Georeferenced soil provenancing with digital signatures.

The provenance or origin of a soil sample is of interest in soil forensics, archaeology, and biosecurity. In all of these fields, highly specialized and often expensive analysis is usually combined with expert interpretation to estimate sample origin. In this proof of concept study we apply rapid and non-destructive spectral analysis to the question of direct soil provenancing. This approach is based on one of the underlying tenets of soil science - that soil pedogenesis is spatially unique, and thus digital spectral signatures of soil can be related directly, rather than via individual soil properties, to a georeferenced location. We examine three different multivariate regression techniques to predict GPS coordinates in two nested datasets. With a minimum of data processing, we show that in most instances Eastings and Northings can be predicted to within 20% of the range of each within the dataset using the spectral signatures produced via portable x-ray fluorescence. We also generate 50 and 95% confidence intervals of prediction and express these as a range of GPS coordinates. This approach has promise for future application in soil and environmental provenancing.

Physical soil architectural traits are functionally linked to carbon decomposition and bacterial diversity.

Aggregates play a key role in protecting soil organic carbon (SOC) from microbial decomposition. The objectives of this study were to investigate the influence of pore geometry on the organic carbon decomposition rate and bacterial diversity in both macro- (250-2000 µm) and micro-aggregates (53-250 µm) using field samples. Four sites of contrasting land use on Alfisols (i.e. native pasture, crop/pasture rotation, woodland) were investigated. 3D Pore geometry of the micro-aggregates and macro-aggregates were examined by X-ray computed tomography (µCT). The occluded particulate organic carbon (oPOC) of aggregates was measured by size and density fractionation methods. Micro-aggregates had 54% less µCT observed porosity but 64% more oPOC compared with macro-aggregates. In addition, the pore connectivity in micro-aggregates was lower than macro-aggregates. Despite both lower µCT observed porosity and pore connectivity in micro-aggregates, the organic carbon decomposition rate constant (Ksoc) was similar in both aggregate size ranges. Structural equation modelling showed a strong positive relationship of the concentration of oPOC with bacterial diversity in aggregates. We use these findings to propose a conceptual model that illustrates the dynamic links between substrate, bacterial diversity, and pore geometry that suggests a structural explanation for differences in bacterial diversity across aggregate sizes.

Effects of carbon dioxide on the searching behaviour of the root-feeding clover weevil Sitona lepidus (Coleoptera: Curculionidae).

The respiratory emission of CO2 from roots is frequently proposed as an attractant that allows soil-dwelling insects to locate host plant roots, but this role has recently become less certain. CO2 is emitted from many sources other than roots, so does not necessarily indicate the presence of host plants, and because of the high density of roots in the upper soil layers, spatial gradients may not always be perceptible by soil-dwelling insects. The role of CO2 in host location was investigated using the clover root weevil Sitona lepidus Gyllenhall and its host plant white clover (Trifolium repens L.) as a model system. Rhizochamber experiments showed that CO2 concentrations were approximately 1000 ppm around the roots of white clover, but significantly decreased with increasing distance from roots. In behavioural experiments, no evidence was found for any attraction by S. lepidus larvae to point emissions of CO2, regardless of emission rates. Fewer than 15% of larvae were attracted to point emissions of CO2, compared with a control response of 17%. However, fractal analysis of movement paths in constant CO2 concentrations demonstrated that searching by S. lepidus larvae significantly intensified when they experienced CO2 concentrations similar to those found around the roots of white clover (i.e. 1000 ppm). It is suggested that respiratory emissions of CO2 may act as a 'search trigger' for S. lepidus, whereby it induces larvae to search a smaller area more intensively, in order to detect location cues that are more specific to their host plant.

Host plant recognition by the root feeding clover weevil, Sitona lepidus (Coleoptera: Curculionidae).

