Effects of dexmedetomidine on kidney and brain tissue microcirculation and histology in ovine cardiopulmonary bypass: a randomised controlled trial.

Cardiac surgery requiring cardiopulmonary bypass is associated with postoperative acute kidney injury and neurocognitive disorders, including delirium. Intra-operative inflammation and/or impaired tissue perfusion/oxygenation are thought to be contributors to these outcomes. It has been hypothesised that these problems may be ameliorated by the highly selective α2 -agonist, dexmedetomidine. We tested the effects of dexmedetomidine on renal and cerebral microcirculatory tissue perfusion, oxygenation and histology in a clinically relevant ovine model. Sixteen sheep were studied while conscious, after induction of anaesthesia and during 2 h of cardiopulmonary bypass. Eight sheep were allocated randomly to receive an intravenous infusion of dexmedetomidine (0.4-0.8 µg.kg-1 .h-1 ) from induction of anaesthesia to the end of cardiopulmonary bypass, and eight to receive an equivalent volume of matched placebo (0.9% sodium chloride). Commencement of cardiopulmonary bypass decreased renal medullary tissue oxygenation in the placebo group (mean (95%CI) 5.96 (4.24-7.23) to 1.56 (0.84-2.09) kPa, p = 0.001), with similar hypoxic levels observed in the dexmedetomidine group (6.33 (5.33-7.07) to 1.51 (0.33-2.39) kPa, p = 0.002). While no differences in kidney function (i.e. reduced creatinine clearance) were evident, a greater incidence of histological renal tubular injury was observed in sheep receiving dexmedetomidine (7/8 sheep) compared with placebo (2/8 sheep), p = 0.041. Graded on a semi-quantitative scale (0-3), median (IQR [range]) severity of histological renal tubular injury was higher in the dexmedetomidine group compared with placebo (1.5 (1-2 [0-3]) vs. 0 (0-0.3 [0-1]) respectively, p = 0.013). There was no difference in cerebral tissue microglial activation (neuroinflammation) between the groups. Dexmedetomidine did not reduce renal medullary hypoxia or cerebral neuroinflammation in sheep undergoing cardiopulmonary bypass.

'You're not going to give a monkey's chuff': exploring co-production in the design of services for women who have experienced sexual violence.

AIMS: Co-production is an emerging field in public health practice. We aim to present evidence of what works well to support co-production and what can be improved based upon learning from our evaluation of a co-production project implemented by Rape Crisis England and Wales (RCEW). RCEW designed and delivered a national co-production project called Weaving the Web, to inform the development of an online support service for women who have experienced sexual violence. METHODS: We qualitatively evaluated the RCEW co-production approach. The specific objectives of our evaluation were to assess the increased role and voice for women and girls in co-producing services and provide better quality of evidence for what works in empowering women and girls. The evaluation was conducted in two phases: Phase 1 was the observation of co-production events (n = 8), with findings from this used to develop an interview schedule for Phase 2, where semi-structured interviews (n = 26) were conducted with a range of stakeholders (staff, partners and service users). RESULTS: Staff supporting the co-production project were highly committed to the work, investing time, money, and preparation, and having a good understanding of co-production. Service users were less familiar with the approach and felt alienated by some of the language used. Most service users described participation as empowering and, in some instances, important in their own recovery. They were keen to stay involved beyond the creation of the online resource. CONCLUSION: The data from our evaluation illustrate that co-production on a national level is challenging. While RCEW used values-based practice, and provided a supportive culture to underpin the co-production of their online service, transformative engagement and true participation were not achieved. Learning from this project is drawn out here to outline transferrable lessons for practitioners intending to use models of co-production in other public health settings.

Stress, a reflective self and an internal locus of control: On the everyday clinical placement experiences of older undergraduate radiographers in the UK.

