Limit case analysis of the "stable indenter velocity" method for obtaining creep stress exponents from constant load indentation creep tests

This study concerns a commonly-used procedure for evaluating the steady state creep stress exponent, n , from indentation data. The procedure involves monitoring the indenter displacement history under constant load and making the assumption that, once its velocity has stabilised, the system is in a quasi-steady state, with stage II creep dominating the behaviour. The stress and strain fields under the indenter are represented by "equivalent stress" and "equivalent strain rate" values. The estimate of n is then obtained as the gradient of a plot of the logarithm of the equivalent strain rate against the logarithm of the equivalent stress. Concerns have, however, been expressed about the reliability of this procedure, and indeed it has already been shown to be fundamentally flawed. In the present paper, it is demonstrated, using a very simple analysis, that, for a genuinely stable velocity, the procedure always leads to the same, constant value for n (either 1.0 or 0.5, depending on whether the tip shape is spherical or self-similar). This occurs irrespective of the value of the measured velocity, or indeed of any creep characteristic of the material. It is now clear that previously-measured values of n , obtained using this procedure, have varied in a more or less random fashion, depending on the functional form chosen to represent the displacement-time history and the experimental variables (tip shape and size, penetration depth, etc.), with little or no sensitivity to the true value of n .

Lessons that Linger: A 40-Year Follow-Along Note About a Boy with Autism Taught to Communicate by Gestures when Aged Six

We draw on an article published in 1973 in this journal. We described how we taught "Geoff," a 6-year old boy with autism, an elementary form of sign language during the course of 24 one-hour sessions held over a 12-week period (Webster et al. in J Autism Child Schizophr 3:337-346, 1973; Fruchter in Autism: new directions in research and education, pp 184-186, 1980). Here, we describe how it is that Geoff has maintained the vestiges of what we taught him (and indeed what he taught us) over the long span. This basic communication strategy has endured well and continues to contribute to his enjoyment of life.

A mass shooting at Port Arthur, Tasmania, Australia: a study of its impact on early pregnancy losses using a conception time-based methodology

STUDY QUESTION

Does an acute calamity in a community cause early miscarriage and is this association the same for male and female fetuses?

SUMMARY ANSWER

Estimated losses of 29.5% of first trimester pregnancies in the affected region could be associated with an acute calamity, with no statistically significant difference in estimated losses by fetal sex.

WHAT IS KNOWN ALREADY

There are very few studies on the impact of a calamity on early pregnancy loss and its differential effects on male and female fetuses. A decline in the human sex ratio at birth associated with the events of 9/11 in New York has been documented.

STUDY DESIGN, SIZE, DURATION

This is a retrospective descriptive study of birth register data in Tasmania, Australia, from 1991 to 1997, covering the period in which the calamity occurred. The register contains data on all pregnancies that proceeded to >20 weeks gestation. The conception date was calculated by subtracting gestational age from birth date. We estimated that 40 318 pregnancies were conceived in the period 1991-1996 inclusive. These were aggregated to 4-weekly blocks classified by region and sex.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The acute calamity was at Port Arthur, Tasmania, Australia. On 28 April 1996, a gunman opened fire on visitors and staff in a tourist cafe. A very stressful 20 h period, ended with 35 people dead and 22 injured. A negative binomial regression model was used to assess the association between this calamity and pregnancy loss. This loss is evidenced by a shortfall in the registration of pregnancies that were in their first trimester at the time of the calamity.

MAIN RESULTS AND THE ROLE OF CHANCE

We estimated a shortfall of 29.5% or 229 registered pregnancies among those in the first trimester at the time of the calamity (P < 0.001), in the region surrounding the calamity site. There was no sex effect in this shortfall (P = 0.911). There was no corresponding shortfall in other parts of Tasmania (P = 0.349).

LIMITATIONS, REASONS FOR CAUTION

The study is descriptive and cannot produce causal inferences. These first trimester miscarriages are estimated statistically and it is understood that gestational age is an estimate. The use of maternal residential postcodes at birth as a surrogate for geographic area or space assumes that the mother has not moved into the postcode area after the calamity and before the reporting of a birth.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study suggest that calamities bring about significant pregnancy loss affecting both sexes. The methodology presented of inferring conception date from birth date and using this for analysis, provides a more accurate assessment of first trimester pregnancy losses than raw birth data or sex ratio at birth.

