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1.
Phys Rev Lett ; 131(23): 236502, 2023 Dec 08.
Artículo en Inglés | MEDLINE | ID: mdl-38134803

RESUMEN

We study the temperature evolution of quasiparticles in the correlated metal Sr_{2}RuO_{4}. Our angle resolved photoemission data show that quasiparticles persist up to temperatures above 200 K, far beyond the Fermi liquid regime. Extracting the quasiparticle self-energy, we demonstrate that the quasiparticle residue Z increases with increasing temperature. Quasiparticles eventually disappear on approaching the bad metal state of Sr_{2}RuO_{4} not by losing weight but via excessive broadening from super-Planckian scattering. We further show that the Fermi surface of Sr_{2}RuO_{4}-defined as the loci where the spectral function peaks-deflates with increasing temperature. These findings are in semiquantitative agreement with dynamical mean field theory calculations.

2.
Phys Rev Lett ; 131(4): 046401, 2023 Jul 28.
Artículo en Inglés | MEDLINE | ID: mdl-37566843

RESUMEN

The recent observation of correlated phases in transition metal dichalcogenide moiré systems at integer and fractional filling promises new insight into metal-insulator transitions and the unusual states of matter that can emerge near such transitions. Here, we combine real- and momentum-space mapping techniques to study moiré superlattice effects in 57.4° twisted WSe_{2} (tWSe_{2}). Our data reveal a split-off flat band that derives from the monolayer Γ states. Using advanced data analysis, we directly quantify the moiré potential from our data. We further demonstrate that the global valence band maximum in tWSe_{2} is close in energy to this flat band but derives from the monolayer K states which show weaker superlattice effects. These results constrain theoretical models and open the perspective that Γ-valley flat bands might be involved in the correlated physics of twisted WSe_{2}.

3.
Perspect Public Health ; : 17579139231185999, 2023 Aug 12.
Artículo en Inglés | MEDLINE | ID: mdl-37572017

RESUMEN

AIMS: Unintentional injuries in the home contribute substantially to preschool child morbidity and mortality. Practitioners such as health visitors, family mentors and children's centre staff are well-positioned to facilitate child injury prevention by providing home safety advice to families, and training may enhance their ability to do so. We aimed to assess the impact of child home safety training for these practitioners. METHODS: An explanatory mixed-methods design was used. Practitioners completed questionnaires before, and up to 7 months after, receiving child home safety training and took part in interviews. Seventy-eight health visitors, 72 family mentors and 11 children's centre staff members completed questionnaires. Items were used to calculate scores on home safety knowledge, confidence to provide home safety advice and belief that child home safety promotion is important. Thematic analysis of interviews with seven health visitors and nine family mentors, open-ended responses to the questionnaires and an additional evaluation form was conducted to explore attendees' perceptions of the training and its impact. In addition, seven health visitors and six children's centre staff who had received no training were interviewed. RESULTS: Knowledge was greater post-training than pre-training across all participants (p < .001). When practitioner groups were analysed separately, there were significant increases in family mentors' knowledge (p < .001) and belief (p = .016), and health visitors' confidence (p = .0036). Qualitative findings indicated that most training session attendees valued the training, believed their practice relating to child home safety had improved as a result, and felt further similar training sessions would be beneficial. Those who had not attended the sessions described a need for more child home safety training. CONCLUSIONS: Delivering training to practitioners providing child home safety promotion to families with preschool children can enhance injury prevention knowledge, beliefs and confidence and positively impact on home safety promotion by practitioners.

4.
Annu Rev Food Sci Technol ; 14: 427-448, 2023 03 27.
Artículo en Inglés | MEDLINE | ID: mdl-36972161

RESUMEN

Sensory science is a multidisciplinary field that encompasses a wide variety of established and newly developed tests to document human responses to stimuli. Sensory tests are not limited to the area of food science but they find wide application within the diverse areas of the food science arena. Sensory tests can be divided into two basic groups: analytical tests and affective tests. Analytical tests are generally product-focused, and affective tests are generally consumer-focused. Selection of the appropriate test is critical for actionable results. This review addresses an overview of sensory tests and best practices.


