A Beginner's Guide to Eddy Covariance: Methodology and Its Applications to Photosynthesis

The eddy covariance technique, commonly applied using flux towers, enables the investigation of greenhouse gas (e.g., carbon dioxide, methane, nitrous oxide) and energy (latent and sensible heat) fluxes between the biosphere and the atmosphere. Through measuring carbon fluxes in particular, eddy covariance flux towers can give insight into how ecosystem scale photosynthesis (i.e., gross primary productivity) changes over time in response to climate and management. This chapter is designed to be a beginner's guide to understanding the eddy covariance method and how it can be applied in photosynthesis research. It introduces key concepts and assumptions that apply to the method, what materials are required to set up a flux tower, as well as practical advice for site installation, maintenance, data management, and postprocessing considerations. This chapter also includes examples of what can go wrong, with advice on how to correct these errors if they arise. This chapter has been crafted to help new users design, install, and manage the best towers to suit their research needs and includes additional resources throughout to further guide successful eddy covariance research activities.

Effects of Bacillus subtilis PB6 supplementation on production, metabolism, inflammatory biomarkers, and gastrointestinal tract permeability in transition dairy cows

Objectives were to evaluate the effects of Bacillus subtilis PB6 (BSP) on gastrointestinal tract permeability, metabolism, inflammation, and production parameters in periparturient Holstein cows. Multiparous cows (n = 48) were stratified by previous 305-d mature equivalent milk yield and parity and assigned to 1 of 2 top-dressed dietary treatments 21 d before expected calving through 63 DIM: (1) control (CON; 13 g/d calcium carbonate; n = 24) or (2) BSP (13 g/d BSP; CLOSTAT, Kemin Industries, Des Moines, IA; n = 24). Gastrointestinal tract permeability was evaluated in vivo using the oral paracellular marker chromium (Cr)-EDTA. Effects of treatment, time, and treatment × time were assessed using PROC MIXED of SAS version 9.4 (SAS Institute Inc.). Prepartum dry matter intake (DMI) was unaffected by treatment; however, BSP supplementation decreased postpartum DMI relative to CON (0.7 kg). Milk yield, energy-corrected milk (ECM), fat-corrected milk (FCM), and solids-corrected milk (SCM) increased in BSP cows compared with CON (1.6, 1.8, 1.6, and 1.5 kg, respectively). Decreased DMI and increased production collectively improved feed efficiency of milk yield, ECM, FCM, and SCM for BSP cows (6, 5, 5, and 5%, respectively). No treatment differences were observed for concentrations of milk fat, protein, total solids, somatic cell count, somatic cell score, body weight, or body condition score. Milk urea nitrogen concentrations decreased (5%), whereas milk protein and lactose yield increased (5 and 2%, respectively) with BSP supplementation. Prepartum fecal pH did not differ among treatments; conversely, postpartum fecal pH was increased with BSP supplementation (0.09 pH units). Prepartum fecal dry matter percentage, starch, acetic acid, propionic acid, butyric acid, and ethanol did not differ among treatments. Postpartum concentrations of the aforementioned fecal parameters were also unaffected by treatment, but fecal propionic acid concentration was decreased (24%) in BSP cows relative to CON. Circulating glucose, nonesterified fatty acids, l-lactate, and insulin were similar between treatments both pre- and postpartum. Prepartum β-hydroxybutyrate (BHB) did not differ between treatments, but postpartum BSP supplementation decreased (21%) circulating BHB relative to CON. Regardless of treatment, inflammatory markers (serum amyloid A and haptoglobin) peaked immediately following parturition and progressively decreased with time, but this pattern was not influenced by treatment. Postpartum lipopolysaccharide binding protein tended to be decreased on d 3 in BSP relative to CON cows (19%). Neither treatment nor time affected Cr-EDTA area under the curve. In summary, supplementing BSP had no detectable effects prepartum, but increased key postpartum production parameters. Bacillus subtilis PB6 consistently increased postpartum fecal pH and decreased fecal propionate concentrations but did not appear to have an effect on gastrointestinal tract permeability.

Improved net carbon budgets in the US Midwest through direct measured impacts of enhanced weathering

Terrestrial enhanced weathering (EW) through the application of Mg- or Ca-rich rock dust to soil is a negative emission technology with the potential to address impacts of climate change. The effectiveness of EW was tested over 4 years by spreading ground basalt (50 t ha-1  year-1 ) on maize/soybean and miscanthus cropping systems in the Midwest US. The major elements of the carbon budget were quantified through measurements of eddy covariance, soil carbon flux, and biomass. The movement of Mg and Ca to deep soil, released by weathering, balanced by a corresponding alkalinity flux, was used to measure the drawdown of CO2 , where the release of cations from basalt was measured as the ratio of rare earth elements to base cations in the applied rock dust and in the surface soil. Basalt application stimulated peak biomass and net primary production in both cropping systems and caused a small but significant stimulation of soil respiration. Net ecosystem carbon balance (NECB) was strongly negative for maize/soybean (-199 to -453 g C m-2  year-1 ) indicating this system was losing carbon to the atmosphere. Average EW (102 g C m-2  year-1 ) offset carbon loss in the maize/soybean by 23%-42%. NECB of miscanthus was positive (63-129 g C m-2  year-1 ), indicating carbon gain in the system, and EW greatly increased inorganic carbon storage by an additional 234 g C m-2  year-1 . Our analysis indicates a co-deployment of a perennial biofuel crop (miscanthus) with EW leads to major wins-increased harvested yields of 29%-42% with additional carbon dioxide removal (CDR) of 8.6 t CO2  ha-1  year-1 . EW applied to maize/soybean drives a CDR of 3.7 t CO2  ha-1  year-1 , which partially offsets well-established carbon losses from soil from this crop rotation. EW applied in the US Midwest creates measurable improvements to the carbon budgets perennial bioenergy crops and conventional row crops.

