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1.
Clin Radiol ; 79(6): e854-e867, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38527920

RESUMO

AIM: Training structure in neuroradiology can be variable, nationally and internationally. Globally, there is a trend towards standardised training pathways, curricula and targeted competencies. Currently, there is limited understanding of the structure of neuroradiology training in the UK. This survey aims to: [1] identify different contemporary models of neuroradiology training in the UK, [2] compare UK trainees' commitments against national and international standards, and [3] understand whether career expectations match the predicted future demands of neuroradiologists. MATERIALS AND METHODS: A survey was developed after consultation with BSNR and UKNG representatives. The eligibility criteria included current neuroradiology trainees in the UK with at least 3 months of experience or had recently completed neuroradiology training, but less than 18 months had elapsed since achieving a certificate of completion of training. RESULTS: A total of 50 trainees responded to the survey; 26 (52%) diagnostic neuroradiologists (DNRs) and 24 (48%) interventional neuroradiologists (INRs) with an overall mean age of 33 years. The mean duration of training at the time of survey was 18 months. The survey details trainee demographics, experience at work, research and teaching commitments and future goals. CONCLUSION: Most respondents are satisfied with their training and 90% want to remain in the UK after completion of training. There is room for improvement but the future of training and working in neuroradiology seems promising internationally, with ever-evolving techniques and developments. ADVANCES IN KNOWLEDGE: Advances in knowledge: This study evaluates neuroradiology training in the UK to enhance the training of future neuroradiologists, and safeguard the future of the speciality.


Assuntos
Educação de Pós-Graduação em Medicina , Reino Unido , Humanos , Inquéritos e Questionários , Adulto , Feminino , Educação de Pós-Graduação em Medicina/métodos , Masculino , Radiologia Intervencionista/educação , Neurorradiografia , Currículo , Competência Clínica
3.
Ultrasound Obstet Gynecol ; 62(2): 248-254, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-36971026

RESUMO

OBJECTIVE: To examine the relationship between umbilical cord insertion site, placental pathology and adverse pregnancy outcome in a cohort of normal and complicated pregnancies. METHODS: Sonographic measurement of the cord insertion and detailed placental pathology were performed in 309 participants. Associations between cord insertion site, placental pathology and adverse pregnancy outcome (pre-eclampsia, preterm birth, small-for-gestational age) were examined. RESULTS: A total of 93 (30%) participants were identified by pathological examination to have a peripheral cord insertion site. Only 41 of the 93 (44%) peripheral cords were detected by prenatal ultrasound. Peripherally inserted cords were associated significantly (P < 0.0001) with diagnostic placental pathology (most commonly with maternal vascular malperfusion (MVM)); of which 85% had an adverse pregnancy outcome. In cases of isolated peripheral cords, without placental pathology, the incidence of adverse outcome was not statistically different when compared to those with central cord insertion and no placental pathology (31% vs 18%; P = 0.3). A peripheral cord with an abnormal umbilical artery (UA) pulsatility index (PI) corresponded to an adverse outcome in 96% of cases compared to 29% when the UA-PI was normal. CONCLUSIONS: This study demonstrates that peripheral cord insertion is often part of the spectrum of findings of MVM disease and is associated with adverse pregnancy outcome. However, adverse outcome was uncommon when there was an isolated peripheral cord insertion and no placental pathology. Therefore, additional sonographic and biochemical features of MVM should be sought when a peripheral cord is observed. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.


Assuntos
Placenta , Resultado da Gravidez , Cordão Umbilical , Feminino , Humanos , Recém-Nascido , Gravidez , Placenta/patologia , Nascimento Prematuro , Artérias Umbilicais/diagnóstico por imagem , Cordão Umbilical/diagnóstico por imagem , Cordão Umbilical/patologia
5.
J Laryngol Otol ; 136(11): 1077-1080, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-35822287

RESUMO

OBJECTIVE: Commercially available suction devices are expensive, large and heavy, and need electricity, and thus restrict the outdoor activity of tracheostomised children and their carers. This study evaluated the efficacy and usability of a simple suction assembly using a syringe and feeding tube in paediatric tracheostomised patients. METHODS: Following the domiciliary usage of this suction assembly instead of their existing suction device for a minimum of 15 days, carers responded to a set of questionnaires containing a subjective scoring system. RESULTS: Ninety-three per cent of the carers considered this assembly as average, good or very good in cleaning the tracheostomy tube. Eighty per cent of the carers considered that this assembly would be suitable when their existing suction machines are unavailable, indicating high usability, and 66.67 per cent of the carers would be confident using this assembly in outdoor settings. CONCLUSION: Larger studies with objective evaluation methods can validate the high efficacy of this simple, inexpensive and easy-to-use, hand-held suction apparatus as reported by the carers of 15 paediatric tracheostomised patients in this study.