Radiocarbon dioxide detection based on cavity ring-down spectroscopy and a quantum cascade laser

Monitoring of radiocarbon (C14) in carbon dioxide is demonstrated using mid-infrared spectroscopy and a quantum cascade laser. The measurement is based on cavity ring-down spectroscopy, and a high sensitivity is achieved with a simple setup. The instrument was tested using a standardized sample containing elevated levels of radiocarbon. Radiocarbon dioxide could be detected from samples with an isotopic ratio C14/C as low as 50 parts-per-trillion, corresponding to an activity of 5  kBq/m(3) in pure CO(2), or 2  Bq/m(3) in air after extraction of the CO(2) from an air sample. The instrument is simple, compact, and robust, making it the ideal tool for on-site measurements. It is aimed for monitoring radioactive gaseous emissions in a nuclear power environment, during the operation and decommissioning of nuclear power plants. Its high sensitivity also makes it the ideal tool for the detection of leaks in radioactive waste repositories.

Large-scale discovery of novel genetic causes of developmental disorders

Despite three decades of successful, predominantly phenotype-driven discovery of the genetic causes of monogenic disorders, up to half of children with severe developmental disorders of probable genetic origin remain without a genetic diagnosis. Particularly challenging are those disorders rare enough to have eluded recognition as a discrete clinical entity, those with highly variable clinical manifestations, and those that are difficult to distinguish from other, very similar, disorders. Here we demonstrate the power of using an unbiased genotype-driven approach to identify subsets of patients with similar disorders. By studying 1,133 children with severe, undiagnosed developmental disorders, and their parents, using a combination of exome sequencing and array-based detection of chromosomal rearrangements, we discovered 12 novel genes associated with developmental disorders. These newly implicated genes increase by 10% (from 28% to 31%) the proportion of children that could be diagnosed. Clustering of missense mutations in six of these newly implicated genes suggests that normal development is being perturbed by an activating or dominant-negative mechanism. Our findings demonstrate the value of adopting a comprehensive strategy, both genome-wide and nationwide, to elucidate the underlying causes of rare genetic disorders.

Adherence and outcomes of patients prescribed dabigatran (Pradaxa) in routine clinical practice

AIM

To explore and detail clinical experiences of dabigatran, a novel anticoagulant, after it became available in New Zealand in July 2011.

METHODS

A cohort of patients was recruited from Hutt Hospital and the two largest primary care practices in the Hutt Valley region. They were included if they took at least one dose of dabigatran between July 2011 and April 2012. Participants undertook a questionnaire 3-12 months after starting dabigatran assessing adherence, perceived side-effects and complications. Those presenting due to an adverse event were analysed separately.

RESULTS

Of 102 patients identified, 92 were recruited to this study. At a median of 8 months, 70% of participants were still taking dabigatran, significantly lower than in the RE-LY trial at 12 months (P = 0.0002). The commonest reason given for discontinuation was gastrointestinal (GI) side-effects. Rates of serious adverse outcomes on dabigatran therapy were relatively low. Patients expressed polarised comments, both positive and negative, regarding their experiences of dabigatran.

CONCLUSIONS

A high rate of discontinuation of dabigatran, mainly due to GI symptoms, was observed. There does not appear to be any specific predictor of dabigatran tolerance. When prescribed according to guidelines, rates of serious adverse events associated with dabigatran appear to be low.

General practitioners' views on perceived and actual gains, benefits and barriers associated with the implementation of an Australian health assessment for people with intellectual disability

BACKGROUND

Health assessments for people with intellectual disability have been implemented in the UK, New Zealand and Australia, and have led to improved health outcomes. The Comprehensive Health Assessment Program (CHAP) has been shown to improve the health of people with intellectual disability. Similar to other health assessments, it is designed to address healthcare needs, many of which are often overlooked in this population, through better communication between the general practitioner (GP), support worker and the person with intellectual disability. This study investigates GP views of the perceived and actual benefits, gains and barriers associated with its uptake and use in practice.

METHOD

As part of a larger randomised controlled trial of the CHAP, 46 GPs in Queensland, Australia, completed two telephone interviews that included open-ended questions about their perceptions of the health assessment. The GPs were enrolled in the intervention arm of the trial. Interviews took place at commencement and conclusion of the trial to gain the views of GPs as they experienced using the CHAP. Thematic analysis was used to identify key themes and patterns from the GP responses.

RESULTS

Four themes were identified: better healthcare and uncertain benefits captured GP perceptions of the potential gains associated with use of the CHAP, while two further themes, organisational barriers in the general practice setting and engagement across the healthcare triad highlighted strengths and barriers related to implementation. Anticipated concerns about time raised by GPs at commencement of the trial were borne out in practice, but concerns about communication and cooperation of people with disabilities were not. Matters associated with support worker engagement emerged as an area of concern.

CONCLUSIONS

GPs perceive the CHAP as a structured and comprehensive approach to the detection of medical problems as well as an aid in overcoming communication barriers between the doctor and the person with disability. Our findings suggest that some GPs may find it difficult to predict the benefits of using health assessments such as the CHAP. Achieving optimal uptake is likely to require attention at policy and systems levels to address: GP time constraints in providing healthcare to this population; enhancement of support worker training and organisational structures to encourage comprehensive health assessment and follow-up activities; and GP awareness of the improved health outcomes shown to derive from the use of comprehensive health assessments.

