860 research outputs found
Spatial correlation increase in single-sensor satellite data reveals loss of Amazon rainforest resilience
The Amazon rainforest (ARF) is threatened by deforestation and climate
change, which could trigger a regime shift to a savanna-like state. Previous
work suggesting declining resilience in recent decades was based only on local
resilience indicators. Moreover, previous results are potentially biased by the
employed multi-sensor and optical satellite data and undetected anthropogenic
land-use change. Here, we show that the spatial correlation provides a more
robust resilience indicator than local estimators and employ it to measure
resilience changes in the ARF, based on single-sensor Vegetation Optical Depth
data under conservative exclusion of human activity. Our results show an
overall loss of resilience until around 2019, which is especially pronounced in
the southwestern and northern Amazon for the time period from 2002 to 2011. The
demonstrated reliability of spatial correlation in coupled systems suggests
that in particular the southwest of the ARF has experienced pronounced
resilience loss over the last two decades
Prediction of final infarct volume from native CT perfusion and treatment parameters using deep learning
CT Perfusion (CTP) imaging has gained importance in the diagnosis of acute
stroke. Conventional perfusion analysis performs a deconvolution of the
measurements and thresholds the perfusion parameters to determine the tissue
status. We pursue a data-driven and deconvolution-free approach, where a deep
neural network learns to predict the final infarct volume directly from the
native CTP images and metadata such as the time parameters and treatment. This
would allow clinicians to simulate various treatments and gain insight into
predicted tissue status over time. We demonstrate on a multicenter dataset that
our approach is able to predict the final infarct and effectively uses the
metadata. An ablation study shows that using the native CTP measurements
instead of the deconvolved measurements improves the prediction.Comment: Accepted for publication in Medical Image Analysi
Bose-Einstein Condensate in Weak 3d Isotropic Speckle Disorder
The effect of a weak three-dimensional (3d) isotropic laser speckle disorder
on various thermodynamic properties of a dilute Bose gas is considered at zero
temperature. First, we summarize the derivation of the autocorrelation function
of laser speckles in 1d and 2d following the seminal work of Goodman. The goal
of this discussion is to show that a Gaussian approximation of this function,
proposed in some recent papers, is inconsistent with the general background of
laser speckle theory. Then we propose a possible experimental realization for
an isotropic 3d laser speckle potential and derive its corresponding
autocorrelation function. Using a Fourier transform of that function, we
calculate both condensate depletion and sound velocity of a Bose-Einstein
condensate as disorder ensemble averages of such a weak laser speckle potential
within a perturbative solution of the Gross-Pitaevskii equation. By doing so,
we reproduce the expression of the normalfluid density obtained earlier within
the treatment of Landau. This physically transparent derivation shows that
condensate particles, which are scattered by disorder, form a gas of
quasiparticles which is responsible for the normalfluid component
Value of 18F-FES-PET to solve clinical dilemmas in breast cancer patients:a retrospective study
Background: Breast cancer (BC) is a heterogeneous disease, in which estrogen receptor (ER) expression plays an important role in the majority of breast tumors. A clinical dilemma may arise when a metastasis biopsy to determine the ER status cannot be performed safely or when ER heterogeneity is suspected between tumor lesions. Whole-body ER imaging, such as 16α-18F-fluoro-17β-estradiol (18F-FES) positron emission tomography (PET), may have added value in these situations. However, the role of this imaging technique in routine clinical practice remains to be further determined. Therefore, we assessed the value of 18F-FES-PET by evaluating if the physician's clinical dilemma that remained after standard workup was solved by the 18F-FES-PET scan. Methods: In this retrospective study, 18F-FES-PET scans, performed in patients with (suspected) ER+ metastatic BC with remaining clinical dilemma after standard workup, at the University Medical Center of Groningen between November 2009 and January 2019, were included. We investigated whether the physician's clinical dilemma was solved, defined as 1) 18F-FES-PET provided a solution for the clinical dilemma, and/or 2) a treatment decision was based directly on the 18F-FES-PET. In addition, category of clinical dilemma, and rate of 18F-FES positive or negative PET scans were reported, and related