Techniques for Contamination Assessment During Drilling for Terrestrial Subsurface Sediments

Details about the procedures for drilling a ca. 150 m long drill core in a terrestrial setting under contamination controlled conditions are presented. Different to previous studies we only used commercially available drilling equipment to reduce the cost of operation significantly. The goals were (1) to minimize, (2) to monitor and, if possible, to quantify the contamination of the recovered sediments, and (3) to identify the different sources of contamination. Both the potential contamination of the sample material by surface microorganisms and non-indigenous material was assessed. To estimate the infiltration of drill mud into the core, fluorescent microspheres, having about half the size as microorganisms, were added to the mud. The drilling technique used was mud rotary drilling. With the exception of the very beginning of the drilling operations, the drill mud was devoid of any allochthonous hydrocarbons potentially derived from the drilling equipment or drill additives, and its biomarker composition reflected the varying organo-facies that were penetrated. Due to the lack of allochthonous hydrocarbons in the drill mud, its infiltration into the sediment cannot be traced by organic geochemical biomarker analysis. Microspheres proved to be a sensitive tool for the assessment of infiltration of drill mud into the core. The concentration of microspheres in the drill mud decreased continuously during the drilling, most probably caused by seepage of mud through leaks and attachment of spheres to the surface scum in the mud pit. Microscopic enumeration of the microspheres showed great variability in the depth of penetration of mud into the core, apparently unaffected of lithology. The sampling of the core material in the laboratory was carried out inside an anaerobic chamber. Several techniques for subsampling were used, according to sediment properties. The overall results indicate that, if strict contamination control protocols are employed, it is possible to recover uncontaminated samples at reasonable cost with commercially available drilling equipment.     

海城仙人洞遗址出土钻器的实验研究

本文运用实验考古学方法,在模拟制作和使用脉石英钻器的基础上,记述了用脉石英钻器钻孔所产生的使用微痕的特点,并讨论了制作疤与使用微痕的区别,进而对海城仙人洞遗址出土的从形态上鉴定为钻器的标本做微痕观察和分析。结果表明它们中后部分所见使用微痕基本具有钻孔形成的特点。因而这部分石器的功能应该是钻,是名符其实的钻器。     

颅骨自动钻孔技术探析

头骨钻孔为脑部微创手术的重要步骤,现有钻孔设备多采朋手动方式,钻孔设备没有任何判断钻穿的装置,钻穿骨头后停止钻进完全靠医生的经验来实现。介绍了国内外该领域的研究现状与存在问题,提出了一种颅骨钻穿自动停刀的判断方法,提出了颅骨自动钻孔技术未来发展的趋势。     

Intense drilling in the Carboniferous brachiopod Cardiarina cordata Cooper, 1956

The brachiopod Cardiarina cordata, collected from a Late Pennsylvanian (Virgilian) limestone unit in Grapevine Canyon (Sacramento Mts., New Mexico), reveals frequent drillings: 32.7% (n = 400) of these small, invariably articulated specimens (<2 mm size) display small (<0.2 mm), round often beveled holes that are typically single and penetrate one valve of an articulated shell. The observed drilling frequency is comparable with frequencies observed in the Late Mesozoic and Cenozoic. The drilling organism displayed high valve and site selectivity, although the exact nature of the biotic interaction recorded by drill holes (parasitism vs. predation) cannot be established. In addition, prey/host size may have been an important factor in the selection of prey/host taxa by the predator/parasite. These results suggest that drilling interactions occasionally occurred at high (Cenozoic-like) frequencies in the Paleozoic. However, such anomalously high frequencies may have been restricted to small prey/host with small drill holes. Small drillings in C. cordata, and other Paleozoic brachiopods, may record a different guild of predators/parasites than the larger, but less common, drill holes previously documented for Paleozoic brachiopods, echinoderms, and mollusks.     

Drilling in bone: modeling heat generation and temperature distribution

Thermo-mechanical equations were developed from machining theory to predict heat generation due to drilling and were coupled with a heat transfer FEM simulation to predict the temperature rise and thermal injury in bone during a drilling operation. The rotational speed, feed rate, drill geometry and bone material properties were varied in a parametric analysis to determine the importance of each on temperature rise and therefore on thermal damage. It was found that drill speed, feed rate and drill diameter had the most significant thermal impact while changes in drill helix angle, point angle and bone thermal properties had relatively little effect.     