INTRODUCTION: Extant evidence indicates that the stresses experienced by younger undergraduate radiographers and their older counterparts vary considerably. Much of this difference has, however, emerged from analyses of the academic component of a radiography degree whereas little work has focused to date upon the specific business of clinical placement. Given this, the research herein reports findings from a qualitative study of how older undergraduate radiography students in the UK assemble their stress and stressors around clinical placement. METHODS: An Interpretative Phenomenological Analysis was employed. N = 6 older undergraduate students undergoing their final year placement were purposively recruited from a variety of hospitals. With full institutional ethical approval, a semi-structured interview was conducted with each participant. RESULTS: Four superordinate themes emerged. These were: (1) Self-identity and perceived competence; (2) Understaffing, instability and affect; (3) Episodic experience and feeling 'thrown-in'; (4) Unpreparedness for the challenging patient. Critically, each theme describes an interaction between stressor, experience of stress and self. CONCLUSION: While familiar stressors were apparent, the older participating students actively made sense of them in terms of their manageability. This provides a strong contrast with existing literature, which tends to imply a more externalised locus of control among (largely younger) students. IMPLICATIONS FOR PRACTICE: Stress in the NHS is a continuing issue and there is a clear rationale for further investigation to ascertain the level of clinical support available and to determine whether further improvements could assist students on clinical placement. Collaboration between academic institutions and clinical sites would allow open discussion around clinical stress experienced by radiography students, with locus of control a potential point of focus, fostering a proactive partnership approach to stress-management and identification of difficulties before they exacerbate.

Evaluation of a urology specialist therapeutic radiographer implemented radiotherapy pathway for prostate cancer patients.

INTRODUCTION: The role of the Urology Specialist Therapeutic Radiographer (USTR) was introduced to support a busy NHS uro-oncology practice. Key objectives were to improve patient preparedness for and experience of radiotherapy, focussed on prostate cancer. Pre-radiotherapy information seminars were developed, and on-treatment patient review managed by the USTRs. To evaluate the revamped patient pathway and direct further improvements, a patient experience survey was designed. METHODS: An 18-point patient questionnaire was produced. The questionnaire captured patient experience and preparedness; pre, during and at completion of treatment. The patient population comprised men receiving radiotherapy for primary prostate cancer within one UK Trust. RESULTS: Two-hundred and fifty-one responses were received. Seventy-three percent of patients felt completely prepared for radiotherapy, higher in those who attended a seminar (77%) compared to those who did not (61%). Eighty-nine and eighty-six percent of respondents were completely satisfied with verbal and written information received prior to commencing radiotherapy respectively. Seventy-three percent of responders would have found additional resources helpful. With respect to on-treatment clinics; eighty-five percent were seen on time or within 20 minutes, eighty-three percent felt fully involved in decisions regarding their care and ninety-one percent reported complete satisfaction with the knowledge of the health care professional reviewing them. The follow-up process was completely understood by eighty-eight percent and overall patient experience rated excellent by eighty-five percent of responders. CONCLUSION: The revamped pathway implemented by USTRs has achieved high levels of satisfaction at all stages of the prostate patient's radiotherapy. By diversifying the format of information giving, the USTRs hope to further meet the information needs of patients. IMPLICATIONS FOR PRACTICE: Validation of a prostate cancer radiotherapy pathway which employs USTRs and utilises a patient preparation seminar. This model could support the introduction of Specialist Therapeutic Radiographers in other Trusts and treatment sites.

Managing discomfort and developing participation in non-emergency MRI: Children's coping strategies during their first procedure.

INTRODUCTION: Building on existing work, this paper aims to develop a detailed analysis of the practical coping strategies developed by children who had not previously experienced an MRI, regarding a non-emergency examination of the brain. METHODS: Semi-structured interviews with 22 children, aged between eight and sixteen years, were conducted immediately post-procedure. Emergent data were thematically analysed in line with the core precepts of Grounded Theory, and triangulated against interview data with their parents where pertinent. RESULTS: The primary concern among interviewees related to how they had coped with the discomfort of an unfamiliar medical procedure; this was recurrently managed through a process herein termed Participation Development. This comprised three phases. The first, preparative participation, describes the children's reported attempts to ready themselves for the examination (with parents) ahead of arriving in hospital. The second, enabling participation, describes how the children (with input from parents and radiographers) endeavoured to understand what was to come, and select viable distraction techniques. Finally, sustaining participation describes the children's reports of actualizing their preparations during the examination itself. Where the overall process of participation development was successful, the children reported a sense of mastery, growth and even joy. CONCLUSION: While much work in the domain portrays children as relatively 'passive' agents during an MRI procedure, the findings herein point to how they can (with varying degrees of success) actively and constructively work with others. This, it is contended, has direct import for the improvement of support, both prior to and within a procedure itself.