Bridge to the future: Important lessons from 20 years of ecosystem observations made by the OzFlux network

In 2020, the Australian and New Zealand flux research and monitoring network, OzFlux, celebrated its 20th anniversary by reflecting on the lessons learned through two decades of ecosystem studies on global change biology. OzFlux is a network not only for ecosystem researchers, but also for those 'next users' of the knowledge, information and data that such networks provide. Here, we focus on eight lessons across topics of climate change and variability, disturbance and resilience, drought and heat stress and synergies with remote sensing and modelling. In distilling the key lessons learned, we also identify where further research is needed to fill knowledge gaps and improve the utility and relevance of the outputs from OzFlux. Extreme climate variability across Australia and New Zealand (droughts and flooding rains) provides a natural laboratory for a global understanding of ecosystems in this time of accelerating climate change. As evidence of worsening global fire risk emerges, the natural ability of these ecosystems to recover from disturbances, such as fire and cyclones, provides lessons on adaptation and resilience to disturbance. Drought and heatwaves are common occurrences across large parts of the region and can tip an ecosystem's carbon budget from a net CO2 sink to a net CO2 source. Despite such responses to stress, ecosystems at OzFlux sites show their resilience to climate variability by rapidly pivoting back to a strong carbon sink upon the return of favourable conditions. Located in under-represented areas, OzFlux data have the potential for reducing uncertainties in global remote sensing products, and these data provide several opportunities to develop new theories and improve our ecosystem models. The accumulated impacts of these lessons over the last 20 years highlights the value of long-term flux observations for natural and managed systems. A future vision for OzFlux includes ongoing and newly developed synergies with ecophysiologists, ecologists, geologists, remote sensors and modellers.

A review of transformative strategies for climate mitigation by grasslands

Grasslands can significantly contribute to climate mitigation. However, recent trends indicate that human activities have switched their net cooling effect to a warming effect due to management intensification and land conversion. This indicates an urgent need for strategies directed to mitigate climate warming while enhancing productivity and efficiency in the use of land and natural (nutrients, water) resources. Here, we examine the potential of four innovative strategies to slow climate change including: 1) Adaptive multi-paddock grazing that consists of mimicking how ancestral herds roamed the Earth; 2) Agrivoltaics that consists of simultaneously producing food and energy from solar panels on the same land area; 3) Agroforestry with a reverse phenology tree species, Faidherbia (Acacia) albida, that has the unique trait of being photosynthetically active when intercropped herbaceous plants are dormant; and, 4) Enhanced Weathering, a negative emission technology that removes atmospheric CO₂ from the atmosphere. Further, we speculate about potential unknown consequences of these different management strategies and identify gaps in knowledge. We find that all these strategies could promote at least some of the following benefits of grasslands: CO₂ sequestration, non-CO₂ GHG mitigation, productivity, resilience to climate change, and an efficient use of natural resources. However, there are obstacles to be overcome. Mechanistic assessment of the ecological, environmental, and socio-economic consequences of adopting these strategies at large scale are urgently needed to fully assess the potential of grasslands to provide food, energy and environmental security.

Quantifying high-temperature stress on soybean canopy photosynthesis: The unique role of sun-induced chlorophyll fluorescence

High temperature and accompanying high vapor pressure deficit often stress plants without causing distinctive changes in plant canopy structure and consequential spectral signatures. Sun-induced chlorophyll fluorescence (SIF), because of its mechanistic link with photosynthesis, may better detect such stress than remote sensing techniques relying on spectral reflectance signatures of canopy structural changes. However, our understanding about physiological mechanisms of SIF and its unique potential for physiological stress detection remains less clear. In this study, we measured SIF at a high-temperature experiment, Temperature Free-Air Controlled Enhancement, to explore the potential of SIF for physiological investigations. The experiment provided a gradient of soybean canopy temperature with 1.5, 3.0, 4.5, and 6.0°C above the ambient canopy temperature in the open field environments. SIF yield, which is normalized by incident radiation and the fraction of absorbed photosynthetically active radiation, showed a high correlation with photosynthetic light use efficiency (r = 0.89) and captured dynamic plant responses to high-temperature conditions. SIF yield was affected by canopy structural and plant physiological changes associated with high-temperature stress (partial correlation r = 0.60 and -0.23). Near-infrared reflectance of vegetation, only affected by canopy structural changes, was used to minimize the canopy structural impact on SIF yield and to retrieve physiological SIF yield (ΦF ) signals. ΦF further excludes the canopy structural impact than SIF yield and indicates plant physiological variability, and we found that ΦF outperformed SIF yield in responding to physiological stress (r = -0.37). Our findings highlight that ΦF sensitively responded to the physiological downregulation of soybean gross primary productivity under high temperature. ΦF , if reliably derived from satellite SIF, can support monitoring regional crop growth and different ecosystems' vegetation productivity under environmental stress and climate change.

The effect of increasing temperature on crop photosynthesis: from enzymes to ecosystems

As global land surface temperature continues to rise and heatwave events increase in frequency, duration, and/or intensity, our key food and fuel cropping systems will likely face increased heat-related stress. A large volume of literature exists on exploring measured and modelled impacts of rising temperature on crop photosynthesis, from enzymatic responses within the leaf up to larger ecosystem-scale responses that reflect seasonal and interannual crop responses to heat. This review discusses (i) how crop photosynthesis changes with temperature at the enzymatic scale within the leaf; (ii) how stomata and plant transport systems are affected by temperature; (iii) what features make a plant susceptible or tolerant to elevated temperature and heat stress; and (iv) how these temperature and heat effects compound at the ecosystem scale to affect crop yields. Throughout the review, we identify current advancements and future research trajectories that are needed to make our cropping systems more resilient to rising temperature and heat stress, which are both projected to occur due to current global fossil fuel emissions.

The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

The FLUXNET2015 dataset provides ecosystem-scale data on CO₂, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.

Measurement(s)	net ecosystem exchange • carbon dioxide • water • energy
Technology Type(s)	eddy covariance • measurement device
Sample Characteristic - Environment	terrestrial biome • atmosphere
Sample Characteristic - Location	Earth (planet)

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12295910

High-throughput field phenotyping using hyperspectral reflectance and partial least squares regression (PLSR) reveals genetic modifications to photosynthetic capacity