Asunto(s)
Comportamiento del Consumidor , Gusto , Humanos , Gusto/fisiología , Preferencias Alimentarias , Tecnología de Alimentos
5.
Orphanet J Rare Dis ; 18(1): 33, 2023 02 22.
Artículo en Inglés | MEDLINE | ID: mdl-36814255

RESUMEN

BACKGROUND: Long-term sequelae are frequent and often disabling after epidermal necrolysis (Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN)). However, consensus on the modalities of management of these sequelae is lacking. OBJECTIVES: We conducted an international multicentric DELPHI exercise to establish a multidisciplinary expert consensus to standardize recommendations regarding management of SJS/TEN sequelae. METHODS: Participants were sent a survey via the online tool "Survey Monkey" consisting of 54 statements organized into 8 topics: general recommendations, professionals involved, skin, oral mucosa and teeth, eyes, genital area, mental health, and allergy workup. Participants evaluated the level of appropriateness of each statement on a scale of 1 (extremely inappropriate) to 9 (extremely appropriate). Results were analyzed according to the RAND/UCLA Appropriateness Method. RESULTS: Fifty-two healthcare professionals participated. After the first round, a consensus was obtained for 100% of 54 initially proposed statements (disagreement index < 1). Among them, 50 statements were agreed upon as 'appropriate'; four statements were considered 'uncertain', and ultimately finally discarded. CONCLUSIONS: Our DELPHI-based expert consensus should help guide physicians in conducting a prolonged multidisciplinary follow-up of sequelae in SJS-TEN.


Asunto(s)
Síndrome de Stevens-Johnson , Humanos , Síndrome de Stevens-Johnson/complicaciones , Consenso , Piel , Progresión de la Enfermedad
6.
J Affect Disord ; 321: 290-303, 2023 01 15.
Artículo en Inglés | MEDLINE | ID: mdl-36306929

RESUMEN

BACKGROUND: Functional status could predict development of bipolar disorder (BD) or have clinical significance. The relationship between BD risk and functioning is poorly understood. We undertook a systematic review examining the global and social functioning of those at risk for BD. METHODS: We examined observational studies comparing a risk sample with healthy controls or full-threshold BD participants, using measures of global or social functioning. Risk status included family history of BD, meeting risk criteria, or having prodromal symptomatology, or premorbid functioning of persons with BD. Medline, PsycINFO, and Embase were searched. The Newcastle-Ottawa Scale for Cross-Sectional Studies was used to assess quality. Meta-analyses were performed where possible. RESULTS: 7215 studies were screened and 40 studies were included (8474 participants). Risk samples had poorer functioning than controls, and superior functioning to participants with BD. Meta-analysis indicated poorer global functioning among persons with familial risk compared to healthy controls (mean global functional difference: 5.92; 95 % confidence interval: 7.90, 3.95; mean premorbid functioning difference: 2.31; 95 % confidence interval: 0.70, 3.92). Studies with higher proportions of female participants had slightly poorer global functioning. High heterogeneity was attributable functional measures and potentially functionally differential subgroups within the risk samples. LIMITATIONS: Broader measures of functioning, such as neurocognition and behavioural measures, were excluded. Measures of global functioning are limited by conflating functioning and symptoms. CONCLUSIONS: Functioning in the BD risk populations is intermediate to that of healthy controls and persons with BD, indicating their value in definitions of BD risk, in itself a likely heterogeneous state.