Recovery of brodifacoum in vomitus following induction of emesis in dogs that had ingested rodenticide bait.

AIM: To assess the benefit of inducing emesis in dogs that have ingested rodenticide bait containing brodifacoum (BDF), by determining the amount of BDF in bait recovered from the vomitus relative to the estimated amount consumed. METHODS: Between 2014 and 2015 samples of vomitus from seven dogs that ingested rodenticide baits containing BDF were submitted by veterinarians in New Zealand. All seven dogs had been given apomorphine by the veterinarian and vomited within 1 hour of ingesting the bait. Some or all of the bait particles were retrieved from each sample and were analysed for concentrations of BDF using HPLC. Based on estimations of the mass of bait consumed, the concentration of BDF stated on the product label, and the estimated mass of bait in the vomitus of each dog, the amount of BDF in the vomited bait was calculated as a percentage of the amount ingested. RESULTS: For five dogs an estimation of the mass of bait ingested was provided by the submitting veterinarian. For these dogs the estimated percentage of BDF in the bait retrieved from the vomitus was between 10-77%. All dogs were well after discharge but only one dog returned for further testing. This dog had a normal prothrombin time 3 days after ingestion. CONCLUSIONS AND CLINICAL RELEVANCE: The induction of emesis within 1 hour of ingestion can be a useful tool in reducing the exposure of dogs to a toxic dose of BDF. The BDF was not fully absorbed within 1 hour of ingestion suggesting that the early induction of emesis can remove bait containing BDF before it can be fully absorbed.

Student radiographers' attitudes towards the older patient - A longitudinal study.

INTRODUCTION: To design, implement and evaluate the effect of an educational intervention on student radiographer attitudes across their educational tenure. METHODS: In the first phase, an educational intervention that involved didactic lectures, reflective exercises and simulation suits, aimed at improving student radiographer attitudes towards the older person, was designed and implemented. Kogan's attitudes towards older people (KoP) scale was administrated at five test points; pre-intervention; post-intervention; 6 months post intervention; 12 months post intervention and 24 months post intervention. At the final test point these quantitative data was supplemented with qualitative data for triangulation of the findings. RESULTS: Students held positive attitudes towards older people pre intervention, these increased significantly post intervention (p = 0.01). However, this increase in positive scores was not noted at 6 months and 12-months post intervention. At 24-months post intervention, although there was a slight increase in positive attitudes when compared to the 6 and 12 month scores, this increase was not found to be significant (p = 0.178) CONCLUSION: The results post-intervention suggested that an educational intervention can have a significant impact on student radiographer's attitudes towards older people. However, the qualitative data suggests that experiences on initial clinical placement can be detrimental to attitudinal scores, particularly if the intervention does not include Dementia care strategies.

Leadership and the everyday practice of Consultant Radiographers in the UK: Transformational ideals and the generation of self-efficacy.

INTRODUCTION: This paper outlines findings from a broader, two-year project investigating the role of Consultant Radiographers (CRs) in the UK, focussing specifically on the leadership aspect of that role. METHODS: Using a qualitative-thematic approach, the leadership-related experiences of a purposive sample of six participating CRs are explored, alongside the systems through which they evaluated how successful they had been as leaders. RESULTS: It is evidenced that many of the ways in which participants describe their own leadership practice, particularly in the intra-team domain, is consistent with the precepts of the Transformational Leadership Model. For example, they highlight how they have asserted positive influence and encouraged collective action and decision-making. However, the experiential focus of the analysis reveals that in specific examples of practice, the transformational approach was not always seen as the most useful route to a productive outcome given constrictions on time and other resources within real professional environments. More 'direct' managerial approaches were sometimes deemed necessary, and at others leadership was reduced to simply 'solving other people's problems'. It was also found that the manner in which participants evaluated their own success as leaders was a practical concern, based in part upon having satisfied 'hard' institutional goals, but also on the more personal business of having affirmatively 'surprised' oneself, or a general sense of feeling trusted by colleagues. CONCLUSION: These findings may help support CRs in the business of real leadership, not least through better understanding how even apparently mundane outcomes can have significant impacts on professional self-efficacy.

Obesity, heuristic reasoning and the organisation of communicative embarrassment in diagnostic radiography.