Spectroscopy is becoming an increasingly powerful tool to alleviate the challenges of traditional measurements of key plant traits at the leaf, canopy, and ecosystem scales. Spectroscopic methods often rely on statistical approaches to reduce data redundancy and enhance useful prediction of physiological traits. Given the mechanistic uncertainty of spectroscopic techniques, genetic modification of plant biochemical pathways may affect reflectance spectra causing predictive models to lose power. The objectives of this research were to assess over two separate years, whether a predictive model can represent natural and imposed variation in leaf photosynthetic potential for different crop cultivars and genetically modified plants, to assess the interannual capabilities of a partial least square regression (PLSR) model, and to determine whether leaf N is a dominant driver of photosynthesis in PLSR models. In 2016, a PLSR analysis of reflectance spectra coupled with gas exchange data was used to build predictive models for photosynthetic parameters including maximum carboxylation rate of Rubisco (V _c,max ), maximum electron transport rate (J _max ) and percentage leaf nitrogen ([N]). The model was developed for wild type and genetically modified plants that represent a wide range of photosynthetic capacities. Results show that hyperspectral reflectance accurately predicted V _c,max, J _max and [N] for all plants measured in 2016. Applying these PLSR models to plants grown in 2017 resulted in a strong predictive ability relative to gas exchange measurements for V _c,max, but not for J _max, and not for genotypes unique to 2017. Building a new model including data collected in 2017 resulted in more robust predictions, with R² increases of 17% for V _c,max . and 13% J _max . Plants generally have a positive correlation between leaf nitrogen and photosynthesis, however, tobacco with reduced Rubisco (SSuD) had significantly higher [N] despite much lower V _c,max. The PLSR model was able to accurately predict both lower V _c,max and higher leaf [N] for this genotype suggesting that the spectral based estimates of V _c,max and leaf nitrogen [N] are independent. These results suggest that the PLSR model can be applied across years, but only to genotypes used to build the model and that the actual mechanism measured with the PLSR technique is not directly related to leaf [N]. The success of the leaf-scale analysis suggests that similar approaches may be successful at the canopy and ecosystem scales but to use these methods across years and between genotypes at any scale, application of accurately populated physical based models based on radiative transfer principles may be required.

Epidemiology of paediatric gastrointestinal colonisation by extended spectrum cephalosporin-resistant Escherichia coli and Klebsiella pneumoniae isolates in north-west Cambodia

Background

Extended-spectrum cephalosporin resistance (ESC-R) in Escherichia coli and Klebsiella pneumoniae is a healthcare threat; high gastrointestinal carriage rates are reported from South-east Asia. Colonisation prevalence data in Cambodia are lacking. The aim of this study was to determine gastrointestinal colonisation prevalence of ESC-resistant E. coli (ESC-R-EC) and K. pneumoniae (ESC-R-KP) in Cambodian children/adolescents and associated socio-demographic risk factors; and to characterise relevant resistance genes, their genetic contexts, and the genetic relatedness of ESC-R strains using whole genome sequencing (WGS).

Results

Faeces and questionnaire data were obtained from individuals < 16 years in north-western Cambodia, 2012. WGS of cultured ESC-R-EC/KP was performed (Illumina). Maximum likelihood phylogenies were used to characterise relatedness of isolates; ESC-R-associated resistance genes and their genetic contexts were identified from de novo assemblies using BLASTn and automated/manual annotation. 82/148 (55%) of children/adolescents were ESC-R-EC/KP colonised; 12/148 (8%) were co-colonised with both species. Independent risk factors for colonisation were hospitalisation (OR: 3.12, 95% CI [1.52–6.38]) and intestinal parasites (OR: 3.11 [1.29–7.51]); school attendance conferred decreased risk (OR: 0.44 [0.21–0.92]. ESC-R strains were diverse; the commonest ESC-R mechanisms were bla_CTX-M 1 and 9 sub-family variants. Structures flanking these genes were highly variable, and for bla_{CTX-M-15, − 55 and − 27} frequently involved IS26. Chromosomal bla_CTX-M integration was common in E. coli.

Conclusions

Gastrointestinal ESC-R-EC/KP colonisation is widespread in Cambodian children/adolescents; hospital admission and intestinal parasites are independent risk factors. The genetic contexts of bla_CTX-M are highly mosaic, consistent with rapid horizontal exchange. Chromosomal integration of bla_CTX-M may result in stable propagation in these community-associated pathogens.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1431-9) contains supplementary material, which is available to authorized users.

Plasma and synovial fluid concentrations and cartilage toxicity of bupivacaine following intra-articular administration of a liposomal formulation to horses

BACKGROUND

The use of intra-articular (IA) local anaesthetics has proven to be an effective means to treat post-operative pain. The effects of local anaesthetics on equine chondrocytes are mixed with some studies reporting chondrodestruction and others no adverse effects. A liposomal formulation of bupivacaine is used in people and dogs by intra- and peri-articular administration to provide up to 72 h of analgesia. The potential uses, side effects including chondrotoxicity, and likelihood of abuse (long-term analgesic effects) has not been evaluated in horses.

OBJECTIVES

Describe bupivacaine concentrations following IA administration and assess biomarkers as indicators of the effects of liposomal bupivacaine on chondrocytes in vivo.

STUDY DESIGN

Parallel design.

METHODS

Sixteen exercised horses received a single IA administration of 0.12 mg/kg liposomal bupivacaine or 0.9% saline. Blood and urine samples were collected for 96 h post-drug administration. Six horses treated with bupivacaine and those receiving saline, underwent daily arthrocentesis. Six additional bupivacaine treated horses underwent arthrocentesis at 96 h. Drug concentrations were measured using LC-MS/MS and pharmacokinetic analyses performed. Immunoassays were used to measure markers of collagen degradation (C2C, C12C) and cartilage matrix synthesis (CPII, CS846) in synovial fluid.

RESULTS

The bupivacaine plasma elimination half-life was 17.8 ± 5.42 and 11.9 ± 5.17 h for horses from which synovial fluid was collected daily and at 96 h respectively. Bupivacaine concentrations in the joint were still detectable at 96 h. Significant increases in C12C and C2C were noted at 96 h in horses undergoing arthrocentesis at 96 h only. CPII was increased at 48 h and CS846 at 24 and 48 h in horses sampled daily.

MAIN LIMITATIONS

Limited number of animals and absence of liposome control group.

CONCLUSIONS

Sustained concentrations of IA bupivacaine suggest viability of this medication as an intra-articular analgesic. Effects on equine chondrocytes need further study.

Seasonal, interannual and decadal drivers of tree and grass productivity in an Australian tropical savanna

Tree-grass savannas are a widespread biome and are highly valued for their ecosystem services. There is a need to understand the long-term dynamics and meteorological drivers of both tree and grass productivity separately in order to successfully manage savannas in the future. This study investigated the interannual variability (IAV) of tree and grass gross primary productivity (GPP) by combining a long-term (15 year) eddy covariance flux record and model estimates of tree and grass GPP inferred from satellite remote sensing. On a seasonal basis, the primary drivers of tree and grass GPP were solar radiation in the wet season and soil moisture in the dry season. On an interannual basis, soil water availability had a positive effect on tree GPP and a negative effect on grass GPP. No linear trend in the tree-grass GPP ratio was observed over the 15-year study period. However, the tree-grass GPP ratio was correlated with the modes of climate variability, namely the Southern Oscillation Index. This study has provided insight into the long-term contributions of trees and grasses to savanna productivity, along with their respective meteorological determinants of IAV.

