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1.
Mater Des ; 2152022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35370339

RESUMO

Bimetallic structures of nickel (Ni) and commercially pure titanium (CP Ti) were manufactured in three different configurations via directed energy deposition (DED)-based metal additive manufacturing (AM). To understand whether the bulk properties of these three composites are dominated by phase formation at the interface, their directional dependence on mechanical properties was tested. X-ray diffraction (XRD) pattern confirmed the intermetallic NiTi phase formation at the interface. Microstructural gradient observed at the heat-affected zone (HAZ) areas. The longitudinal samples showed about 12% elongation, while the same was 36% for the transverse samples. During compressive deformation, strain hardening from dislocation accumulation was observed in the CP Ti and transverse samples, but longitudinal samples demonstrated failures similar to a brittle fracture at the interface. Transverse samples also showed shear band formation indicative of ductile failures. Our results demonstrate that AM can design innovative bimetallic structures with unique directional mechanical properties.

2.
Science ; 375(6576): 101-104, 2022 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-34990239

RESUMO

Climate change is expected to result in smaller fish size, but the influence of fishing has made it difficult to substantiate the theorized link between size and ocean warming and deoxygenation. We reconstructed the fish community and oceanographic conditions of the most recent global warm period (last interglacial; 130 to 116 thousand years before present) by using sediments from the northern Humboldt Current system off the coast of Peru, a hotspot of small pelagic fish productivity. In contrast to the present-day anchovy-dominated state, the last interglacial was characterized by considerably smaller (mesopelagic and goby-like) fishes and very low anchovy abundance. These small fish species are more difficult to harvest and are less palatable than anchovies, indicating that our rapidly warming world poses a threat to the global fish supply.


Assuntos
Mudança Climática , Ecossistema , Peixes , Sedimentos Geológicos , Oxigênio/análise , Água do Mar , Animais , Tamanho Corporal , Peixes/anatomia & histologia , Oceano Pacífico , Paleontologia , Peru , Água do Mar/química , Temperatura
3.
New Phytol ; 233(3): 1426-1439, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-34170548

RESUMO

Parallel evolution of similar morphologies in closely related lineages provides insight into the repeatability and predictability of evolution. In the genus Antirrhinum (snapdragons), as in other plants, a suite of morphological characters are associated with adaptation to alpine environments. We tested for parallel trait evolution in Antirrhinum by investigating phylogenetic relationships using restriction-site associated DNA (RAD) sequencing. We then associated phenotypic information to our phylogeny to reconstruct the patterns of morphological evolution and related this to evidence for hybridisation between emergent lineages. Phylogenetic analyses showed that the alpine character syndrome is present in multiple groups, suggesting that Antirrhinum has repeatedly colonised alpine habitats. Dispersal to novel environments happened in the presence of intraspecific and interspecific gene flow. We found support for a model of parallel evolution in Antirrhinum. Hybridisation in natural populations, and a complex genetic architecture underlying the alpine morphology syndrome, support an important role of natural selection in maintaining species divergence in the face of gene flow.


Assuntos
Antirrhinum , Antirrhinum/genética , Evolução Biológica , Fluxo Gênico , Fenótipo , Filogenia , Seleção Genética
4.
Chem Commun (Camb) ; 58(6): 815-818, 2022 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-34928278

RESUMO

We trace a polymorphic phase change in solid ammonia films through the emergence of a Frenkel exciton at 194.4 nm, for deposition temperatures of 48 K, 50 K and 52 K. Observations on a timescale of hours give unparalleled access to the individual processes of nucleation and the phase change itself. The excitonic transition is forbidden in the low temperature phase, but greater flexing of the solid state structure in the higher temperature phase makes the transition allowed, as the nano-crystals approach ∼30 unit cells through nucleation. We find activation energies of 21.7 ± 0.6 kJ mol-1 for nucleation and 22.8 ± 0.6 kJ mol-1 for the phase change, corresponding to the breaking of two to three hydrogen bonds.