Asunto(s)
Trastorno Bipolar , Humanos , Femenino , Interacción Social , Estudios Transversales , Factores de Riesgo
7.
J Sports Sci ; 41(24): 2236-2250, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-38446499

RESUMEN

Low back pain (LBP) is the most common injury in golfers of all abilities. The primary aim of this review was to improve understanding of human golf swing biomechanics associated with LBP. A systematic review using the PRISMA guidelines was performed. Nine studies satisfying inclusion criteria and dually reporting golf swing biomechanics and LBP were identified. Human golf swing biomechanics potentially associated with LBP include: reduced lumbar flexion velocity; reduced transition phase length; reduced lumbar torsional load; earlier onset of erector spinae contraction; increased lumbar lateral flexion velocity; reduced or greater erector spinae activity; and earlier onset of external oblique contraction. These potential associations were undermined by a very limited and conflicting quality of evidence, study designs which introduced a severe potential for bias and a lack of prospective study design. There is no conclusive evidence to support the commonly held belief that LBP is associated with "poor" golf swing technique. The potential associations identified should be further investigated by prospective studies of robust design, recruiting participants of both sexes and dexterities. Once firm associations have been identified, further research is required to establish how this knowledge can be best integrated into injury prevention and rehabilitation.


LBP has the highest incidence of any injury in elite, sub-elite and recreational golfers, causing a significant burden of injury worldwide.There is very limited and conflicting evidence that some human biomechanical factors in the golf swing may be associated with LBP.Prospective studies investigating the full movement pattern are required in order to improve understanding of the potential relationship between the biomechanics of the golf swing and LBP.


Asunto(s)
Golf , Dolor de la Región Lumbar , Masculino , Femenino , Humanos , Dolor de la Región Lumbar/etiología , Dolor de la Región Lumbar/prevención & control , Golf/lesiones , Estudios Prospectivos , Región Lumbosacra , Fenómenos Biomecánicos
8.
Nat Commun ; 12(1): 6739, 2021 Nov 18.
Artículo en Inglés | MEDLINE | ID: mdl-34795276

RESUMEN

Quasiparticle interference (QPI) imaging is well established to study the low-energy electronic structure in strongly correlated electron materials with unrivalled energy resolution. Yet, being a surface-sensitive technique, the interpretation of QPI only works well for anisotropic materials, where the dispersion in the direction perpendicular to the surface can be neglected and the quasiparticle interference is dominated by a quasi-2D electronic structure. Here, we explore QPI imaging of galena, a material with an electronic structure that does not exhibit pronounced anisotropy. We find that the quasiparticle interference signal is dominated by scattering vectors which are parallel to the surface plane however originate from bias-dependent cuts of the 3D electronic structure. We develop a formalism for the theoretical description of the QPI signal and demonstrate how this quasiparticle tomography can be used to obtain information about the 3D electronic structure and orbital character of the bands.

9.
Gynecol Oncol Rep ; 37: 100845, 2021 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-34430691

RESUMEN

This case report reviews the case of a 13-year-old patient who presented with a 9 cm NTRK1-rearranged cervical sarcoma with fibrosarcoma like morphology. At presentation the lesion filled her vagina and pelvis and any attempt at surgical removal would have been morbid and led to loss of fertility. These neoplasms are extremely rare with 18 cases of the uterine cervix reported in the literature, none of which have occurred in a paediatric patient, and none of whom have received neo-adjuvant therapy prior to excision. Based upon evidence that has shown good tolerability and responses of paediatric NTRK fusion-positive solid tumours to TRK inhibitors, both in the neo-adjuvant and upfront setting, this patient was managed with neo-adjuvant entrectinib. Following a dramatic reduction in tumour size confirmed by imaging, she underwent conservative fertility sparing surgery with final histopathology showing no residual disease.

