age-height relationships of the higher Holocene terraces. Nonlinear uplift during the Holocene, with recurrence intervals increasing toward the present, is clearly recorded by the regressive terraces in each subregion. Some of the Holocene regressive terraces grade laterally into fluvial terraces capped with debris-flow deposits, probably reflecting seismically triggered mass movement.
Discriminant Function Analysis of Glass Chemistry of New Zealand and North American Tephra Deposits
Authors: Shane Philip A.R. , Froggatt Paul C.
Published: October 2002

Major, trace, and rare earth element analyses of volcanic glass are used separately or in combination for correlating Quaternary tephras, often by graphical or simple comparative methods. We have taken a statistical approach using discriminant function analysis (DFA) to assess the relative discriminating power of the different elements in volcanic glasses from several tectonovolcanic provinces. We found that major oxides are powerful discriminating variables for widespread tephras from the Taupo Volcanic Zone in New Zealand and here they can be more discriminating than trace elements. A wide selection of tephras from the western United States can also be distinguished on major oxides alone, particularly those from Cascade Range volcanoes. For tephras from large intracontinental calderas, such as Long Valley or Yellowstone, REE and trace elements are more effective at discriminating than major oxides. However, tephras erupted from the Long Valley area can be distinguished on major oxide composition by DFA, despite their similar chemistry. The selection and relative significance of different elements for discriminating tephras depends on the total data set being compared, as well as the source volcano and the individual eruptive events. Caution must be exercised in the nonstatistical selection of compositional data for characterizing tephras: DFA is a more powerful and objective tool for the comparison of tephra chemistry.
Growth of an Intermittent Ice Sheet in Iceland during the Late Pliocene and Early Pleistocene
Authors: Geirsdóttir Áslaug , Eiríksson Jón
Published: October 2002

Deep-sea paleoclimatic records show that the Quaternary climate around Iceland was, and probably still is, very sensitive to rapid shifts in North Atlantic oceanic circulation. Studies of several key sections in Iceland indicate that similar oscillations are reflected in the late Pliocene and early Pleistocene terrestrial stratigraphy. Correlations between six rock sequences in western, northern, eastern, and southern Iceland show a fairly distinct trend during the Pliocene-Pleistocene transition indicating the progressive growth of an ice sheet from southeast toward the north and west. The correlations are based on K/Ar dates and paleomagnetic studies. A total of 11 glacial horizons are recorded in a stratigraphic column from eastern Iceland extending back 6.5 myr. In western Iceland, 7 glacial horizons are preserved in a rock section dated from 7.0 to 1.8 myr, and in northern Iceland 14 glacial horizons are identified in a section that extends back to 9.0 myr. Well over 20 glacial horizons have been identified in the stratigraphic column in Iceland. Full-scale glacial-interglacial cyclicity with regional ice cover is indicated at approximately 2.6 myr. A further amplification leading to islandwide glaciations is identified at 2.2-2.1 myr. These results show that changes in the ice cover in Iceland correlate with the deep-sea oxygen isotope records from benthic and planktonic foraminifera as well as IRD studies from the North Atlantic.
Assemblage Data and Bone and Teeth Modifications as an Aid to Paleoenvironmental Interpretations of the Open-Air Pleistocene Site of Tighenif (Algeria)
Authors: Dauphin Yannicke , Kowalski Casimir , Denys Christiane
Published: October 2002

Variations in the proportions of the various groups of Rodentia collected from eight stratigraphic levels at Tighenif had previously been interpreted as representing environmental (climatic) changes. However, the processes involved in the formation of assemblages are still not well understood. Examination of fragmentation, crystallinity, and chemical composition of fossil bones and teeth, compared to recent samples, shows that a possible explanation for the variations in frequencies is the differential preservation of skeletal remains. Thus, the evaluation of postmortem effects is essential in determining the accuracy of the fossil record. The abundance and composition of remains are governed by the complex interaction of many factors. As indicated by actualistic studies, direct deductions from fauna lists must be avoided as much as possible.
Thirty Thousand Years of Vegetation Changes in the Alabama Hills, Owens Valley, California
Authors: Koehler Peter A. , Anderson R.Scott
Published: October 2002