5.
Front Physiol ; 12: 695431, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34776991

RESUMO

Correlated, spontaneous neural activity is known to play a necessary role in visual development, but the higher-order statistical structure of these coherent, amorphous patterns has only begun to emerge in the past decade. Several computational studies have demonstrated how this endogenous activity can be used to train a developing visual system. Models that generate spontaneous activity analogous to retinal waves have shown that these waves can serve as stimuli for efficient coding models of V1. This general strategy in development has one clear advantage: The same learning algorithm can be used both before and after eye-opening. This same insight can be applied to understanding LGN/V1 spontaneous activity. Although lateral geniculate nucleus (LGN) activity has been less discussed in the literature than retinal waves, here we argue that the waves found in the LGN have a number of properties that fill the role of a training pattern. We make the case that the role of "innate learning" with spontaneous activity is not only possible, but likely in later stages of visual development, and worth pursuing further using an efficient coding paradigm.

6.
Plants (Basel) ; 10(11)2021 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-34834833

RESUMO

Vegetables and herbs play a central role in the human diet due to their low fat and calory content and essential antioxidant, phytochemicals, and fiber. It is well known that the manipulation of light wavelengths illuminating the crops can enhance their growth rate and nutrient contents. To date, it has not been easy to generalize the effects of LED illumination because of the differences in the plant species investigated, the measured traits, the way wavelengths have been manipulated, and the plants' growing environments. In order to address this gap, we undertook a quantitative review of LED manipulation in relation to plant traits, focusing on vegetables and herbs. Here, we use standardized measurements of biomass, antioxidant, and other quantitative characteristics together with the whole range of the photosynthetic photon flux density (PPFD). Overall, our review revealed support for the claims that the red and blue LED illumination is more reliable and efficient than full spectrum illumination and increases the plant's biomass and nutritional value by enhancing the photosynthetic activity, antioxidant properties, phenolic, and flavonoids contents. Although LED illumination provides an efficient way to improve yield and modify plant properties, this study also highlights the broad range of responses among species, varieties traits, and the age of plant material.

7.
PLoS Comput Biol ; 17(9): e1009456, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34570753

RESUMO

A number of neuroimaging techniques have been employed to understand how visual information is transformed along the visual pathway. Although each technique has spatial and temporal limitations, they can each provide important insights into the visual code. While the BOLD signal of fMRI can be quite informative, the visual code is not static and this can be obscured by fMRI's poor temporal resolution. In this study, we leveraged the high temporal resolution of EEG to develop an encoding technique based on the distribution of responses generated by a population of real-world scenes. This approach maps neural signals to each pixel within a given image and reveals location-specific transformations of the visual code, providing a spatiotemporal signature for the image at each electrode. Our analyses of the mapping results revealed that scenes undergo a series of nonuniform transformations that prioritize different spatial frequencies at different regions of scenes over time. This mapping technique offers a potential avenue for future studies to explore how dynamic feedforward and recurrent processes inform and refine high-level representations of our visual world.


Assuntos
Mapeamento Encefálico/métodos , Eletroencefalografia/estatística & dados numéricos , Vias Visuais/fisiologia , Adolescente , Mapeamento Encefálico/instrumentação , Mapeamento Encefálico/estatística & dados numéricos , Biologia Computacional , Eletrodos , Eletroencefalografia/instrumentação , Feminino , Neuroimagem Funcional/estatística & dados numéricos , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética/estatística & dados numéricos , Masculino , Estimulação Luminosa , Análise Espaço-Temporal , Córtex Visual/fisiologia , Adulto Jovem
9.
Phys Chem Chem Phys ; 23(29): 15719-15726, 2021 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-34279530

RESUMO

Glassy films of cis-methyl formate show spontaneous dipole orientation on deposition from the vacuum, the so-called 'spontelectric effect', creating surface potentials and electric fields within the films. We follow the decay of these fields, and their accompanying dipole orientation, on the hours timescale at deposition temperatures between 40 K and 55 K. Our data trace the low temperature 'secondary decay' mechanism, at tens of degrees below the glass transition temperature of 90 K. We show that secondary decay is due to molecular rotation, with associated activation energies lying between 0.1 and 0.2 eV. Diffusion is absent, as established from published neutron reflectivity data. Using an analytical model for the spontelectric effect, data are placed on a quantitative footing, showing that angular motion in excess of 50° reproduces the observed values of activation energies. Exploitation of the spontelectric effect is new in the study of glass aging and is shown here to give insight into the elusive processes which take place far from the molecular glass transition temperature.