This study investigated the ability of neonatal larvae of the root-feeding weevil, Sitona lepidus Gyllenhal, to locate white clover Trifolium repens L. (Fabaceae) roots growing in soil and to distinguish them from the roots of other species of clover and a co-occurring grass species. Choice experiments used a combination of invasive techniques and the novel technique of high resolution X-ray microtomography to non-invasively track larval movement in the soil towards plant roots. Burrowing distances towards roots of different plant species were also examined. Newly hatched S. lepidus recognized T. repens roots and moved preferentially towards them when given a choice of roots of subterranean clover, Trifolium subterraneum L. (Fabaceae), strawberry clover Trifolium fragiferum L. (Fabaceae), or perennial ryegrass Lolium perenneL. (Poaceae). Larvae recognized T. repens roots, whether released in groups of five or singly, when released 25 mm (meso-scale recognition) or 60 mm (macro-scale recognition) away from plant roots. There was no statistically significant difference in movement rates of larvae.

Interactions and self-organization in the soil-microbe complex.

Soil is the most complicated biomaterial on the planet. As with any material, the physical habitat is of prime importance in determining and regulating biological activity. However, until recently the opaque nature of soil has meant that any interrogation of its interior architecture has been relatively rudimentary, restricted to simple qualitative expressions of the physical heterogeneity that fail to relate to any specific function. However, new techniques and insights into the biophysical and biochemical processes of this inner space are leading to the developments of theoretical frameworks and experimental approaches that will allow us to sustainably manage Earth's most important resource. We introduce the concept that the soil-microbe system is self-organized and suggest new priorities for research based on an integrative approach that combines biochemistry and biophysics.

The impact of bacterial diet on the migration and navigation of Caenorhabditis elegans.

Can diet have a significant impact on the ability of organisms to sense and locate food? Focusing on the bacterial feeder Caenorhabditis elegans, we investigated what effect preconditioning on a range of bacterial substrates had on the subsequent chemotaxis process involved in the nematode locating other bacterial populations. Remarkably, we found that C. elegans, initially fed on a diet of Escherichia coli OP50, was significantly impaired in finding E. coli OP50 populations, compared to other available bacterial populations (P <0.001). We found similar results for another bacterial feeding nematode species, suggesting that a general "substrate legacy" may operate across a wide range of organisms. We discuss this important finding with respect to the variation in response exhibited within a given nematode population, and the impact nematode migration has on bacterial dispersal in the environment.

Does the Presence of Detached Root Border Cells of Zea mays Alter the Activity of the Pathogenic Nematode Meloidogyne incognita?

ABSTRACT The root-knot nematode Meloidogyne incognita is a major pathogen of a range of important crops. Currently, control is typically achieved by the use of nematicides. However, recent work suggests that manipulating the ability of roots to slough off border cells, which then act as a decoy to the nematode, can significantly decrease damage to the roots. We investigated the attractiveness of border cells to M. incognita and the response of the nematode to border cells in close proximity. We found very limited attraction, in that nematodes did not preferentially alter direction to move toward the border cells, but a large and significant increase in nematode speed was observed once they were in the immediate vicinity of border cells. We discuss the results in the context of physical and biological mechanisms in relation to the control of pathogenic nematodes.

Plant roots release phospholipid surfactants that modify the physical and chemical properties of soil.

• Plant root mucilages contain powerful surfactants that will alter the interaction of soil solids with water and ions, and the rates of microbial processes. • The lipid composition of maize, lupin and wheat root mucilages was analysed by thin layer chromatography and gas chromatography-mass spectrometry. A commercially available phosphatidylcholine (lecithin), chemically similar to the phospholipid surfactants identified in the mucilages, was then used to evaluate its effects on selected soil properties. • The lipids found in the mucilages were principally phosphatidylcholines, composed mainly of saturated fatty acids, in contrast to the lipids extracted from root tissues. In soil at low tension, lecithin reduced the water content at any particular tension by as much as 10 and 50% in soil and acid-washed sand, respectively. Lecithin decreased the amount of phosphate adsorption in soil and increased the phosphate concentration in solution by 10%. The surfactant also reduced net rates of ammonium consumption and nitrate production in soil. • These experiments provide the first evidence we are aware of that plant-released surfactants will significantly modify the biophysical environment of the rhizosphere.

In situ spatial patterns of soil bacterial populations, mapped at multiple scales, in an arable soil.