Assuntos
Seringas , Traqueostomia , Criança , Humanos , Sucção
6.
Clin Radiol ; 77(9): 684-688, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35764437

RESUMO

AIM: To investigate whether the radiation dose in neurointerventional procedures is reduced if the interventionalist has a better working knowledge and skill to operate the biplane angiographic system (BAS). MATERIALS AND METHODS: It is common practice in most centres in the UK for radiographers to drive many of the functions of the BAS under the instruction of the interventionalist who performs the procedure. The dose profile of a neurointerventionalist who was trained to perform procedures while operating the BAS independently was evaluated against that of a highly experienced neurointerventionalist when operating with a radiographer-assisted BAS. RESULTS: The dose-area product for 57 procedures was collected retrospectively. Working independently resulted in a statistically significant lower mean dose of 4,655 µGy·m2 compared to mean doses above 7,000 µGy·m2 with a radiographer-assisted BAS (p<0.05). Effectively this allowed for the mean dose to be reduced by as much as 38%. CONCLUSION: This study suggests that improved knowledge and skill in operating the BAS gives the neurointerventionalist the opportunity to minimise radiation dose. Therefore, this should be part of the skillset acquired by a qualified neurointerventionalist and be formally addressed in the interventional radiology curriculum.18.


Assuntos
Exposição à Radiação , Angiografia , Humanos , Doses de Radiação , Exposição à Radiação/prevenção & controle , Radiologia Intervencionista , Estudos Retrospectivos
7.
Infect Control Hosp Epidemiol ; 43(4): 435-441, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-34027841

RESUMO

OBJECTIVE: To understand how the different data collections methods of the Alberta Health Services Infection Prevention and Control Program (IPC) and the National Surgical Quality Improvement Program (NSQIP) are affecting reported rates of surgical site infections (SSIs) following total hip replacements (THRs) and total knee replacements (TKRs). DESIGN: Retrospective cohort study. SETTING: Four hospitals in Alberta, Canada. PATIENTS: Those with THR or TKR surgeries between September 1, 2015, and March 31, 2018. METHODS: Demographic information, complex SSIs reported by IPC and NSQIP were compared and then IPC and NSQIP data were matched with percent agreement and Cohen's κ calculated. Statistical analysis was performed for age, gender and complex SSIs. A P value <.05 was considered significant. RESULTS: In total, 7,549 IPC and 2,037 NSQIP patients were compared. The complex SSI rate for NSQIP was higher compared to IPC (THR: 1.19 vs 0.68 [P = .147]; TKR: 0.92 vs 0.80 [P = .682]). After matching, 7 SSIs were identified by both IPC and NSQIP; 3 were identified only by IPC, and 12 were identified only by NSQIP (positive agreement, 0.48; negative agreement, 1.0; κ = 0.48). CONCLUSIONS: Different approaches to monitor SSIs may lead to different results and trending patterns. NSQIP reports total SSI rates that are consistently higher than IPC. If systems are compared at any point in time, confidence on the data may be eroded. Stakeholders need to be aware of these variations and education provided to facilitate an understanding of differences and a consistent approach to SSI surveillance monitoring over time.


Assuntos
Artroplastia de Quadril , Artroplastia do Joelho , Alberta/epidemiologia , Artroplastia de Quadril/efeitos adversos , Artroplastia do Joelho/efeitos adversos , Humanos , Melhoria de Qualidade , Estudos Retrospectivos , Infecção da Ferida Cirúrgica/epidemiologia , Infecção da Ferida Cirúrgica/prevenção & controle
8.
Opt Lett ; 46(9): 2039-2042, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33929413

RESUMO

We report a seeded optical parametric generator (OPG) producing tunable radiation from 4.2-4.6 µm. The seeded OPG employs a 13 mm long CdSiP2 (CSP) crystal cut for non-critical phase-matching, pumped by a nanosecond-pulsed, MHz repetition rate Raman fiber amplifier system at 1.24 µm. A filtered, continuous-wave fiber supercontinuum source at 1.72 µm is used as the seed. The source generates up to 0.25 W of mid-infrared (MIR) idler power with a total pump conversion of 42% (combined signal and idler).

