Morgenstern U.,Institute of Geological & Nuclear Sciences |
Ditchburn R.G.,Institute of Geological & Nuclear Sciences |
Vologina E.G.,Russian Academy of Sciences |
Sturm M.,Waters Technology
Journal of Paleolimnology | Year: 2013
We applied the 32Si dating technique to a sediment core from Lake Baikal to obtain the sediment chronology for the last millennium. The core was recovered about 4 km offshore from the north slope of the South Basin in 1,366 m water depth. The sediment material consisted of continuously accumulated diatom-rich geogenic-terrigenous mud, intercalated with a number of dark olive-grey turbidite layers. The sediment layers containing the turbidites were excluded from 32Si sampling to obtain the chronology that is representative of the continuous sedimentation. The initial 32Si activity of 31.3 dpm kg-1 SiO2, measured in sediment trap samples, confirms the trend of 32Si specific activities of biogenic silica found in other Northern Hemisphere lakes. The four sediment core samples from depth 0-48 cm have 32Si specific activities between 23.5 and 0.5 dpm kg-1 SiO2, with corresponding ages between 60 and 860 years and constant sedimentation rate of 0.036 ± 0.004 cm year-1 over the most recent 800 years. 32Si allowed us for the first time to date the uppermost turbidites in the South Basin of Lake Baikal, to 1030, 1310 and 1670 ad. Given these dates, the last long-distance turbidity current triggered by slope instabilities had occurred 330 years before 2000 ad, and the intervals between the 1310 and 1670 ad event and between the 1030 and 1310 ad event were 360 and 280 years, respectively. The 32Si ages allow unprecedented time resolution for reconstruction of the former environmental and climatic conditions during the past millennium. © 2013 Springer Science+Business Media Dordrecht.
Zaimes G.N.,Waters Technology |
Schultz R.C.,Iowa State University
Catena | Year: 2015
Stream bank erosion and deposition are complex phenomena because of the many factors that influence them. These factors can be spatial such as bank aspect, height and slope or temporal such as seasonal and yearly precipitation and streamflow events. Riparian land-use also has a major influence. This study investigated for two years, spatial and temporal patterns and dominant geomorphologic processes of stream bank erosion and deposition along a 10. km reach of Bear Creek in north-central Iowa, USA. The channel sub-reaches used were adjacent to a riparian forest buffer, a perennial grass filter and a continuously grazed pasture. Two plots were placed in each sub-reach; one on a north-facing outside bank (north-bank) and the other on a south-facing outside bank (south-bank). Each plot had two photo-electronic erosion pins (PEEPs) placed at 1/3 of the bank height (bottom-bank) and the other at 2/3 of the bank height (top-bank). PEEP daily measurements were compared to daily precipitation and streamflow. The continuously grazed pasture banks had the highest erosion rates. The grass area banks had approximately equal rates of erosion and deposition. The riparian forest buffer banks had high erosion rates during the second year. In the continuously grazed pasture, fluvial entrainment was the dominant erosion process, although minor mass failures also caused erosion. In the riparian forest buffer most erosion was recorded after moderate streamflows removed the bank soil loosened by freeze-thaw cycling. This occurred in late winter/early spring, when trees provide primarily mechanical but not hydraulic reinforcement to stream banks and on the lower part of the banks that have less extensive root networks. Overall, stream bank erosion and deposition in each sub-reach occurred during different time periods and under different processes and conditions. This indicates the need for continuous erosion and deposition measurements along with continuous soil moisture, soil temperature and streamflow measurements to fully comprehend these erosion phenomena. © 2014 Elsevier B.V..
Miller A.G.,University of Manchester |
Brown H.,Waters Technology |
Degg T.,Leeds Teaching Hospitals |
Allen K.,Leeds Teaching Hospitals |
Keevil B.G.,University of Manchester
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences | Year: 2010
In patients with carcinoid disease, urinary concentration of the serotonin metabolite 5-hydroxyindole acetic acid (5-HIAA) is currently used to monitor disease progression or response to treatment as it is the metabolic end-product resulting from free and stored serotonin turnover. However, due to the undignified, cumbersome and error-prone nature of 24-h urine collections, there is constant pressure to replace them. It has been demonstrated using high performance liquid chromatography (HPLC) with fluorescence detection technology that plasma can achieve this, with the added advantage that it can be used for diagnostic purposes also. Here we describe a much simpler method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) that is twice as fast as a HPLC method currently in routine use. The sample preparation protocol requires 50 μL of plasma and a simple protein precipitation step facilitated by acetonitrile. Chromatography was performed on a Phenomenex C18 Security Guard™ column coupled to a SIELC Primesep B reversed-phase, anion-exchange dual chemistry column and methanolic mobile phase gradient elution. Eluant was directly connected to a Waters® Quattro Premier™ XE tandem mass spectrometer operating in positive ion mode. We detected multiple reaction monitoring transitions m/z 191.9 > 145.6 and 193.9 > 147.6 for 5-HIAA and d2-5-HIAA respectively, which co-eluted at 2.1 min. Ion suppression was negligible, recovery from spiked plasma was 103% (range 97-113%) and the method showed good linearity to 10,000 nmol/L (r2 = 0.999). Within-batch and between-batch imprecision was <10% and bias <15% at 3 concentrations, the limit of detection was 5 nmol/L and lower limit of quantitation 15 nmol/L. No interference was observed with l-tryptophan or 5-hydroxytryptamine. Comparison of LC-MS/MS and HPLC showed good agreement between the two methods but this LC-MS/MS assay displays several advantages; it requires 10-fold less sample, has a simpler extraction procedure and extended linearity, thus increasing laboratory throughput, lowering reagent costs and removing the need to dilute samples in patients with established carcinoid disease being monitored for therapeutic efficacy. © 2010 Elsevier B.V. All rights reserved.
Nabuchi Y.,Yokohama City University |
Hirose K.,Waters Technology |
Takayama M.,Yokohama City University
Analytical Chemistry | Year: 2010
Folding analysis of the zinc protein, carbonic anhydrase 2 (CA2), was performed using electrospray ionization ion mobility spectrometry coupled with collision-induced dissociation (ESI IMS/CID). Multiply protonated ions with a bimodal charge state distribution were observed indicating the presence of at least two folding states for gas-phase CA2 ions as was described in a previous study (Nabuchi, Y.; Murao, N.; Asoh, Y.; Takayama, M. Anal. Chem. 2007, 79, 8342-8349). In the IMS driftgram, several ions with different mobility were observed for each multiply charged ion, and this suggests that CA2 ions consist of several components with different folding states. IMS/CID spectra were acquired against precursor ions separated by mobility. The CID spectra gave several characteristic product ions including those from the N- and C-terminal region of CA2. A shift to larger charge number for the most abundant of the several product ions was observed for ions having a larger drift time. This charge number shift indicates that the folding state of the ion is more unfolded. Furthermore, differences in the production of an ion corresponding to the N-terminal side fragment gave information about the unfolding process of CA2. © 2010 American Chemical Society.
Waters Technology | Date: 2011-11-28
Described are a method and an apparatus for delivering a fluid having a desired mass composition. According to the method, temperatures of the fluids to be mixed are sensed and the densities of the fluids at the sensed temperatures are determined. The volume of each fluid is determined so that a mixture of the fluids at the sensed temperatures has the desired mass composition. The determined volumes of the fluids are combined to create the mixture. In one option, combining the determined volumes includes metering flows of the fluids sequentially into a common fluid channel. Alternatively, combining the determined volumes includes controlling a flow rate of each of the fluids and directing the fluids into a common fluid channel.