Termination 1A Research Articles

Morphosedimentary, Structural and Benthic Characterization of Carbonate Mound Fields on the Upper Continental Slope of the Northern Alboran Sea (Western Mediterranean)

Carbonate mounds clustering in three fields were characterized on the upper continental slope of the northern Alboran Sea by means of a detailed analysis of the morphosedimentary and structural features using high-resolution bathymetry and parametric profiles. The contemporary and past benthic and demersal species were studied using ROV underwater imagery and some samples. A total of 325 mounds, with heights between 1 and 18 m, and 204 buried mounds were detected between 155 to 401 m water depth. Transparent facies characterize the mounds, which root on at least six erosive surfaces, indicating different growth stages. At present, these mounds are covered with soft sediments and typical bathyal sedimentary habitat-forming species, such as sea-pens, cerianthids and sabellid polychaetes. Nevertheless, remains of colonial scleractinians, rhodoliths and bivalves were detected and their role as potential mound-forming species is discussed. We hypothesized that the formation of these mounds could be related to favorable climatic conditions for cold-water corals, possibly during the late Pleistocene. The occurrence on top of some mounds of abundant rhodoliths suggests that some mounds were in the photic zone during minimum sea level and boreal guest fauna (e.g., Modiolus modiolus), which declined in the western Mediterranean after the Termination 1a of the Last Glacial (Late Pleistocene).

A relay catalysis strategy for enantioselective nickel-catalyzed migratory hydroarylation forming chiral α-aryl alkylboronates

A relay catalysis strategy for enantioselective nickel-catalyzed migratory hydroarylation forming chiral α-aryl alkylboronates

Modular Synthesis of Diarylalkanes by Nickel-Catalyzed 1,1-Diarylation of Unactivated Terminal Alkenes

A nickel-catalyzed 1,1-diarylation of electronically unbiased alkenes has been developed, providing straightforward access to diarylalkanes from readily available materials. Importantly, both the e...

COULD SATISFACTION ON THE AIRLINE’S SERVICE QUALITY (AIRQUAL) MAKE LION AIR’S CUSTOMERS TRUST AND BECOME LOYAL TO THE AIRLINE COMPANY?

The Indonesian public interest in using the service flights as their means of transportation is remarkably growing according to Indonesia Investment data in 2017. People tend to use service flights because of Indonesia’s unique geographical nature and airline tickets becomes increasingly affordable as the growth low-cost carrier. The purpose of this research is to investigate the role of customer satisfaction toward the airline’s service quality (AIRQUAL) in effecting trust and loyalty. The study was directly conducted by collecting primary data by randomly distribute 252 questioners to respondents that were boarding gate terminal 1A and 1B at the Soekarno Hatta International Airport. Hypotheses were then statistically tested using structural equation model. The results of this research show that satisfaction can make customer whose satisfied with the quality of the airline service become loyal to Lion Air. On the contrary, satisfaction cannot make the customer trust Lion Air as an airline company, even though they already satisfied with the quality of airline service.

Speleothem based 1000-year high resolution record of Indian monsoon variability during the last deglaciation

A high resolution record of the Indian summer monsoon (ISM) is generated using a δ18O time series from a stalagmite collected from the Valmiki cave in southern India. This record covers a time span of ~1000years from 15,700 to 14,700yr BP (before 1950AD) with an average sampling resolution of ~5years. High amplitude δ18O variation in this record reflects abrupt changes in ISM activity during the last deglaciation and suggest an age for the onset of Termination 1a (T1a) at ~14,800yr BP in the Indian sub-continent. This record shows evidence for strong changes in tropical climate during the last deglaciation. Coincident variability in VSPM4 δ18O with speleothems from southern China during Termination 1a suggests that these caves reflect fluctuations in ISM activity. The variance in δ18O amplitude reveals significant multidecadal variability in ISM activity. Our record reveals intervals of strong monsoon activity during the later phase of Heinrich event 1 (H1) and shows synchronous multidecadal variability between ISM and East Asian monsoon (EAM). Spectral analysis of δ18O time series in VSPM4 reveals solar forcing and strong ocean–atmospheric circulation control on ISM dynamics during the studied time interval.