10.
Chem Commun (Camb) ; 57(52): 6368-6371, 2021 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-34105533

RESUMO

Measurements of the decay of electric fields, formed spontaneously within vapour-deposited films of cis-methyl formate, provide the first direct assessment of the energy barrier to secondary relaxation in a molecular glass. At temperatures far below the glass transition temperature, the mechanism of relaxation is shown to be through hindered molecular rotation. Magnetically-polarised neutron scattering experiments exclude diffusion, which is demonstrated to take place only close to the glass transition temperature.

12.
BMC Pediatr ; 21(1): 100, 2021 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-33637074

RESUMO

BACKGROUND: The question of whether to treat patent ductus arteriosus (PDA) early or wait until symptoms appear remains high on the research agenda for neonatal medicine. Around 7000 extremely preterm babies under 29 weeks' gestation are born in the UK every year. In 40% of cases the PDA will fail to close spontaneously, even by 4 months of age. Untreated PDA can be associated with several serious and life-threatening short and long-term complications. Reliable data to support clinical decisions about PDA treatment are needed to prevent serious complications in high risk babies, while minimising undue exposure of infants. With the availability of routine bedside echocardiography, babies with a large PDA can be diagnosed before they become symptomatic. METHODS: This is a multicentre, masked, randomised, placebo-controlled parallel group trial to determine if early-targeted treatment of a large PDA with parenteral ibuprofen in extremely preterm babies (23+ 0-28+ 6 weeks' gestation) improves short and long-term health and economic outcomes. With parental informed consent, extremely preterm babies (born between 23+ 0-28+ 6 weeks' gestation) admitted to tertiary neonatal units are screened using echocardiography. Babies with a large PDA on echocardiography, defined by diameter of at least 1.5 mm and unrestricted pulsatile PDA flow pattern, are randomly allocated to either ibuprofen or placebo within 72 h of birth. The primary endpoint is the composite outcome of death by 36 weeks' postmenstrual age or moderate or severe bronchopulmonary dysplasia (BPD) at 36 weeks postmenstrual age. DISCUSSION: Prophylactic pharmacological treatment of all preterm babies unnecessarily exposes them to potentially serious side effects of drug treatment, when their PDA may have closed spontaneously. However, delaying treatment until babies become symptomatic could result in loss of treatment benefit as irreversible damage may have already been done. Targeted, early pharmacological treatment of PDA in asymptomatic babies has the potential to overcome the disadvantages of both prophylactic (overtreatment) and symptomatic approaches (potentially too late). This could result in improvements in the clinically important short-term clinical (mortality and moderate or severe BPD at 36 weeks' postmenstrual age) and long-term health outcomes (moderate or severe neurodevelopment disability and respiratory morbidity) measured at 2 years corrected age. TRIAL REGISTRATION: ISRCTN84264977 . Date assigned: 15/09/2010.


Assuntos
Displasia Broncopulmonar , Permeabilidade do Canal Arterial , Doenças do Prematuro , Displasia Broncopulmonar/prevenção & controle , Permeabilidade do Canal Arterial/diagnóstico por imagem , Permeabilidade do Canal Arterial/tratamento farmacológico , Humanos , Ibuprofeno/uso terapêutico , Lactente , Recém-Nascido de Baixo Peso , Recém-Nascido , Doenças do Prematuro/tratamento farmacológico , Estudos Multicêntricos como Assunto , Ensaios Clínicos Controlados Aleatórios como Assunto
13.
J Am Coll Radiol ; 18(5): 752-758, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33387455

