454 research outputs found
The application of environmental magnetism to archaeological prospection: a semi-quantitative approach
Magnetic survey is the most widely used shallow geophysical techniquefor the location of
archaeological activity in the United Kingdom but is often discountedftom use within
alluviated landscapes. Results presented in this thesis from fluxgate gradiometer surveys
conducted over an alluviated flood plain near the village of Yarnton, Oxfordshire, UK,
demonstrate a wide variation of magnetic response between adjacent sites. This suggests a
more complicated relationship between the rock magnetic properties of underlying
archaeological sediments and the resultant magnetic anomalies recorded during surface
magnetometer surveys. This study aims to investigate this relationship further and
determine the influence of post-depositional mineral dissolution in water logged soils; a
factor that together with increased alluvial overburden, has often been cited as an
explanation for disappointing magnetic results over similar sites. A wide ranging study has
been conducted including geophysical surveys, environmental magnetic analysis of
archaeological sediments recovered during excavation and experimental work to
investigate the influence of burning. Initial, rapid determination of isothermal magnetic
parameters, such as susceptibility, has been complemented, for selected samples, by more
detailed hysteresis measurements and thermomagnetic variation over a temperature range
from 20 to 973K. Interpretation of the resulting data has been assisted through the
development of semi-quantitative numerical models to describe the complex magnetic
mixtures present. The results, including over 20ha (20, OOOOm2)of geophysical survey and
the analysis of more than 500 samples, demonstrate the important role of fire for magnetic
enhancement and also provides evidence, under suitable conditions, for more esoteric
biogenic mechanisms. The main conclusions reached suggest archaeological features
magnetised before the onset of floodplain conditions may still be detected through
geophysical survey, particularly if more sensitive, caesium vapour magnetometers are
applied In addition, semi-quantitative unmixing models allow both the thermal history of
burnt sediments to be estimated and provide a means for identifying biogenically enhanced
samples
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EAC Guidelines for the use of Geophysics in Archaeology: Questions to Ask and Points to Consider.
These guidelines provide an overview of the issues to
be considered when undertaking or commissioning
geophysical survey in archaeology. As every project diff ers
in its requirements (e.g. from fi nding sites to creating
detailed maps of individual structures) and variations in
geological and environmental conditions lead to diff erent
geophysical responses, there is no single ābestā survey
technique or methodology. Th is guide, in its European
approach, highlights the various questions to be asked
before a survey is undertaken. It does not provide recipebook
advice on how to do a geophysical survey or a tick
list of which technique is suitable under what conditions.
Experienced archaeological geophysicists should be
consulted to address the questions that are being posed.
Using geophysical techniques and methods inappropriately
will lead to disappointment and may, ultimately, result
in archaeologists not using them at all. āIf all you have is
a hammer (or magnetometer), driving a screw becomes
impossibleā.
Especially in the American literature the term āremote
sensingā is oft en used to describe geophysical as well as
air and space based exploration of underground features
(e.g. Wiseman and El-Baz 2007). By contrast, and in line
with European traditions, a clear distinction is made
here between ground-based geophysical techniques and
remote sensing techniques. Th is is based on the imaging
principles underlying the respective technologies. Ground
based systems usually collect one spatially registered data
sample from each sensor location (e.g. a single reading
for each magnetometer, or a single trace from each GPR
antenna). Remote sensing techniques, by contrast, collect
spatially resolved data from a whole area of investigation
from each sensor location, using either the systemās optical
aperture (e.g. photography) or a scanning device (e.g. laser
sampling).