Responses to rapid warming at Termination 1a at Gerzensee (Central Europe): Primary succession, albedo, soils, lake development, and ecological interactions

The transition from the Oldest Dryas to the Bølling around 14,685calyr BP was a period of extremely rapid climatic warming. From a single core of lake marl taken at Gerzensee (Switzerland) we studied the transition in stable isotopes of oxygen and carbon on bulk sediment and charophyte remains, as well as on monospecific samples of ostracods, after Pisidium a; in addition pollen, chironomids, and Cladocera were analyzed. The δ18O record serves as an estimate of mean air temperature, and by correlation to the one from NGRIP in Greenland it provides a timescale.The timing of responses: The statistically significant zone boundaries of the biostratigraphies are telescoped at the rapid increase of about 3‰ in δ18O at the onset of Bølling. Biotic responses may have occurred within sampling resolution (8 to 16years), although younger zone boundaries are less synchronous. Gradual and longer-lasting responses include complex processes such as primary or secular succession. During the late-glacial interstadial of Bølling and Allerød, two stronger and two weaker cool phases were found.Biological processes involved in the responses occurred on levels of individuals (e.g. pollen productivity), of populations (increases or decreases, immigration, or extinction), and on the ecosystem level (species interactions such as facilitation or competition).Abiotic and biotic interactions include pedogenesis, nitrogen-fixation, nutrient cycling, catchment hydrology, water chemistry of the lake and albedo (controlled by the transition from tundra to forest).For the Swiss Plateau this major change in vegetation induced a change in the mammal fauna, which in turn led to changes in the tool-making by Paleolithic people.

Chronological framework of Asian Southwest Monsoon events and variations over the past 24,000 years in Sri Lanka and regional correlations

An accelerator mass spectrometry (AMS- 14C) dated multi-proxy upper montane rainforest record from the Horton Plains, Central Sri Lanka reveals a ~ 24,000 year history of millennial-scale monsoon climate variability since the last glacial maximum (LGM). The vegetation history indicates that post-LGM earliest tropical warming and monsoon initiation preceded the Northern Hemisphere ice-sheet melting by over 3000 years before the Bolling interval, with a significant increase in the precipitation at Termination 1A (event-B in the Horton Plains). This suggests a major early strengthening of the monsoon. Starting ca. 17,600 years before present (yr BP), the rainforest diversity increases in-step with four progressively increasing humid events (A-D) and interrupted by two relatively semi-arid/weak episodes of which the second (Termination 1B) ending ca. 10,400 yr BP may reflect a delayed Younger Dryas event. The optimum rainforest diversification coincides with the Holocene monsoon precipitation maximum ca. 9,200 − 8,800 yr BP (event-D). A disruption to these millennial cycles coincided with a gradual monsoon downturn, precipitation and rainforest decline and aridity between ca. 8,100 − 3,400 yr BP. The conditions became more humid again for rainforest expansions between ca. 3,400 − 1,500 yr BP (event-E). Broadly synchronous millennial-scale climatic records of the Horton Plains, Arabian Sea, Oman, Yemen and India, equatorial West and East Africa, and the North Atlantic regions indicate twoway teleconnections between the tropical Asian Monsoon fluctuations and high latitude events. The above changes reflect vast spatial rearrangements in atmospheric circulation patterns, probably caused by forcing associated with coupled ocean-atmosphere-vegetation feedbacks. There is a remarkably close correlation of the different proxies that has tracked the Southwest Monsoon variations across the region since the LGM. J.Natn.Sci.Foundation Sri Lanka 2013 41 (3): 219-228 DOI: http://dx.doi.org/10.4038/jnsfsr.v41i3.6057

Biotic responses to rapid warming at Termination 1a at Gerzensee (Central Europe) – Hypotheses about succession, albedo, soils, lake development, and ecological interactions

Biotic responses to rapid warming at Termination 1a at Gerzensee (Central Europe) – Hypotheses about succession, albedo, soils, lake development, and ecological interactions

1,4-Dihydroxyanthraquinone-copper(II) nanoparticles immobilized on silica gel: a highly efficient, copper scavenger and recyclable heterogeneous nanocatalyst for a click approach to the three-component synthesis of 1,2,3-triazole derivatives in water