This paper, the second of three arising from a broader qualitative study, explores difficulties emerging around radiographer-patient communication regarding obesity in hospital-based encounters, and the situated strategies found by experienced radiographers for handling such situations. Semi-structured interviews with eight clinicians working in plain radiography (mean experience = 21.56 years) were analysed using Interpretative Phenomenological Analysis (IPA), so as to highlight the practical, nuanced and real-world experiences of these individuals regarding obesity communication. Participants generally viewed communicating with obese patients as a potential interpersonal 'minefield'. Most reported having had negative experiences in which patients had acted with denial or outright aggression during examinations but, conversely, all reported cases in which patients had been frank and open about their obesity, and even been happy to joke about it. Equally, all participants were able to document a range of communicative strategies for effectively handling potentially difficult situations. Results further indicate that the documented communicative problems and embarrassment for the patient only generally arose within specific material contexts; i.e. when equipment is inadequate or multiple exposures are necessary. It is concluded that, while participants largely expected any interaction about obesity with a patient to be embarrassing for both parties, their actual experience was much more varied. This indicates a more complex communicative environment than may be expected, and also a potential metacognitive availability heuristic in play - something that might be clarified with future quantitative investigation.

Distribution of orexin-1 receptor-green fluorescent protein- (OX1-GFP) expressing neurons in the mouse brain stem and pons: Co-localization with tyrosine hydroxylase and neuronal nitric oxide synthase.

We used a reporter mouse line in which green fluorescent protein (GFP) was inserted into the orexin-1 receptor (OX1) locus to systematically map the neuroanatomical distribution of the OX1 receptor in the mouse brainstem and pons. Here, we show that the OX1 receptor is expressed in a select subset of medullary and pontine nuclei. In the medulla, we observed OX1-GFP expression in the cuneate, gracile, dorsal motor nucleus of the vagus (10N), nucleus of the solitary tract and medullary raphe areas. In the pons, the greatest expression was found in the locus coeruleus (LC) and dorsal raphe nucleus (DRN). High to moderate expression was found in the pedunculopontine tegmental nucleus (PPTg), laterodorsal tegmental nucleus, A5 noradrenergic cell group (A5) and the periaqueductal gray. Double-labeling with neuronal nitric oxide synthase (NOS1) revealed extensive co-localization in cell bodies and fibers of the 10N, A5 cell group and the PPTg. Double-staining with tyrosine hydroxylase revealed extensive co-expression in the LC, DRN and the lateral paragigantocellularis cell group in the ventral medulla. Our findings faithfully recapitulate the findings of OX1 mRNA expression previously reported. This is the first study to systematically map the neuroanatomical distribution of OX1 receptors within the mouse hindbrain and suggest that this OX1-GFP transgenic reporter mouse line might be a useful tool with which to study the neuroanatomy and physiology of OX1 receptor-expressing cells.

Timeliness of electronic reporting and acceptability of public health follow-up of routine nonparatyphoidal and nontyphoidal Salmonella infections, London and South East England, 2010 to 2011.

Nonparatyphoidal and nontyphoidal Salmonella (NTS) infections are major causes of food poisoning in England. Diagnostic laboratories and clinicians have a statutory responsibility to report NTS infection cases to the Health Protection Agency via various means, with electronic reporting encouraged as the universal method. The Health Protection Agency (Public Health England since 1 April 2013) refers cases to environmental health departments for follow-up. Timeliness of reporting and adequacy of NTS infection case follow-up are key factors in the implementation of public health actions. Laboratories, health protection units, and environmental health departments in London and South East (SE) regions of England completed three surveys between December 2010 and April 2011, collecting data about the NTS infection case reporting methods and the time elapsed between symptom onset and public health actions. The median period between symptom onset and public health investigation was 25 days in London and 23 days in SE when electronic reporting was used and 12 days in London and 11 days in SE when other means of reporting were used. The most common follow-up method was a telephone questionnaire in London (53%) and a postal questionnaire in SE (52%). The telephone questionnaire had the highest response rate (98% in London; 96% in SE). Timeliness and efficiency of electronic NTS infection case reports can be improved by decreasing the electronic laboratory report period and using telephone-administered questionnaires to maximize the public health benefit when following up single cases of NTS infection.

Duration of shedding of Verocytotoxin-producing Escherichia coli in children and risk of transmission in childcare facilities in England.

