The Relationship of Extrinsic Dark Tooth Stains to Dental Caries

The purpose of this investigation was to assess the relationship between certain coloured extrinsic tooth stains and dental disease with particular emphasis on black extrinsic tooth stain. Bacteriological and chemical analyses were carried out into the aetiology and composition of the black material found upon the teeth of certain individuals. An epidemiological survey was also carried out, in which dental caries, calculus, dental cleanliness and coloured extrinsic tooth stains were recorded on 928 children aged thirteen years. An analysis was made of the data to study possible relationships between dental caries and the other variables particularly black extrinsic tooth stain. It was found that: 1. Girls brushed their teeth more often than boys and had significantly cleaner mouths. 2. A significant correlation was found between oral hygiene and, gingivitis in both boys and girls. 3. A mean number of 8.25 D-M-F teeth per child was found. 4. Children with dark extrinsic tooth stain had a significantly lower dental caries experience than those with either no stain or stain of other colours. 3. No significant correlation was found between the standard of oral hygiene in children with no tooth stain and children with extrinsic black stain. 6. A significant correlation between the stated sweet consumption and numbers of D-M-F teeth was found. 7. No significant correlation between oral hygiene and the D-M-F rate was found. 8. A significantly lower oxygen tension was found in children with extrinsic black tooth stain than those with no stain. 9. Greater numbers of Bacteroides melaninogenicus were found in children with black extrinsic tooth stain than those with no stain but the correlation between the groups was not significant. 10. Iron and sulphide was found in gingival scrapings from children with black stain upon their teeth but a less vigorous reaction for sulphide only was found in gingival scrapings from children with no coloured tooth stains. 11. Spectral studies on the supernatant of an homogenate of gingival debris from the black stain group indicated that significant amounts of iron-sulphur proteins or haem compounds were not present. 12. Iron was found in the black material recovered from culture plates on which Bacteroides melaninogenicus was grown. However, the test for sulphide was negative. 13. Spectrographic analysis of the supernatant from the microbiological culture plate did not indicate that significant amounts of iron-sulphur proteins or haem compounds were present. 14. Examination of the ultrastructure of Bacteroides melaninogenicus from a pure growth demonstrated the presence of a cell wall, cytoplasmic membrane, "bridges" and a dense crust. Both the cell wall and the cytoplasmic membrane were seen as triple layered structures. 13. Cell division of Bacteroides melaninogenicus appeared to be by inward growth of the cell wall-cytoplasmic membrane complex until fission was complete. 160 Electron microscopic studies of the organisms on the tooth section demonstrate both a cell wall and cytoplasmic membrane. These organisms were also shown to be gram negative cocco-bacilli. 17. An homogeneous cell-free dark material was demonstrated interposed between the microbial layer and the tooth surface The results show that children with extrinsic black tooth stain had a lower D-M-F rate than children with no tooth stains. The numbers of Bacteroides melaninogenicus were greater in the black stain group although not sufficiently so to be statistically significant. Chemical analysis of gingival scrapings revealed the presence of iron and. sulphide in the black stain group but only thiocyanate in the gingival scrapings from the control group. Thus the black material from both in vivo and. in vitro sources has iron with sulphide present in the former. These factors plus the lower oxygen tension found in the mouths of the black stain group suggest that Bacteroides melaninogenicus is the aetiological agent responsible for the extrinsic black stain found on the teeth of certain children in this study. Certainly if black stain could be produced on the teeth of germ-free animals using Bacteroides melaninogenicus this would be further evidence to support the part played by these organisms in black stain production. This line of investigation would be interesting in spite of the fact that Bacteroides melaninogenicus would not become established as a monocontaminant in mice (Gibbons et al., 1964). The part played by the organisms in the dental caries process could then be studied and it is hoped that further work into both these topics will be undertaken. Perhaps the results of this study will strengthen the statement made by Bibby (1931): "The principal value of this discussion seems to be its suggestion that a sweeping condemnation of all deposits on the surface of the teeth is unjustified, as at least, this particular plaque appears to exert nothing but a protective action"

Telecommunications and radio-metric support for a manned mission to Mars

Some general characteristics of the Deep Space Network are described and related to services needed by a manned mission to Mars. Specific details of the current Network capabilities and those planned for the near future may be found in the reference

Delayed inhibition of an anticipatory action during motion extrapolation

Background: Continuous visual information is important for movement initiation in a variety of motor tasks. However, even in the absence of visual information people are able to initiate their responses by using motion extrapolation processes. Initiation of actions based on these cognitive processes, however, can demand more attentional resources than that required in situations in which visual information is uninterrupted. In the experiment reported we sought to determine whether the absence of visual information would affect the latency to inhibit an anticipatory action. Methods: The participants performed an anticipatory timing task where they were instructed to move in synchrony with the arrival of a moving object at a determined contact point. On 50% of the trials, a stop sign appeared on the screen and it served as a signal for the participants to halt their movements. They performed the anticipatory task under two different viewing conditions: Full-View (uninterrupted) and Occluded-View (occlusion of the last 500 ms prior to the arrival at the contact point). Results: The results indicated that the absence of visual information prolonged the latency to suppress the anticipatory movement. Conclusion: We suggest that the absence of visual information requires additional cortical processing that creates competing demand for neural resources. Reduced neural resources potentially causes increased reaction time to the inhibitory input or increased time estimation variability, which in combination would account for prolonged latency