10.
J Hosp Infect ; 115: 93-116, 2021 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-34144096

RESUMEN

BACKGROUND: Antimicrobial stewardship (AMS) programmes optimize antimicrobial use and address antimicrobial resistance. Pharmacists are often key agents of these programmes. The effectiveness of hospital-based AMS interventions when they are led by pharmacists, however, has not previously been reported. AIM: To evaluate the effectiveness of pharmacist-led AMS interventions in improving antimicrobial use for hospital inpatients. METHODS: Standard systematic review methods were used. The search strategies and databases used in a previous Cochrane review were applied. Studies that reported pharmacist-led AMS interventions were included. Narrative synthesis was used to report the findings. PRISMA guidelines were followed. FINDINGS: From 6971 records retrieved and screened, 52 full-text articles were included. Most studies were undertaken in teaching hospitals (N = 45) and many were conducted in North America (N = 27). Most interventions targeted junior or ward physicians and lasted between one and six months. All studies evaluated educational interventions often in combination with other interventions and reported improvements 'in compliance with target AMS practice'. Greater compliance was achieved with multiple interventions. Pharmacist-led interventions reduced the duration of antimicrobial therapy without increasing mortality. No consistency of evidence was achieved in relation to interventions and reduced duration of hospital stay, nor infections due to antimicrobial resistance or occurrence of Clostridium difficile. CONCLUSION: This is the first systematic review to evaluate the effectiveness of pharmacist-led AMS interventions in hospital inpatients. Education-based interventions were effective in increasing guideline compliance and reducing duration of antimicrobial therapy. Future hospital-based AMS programmes should consider the involvement of pharmacists to deliver and promote AMS interventions and programmes.


Asunto(s)
Antiinfecciosos , Programas de Optimización del Uso de los Antimicrobianos , Antiinfecciosos/uso terapéutico , Hospitales de Enseñanza , Humanos , Pacientes Internos , Farmacéuticos
11.
Respir Res ; 22(1): 157, 2021 May 21.
Artículo en Inglés | MEDLINE | ID: mdl-34020644

RESUMEN

BACKGROUND: The long-term consequences of COVID-19 remain unclear. There is concern a proportion of patients will progress to develop pulmonary fibrosis. We aimed to assess the temporal change in CXR infiltrates in a cohort of patients following hospitalisation for COVID-19. METHODS: We conducted a single-centre prospective cohort study of patients admitted to University Hospital Southampton with confirmed SARS-CoV2 infection between 20th March and 3rd June 2020. Patients were approached for standard-of-care follow-up 12-weeks after hospitalisation. Inpatient and follow-up CXRs were scored by the assessing clinician for extent of pulmonary infiltrates; 0-4 per lung (Nil = 0, < 25% = 1, 25-50% = 2, 51-75% = 3, > 75% = 4). RESULTS: 101 patients with paired CXRs were included. Demographics: 53% male with a median (IQR) age 53.0 (45-63) years and length of stay 9 (5-17.5) days. The median CXR follow-up interval was 82 (77-86) days with median baseline and follow-up CXR scores of 4.0 (3-5) and 0.0 (0-1) respectively. 32% of patients had persistent CXR abnormality at 12-weeks. In multivariate analysis length of stay (LOS), smoking-status and obesity were identified as independent risk factors for persistent CXR abnormality. Serum LDH was significantly higher at baseline and at follow-up in patients with CXR abnormalities compared to those with resolution. A 5-point composite risk score (1-point each; LOS ≥ 15 days, Level 2/3 admission, LDH > 750 U/L, obesity and smoking-status) strongly predicted risk of persistent radiograph abnormality (0.81). CONCLUSION: Persistent CXR abnormality 12-weeks post COVID-19 was common in this cohort. LOS, obesity, increased serum LDH, and smoking-status were risk factors for radiograph abnormality. These findings require further prospective validation.


Asunto(s)
COVID-19/complicaciones , COVID-19/diagnóstico por imagen , Tórax/diagnóstico por imagen , Anciano , Estudios de Cohortes , Femenino , Estudios de Seguimiento , Hospitalización , Humanos , L-Lactato Deshidrogenasa/sangre , Tiempo de Internación , Masculino , Persona de Mediana Edad , Obesidad , Reacción en Cadena de la Polimerasa , Estudios Prospectivos , Radiografía Torácica , Factores de Riesgo , Fumar , Resultado del Tratamiento
12.
Oncogene ; 40(18): 3260-3272, 2021 05.
Artículo en Inglés | MEDLINE | ID: mdl-33846571

