Oxidative Conversion of Hexane to Olefins-Influence of Plasma and Catalyst on Reaction Pathways

An integrated plasma-Li/MgO system is efficient for the oxidative conversion of hexane. In comparison to the Li/MgO catalytic system, it brings considerable improvements in the yields of light olefins (C 2 = –C 5 = ) at relatively low temperatures indicating synergy from combination of plasma and catalyst. The study on the influence of temperature on the performance of the integrated plasma-Li/MgO system shows dominancy of plasma chemistry at the lower temperature (500°C), while contribution from the catalyst both in hexane activation and in enhancing olefin formation becomes significant at the higher temperature (600°C). At 500°C significant amount of acetylene formation is observed. This is minimized at 600°C at oxygen depleting condition

Contamination control engineering design guidelines for the aerospace community

Thermal control surfaces, solar arrays, and optical devices may be adversely affected by a small quantity of molecular and/or particulate contamination. What is rarely discussed is how one: (1) quantifies the level of contamination that must be maintained in order for the system to function properly, and (2) enforces contamination control to ensure compliance with requirements. This document is designed to address these specific issues and is intended to serve as a handbook on contamination control for the reader, illustrating process and methodology while providing direction to more detailed references when needed. The effects of molecular contamination on reflecting and transmitting surfaces are examined and quantified in accordance with MIL STD 1246C. The generation, transportation, and deposition of molecular contamination is reviewed and specific examples are worked to illustrate the process a design engineer can use to estimate end of life cleanliness levels required by solar arrays, thermal control surfaces, and optical surfaces. A similar process is used to describe the effect of particulate contamination as related to percent area coverage (PAC) and bi-directional reflectance distribution function (BRDF). Relationships between PAC and surface cleanliness, which include the effects of submicron sized particles, are developed and BRDF is related to specific sensor design parameters such as Point Source Transmittance (PST). The pros and cons of various methods of preventing, monitoring, and cleaning surfaces are examined and discussed

Auditory exostoses as an aquatic activity marker in coastal and inland skeletal remains from Brazil

Exostoses auditivas são utilizadas como marcadores de atividades aquáticas em estudos bioarqueológicos. A análise de 651 meatos auditivos direitos de esqueletos de 107 grupos brasileiros da costa e do interior mostrou que os grupos do interior apresentaram freqüências muito baixas de exostose (zero a 0,03), porém, nos grupos da costa (mais relacionados às atividades aquáticas devido ao padrão de subsistência baseado em recursos marinhos) a freqüência variou de zero a 0,58. Isso pode ser explicado pela combinação da temperatura atmosférica associada à ação dos ventos, uma vez que a temperatura da água não varia muito nessas regiões. Portanto, deve haver cautela quanto ao uso das exostoses auditivas como marcador de atividades aquáticas, já que este traço não se desenvolve, necessariamente, em todos os grupos ligados a essas atividades e, quando se desenvolve, apresenta freqüências distintas.Auditory exostoses are usually considered as a marker for aquatic activity aquatic marker in bioarcheological studies. The analysis of 651 right meatii from prehistoric and extant skeletons from 107 coastal and inland native Brazilian groups revealed very low frequency of auditory exostoses in the inland groups (zero to 0.03), while the frequency of auditory exostoses in the coastal groups (with intense aquatic activities due to their subsistence pattern based on marine resources) ranged from zero to 0.58. These differences might be explained by the combination of water and atmospheric temperatures in conjunction with wind chill effects. Therefore, the use of auditory exostoses as a marker of aquatic activity in coastal groups of tropical and subtropical regions must be performed cautiously, once it does not necessarily develop in all groups with the same frequency

Assesing use and suitability of scanning electron microscopy in the analysis of micro remains in dental calculus