Susceptibility artifacts detected on 3T MRI of the knee: frequency, change over time and associations with radiographic findings: data from the joints on glucosamine study

OBJECTIVE

To determine the prevalence of intraarticular susceptibility artifacts and to detect longitudinal changes in the artifacts, on 3T magnetic resonance imaging (MRI) of the knee in a cohort of patients with knee pain, and to assess the association of susceptibility artifacts with radiographic intraarticular calcifications.

DESIGN

Three hundred and forty-six knees of 177 subjects aged 35-65 were included. 3T MRI was performed at baseline and at 6 months. Baseline radiographs were assessed for presence/absence of linear/punctate calcifications within the tibiofemoral joint (TFJ) space. Corresponding MRIs were assessed for susceptibility artifacts (i.e., linear/punctate hypointensities) in the TFJ space on coronal dual-echo steady-state (DESS) sequences. Kappa statistics were applied to determine agreement between findings on baseline DESS and radiography. Changes in artifacts over time were recorded.

RESULTS

In the medial compartment, 13 (4%) of the knees showed susceptibility artifacts at baseline. Six knees had persistent artifacts and six knees had incident artifacts at follow-up. Agreement between DESS and radiography was κ = 0.18 (-0.15, 0.51) in the medial compartment. Frequency of artifacts in the lateral compartment was low (2%).

CONCLUSION

Susceptibility artifacts detected on knee MRI are not frequent, and likely correspond to vacuum phenomena as they commonly change over time and are not associated with intraarticular calcifications. Radiologists should be aware of these artifacts as they can interfere with cartilage segmentation.

Septic arthritis of the hip in a Cambodian child caused by multidrug-resistant Salmonella enterica serovar Typhi with intermediate susceptibility to ciprofloxacin treated with ceftriaxone and azithromycin

Septic arthritis is a rare complication of typhoid fever. A 12-year-old boy without pre-existing disease attended a paediatric hospital in Cambodia with fever and left hip pain. A hip synovial fluid aspirate grew multidrug-resistant Salmonella enterica ser. Typhi with intermediate susceptibility to ciprofloxacin. Arthrotomy, 2 weeks of intravenous ceftriaxone and 4 weeks of oral azithromycin led to resolution of symptoms. The optimum management of septic arthritis in drug-resistant typhoid is undefined.

Healthcare-associated outbreak of meticillin-resistant Staphylococcus aureus bacteraemia: role of a cryptic variant of an epidemic clone

Background

New strains of meticillin-resistant Staphylococcus aureus (MRSA) may be associated with changes in rates of disease or clinical presentation. Conventional typing techniques may not detect new clonal variants that underlie changes in epidemiology or clinical phenotype.

Aim

To investigate the role of clonal variants of MRSA in an outbreak of MRSA bacteraemia at a hospital in England.

Methods

Bacteraemia isolates of the major UK lineages (EMRSA-15 and -16) from before and after the outbreak were analysed by whole-genome sequencing in the context of epidemiological and clinical data. For comparison, EMRSA-15 and -16 isolates from another hospital in England were sequenced. A clonal variant of EMRSA-16 was identified at the outbreak hospital and a molecular signature test designed to distinguish variant isolates among further EMRSA-16 strains.

Findings

By whole-genome sequencing, EMRSA-16 isolates during the outbreak showed strikingly low genetic diversity (P < 1 × 10⁻⁶, Monte Carlo test), compared with EMRSA-15 and EMRSA-16 isolates from before the outbreak or the comparator hospital, demonstrating the emergence of a clonal variant. The variant was indistinguishable from the ancestral strain by conventional typing. This clonal variant accounted for 64/72 (89%) of EMRSA-16 bacteraemia isolates at the outbreak hospital from 2006.

Conclusions

Evolutionary changes in epidemic MRSA strains not detected by conventional typing may be associated with changes in disease epidemiology. Rapid and affordable technologies for whole-genome sequencing are becoming available with the potential to identify and track the emergence of variants of highly clonal organisms.

The value of intermittent point-prevalence surveys of healthcare-associated infections for evaluating infection control interventions at Angkor Hospital for Children, Siem Reap, Cambodia

Background

There are limited data on the epidemiology of paediatric healthcare-associated infection (HCAI) and infection control in low-income countries. We describe the value of intermittent point-prevalence surveys for monitoring HCAI and evaluating infection control interventions in a Cambodian paediatric hospital.

Methods

Hospital-wide, point-prevalence surveys were performed monthly in 2011. Infection control interventions introduced during this period included a hand hygiene programme and a ventilator-associated pneumonia (VAP) care bundle.

Results

Overall HCAI prevalence was 13.8/100 patients at-risk, with a significant decline over time. The highest HCAI rates (50%) were observed in critical care; the majority of HCAIs were respiratory (61%). Klebsiella pneumoniae was most commonly isolated and antimicrobial resistance was widespread. Hand hygiene compliance doubled to 51.6%, and total VAP cases/1000 patient-ventilator days fell from 30 to 10.

Conclusion

Rates of HCAI were substantial in our institution, and antimicrobial resistance a major concern. Point-prevalence surveys are effective for HCAI surveillance, and in monitoring trends in response to infection control interventions.

The Importance of Oxidation or Glycosylation of Low-density Lipoproteins in Relation to Platelet Activation

Low-density lipoproteins (LDL) are thought to influence directly the sensitivity of platelets, but this may only be the case when the LDL are modified by oxidation. In diabetes, LDL are known to be modified by non-enzymatic glycosylation, especially when the blood glucose concentrations are poorly controlled: platelet activation is also concomitantly increased as is the concentration of plasma lipid peroxides. In this study we found that mild oxidation of LDL in vitro is more potent than strongly oxidised LDL in terms of the activation of platelets. Glycosylation of LDL per se has little effect on the aggregation of isolated platelets.

[Orbital invasion of a maxillary ameloblastoma]

A 66-year-old man with a history of repeated surgery, external radiation and brachytherapy for ameloblastoma presented with a recurrence of the tumor with sinus, intraorbital and skull base infiltration. Histopathologic examination of the resected orbital and sinus tissue confirmed the diagnosis of ameloblastoma. Immunohistochemical staining for CD56 was strongly positive in the tumor cells. Although ameloblastoma is usually a low-grade malignant tumor, it can be locally aggressive with invasion of the surrounding tissue. Maxillary ameloblastomas are more likely to infiltrate the orbit.