High yielding preparation of structurally different β-hydroxy 1,4-disubstituted 1,2,3-triazole from the regio-selective reaction of epoxides 2a–2c with wide range of terminal alkynes 1a–1j, and sodium azide in the presence of catalytic amount, complexed form of homogeneous catalyst [bis 1,4-mono ester hydroxy anthraquinone copper(II)] (5.0 mol%), [AQ2Cu(II)] 7 at 25 °C in water has been described. To benefit from the recovery and reuse of the catalyst, a novel heterogeneous nanoparticles of catalyst [bis 1,4-mono ester hydroxy anthraquinone copper(II) aminopropyl silica gel] (5.0 mol%), [AQ2Cu(II)-APSiO2] 13 bearing oxygen anthraquinone ligands with strong copper(II) affinity was easily prepared by using silica gel as a suitable support. The heterogeneous catalyst was fully characterized by XRD, SEM, AFM, ICP, TG methods for analysis of nitrogen adsorption, and FT-IR techniques. The remarkable features of this protocol are high yields, short reaction times, a cleaner reaction profile in an environmentally benign solvent (H2O), one-pot procedure and the method is applicable to large-scale operation without any problem. Furthermore, the catalyst could be recovered and easily removed by simple filtration of the reaction mixture and it was recycled ten times showing negligible copper leaching. In their uncomplexed form of homogeneous catalyst [AQ2Cu(II)] 7 and heterogeneous catalyst [AQ2Cu(II)-APSiO2] 13, the anthraquinone ligand 6 and [AQ-APSiO2] 12 are very efficient copper scavengers able to catalyze the 1,3-dipolar cycloaddition reaction of azides with alkynes (CuAAC) without pre-synthesis of catalysts.

Northern peatland initiation lagged abrupt increases in deglacial atmospheric CH 4

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

Rapid summer temperature changes during Termination 1a: high-resolution multi-proxy climate reconstructions from Gerzensee (Switzerland)

Quantitative July temperature reconstructions using fossil chironomid and pollen data have been carried out with a high temporal resolution for the Termination 1a and the late-glacial Interstadial (ca 15 000–13 000 cal years BP) on a sediment core from Gerzensee (Switzerland). The biota-based July temperature reconstructions show a rapid warming of 4–5 °C (pollen) and 2–3 °C (chironomids) at Termination 1a (i.e. the onset of the late-glacial Interstadial, ca 14 650 cal. BP). These temperature changes go parallel with a shift of more than 3‰ in a high-resolution stable oxygen isotope record measured on bulk carbonates from the same core, also indicating a substantial and rapid warming.Pollen-inferred July temperatures follow the shape of the oxygen-isotope record with a generally decreasing trend of ca 2 °C throughout the Interstadial, showing even minor cold oscillations of 0.5–1 °C in July temperature recorded in many central European sites (e.g. Aegelsee and Gerzensee Oscillations) and the Greenland ice cores (e.g. GI-1d and GI-1b). Chironomid-inferred summer temperatures, however, show a gradual increase of ca 2–3 °C throughout the Interstadial, interrupted by some cold oscillations (e.g. GI-1b) of 0.5–1 °C.The reconstructions based on both proxies are in agreement with comparable studies in the Jura Mountains and the Alps. Given the close correlation between the oxygen isotope record and the pollen-inferred temperatures, the discrepancies between the two biota-specific July temperature inferences could be explained by the higher sensitivity of vegetation to changes in seasonality and precipitation, whereas aquatic organisms such as chironomids are more responsive to summer season conditions.

ChemInform Abstract: Palladium Catalyzed [2 + 2 + 1] Cyclotrimerization of Alkynes: Selective Synthesis of Fulvenes.

Abstract This is the first report on the selective synthesis of fulvenes via a [2+2+1] cyclotrimerization of alkynes under catalytic conditions. The reactions of aliphatic terminal alkynes 1a – e in the presence of a palladium catalyst in toluene gave the cyclotrimerization products 2a – e , not easily available through the previously known methods, in good to fair yields.

Variations of the oxygen minimum zone of the Okhotsk Sea during the last 50 ka as indicated by benthic foraminiferal and biogeochemical data

Benthic foraminiferal and sediment biogeochemical data (total organic carbon, calcium carbonate and biogenic opal contents) in two cores (1265 and 1312 m water depths) from the southeastern Sakhalin slope and one core (839 m water depth) from the southwestern Kamchatka slope were investigated to reconstruct variations of the oxygen minimum zone during the last 50 ka in the Okhotsk Sea. The oxygen minimum zone was less pronounced during cooling in the MIS 2 that is suggested to be caused by a maximal expansion of sea ice cover, decrease of marine productivity and increase of production of the oxygenated Okhotsk Sea Intermediate Water (OSIW). A two-step-like strengthening of oxygen minimum zone during the warmings in the Termination 1a and 1b was linked to (1) enhanced oxygen consumption due to degradation of large amount of organic matter in the water column and bottom sediments, originated from increased marine productivity and supply of terrigenous material from the submerged northern shelves; (2) sea ice cover retreat and reduction of OSIW production; (3) freely inflow of the oxygen-depleted intermediate water mass from the North Pacific.

