甘肃棘豆属一新变种

Oxytropis xinglongshanica C. W. Chang var. obesusi-corollata Y. H. Wu, var. nov. A var. xinglongshanica recedit corollis obesis, vexillis c. 15 mm longis, c. 10 mm latis, limbis late ovatis, unguibus c. 6 mm longis; alis c. 14 mm longis, c. 4.5 mm latis, limbis anguste obovatis.

Soil organic carbon storage and soil CO2 flux in the alpine meadow ecosystem

High-resolution sampling, measurements of organic carbon contents and C-14 signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau, and application of C-14 tracing technology were conducted in an attempt to investigate the turnover times of soil organic carbon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12x10(4) kg C hm(-2) to 30.75x10(4) kg C hm(-2) in the alpine meadow ecosystems, with an average of 26.86x10(4) kg C hm(-2). Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m(-2) a(-1) to 254.93 gC m(-2) a(-1), with an average of 191.23 g C m(-2) a(-1). The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m(-2) a(-1) to 181 g C m(-2) a(-1). More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%. 81.23% of total CO2 emitted from organic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming, the storage, volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed, which needs further research.

湖光岩玛珥湖沉积物硅藻硅同位素研究

本论文选取我国的典型玛珥湖－湖光岩玛珥湖为研究对象，在国内外率先系统开展湖泊沉积物硅藻硅同位素研究。为获取过去2000a来的气候环境记录，对原有沉积物-水界面采样装置进行了改进，将沉积物柱芯无扰动采集深度从60cm提高到150cm。建立了一套有效的五阶段硅藻提纯方法，成功从初始硅藻含量大于7%的沉积物中提取出纯度达90％以上的硅藻样品，为广泛开展沉积物硅藻硅氧同位素研究奠定了基础。放射性核素Pb-210、Cs-137、C-14计年结果表明，该湖沉积物堆积速率稳定，具连续、稳定的堆积特点，是气候和环境变化的良好记录体。湖光岩玛珥湖沉积物硅藻硅同位素记录了硅藻利用水体溶解硅的比例变化。沉积物硅藻硅同位素与生物硅含量的变化关系为揭示湖泊古环境提供了重要线索。当硅藻硅同位素组成与生物硅含量呈正相关变化时，湖水溶解硅利用比例主要受温度控制，硅藻硅同位素可反映古温度变化。当硅藻硅同位素组成与生物硅含量不呈相似变化时，湖水溶解硅利用比例主要受有效养分控制，沉积物硅藻硅同位素仅仅反映硅藻利用水体溶解硅的比例，不反映古温度变化。湖光岩玛珥湖沉积物柱芯硅藻硅同位素组成的变化范围为 -0.6‰～1.1‰，其最小值出现于1580～1920年间，指示了1580～1920年为湖光岩地区过去2000年来最冷的时期，为中国南方热带地区现代小冰期的存在提供了新的证据。

Simple derivatization method for sensitive determination of fatty acids with fluorescence detection by high-performance liquid chromatography using 9-(2-hydroxyethyl)-carbazole as derivatization reagent

A simple and sensitive method for the determination of short and long-chain fatty acids using high-performance liquid chromatography with fluorimetric detection has been developed. The fatty acids were derivatized to their corresponding esters with 9-(2-hydroxyethyl)-carbazole (HEC) in acetonitrile at 60 degreesC with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride as a coupling agent in the presence of 4-dimethylaminopyridine (DMAP). A mixture of esters of C-1-C-20 fatty acids was completely separated within 38 min in conjunction with a gradient elution on a reversed-phase C-18 column. The maximum fluorescence emission for the derivatized fatty acids is at 365 nm (lambda (ex) 335 nm). Studies on derivatization conditions indicate that fatty acids react proceeded rapidly and smoothly with HEC in the presence of EDC and DMAP in acetonitrile to give the corresponding sensitively fluorescent derivatives. The application of this method to the analysis of long chain fatty acids in plasma is also investigated. The LC separation shows good selectivity and reproducibility for fatty acids derivatives. The R.S.D. (n = 6) for each fatty acid derivative are <4%. The detection limits are at 45-68 fmol levels for C-14-C-20 fatty acids and even lower levels for <C-14 fatty acids. (C) 2001 Elsevier Science B.V. All rights reserved.

