1,183 research outputs found
Characterising the convergence of a stochastic simulation model using the bootstrap method
No full textAccepting that all models are wrong, whilst some are useful (G.E.P. Box), this paper will describe how the bootstrap technique has been applied to forecasting for Rolls-Royce, in order to develop a more robust decision support framework that can deliver on the promise of being more useful.Practically speaking, the computational cost of large simulation studies may seem prohibitive, but large enough samples are often required to ensure both the accuracy and precision necessary for unambiguous experimentation. In order to appropriately prioritise opportunities, it is crucially important that an analyst can distinguish the sample differences that are due to experimental changes, rather than imprecise estimates.To illustrate this issue, the bootstrap method has been applied to a complex model of engine maintenance operations to show a clear relationship between sample size, computational power, and precision. As example, all metric means in this case study were shown to have reached an acceptable level of precision within 1024 runs, or one hour of computation time, however, one hour per trial is considered impractically slow with respect to an experimental study requiring upwards of 350 trials. In showing that 25 of 198 tracked metric values require more than 1024 iterations to achieve acceptable levels of precision, this paper illustrates the need to trade off computation time against computation power, thus enabling the sorts of experimentation that usefully prioritise the exploitation of profitable opportunities
Dissociation of erythema and p53 protein expression in human skin following UVB irradiation, and induction of p53 protein and mRNA following application of skin irritants
No full textThe mechanisms mediating the varied effects of ultraviolet radiation (UVR) on human skin are unclear, although a relationship between erythema and DNA damage is suggested by photosensitivity in xeroderma pigmentosum. Increased p53 expression in response to UVR is thought to reflect direct DNA damage, but recent evidence indicates that UVR also activates membrane and cytosolic signal transduction pathways. In this study, we have investigated the relationship between erythema and p53 induction following UVB and whether this p53 response is specific to UVR. p53 protein expression was determined by immunocytochemistry using the monoclonal antibody DO7, and p53 mRNA expression was examined by non-isotopic in situ hybridization. Incremental doses of UVB were administered to the lower back of eight subjects. Immunostaining revealed that p53 positive nuclei were significantly increased 8 h after suberythemogenic doses of UVB (79 +/- 12), compared to normal unirradiated skin (8 +/- 6, p < 0.0005), but no change in p53 mRNA was seen. Higher UVB doses, which resulted in moderate erythema, resulted in a similar or greater induction of p53 protein. Indomethacin (1% w/v), applied immediately after UVB irradiation, significantly inhibited UVB erythema at 8 h in six subjects (p < 0.005), but did not reduce p53 immunostaining. Dithranol (1 microgram/microliter, n = 8), sodium dodecylsulphate (5%, n = 4), and retinoic acid (0.5%, n = 4), applied for 48 h, caused erythema, significantly increased p53 protein levels (p < 0.05), and also increased p53 mRNA. Our results show that in human skin, UVB-induced p53 elevation can be dissociated from erythema and skin irritants can also induce p53 protein. The induction of p53 mRNA by irritants but not UVR suggests different mechanisms of action
Experimenter Demand Effects
No full textExperimenter demand effects arise when participants in an experiment or survey distort their behavior in a misguided attempt to please the experimenter by confirming their research hypothesis. Experimental economists have taken the threat of demand effects seriously and have developed an array of best practices to mitigate their influence, as well as bounding techniques to assess their potential impact on inference. We provide an overview of these techniques and summarize recent empirical assessments of the potential threat of experimenter demand. Our main message is that good design is normally sufficient to address demand concerns, and that bounding approaches work well when concerns remain. Existing empirical evidence suggests that the potential impact of experimenter demand is limited
Ixora longifolia Sm.
No full textIxora longifolia Sm. in A. Rees, Cycl. 19 (1811) no. 3. Materials examined. Table 2. Fig. 4EPublished as part of Ordas, Jorge Anton D., Pinarok, Neil Alejandro A., Romeroso, Roanne B., Alejandro, Grecebio Jonathan D. & Banag-Moran, Cecilia I., 2019, A checklist of Rubiaceae species from Eastern Samar, Visayas, Philippines, pp. 295-312 in Check List 15 (2) on page 303, DOI: 10.15560/15.2.29
The Asp84GIu variant of the melanocortin 1 receptor (MC1R)is associated with melanoma
No full textMelanocyte stimulating hormone (MSH) plays an important role in determining the cutaneous response to ultraviolet radiation and may also influence melanoma progression. We have previously shown that variants of the melanocortin receptor present on melanocytes, MC1R, are associated with sun sensitivity and red hair in a UK population and therefore now consider the gene as a candidate for melanoma susceptibility. We have compared the frequency of known MC1R variants in the second and seventh transmembrane domains in 43 melanoma cases and 44 controls. MC1R variants were more common in cases than controls (?2 = 6.75, 1 d.f.; P = 0.0094) with a relative risk to carriers of variant alleles compared with normal homozygotes of 3.91 (95% c.l.: 1.48-10.35), and a population risk attributable to carriers of 34.6% (95% c.i. 10.7-52.1%). The Asp84Glu variant was only present in melanoma cases and appears to be of particular significance. The contribution of variant MC1R alleles was largely independent of skin type. Variants of the MC1R gene are likely to be causally associated with the development of melanoma
Nitrogen fixation in the western English Channel (NE Atlantic Ocean)