to frequency of solved dilemmas. Results: One hundred 18F-FES-PET scans were performed in 83 patients. Clinical dilemma categories were: 1) inability to determine extent of (suspected) metastatic disease with standard workup (n = 52), 2) unclear ER status of the tumor (n = 31), and 3) inability to determine which primary tumor caused metastases (n = 17). Dilemmas were solved by 18F-FES-PET in 87/100 cases (87%). In 81/87 cases a treatment decision was made based directly on the 18F-FES-PET (treatment change: n = 51 cases; continuance: n = 30 cases). The frequency of solved dilemmas was not related to the clinical dilemma category (P = 0.334). However, the frequency of solved dilemmas was related to whether scans were 18F-FES positive (n = 63) or negative (n = 37; p<0.001). Conclusion: For various indications, the 18F-FES-PET scan can help to solve the vast majority of clinical dilemmas that may remain after standard workup. Therefore, the 18F-FES-PET scan has added value in BC patients presenting with a clinical dilemma
A good practice guide for translating and adapting hearing-related questionnaires for different languages and cultures
Objectives: To raise awareness and propose a good practice guide for translating and adapting any hearing-related questionnaire to be used for comparisons across populations divided by language or culture, and to encourage investigators to publish detailed steps.
Design: From a synthesis of existing guidelines, we propose important considerations for getting started, followed by six early steps: (1) Preparation, (2, 3) Translation steps, (4) Committee Review, (5) Field testing and (6) Reviewing and finalising the translation.
Study sample: Not applicable.
Results: Across these six steps, 22 different items are specified for creating a questionnaire that promotes equivalence to the original by accounting for any cultural differences. Published examples illustrate how these steps have been implemented and reported, with shared experiences from the authors, members of the International Collegium of Rehabilitative Audiology and TINnitus research NETwork.
Conclusions: A checklist of the preferred reporting items is included to help researchers and clinicians make informed choices about conducting or omitting any items. We also recommend using the checklist to document these decisions in any resulting report or publication. Following this step-by-step guide would promote quality assurance in multinational trials and outcome evaluations but, to confirm functional equivalence, large-scale evaluation of psychometric properties should follow
Validation of methods for converting the original Disease Activity Score (DAS) to the DAS28
© The Author(s) 2018.The Disease Activity Score (DAS) is integral in tailoring the clinical management of rheumatoid arthritis (RA) patients and is an important measure in clinical research. Different versions have been developed over the years to improve reliability and ease of use. Combining the original DAS and the newer DAS28 data in both contemporary and historical studies is important for both primary and secondary data analyses. As such, a methodologically robust means of converting the old DAS to the new DAS28 measure would be invaluable. Using data from The Early RA Study (ERAS), a sub-sample of patients with both DAS and DAS28 data were used to develop new regression imputation formulas using the total DAS score (univariate), and using the separate components of the DAS score (multivariate). DAS were transformed to DAS28 using an existing formula quoted in the literature, and the newly developed formulas. Bland and Altman plots were used to compare the transformed DAS with the recorded DAS28 to ascertain levels of agreement. The current transformation formula tended to overestimate the true DAS28 score, particularly at the higher end of the scale. A formula which uses all separate components of the DAS was found to estimate the scores with a higher level of precision. A new formula is proposed that can be used by other early RA cohorts to convert the original DAS to DAS28.Peer reviewedFinal Published versio
Weighing up Exercises on Phrasal Verbs: Retrieval Versus Trial-And-Error Practices