X-ray crystallographic structures of two lamotrigine analogues: (I) 3,5-diamino-6-(2-chlorophenyl)-1,2,4-triazine water solvate and (II) 3,5-diamino-6-(3,6-dichlorophenyl)-1,2,4-triazine methanol solvate

The X-ray crystal structures of two lamotrigine derivatives (I) 3,5-diamino-6-(2-chlorophenyl)-1,2,4-triazine, C9H8ClN5, (465BL) as a hydrate, and (II) 3,5-diamino-6-(3,6-dichlorophenyl)-1,2,4-triazine, C9H7Cl2N5, (469BR) as a methanol solvate, have been carried out at liquid nitrogen temperature and room temperature, respectively. A detailed comparison of the two structures is given. Both are centrosymmetric with (I) in the orthorhombic space group Pbca, a = 12.2507(3), b = 15.7160(6), c = 21.71496(9) angstrom, Z = 16, and (II) in the monoclinic space group C2/c, a = 38.553(3), b = 4.9586(2), c = 14.546(2) angstrom, beta = 111.59(1)degrees, Z = 8. Final R indices [I > 2sigma(I)] for (I) are R1 = 0.0670, wR2 = 0.1515 and for (II) R1 = 0.0434, wR2 = 0.1185. Structure (I) has water of crystallization in the lattice and (II) includes a solvated CH3OH. Structure (I) is characterized by having two crystallographically independent molecules, A and B, of 465BL, per asymmetric unit. Molecule B has a very unusual feature in that the 2-chlorophenyl ring is statistically disordered, occupying site (1) in 87.5% of the structure and site (2) in 12.5% of the structure. Sites (1) and (2) are related by an exact 180 degrees pivot of the phenyl ring about the ring linkage bond. The presence of two independent molecules per asymmetric unit provides an ideal opportunity for the conformational flexibility of the molecule 465BL to be studied. Structure (I) also includes a further unusual feature in that the lattice contains one fully occupied water molecule and an additional solvated water which is only 33% occupied.

Radiocarbon wiggle-match dating of proglacial lake sediments - Implications for the 8.2 ka event

The problem of insufficient age-control limits the utilisation of the 8.2 ka BP event for modelling freshwater forcing in climate change studies. High-resolution radiocarbon dates, magnetic susceptibility and lithostratigraphic evidence from a lake sediment core from Nedre Hervavatnet located at Sygnefjell in western Norway provide a record of the early Holocene. We use the method of radiocarbon wiggle-match dating of the lake sediments using the non-linear relationship between the C-14 calibration curve and the consecutive accumulation order of the sample series in order to build a high-resolution age-model. The timing and duration of Holocene environmental changes is estimated using 38 AMS radiocarbon dates on terrestrial macrofossils, insects and chironomids covering the time period from 9750 to 1180 cal BP. Chironomids, Salix and Betula leaves produce the most consistent results. Sedimentological and physical properties of the core suggest that three meltwater events with high sedimentation rates are superimposed on a long-term trend with glacier retreat between 9750 and 8000 cal BP. The lake sediment sequence of Nedre Hervavatnet demonstrates the following: only a reliable high-resolution geochronology based on carefully selected terrestrial macrofossils allows the reconstruction of a more refined and complex environmental change history before and during the 8.2 ka event. (C) 2009 Elsevier Ltd. All rights reserved.

Cooling and changing seasonality in the Southern Alps, New Zealand during the Antarctic Cold Reversal

A comprehensively C-14 AMS dated pollen and chironomid record from Boundary Stream Tarn provides the first chironomid-derived temperature reconstruction to quantify temperature change during Lateglacial times (17,500-10,000 cal yr BP) in the Southern Alps, New Zealand. The records indicate a ca 1000-year disruption to the Lateglacial warming trend and an overall cooling consistent with the Antarctic Cold Reversal (ACR). The main interval of chironomid-inferred summer temperature depression (similar to 2-3 degrees C) lasted about 700 years during the ACR. Following this cooling event, both proxies indicate a warming step to temperatures slightly cooler than present during the Younger Dryas chronozone (12,900-11,500 cal yr BP). These results highlight a direct linkage between Antarctica and mid-latitude terrestrial climate systems and the largely asynchronous nature of the interhemispheric climate system during the last glacial transition. The greater magnitude of temperature changes shown by the chironomid record is attributed to the response of the proxies to differences in seasonal climate with chironomids reflecting summer temperature and vegetation more strongly controlled by duration of winter or by minimum temperatures. These differences imply stronger seasonality at times during the Lateglacial, which may explain some of the variability between other paleoclimate records from New Zealand and have wider implications for understanding differences between proxy records for abrupt climate change. (C) 2007 Elsevier Ltd. All rights reserved.