Twenty packrat (Neotoma) middens recovered from three sites (1265-1535 m) in the Alabama Hills, Inyo County, California, provide a ca. 31,450-yr record of vegetation change. Located ca. 7 km east of the Sierra Nevada, the middens document that Utah juniper (Juniperus osteosperma), Joshua tree (Yucca brevifolia), and bitterbush (Purshia tridentata) occupied the site between 31,450 and 19,070 yr B.P. Joshua tree and bitterbush departed by ca. 17,760 yr B.P., with cliffrose (Purshia mexicana) and joint-fir (Ephedra viridis) appearing. By 13,350 yr B.P., blackbush (Coleogyne ramosissima) and cholla (Opuntia echinocarpa) entered the record. Between 9540 and 7990 yr B.P., Utah juniper and other species now extralocal to the sites departed and modern components such as wolfberry (Lycium andersonii) and rubber rabbitbrush (Chrysothamnus teretifolius) appeared. The middle Holocene records little variation in plant macrofossil composition; however, pollen analysis reflects an increase in aquatic pollen types which might suggest more-open conditions. The transition to the modern vegetation associations at the sites occurred after ca. 2800 yr B.P. The record from the Alabama Hills correlates well with that of other regional vegetation data but documents conditions of increasing aridity earlier than many other packrat midden sites. A shift in understory vegetation between 19,070 and 17,760 yr B.P. may reflect a transition from glacial maximum to post-maximum conditions in the eastern Sierra Nevada.
Holocene Environmental Change and River-Mouth Sedimentation in the Baie des Anges, French Riviera
Authors: Dubar Michel , Anthony Edward J.
Published: October 2002

River mouths on the steep, high-relief coast of the French Riviera exhibit thick sequences of Holocene marine, estuarine, deltaic, and river channel-floodplain sediments that overlie basal fluvial Pleistocene gravel. Gravel is uncommon in most of the early to middle Holocene aggradational-progradational marine, estuarine, deltaic sediments, despite an ample supply from rock units in the steep adjoining uplands. River-mouth gravel is common only in late Holocene river channels and in barrier beaches perched on finer-grained nearshore sediments. Neither downslope grain-size fining on alluvial fans nor sediment stacking patterns during sea-level (base-level) rise readily account for the lack of early to middle Holocene gravel in the river-mouth sediment wedges. Holocene sea-level rise led to the storage of fine-grained sediments in shallow marine, estuarine, and deltaic environments in the present coastal zone. We infer that humid temperate conditions, a dense forest cover, landscape stabilization, and a regular quiescent river flow regime associated with the Atlantic climatic optimum limited gravel supply in the adjoining catchments and gravel entrainment downstream during the early Holocene. Sea-level stabilization in the middle and late Holocene coincided with a marked change in bioclimatic conditions toward the present Mediterranean-type regime, which is characterized by a less dense forest cover, soil erosion, and episodic catastrophic floods. The late Holocene was thus a time of downstream bedload channel aggradation, fine-grained floodplain and paludal sedimentation, and seaward flushing of clasts leading to the formation and consolidation of the gravel barrier beaches that bound the rivermouths and embayments.
Influence of Changing Atmospheric Circulation on Precipitation δ18O–Temperature Relations in Canada during the Holocene
Authors: Edwards Thomas W.D. , Wolfe Brent B. , Macdonald Glen M.
Published: October 2002