Methodology for Life Testing of Refractory Metal/Sodium Heat Pipes

The focus of this work was to establish an approach to generate carefully controlled data that can conclusively establish heat pipe operating life with material-fluid combinations capable of extended operation. To accomplish this goal acceleration is required to compress 10 years of operational life into 3 years of laboratory testing through a combination of increased temperature and mass fluence. Specific test series have been identi3ed, based on American Society for Testing and Materials (ASTM) specifications, to investigate long term corrosion rates. The refractory metal selected for demonstration purposes is a Molybdenum-44.5%Rhenium alloy formed by powder metallurgy. The heat pipe makes use of an annular crescent wick design formed by hot isostatic pressing of Molybdenum-Rhenium wire mesh. The heat pipes are filled using vacuum distillation and purity sampling is considered. Testing of these units is round-the-clock with 6-month destructive and non-destructive inspection intervals to identify the onset and level of corrosion. Non-contact techniques are employed for providing power to the evaporator (radio frequency induction heating at I to 5 kW per unit) and calorimetry at the condenser (static gas gap coupled water cooled calorimeter). The planned operating temperature range would extend from 1123 to 1323 K. Accomplishments prior to project cancellation included successful demonstration of the heat pipe wick fabrication technique, establishment of all engineering designs, baselined operational test requirements and procurement/assembly of supporting test hardware systems

Life Test Approach for Refractory Metal/Sodium Heat Pipes

Heat pipe life tests described in the literature have seldom been conducted on a systematic basis. Typically one or more heat pipes are built and tested for an extended period at a single temperature with simple condenser loading. This paper describes an approach to generate carefully controlled data that can conclusively establish heat pipe operating life with material-fluid combinations capable of extended operation. Approximately 10 years of operational life might be compressed into 3 years of laboratory testing through a combination of increased temperature and mass fluence. Two specific test series have been identified and include: investigation of long term corrosion rates based on the guidelines contained in ASTM G-68-80 (using 7 heat pipes); and investigation of corrosion trends in a cross correlation sequence at various temperatures and mass fluences based on a central composite test design (using 9 heat pipes). The heat pipes selected for demonstration purposes are fabricated from a Mo-44.5%Re alloy with a length of 0.3 meters and a diameter of 1.59 cm(to conserve material) with a condenser to evaporator length ratio of approximately 3. The wick is a crescent annular design formed from 400-mesh Mo-Re alloy material hot isostatically pressed to produce a final wick core of 20 microns or less

How Differing Soil Microbial Communities and Dehydration Stress Effect Arabidopsis thaliana Morphological Development

Arabidopsis thaliana was exposed to five different soil treatments: Vermicompost, ‘Food Waste’ Compost, Potting soil (4:1 Promix BX/Perlite), Autoclaved Vermicompost and Autoclaved ‘Food Waste’ compost. Soil treatments A and B were tested for the presence of bacteria using MacConkey and Phenylethyl Alcohol media. All plants were watered on Tuesdays and Fridays and no longer received water after one month. Leaf number, stem height and length of the largest leaf were measured before and after dehydration stress. Once the dehydration stress began, the majority of the plants did not survive with the exception of the vermicompost

Size-resolved aerosol and cloud condensation nuclei (CCN) properties in the remote marine South China Sea - Part 1: Observations and source classification

Abstract. Ship-based measurements of aerosol and cloud condensation nuclei (CCN) properties are presented for 2 weeks of observations in remote marine regions of the South China Sea/East Sea during the southwestern monsoon (SWM) season. Smoke from extensive biomass burning throughout the Maritime Continent advected into this region during the SWM, where it was mixed with anthropogenic continental pollution and emissions from heavy shipping activities. Eight aerosol types were identified using a k-means cluster analysis with data from a size-resolved CCN characterization system. Interpretation of the clusters was supplemented by additional onboard aerosol and meteorological measurements, satellite, and model products for the region. A typical bimodal marine boundary layer background aerosol population was identified and observed mixing with accumulation mode aerosol from other sources, primarily smoke from fires in Borneo and Sumatra. Hygroscopicity was assessed using the κ parameter and was found to average 0.40 for samples dominated by aged accumulation mode smoke; 0.65 for accumulation mode marine aerosol; 0.60 in an anthropogenic aerosol plume; and 0.22 during a short period that was characterized by elevated levels of volatile organic compounds not associated with biomass burning impacts. As a special subset of the background marine aerosol, clean air masses substantially scrubbed of particles were observed following heavy precipitation or the passage of squall lines, with changes in observed aerosol properties occurring on the order of minutes. Average CN number concentrations, size distributions, and κ values are reported for each population type, along with CCN number concentrations for particles that activated at supersaturations between 0.14 and 0.85 %