Dental calculus is increasingly recognized as a major reservoir of dietary information. Palaeodietary studies using plant and animal micro remains (e.g. phytoliths, pollen, sponge spicules, and starch grains) trapped in calculus have the potential to revise our knowledge of the dietary role of plants in past populations. The conventional methods used to isolate and identify these micro remains rely on removing them from their microenvironment in the calculus, thus the microenvironment that traps and preserves micro remains is not understood. By using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEMeEDX) on modern chimpanzee calculus from the Taï Forest, Côte d¿Ivoire, and human calculus from the Chalcolithic site of Camino del Molino, Spain, we present the first reported observations on characteristics of the matrix setting that are conducive to the survival of starch in dental calculus. We also assess the potential for SEMeEDX to detect starch and differentiate it from structurally and molecularly similar substrates. We demonstrate that SEMeEDX may offer a nondestructive technique for studying micro remains in certain contexts. Finally, we compare traditional optical analytical techniques (OM) with less invasive electron microscopy. The results indicate that SEM-EDX and OM are both effective for observing micro remains in calculus, but differ in their analytical resolution to identify different micro remains, and we therefore recommend a sequential use of both techniques

Dental calculus evidence of Taï Forest Chimpanzee plant consumption and life history transitions

Dental calculus (calcified dental plaque) is a source of multiple types of data on life history. Recent research has targeted the plant microremains preserved in this mineralised deposit as a source of dietary and health information for recent and past populations. However, it is unclear to what extent we can interpret behaviour from microremains. Few studies to date have directly compared the microremain record from dental calculus to dietary records, and none with long-term observation dietary records, thus limiting how we can interpret diet, food acquisition and behaviour. Here we present a high-resolution analysis of calculus microremains from wild chimpanzees (Pan troglodytes verus) of Taï National Park, Côte d"Ivoire. We test microremain assemblages against more tan two decades of field behavioural observations to establish the ability of calculus to capture the composition of diet. Our results show that some microremain classes accumulate as long-lived dietary markers. Phytolith abundance in calculus can reflect the proportions of plants in the diet, yet this pattern is not true for starches. We also report microremains can record information about other dietary behaviours, such as the age of weaning and learned food processing techniques like nutcracking

Recovering Dietary Information from Extant and Extinct Primates Using Plant Microremains

When reconstructing the diets of primates, researchers often rely on several well established methods, such as direct observation, studies of discarded plant parts, and analysis of macrobotanical remains in fecal matter. Most of these studies can be performed only on living primate groups, however, and the diets of extinct, subfossil, and fossil groups are known only from proxy methods. Plant microremains, tiny plant structures with distinctive morphologies, can record the exact plant foods that an individual consumed. They can be recovered from recently deceased and fossil primate samples, and can also be used to supplement traditional dietary analyses in living groups. Here I briefly introduce plant microremains, provide examples of how they have been successfully used to reconstruct the diets of humans and other species, and describe methods for their application in studies of primate dietary ecology

Dental wash: a problematic method for extracting microfossils from teeth (galley proofs)

A variety of microfossils, originating from plant foods, become trapped in the dental calculus matrix. Processing of dental calculus allows extraction of these microfossils. The resulting data can be used to reconstruct diet at the individual and population levels as the identification of microfossils like starch grains and phytoliths to the generic level, and sometimes to the species level, is possible. However, in some archaeological sites, dental calculus deposits do not preserve well enough to be processed. To prevent the loss of information in such cases, we present a technique, called ‘‘dental wash’’. It permits extracting microfossils from cryptic dental calculus deposits. In the two experimental archaeological cases presented herein we identified phytoliths, starch grains as well as a diatom fragment with this method, whereas in a control sample no microfossils were found. Moderate damage to the teeth was detected when they were already friable due to poor preservation. Minor damage to the surface of well-preserved teeth was observed. This indicates that the proposed method is efficient in recovering microfossils, but unacceptable because of damage to teeth. If the method can be refined, it will expand the potential of dental calculus analysis to a greater range of archeological sites