344 research outputs found
Contrast Mechanisms for the Detection of Ferroelectric Domains with Scanning Force Microscopy
We present a full analysis of the contrast mechanisms for the detection of
ferroelectric domains on all faces of bulk single crystals using scanning force
microscopy exemplified on hexagonally poled lithium niobate. The domain
contrast can be attributed to three different mechanisms: i) the thickness
change of the sample due to an out-of-plane piezoelectric response (standard
piezoresponse force microscopy), ii) the lateral displacement of the sample
surface due to an in-plane piezoresponse, and iii) the electrostatic tip-sample
interaction at the domain boundaries caused by surface charges on the
crystallographic y- and z-faces. A careful analysis of the movement of the
cantilever with respect to its orientation relative to the crystallographic
axes of the sample allows a clear attribution of the observed domain contrast
to the driving forces respectively.Comment: 8 pages, 8 figure
An Evaluation Of Provision In A School Designated As Catering For Pupils Categorised As Having 'Emotional And Behavioural Difficulties' In The Light Of The Perspectives And Expectations Of Its Various Stakeholders
Line End is an 11-16 day school for pupils categorised as having emotional and behavioural difficulties (EBD). It is maintained by Farside Local Education Authority, and provides secondary education for pupils who are statemented as having emotional and behavioural difficulties. Some have additional learning difficulties, this assessment being based on reading ages that are considerably lower than their chronological ages, and scores in KS2 SATs that are below National averages. All referrals come through the local authority’s special educational needs department; invariably, the pupils who are placed at Line End either transfer from the EBD primary unit, or are those who have been excluded from mainstream secondary schools within the borough.
The aim of the study is to establish the extent to which Line End is felt to be effective by its various stakeholders; and in establishing this position, it is first important to elicit the criteria by which the various stakeholders judge the school to be effective. The first phase of the study, therefore, is aimed at eliciting these stakeholder criteria, whilst the second phase focuses on the extent to which the school is perceived to be effective in its various areas of provision, based on these very criteria. A subsequent analysis of findings seeks to examine stakeholder perspectives, and the extent to which there is congruence and/or divergence of perspective amongst and between stakeholders might create conflict or tensions between and amongst stakeholders.
Findings from the first phase of the study suggest that there is broad agreement amongst stakeholders about what should constitute effective provision for Line End pupils: addressing both academic and emotional/behavioural needs effectively, providing a safe and positive environment in which to make such provision, and providing opportunities for the reintegration of pupils to mainstream where appropriate and practicable. These three areas reflect the three major aims of the school as outlined in the staff handbook, and alongside these as key indicators of quality, stakeholders included relationships between home and school, and the management/organisation of the school -the extent to which it was strategically or ‘crisis’ managed.
Findings from the second phase of the research suggested that the school was perceived to be effective by virtually all of its stakeholders - in some areas for some of the time. There were differences of perspective within stakeholder groups, and sometimes differences of emphasis between stakeholder groups. These differences did not necessarily lead to tension, as it was possible for differing perspectives to co-exist; the tensions became evident when perspectives conflicted rather than co-existed, as the group or individual who held the greatest power would invariably have its way in translating its perspective into policy and practic
Three-dimensionality of space and the quantum bit: an information-theoretic approach
It is sometimes pointed out as a curiosity that the state space of quantum
two-level systems, i.e. the qubit, and actual physical space are both
three-dimensional and Euclidean. In this paper, we suggest an
information-theoretic analysis of this relationship, by proving a particular
mathematical result: suppose that physics takes place in d spatial dimensions,
and that some events happen probabilistically (not assuming quantum theory in
any way). Furthermore, suppose there are systems that carry "minimal amounts of
direction information", interacting via some continuous reversible time
evolution. We prove that this uniquely determines spatial dimension d=3 and
quantum theory on two qubits (including entanglement and unitary time
evolution), and that it allows observers to infer local spatial geometry from
probability measurements.Comment: 13 + 22 pages, 9 figures. v4: some clarifications, in particular in
Section V / Appendix C (added Example 39
Land subsidence hazard in iran revealed by country-scale analysis of sentinel-1 insar
Many areas across Iran are subject to land subsidence, a sign of exceeding stress due to the over-extraction of groundwater during the past decades. This paper uses a huge dataset of Sentinel-1, acquired since 2014 in 66 image frames of 250×250km, to identify and monitor land subsidence across Iran. Using a two-step time series analysis, we first identify subsidence zones at a medium scale of 100m across the country. For the first time, our results provide a comprehensive nationwide map of subsidence in Iran and recognize its spatial distribution and magnitude. Then, in the second step of analysis, we quantify the deformation time series at the highest possible resolution to study its impact on civil infrastructure. The results spots the hazard posed by land subsidence to different infrastructure. Examples of road and railways affected by land subsidence hazard in Tehran and Mashhad, two of the most populated cities in Iran, are presented in this study
Exploring cloud-based platforms for rapid insar time series analysis