Postglacial precipitation δ18O history has been reconstructed for two regions of Canada. Long-term shifts in the oxygen-isotope composition of annual precipitation (δ18Op) in southern Ontario appear to have occurred with a consistent isotope–temperature relation throughout the past 11,50014C yr. The modern isotope–temperature relation in central Canada near present boreal treeline evidently became established between 5000 and 4000 years ago, although the relation during the last glacial maximum and deglaciation may also have been similar to present. In the early Holocene, however, unusually high δ18Opapparently persisted, in spite of low temperature locally, probably associated with high zonal index. A rudimentary sensitivity analysis suggests that a small reduction in distillation of moisture in Pacific air masses traversing the western Cordillera, perhaps accompanied by a higher summer:winter precipitation ratio, could have been responsible for the observed effect. Equivalent isotope–temperature “anomalies” apparently occurred elsewhere in western North America in response to changing early-Holocene atmospheric circulation patterns, suggesting that a time-slice map of δ18Opfor North America during this period might provide a useful target for testing and validation of atmospheric general circulation model simulations using isotopic water tracers.
Late-Holocene Expansion of Eastern Larch (Larix laricina[Du Roi] K. Koch) in Northwestern Québec
Authors: Peñalba M. Cristina , Payette Serge
Published: October 2002

The Holocene expansion of eastern larch (Larix laricina[Du Roi] K. Koch) at the edge of its geographical range in northwestern Québec was reconstructed using pollen and macrofossils from peat deposits. BecauseLarixis a poor pollen producer, the total pollen sum of 300–500 grains per spectrum was supplied by an additional survey of 2000 grains. However, the use of 2000 pollen counts did not give a betterLarixrecord. The combination of both pollen and macrofossil analyses offered greater opportunities to estimate the time of arrival of eastern larch at the edge of its distributional range. Along the study transect, eastern larch established east of 75° W long before 2000 yr B.P. but not sooner than 5000 yr B.P., whereas it arrived much later, after 1500 yr B.P., in most sites west of 75° W within a migration corridor around 57° 45′ N. The macrofossil record is completely different between the eastern sites, with high frequencies and densities, and the western sites where larch occurs sporadically with few remains only, concentrated in the upper part of the peat profiles. The colonization pattern of eastern larch was patchy in time and space, as suggested by the available macrofossil records, present distributional pattern in the area, and age structure of extant populations. The establishment of disjunct larch populations in the westernmost sites most likely proceeded from long-distance transport. The spatial–temporal pattern of eastern larch west of 74° W may have been influenced by the site conditions associated with late deglaciation in central northern Québec.
Ostracode Geochemical Record of Holocene Climatic Change and Implications for Vegetational Response in the Northwestern Alaska Range
Authors: Hu Feng Sheng , Ito Emi , Brubaker Linda B. , Anderson Patricia M.
Published: October 2002

Trace-element analysis of the calcareous shells of ostracodes in a sediment core from Farewell Lake provides the first limno-geochemical record for climatic reconstructions in Alaska. When compared with pollen data from the same site, this record offers new insights into climatic controls over vegetation dynamics during the Holocene. The low Mg/Ca ratios and high Sr/Ca ratios suggest that a relatively cold dry climate prevailed in this region between 11,000 and 9000 yr B.P. (uncalibrated14C ages are used throughout the paper). This result contrasts with previous interpretations of a thermal maximum at this time, corresponding to the widespread establishment ofPopuluswoodland/forest. The trace-element record suggests, instead, that the warmest period of the early Holocene at Farewell Lake was between 8500 and 8000 yr B.P. during the decline ofPopulus.Marked decreases in Sr/Ca and Mg/Ca suggest a major increase in effective moisture around 6500 yr B.P., which coincided with the establishment ofPiceaboreal forests in the Farewell Lake region. This climatic change was probably widespread throughout much of Alaska and adjacent Canada and might have induced the rapid spread ofAlnusand the shift fromPicea glaucatoP. marianadominance across that region. Our geochemical record also suggests that the late-Holocene climate history was more complex than previously thought on the basis of palynological studies. According to this record, growing-season temperatures increased 6000–4500 yr B.P., decreased 4500–1500 yr B.P., and increased with fluctuations afterward. After 6000 yr B.P. stratigraphic changes in pollen percentages ofPiceaappear to be positively related with those of Mg/Ca. This relationship implies that once the threshold of effective moisture was crossed for the establishment ofPiceaforests temperature was the primary control ofPiceapopulation density.
Late Quaternary Variations in the Level of Paleo-Lake Malheur, Eastern Oregon
Authors: Dugas Daniel P.
Published: October 2002

