Starved picowatt oscillator for remote sensor wake-up timer

A sub-nanowatt oscillator is described. The oscillator is intended for a wake-up timer for remote sensors and hence trades frequency accuracy for reduced power consumption. It is constructed from a five-stage ring of inverters in which the switching speed is reduced using transistors that are always-off, or starved. Fabricated in a 0.35 μm process, the oscillator and its active load dissipate 80 pW at 1.5 Hz from a 1 V supply at 22°C.J.A. Kitchener and B.J. Phillip

Casimir forces and non-Newtonian gravitation

The search for non-relativistic deviations from Newtonian gravitation can lead to new phenomena signalling the unification of gravity with the other fundamental interactions. Various recent theoretical frameworks indicate a possible window for non-Newtonian forces with gravitational coupling strength in the micrometre range. The major expected background in the same range is attributable to the Casimir force or variants of it if dielectric materials, rather than conducting ones, are considered. Here we review the measurements of the Casimir force performed so far in the micrometre range and how they determine constraints on non-Newtonian gravitation, also discussing the dominant sources of false signals. We also propose a geometry-independent parameterization of all data in terms of the measurement of the constant c. Any Casimir force measurement should lead, once all corrections are taken into account, to a determination of the constant c which, in order to assess the accuracy of the measurement, can be compared with its more precise value known through microscopic measurements. Although the last decade of experiments has resulted in solid demonstrations of the Casimir force, the situation is not conclusive with respect to being able to discover new physics. Future experiments and novel phenomenological analysis will be necessary to discover non-Newtonian forces or to push the window for their possible existence into regions of the parameter space which theoretically appear unnatural.Comment: Also available at http://www.iop.org/EJ/abstract/1367-2630/8/10/23

Reinterpreting turbidity: new methodologies for suspended-sediment research

Existing instruments for turbidity measurement vary considerably in terms of the principles of operation, the physical design, and the cost to the researcher. The operational methodologies of late twentieth century turbidity instruments have led to the development of new turbidity measurement standards, and the invention of new turbidity measurement units. These measurement units are invalid and do not have a sound footing with regard to the underlying physics of the scattering and absorption of light by suspended particles. A review of the turbidity literature has shown that the proliferation of these incommensurate units of measurement throughout the physical sciences has caused extensive misinterpretation of turbidity data, particularly concerning its use as a surrogate for suspended sediment concentration (SSC). Turbidity is a complex phenomenon, and its measurement reported in terms of a single numeric quantity in some physically indeterminate units of measurement. It is not necessarily useful to reduce complex data to a single value, since this approach does not permit the researcher any a posteriori opportunity to reinterpret existing data in light of innovations in analysis methodology. This thesis proposes a new way to present turbidity data that will facilitate the cross-comparison of turbidity measurements made by different instruments on any type of suspended sediment. The creation of a new turbidity research instrument that illustrates the application of the new method for reporting turbidity data as a ratio of light attenuation values in decibels, promotes a positive change in direction away from the traditional measurement units. The design process focusses on the instrument calibration procedure. With a simple reinterpretation of the phase-function description of light scattering from suspended particles, measurements of light attenuation made at multiple angles with respect to the axis of the incident light beam, compare easily with the same measurements made using different wavelengths of incident light. This work goes on to introduce new nomenclature that requires the citing of measurement angle and wavelength of light to be an integral part of any recorded turbidity measurement. A modelling approach is used in the evaluation of the new turbidity instrument. This modelling is important for three reasons. First, it identifies which instrument parameters affect the result of a turbidity measurement – the key parameter being the mathematical function that describes the spatial divergence of the incident light beam, which is important to measurement systems that employ incoherent light sources such as LEDs, rather than to laser-based systems. Secondly, the modelling reveals two fundamental theories of light scattering due to suspended particles, both of which are required to describe adequately the turbidity of sediment-laden water. These two theories are Mie scattering and geometric optics. Mie scattering is well accounted for by the developed model - geometric optics, less so. The extent to which the model predictions diverge from the empirical data is characterised by a metric related to the backscatter fraction, and the consistency and linearity of the model is established. Ideas for the improvement of the geometric optics feature of the model are discussed, as is the third reason for the importance of numerical modelling. This third reason relates to the use of multi-parameter turbidity measurements as a means to characterise the properties of a suspended sediment. By simulating precisely the measurement response of the turbidity instrument, then it is notionally possible to infer the properties of an unknown sediment by tuning the model parameters to match the empirical response of the unknown sediment. This tuning process could reveal information pertaining to particle size and shape. Finally, potential applications for the new research instrument focus on improvements to the instrument itself and the methodology, and the further development of the turbidity data reporting nomenclature. Prototype methodologies that relate turbidity to suspended sediment concentration are suggested, which also consider ways in which the optical measurements can potentially classify the physical properties of a sediment

Beyond the ‘Tomlinson Trap’: analysing the effectiveness of section 1 of the Compensation Act 2006