9.
Prensa méd. argent ; 107(2): 80-91, 20210000. tab
Artigo em Inglês | LILACS, BINACIS | ID: biblio-1361359

RESUMO

La enfermedad del corona virus 2 del síndrome respiratorio agudo severo (virus SARS-CoV-2) apareció por primera vez en diciembre de 2019 en Wuhan, China, y desde entonces se ha extendido rápidamente por todo el mundo. Desde entonces, el brote de esta grave enfermedad viral se ha convertido en una amenaza global para la humanidad. El diagnóstico precoz y el aislamiento son las medidas más importantes necesarias para prevenir su propagación. La evidencia anecdótica reciente ha sugerido manifestaciones orales con o sin deterioro olfativo y gustativo en asociación con la enfermedad por coronavirus (COVID-19). La enzima convertidora de angiotensina-2 (ECA-2) se expresa en la mucosa oral en grandes cantidades y, por tanto, puede contribuir a las primeras manifestaciones de esta enfermedad viral mortal. Las manifestaciones bucales de la enfermedad por coronavirus pueden presentarse en forma de lesiones ulcerativas irregulares en relación con diferentes partes de la cavidad oral y, en particular, en relación con la mucosa adherida en la región del paladar duro, así como inflamación y posterior atrofia de las diversas papilas de la lengua. La disfunción olfativa y gustativa asociada también puede conducir a una pérdida parcial y / o incluso completa de la capacidad para oler y saborear en las primeras etapas del inicio de la enfermedad. La evidencia también ha sugerido la presencia de ácido nucleico del SARS-CoV-2 en la saliva humana, lo que la convierte en portadora de la enfermedad viral infecciosa y ayuda en su diagnóstico. Hemos buscado sistemáticamente la base de datos médica para el mismo y hemos revisado toda la literatura disponible hasta el 29 de junio de 2020


Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2 virus) disease had first appeared in December 2019 in Wuhan, China and has been spreading quickly throughout the world since then. Since then, the outbreak of this severe viral disease has become a global threat to humanity. An early diagnosis and isolation are the most significant measures required to prevent its spread. Recent anecdotal evidence has suggested oral manifestations with or, without olfactory and gustatory impairment in association with corona virus disease (COVID-19). Angiotensin converting enzyme-2 (ACE-2) is expressed in oral mucosa in large amounts and can, thus, contribute in the early manifestations of this deadly viral disease. The oral manifestations of corona virus disease can occur in the form of irregular ulcerative lesions in relation to different parts of the oral cavity and particularly, in relation to the attached mucosa in the hard palate region as well as inflammation and subsequent, atrophy of the various tongue papilla. The associated olfactory and gustatory dysfunction can, also, lead to partial and/or, even a complete loss of the ability to smell and taste in the early stages of the disease onset. Evidence has, also, suggested the presence of SARS-CoV-2 nucleic acid in human saliva making it the carrier of the infectious viral disease as well as aiding in its diagnosis. We have systemically searched medical database for the same and have reviewed all the literature available up to 29th of June 2020.


Assuntos
Humanos , Manifestações Bucais , Isolamento de Pacientes , Saliva/imunologia , Diagnóstico Precoce , SARS-CoV-2/imunologia , COVID-19/diagnóstico
10.
Infect Control Hosp Epidemiol ; 42(5): 557-564, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33222722