Andrew Melville, sacred chronology and world history: the Carmina Danielis 9 and the Antichristus

The accepted view of the ecclesiastical reformer Andrew Melville (1545–1622) as the dynamic leader of the Presbyterian movement in Jacobean Scotland has been severely eroded in recent years, with particular criticism of the actual importance of his contribution to the Kirk and to Scottish higher education. While this reductionism has been necessary, it has resulted in an inversion of the overwhelmingly positive traditional image of Melville, and does not give us a rounded assessment of his life and works. This article attempts to partially redress this balance by looking at a neglected aspect of Melville's Latin writings, which showcase his talents as a humanist intellectual and biblical commentator. It focuses on two long poems that are both commentaries and paraphrases of Daniel and Revelation: the Carmina Danielis and the Antichristus. Through these poems, we see how Melville engaged with two problems exercising reformed theologians across Europe: the dating of key biblical events and the historicised meaning of prophecies within these texts. We also find evidence that Melville read widely among both contemporary and ancient commentators on both these issues

Decision-making without a brain: how an amoeboid organism solves the two-armed bandit

Several recent studies hint at shared patterns in decision-making between taxonomically distant organisms, yet few studies demonstrate and dissect mechanisms of decision-making in simpler organisms. We examine decision-making in the unicellular slime mould Physarum polycephalum using a classical decision problem adapted from human and animal decision-making studies: the two-armed bandit problem. This problem has previously only been used to study organisms with brains, yet here we demonstrate that a brainless unicellular organism compares the relative qualities of multiple options, integrates over repeated samplings to perform well in random environments, and combines information on reward frequency and magnitude in order to make correct and adaptive decisions. We extend our inquiry by using Bayesian model selection to determine the most likely algorithm used by the cell when making decisions. We deduce that this algorithm centres around a tendency to exploit environments in proportion to their reward experienced through past sampling. The algorithm is intermediate in computational complexity between simple, reactionary heuristics and calculation-intensive optimal performance algorithms, yet it has very good relative performance. Our study provides insight into ancestral mechanisms of decision-making and suggests that fundamental principles of decision-making, information processing and even cognition are shared among diverse biological systems

Nutrient contamination from an agricultural non-point source and its mitigation: A case study of EKU Meadowbrook Farm, Madison County, Kentucky

Non-point sources are now responsible for most nutrient contamination in surface water and groundwater, leading to eutrophication and decreased water quality. Because of fertilizer use and animal husbandry, agricultural areas are prime sources for nutrient contamination. Consequently, it is advisable to mitigate entry of nutrients into watersheds from agricultural runoff and groundwater flow. Eastern Kentucky University (EKU) Meadowbrook Farm (Madison County, Kentucky) seeks to decrease its export of nutrients to Muddy Creek, which is tributary of the Kentucky River. To demonstrate the efficacy of any sequestration strategies, nutrient export must be measured both before and after sequestration efforts are implemented. Over the past two field seasons, we have investigated the sources and behavior of dissolved nutrients (phosphate, PO43-; ammonium, NH4+; nitrate, NO3-) and other dissolved ions, and their transport via hydrologic pathways at the Farm. Here, we present our findings in three parts: (1) background nutrient concentration in surface water and groundwater during fair-weather times and identification of likely nutrient sources (Borowski et al.); (2) details of cation and nutrient drainage from the Farm during rain events (Buskirk et al.); and (3) quantification of nutrient export from a representative sub-watershed on the Farm during a major rainfall event (Winter et al.). Meadowbrook Farm is a working farm raising crops (mainly corn and soybeans), and rearing dairy and beef cattle and other livestock. Livestock produce manure that is eventually applied to pasture and croplands; supplemental fertilizer is also used. These are the primary sources for excess nutrients that leave the Farm via overland and groundwater flow. We sampled water from several different water sources and measured their nutrient content. Water types include that from drainage tiles, springs (groundwater), and surface water within intermittent streams on the Farm, other adjacent streams, and Muddy Creek. Water samples were passed through a 0.4 mm syringe filter and then preserved at a pH of 2 with sulfuric acid (H2SO4). Nutrient concentration, expressed in terms of phosphorus (P) and nitrogen (N) content, was measured colorimetrically using an UV-VIS spectrophotometer and the ascorbic acid (orthophosphate; P-PO43-), sodium hypochlorite (ammonium, N-NH4+), and cadmium reduction (nitrate, N-NO3-) methods. Nitrate is the nutrient contaminant with highest median concentration (~1.1 mg/L N-NO3) in surface waters; median concentration for ammonium and phosphate are ~0.3 mg/L N-NH4+ and ~0.03 mg/L P-PO43-, respectively. Relative to national data, Farm groundwater is enriched in all nutrients with median concentrations of ~0.04 mg/L N-NH4+, ~7.3 mg/L N-NO3, and ~0.04 mg/L P-PO43-. Enrichment in ammonium is more significant compared to that of nitrate and phosphate. These data provide fair-weather, background estimates for comparison to nutrient export that occur during rain events