Theoretical temperature calculation in the cutting area in drilling cortical bones

To date, analysis of temperature in the drill area of cortical bone have been limited to measurements with thermocouple systems at a certain distance from the drill hole. Many authors equate this temperature measurement with the drill--cortical bone interface temperature. In order show that there is a temperature difference, a drill hole was simulated with the aid of the "Finite Element Method". The interface temperature was calculated by the energy distribution. It was shown, that for "dry" and "watercooled" drilling, the drill hole temperature was 13 degrees C higher than the temperature measured with the thermocouple systems at a distance 0.5 mm of from the drill hole. In particular when using "watercooled" drills for bone and dental surgery, the temperature may be higher than the bone damage limit of 44 degrees C for lengthy and 50 degrees C for brief drilling.     

Investigation of the potential for microbial contamination of deep granitic aquifers during drilling using 16S rRNA gene sequencing and culturing methods

Total number of bacteria, viable counts of aerobic and anaerobic heterotrophic bacteria and 16S rRNA gene diversity were investigated during drilling of three boreholes in the walls of the Äspö hard rock laboratory tunnel, at depths ranging from 380 to 446 m below sea level. Water samples were taken from the drill water source, the drilling equipment and from the drilled boreholes. The drill water was kept under nitrogen atmosphere and all equipment was steam cleaned before the start of a new drilling. Total and viable counts of bacteria in the drilled boreholes were several orders of magnitude lower than in the samples from the drilling equipment, except for sulphate reducing bacteria. A total of 158 16S rRNA genes that were cloned from the drill water source, the drilling equipment and the drilled boreholes were partially sequenced. The drilled boreholes generally had a 16S rRNA diversity that differed from what was found in samples from the drilling equipment. Several of the sequences obtained could be identified on genus level as one of the genera Acinetobacter, Methylophilus, Pseudomonas and Shewanella. In conclusion, the tubing used for drill water supply constituted a source of bacterial contamination to the rest of the drilling equipment and the boreholes. The results show, using molecular and culturing methods, that although large numbers of contaminating bacteria were introduced to the boreholes during drilling, they did not establish in the borehole groundwater at detectable levels.     

Effect of durophagy on drilling predation: a case study of Cenozoic molluscs from North America

Drilling predation represents one of the most widely studied biotic interactions preserved in the fossil record, and complete and incomplete drill holes have been commonly used to explore spatial and temporal patterns of this phenomenon. While such patterns are generally viewed solely in terms of the interactions between predator and prey, they might also be affected by extrinsic ecological factors. Recent experiments have demonstrated that in the presence of a secondary predator (crab), the incomplete drilling frequency increases indicating increasing abandonment of the prey, and drilling frequency decreases implying a decrease in successful attacks. Here, we tested whether the effect of secondary predators on drilling frequencies can be detected in the fossil record. Using fossil molluscs from six Plio-Pleistocene localities, we found that repair scar frequencies, a proxy for activity of durophagous predators, correlate directly with incomplete drill hole frequencies and inversely with complete drill hole frequencies. These results suggest that the activity and success of drilling predators is influenced not just by the prey, but also by secondary predators.     

Predatory shell drilling by two species of Austroginella (Gastropoda: Marginellidae)

Predatory shell drilling of bivalve mollusc shells is reported for the gastropods Austroginella johnstoni and A. muscaria from south-eastern Australia. This is the first record of this feeding behaviour in the family Marginellidae. The drill holes are circular and paraboloid, with a small inner penetration hole. The corroded nature of the aragonite crystals within the drill holes suggests a chemical dissolution drilling mechanism. No obvious accessory boring organ was located. The gastropods have subepithelial gland cells in the proboscis, a pair of small salivary glands and a large foregut gland. The latter has a duct bypassing the valve of Leiblein and joining the anterior oesophagus.     

Shift work at a modern offshore drilling rig

The oil and gas exploration and production offshore units are classified as hazardous installations. Work in these facilities is complex, confined and associated with a wide range of risks. The continuous operation is secured by various shift work patterns. The objective of this study was to evaluate how offshore drilling workers perceived shift work at high seas and its impacts on their life and working conditions. The main features of the studied offshore shift work schedules are: long time on board (14 to 28 days), extended shifts (12 hours or more per day), slow rotation (7 to 14 days in the same shift), long sequence of days on the night shift (7 to 14 days in a row) and the extra-long extended journey (18 hours) on shift change and landing days. Interviews revealed a wide range of stressors caused by the offshore shift work, as well as difficulties to conciliate work with family life. It was observed that changes of the family model, leading to role conflicts and social isolation, work in a hazardous environment, perceiving poor sleep when working at night shifts and the imbalance between the expected and actual rewards are the major stressors for the offshore drilling workers.     

