Unsupervised State-Space Modeling Using Reproducing Kernels

This is the accepted manuscript. The final version is available at http://dx.doi.org/10.1109/TSP.2015.2448527.A novel framework for the design of state-space models (SSMs) is proposed whereby the state-transition function of the model is parametrised using reproducing kernels. The nature of SSMs requires learning a latent function that resides in the state space and for which input-output sample pairs are not available, thus prohibiting the use of gradient-based supervised kernel learning. To this end, we then propose to learn the mixing weights of the kernel estimate by sampling from their posterior density using Monte Carlo methods. We first introduce an offline version of the proposed algorithm, followed by an online version which performs inference on both the parameters and the hidden state through particle filtering. The accuracy of the estimation of the state-transition function is first validated on synthetic data. Next, we show that the proposed algorithm outperforms kernel adaptive filters in the prediction of real-world time series, while also providing probabilistic estimates, a key advantage over standard methods.Felipe Tobar acknowledges financial support from EPSRC grant number EP/L000776/1

Quantum bistability and spin current shot noise of a single quantum dot coupled to an optical microcavity

Here we explore spin dependent quantum transport through a single quantum dot coupled to an optical microcavity. The spin current is generated by electron tunneling between a single doped reservoir and the dot combined with intradot spin flip transitions induced by a quantized cavity mode. In the limit of strong Coulomb blockade, this model is analogous to the Jaynes-Cummings model in quantum optics and generates a pure spin current in the absence of any charge current. Earlier research has shown that in the classical limit where a large number of such dots interact with the cavity field, the spin current exhibits bistability as a function of the laser amplitude that drives the cavity. We show that in the limit of a single quantum dot this bistability continues to be present in the intracavity photon statistics. Signatures of the bistable photon statistics manifest themselves in the frequency dependent shot noise of the spin current despite the fact that the quantum mechanical average spin current no longer exhibits bistability. Besides having significance for future quantum dot based optoelectronic devices, our results shed light on the relation between bistability, which is traditionally viewed as a classical effect, and quantum mechanics

Spin current and shot noise from a quantum dot coupled to a quantized cavity field

We examine the spin current and the associated shot noise generated in a quantum dot connected to normal leads with zero bias voltage across the dot. The spin current is generated by spin flip transitions induced by a quantized electromagnetic field inside a cavity with one of the Zeeman states lying below the Fermi level of the leads and the other above. In the limit of strong Coulomb blockade, this model is analogous to the Jaynes-Cummings model in quantum optics. We also calculate the photon current and photon current shot noise resulting from photons leaking out of the cavity. We show that the photon current is equal to the spin current and that the spin current can be significantly larger than for the case of a classical driving field as a result of cavity losses. In addition to this, the frequency dependent spin (photon) current shot noise show dips (peaks) that are a result of the discrete nature of photons

Response to comments on "magnetic resonance spectroscopy identifies neural progenitor cells in the live human brain"

We reported on a neural progenitor cell biomarker, a lipid-based metabolite enriched in these cells, which we detected using spectroscopy both in vitro and in vivo, and singular value decomposition–based signal processing. The study provided an outline of our computational methodology. Herein, we report more extensively on the method of spectrum analysis used, demonstrating the specificity of our findings

Recruitment strategies and interventions to increase participation in lung cancer screening programmes: A systematic review protocol

IntroductionDespite strong evidence for the efficacy of low-radiation dose CT (LDCT) in reducing lung cancer (LC) mortality, implementing LC screening (LCS) programmes remains a challenge. We aim to systematically review the evidence on the strategies used to recruit the adult population at risk of LC to LDCT within LCS programmes and to estimate the effectiveness of interventions identified, used to reach the potentially eligible population, increase participation and informed choice, and ensure equitable access.Methods and analysisThis sequential systematic literature review will consist of three steps: (1) a scoping review of existing strategies and organisational models for LCS; (2) selecting papers reporting relevant outcomes (test coverage, screening participation and informed choice) and comparing results among different models; (3) a systematic review of interventions implemented to increase participation in LCS programmes. Each step will follow the methodological guidelines provided by the Cochrane Collaboration and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Data sources include electronic databases such as Medline (PubMed version), Embase, CINAHL (Ebsco version), Scopus and Cochrane CENTRAL. The search will be limited to studies published from January 2000 to March 2023 in English, Italian, French, Spanish, Serbian and Croatian language. Findings will be synthesised quantitatively and qualitatively as appropriate. Risk of bias assessment will be only applied to studies selected in the second and third steps. The quality of evidence will be summarised for each outcome using the Grading Recommendation Assessment, Development and Evaluation methodology.Ethics and disseminationGiven that this is a review of existing literature, ethics approval is not required. The results will be published in peer-reviewed scientific journals and presented at relevant conferences. The findings of this review will help guide health authorities in organising LCS programmes and developing recommendations, policies, and actions at national and regional levels.PROSPERO registration numberCRD42023408357