EFL textbooks and internet resources exhibit various formats and implementations of exercises on phrasal verbs. The experimental study reported here examines whether some of these might be more effective than others. EFL learners at a university in Japan were randomly assigned to four treatment groups. Two groups were presented first with phrasal verbs and their meaning before they were prompted to retrieve the particles from memory. The difference between these two retrieval groups was that one group studied and then retrieved items one at a time, while the other group studied and retrieved them in sets. The two other groups received the exercises as trial-and-error events, where participants were prompted to guess the particles and were subsequently provided with the correct response. One group was given immediate feedback on each item, while the other group tackled sets of 14 items before receiving feedback. The effectiveness of these exercise implementations was compared through an immediate and a 1-week delayed post-test. The best test scores were obtained when the exercises had served the purpose of retrieval, although this advantage shrank in the delayed test (where scores were poor regardless of treatment condition). On average 70% of the post-test errors produced by the learners who had tackled the exercises by trial-and-error were duplicates of incorrect responses they had supplied at the exercise stage, which indicates that corrective feedback was often ineffective
mm-Wave Systems for High Data Rate Wireless Consumer Applications
ISM spectrum at 60GHz has attracted attention for possible high-speed applications in wireless communications for well over ten years. However, no high volume applications have emerged. Despite progress in mm-wave ICs, the power and cost of these efforts have not reached the level needed for mass deployment. This paper summarises the ARC funded GLIMMR project which aims to remedy this situation by designing systems on silicon that have both low cost and low power. In particular, the paper presents design work done to date that indicate that silicon (particularly SiGe) is on the cusp of being able to provide economical mm-wave systems
Optical Lattices: Theory
This chapter presents an overview of the properties of a Bose-Einstein
condensate (BEC) trapped in a periodic potential. This system has attracted a
wide interest in the last years, and a few excellent reviews of the field have
already appeared in the literature (see, for instance, [1-3] and references
therein). For this reason, and because of the huge amount of published results,
we do not pretend here to be comprehensive, but we will be content to provide a
flavor of the richness of this subject, together with some useful references.
On the other hand, there are good reasons for our effort. Probably, the most
significant is that BEC in periodic potentials is a truly interdisciplinary
problem, with obvious connections with electrons in crystal lattices, polarons
and photons in optical fibers. Moreover, the BEC experimentalists have reached
such a high level of accuracy to create in the lab, so to speak, paradigmatic
Hamiltonians, which were first introduced as idealized theoretical models to
study, among others, dynamical instabilities or quantum phase transitions.Comment: Chapter 13 in Part VIII: "Optical Lattices" of "Emergent Nonlinear
Phenomena in Bose-Einstein Condensates: Theory and Experiment," edited by P.
G. Kevrekidis, D. J. Frantzeskakis, and R. Carretero-Gonzalez (Springer
Series on Atomic, Optical, and Plasma Physics, 2007) - pages 247-26
The patient perspective on absence of disease activity in rheumatoid arthritis: A survey to identify key domains of patient-perceived remission
© 2017, BMJ Publishing Group. All rights reserved. Background: Guidelines suggest treatment in rheumatoid arthritis (RA) to target remission, in close consultation with the patient. Our recent qualitative study of the patients' perspective on remission in RA identified 26 domains. The current study aimed to identify a short list of the most important aspects to inform future research. Methods: Patients with RA from the Netherlands, the UK, Austria, Denmark, France and the USA completed a survey that contained all domains identified in our qualitative study. They rated domains for importance ('not important', 'important' or 'essential' to characterise a period of remission) and if important or essential, whether this domain needs to be 'less', 'almost gone' or 'gone' to reflect remission. Respondents were also asked to determine their personal top 3 most important/ essential domains. Frequency of specific domains in the top 3 was calculated, and domains were sorted on the percentage of patients that evaluated a particular domain as 'essential'. Results: Of 274 respondents, 75% were female, mean (SD) age 57(13) years, disease duration 12(9) years. The top 3 were as follows: pain (67%), fatigue (33%) and independence (19%); domains most frequently rated as 'essential' were as follows: pain (60%), being mobile (52%), physical function (51%), being independent (47%) and fatigue (41%). Pain needed to be less (13%), almost gone (42%) or gone (45%) to reflect remission. Similar patterns were seen for fatigue, independence, mobility and physical functioning. Conclusion: Patients identified pain, fatigue and independence as the most important domains of RA disease activity that need to be improved to reflect remission
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