Modeling and experimentation of bone drilling forces

Prediction and control of bone drilling forces are critical to the success of many orthopaedic operations. Uncontrolled and large forces can cause drill-bit breakage, drill breakthrough, excessive heat generation, and mechanical damage to the bone. This paper presents a mechanistic model for prediction of thrust forces and torques experienced during bone drilling. The model incorporates the radially varying drill-bit geometry and cutting conditions analytically, while capturing the material and friction properties empirically through a specific energy formulation. The forces from the chisel edge are modeled by considering the indentation process that occurs in the vicinity of the drill-bit axis. A procedure is outlined to calibrate the specific energies, where only a small number of calibration experiments are required for a wide range of drilling conditions and drill-bit geometry. The calibration parameters for the cortical portions of bovine tibia are identified through drilling tests. Subsequently, a series of validation tests are conducted under different feed rates and spindle speeds. The thrust forces and torques were observed to vary considerably between bones from different animals. The forces from the model were seen to match well with those from the experimentation within the inherent variations from the bone characteristics. The model can be used to select favorable drilling conditions, to assist in robotic surgeries, and to design optimal orthopaedic drill bits.     

Post-Drilling Changes in Seabed Landscape and Megabenthos in a Deep-Sea Hydrothermal System,the Iheya North Field,Okinawa Trough

There has been an increasing interest in seafloor exploitation such as mineral mining in deep-sea hydrothermal fields, but the environmental impact of anthropogenic disturbance to the seafloor is poorly known. In this study, the effect of such anthropogenic disturbance by scientific drilling operations (IODP Expedition 331) on seabed landscape and megafaunal habitation was surveyed for over 3 years using remotely operated vehicle video observation in a deep-sea hydrothermal field, the Iheya North field, in the Okinawa Trough. We focused on observations from a particular drilling site (Site C0014) where the most dynamic change of landscape and megafaunal habitation was observed among the drilling sites of IODP Exp. 331. No visible hydrothermal fluid discharge had been observed at the sedimentary seafloor at Site C0014, where Calyptogena clam colonies were known for more than 10 years, before the drilling event. After drilling commenced, the original Calyptogena colonies were completely buried by the drilling deposits. Several months after the drilling, diffusing high-temperature hydrothermal fluid began to discharge from the sedimentary subseafloor in the area of over 20 m from the drill holes, ‘artificially’ creating a new hydrothermal vent habitat. Widespread microbial mats developed on the seafloor with the diffusing hydrothermal fluids and the galatheid crab Shinkaia crosnieri endemic to vents dominated the new vent community. The previously soft, sedimentary seafloor was hardened probably due to barite/gypsum mineralization or silicification, becoming rough and undulated with many fissures after the drilling operation. Although the effects of the drilling operation on seabed landscape and megafaunal composition are probably confined to an area of maximally 30 m from the drill holes, the newly established hydrothermal vent ecosystem has already lasted 2 years and is like to continue to exist until the fluid discharge ceases and thus the ecosystem in the area has been altered for long-term.     

Drilling under threat: An experimental assessment of the drilling behavior of Nucella lamellosa in the presence of a predator

Using the drilling muricid, Nucella lamellosa (Gmelin 1791) and its prey, the mussel Mytilus trossulus (Gould 1850), the impact of a secondary predator, the crab Cancer gracilis, on drilling was investigated experimentally. The frequency of incomplete holes was compared under two conditions: (1) when the gastropod's natural predator, C. gracilis, was present and (2) when it was absent. The results indicate that the presence of a secondary predator can affect drilling activity, leading to a significant increase in the frequency of incomplete drill holes. The introduction of a secondary predator can also decrease the overall drilling frequency. The size distributions of completely and incompletely drilled mussels suggest that in the presence of the secondary predator the decision by the gastropod to either abandon or continue drilling its prey might be influenced by how much time it has already invested into drilling or the size of the prey item. These results are important for the ecological and evolutionary implications of incomplete drill holes frequencies, especially with regard for their use as proxies for evolutionary prey improvement.     

The effects of excessive drilling diagnosis on decay propagation in trees

The effects of excessive drilling into the trunk with an increment borer and drilling resistance measurement device were determined for four trees of three different species (Populus nigra L., Acer pseudoplatanus L., Quercus robur L.). At the test trees with an internal decay it was found that there are two counteracting effects: First, the internal decay slightly enters into the drilling channel, which is locally a negative effect. But, on the other hand, there is the creation of a reaction zone beside the drilling hole enclosing the drilling channel in order to delay efficiently further decay propagation. Furthermore, there is the formation of a barrier zone spacious covering the location of drilling with multiple layers of fungicide tissue. These are two positive effects stopping or delaying the local outgrowth of the internal decay. Far away from the drilling hole the internal decay is not only locally coming out into the sound wall thickness but is also not specially delayed in propagation. So after some years the decay front is everywhere homogenous again, respectively, the spreading central inner decay has caught up with the migrated decay in the drilling channel. For the tree the negative effect of drilling was compensated nearly completely. In addition, it was found that in no case a decay had entered the drilling channels from outside and survived in the outer area of the drill hole.     