Decreased survival of newborn neurons in the dorsal hippocampus after neonatal LPS exposure in mice

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Neonatal inflammation reduces the survival of dividing neurons and astrocytes.

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Neonatal inflammation does not affect the survival of post-mitotic cells.

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Decrease in cell survival was specific for the granule cells of the dorsal blade of the hippocampus.

Experimental studies show that inflammation reduces the regenerative capacity in the adult brain. Less is known about how early postnatal inflammation affects neurogenesis, stem cell proliferation, cell survival and learning and memory in young adulthood. In this study we examined if an early-life inflammatory challenge alters cell proliferation and survival in distinct anatomical regions of the hippocampus and whether learning and memory were affected. Lipopolysaccharide (LPS, 1 mg/kg) was administered to mice on postnatal day (P) 9 and proliferation and survival of hippocampal cells born either prior to (24 h before LPS), or during the inflammatory insult (48 h after LPS) was evaluated. Long-term cell survival of neurons and astrocytes was determined on P 41 and P 60 in the dorsal and ventral horns of the hippocampus. On day 50 the mice were tested in the trace fear conditioning (TFC) paradigm. There was no effect on the survival of neurons and astrocytes that were born before LPS injection. In contrast, the number of neurons and astrocytes that were born after LPS injection were reduced on P 41. The LPS-induced reduction in cell numbers was specific for the dorsal hippocampus. Neither early (48 h after LPS) or late (33 days after LPS) proliferation of cells was affected by neonatal inflammation and neonatal LPS did not alter the behavior of young adult mice in the TFC test. These data highlight that neonatal inflammation specifically affects survival of dividing neurons and astrocytes, but not post-mitotic cells. The reduction in cell survival could be attributed to less cell survival in the dorsal hippocampus, but had no effect on learning and memory in the young adult.

Transverse and vortex domain wall structure in magnetic nanowires with uniaxial in-plane anisotropy

Micromagnetic and analytical models are used to investigate how in-plane uniaxial anisotropy affects transverse and vortex domain walls in nanowires where shape anisotropy dominates. The effect of the uniaxial anisotropy can be interpreted as a modification of the effective wire dimensions. When the anisotropy axis is aligned with the wire axis (θ(a) = 0), the wall width is narrower than when no anisotropy is present. Conversely, the wall width increases when the anisotropy axis is perpendicular to the wire axis (θ(a) = π/2). The anisotropy also affects the nanowire dimensions at which transverse walls become unstable. This phase boundary shifts to larger widths or thicknesses when θ(a) = 0, but smaller widths or thicknesses when θ(a) = π/2.

P2-02-10: Differential Targeting of the RB-Pathway To Expand the Therapeutic Index in the Treatment of Triple Negative Breast Cancer

Background: The retinoblastoma tumor suppressor (RB) is inactivated in a significant fraction of triple negative breast cancers (TNBC). RB loss is believed to contribute to tumor initiation and progression, and provocative data suggest that RB loss is associated with improved response to cytotoxic chemotherapy. Unfortunately, such therapies have significant side effects that impinge on patient quality of life. Here we explored the ability to specifically target RB loss in TNBC to expand the therapeutic index by protecting against undesired side-effects of chemotherapy.

Experimental Design: A combination of cell culture and xenograft models of triple negative breast cancer were used to evaluate how RB-status impinges on sensitivity to chemotherapy. These models were complemented by the analyses of clinical specimens from patients treated with chemotherapy. Parallel use of agents that activate RB function with high specificity were interrogated as potential tissue protectors to ameliorate side effect of chemotherapy.

Results: RB loss in preclinical models is associated with increased sensitivity to conventional cytotoxic chemotherapies that are frequently employed in the treatment of TNBC. The findings were recapitulated through the analyses of clinical specimens, and suggest that the loss of RB could be particularly useful in defining TNBC patients with improved response to chemotherapy. Combination studies of pharmacological activation of the RB pathway and cytotoxic chemotherapies commonly used to treat TNBC demonstrated that activation of RB can modulate the efficacy of cytotoxic compounds in the treatment of TNBC. Importantly, functional studies indicated that RB pathway activation limits cardiotoxicity associated with anthracycline based treatments and correspondingly improve cardiac function in animal studies.

Conclusions: Combined, these studies indicate that RB pathway status could be utilized in the clinic to direct combination treatments that would exploit the sensitivity of RB-deficient tumors to cytotoxic chemotherapies while simultaneously providing protection for normal tissues.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-02-10.