1,721,110 research outputs found
Variations of Depositional Settings in the South China Sea: Implications Since the Late Neogene Sediments
No full textAbstract
The South China is the largest marginal sea in the western Pacific. It\ue2s unique geographic settings and high sedimentation rates preserve the paleo- climatic signals with larger amplitude than those from the open ocean. In this study, grain size and elemental compositions of the fine fractions (<63 mm) from the sediments collected by the ODP Leg 184 Sites 1143 and 1146 were analyzed to reconstruct the depositional settings for the last 8 My.
Particle size and elements analyses, in conjunction with the carbonate contents and sedimentation rates from core sediments, reflect the possible increase in precipitation, which was caused by the strengthened summer monsoon between 5 and 3 Ma. In addition to the grain sizes change from silt-domain to clay-domain, Ti/Al ratio of sediments increase while the Si/Al, Zr/Al, and K/Al ratios decrease, which could be related to the enhanced sediments input through rivers. These environmental changes could be attributed to the uplift of Tibet plateau and the formation of Western Pacific Warm Pool. On the contrary, the impact of climate changes is not evident in the loess plateau in the northwestern China. It is likely that the climate in the South China Sea became warm and humid from 5 to 3 Ma were regional changes.
Key words: Grain size, element analyses, South China Sea, summer monsoo
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Geochemistry of Uranium and Thorium Isotopes in Marine Sediments off Taiwan and Northern South China Sea
No full textUranium and thorium radionuclides were measured on two gravity cores (T17G and T18G) and one box core (T19B) collected from the western South Okinawa Trough (SOT), one gravity core from off shore Southwest Taiwan (N3) and three box cores (C, D and E) from the northern South China Sea (SCS) in order to examine the variations of these radionuclides and their activity ratios in the sediments of the areas and to characterize the source function of the sediments and their geochemical implication based on these nuclides. For long half-life radionuclides such as 238U, 234U, 232Th and 230Th, the activities in the cores of the SOT and Southwest Taiwan areas show no significant vertical or areal variations, implying no significant variation in sediment supply or depositional environment within the past 100 years. The average activity of 238U is 1.65 dpm/g and 1.33 dpm/g in the SOT and Southwest Taiwan areas, respectively, and that of 232Th is 3.57 dpm/g and 3.34 dpm/g, respectively. The average activities of 238U and 232Th are, respectively, 1.37 dpm/g and 2.37 dpm/g in the SCS. The mean 232Th activity is lower in the SCS than in the SOT and Southwest Taiwan. The mean 232Th activity of the sediments in the SOT and Southwest Taiwan is quite comparable to that of the shale, slate and black schist in Taiwan, suggesting that these sediments are the terrigenous detrial materials from Taiwan. The 238U and 234U activities in the cores of these two areas show no significant vertical nor areal variations with activities ranging between 1.3 and 2 dpm/g, and their 234U /238U activity ratios being about 1.1, quite close to that of seawater (1.14).
Since 238U and 234U are quite comparable among the three areas, the
higher activity of 230Th in excess over 234U in the northern SCS may be due to greater water depth that allows more 234U produced 230Th to be scavenged from the water column.
The uranium and thorium radionuclides and their activity ratios in the SOT and Southwest Taiwan sediments suggest that these sediments are the terrigenous detrial materials from Taiwan. The source function of the SCS sediments is more complex than that of the above-mentioned sediments
Living (Rose Bengal Stained) Benthic Foraminifera in Sediments off the Southwest Taiwan
No full textThe objective for this study was to provide the insight into the link between benthic foraminiferal assemblages and the surrounding environment. Stained sediment samples were collected from the continental shelf and slope off the southwest Taiwan, including the Kao-ping Submarine Canyon. In addition to faunal census, total organic carbon (TOC), carbonate, and coarse fraction of the sediments were also measured. Nevertheless, the downcore record of the excess 210Pb from selected sites offers the constraint for stratigraphy time frame for discussion.
The benthic foraminiferal assemblages were analyzed by statistics. Clusters analysis shows that all species present in this study could be divided into two groupings. One is those distributed in outer shelf and the other is those found in the inner shelf of the southwest Taiwan. Different from previous studies, the spatial distribution of stained benthic foraminifera seems not to be related with TOC contents in the sediment and water depth. Both the diversity index and Eqitability show that sites inside of the canyon have lower values. The higher Living/Total ratios and lower dead tests at the head of Kao-ping Submarine Canyon than adjacent area might be the effect of migration. Furthermore, the species within the canyon are similar to the southern and northern continental shelf. These findings indicate that the spatial distribution of benthic forams within canyon might be the effect of transport, which could result from the complex interaction between tides and currents.