One of the intentions underpinning section 1 of the Compensation Act 2006 was to provide reassurance to individual volunteers, and voluntary organisations, involved in what the provision called ‘desirable activities’ and including sport. The perception was that such volunteers, motivated by an apprehension about their increased vulnerability to negligence liability, and as driven by a fear of a wider societal compensation culture, were engaging excessively in risk-averse behaviour to the detriment of such socially desirable activities. Academic commentary on section 1 of the Compensation Act 2006 has largely regarded the provision as unnecessary and doing little more than restating existing common law practice. This article argues otherwise and, on critically reviewing the emerging jurisprudence, posits the alternative view that section 1, in practice, affords an enhanced level of protection and safeguarding for individuals undertaking functions in connection with a desirable activity. Nonetheless, the occasionally idiosyncratic judicial interpretation given to term ‘desirable activity’, potentially compounded by recent enactment of the Social Action, Responsibility and Heroism Act 2015, remains problematic. Two points of interest will be used to inform this debate. First, an analysis of the then House of Lords’ decision in Tomlinson and its celebrated ‘balancing exercise’ when assessing reasonableness in the context of negligence liability. Second, a fuller analysis of the application of section 1 in the specific context of negligence actions relating to the coaching of sport where it is argued that the, albeit limited, jurisprudence might support the practical utility of a heightened evidential threshold of gross negligence

Splitting or lumping? A conservation dilemma exemplified by the critically endangered Dama Gazelle (Nanger dama)

Managers of threatened species often face the dilemma of whether to keep populations separate to conserve local adaptations and minimize the risk of outbreeding, or whether to manage populations jointly to reduce loss of genetic diversity and minimise inbreeding. In this study we examine genetic relatedness and diversity in three of the five last remaining wild populations of dama gazelle and a number of captive populations, using mtDNA control region and cytochrome b data. Despite the sampled populations belonging to the three putative subspecies, which are delineated according to phenotypes and geographical location, we find limited evidence for phylogeographical structure within the data and no genetic support for the putative subspecies. In the light of these data we discuss the relevance of inbreeding depression, outbreeding depression, adaptive variation, genetic drift, and phenotypic variation to the conservation of the dama gazelle and make some recommendations for its future conservation management. The genetic data suggest that the best conservation approach is to view the dama gazelle as a single species without subspecific divisions

Herschel Spectroscopic Observations of Little Things Dwarf Galaxies

We present far-infrared (FIR) spectral line observations of five galaxies from the Little Things sample: DDO 69, DDO 70, DDO 75, DDO 155, and WLM. While most studies of dwarfs focus on bright systems or starbursts due to observational constraints, our data extend the observed parameter space into the regime of low surface brightness dwarf galaxies with low metallicities and moderate star formation rates. Our targets were observed with Herschel at the [C ii] 158 $m, [O i] 63$m, [O iii] 88 $m, and [N ii] 122$m emission lines using the PACS Spectrometer. These high-resolution maps allow us for the first time to study the FIR properties of these systems on the scales of larger star-forming complexes. The spatial resolution in our maps, in combination with star formation tracers, allows us to identify separate photodissociation regions (PDRs) in some of the regions we observed. Our systems have widespread [C ii] emission that is bright relative to continuum, averaging near 0.5% of the total infrared (TIR) budgetmdashhigher than in solar-metallicity galaxies of other types. [N ii] is weak, suggesting that the [C ii] emission in our galaxies comes mostly from PDRs instead of the diffuse ionized interstellar medium (ISM). These systems exhibit efficient cooling at low dust temperatures, as shown by ([O i]+[C ii])/TIR in relation to 60 $m/100$m, and low [O i]/[C ii] ratios which indicate that [C ii] is the dominant coolant of the ISM. We observe [O iii]/[C ii] ratios in our galaxies that are lower than those published for other dwarfs, but similar to levels noted in spirals.Peer reviewedFinal Accepted Versio

A low-cost HPV immunochromatographic assay to detect high-grade cervical intraepithelial neoplasia

Objective To evaluate the reproducibility and accuracy of the HPV16/18-E6 test. Methods The study population was comprised of 448 women with a previously abnormal Pap who were referred to the Barretos Cancer Hospital (Brazil) for diagnosis and treatment. Two cervical samples were collected immediately before colposcopy, one for the hr-HPV-DNA test and cytology and the other for the HPV16/18-E6 test using high-affinity monoclonal antibodies (mAb). Women with a histologic diagnosis of cervical intraepithelial neoplasia grade 2 or 3 were considered to be positive cases. Different strategies using a combination of screening methods (HPV-DNA) and triage tests (cytology and HPV16/18-E6) were also examined and compared. Results The HPV16/18-E6 test exhibited a lower positivity rate compared with the HPV-DNA test (19.0% vs. 29.3%, p<0.001) and a moderate/high agreement (kappa = 0.68, 95% CI: 0.60-0.75). It also exhibited a significantly lower sensitivity for CIN2+ and CIN3+ detection compared to the HPV-DNA test and a significantly higher specificity. The HPV16/18-E6 test was no different from cytology in terms of sensitivity, but it exhibited a significantly higher specificity in comparison to ASCH+. A triage test after HPV-DNA detection using the HPV16/18-E6 test exhibited a significantly higher specificity compared with a triage test of ASCH+ to CIN2+ (91.8% vs. 87.4%, p = 0.04) and CIN3+ (88.6% vs. 84.0%, p = 0.05). Conclusion The HPV16/18-E6 test exhibited moderate/high agreement with the HPV-DNA test but lower sensitivity and higher specificity for the detection of CIN2+ and CIN3+. In addition, its performance was quite similar to cytology, but because of the structural design addressed for the detection of HPV16/18-E6 protein, the test can miss some CIN2/3+ lesions caused by other high-risk HPV types.Cancer Prevention Department, Center for the Researcher Support and Pathology Department of the Barretos Cancer Hospital. This study was supported by CNPq 573799/2008-3 and FAPESP 2008/57889-1info:eu-repo/semantics/publishedVersio