Exclusion of children with presumptive Verocytotoxin-producing Escherichia coli (VTEC) from childcare facilities until negative stool specimens are obtained is routine practice that disrupts families. We estimated the shedding and exclusion duration and transmission risk in such facilities. The study population comprised 225 children aged <6 years attending 201 childcare facilities in England with microbiologically confirmed VTEC in 2010-2011. We estimated the interval from onset to first negative specimen, and identified transmission events with secondary cases linked to facilities. The median duration of shedding was 31 days, and median period of exclusion was 39·5 days. Cases attending facilities while shedding VTEC did so for a median of 2 days before exclusion. Secondary cases occurred in 6/83 facilities (7%) attended by infectious cases. Despite evidence of VTEC shedding at facilities, transmission is relatively low. Revised control guidelines could consider supervised return for prolonged asymptomatic shedders.

Guidelines for the public health management of typhoid and paratyphoid in England: practice guidelines from the National Typhoid and Paratyphoid Reference Group.

OBJECTIVES: The Typhoid and Paratyphoid Reference Group (TPRG) was convened by the Health Protection Agency (HPA) and the Chartered Institute of Environmental Health (CIEH) to revise guidelines for public health management of enteric fever. This paper presents the new guidelines for England and their rationale. METHODS: Methods include literature reviews including grey literature such as audit data and case studies; analysis of enhanced surveillance data from England, Wales and Northern Ireland; review of clearance and screening schedules in use in other non-endemic areas; and expert consensus. RESULTS: The evidence and principles underpinning the new guidance are summarised. Significant changes from previous guidance include: • Algorithms to guide risk assessment and management, based on risk group and travel history; • Outline of investigation of non-travel cases; • Simplified microbiological clearance schedules for cases and contacts; • Targeted co-traveller screening and a "warn and inform" approach for contacts; • Management of convalescent and chronic carriers. CONCLUSIONS: The guidelines were launched in February 2012. Feedback has been positive: the guidelines are reported to be clear, systematic, practical and risk-based. An evaluation of the guidelines is outlined and will add to the evidence base. There is potential for simplification and consistency between international guidelines.

Large outbreak of Salmonella enteritidis PT8 in Portsmouth, UK, associated with a restaurant.

Seventy-five individuals with Salmonella infection were identified in the Portsmouth area during August and September 2009, predominantly Salmonella Enteritidis phage type 8. Five patients were admitted to hospital. A case-case comparison study showed that a local restaurant was the most likely source of the infection with a risk of illness among its customers 25-fold higher than that of those who did not attend the restaurant. A case-control study conducted to investigate specific risk factors for infection at the restaurant showed that eating salad was associated with a threefold increase in probability of illness. Changing from using ready washed lettuces to lettuces requiring washing and not adhering strictly to the 48 hours exclusion policy for food handlers with diarrhoea were likely to have contributed to the initiation and propagation of this outbreak. Possibilities for cross-contamination and environmental contamination were identified in the restaurant.

Effects of action relations on the configural coding between objects.

Configural coding is known to take place between the parts of individual objects but has never been shown between separate objects. We provide novel evidence here for configural coding between separate objects through a study of the effects of action relations between objects on extinction. Patients showing visual extinction were presented with pairs of objects that were or were not co-located for action. We first confirmed the reduced extinction effect for objects co-located for action. Consistent with prior results showing that inversion disrupts configural coding, we found that inversion disrupted the benefit for action-related object pairs. This occurred both for objects with a standard canonical orientation (e.g., teapot and teacup) and those without, but where grasping and using the objects was made more difficult by inversion (e.g., spanner and nut). The data suggest that part of the affordance effect may reflect a visuo-motor response to the configural relations between stimuli. Experiment 2 showed that distorting the relative sizes of the objects also reduced the advantage for action-related pairs. We conclude that action-related pairs are processed as configurations.

Receptor localization, native tissue binding and ex vivo occupancy for centrally penetrant P2X7 antagonists in the rat.