These guidelines are based on the experience of the authors
in archaeological geophysics and infl uenced by various
published sources
Chemically Stable High Resolution Surface Patterning by Thiolated DNA for Self Assembly of Nanocircuits on a Gold Nano-Dot Surface
The Ursinus Weekly, January 15, 1951
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Evaluation of methods for oligonucleotide array data via quantitative real-time PCR
BACKGROUND: There are currently many different methods for processing and summarizing probe-level data from Affymetrix oligonucleotide arrays. It is of great interest to validate these methods and identify those that are most effective. There is no single best way to do this validation, and a variety of approaches is needed. Moreover, gene expression data are collected to answer a variety of scientific questions, and the same method may not be best for all questions. Only a handful of validation studies have been done so far, most of which rely on spike-in datasets and focus on the question of detecting differential expression. Here we seek methods that excel at estimating relative expression. We evaluate methods by identifying those that give the strongest linear association between expression measurements by array and the "gold-standard" assay. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) is generally considered the "gold-standard" assay for measuring gene expression by biologists and is often used to confirm findings from microarray data. Here we use qRT-PCR measurements to validate methods for the components of processing oligo array data: background adjustment, normalization, mismatch adjustment, and probeset summary. An advantage of our approach over spike-in studies is that methods are validated on a real dataset that was collected to address a scientific question. RESULTS: We initially identify three of six popular methods that consistently produced the best agreement between oligo array and RT-PCR data for medium- and high-intensity genes. The three methods are generally known as MAS5, gcRMA, and the dChip mismatch mode. For medium- and high-intensity genes, we identified use of data from mismatch probes (as in MAS5 and dChip mismatch) and a sequence-based method of background adjustment (as in gcRMA) as the most important factors in methods' performances. However, we found poor reliability for methods using mismatch probes for low-intensity genes, which is in agreement with previous studies. CONCLUSION: We advocate use of sequence-based background adjustment in lieu of mismatch adjustment to achieve the best results across the intensity spectrum. No method of normalization or probeset summary showed any consistent advantages
Entamoeba histolytica Phagocytosis of Human Erythrocytes Involves PATMK, a Member of the Transmembrane Kinase Family
Entamoeba histolytica is the cause of amebic colitis and liver abscess. This parasite induces apoptosis in host cells and utilizes exposed ligands such as phosphatidylserine to ingest the apoptotic corpses and invade deeper into host tissue. The purpose of this work was to identify amebic proteins involved in the recognition and ingestion of dead cells. A member of the transmembrane kinase family, phagosome-associated TMK96 (PATMK), was identified in a proteomic screen for early phagosomal proteins. Anti-peptide affinity-purified antibody produced against PATMK demonstrated that it was a type I integral membrane protein that was expressed on the trophozoite surface, and that co-localized with human erythrocytes at the site of contact. The role of PATMK in erythrophagocytosis in vitro was demonstrated by: (i) incubation of ameba with anti-PATMK antibodies; (ii) PATMK mRNA knock-down using a novel shRNA expression system; and (iii) expression of a carboxy-truncation of PATMK (PATMKĪ932). Expression of the carboxy-truncation of PATMKĪ932 also caused a specific reduction in the ability of E. histolytica to establish infection in the intestinal model of amebiasis, however these amebae retained the ability to cause hepatic abscesses when directly injected in the liver. In conclusion, PATMK was identified as a member of the TMK family that participates in erythrophagocytosis and is uniquely required for intestinal infection
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Precision farming and archaeology
With a significant growth in the agricultural technology industry a vast amount of agricultural data is now being collected on farms throughout the world. Farmers aim to utilise these technologies to regularly record and manage the variation of crops and soils within their fields, to reduce inputs, increase yields and enhance environmental sustainability. In this paper we aim to highlight the variety of different data types and methodological processes involved in modern precision farming and explore how potentially interconnected these systems are with the archaeological communit
Binary orbits as the driver of Ī³-ray emission and mass ejection in classical novae
Classical novae are the most common astrophysical thermonuclear explosions, occurring on the surfaces of white dwarf stars accreting gas from companions in binary star systems. Novae typically expel ļæ½10,000 solar masses of material at velocities exceeding 1,000 km/s. However, the mechanism of mass ejection in novae is poorly understood, and could be dominated by the impulsive flash of the thermonuclear runaway, prolonged optically thick winds, or binary interaction with the nova envelope. Classical novae are now routinely detected in GeV gamma-rays, suggesting that relativistic particles are accelerated by strong shocks in nova ejecta. Here we present high-resolution imaging of the gamma-ray-emitting nova V959 Mon at radio wavelengths, showing that its ejecta were shaped by binary motion: some gas was expelled rapidly along the poles as a wind from the white dwarf, while denser material drifted out along the equatorial plane, propelled by orbital motion. At the interface between the equatorial and polar regions, we observe synchrotron emission indicative of shocks and relativistic particle acceleration, thereby pinpointing the location of gamma-ray production. Binary shaping of the nova ejecta and associated internal shocks are expected to be widespread among novae, explaining why many novae are gamma-ray emitters
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