Late Pleistocene Sea level on the New Jersey Margin: Implications to eustasy and deep-sea temperature

We assembled and dated a late Pleistocene sea-level record based on sequence stratigraphy from the New Jersey margin and compared it with published records from fossil uplifted coral reefs in New Guinea, Barbados, and Araki Island, as well as a composite sea-level estimate from scaling of Red Sea isotopic values. Radiocarbon dates, amino acid racemization data, and superposition constrain the ages of large (20–80 m) sea-level falls from New Jersey that correlate with Marine Isotope Chrons (MIC) 2, 3b, 4, 5b, and 6 (the past 130 kyr). The sea-level records for MIC 1, 2, 4, 5e, and 6 are similar to those reported from New Guinea, Barbados, Araki, and the Red Sea; some differences exist among records for MIC 3. Our record consistently provides the shallowest sea level estimates for MIC3 (∼ 25–60 m below present); it agrees most closely with the New Guinea record of Chappell (2002; ∼ 35–70 m), but contrasts with deeper estimates provided by Araki (∼ 85–95 m) and the Red Sea (50–90 m). Comparison of eustatic estimates with benthic foraminiferal δ 18O records shows that the deep sea cooled ∼ 2.5 °C between MIC 5e and 5d (∼ 120–110 ka) and that near freezing conditions persisted until Termination 1a (14–15 ka). Sea-level variations between MIC 5b and 2 (ca. 90–20 ka) follow a well-accepted 0.1‰/10 m linear variation predicted by ice-growth effects on foraminiferal δ 18O values. The pattern of deep-sea cooling follows a previously established hysteresis loop between two stable modes of operation. Cold, near freezing deep-water conditions characterize most of the past 130 kyr punctuated only by two warm intervals (the Holocene/MIC 1 and MIC 5e). We link these variations to changes in Northern Component Water (NCW).

Late Pleistocene submarine mass movements: occurrence and causes

An extensive study of Late Pleistocene continental slope submarine mass movements was undertaken. Twenty-six well-dated mass movements occurred during the last 45 ka BP in the North Atlantic sector. A latitudinal trend is observed: between 45 and 12 ka BP most events occur in the mid- to low-latitudes, post-12 ka BP high-latitude occurring events dominate. A cluster of events is associated with the Last Glacial sea level lowstand and Termination 1B. Further events are associated with Termination 1A and the Holocene. Prior to 23 ka BP no clear relationship with the ice core atmospheric methane record is observed, in contrast during and following the deglaciation there is a possible relationship with atmospheric methane. High-latitude mass movements are primarily controlled by cyrospheric-induced variations in sedimentation and local sea level. In high latitudes, the glaciation subdues mass movement activity through reduced seisimicity, sediment supply and ocean temperatures. Deglaciation increases the sediment supply, seisimicity and ocean temperatures, thus increasing the likelihood of continental slope failures. For example the Storegga event coincides with high isostatic uplift and postglacial seisimicity, while the Andøya and Trænadjupet events occur before and after the peak rates respectively. In contrast low latitudes experience greater risk of slope failures during glacial periods from falling sea levels, although during the deglacial and interglacial period there is a potential for failure from changes in deposition centres and rates, as well as warming ocean temperatures potentially leading to dissociation of gas hydrates. The ongoing rapid deglaciation of coastal Greenland and Antarctica and consequent rapid input of sediment, isostatic uplift, crustal stress release and warming bottom water temperature at the shelf break will increase the risk of continental slope failure in these regions.

Seasonal sea surface temperature contrast between the Holocene and last glacial period in the western Arabian Sea (Ocean Drilling Project Site 723A): Modulated by monsoon upwelling

Annual, summer, and winter sea surface temperatures (SSTs) in the western Arabian Sea were reconstructed through the last 22 kyr using artificial neural networks (ANNs) based on quantitative analyses of planktic foraminifera. Down‐core SST estimates reveal that annual, summer, and winter SSTs were 2, 1.2, and 2.6°C cooler, respectively, during the last glacial period than in the Holocene. A 2.5°C SST increase during Termination 1A (hereinafter referred as glacial to Holocene transition) in the western Arabian Sea. The study reveals a strong seasonal SST contrast between winter and summer from 18 to 14 calendar kyr owing to the combined effect of weak upwelling and strong cold northeasterly winds. Minor or no seasonal SST changes were noticed within the Holocene period, which is attributed to the intense upwelling during the summer monsoon. This causes a lowering of SST to values similar to those of the winter season in analogy with the present day. A 3°C rise in winter SSTs during the glacial to Holocene transition coincides with a strengthening of the monsoon, suggesting a link between winter SST and monsoon initiation from the beginning of the Holocene. Strikingly, annual, summer, and winter SSTs show a cooling trend from ∼8 ka to the present day, implying tropical cooling in the late Holocene.