RESUMO

OBJECTIVE: Adverse outcomes following Clostridioides difficile infection (CDI) are not often reported for long-term care facility (LTCF) residents. We focused on the adverse outcomes due to CDI identified in Alberta LTCFs. METHODS: All positive Clostridioides difficile stool specimens identified by laboratory-identified (LabID) event surveillance in Alberta from 2011 to 2018, along with Alberta Continuing Care Information System, were used to define CDI in Alberta LTCFs. CDI cases were classified as long-term care onset, hospital onset, and community onset. Laboratory records were linked to provincial databases to analyze acute-care admissions and mortality within 30-day post CDI. Age, sex, case classification, episode, and operator type, were investigated using logistic regression. RESULTS: Overall, 902 CDI cases were identified in 762 LTCF residents. Of all CDI events, 860 (95.3%) were long-term care onset, 38 (4.2%) were hospital onset, and 4 (0.4%) were community onset. The CDI rate was 2.0 of 100,000 resident days. In total, 157 residents (20.6%) had 30-day all-cause mortality, 126 CDI cases (14.0%) had 30-day all-cause acute-care admissions. The 30-day all-cause mortality rate was significantly higher in residents aged >80 versus ≤80 years (24.9 vs 12.3 per 100 residents; P < .05). Residents aged >80 years, with hospital-onset CDI, and those staying in private or voluntary LTCFs were more likely to have 30-day all-cause acute-care admissions. CONCLUSIONS: The prevalence of CDI adverse outcomes is in LTCFs was found to be high using LabID event surveillance. Annual review of CDI adverse outcomes using LabID event can minimize the burden of surveillance and standardize the process across all Alberta LTCFs.


Assuntos
Clostridioides difficile , Infecções por Clostridium , Infecção Hospitalar , Alberta/epidemiologia , Clostridioides , Infecções por Clostridium/epidemiologia , Humanos , Laboratórios , Assistência de Longa Duração
11.
Ultrasound Obstet Gynecol ; 57(1): 70-74, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33030756

RESUMO

OBJECTIVE: To evaluate the feasibility of using umbilical artery (UA) Doppler waveforms to measure fetal heart rate (FHR) short-term variation (STV) across gestation. METHODS: This was a prospective longitudinal study, conducted at two study sites, of 195 pregnancies considered low risk. Pulsed-wave Doppler of the UAs was performed at 4-weekly intervals, between 14 and 40 weeks of gestation, using a standardized imaging protocol. Up to 12 consecutive UA Doppler waveforms were analyzed using offline processing software. FHR STV was calculated using average R-R intervals extracted from the waveforms and baseline corrected for FHR. RESULTS: Baseline-corrected FHR STV increased significantly with gestational age (conditional R2 = 0.37; P < 0.0001) and was correlated inversely with FHR (conditional R2 = 0.54; P < 0.0001). The STV ranged (median (interquartile range)) from 3.5 (2.9-4.1) ms at 14-20 weeks' gestation to 6.3 (4.8-7.7) ms at 34-40 weeks' gestation. The change in heart rate STV did not differ between study sites or individual sonographers. CONCLUSIONS: UA Doppler waveforms offer a robust and feasible method to derive STV of the FHR. It should be emphasized that the UA Doppler-derived STV is not interchangeable with measurements derived with computerized cardiotocography. Accordingly, further investigations are needed to validate associations with outcome, in order to determine the value of concurrent fetal cardiovascular and heart rate evaluations that are possible with the technique described here. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.


Assuntos
Retardo do Crescimento Fetal/diagnóstico por imagem , Frequência Cardíaca Fetal , Artéria Cerebral Média/diagnóstico por imagem , Ultrassonografia Doppler/métodos , Artérias Umbilicais/diagnóstico por imagem , Adulto , Cardiotocografia/métodos , Feminino , Idade Gestacional , Humanos , Recém-Nascido , Estudos Longitudinais , Masculino , Artéria Cerebral Média/embriologia , Gravidez , Estudos Prospectivos , Ultrassonografia Pré-Natal
14.
Phys Rev Lett ; 125(10): 100601, 2020 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-32955337

RESUMO

A spin strongly driven by two harmonic incommensurate drives can pump energy from one drive to the other at a quantized average rate, in close analogy with the quantum Hall effect. The pumping rate is a nonzero integer in the topological regime, while the trivial regime does not pump. The dynamical transition between the regimes is sharp in the zero-frequency limit and is characterized by a Dirac point in a synthetic band structure. We show that the pumping rate is half-integer quantized at the transition and present universal Kibble-Zurek scaling functions for energy transfer processes. Our results adapt ideas from quantum phase transitions, quantum information, and topological band theory to nonequilibrium dynamics, and identify qubit experiments to observe the universal linear and nonlinear response of a Dirac point in synthetic dimensions.