The highest shoreline features of paleo-Lake Malheur are undated gravelly barrier beaches south of Harney Lake that lie ca. 3.5 m higher than the hydrographic outlet of Harney Basin at Malheur Gap (1254 m). The earliest Quaternary record for Lake Malheur consists of occurrences of water-deposited tephra dated to ca. 70,000–80,000 yr ago. The next identified lake interval is dated by shells with ages of ca. 32,000 and 29,500 yr B.P. No dates are available for the terminal-Pleistocene Lake Malheur. Lake(s) were present between ca. 9600 and 7400 yr B.P., although periodic low levels or desiccation are suggested by a paleosol dated as ca. 8000 yr B.P. The lake system probably dried further after 7400 yr B.P., although dates are lacking for the period between ca. 7400 and 5000 yr B.P. Dune deposits on the lake floor are ca. 5000 yr old and indicate generally dry conditions. Fluctuating shallow lakes have probably characterized the last 2000 years. A date of 1000 yr B.P. gives a maximum age for beach deposits at 1254 m, near the basin threshold elevation. Thus, the Malheur Lake system may have drained to the Pacific Ocean by way of Malheur Gap during the latest Holocene.
Integrating Stalagmite, Vertebrate, and Pollen Sequences to Investigate Holocene Vegetation and Climate Change in the Southern Midwestern United States
Authors: Denniston Rhawn F. , Gonzalez Luis A. , Semken Holmes A. , Asmerom Yemane , Baker Richard G. , Recelli-Snyder Heather , Reagan Mark K. , Bettis E. Arthur
Published: October 2002

Speleothem carbon and oxygen isotopic records from Onondaga Cave, south-central Missouri, and Beckham Creek Cave, north-central Arkansas, are compared with the Cupola Pond and Oldfield Swamp pollen series from southeastern Missouri and the Rodgers Shelter and Modoc Shelter vertebrate biostratigraphic sequences from central Missouri and southwestern Illinois. Similar, and roughly contemporaneous, shifts between deciduous forest and steppe indicators throughout the Holocene are revealed in each database. These independent proxies record steppe conditions between approximately 9000 and 1500 cal yr B.P. A shift toward lighter speleothem carbon may reflect a change from warm and dry to cool and dry conditions between 4500 and 3000 yr B.P. The sensitive response of speleothem δ13C to changes in vegetation emphasizes their importance as paleoclimate records in an area containing few other millenial-scale climate proxies.
Mollusk Record of Monsoon Variability during the L2–S2 Cycle in the Luochuan Loess Sequence, China
Authors: Rousseau Denis-Didier , Wu Naiqin
Published: October 2002

Molluscan changes that occurred in China over the S2–L2 upper middle Pleistocene series may be caused by monsoon variation. Study of terrestrial mollusks from the loess sequence in Luochuan, gathered in ecological groups according to the moisture and temperature requirements of the identified species, indicates alternating strengthened summer and winter paleomonsoons between 130,000 and 244,000 yr. The four occurrences of species, currently distributed in S.E. China in the sequence, indicate that the climate conditions were warmer and wetter than today between about 242,000 and 233,000 yr, at about 210,000, 164,000, and 140,000 yr. The main occurrence of xerophilous taxa at about 180,000, 154,000, and 138,000 yr is interpreted as indicating a drier environment than today. Such suggestions are in agreement with other proxy data such as grain size distribution. Higher numbers of individuals in the different ecological groups from the S2–L2 sequence indicate more favorable general environmental conditions than in the youngest S1–L1. This may agree with an increase in the regional aridity, since 500,000 yr, deduced from the study of the eolian flux in the northwestern Pacific downwind from China.
The Composite Nature of the Provo Level of Lake Bonneville, Great Basin, Western North America
Authors: Sack Dorothy
Published: October 2002