Augmented with the profiles of excess 210Pb, the temporal variation of benthic foraminifera was revealed. Generally there is a progressive decrease in the abundance of Ammonia sp.. It is possible that the diminishing trend was caused by the increase of anthropogenic activity for the last 30 years
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Seasonal Variations of the Planktonic Foraminiferal Assemblages and Stable Isotopic Compositions: Sediment Trap Results from the Kao-ping Submarine Canyon and Northern South China Sea
No full textAbstract
The carbon and oxygen isotopes of planktonic foraminifera, faunal assemblage, and coarse fraction of trap materials were analyzed in this study. The sediment traps were deployed in two lacations. One was in the Kao-ping submarine canyon and the other was in the northern South China Sea.
Variations of the individual concentrations from Kao-ping submarine canyon are small throughout the deployment interval except for the period when the Typhoon Chi-Te invaded southern Taiwan in July 2000. The results that benthic foraminifer abundances (#/g) are higher than that of planktonic foraminifera after typhoon invasion reflect the influence of particle settling by lateral transport. In addition, the major planktonic foraminifera found in canyon are Globigerinoides aequilateralis, Globigerinoides ruber, Globigerinoides sacculifer, and Neogloboquadrina dutertrei. At the same time, we also found Globigerina bulloides that usually lives in the high latitudes and cold temperature. It reveals the effect of nutrient supply along coastal region.
The coarse fraction contents and foraminiferal abundances collected by the traps in the northern South China Sea are both increasing in January and March. It could be associated with the enhanced surface productivity. The planktonic foraminifera divided into two groups based on their preferrence. The G. bulloides and N. dutertrei live in cold environment while G. aequilateralis, G. ruber, G. sacculifer, and Pulleniatina obliquiloculata preferr warm areas. In this study, G. bulloides and N. dutertrei were found in January whereas G. aequilateralis, G. rubber, G. sacculifer, and P. obliquiloculata were mostly in March.
The difference of carbon isotopes of planktonic foraminifera between species are distinct. Orbulina universa is the heaviest and G. ruber was the lightest. Foraminiferal d18O are depleted in October and enriched in January and March. It is suggested that sea surface temperature might be responsible for the variations of planktonic foraminiferal oxygen isotopes. Comparisons of foraminiferal d18O with the hydrographic data provide some informations. The results show that G. ruber lives in shallow water (~10m), G. sacculifer lives in 25m on average, and O. universa lives in deeper water layer (~70m) in northern South China Sea. Moreover, both the carbon isotopes and foraminiferal abundance of G. ruber show a negative correlation with the particles fluxes
Planktonic Foraminiferal Isotopic Records of Gutingken Formation at Shoushan, Kaohsiung
No full textThe samples for this study were adopted from the drilling cores for the slope-stability monitoring project inside the campus of NSYSU. Stratigraphically the strata belongs to the Gutingken Formation and is lain below the Kaohsiung Limestone. Two cores were selected for this research, one is W-2 (N: 2504008.088; E: 174168.943, 60m in length) and the other is S-4 (N: 2503968.458; E: 174009.179, 55m in length). The thickness of the Gutingken Mudstone in cores W2 and S4 is 38.7m and 21.8m, respectively. Each sample was obtained at every 10 cm interval for W2 and 30~40 cm for S4 with an average weight of 40 g.
This study mainly contains two parts: analyzing the planktonic foraminifera for their carbon and oxygen stable isotopic compositions and dating the downcore records by correlating with the nannobiostratigraphy. Particular is the stable isotopic compositions of planktonic foraminifera in these terrestrial sedimentary sequences which has not been done in Taiwan before.
Overall the mudstone analyzed in this study falls in the biostratigraphic range of small Gephyrocapsa Subchron, which spreads within 1.242 Ma~1.031 Ma. according to previous report. The age range is further constrained at about 1.186~1.065 Ma based on the oxygen isotope record and thus can be regarded as a high-resolution isotopic stratigraphy within the small Gephyrocapsa subchron. The average sedimentation rate inferred by the best age model from these cores is about 31cm/ky. It shows a progressive decrease in sedimentation rates: the younger the strata, the lower the sedimentation rate. On the contrary, the sedimentation rate varies dramatically at the lower part of the record. The turbidity current might be a potential factor responsible for the change. In addition, the spectral analysis of \uce\ub418O data presents a comparatively significant cycle of about 2.5ky through out the record. It might indicate a periodic forcing which influenced the environment during sediment depositation. The \uce\ub413C record obtained from this study fail to reflect the high productivity during the glacials. The mechanism that might affect the productivity in the area is not clear and still needs advanced research
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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