Very little is known about the spatial organization of soil microbes across scales that are relevant both to microbial function and to field-based processes. The spatial distributions of microbes and microbially mediated activity have a high intrinsic variability. This can present problems when trying to quantify the effects of disturbance, management practices, or climate change on soil microbial systems and attendant function. A spatial sampling regime was implemented in an arable field. Cores of undisturbed soil were sampled from a 3 x 3 x 0.9 m volume of soil (topsoil and subsoil) and a biological thin section, in which the in situ distribution of bacteria could be quantified, prepared from each core. Geostatistical analysis was used to quantify the nature of spatial structure from micrometers to meters and spatial point pattern analysis to test for deviations from complete spatial randomness of mapped bacteria. Spatial structure in the topsoil was only found at the microscale (micrometers), whereas evidence for nested scales of spatial structure was found in the subsoil (at the microscale, and at the centimeter to meter scale). Geostatistical ranges of spatial structure at the micro scale were greater in the topsoil and tended to decrease with depth in the subsoil. Evidence for spatial aggregation in bacteria was stronger in the topsoil and also decreased with depth in the subsoil, though extremely high degrees of aggregation were found at very short distances in the deep subsoil. The data suggest that factors that regulate the distribution of bacteria in the subsoil operate at two scales, in contrast to one scale in the topsoil, and that bacterial patches are larger and more prevalent in the topsoil.

Clinical disorders of smell and taste.

Renewed attention to chemosensory dysfunction has revealed that a substantial portion of the population are affected during their lives, many simply as a result of aging. The authors discuss terminology, assessment, etiology, and prognosis and compare current understanding with that presented by Mackenzie in 1884.

Fastpac visual field screening.

In epidemiology, screening for visual field defects has traditionally been expensive, time consuming and laborious. To achieve cost- and time-effective visual field screening, a faster algorithm has been developed for the Humphrey perimeter called Fastpac, which is designed to achieve threshold perimetry in two-thirds the time of the standard algorithm. We compared the Fastpac and conventional full-threshold 24-2 fields obtained in 39 eyes of 36 participants. We divided the participants' fields into normal (14) and glaucomatous (25) visual field groups, and compared the test times, number of questions asked and statistical parameters generated for each field for Fastpac as compared to the standard algorithm. Then we divided the participants' fields into Fastpac and standard fields and again compared the test times, number of questions and statistical parameters. Finally we asked trained observers to judge the fields as being normal or abnormal, in a masked fashion, and found a high degree of agreement between the fields generated by Fastpac and standard. Fastpac offers accurate full-threshold screening in two-thirds the time of the conventional algorithm and would be very useful for large scale prevalence studies in ophthalmic epidemiology.

Excimer laser lamellar keratoplasty.

PURPOSE: To evaluate a procedure using the excimer laser to perform lamellar keratoplasty to treat deep corneal scars in the central optical zone. To determine if excimer laser can safely prepare a smooth surface for the host bed and the donor button, assess the interface opacity and evaluate the effects of the ablation on the recipient's endothelial surface with the deeper ablation. METHODS: Nineteen rabbits underwent an excimer laser lamellar keratoplasty in one eye. The rabbits were followed for 9 to 12 weeks until they were sacrificed. RESULTS: Little opacity developed at the graft-host interface and scanning electron microscopy of the endothelial surface showed little difference between the treated and untreated areas or the endothelium of the untreated eyes. CONCLUSIONS: Our results suggest that the use of the excimer laser to treat corneas with deep stromal scars and normal endothelium is feasible. However, we have not proved that this technique will give a better result than conventional lamellar dissection methods.

Comparison between Fastpac and conventional Humphrey perimetry.

As part of the Melbourne Visual Impairment Project, a substudy was performed to determine the efficacy of the newly released Fastpac program for the Humphrey Field Analyser. A comparison was performed of the Fastpac and conventional full threshold 24-2 fields obtained in 39 eyes of 36 participants. Also a comparison study was performed of the standard and non-standard 80-point screening tests to the standard 24-2 full threshold test in 23 eyes of 23 participants. In the full threshold comparison there was 100% agreement between the two with Fastpac being 32% to 39% faster than standard. In the 80-point screening test comparison, non-standard was no faster than standard. Sensitivities were 17/17 (1.0) for non-standard and 15/18 (0.83) for standard, as compared with the standard 24-2 full threshold test. Fastpac software offers accurate screening and threshold testing in less time than the standard algorithm.