Patient safety incidents associated with obesity: a review of reports to the National Patient Safety Agency and recommendations for hospital practice

BACKGROUND

The incidence and prevalence of obesity are increasing world wide. In the UK, obesity governmental strategy has primarily focused on prevention measures, with less focus on the demands of treating obese patients in hospital. Increasing service demand by obese patients coupled with a lack of adequate provision for care of these patients may lead to an increase in patient safety incidents. By classifying patient safety incidents associated with obesity reported to the National Patient Safety Agency, this report aims to identify areas for improvement in the quality and safety of care of the obese patient.

METHODS

A search of the National Reporting and Learning System database was conducted for all incidents caused by or relating to obesity for the period 1 January 2005 to 31 August 2008. The keywords 'obesity', 'overweight', 'BMI' (body mass index), and 'bariatric' were used. The relevant free text fields of the resulting set of incidents were then searched for the terms designed to isolate incidents occurring in anaesthesia, critical care, and surgery. Reported incidents were analysed and subsequently categorised to identify incident themes. Levels of harm were also established.

RESULTS

555 patient safety incidents were identified; 388 met inclusion criteria for analysis. 148 incidents were related to assessment, diagnosis or treatment, 213 related to infrastructure and 27 related to staffing. The majority of incidents were classified as no or low harm. Three deaths were reported, all within the domain of anaesthesia.

CONCLUSIONS

This report identifies that the majority of safety incidents associated with obesity were related to infrastructure, suggesting that there is inadequate provision in place for the care of obese patients. While levels of harm were mostly low, the occurrence of incidents resulting in severe harm or death highlights the specific dangers associated with the care of the obese patient. A global approach to improving the safety of care delivery for obese patients is recommended, including obesity specific training, management structures, care pathways, and equipment provisioning.Further planning and development of operation policies is needed to ensure the safe delivery of healthcare to obese patients in the future.

Craniofacial resection: decreased complication rate with a modified subcranial approach

The authors have successfully utilized a modified subcranial approach to the anterior skull base, based upon the procedure first described by Joram Raveh, as an alternative to standard craniofacial resection. The complication rate of this procedure in 31 consecutive cases (28 tumors, 2 congenital malformations, and 1 mucocele) has been 19.4% with no permanent complications, no deaths, no new neurological deficits, no brain injuries, no infections, and no seizures. Minor complications without permanent sequelae included two cases of tension pnenmocephalus, a subdural hygroma, two transient cerebrospinal fluid leaks, and a case of bacterial meningitis secondary to fecal contamination of a lumbar drain in a child. Average length of hospitalization was 7.1 days (range 2 to 16 days). The overall complication rate is considerably below the complication rate for other reported craniofacial procedures. We describe the technique we have used and the results. The subcranial approach as described herein provides wide exposure of the anterior cranial base without brain retraction, does not require prolonged operating times or hospitalization, and has a potentially lower complication rate than reported for other transfrontal transbasal approaches.

Adolescent awareness of risk factors associated with head and neck cancer vs lung cancer

This study investigates the knowledge base of adolescents as it relates to their awareness of tobacco use being a major risk factor for the development of malignancies of the head and neck. To gain a more comprehensive perspective, we compared this to their knowledge of the association of tobacco and lung cancer. Data were obtained from a questionnaire survey given to participants at community health screening. A total of 139 participants were included, of which 36.7% were under the age of 18 years old. Participants were asked to indicate if they were aware of the effects of tobacco and lung cancer, as well as tobacco and head and neck cancer. The results showed that 82.4% were able to identify tobacco as a risk factor for lung cancer, while only 15.7% made a similar association with head and neck cancer. These results highlight the need for increased awareness in the vulnerable population.

NFKBIZ polymorphisms and susceptibility to pneumococcal disease in European and African populations

The proinflammatory transcription factor nuclear factor-kappaB (NF-kappaB) has a central role in host defence against pneumococcal disease. Both rare mutations and common polymorphisms in the NFKBIA gene encoding the NF-kappaB inhibitor, IkappaB-alpha, associate with susceptibility to bacterial disease, but the possible role of polymorphisms within the related IkappaB-zeta gene NFKBIZ in the development of invasive pneumococcal disease (IPD) has not been reported previously. To investigate this further, we examined the frequencies of 22 single-nucleotide polymorphisms spanning NFKBIZ in two case-control studies, comprising UK Caucasian (n=1008) and Kenyan (n=723) individuals. Nine polymorphisms within a single UK linkage disequilibrium (LD) block and all four polymorphisms within the equivalent, shorter Kenyan LD block displayed either a significant association with IPD or a trend towards association. For each polymorphism, heterozygosity was associated with protection from IPD when compared with the combined homozygous states (for example, for rs600718, Mantel-Haenszel 2 x 2 chi(2)=7.576, P=0.006, odds ratio (OR)=0.67, 95% confidence interval (95% CI) for OR: 0.51-0.88; for rs616597, Mantel-Haenszel 2 x 2 chi(2)=8.715, P=0.003, OR=0.65, 95% CI: 0.49-0.86). We conclude that multiple NFKBIZ polymorphisms associate with susceptibility to IPD in humans. The study of multiple populations may aid in fine mapping of associations within extensive regions of strong LD ('transethnic mapping').

Seroprotection against serogroup C meningococcal disease in adolescents in the United Kingdom: observational study

OBJECTIVE

To determine the persistence of bactericidal antibody titres following immunisation with serogroup C meningococcal glycoconjugate vaccine at age 6-15 years in order to examine changes in persistence of antibodies with age.

DESIGN

Observational study.

SETTING

Secondary and tertiary educational institutions in the United Kingdom.

PARTICIPANTS

Healthy adolescents aged 11-20 years previously immunised between 6 and 15 years of age with one of the three serogroup C meningococcal vaccines.

INTERVENTION

Serum obtained by venepuncture.

MAIN OUTCOME MEASURES

Percentage of participants with (rabbit complement) serum bactericidal antibody titres of at least 1:8; geometric mean titres of serogroup C meningococcal serum bactericidal antibody.

RESULTS

Five years after immunisation, 84.1% (95% confidence interval 81.6% to 86.3%) of 987 participants had a bactericidal antibody titre of at least 1:8. Geometric mean titres of bactericidal antibody were significantly lower in 11-13 year olds (147, 95% confidence interval 115 to 188) than in 14-16 year olds (300, 237 to 380) and 17-20 year olds (360, 252 to 515) (P<0.0001 for both comparisons). Within these age bands, no significant difference in geometric mean titres of bactericidal antibody between recipients of the different serogroup C meningococcal vaccines was seen. More than 70% of participants had received a vaccine from one manufacturer; in this cohort, geometric mean titres were higher in those immunised at aged 10 years or above than in those immunised before the age of 10.

