134 research outputs found
A Measure-Theoretic Axiomatisation of Causality
Causality is a central concept in a wide range of research areas, yet there
is still no universally agreed axiomatisation of causality. We view causality
both as an extension of probability theory and as a study of \textit{what
happens when one intervenes on a system}, and argue in favour of taking
Kolmogorov's measure-theoretic axiomatisation of probability as the starting
point towards an axiomatisation of causality. To that end, we propose the
notion of a \textit{causal space}, consisting of a probability space along with
a collection of transition probability kernels, called \textit{causal kernels},
that encode the causal information of the space. Our proposed framework is not
only rigorously grounded in measure theory, but it also sheds light on
long-standing limitations of existing frameworks including, for example,
cycles, latent variables and stochastic processes
Kernel-based independence tests for causal structure learning on functional data
Measurements of systems taken along a continuous functional dimension, such
as time or space, are ubiquitous in many fields, from the physical and
biological sciences to economics and engineering.Such measurements can be
viewed as realisations of an underlying smooth process sampled over the
continuum. However, traditional methods for independence testing and causal
learning are not directly applicable to such data, as they do not take into
account the dependence along the functional dimension. By using specifically
designed kernels, we introduce statistical tests for bivariate, joint, and
conditional independence for functional variables. Our method not only extends
the applicability to functional data of the HSIC and its d-variate version
(d-HSIC), but also allows us to introduce a test for conditional independence
by defining a novel statistic for the CPT based on the HSCIC, with optimised
regularisation strength estimated through an evaluation rejection rate. Our
empirical results of the size and power of these tests on synthetic functional
data show good performance, and we then exemplify their application to several
constraint- and regression-based causal structure learning problems, including
both synthetic examples and real socio-economic data
Capacitive Heart-Rate Sensing on Touch Screen Panel with Laterally Interspaced Electrodes
It is demonstrated that the heart-rate can be sensed capacitively on a touch screen panel (TSP) together with touch signals. The existing heart-rate sensing systems measure blood pulses by tracing the amount of light reflected from blood vessels during a number of cardiac cycles. This type of sensing system requires a considerable amount of power and space to be implemented in multi-functional mobile devices such as smart phones. It is found that the variation of the effective dielectric constant of finger stemming from the difference of systolic and diastolic blood flows can be measured with laterally interspaced top electrodes of TSP. The spacing between a pair of non-adjacent top electrodes turns out to be wide enough to distinguish heart-rate signals from noises. With the aid of fast Fourier transform, the heart-rate can be extracted reliably, which matches with the one obtained by actually counting heart beats on the wrist
Analysis of the predictive role and new proposal for surgical strategies based on the modified Tomita and Tokuhashi scoring systems for spinal metastasis
BACKGROUND: We sought to identify preoperative factors significantly correlated with survival. We also aimed to evaluate the validity of the prognostic scores in the Tomita and Tokuhashi systems and discuss several aspects to improve the predictive accuracy of these systems. Moreover, we suggest modified criteria for selecting treatment strategies. METHODS: In total, the outcomes of 112 patients with spinal metastasis who underwent surgery between January 2006 and June 2011 were retrospectively reviewed. The validity of the prognostic scores was assessed on the basis of their correlation with survival. For various primary malignancies, new scoring criteria were applied in each system according to the survival results obtained in this study. Each revised scoring system was adjusted with a similar principle of scoring as described previously. Patient survival according to each preoperative factor was analyzed by the Kaplan-Meier method. The predictive value of each scoring system was evaluated by the log-rank test and Cox regression analysis. RESULTS: The interval from the diagnosis of the primary malignancy to that of spinal metastasis (p = 0.023) and the interval from the diagnosis of spinal metastasis to surgery (p = 0.039) were significantly correlated with survival. Regarding Tokuhashi scores, the correlation coefficient was 0.790 before adjustment (p = 0.001) and 0.853 after adjustment (p < 0.001). For Tomita scores, the correlation coefficient was -0.994 (p < 0.001) both before and after adjustment. CONCLUSIONS: Tomita scores more accurately predicted survival than Tokuhashi scores. It is helpful to evaluate both scoring systems with adjustment for primary malignancy depending on the clinical setting. Patients with Tomita scores less than or equal to 8 and Tokuhashi scores greater than or equal to 6 are recommended to undergo surgical management
Self-selective ferroelectric memory realized with semimetalic graphene channel
A new concept of read-out method for ferroelectric random-access memory (FeRAM) using a graphene layer as the channel material of bottom-gated field effect transistor structure is demonstrated experimentally. The transconductance of the graphene channel is found to change its sign depending on the direction of spontaneous polarization (SP) in the underlying ferroelectric layer. This indicates that the memory state of FeRAM, specified by the SP direction of the ferroelectric layer, can be sensed unambiguously with transconductance measurements. With the proposed read-out method, it is possible to construct an array of ferroelectric memory cells in the form of a cross-point structure where the transconductance of a crossing cell can be measured selectively without any additional selector. This type of FeRAM can be a plausible solution for fabricating high speed, ultra-low power, long lifetime, and high density 3D stackable non-volatile memory
Scenario-Based Techno-Economic Analysis of Steam Methane Reforming Process for Hydrogen Production
Steam methane reforming (SMR) process is regarded as a viable option to satisfy the growing demand for hydrogen, mainly because of its capability for the mass production of hydrogen and the maturity of the technology. In this study, an economically optimal process configuration of SMR is proposed by investigating six scenarios with different design and operating conditions, including CO2 emission permits and CO2 capture and sale. Of the six scenarios, the process configuration involving CO2 capture and sale is the most economical, with an H-2 production cost of $1.80/kg-H-2. A wide range of economic analyses is performed to identify the tradeoffs and cost drivers of the SMR process in the economically optimal scenario. Depending on the CO2 selling price and the CO2 capture cost, the economic feasibility of the SMR-based H-2 production process can be further improved
Comparison of The Genome Profiles Between Head and Body Lice
The body louse (Pediculus humanus humanus) is known to have diverged from the head louse (P. humanus capitis) but genomic differences between these two subspecies still remain unexplored. To compare genomic profiles between head and body lice, whole genome sequences of head lice were determined by next generation sequencing methods based on both Illumina Genome analyzer and Roche GS FLX pyrosequencing and compared with the reference genome sequences of the body louse. Total consensuses generated by mapping to the body louse genome in conjunction with de novo assembly of head louse genome sequences revealed a head louse genome size of 110 Mbp with a 96% coverage of the body louse genome sequences. A total of 12,651 genes were predicted from the head louse genome sequences although more precise assembly and functional annotation of the genome is required for a more accurate gene count. Among the 873 genes that were putatively specific to the head louse, 15 genes were confirmed to be transcribed in both head and body lice, suggesting the previously estimated gene number of the body louse was likely underestimated. The single nucleotide polymorphism analysis showed that the nucleotide diversity of genome between head and body lice was 2.2%, which was larger than that of the transcriptome between head and body lice. An endosymbiont genome analysis showed that the composition of endosymbionts in head lice was similar to that of body lice and Candidatus Riesia pediculicola was the primary endosymbiont in both head and body lice
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