RESUMEN

The molecular mechanisms of luminal cell differentiation are not understood well enough to determine how differentiation goes awry during oncogenesis. Using RNA-Seq analysis, we discovered that CREB1 plays a central role in maintaining new luminal cell survival and that oncogenesis dramatically changes the CREB1-induced transcriptome. CREB1 is active in luminal cells, but not basal cells. We identified ING4 and its E3 ligase, JFK, as CREB1 transcriptional targets in luminal cells. During luminal cell differentiation, transient induction of ING4 expression is followed by a peak in CREB1 activity, while JFK increases concomitantly with CREB1 activation. Transient expression of ING4 is required for luminal cell induction; however, failure to properly down-regulate ING4 leads to luminal cell death. Consequently, blocking CREB1 increased ING4 expression, suppressed JFK, and led to luminal cell death. Thus, CREB1 is responsible for the suppression of ING4 required for luminal cell survival and maintenance. Oncogenic transformation by suppressing PTEN resulted in constitutive activation of CREB1. However, the tumor cells could no longer fully differentiate into luminal cells, failed to express ING4, and displayed a unique CREB1 transcriptome. Blocking CREB1 in tumorigenic cells suppressed tumor growth in vivo, rescued ING4 expression, and restored luminal cell formation, but ultimately induced luminal cell death. IHC of primary prostate tumors demonstrated a strong correlation between loss of ING4 and loss of PTEN. This is the first study to define a molecular mechanism whereby oncogenic loss of PTEN, leading to aberrant CREB1 activation, suppresses ING4 expression causing disruption of luminal cell differentiation.


Asunto(s)
Próstata , Neoplasias de la Próstata , Proteínas de Ciclo Celular , Diferenciación Celular , Humanos , Masculino , Fosfohidrolasa PTEN
13.
Proc Math Phys Eng Sci ; 477(2255): 20210442, 2021 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-35474957

RESUMEN

Understanding the dynamic condition of the interface between a railway wheel and rail is important to reduce the risks and consider the effectiveness of countermeasures for tribological problems. Traditionally the difficulty in obtaining accurate non-destructive interfacial measurements has hindered systematic experimental investigations. Recently, an ultrasound reflectometry technique has been developed as a direct observation method of a rolling-sliding interface; however, the topography dependence under the high contact pressures in a wheel-rail contact has not been clarified. For this reason, a novel in situ measurement of the contact stiffness using ultrasound reflectometry was carried out for three different levels of roughness. A contact pressure equivalent to that in a wheel-rail interface was achieved by using a high-pressure torsion test approach. The dynamic change of contact stiffness with slip was measured using ultrasound and the influence of roughness was investigated. The measured changes were validated using a newly developed numerical simulation, and mechanisms to explain the observed behaviour were proposed in terms of fracture and plastic deformation of the asperity bonds. These findings could help in understanding the traction characteristics for different roughness conditions and also assist in understanding damage mechanisms better, such as wear and rolling contact fatigue.

14.
BMC Fam Pract ; 21(1): 244, 2020 11 28.
Artículo en Inglés | MEDLINE | ID: mdl-33248452

RESUMEN

BACKGROUND: The expansion of community pharmacy services is one solution to relieve pressure on general practice in the United Kingdom (UK). There is a paucity of research of general practitioners' (GPs') perspectives of quality of care in the community pharmacy sector. The purpose of this study was to explore GPs': Conceptualisation of quality for community pharmacy services, including the management of acute (low acuity) conditions and defining indispensable aspects of the patient experience ('always events') Opinions regarding whether and how to measure quality in the community pharmacy sector METHOD: Semi-structured interviews were conducted with GPs in the UK. GPs were recruited using the snowballing technique and professional networks. Interviews were audio-recorded, transcribed and analysed using an interpretive approach. RESULTS: Interviews were completed with 20 GPs from Scotland (n = 8) and England (n = 12). Multidimensional and inter-related concepts of quality were identified; most dimensions related to patient benefit, as well as impact on GP workload or other health service provision. Interviewees cautioned that "what counts can't always be measured". GPs' expectations of quality often mirrored those of their own sector, but were ambivalent about the adoption of a quality outcome framework-type approach. Pharmacist involvement was expected to ensure quality in the management of 'acute consultations', however, GPs lacked awareness of community pharmacy personnel type, roles and training. Interviewees' perceptions of quality varied by pharmacy type; independent pharmacies were sometimes associated with higher quality service delivery than larger chain organisations. CONCLUSIONS: Quality frameworks for community pharmacy services could be partly informed by GP experience and expectations, but need to be contextual to reflect differences between both settings. The importance of person-centred care, consistency and continuity was emphasised together with the need for competent personnel and privacy of interactions.