Mechanics of caloric stimulation in a case with a plug in the horizontal semicircular canal.

Horizontal eye movements were recorded by electronystagmography in a subject with a plug of granulation tissue in the unilateral horizontal semicircular canal by the room temperature air caloric stimulation. Stimuli were sequentially presented to both ears with the subject supine and prone, keeping the horizontal canal vertical. Caloric stimuli presented to the unplugged ear resulted in a vestibular nystagmus whose slow phase eye velocity (SPEV) was always directed toward the stimulated side when the subject was supine and toward the opposite side when he was prone. In contrast, calorics presented to the horizontal canal plugged ear showed that SPEV was always directed toward the stimulated side, irrespective of whether the subject was supine or prone. Results were consistent with consensus that the caloric responses noted in the horizontal canal plugged ear reflected horizontal canal afferent activity which may correspond to direct effect of temperature on end organs or afferents. The findings imply that a caloric mechanism exists which is independent of the conventionally accepted one involving concection currents within the canal.

Non-oral etiologies of oral malodor and altered chemosensation.

A number of non-oral causes for oral malodor have been discussed. Several well documented etiologies for non-oral malodor include renal failure, cirrhosis of the liver, and diabetes mellitus. Each of these conditions has been examined using analytical instrumentation. In addition there appear to be several other metabolic conditions involving enzymatic and transport anomalies (such as trimethylaminuria) which lead to the systemic production of volatile malodors that manifest themselves as halitosis and/or altered chemoreception. Our studies include patients who have been referred to us after being examined by numerous clinical specialists with no identification or relief from their problem. This is due in part to the intermittent nature of many of these problems as well as an apparent lack of knowledge concerning many of these metabolic problems and their relation to oral symptoms.

Time-intensity relations in Békésy audiometry.

Threshold and amplitude measurements were made for fixed frequency Bekesy pure tones on subjects with normal hearing, sensorineural hearing impairment, and functional hearing loss. Following conventional Bekesy audiometry (intensity change 4 dB/sec), -20 dB was added to a signal at the threshold of audibility (bottom of the spike). When sensation was lost at the threshold of inaudibility (top of the spike), +20 dB was added. Adding +/- 20 dB in subjects with normal hearing reduced the amplitude of the spike about 4 dB, corresponding to 1 second, for both pulsed and continuous tones. Adding +/- 40 dB produced essentially similar findings. Adding +/- 20 dB in subjects with sensorineural loss with reduced amplitude of continuous tone tracings also reduced the amplitude approximately 4 dB for pulsed tones, but 3 dB, corresponding to 0.75 seconds, for continuous tones. Abnormal rapid adaptation may account for this reduced amplitude of the spikes. A subject with multiple sclerosis producing excessive abnormal adaptation showed spectacular increased amplitude for continuous tone only when -20 dB was added at bottoms and +20 dB at tops of spikes. An explanation based on slow adaptation is offered. Subjects with functional hearing loss may emphasize either time or intensity in their inappropriate responses when +/- 20 dB is added at tops and/or bottoms of spikes.

Dinoprost 14-day oestrus synchronisation schedule for dairy cows.

Oestrus and ovulation were synchronised in 82 lactating Friesian dairy cows with two injections of dinoprost, and the cows were inseminated 72 and 96 hours after the second injection. Twenty-one of the 41 cows (51 per cent) which had a 14-day interval between the dinoprost injections conceived to the inseminations, compared with 18 of the 41 cows (44 per cent) which had an 11-day interval between the injections.

Decruitment and abnormal auditory adaptation.

1. Factual findings related to decruitment have been presented. 2. Decruitment is considered to be a manifestation of eighth nerve involvement indicating abnormal adaptation. 3. Loudness match as a quick screening test may be applied in cases of suspected abnormal auditory adaptation.