CONCLUSIONS

Higher concentrations of bactericidal antibody are seen five years after immunisation with serogroup C meningococcal vaccine at age 10 years or above than in younger age groups, possibly owing to immunological maturation. This provides support for adolescent immunisation programmes to generate sustained protection against serogroup C meningococcal disease not only for the vaccine recipients but also, through the maintenance of herd immunity, for younger children.

Effects of Week of Lactation and Genetic Selection for Milk Yield on Milk Fatty Acid Composition in Holstein Cows

Control (CL) and select line (SL) dairy cows (n = 22) managed identically but differing in milk yield (>4100 kg/305 d) were used to determine differences in milk fatty acid profile as lactation progressed. Milk yield was recorded daily and milk samples were collected during wk 1, 4, 8, 12, and 16 postpartum for milk composition analysis. Milk samples from wk 1, 8, and 16 were also analyzed for fatty acid composition. Select-line cows produced more milk (44.4 vs. 31.2 kg/d) and milk components than CL cows during the 16-wk period. There was no difference in rate of milk yield increase, but peak milk yield for SL cows was greater and occurred later in lactation. There were no differences in milk SCC or milk fat, protein, or lactose content. Selection for milk yield did not affect the content of most individual milk fatty acids; however, compared with CL, SL cows had a reduced Delta(9)-desaturase system and tended to produce milk with lower monounsaturated fatty acid content. Selection for milk yield did not affect milk fatty acid origin but the percentage of de novo fatty acids increased and preformed fatty acids decreased as lactation progressed. Milk fat trans-11 18:1 and cis-9,trans-11 conjugated linoleic acid increased with progressing lactation (10.7 vs. 14.1 and 3.1 vs. 5.4 mg/g, or 31 and 76%, respectively) and were correlated strongly among wk 1, 8, and 16 of lactation. Temporal changes in the Delta(9)-desaturase system occurred during lactation but these changes were not correlated with milk fat cis-9,trans-11 conjugated linoleic acid content. Results indicate prolonged genetic selection for milk yield had little effect on milk fatty acid composition, but milk fatty acid profiles varied markedly by week of lactation.

Effect of Supplemental Conjugated Linoleic Acids on Heat-Stressed Brown Swiss and Holstein Cows

Heat-stressed dairy cattle are bioenergetically similar to early-lactation cows in that dietary energy may be inadequate to support maximum milk and milk component synthesis. Study objectives were to evaluate whether conjugated linoleic acids- (CLA-) induced milk fat depression (MFD) during heat stress would allow for increased milk and milk component synthesis. In addition, CLA effects on production variables and its ability to induce MFD were compared between Holstein and Brown Swiss cows. Multiparous cows (n = 8, Holstein; n = 5, Brown Swiss) averaging 97 +/- 17 d in milk were used in a crossover design during the summer (mean temperature-humidity index = 75.7). Treatment periods were 21 d with a 7-d adaptation period before and between periods. During adaptation periods, all cows received a supplement of palm fatty acid distillate (242 g/d). Dietary treatment consisted of 250 g/d of CLA supplement (78.9 g/d of CLA) or 242 g/d of palm fatty acid distillate to provide equal amounts of fatty acids. The CLA supplement contained a variety of CLA isomers (3.0% trans-8, cis-10; 3.4% cis-9, trans-11; 4.5% trans-10, cis-12; and 4.8% cis-11, trans-13 CLA). Treatments were applied 2 x/d with half of the supplement top-dressed at 0600 h and the remainder top-dressed at 1800 h. There was no overall treatment effect on dry matter intake (23.9 kg/d), milk yield (40.0 kg/d), somatic cell count (305,000), protein (2.86%), or lactose content (4.51%) or yields of these milk components. Supplementation with CLA decreased overall milk fat content and yield by 26 and 30%, irrespective of breed. The reduction of milk fat content and yield was greatest on d 21 (28 and 37%, respectively). Energy availability predicted by energy balance was improved with CLA supplementation compared with controls (3.7 vs. 7.1 Mcal/d, respectively). Respiration rate (78 breaths/min) and skin temperature (35.4 degrees C) during maximum heat load were not affected by treatment. The group receiving CLA had higher total milk fat CLA concentration (9.3 vs. 4.9 mg/g). Supplementation with CLA induced MFD and altered milk fat composition similarly between breeds and improved calculated energy balance during heat stress, but had no effect on production measures under these conditions.

Increasing Amounts of Conjugated Linoleic Acid (CLA) Progressively Reduces Milk Fat Synthesis Immediately Postpartum

Mixed conjugated linoleic acid (CLA) isomers decrease milk fat synthesis during established lactation, but their ability to cause milk fat depression (MFD) immediately postpartum remains unclear. Multiparous Holstein cows (n = 19) were randomly assigned to 1 of 4 doses of rumen-protected (RP) CLA supplements (0, 200, 400, and 600 g/d); each dose provided equal amounts of fatty acids by replacing and balancing treatments with an RP supplement of palm fatty acid distallate. Doses provided a total of 468 g fatty acids/d and 0, 62, 125, or 187 g of mixed CLA isomers/d, respectively. The CLA supplement contained a variety of CLA isomers: 5.4% trans-8, cis-10; 6.3% cis-9, trans-11; 7.9% trans-10, cis-12; and 8.2% cis-11, trans-13 CLA. Each group received treatments from approximately -10 to 21 d relative to calving. To improve palatability and ensure complete consumption, doses were mixed with equal amounts of steam-flaked corn and dried molasses; one-half the supplement was fed at 0600 h, and the remaining supplement was fed at 1800 h. Milk yield and individual feed intake were recorded daily, and milk samples were obtained from each cow every 2nd day (at both milkings) starting on d 1 postpartum. There were no differences in dry matter intake (17.1 kg/d), milk yield (34.2 kg/d), protein content (3.74%), lactose content (4.61%), or yield of milk protein or lactose. The CLA supplementation decreased overall milk fat content in a dose-responsive manner (4.57, 3.97, 3.32, and 3.10, respectively), and milk fat yield displayed the same progressive decline. The dose-dependent decrease in milk fat content was evident during wk 1 and became highly significant during wk 2 and 3. The milk fat yield response pattern was similar, and by d 21, the highest RP-CLA supplement decreased milk fat content and yield by 49 and 56%, respectively. These data clearly indicate RP-CLA can markedly (40 to 50%) induce MFD immediately postpartum without negatively affecting other production parameters.