SARS-CoV-2 transmission patterns in educational settings during the Alpha wave in Reggio-Emilia, Italy

: Different monitoring and control policies have been implemented in schools to minimize the spread of SARS-CoV-2. Transmission in schools has been hard to quantify due to the large proportion of asymptomatic carriers in young individuals. We applied a Bayesian approach to reconstruct the transmission chains between 284 SARS-CoV-2 infections ascertained during 87 school outbreak investigations conducted between March and April 2021 in Italy. Under the policy of reactive quarantines, we found that 42.5% (95%CrI: 29.5-54.3%) of infections among school attendees were caused by school contacts. The mean number of secondary cases infected at school by a positive individual during in-person education was estimated to be 0.33 (95%CrI: 0.23-0.43), with marked heterogeneity across individuals. Specifically, we estimated that only 26.0% (95%CrI: 17.6-34.1%) of students and school personnel who tested positive during in-person education caused at least one secondary infection at school. Positive individuals who attended school for at least 6 days before being isolated or quarantined infected on average 0.49 (95%CrI: 0.14-0.83) secondary cases. Our findings provide quantitative insights on the contribution of school transmission to the spread of SARS-CoV-2 in young individuals. Identifying positive cases within 5 days after exposure to their infector could reduce onward transmission at school by at least 30%

Twin-screw granulation – a systematic analysis of process parameters

Twin-screw granulation has a significant advantage over traditional granulation methods leading to the possibility of continuous manufacturing. Although this technology has drawn attention in recent years, the general understanding of the process is limited. This study gives a brief overview of the most important process parameters and their influence on product quality. Experimental results from a benchtop granulator and an in-line particle size measurement have been analysed. From this basic study conclusions can be drawn how to tailor the particle size distribution in twin-screw granulation. The most crucial parameters are the liquid-to-solid ratio and the filling level of the screws

Red wine consumption increases antioxidant status and decreases oxidative stress in the circulation of both young and old humans

Background: Red wine contains a naturally rich source of antioxidants, which may protect the body from oxidative stress, a determinant of age-related disease. The current study set out to determine the in vivo effects of moderate red wine consumption on antioxidant status and oxidative stress in the circulation.Methods: 20 young (18&ndash;30 yrs) and 20 older (&ge; 50 yrs) volunteers were recruited. Each age group was randomly divided into treatment subjects who consumed 400 mL/day of red wine for two weeks, or control subjects who abstained from alcohol for two weeks, after which they crossed over into the other group. Blood samples were collected before and after red wine consumption and were used for analysis of whole blood glutathione (GSH), plasma malondialdehyde (MDA) and serum total antioxidant status.Results: Results from this study show consumption of red wine induced significant increases in plasma total antioxidant status (P &lt; 0.03), and significant decreases in plasma MDA (P &lt; 0.001) and GSH (P &lt; 0.004) in young and old subjects. The results show that the consumption of 400 mL/day of red wine for two weeks, significantly increases antioxidant status and decreases oxidative stress in the circulation.Conclusion: It may be implied from this data that red wine provides general oxidative protection and to lipid systems in circulation via the increase in antioxidant status.<br /

Magnetic resonance spectroscopy identifies neural progenitor cells in the live human brain

The identification of neural stem and progenitor cells (NPCs) by in vivo brain imaging could have important implications for diagnostic, prognostic, and therapeutic purposes. We describe a metabolic biomarker for the detection and quantification of NPCs in the human brain in vivo. We used proton nuclear magnetic resonance spectroscopy to identify and characterize a biomarker in which NPCs are enriched and demonstrated its use as a reference for monitoring neurogenesis. To detect low concentrations of NPCs in vivo, we developed a signal processing method that enabled the use of magnetic resonance spectroscopy for the analysis of the NPC biomarker in both the rodent brain and the hippocampus of live humans. Our findings thus open the possibility of investigating the role of NPCs and neurogenesis in a wide variety of human brain disorders