Asunto(s)
Servicios Comunitarios de Farmacia , Médicos Generales , Actitud del Personal de Salud , Formación de Concepto , Humanos , Farmacéuticos , Investigación Cualitativa
15.
Nature ; 584(7819): E4, 2020 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-32690939

RESUMEN

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

16.
Sci Adv ; 6(6): eaaz0611, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-32128385

RESUMEN

A nearly free electron metal and a Mott insulating state can be thought of as opposite ends of the spectrum of possibilities for the motion of electrons in a solid. Understanding their interaction lies at the heart of the correlated electron problem. In the magnetic oxide metal PdCrO2, nearly free and Mott-localized electrons exist in alternating layers, forming natural heterostructures. Using angle-resolved photoemission spectroscopy, quantitatively supported by a strong coupling analysis, we show that the coupling between these layers leads to an "intertwined" excitation that is a convolution of the charge spectrum of the metallic layer and the spin susceptibility of the Mott layer. Our findings establish PdCrO2 as a model system in which to probe Kondo lattice physics and also open new routes to use the a priori nonmagnetic probe of photoemission to gain insights into the spin susceptibility of correlated electron materials.

17.
Nat Commun ; 10(1): 5485, 2019 12 02.
Artículo en Inglés | MEDLINE | ID: mdl-31792208

RESUMEN

Band inversions are key to stabilising a variety of novel electronic states in solids, from topological surface states to the formation of symmetry-protected three-dimensional Dirac and Weyl points and nodal-line semimetals. Here, we create a band inversion not of bulk states, but rather between manifolds of surface states. We realise this by aliovalent substitution of Nb for Zr and Sb for S in the ZrSiS family of nonsymmorphic semimetals. Using angle-resolved photoemission and density-functional theory, we show how two pairs of surface states, known from ZrSiS, are driven to intersect each other near the Fermi level in NbGeSb, and to develop pronounced spin splittings. We demonstrate how mirror symmetry leads to protected crossing points in the resulting spin-orbital entangled surface band structure, thereby stabilising surface state analogues of three-dimensional Weyl points. More generally, our observations suggest new opportunities for engineering topologically and symmetry-protected states via band inversions of surface states.

18.
J Laryngol Otol ; 133(2): 125-128, 2019 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-30722793

RESUMEN

BACKGROUND: Pharyngeal pouch surgical treatments can be carried out via an endoscopic or open approach. Injection of botulinum toxin into the cricopharyngeus was first described as an alternative treatment to the more invasive surgical procedures performed for cricopharyngeal dysfunction. It has not been previously described as a treatment option for pharyngeal pouch. OBJECTIVES: To compare operative time, average stay, complication rates and symptom control between endoscopic laser diverticulotomy, botulinum toxin injection and open procedures for pharyngeal pouch patients. METHODS: The medical records for 66 pharyngeal pouch procedures, carried out on 47 patients treated between 2011 and 2017, were identified and reviewed. RESULTS: The mean operative time was 21 minutes for botulinum toxin injection, 38 for endoscopic laser diverticulotomy and 104 for open surgery. The mean hospital stay was 0.6 days for botulinum toxin injection, 4.7 for endoscopic laser diverticulotomy and 4 for open surgery. The improvement in Reflux Symptom Index scores was statistically significant for both endoscopic laser diverticulotomy and botulinum toxin injection. Botulinum toxin injection had a 0 per cent complication rate. CONCLUSION: Botulinum toxin injection is a safe and effective treatment for pharyngeal pouch.