Deposits of a transgressive-phase Lake Bonneville stillstand or oscillation are found just below the elevation of the regressive-phase Provo shoreline at numerous exposures throughout the Bonneville basin. Existence of these subProvo shoreline deposits provides a new explanation for the massive size of Provo depositional and erosional landforms, which can no longer be explained by a long stillstand at the Provo shoreline. Provo coastal landforms are large because they are superimposed on subProvo landforms. Results also help to clarify divergent interpretations regarding the relative age of the Provo shoreline and the number of times it was occupied by the water plane. Occupation of approximately the same level during both the transgressive and the regressive phase of Lake Bonneville may be coincidental, or it may indicate that a bedrock sill controlled outflow at subProvo as well as Provo time. Rise to the Bonneville level could have occurred after massive slope failure plugged the outlet pass.
B plexins activate Rho through PDZ‐RhoGEF
Authors: Driessens Mariette H.E , Olivo Cristina , Nagata Koh-ichi , Inagaki Masaki , Collard John G
Published: October 2002

Plexins are receptors for the repulsive axon guidance molecules semaphorins. Previously, we have shown that plexin‐B1 binds activated Rac, but that clustering of plexin‐B1 causes Rho activation, resulting in stress fiber formation. Using the yeast two‐hybrid system, we found that the C‐terminus of B plexins interacted directly with Rho‐specific exchange factors, via their PDZ domain. Mutation of the carboxy‐terminal amino acids of plexin‐B1 or coexpression of a dominant negative PDZ‐RhoGEF abrogated the ability of plexin‐B1 to cause stress fiber formation. Our results demonstrate a role for PDZ‐RhoGEF in B plexin‐mediated activation of Rho/Rho kinase signaling, implicated in the regulation of axon guidance and cell migration.
Most of the structural elements of the globular domain of murine prion protein form fibrils with predominant β‐sheet structure
Authors: Jamin Nadège , Coı̈c Yves-Marie , Landon Céline , Ovtracht Ludmila , Baleux Françoise , Neumann Jean-Michel , Sanson Alain
Published: October 2002

The conversion of the cellular prion protein into the β‐sheet‐rich scrapie prion protein is thought to be the key step in the pathogenesis of prion diseases. To gain insight into this structural conversion, we analyzed the intrinsic structural propensity of the amino acid sequence of the murine prion C‐terminal domain. For that purpose, this globular domain was dissected into its secondary structural elements and the structural propensity of the protein fragments was determined. Our results show that all these fragments, excepted that strictly encompassing helix 1, have a very high propensity to form structured aggregates with a dominant content of β‐sheet structures.
N‐terminal acetylation of ectopic recombinant proteins in Escherichia coli
Authors: Charbaut Elodie , Redeker Virginie , Rossier Jean , Sobel André
Published: October 2002

N‐terminal acetylation is a protein modification common in eukaryotes, but rare in prokaryotes. Here, we characterized five mammalian stathmin‐like subdomains expressed in Escherichia coli by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and nanoESI Q‐TOF tandem mass spectrometry. We revealed that RB3SLD and RB3′SLD are Nα‐acetylated, whereas SCG10SLD and SCLIPSLD, although identical up to residue 6, are not, as well as stathmin. To assess the influence of the N‐terminal sequences on Nα‐acetylation, we exchanged residues 7 and 8 between acetylated RB3SLD and unacetylated SCG10SLD, and showed that it reversed the acetylation pattern. Our results demonstrate that ectopic recombinant proteins can be extensively Nα‐acetylated in E. coli, and that the rules governing Nα‐acetylation are complex and involve the N‐terminal region, as in eukaryotes.
Behavior of earnings, stock returns, accruals, and analysts' forecasts following negative annual earnings
Authors: Ettredge Michael , Toolson Richard , Hall Steve , Na Chongkil
Published: October 2002