High-resolution stratigraphy of the northernmost concentric raised bog in Europe: Sellevollmyra, Andoya, northern Norway

From the Sellevollmyra bog at Andoya, northern Norway, a 440-cm long peat core covering the last c. 7000 calendar years was examined for humification, loss-on-ignition, microfossils, macrofossils and tephra. The age model was based on a Bayesian wiggle-match of 35 C-14 dates and two historically anchored tephra layers. Based on changes in lithology and biostratigraphical climate proxies, several climatic changes were identified ( periods of the most fundamental changes in italics): 6410-6380, 6230-6050, 5730-5640, 5470-5430, 5340-5310, 5270-5100, 4790-4710, 4890-4820, 4380-4320, 4220-4120, 4000-3810, 3610-3580, 3370-3340 ( regionally 2850-2750; in Sellevollmyra a hiatus between 2960-2520), 2330-2220, 1950, 1530-1450, 1150-840, 730? and c. 600? cal. yr BP. Most of these climate changes are known from other investigations of different palaeoclimate proxies in northern and middle Europe. Some volcanic eruptions seemingly coincide with vegetation changes recorded in the peat, e.g. about 5760 cal. yr BP; however, the known climatic deterioration at the time of the Hekla-4 tephra layer started some decades before the eruption event.

Constraining the age of Lateglacial and early Holocene pollen zones and tephra horizons in southern Sweden with Bayesian probability methods

The sediment sequence from Hasseldala port in southeastern Sweden provides a unique Lateglacial/early Holocene record that contains five different tephra layers. Three of these have been geochemically identified as the Borrobol Tephra, the Hasseldalen Tephra and the 10-ka Askja Tephra. Twenty-eight high-resolution C-14 measurements have been obtained and three different age models based on Bayesian statistics are employed to provide age estimates for the five different tephra layers. The chrono- and pollen stratigraphic framework supports the stratigraphic position of the Borrobol Tephra as found in Sweden at the very end of the Older Dryas pollen zone and provides the first age estimates for the Askja and Hasseldalen tephras. Our results, however, highlight the limitations that arise in attempting to establish a robust, chronologically independent lacustrine sequence that can be correlated in great detail to ice core or marine records. Radiocarbon samples are prone to error and sedimentation rates in lake basins may vary considerably due to a number of factors. Any type of valid and 'realistic' age model, therefore, has to take these limitations into account and needs to include this information in its prior assumptions. As a result, the age ranges for the specific horizons at Hasseldala port are large and calendar year estimates differ according to the assumptions of the age-model. Not only do these results provide a cautionary note for overdependence on one age-model for the derivation of age estimates for specific horizons, but they also demonstrate that precise correlations to other palaeoarchives to detect leads or lags is problematic. Given the uncertainties associated with establishing age-depth models for sedimentary sequences spanning the Lateglacial period, however, this exercise employing Bayesian probability methods represents the best possible approach and provides the most statistically significant age estimates for the pollen zone boundaries and tephra horizons. Copyright (C) 2006 John Wiley & Sons, Ltd.

Late Holocene climatic changes in Tierra del Fuego based on multiproxy analyses of peat deposits

A ca. 1400-yr record from a raised bog in Isla Grande, Tierra del Fuego, Argentina, registers climate fluctuations, including a Medieval Warm Period, although evidence for the 'Little Ice Age' is less clear. Changes in temperature and/or precipitation were inferred from plant macrofossils, pollen, fungal spores, testate amebae, and peat humification. The chronology was established using a C-14 wiggle-matching technique that provides improved age control for at least part of the record compared to other sites. These new data are presented and compared with other lines of evidence from the Southern and Northern Hemispheres. A period of low local water tables occurred in the bog between A.D. 960-1020, which may correspond to the Medieval Warm Period date range of A.D. 950-1045 generated from Northern Hemisphere tree-ring data. A period of cooler and/or wetter conditions was detected between ca. A.D. 1030 and I 100 and a later period of cooler/wetter conditions estimated at ca. cal A.D. 1800-1930, which may correspond to a cooling episode inferred from Law Dome, Antarctica. (C) 2004 University of Washington. All rights reserved.

Radiocarbon dating of bulk peat samples from raised bogs: nonexistence of a previously reported 'reservoir effect'?

In 1995. an unexpected reservoir effect was reported in sequences of bulk C-14 dates of raised bog peat. In most peat Studies bulk C-14 dates are used for obtaining chronologies. Therefore it is important to confirm and quantify such a C-14 reservoir effect. Five bulk peat samples from the raised bog Engbertsdijksveen were conventionally C-14 dated. The same core had previously been precisely dated by C-14 AMS dates of carefully selected above-ground plant remains. The existence of a reservoir effect in bulk peat C-14 samples could not be confirmed. Other explanations for the reported reservoir effect are discussed. (C) 2004 Elsevier Ltd. All rights reserved.