15.
Phys Rev Lett ; 124(5): 050602, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-32083902

RESUMO

Constraints play an important role in the entanglement dynamics of many quantum systems. We develop a diagrammatic formalism to exactly evaluate the entanglement spectrum of random pure states in large constrained Hilbert spaces. The resulting spectra may be classified into universal "phases" depending on their singularities. The simplest class of local constraints reveals a nontrivial phase diagram with a Marchenko-Pastur phase which terminates in a critical point with new singularities. We propose a certain quantum defect chain as a microscopic realization of the critical point. The much studied Rydberg-blockaded or Fibonacci chain lies in the Marchenko-Pastur phase with a modified Page correction to the entanglement entropy. Our results predict the entanglement of infinite temperature eigenstates in thermalizing constrained Floquet spin chains, as we confirm numerically.

16.
Acta Crystallogr D Struct Biol ; 75(Pt 1): 41-55, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30644844

RESUMO

LexA is a protein that is involved in the SOS response. The protein from Mycobacterium tuberculosis and its mutants have been biochemically characterized and the structures of their catalytic segments have been determined. The protein is made up of an N-terminal segment, which includes the DNA-binding domain, and a C-terminal segment encompassing much of the catalytic domain. The two segments are defined by a cleavage site. Full-length LexA, the two segments, two point mutants involving changes in the active-site residues (S160A and K197A) and another mutant involving a change at the cleavage site (G126D) were cloned and purified. The wild-type protein autocleaves at basic pH, while the mutants do not. The wild-type and the mutant proteins dimerize and bind DNA with equal facility. The C-terminal segment also dimerizes, and it also shows a tendency to form tetramers. The C-terminal segment readily crystallized. The crystals obtained from attempts involving the full-length protein and its mutants contained only the C-terminal segment including the catalytic core and a few residues preceding it, in a dimeric or tetrameric form, indicating protein cleavage during the long period involved in crystal formation. Modes of tetramerization of the full-length protein similar to those observed for the catalytic core are feasible. A complex of M. tuberculosis LexA and the cognate SOS box could be modeled in which the mutual orientation of the two N-terminal domains differs from that in the Escherichia coli LexA-DNA complex. These results represent the first thorough characterization of M. tuberculosis LexA and provide definitive information on its structure and assembly. They also provide leads for further exploration of this important protein.


Assuntos
Proteínas de Bactérias/química , Mycobacterium tuberculosis/química , Serina Endopeptidases/química , Proteínas de Bactérias/genética , Proteínas Mutantes , Domínios Proteicos , Multimerização Proteica , Resposta SOS em Genética , Serina Endopeptidases/genética
17.
Opt Lett ; 44(24): 6025-6028, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32628210

RESUMO

We demonstrate a nanosecond pulsed source at 620 nm with watt-level average power by frequency-doubling a 1240 nm phosphosilicate Raman fiber amplifier. A gain-switched laser diode operating at 1064 nm is amplified in an ytterbium fiber master oscillator power amplifier system and then converted to 1240 nm using a phosphosilicate Raman fiber amplifier with a conversion efficiency of up to 66%. The Raman fiber amplifier is seeded with a continuous-wave 1240 nm laser diode to obtain narrow-linewidth radiation, which is subsequently frequency-doubled in a periodically poled lithium tantalate crystal. A maximum average power of 1.5 W is generated at 620 nm, corresponding to a pulse energy of 300 nJ at a repetition rate of 5 MHz. The source has excellent beam quality (M2≤1.16) and an optical efficiency (1064 nm to 620 nm) of 20%, demonstrating an effective architecture for generating red pulsed light for biomedical imaging applications.