This study documents the behavior of earnings, abnormal stock returns, analysts' earnings forecasts, and accounting accruals following years in which companies report negative annual earnings. Changes in accounting accruals (earnings minus operating cash flows) frequently are used as proxies for managerial manipulation of earnings numbers. Our evidence indicates that earnings typically increase sharply in the year following a loss. The earnings increases are due to improved operating cash flows, not to accounting “window dressing.” However, financial analysts expect even better earnings performance than the rebounding firms are able to provide. Investors also appear not to understand the post‐loss behavior of annual earnings. Therefore, the market commonly is disappointed by the earnings increases, and the result, on average, is negative excess stock returns. The excess returns are correlated with analysts' earnings forecast errors, which proxy for the market's failure to understand post‐loss earnings behavior.
Mergers and macro‐economic factors
Authors: Yagil Joseph
Published: October 2002

This study investigates the relationship between macro‐economic factors and the time pattern of the degree of merger activity in the U.S. economy. The results of the study imply that whether mergers are motivated by operating or financial synergy, they are closely related to macro‐economic factors. The findings also indicate that this relationship is stronger for pure conglomerate than for non‐conglomerate mergers, and that while the impact of the interest rate on “cash” mergers is positive, for “securities” mergers the impact is negative.
A nonparametric investigation of the 90‐day t‐bill rate
Authors: Barkoulas John T. , Baum Christopher F. , Onochie Joseph
Published: October 2002

We employ a nonlinear, nonparametric method to model the stochastic behavior of changes in the 90‐day U.S. T‐bill rate. The estimation technique is locally weighted regression (LWR), a nearest‐neighbor method, and the forecasting criteria are the root mean square error (RMSE) and mean absolute deviation (MAD) measures. We compare the forecasting performance of the nonparametric fit to the performance of two benchmark linear models: an autoregressive model and a random‐walk‐with‐drift model. The nonparametric fit results in significant improvements in forecasting accuracy as compared to benchmark linear models both in‐sample and out‐of‐sample, thus establishing the presence of substantial nonlinear mean predictability in the 90‐day T‐bill rate.
Effect of hydrodynamic and physicochemical changes on critical flux of milk protein suspensions
Authors: YOURAVONG WIROTE , GRANDISON ALISTAIR S. , LEWIS MICHAEL J.
Published: October 2002

The critical flux during ultrafiltration of whey protein concentrate and sodium caseinate suspensions was investigated. The weak form of critical flux was found for both suspensions. Critical flux of sodium caseinate was higher than that of whey protein concentrate. This could be due to the differences in particle size of the suspensions, resulting in a slower particle back transportation for small particles (whey proteins) compared to the larger casein micelles. Critical flux increased as crossflow velocity increased and decreased as concentration increased, suggesting that critical flux was determined by competition between rate of particle removal from the membrane surface and rate of particle movement towards the membrane surface. Influence of changing pH, addition of NaCl and CaCl2 on the critical fluxes of both protein suspensions was also studied. Increasing pH led to an increase in critical flux for both protein suspensions, suggesting that electrostatic repulsive forces are involved in determining critical flux in both cases. Addition of NaCl gave rise to a decrease in electrostatic interactions due to an increase in ionic strength and ζ potential, and resulted in a decrease in critical flux for sodium caseinate, but had no significant effect for whey protein concentrate. Addition of CaCl2 resulted in a decrease in the critical flux and had a more pronounced influence than NaCl. These results suggest that, in addition to electrostatic repulsive forces, other factors such as structure of protein may be involved in determining the critical flux.
Population dynamics of the shore crab Pachygrapsus marmoratus (Brachyura: Grapsidae) in the central Portuguese coast
Authors: Flores Augusto A.V. , Paula José
Published: October 2002