Marine reservoir corrections: St Helena, South Atlantic Ocean

We present the first marine reservoir age and Delta R determination for the island of St. Helena using marine mollusk radiocarbon dates obtained from an historical context of known age. This represents the first marine reservoir a.-c and Delta R determination in the southern Atlantic Ocean within thousands of kilometers of the island. The depletion of C-14 in the shells indicates a rather larger reservoir age for that portion of the surface Atlantic than models indicate. The implication is that upwelling old water along the Namibian coast is transported for a considerable distance, although it is likely to be variable on a decadal timescale. An artilleryman's button, together with other artifacts found in a midden, demonstrate association of the mollusk shells with a narrow historic period of AD 1815-1835.

Palaeobiology of an extinct Ice Age mammal: Stable isotope and cementum analysis of giant deer teeth

The extinct giant deer, Megaloceros giganteus, is among the largest and most famous of the cervids. Megaloceros remains have been uncovered across Europe and western Asia. but the highest concentrations come from Irish bogs and caves Although Megaloceros has enjoyed a great deal of attention over the centuries, paleobiological study has focused oil morphometric and distributional work until now. This paper presents quantitative data that have implications for understanding its sudden extirpation in western Europe during a period of global climate change approximately 10.600 C-14 years ago (ca 12,500 calendar years BP). We report here the first stable isotope analysis of giant deer teeth. which we combine with dental cementum accretion in order to document age, diet and life-history seasonality from birth until death Enamel delta C-13 and delta O-18 measured in the second and third molars from seven individual giant deer Suggest a grass and forbbased diet supplemented with browse in a deteriorating. possibly water-stressed, environment, and a season of birth around spring/early summer Cementurm data indicate that the ages of the specimens ranged from 6.5 to 14 years and that they possessed mature antlers by autumn, similar to extant cervids. In addition. the possibility for combining these two techniques in future mammalian paleoccological studies is considered. The data presented in this study imply that Megoloceros would have indeed been vulnerable to extirpation during the terminal Pleistocene in Ireland. and this information is relevant to understanding the broader pattern of its extinction.

Determining the Sun's influence on Lateglacial and Holocene climates: a focus on climate response to centennial-scale solar forcing at 2800 cal. BP

The influence of solar variability on the climate of the Lateglacial and Holocene periods has been the subject of increasing discussion during the last decade. In the Mid-Holocene, several studies have identified cold/wet events that occur at ca 2800 cal. BP and a link with a reduction in solar activity, inferred from the C-14 record, has been postulated. We present results from a multi-proxy study of peat humification, plant macrofossils and testate amoebae from a raised bog at Glen West, northwest Ireland, that indicate that dry bog surface conditions were experienced in the north of Ireland at the time of the solar anomaly starting at 2800 cal. BP. With the aid of C-14 wiggle-matching and tephrochronology, an abrupt shift to wetter conditions is dated to ca 2700 cal. BP, coinciding with a C-14 maximum but clearly post-dating the 2800 cal. BP event identified elsewhere in Europe. We explore the significance of this apparent lag in the Irish record, considering the possible role of the ocean in generating spatial and temporal complexities in the climate patterns of the North Atlantic region. We conclude that these complexities are likely to give rise to time-transgressive climate responses around the North Atlantic that will only be recognised by more critical chronological approaches.

The effect of triclabendazole ("Fasinex") on protein synthesis by the liver fluke, Fasciola hepatica

The effect of the active sulphoxide metabolite of the anthelmintic triclabendazole (TCBZ-SX, 15-50 mu g ml(-1)) on the incorporation of radioactively labelled [C-14] leucine by adult Fasciola hepatica tissue slices was measured by liquid scintillation counting. In addition, the ability of the microfilament-disrupting drug, cytochalasin B, and the microtubule-disrupting drug, tubulozole-C, to inhibit protein synthesis, was assessed by similar methods and compared with TCBZ-SX. The established protein synthesis inhibitors, cycloheximide and actinomycin D were used as positive controls. All the drugs showed a significant inhibition of protein synthesis, albeit to different extents; however, TCBZ-SX was the most potent, with no significant difference between its effect and that of cycloheximide or actinomycin D. Moreover, the concentration of TCBZ-SX, above 15 mu g ml(-1), had little further influence on incorporation of [C-14] leucine. This investigation demonstrates the inhibitory effect of TCBZ-SX, cytochalasin B and tubulozole-C on protein synthesis in F. hepatica and confirms the qualitative observations made in several previous ultrastructural studies.