459 research outputs found
THE MEMS FLUX CONCENTRATOR: POTENTIAL LOW-COST, HIGHSENSITIVITY MAGNETOMETER
Progress on the development of a device, the MEMS flux concentrator, for mitigating the problem of 1/f noise in magnetic sensors will be presented. The MEMS flux concentrator essentially eliminates the effect of 1/f noise by increasing the operating frequency of the sensor to a frequency region where 1/f noise is small. This is accomplished by putting flux concentrators on MEMS structures whose motion modulates the magnetic field at the position of the magnetic sensor. Depending on the sensor, mitigating the effect of 1/f noise will increase the sensitivity of magnetic sensors by one to three orders of magnitude. Combining the MEMS flux concentrator with magnetic tunnel junctions with MgO barriers should lead to low cost magnetic sensors that are able to detect 1 pT signals at 1 Hz
Tensor Methods for Nonlinear Matrix Completion
In the low rank matrix completion (LRMC) problem, the low rank assumption
means that the columns (or rows) of the matrix to be completed are points on a
low-dimensional linear algebraic variety. This paper extends this thinking to
cases where the columns are points on a low-dimensional nonlinear algebraic
variety, a problem we call Low Algebraic Dimension Matrix Completion (LADMC).
Matrices whose columns belong to a union of subspaces (UoS) are an important
special case. We propose a LADMC algorithm that leverages existing LRMC methods
on a tensorized representation of the data. For example, a second-order
tensorization representation is formed by taking the outer product of each
column with itself, and we consider higher order tensorizations as well. This
approach will succeed in many cases where traditional LRMC is guaranteed to
fail because the data are low-rank in the tensorized representation but not in
the original representation. We also provide a formal mathematical
justification for the success of our method. In particular, we show bounds of
the rank of these data in the tensorized representation, and we prove sampling
requirements to guarantee uniqueness of the solution. Interestingly, the
sampling requirements of our LADMC algorithm nearly match the information
theoretic lower bounds for matrix completion under a UoS model. We also provide
experimental results showing that the new approach significantly outperforms
existing state-of-the-art methods for matrix completion in many situations
Genetic progression and the waiting time to cancer
Cancer results from genetic alterations that disturb the normal cooperative
behavior of cells. Recent high-throughput genomic studies of cancer cells have
shown that the mutational landscape of cancer is complex and that individual
cancers may evolve through mutations in as many as 20 different
cancer-associated genes. We use data published by Sjoblom et al. (2006) to
develop a new mathematical model for the somatic evolution of colorectal
cancers. We employ the Wright-Fisher process for exploring the basic parameters
of this evolutionary process and derive an analytical approximation for the
expected waiting time to the cancer phenotype. Our results highlight the
relative importance of selection over both the size of the cell population at
risk and the mutation rate. The model predicts that the observed genetic
diversity of cancer genomes can arise under a normal mutation rate if the
average selective advantage per mutation is on the order of 1%. Increased
mutation rates due to genetic instability would allow even smaller selective
advantages during tumorigenesis. The complexity of cancer progression thus can
be understood as the result of multiple sequential mutations, each of which has
a relatively small but positive effect on net cell growth.Comment: Details available as supplementary material at
http://www.people.fas.harvard.edu/~antal/publications.htm
Prevalence, management and efficacy of treatment in portal vein obstruction after paediatric liver transplantation: protocol of the retrospective international multicentre PORTAL registry
Interventional radiology; Paediatric hepatology; Paediatric transplant surgeryRadiologia intervencionista; Hepatologia pediàtrica; Cirurgia de trasplantament pediàtricRadiología intervencionista; Hepatología pediátrica; Cirugía de trasplante pediátricoIntroduction Portal vein obstruction (PVO) consists of anastomotic stenosis and thrombosis, which occurs due to a progression of the former. The aim of this large-scale international study is to assess the prevalence, current management practices and efficacy of treatment in patients with PVO.
Methods and analysis The Portal vein Obstruction Revascularisation Therapy After Liver transplantation registry will facilitate an international, retrospective, multicentre, observational study, with 25 centres around the world already actively involved. Paediatric patients (aged <18 years) with a diagnosed PVO between 1 January 2001 and 1 January 2021 after liver transplantation will be eligible for inclusion. The primary endpoints are the prevalence of PVO, primary and secondary patency after PVO intervention and current management practices. Secondary endpoints are patient and graft survival, severe complications of PVO and technical success of revascularisation techniques.
Ethics and dissemination Medical Ethics Review Board of the University Medical Center Groningen has approved the study (METc 2021/072). The results of this study will be disseminated via peer-reviewed publications and scientific presentations at national and international conferences
Strengthening a One Health approach to emerging zoonoses
Given the enormous global impact of the COVID-19 pandemic, outbreaks of highly pathogenic avian influenza in Canada, and manifold other zoonotic pathogen activity, there is a pressing need for a deeper understanding of the human-animal-environment interface and the intersecting biological, ecological, and societal factors contributing to the emergence, spread, and impact of zoonotic diseases. We aim to apply a One Health approach to pressing issues related to emerging zoonoses, and propose a functional framework of interconnected but distinct groups of recommendations around strategy and governance, technical leadership (operations), equity, education and research for a One Health approach and Action Plan for Canada. Change is desperately needed, beginning by reorienting our approach to health and recalibrating our perspectives to restore balance with the natural world in a rapid and sustainable fashion. In Canada, a major paradigm shift in how we think about health is required. All of society must recognize the intrinsic value of all living species and the importance of the health of humans, other animals, and ecosystems to health for all
Human resident liver myeloid cells protect against metabolic stress in obesity
Although multiple populations of macrophages have been described in the human liver, their function and turnover in patients with obesity at high risk of developing non-alcoholic fatty liver disease (NAFLD) and cirrhosis are currently unknown. Herein, we identify a specific human population of resident liver myeloid cells that protects against the metabolic impairment associated with obesity. By studying the turnover of liver myeloid cells in individuals undergoing liver transplantation, we find that liver myeloid cell turnover differs between humans and mice. Using single-cell techniques and flow cytometry, we determine that the proportion of the protective resident liver myeloid cells, denoted liver myeloid cells 2 (LM2), decreases during obesity. Functional validation approaches using human 2D and 3D cultures reveal that the presence of LM2 ameliorates the oxidative stress associated with obese conditions. Our study indicates that resident myeloid cells could be a therapeutic target to decrease the oxidative stress associated with NAFLD
- …