Analysis of pilot-related equipment and archaeological strategy in the recovery of aircrew losses from the Vietnam War

Determining the location and distribution of cockpit and aircrew-related equipment within the wider debris field of a military aircraft crash site is an essential first step in planning and executing the recovery of missing aircrew members presumed still to be on the site. Understanding the spatial relationship of these materials improves the likelihood of finding and recovering the remains of the aircrew during the excavation of an aircraft crash site. Since the greater portion of these unaccounted for crewmembers were involved in aircraft with single-seat cockpits or cockpits with two or three seats in tandem, pre-analysis of the debris pattern may be more-or-less straightforward. Larger, multiple-personnel aircraft, on the other hand, create a potentially more complex analytical situation given the aircrew's greater freedom of movement within the aircraft. Nevertheless, the same fundamental principles apply and, indeed, have been successfully so for some time in the civilian arena. But older aircraft crash sites, i.e., those dating to World War II, Korea, or the Vietnam conflict, have been and still are undergoing taphonomic processes that progressively alter these relationships. The following will illustrate that exchange of information between the anthropologist/archaeologist and the life-support analyst is required to maximize the effectiveness of field recovery and demonstrates the relationship between the recovery of life-support equipment and human remains and the effect that aircraft type has on this relationship.

Comparison of multilocus sequence typing and pulsed-field gel electrophoresis as tools for typing Staphylococcus aureus isolates in a microepidemiological setting

Multilocus sequence typing (MLST) of Staphylococcus aureus is well suited to the study of global or long-term epidemiology, but its role in local epidemiology has not been defined. The present study has compared MLST with pulsed-field gel electrophoresis (PFGE) by using S. aureus isolates associated with carriage and disease in a busy regional renal unit. One hundred forty-four patients were prospectively recruited, of whom 103 were receiving hemodialysis and 41 were on continuous ambulatory peritoneal dialysis. Three nasal swab specimens were obtained 1 month apart on entering the study. A nasal swab was positive for S. aureus on at least one occasion in 50 patients (35%). Typing of the 104 carriage isolates demonstrated 21 PFGE types and 21 sequence types (STs). Thirty-one carriers had two or more positive nasal swabs; of these, the isolates in all swabs from a given carrier had identical PFGE types for 29 carriers; the isolates in all of the same 29 swabs had identical STs. The carriage strain in two patients changed both PFGE type and STs during the period of swabbing. Eight patients (6%) had an episode of S. aureus bacteremia during the 12-month study period, and two of these were nasal carriers. One of these invasive isolates had the same PFGE type and ST as the carriage isolate. There were no differences between Simpson's index of diversity for PFGE and Simpson's index of diversity for MLST for both invasive and carriage isolates, suggesting that the two methods have very similar discriminatory abilities. We conclude that PFGE and MLST performed equally in this study.

Human locognosic acuity on the arm varies with explicit and implicit manipulations of attention: implications for interpreting elevated tactile acuity on an amputation stump

In Experiment 1, normal subjects' ability to localize tactile stimuli (locognosia) delivered to the upper arm was significantly higher when they were instructed explicitly to direct their attention selectively to that segment than when they were instructed explicitly to distribute their attention across the whole arm. This elevation of acuity was eliminated when subjects' attentional resources were divided by superimposition of an effortful, secondary task during stimulation. In Experiment 2, in the absence of explicit attentional instruction, subjects' locognosic acuity on one of three arm segments was significantly higher when stimulation of that segment was 2.5 times more probable than that of stimulation of the other two segments. We surmise that the attentional mechanisms responsible for such modulations of locognosic acuity in normal subjects may contribute to the elevated sensory acuity observed on the stumps of amputees.

A link between virulence and ecological abundance in natural populations of Staphylococcus aureus

Staphylococcus aureus is a major cause of severe infection in humans and yet is carried without symptoms by a large proportion of the population. We used multilocus sequence typing to characterize isolates of S. aureus recovered from asymptomatic nasal carriage and from episodes of severe disease within a defined population. We identified a number of frequently carried genotypes that were disproportionately common as causes of disease, even taking into account their relative abundance among carriage isolates. The existence of these ecologically abundant hypervirulent clones suggests that factors promoting the ecological fitness of this important pathogen also increase its virulence.

Recombination within natural populations of pathogenic bacteria: short-term empirical estimates and long-term phylogenetic consequences

The identification of clones within bacterial populations is often taken as evidence for a low rate of recombination, but the validity of this inference is rarely examined. We have used statistical tests of congruence between gene trees to examine the extent and significance of recombination in six bacterial pathogens. For Neisseria meningitidis, Streptococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus, the congruence between the maximum likelihood trees reconstructed using seven house-keeping genes was in most cases no better than that between each tree and trees of random topology. The lack of congruence between gene trees in these four species, which include both naturally transformable and nontransformable species, is in three cases supported by high ratios of recombination to point mutation during clonal diversification (estimates of this parameter were not possible for Strep. pyogenes). In contrast, gene trees constructed for Hemophilus influenzae and pathogenic isolates of Escherichia coli showed a higher degree of congruence, suggesting lower rates of recombination. The impact of recombination therefore varies between bacterial species but in many species is sufficient to obliterate the phylogenetic signal in gene trees.

Investigation of the functional correlates of reorganization within the human somatosensory cortex

Much work in animals and humans has demonstrated the existence of changes in topographic organization within the somatosensory cortex (SSC) after amputation or nerve injury. Afferent inputs from one area of skin are able to activate novel areas of cortex after amputation of an adjacent body part. We have investigated the functional consequences of this reorganization in a group of patients with nerve injury. Using the microneurographic technique of intraneural microstimulation (INMS) we stimulated groups of nerve fibres, within individual fascicles proximal to the nerve transection, with small electrical pulses. This enabled us to activate the deafferented cortex that had presumably undergone remodelling and study the conscious percepts described by the subjects. In 39 fascicles from 10 subjects, we found that the sensations evoked on INMS were no different from those reported previously by subjects with intact nerves. This finding suggests that such reorganization within the SSC has little effect on the function of deafferented cortical neurones or subcortical relay stations. In a separate set of experiments, INMS was performed in 16 nerve fascicles from an adjacent non-injured nerve or uninjured fascicle within a partially injured nerve. The sensations evoked by INMS in these experiments were also comparable to those obtained in normal subjects. This indicates that the expanded cortical representation of adjacent non-anaesthetic skin does not influence the cortical processing of afferent information. Taken together, these findings lead us to question the notion that reorganization of connections within the somatosensory cortex equates to a change in function. Whilst it may be advantageous that the human brain is not 'hard-wired', neurophysiological proof of functional plasticity in the adult somatosensory system as a result of deafferentation is elusive.