Asunto(s)
Toxinas Botulínicas/administración & dosificación , Síndrome de DiGeorge/tratamiento farmacológico , Endoscopía/métodos , Procedimientos Quirúrgicos Otorrinolaringológicos/métodos , Anciano , Anciano de 80 o más Años , Síndrome de DiGeorge/cirugía , Femenino , Humanos , Inyecciones , Masculino , Persona de Mediana Edad , Neurotoxinas/administración & dosificación , Músculos Faríngeos , Estudios Retrospectivos , Resultado del Tratamiento
19.
Nature ; 566(7745): 518-522, 2019 02.
Artículo en Inglés | MEDLINE | ID: mdl-30742073

RESUMEN

The major breakthroughs in understanding of topological materials over the past decade were all triggered by the discovery of the Z2-type topological insulator-a type of material that is insulating in its interior but allows electron flow on its surface. In three dimensions, a topological insulator is classified as either 'strong' or 'weak'1,2, and experimental confirmations of the strong topological insulator rapidly followed theoretical predictions3-5. By contrast, the weak topological insulator (WTI) has so far eluded experimental verification, because the topological surface states emerge only on particular side surfaces, which are typically undetectable in real three-dimensional crystals6-10. Here we provide experimental evidence for the WTI state in a bismuth iodide, ß-Bi4I4. Notably, the crystal has naturally cleavable top and side planes-stacked via van der Waals forces-which have long been desirable for the experimental realization of the WTI state11,12. As a definitive signature of this state, we find a quasi-one-dimensional Dirac topological surface state at the side surface (the (100) plane), while the top surface (the (001) plane) is topologically dark with an absence of topological surface states. We also find that a crystal transition from the ß-phase to the α-phase drives a topological phase transition from a nontrivial WTI to a normal insulator at roughly room temperature. The weak topological phase-viewed as quantum spin Hall insulators stacked three-dimensionally13,14-will lay a foundation for technology that benefits from highly directional, dense spin currents that are protected against backscattering.

20.
Heredity (Edinb) ; 122(1): 53-68, 2019 01.
Artículo en Inglés | MEDLINE | ID: mdl-29720718

RESUMEN

Understanding how dispersal and gene flow link geographically separated the populations over evolutionary history is challenging, particularly in migratory marine species. In southern right whales (SRWs, Eubalaena australis), patterns of genetic diversity are likely influenced by the glacial climate cycle and recent history of whaling. Here we use a dataset of mitochondrial DNA (mtDNA) sequences (n = 1327) and nuclear markers (17 microsatellite loci, n = 222) from major wintering grounds to investigate circumpolar population structure, historical demography and effective population size. Analyses of nuclear genetic variation identify two population clusters that correspond to the South Atlantic and Indo-Pacific ocean basins that have similar effective breeder estimates. In contrast, all wintering grounds show significant differentiation for mtDNA, but no sex-biased dispersal was detected using the microsatellite genotypes. An approximate Bayesian computation (ABC) approach with microsatellite markers compared the scenarios with gene flow through time, or isolation and secondary contact between ocean basins, while modelling declines in abundance linked to whaling. Secondary-contact scenarios yield the highest posterior probabilities, implying that populations in different ocean basins were largely isolated and came into secondary contact within the last 25,000 years, but the role of whaling in changes in genetic diversity and gene flow over recent generations could not be resolved. We hypothesise that these findings are driven by factors that promote isolation, such as female philopatry, and factors that could promote dispersal, such as oceanographic changes. These findings highlight the application of ABC approaches to infer the connectivity in mobile species with complex population histories and, currently, low levels of differentiation.


Asunto(s)
Evolución Molecular , Variación Genética/genética , Genética de Población , Ballenas/genética , Animales , Clima , ADN Mitocondrial/genética , Flujo Génico/genética , Genotipo , Haplotipos/genética , Repeticiones de Microsatélite/genética , Océano Pacífico , Filogenia , Densidad de Población , Ballenas/fisiología
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