18.
Phys Rev Lett ; 120(17): 175702, 2018 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-29756831

RESUMO

Unlike random potentials, quasiperiodic modulation can induce localization-delocalization transitions in one dimension. In this Letter, we analyze the implications of this for symmetry breaking in the quasiperiodically modulated quantum Ising chain. Although weak modulation is irrelevant, strong modulation induces new ferromagnetic and paramagnetic phases which are fully localized and gapless. The quasiperiodic potential and localized excitations lead to quantum criticality that is intermediate to that of the clean and randomly disordered models with exponents of ν=1^{+} (exact) and z≈1.9, Δ_{σ}≈0.16, and Δ_{γ}≈0.63 (up to logarithmic corrections). Technically, the clean Ising transition is destabilized by logarithmic wandering of the local reduced couplings. We conjecture that the wandering coefficient w controls the universality class of the quasiperiodic transition and show its stability to smooth perturbations that preserve the quasiperiodic structure of the model.

19.
Med J Malaysia ; 72(5): 282-285, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-29197883

RESUMO

INTRODUCTION: The on-going, international, prospective, observational, longitudinal CLARIFY registry is investigating the demographics, clinical profiles, management and outcomes of patients with stable coronary artery disease (CAD). This paper assesses baseline characteristics, treatment, and clinical outcomes at two years' follow-up of Malaysian/Bruneian patients compared with the overall registry population. METHOD: Between November 2009 and July 2010, outpatients from 45 countries who met the criteria for stable CAD were recruited into the registry. Baseline characteristics were documented at enrolment, and patients were reassessed during their annual visits over a five-year follow-up period. Key outcomes measured were sudden death and cardiovascular (CV) death, non-CV death and CV morbidity. RESULTS: At baseline, 33,283 patients were available for analysis within the registry; 380 and 27 were Malaysians and Bruneians, respectively. The mean ages of Malaysian/Bruneian patients and the rest of the world (RoW) were 57.83 ±9.98 years and 64.23 ± 10.46 years, respectively (p<0.001). The median body mass index values were 26.6 (24.4-29.6) kg/m2 and 27.3 (24.8-30.3) kg/m2, respectively (p=0.014). Malaysian/Bruneian patients had lower rates of myocardial infarction (54.55% versus 59.76%, p=0.033) and higher rates of diabetes (43.24% versus 28.99%, p<0.001) and dyslipidaemia (90.42% versus 74.66%, p<0.001) compared with the RoW. Measured clinical outcomes in Malaysian and Bruneian patients at 2-years follow-up were low and generally comparable to the RoW. CONCLUSION: Malaysian/Bruneian patients with stable CAD tend to be younger with poorer diabetic control compared with the RoW. However, they had similar outcomes as the main registry following two years of treatment.


Assuntos
Doença da Artéria Coronariana/terapia , Avaliação de Resultados em Cuidados de Saúde , Sistema de Registros , Idoso , Brunei/epidemiologia , Doença da Artéria Coronariana/epidemiologia , Demografia , Diabetes Mellitus/epidemiologia , Dislipidemias/epidemiologia , Feminino , Frequência Cardíaca , Humanos , Malásia/epidemiologia , Masculino , Pessoa de Meia-Idade , Infarto do Miocárdio/epidemiologia , Avaliação de Resultados em Cuidados de Saúde/estatística & dados numéricos , Estudos Prospectivos
20.
Philos Trans A Math Phys Eng Sci ; 375(2108)2017 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-29084891

RESUMO

Many-body localized (MBL) systems lie outside the framework of statistical mechanics, as they fail to equilibrate under their own quantum dynamics. Even basic features of MBL systems, such as their stability to thermal inclusions and the nature of the dynamical transition to thermalizing behaviour, remain poorly understood. We study a simple central spin model to address these questions: a two-level system interacting with strength J with N≫1 localized bits subject to random fields. On increasing J, the system transitions from an MBL to a delocalized phase on the vanishing scale Jc(N)∼1/N, up to logarithmic corrections. In the transition region, the single-site eigenstate entanglement entropies exhibit bimodal distributions, so that localized bits are either 'on' (strongly entangled) or 'off' (weakly entangled) in eigenstates. The clusters of 'on' bits vary significantly between eigenstates of the same sample, which provides evidence for a heterogeneous discontinuous transition out of the localized phase in single-site observables. We obtain these results by perturbative mapping to bond percolation on the hypercube at small J and by numerical exact diagonalization of the full many-body system. Our results support the arguments that the MBL phase is unstable in systems with short-range interactions and quenched randomness in dimensions d that are high but finite.This article is part of the themed issue 'Breakdown of ergodicity in quantum systems: from solids to synthetic matter'.

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