The idea of near real-time deformation analysis using Synthetic Aperture Radar (SAR) data as a response to natural and anthropogenic disasters has been an interesting topic in the last years. A major limiting factor for this purpose has been the non-availability of both spatially and temporally homogeneous SAR datasets. This has now been resolved thanks to the SAR data provided by the Sentinel-1A/B missions, freely available at a global scale via the Copernicus program of the European Space Agency (ESA). Efficient InSAR analysis in the era of Sentinel demands working with cloud-based platforms to tackle problems posed by large volumes of data. In this study, we explore a variety of existing cloud-based platforms for Multioral Interferometric SAR (MTI) analysis and discuss their opportunities and limitations
The Astropy Problem
The Astropy Project (http://astropy.org) is, in its own words, "a community
effort to develop a single core package for Astronomy in Python and foster
interoperability between Python astronomy packages." For five years this
project has been managed, written, and operated as a grassroots,
self-organized, almost entirely volunteer effort while the software is used by
the majority of the astronomical community. Despite this, the project has
always been and remains to this day effectively unfunded. Further, contributors
receive little or no formal recognition for creating and supporting what is now
critical software. This paper explores the problem in detail, outlines possible
solutions to correct this, and presents a few suggestions on how to address the
sustainability of general purpose astronomical software
Refinement type contracts for verification of scientific investigative software
Our scientific knowledge is increasingly built on software output. User code
which defines data analysis pipelines and computational models is essential for
research in the natural and social sciences, but little is known about how to
ensure its correctness. The structure of this code and the development process
used to build it limit the utility of traditional testing methodology. Formal
methods for software verification have seen great success in ensuring code
correctness but generally require more specialized training, development time,
and funding than is available in the natural and social sciences. Here, we
present a Python library which uses lightweight formal methods to provide
correctness guarantees without the need for specialized knowledge or
substantial time investment. Our package provides runtime verification of
function entry and exit condition contracts using refinement types. It allows
checking hyperproperties within contracts and offers automated test case
generation to supplement online checking. We co-developed our tool with a
medium-sized (3000 LOC) software package which simulates
decision-making in cognitive neuroscience. In addition to helping us locate
trivial bugs earlier on in the development cycle, our tool was able to locate
four bugs which may have been difficult to find using traditional testing
methods. It was also able to find bugs in user code which did not contain
contracts or refinement type annotations. This demonstrates how formal methods
can be used to verify the correctness of scientific software which is difficult
to test with mainstream approaches
Ambulatory blood pressure monitoring and renal functions in children with a solitary kidney
The aim of this study is to investigate the blood pressure (BP) profile, microalbuminuria, renal functions, and relations with remaining normal kidney size in children with unilateral functioning solitary kidney (UFSK). Sixty-six children with UFSK were equally divided into three groups: unilateral renal agenesis (URA), unilateral atrophic kidney (UAK), and unilateral nephrectomy (UNP). Twenty-two age-, weight-, and height-matched healthy children were considered as a control group. The serum creatinine level and first-morning urine microalbumin and creatinine concentrations were determined by the standard methods. Also, the BP profile was determined by ambulatory blood pressure monitoring (ABPM). We found that the serum creatinine level was higher and creatinine clearance was lower in each patient groups compared to those of the control group (p < 0.05). Compared with the controls, each group of patients had mean office, 24-h, daytime, and night-time systolic and diastolic BP values similar to those of the controls (p > 0.05). An inverse correlation was found between the renal size standard deviation scores (SDS) of normal kidneys and 24-h systolic and diastolic BP load SDS in all of the patients (p < 0.05; r = −0.372, r = −0.295, respectively). The observed relationship between renal size SDS and 24-h mean arterial pressure (MAP), systolic and diastolic BP load SDS suggests that children with UFSK should be evaluated by using ABPM for the risk of hypertension
Chronic kidney disease in children: the global perspective
In contrast to the increasing availability of information pertaining to the care of children with chronic kidney disease (CKD) from large-scale observational and interventional studies, epidemiological information on the incidence and prevalence of pediatric CKD is currently limited, imprecise, and flawed by methodological differences between the various data sources. There are distinct geographic differences in the reported causes of CKD in children, in part due to environmental, racial, genetic, and cultural (consanguinity) differences. However, a substantial percentage of children develop CKD early in life, with congenital renal disorders such as obstructive uropathy and aplasia/hypoplasia/dysplasia being responsible for almost one half of all cases. The most favored end-stage renal disease (ESRD) treatment modality in children is renal transplantation, but a lack of health care resources and high patient mortality in the developing world limits the global provision of renal replacement therapy (RRT) and influences patient prevalence. Additional efforts to define the epidemiology of pediatric CKD worldwide are necessary if a better understanding of the full extent of the problem, areas for study, and the potential impact of intervention is desired
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