BACKGROUND AND PURPOSE: The P2X7 receptor is implicated in inflammation and pain and is therefore a potential target for therapeutic intervention. Here, the development of a native tissue radioligand binding, localization and ex vivo occupancy assay for centrally penetrant P2X7 receptor antagonists is described. EXPERIMENTAL APPROACH: Autoradiography studies using the P2X7 antagonist radioligand [³H]-A-804598 were carried out in rat brain and spinal cord. Subsequent in vitro binding and ex vivo occupancy assays were performed using rat cortex homogenate. KEY RESULTS: P2X7 expression was shown to be widespread throughout the rat brain, and in the grey matter of the spinal cord. In binding assays in rat cortex homogenate, ∼60% specific binding was achieved at equilibrium. In kinetic binding assays, k(on) and k(off) values of 0.0021·min⁻¹·nM⁻¹ and 0.0070·min⁻¹ were determined, and the K(d) derived from kinetic measurements was consistent with that derived from saturation analysis. Novel P2X7 antagonists inhibited the binding of [³H]-A-804598 to rat cortex P2X7 receptors with K(i) values of <40 nM. In an ex vivo occupancy assay, a P2X7 antagonist dosed orally to rats caused a concentration-dependent inhibition of the specific binding of [³H]-A-804598 to rat cortex. CONCLUSIONS AND IMPLICATIONS: The present study describes the development of an assay that allows localization of P2X7 receptors, the measurement of the binding affinity of P2X7 receptor antagonists in native tissue, and provides a means of determining central P2X7 receptor occupancy. These assays could form an important part of a P2X7 drug discovery programme.

Potential biomarkers for hypoxic-ischemic encephalopathy.

Cerebral hypothermia reduces brain injury and improves behavioral recovery after hypoxia-ischemia (HI) at birth. However, using current enrolment criteria many infants are not helped, and conversely, a significant proportion of control infants survive without disability. In order to further improve treatment we need better biomarkers of injury. A 'true' biomarker for the phase of evolving, 'treatable' injury would allow us to identify not only whether infants are at risk of damage, but also whether they are still able to benefit from intervention. Even a less specific measure that allowed either more precise early identification of infants at risk of adverse neurodevelopmental outcome would reduce the variance of outcome of trials, improving trial power while reducing the number of infants unnecessarily treated. Finally, valid short-term surrogates for long term outcome after treatment would allow more rapid completion of preliminary evaluation and thus allow new strategies to be tested more rapidly. Experimental studies have demonstrated that there is a relatively limited 'window of opportunity' for effective treatment (up to about 6-8h after HI, the 'latent phase'), before secondary cell death begins. We critically evaluate the utility of proposed biochemical, electronic monitoring, and imaging biomarkers against this framework. This review highlights the two central limitations of most presently available biomarkers: that they are most precise for infants with severe injury who are already easily identified, and that their correlation is strongest at times well after the latent phase, when injury is no longer 'treatable'. This is an important area for further research.

Experimental Study of a TET System for Implantable Biomedical Devices.

Time-varying magnetic fields can be used to transfer power across the skin to drive implantable biomedical devices without the use of percutaneous wires. However, the main challenges of a transcutanoues energy transfer (TET) system are the temperature rise caused by power loss in the implanted circuitry and the changes in positioning between the external and internal coils due to fitting and changes in posture. This study presents a TET system with a closed-loop frequency-based power regulation method to deliver the right amount of power to the load under variable coil coupling conditions. After implanting a TET system into adult sheep, the temperature rise in the internal and external coils of a TET system was measured for power delivery in the range of 5 W to 15 W. The sheep was housed in a temperature controlled (16 plusmn1degC, humidity 50plusmn10%) room, in accordance with the standard protocols implemented at the University of Auckland for sheep studies. A power-loss analysis for the overall system was performed. The system was capable of regulating power for axially aligned separations of up to 16 mm. The maximum power efficiency of the overall system was 82.1% and a maximum temperature rise of 2.7degC was observed on the implanted secondary coil.

Measuring degradation of zinc phosphide residues in possum stomach contents.

Zinc phosphide (ZnP) has been identified as a potentially cost-effective vertebrate pesticide for possum (Trichosurus vulpecula) control in New Zealand. We established methodology for analysis of microencapsulated ZnP formulations (MZP) and investigated the half-life of residual ZnP in the stomach contents of poisoned possums. An interlaboratory study was conducted to compare results of ZnP analysis in stomach contents. The half-life of ZnP was 3.4 days for ZnP in possum stomach contents and 6.7 days in vomit. Subsequent estimates were made of 34 and 67 days, respectively, for residual ZnP to decline to concentrations below the 1 microg/g method detection limit.