No full textIn temperate Atlantic waters (18.8 to 20.1°C), biological nitrogen fixation has beendemonstrated by 2 independent measurements: 15N-N2 incorporation and nifH identification in theDNA and expressed messenger RNA (mRNA). At 2 stations in the western English Channel, bulkwaters were incubated with 15N-N2. At the high levels of particulate nitrogen (?11.5 ?mol N l–1),absolute fixation rates of 18.9 ± 0.01 and 20.0 nmol N l–1d–1 were determined. While a caveat mustaccompany the magnitude of the rates presented due to the limited number of data, the presence andactivity of diazotrophic organisms in these waters is of ecological significance and may affect currentattitudes to nitrogen and carbon budgets. In particular, our estimate of the rate of N fixation(0.35 mmol N m–2 d–1) is comparable to that of denitrification rates in UK shelf seas. Molecular analysisidentified a diversity of expressed nifH genes, and 21 different prokaryotic nifH transcripts wereidentified
Lectures on the asymptotic theory of ideals
No full textIn this book Professor Rees introduces and proves some of the main results of the asymptotic theory of ideals. The author's aim is to prove his Valuation Theorem, Strong Valuation Theorem, and Degree Formula, and to develop their consequences. The last part of the book is devoted to mixed multiplicities. Here the author develops his theory of general elements of ideals and gives a proof of a generalised degree formula. The reader is assumed to be familiar with basic commutative algebra, as covered in the standard texts, but the presentation is suitable for advanced graduate students. The wor
Protocol for the United Kingdom Rotator Cuff Study (UKUFF) : a randomised controlled trial of open and arthroscopic rotator cuff repair
No full textThis project was funded by the NIHR Health Technology Assessment programme (project number 05/47/02). J. L. Rees has received a grant from Oxford University which is related to this paper. J. Dawson reports that Oxford University has received a grant from HTA which is related to this paper, as well as a study grant.Peer reviewe
Dermato-informatic approaches to understanding and improving lesional diagnostic expertise in cutaneous oncology
No full textCutaneous malignancies represent a quarter of all new cancer diagnoses in the UK.
The key to reducing the tumours’ associated mortality and morbidity is early diagnosis
and treatment. Prompt diagnosis remains predominately a clinical skill, but relatively
little investigation of the cognitive psychology underpinning expertise in this domain
has been undertaken. This thesis aims to improve understanding of these processes
and investigate how lesional diagnostic expertise might be enhanced. A large database
of diagnostically tagged images was captured specifically for this project. A series of
separate studies were undertaken to give insight into how lesional diagnosis occurs
and how it can be improved. The studies highlighted that non-analytical pattern
recognition (NAPR) is likely to predominate in distinguishing malignant and non-malignant
skin lesions and that the widely-promoted rules advocating analytical
pattern recognition (APR) are not effective for discriminating melanoma from benign
pigmented lesions. The keystone to promoting the development of NAPR and thus
diagnostic expertise would seem to be increasing a novice’s personal library of
examples with relevant feedback. Studies demonstrated that current undergraduate
exposure was variable but universally sparse, so simulation by way of diagnostically
tagged images was developed which showed accuracy could be improved by
increased exposure. This improvement occurred in both a content specific and dose
responsive manner. These studies also highlighted that the learning curves for skin
lesions are not uniform. Further studies demonstrated that the choice of images had
implications on the development of diagnostic expertise; suggesting it was important
that these images represent clinical practice rather than “classic” examples
traditionally advocated for teaching purposes. In addition, studies highlighted the
potential benefit of the 3D models developed during this project. Building on the idea
that a personal catalogue of relevant referent images was crucial to enhanced
diagnostic accuracy, prototype software was developed to exteriorise the experts’
library of examples; in the tests described novices utilising the software delivered
superior accuracy than medical students on the completion of their undergraduate
teaching. In summation, the work described shows that by utilising dermato-informatic
approaches lesional diagnostic competence can be improved significantly
The Rees algebra and analytic spread of a divisorial filtration
No full textIn this paper we investigate some properties of Rees algebras of divisorial
filtrations and their analytic spread. A classical theorem of McAdam shows that
the analytic spread of an ideal in a formally equidimensional local ring is
equal to the dimension of the ring if and only if the maximal ideal is an
associated prime of for some . We show in Theorem 1.6
that McAdam's theorem holds for -divisorial filtrations in an
equidimensional local ring which is essentially of finite type over a field.
This generalizes an earlier result for -divisorial filtrations in an
equicharacteristic zero excellent local domain by the author. This theorem does
not hold for more general filtrations.
We consider the question of the asymptotic behavior of the function for a -divisorial filtration
of -primary ideals on a -dimensional normal excellent local ring. It is
known from earlier work of the author that the multiplicity can be irrational. We
show in Lemma 4.1 that the limsup of the first difference function is always
finite for a -divisorial filtration. We then give an example in
Section 4 showing that this limsup may not exist as a limit.
In the final section, we give an example of a symbolic filtration
of a prime ideal in a normal two dimensional excellent local
ring which has the property that the set of Rees valuations of all the symbolic
powers of is infinite.Comment: 25 page
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