Reasons for poor establishment of direct re-seeded grassland

These experiments suggest a number of causes for the poor establishment of direct reseeded grass. An adequate supply of moisture to the seed is of prime importance and burial of trash in drill slits may impair this supply by preventing seed/soil contact directly or by preventing closure of the drill slit. Management techniques which aim to reduce the burden of trash in areas to be sown by direct drilling, usually result in improvements in emergence. This is achieved by improved seed/soil contact, reduced evaporation of water from an open drill slit and lowered probability of phytotoxic leachates being produced. It is possible that benefits might be achieved were it possible to select for sowing seed of proven high vigour, i.e. seed that establishes well in poor conditions.     

Stereotypic and size-selective predation in Polinices pulchellus (Gastropoda: Naticidae) Risso 1826

Polinices pulchellus were size-selective in their choice of Cerastoderma edule. Large predators (12-15.9 mm shell length) selected both larger and a wider size range of cockles than smaller individuals (4-11.9 mm shell length). Considerable overlap occurred in the sizes of cockles frequently drilled by different size classes of snails, indicating that certain sizes of cockles may be most profitable to a wide range of predator sizes. Consumption rates were highest during July and August and were closely related to seawater temperature. Inner and outer drill hole diameters were both correlated with predator size, and the morphology of the drill hole was geometrically similar across a range of predator sizes. Polinices pulchellus showed no preference for either the left or right valve and drilled most cockles in the centre of the shell valve. The relationship between the distance of the drill hole from the umbo and prey size was unaffected by predator size, such that predators of different sizes were not found to drill cockles in different positions. When disturbed during drilling, incomplete drill holes were abandoned and, when drilling resumed, it occurred in new locations on the surface of the shell valve. The findings of this study highlight the stereotyped nature of drilling behaviour seen in the family Naticidae.     

Pulling or drilling, does size or species matter? An experimental study of prey handling in Octopus dierythraeus ()

The influence of both predator and prey size on the shift from a pulling to a drilling predatory response was examined in the intertidal octopus Octopus dierythraeus, using an experimental program. Additionally, selective drilling, where particular regions of the prey are targeted, was examined for a variety of bivalve and gastropod prey. O. dierythraeus always initially attempted to pull bivalves apart. Shells that were eventually drilled were always subjected to significantly more pulling attempts than those that could be pulled apart, indicating that octopus are willing to expend more energy to access the flesh quickly. There was no defined threshold where bivalve size caused an octopus to switch from a pulling to a drilling response. Instead, there was a broad size range where the octopus could adopt either handling method and it varied for each individual. Octopus may only able to pull open bivalves before the molecular ratchet or ‘catch’ mechanism that many bivalves possess is engaged. This might explain the lack of a relationship between either octopus or bivalve size and the success of pulling, as it is likely that when the bivalves were presented to individual octopus they were either setting the ‘catch’ mechanism, or had already engaged it. O. dierythraeus demonstrated selective drilling on a variety of molluscan prey, with penetration sites differing between prey species. O. dierythraeus targeted the valve periphery, which was the thinnest part of the shell, therefore minimizing handling time. O. dierythraeus always drilled gastropods, but did not target the thinnest regions of the shells, with drill site varying according to the morphology of the prey. Elongate species with pronounced aperture lips were drilled in the apical region, close to the columella on the side of the opercula whereas nonelongate species were drilled immediately above the aperture. The location of drilling sites may represent a trade-off between targeting the most effective places to inject paralyzing secretions and the mechanically simplest places to drill.     

Drill Holes and Predation Traces versus Abrasion-Induced Artifacts Revealed by Tumbling Experiments

Drill holes made by predators in prey shells are widely considered to be the most unambiguous bodies of evidence of predator-prey interactions in the fossil record. However, recognition of traces of predatory origin from those formed by abiotic factors still waits for a rigorous evaluation as a prerequisite to ascertain predation intensity through geologic time and to test macroevolutionary patterns. New experimental data from tumbling various extant shells demonstrate that abrasion may leave holes strongly resembling the traces produced by drilling predators. They typically represent singular, circular to oval penetrations perpendicular to the shell surface. These data provide an alternative explanation to the drilling predation hypothesis for the origin of holes recorded in fossil shells. Although various non-morphological criteria (evaluation of holes for non-random distribution) and morphometric studies (quantification of the drill hole shape) have been employed to separate biological from abiotic traces, these are probably insufficient to exclude abrasion artifacts, consequently leading to overestimate predation intensity. As a result, from now on, we must adopt more rigorous criteria to appropriately distinguish abrasion artifacts from drill holes, such as microstructural identification of micro-rasping traces.