Organic matter rain rates, oxygen availability, and vital effects from benthic foraminiferal δC in the historic Skagerrak, North Sea

The sediment cores 225514 and 225510 were recovered from 420 and 285 m water depth, respectively. They were investigated for their benthic foraminiferal δ¹³C during the last 500 years. Both cores were recovered from the southern flank of the Skagerrak. The δ¹³C values of Uvigerina mediterranea and other shallow infaunal species in both cores indicate that organic matter rain rates to the seafloor varied around a mean value until approximately AD 1950 after which they increased. This increase might result from changes in the North Atlantic Current System and a co-occurring persistently high North Atlantic Oscillation index state in the 1980s to 1990s, rather than from anthropogenic eutrophication. Using δ¹³C mean values of multiple species, we reconstruct δ¹³C gradients of dissolved inorganic carbon (DIC) within pore waters for the time periods AD 1500 to 1950 and AD 1950 to 2000. The calculated δ¹³C_DIC ranges, interpreted as indicating total organic matter remineralization due to respiration, are generally bigger in Core 225514 than in Core 225510. Since mean δ¹³C values of U. mediterranea suggest that organic matter rain rates were similar at both locations, differences in total organic matter remineralization are attributed to differing oxygen availability. However, oxygen concentrations in the overlying bottom water masses are not likely to have differed significantly. Thus, we suggest that organic matter remineralization was controlled by oxygen availability within the sediments, reflecting strong differences in sedimentation rates at the two investigated core sites. Based on the assumptions that tests of benthic foraminiferal species inhabiting the same microhabitat depth should show equal δ¹³C values unless they are affected by vital effects and that Globobulimina turgida records pore water δ¹³C_DIC, we estimate microhabitat-corrected vital effects for several species with respect to G. turgida: > 0.7‰ for Cassidulina laevigata, > 1.3‰ for Hyalinea balthica, and > 0.7‰ for Melonis barleeanus. Melonis zaandami seems to closely record pore water δ¹³C_DIC.     

Chemical speciation of saliva containing remineralizing solutions and their predicted effectiveness for subsurface lesion remineralization

Abstract

A computer modelling approach to estimate the chemical speciation which occurs in saliva and in subsurface lesion remineralizing solutions has been used to correlate chemical speciation data with published findings related to remineralization of dental enamel. The work also provides a means of selecting improved carrier ligands for the ions involved in remineralization and for optimising tooth protection and repair.     

Systems and organismal aspects of phosphorus remineralization

During a six-month study at Lake George, N.Y., zooplankton contributed an average of 19.4% of the phosphate required for algal photosynthesis. Values ranged from 44.1% prior to the unimodal phytoplankton pulse to 4.6% during the phytoplankton bloom. Copepods accounted for a large percentage (21–68%) of the SRP recycled during the growing season examined, whereas, the cladocera provided only a small percentage of remineralization (6.9%).Contribution No. 315 from the Eastern Deciduous Forest Biome, U. .-IBP, Research supported by the Eastern Diciduous Forest Biome U.S.-IBP, funded by the National Science Foundation under interagency agreement AG-199. DEB 76-00761 with the U.S. Department of Energy — Oak Ridge National Laboratory.     

Double blind clinical trial of a remineralizing dentifrice in the prevention of caries in a radiation therapy population

Objectives: The purpose of this study is to determine the efficacy and safety of a specially formulated remineralizing toothpaste in controlling caries in a group of high risk, head and neck radiation patients. Design: The study compares the performance of the remineralizing toothpaste with a leading conventional fluoride dentifrice using double-blind randomization. Test Products The products compared both contain equivalent quantities of fluoride (1150ppm). The remineralizing toothpaste also delivers soluble calcium and phosphate ions, the essential components of teeth. Subjects: On completion, 50 subjects who received >50 Gy of radiation to the head and neck. Measurements: Examinations include coronal and root caries using the Pitts Diagnostic Criteria, salivary flow rate, plaque and gingival indices and microbiological counts over one year. Results: At this point subjects are enrolled in the study at various phases. However, the current average for the net increment per month per subject is −0.12 (±1.30) for coronal caries and 0.06 (±0.73) for root caries in subjects using the remineralizing toothpaste and 0.53 (±1.62) for coronal caries and 0.45 (±0.98) for root caries in subjects using the conventional fluoride dentifrice. Non-parametric analysis of rank scores for net root surface increments/month was statistically significant (p=0.02), suggesting lower net root surface increment/month for the remineralizing toothpaste relative to the conventional toothpaste. No significant differences were noted on coronal surfaces. Conclusions: The results to date indicate that the remineralizing toothpaste is significantly superior to the conventional fluoride dentifrice in preventing root caries in high risk patients.     

半导体激光联合CPP-ACP对乳牙早期釉质龋再矿化的作用研究

目的:探讨应用半导体激光联合酪蛋白磷酸肽钙磷复合体(CPP-ACP)对乳牙早期釉质龋再矿化的作用。方法:选择下颌离体乳前牙制备人工龋模型40例,将其随机分为5组:脱矿组(A)、单纯激光组(B)、CPP-ACP组(C)、先激光后CPP-ACP组(D)、先CPP-ACP后激光组(E)。运用X射线能谱分析技术分析五组样本的钙和磷摩尔百分比变化,运用扫描电子显微镜观察牙釉质表面形态的变化。结果:C组、D组、E组的Ca、P摩尔百分比含量明显高于A组(P0.05),而D组、E组再矿化程度高于C组(P0.05),B组Ca、P摩尔百分比与A组比较差异无统计学意义(P0.05)。扫描电镜观察显示再矿化处理后除对照组试件外,其余3组试件均可见矿物质沉积。结论:激光协同CPP-ACP能有效促进脱矿乳牙的再矿化,其再矿化能力远大于单纯使用CPP-ACP,单纯使用激光在本次实验中未能体现出再矿化能力。