The population dynamics of the shore crab Pachygrapsus marmoratus was studied at two different rocky shores, Cabo Raso and Avencas, within the central Portuguese coast. The population structure at these shores, obtained by pooling monthly samples, revealed marked discrepancies. Unimodal, right-skewed size–frequency distributions at Avencas contrasts with the bimodal distributions obtained at Cabo Raso, corresponding to early recruits and larger adults. Recruitment timing and intensity together with habitat complexity are probable causes of the differences observed. At Cabo Raso an intense recruitment season was recorded from September to November, but very small juveniles were always present in samples. Monthly polymodal distributions are apparent but the size structure too complex to identify age groups through the sampling period. At Avencas, the influx of new juveniles is temporally restricted and year groups recognizable from main recruitment events taking place around October. Young-of-the-year crabs grow quickly to mature size and join the reproductive stock in the next breeding season from late March to early September in the study region. The growth pattern in both sexes follows a seasonal trend with minimum growth during the breeding months and maximum growth rates from late winter to early spring. Life span may reach four years, probably more in males. At Avencas, population maintenance seems to be highly dependent on favourable conditions promoting adequate settlement intensity and timing. Early recruitment is presumed to enhance the reproductive output of young-of-the-year individuals which comprise the bulk of breeding crabs. At Cabo Raso settlement rates are much higher and recruitment timing may be less critical since most breeding crabs belong to the 1-y+ class.
Habitat, behaviour and colour patterns of orange roughy Hoplostethus atlanticus (Pisces: Trachichthyidae) in the Bay of Biscay
Authors: Lorance Pascal , Uiblein Franz , Latrouite Daniel
Published: October 2002

Analyses of 13 submersible dives on the continental slope of the Bay of Biscay
(north-east Atlantic) showed that: (i) orange roughy formed dense aggregation of more than
4000 individuals per ha close to the bottom of a small underwater canyon. In all other study
areas only a few individuals were observed. Orange roughy aggregations are probably associated
with areas of high water mass movements and mixing; (ii) most individuals observed within this
aggregation or in its peripheral areas were behaviourally inactive and could be approached with
the submersible at close distance; (iii) a large number of these orange roughy showed a completely
pigmentless white, or weak red coloration, never observed from specimens caught in trawls.
Two individuals which were disturbed by the submarine changed from white to
the ‘typical’ red coloration.

These observations suggest fine tuning of the foraging strategy and life cycle of the species. It is speculated that, as an active predator of a sparse food resource, orange roughy has developed adaptations to exploit areas with specific hydrological conditions which offer high prey encounter rates and shelter during metabolic relaxation phases between foraging trips.
Distribution and bathymetric zonation of deep-sea brittle stars (Echinodermata: Ophiuroidea) off the Japanese Pacific coast
Authors: García Julio , Yeh Hsin-ming , Ohta Suguru
Published: October 2002

The distribution and bathymetric zonation of deep-sea ophiuroids off the Japanese Pacific coast were analysed. Samples were collected using beam trawls between depths of 60 and 6382 m. In 154 samples, 139 ophiuroid species were found. Data were clustered based on Morisita–Horn similarity index and a dendrogram was constructed. The Japanese Pacific coast can be divided in two major zones. One in the northern part off the Japanese Pacific coast, and another in the region off the central Japanese Pacific coast. In the northern region, five bathymetrical zones were detected at depths of 130–250, 300–500, 500–650, 1100–1500, and 2000–3000 m. In the central region, eight bathymetrical zones were detected at 100–140, 150–250, 200–300, 220–300, 300–400, 400–500, 800–1000, and 1000–1500 m depth. Representative species for each bathymetrical zone are reported.