Cortical focusing is an alternative explanation for improved sensory acuity on an amputation stump

The ability to localize a sensory stimulus on the body surface (locognosia) has been investigated in normal subjects in a quest to find an explanation for the reported findings of improved sensory acuity on an amputation stump. We have shown that when attending to a smaller area of skin, during the testing procedure, locognosia improves (P < 0.001) by a similar degree to that seen in amputees. Such selective attention is likely to occur in upper limb amputees as they have a reduced area of skin on which to focus during sensory testing. This represents a further explanation for improved sensory acuity on an amputation stump without implicating plasticity of connections within the somatosensory cortex.

Critical pathways in anterior cranial base surgery

New advances in anterior cranial base surgery have dictated the need for a comprehensive, multidisciplinary approach in the treatment of lesions of this area, necessitating multiple modes of diagnostic and surgical techniques. Traditional consideration of the complex problems presented by neoplastic involvement of the anterior cranial base predicated on isolated syndrome analysis is no longer sufficient to adequately assess tumor pathology. To address these complex problems, we discuss a method of localization of pathology based on anatomic structure and function as well as the corresponding surgical approach to the anterior cranial base.

High-risk human papillomavirus types and squamous cell carcinoma in patients with respiratory papillomas

Respiratory papillomas (RPs) are benign, virally induced tumors of the larynx and respiratory epithelium that may obstruct the airway and tend to recur frequently. RPs are thought to be the result of infection with the human papillomaviruses (HPVs) types 6 and 11. We surveyed archival RP specimens to determine whether there were correlations of HPV type with patient characteristics or clinical course. Paraffin-embedded papilloma specimens of 45 different patients were analyzed. We assessed HPV types using the polymerase chain reaction with E6 consensus primers, hybrid capture assays (high or low risk), and dot blot hybridization of generic E6 PCR products with E6 type-specific oligonucleotide probes. The presence and type of HPV were correlated with patient data from a retrospective chart review. We found that RPs may have either low- or high-risk HPV types and some contain multiple HPV types. Respiratory infection with high-risk HPV apparently introduces a long-term risk of squamous cell carcinoma development, even in the absence of conventional cofactors. Low-risk HPV infection may also act in association with these cofactors to promote carcinogenesis. Our data also show a racial imbalance in RP that may indicate a difference in genetic resistance and/or susceptibility to HPV infection and the development of RP.

Subcranial approach to tumors of the anterior cranial base: analysis of current and traditional surgical techniques

Tumors of the anterior cranial base have previously required a craniofacial resection to allow adequate tumor extirpation. An analysis of current and traditional techniques demonstrates a significant reduction in operative time, complication rate, and intensive care unit and total hospital length of stay with the use of the subcranial approach as compared with the traditional frontal craniotomy and lateral rhinotomy approach. The subcranial approach is both cost and time efficient and provides comparable morbidity and mortality rates.

Orthodromic near-field potentials of the intratemporal facial nerve

HYPOTHESIS

This study aimed to assess the electrophysiologic parameters of near-field action potentials recorded from the intratemporal facial nerve.

BACKGROUND

Assessment of facial nerve function is limited because of the inaccessibility of the majority of its course deep in the temporal bone. Indirect measurements have therefore evolved in which stimulation distal to most major pathology and indirect recordings from the tissues the nerve supplies offers some evidence as to facial function. Recording from the intratemporal portion of the facial nerve is possible. Antidromic nerve action potentials can be recorded from an extratympanic electrode after stimulation of peripheral facial nerve branches. This technique offers new alternatives to the assessment of the facial nerve.

METHODS

The facial nerve was electrically stimulated close to the brain stem, and monopolar recordings were taken distally at several points along its intratemporal course. Averaging techniques produced a reliable and reproducible triphasic waveform that then was analyzed.

RESULTS

Neuromuscular blockade had no effect on amplitude of the waveform. Recording at different points along the nerve course showed an increasing nerve potential latency with increasing distance from the stimulus. The amplitude of the waveform decreased as the recording electrode was moved away from the nerve. These findings are in keeping with the electrophysiologic properties of a near-field nerve action potential. Conduction velocity along the facial nerve averaged 23.7 m/s and was found to vary along different nerve segments.

CONCLUSION

Facial nerve action potentials can be recorded from within the temporal bone despite its multidirectional course through different volume conductors. These action potentials exhibit the same characteristics as those arising from more accessible peripheral nerves.

Red bluebirds and black greenflies: preschoolers' understanding of the semantics of adjectives and count nouns

Three experiments explored preschoolers' and adults' understanding of the distinctive semantic functions of adjectives (i.e., to name properties) and count nouns (i.e., to name object kinds). In Experiment 1, we modeled a familiar adjective (e.g., "blue") syntactically as either an adjective (e.g., "This is a blue one") or a count noun (e.g., "This is a blue") and applied it to a target object (e.g., a blue creature). In Experiments 2 and 3, we marked the adjective phonologically as either an adjective (e.g., "This is a blue bird") or a part of a count noun (e.g., "This is a bluebird") and applied it to a target object (e.g., a blue bluebird). In all experiments, participants then had to extend the expression they heard to either an object of a different kind with the same property as the target (e.g., a different creature or bird colored blue) or an object of the same kind with a different property (e.g., the same creature or bird colored red). Four-year-olds and adults, but not 3-year-olds, who heard the adjective version were more likely than those who heard the count noun version to choose the object with the same property. Thus, by the age of four years, children treated a word's lexical category, cued syntactically or phonologically, as a powerful cue to its meaning.

Cutaneous localisation of laser induced pain in humans

Localisation of painful laser-induced stimuli has been compared to localisation of tactile stimuli in normal humans. Laser stimulation evoked pain of two qualities (sharp pricking pain and hot burning pain). Sharp pricking pain was found to be localised with almost equal precision to tactile stimuli (13.8 +/- 3.4 versus 11.6 +/- 2.3 mm) on the dorsum of the hand, (21.5 +/- 7.9 versus 20.6 +/- 7.5 mm) on the forearm and (15.5 +/- 5.6 versus 13.8 +/- 5.4 mm) on the foot, respectively. There was no significant difference between the ability to localise tactile stimuli and hot burning pain except on the dorsum of the hand. These results indicate that tactile information is not essential for the accurate localisation of cutaneous pain.