Exclusive underexpression of vitamin D receptor exon 1f transcripts in tumors of primary hyperparathyroidism.

Primary hyperparathyroidism (pHPT) is characterized by excessive production of parathyroid hormone (PTH) due to parathyroid adenomas while uremic secondary HPT (sHPT) is caused by parathyroid hyperplasia in response to renal failure. Active vitamin D, 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)), with the vitamin D receptor (VDR) is involved in regulation of the calcium homeostasis together with PTH. In a feedback loop, 1,25-(OH)(2)D(3) has a direct action on the parathyroid gland to regulate PTH transcription, PTH secretion and cell proliferation. We have previously demonstrated reduced VDR mRNA expression in parathyroid adenomas and hyperplasia of sHPT using a probe detecting all 14 variant VDR transcripts expressed in parathyroid cells. Here we have assessed which of the 5'-terminal exon 1a, 1d and 1f variant VDR transcripts are reduced in pathological parathyroid glands. The relative VDR/glyceraldehyde-3-phosphate dehydrogenase mRNA levels for each VDR exon were determined by real-time quantitative RT-PCR in five normal parathyroid glands, seventeen parathyroid adenomas and ten hyperplastic glands of sHPT. The results demonstrated exclusive underexpression of VDR exon 1f transcripts in parathyroid adenoma, while all measured VDR transcripts were reduced in secondary hyperplasia. We suggest that exclusive underexpression of VDR exon 1f transcripts in adenomas of pHPT, which derive from a distal promoter active in tIssues involved in calcium regulation by 1,25-(OH)(2)D(3), may either reflect a defective cell type-specific transcription factor or other physiologically important pathway(s) for tIssue-specific VDR gene expression.

Paleoproductivity variations related to climatic conditions in the Alboran Sea (western Mediterranean) during the last glacial–interglacial transition: the diatom record

The present study addresses the analysis of changes in marine primary productivity derived from climatic variability over the last 30,000 yr. The study area is the Alboran Sea; this is the westernmost basin of the Mediterranean Sea, and was a very sensitive area to changes in sea levels and atmospheric configuration during the last glacial–interglacial transition. We report the results from four sediment cores recovered in both the western and eastern Alboran basins. This allowed us to monitor the W–E evolution of the hydrological structures. The study is mainly based on the diatom record, although total organic carbon (TOC), isotopes and UK′37-SST were also used to gain further information. Paleoceanographic conditions favoured high paleoproductivity rates during the Last Glacial Maximum, although this occurred at Termination 1a and during the Younger Dryas event (YD), increasing towards the easternmost sites. During these periods, meteorological conditions, with increased westerlies, intensified the flow to the east, driving an eastward migration of the Western Anticyclonic Gyre. A possible displacement of the North Alboran upwelling system is also considered. The major component of the diatom assemblage during the YD are the resting spores of Leptocylindrus danicus, which suggest the presence of cooler and less saline surface waters. The opposite behaviour between planktonic and benthic proxies in addition to the high TOC values allows us to infer a phase of reduced deep water renewal between 16.5 and 9 cal ky BP. Fresh-water diatoms and opal phytoliths were used as indicators of aridity and humid land-conditions, respectively. During the glacial period and until 14 cal ky BP we observed a gradual climatic deterioration, accompanied by a loss of grass belts. Climatic conditions were warmer and moister during the Bølling–Allerød while the YD was dry. The re-establishment of vegetation belts and replenishment of lakes was observed at 8 cal ky BP.

Regioselective control of the thiocarbonylation of terminal acetylenes with arylthiols catalyzed by Pd(II) and diphosphine ligands

Control of the regioselective thiocarbonylation of terminal acetylenes 1a– e with arylthiols 2a, b was successfully achieved by using Pd(OAc) 2 and 1,4-bis(diphenylphosphino)butane (dppb), or 1,3-bis(diphenylphosphino)propane (dppp), as catalysts. The formation of the thioesters 3 or 4 depends mainly on the type of ligand (dppp or dppb) and the solvent (THF or CH 2Cl 2) under CO/H + or syngas mixture.

Palladium catalyzed [2+2+1] cyclotrimerization of alkynes: selective synthesis of fulvenes

This is the first report on the selective synthesis of fulvenes via a [2+2+1] cyclotrimerization of alkynes under catalytic conditions. The reactions of aliphatic terminal alkynes 1a– e in the presence of a palladium catalyst in toluene gave the cyclotrimerization products 2a– e, not easily available through the previously known methods, in good to fair yields.