RESUMO

OBJECTIVES: To determine and compare the relative value of diagnostic radiology resident stipends when adjusted for regional cost of living. METHODS: The ACGME database was queried for a list of accredited allopathic diagnostic radiology residency programs for academic year 2017-2018. Stipend information for R1 positions (post-graduate year 2) was identified through each program's website. Data was grouped and analyzed by city, state, and geographical region. Stipends were then correlated with the 2017 annual region-specific average cost of living index (COLI). RESULTS: There were 194 programs identified, of which 118 (60.8%) were analyzed after exclusions for lack of stipend or corresponding COLI data. The average annual stipend was $57,161±$4,242 (range, $49,547-$72,000). The COLI-adjusted value was $51,357±$9,927 (range, $26,915-$68,827). The average difference between stipend and cost-ofliving adjusted value was -$5,804±$12,610 (range, -$40,953-$10,958), corresponding to an average -9.1% stipend value loss (range, -58.1%-21.7%, P = .00000004). Value loss in large metropolitan cities was as high as 53.8%. DISCUSSION: Financial issues are one of the biggest challenges faced by trainees and have been correlated with increased stress as well as poor academic performance. The pressures of debt can also play a significant role in ultimate subspecialty career choice. Discrepancies between resident stipends, which are not adjusted based on the local COLI, are exacerbated by large regional variations in cost of living. Residency applicants should not discount regional cost of living when deciding where to train, and training programs should consider cost of living when setting stipend levels for their trainees.


Assuntos
Internato e Residência , Radiologia , Escolha da Profissão , Educação de Pós-Graduação em Medicina , Radiologia/educação , Estados Unidos
14.
ChemistryOpen ; 9(10): 983-990, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-33024652

RESUMO

Absorption spectra of vacuum-deposited films of ammonia have been obtained in the range 115 nm to 310 nm for a set of 15 deposition temperatures, Td, between 20 K and 80 K. Results focus upon the region 115 nm to 130 nm in overlapping D, E, F and G←X Rydberg transitions involving Wannier-Mott excitons. We identify two phases of ammonia, showing the solid to be polymorphic. Peak absorption wavelengths in the region of interest are found to shift to the red by 299 cm-1, for Td between 20 K to 50 K, and 1380 cm-1 for Td between 55 K to 80 K. Shifts provide evidence for the presence of spontaneously generated electric fields in these films, of values in excess of 108 V m-1 for Td of 20 K to 50 K to a few times 107 V m-1 for 55 K to 80 K. Results enable us to place a lower limit of 1.58 nm on the size of crystallites in the low temperature regime. This dimension represents 16 unit cells or 64 species, giving a more quantitative description than the nebulous term amorphous, as applied to solid ammonia. We also determine that crystallites formed in the high temperature regime contain, within ±20 %, 1688, 756 and 236 molecules of ammonia, respectively at Td of 65 K, 60 K and 55 K.

15.
J Vasc Interv Radiol ; 31(11): 1740-1744.e9, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33019993

RESUMO

Advances in immunotherapy have changed the landscape of oncology over the past decade. Still, most patients with solid organ tumors do not derive a durable benefit from immunotherapies. How these tumors evade treatment has not been fully elucidated, but several studies are seeking ways to stimulate treatment response in these immunologically quiescent tumors. Of these, the combination of locoregional therapy with immune checkpoint inhibition is of interest to the interventional radiologist. This brief report provides an overview of current trials testing the effectiveness of locoregional therapy in combination with immune checkpoint inhibitors and identifies future research goals.


Assuntos
Antineoplásicos Imunológicos/uso terapêutico , Embolização Terapêutica , Neoplasias/terapia , Antineoplásicos Imunológicos/efeitos adversos , Quimioterapia Adjuvante , Ensaios Clínicos como Assunto , Embolização Terapêutica/efeitos adversos , Embolização Terapêutica/mortalidade , Humanos , Neoplasias/imunologia , Neoplasias/mortalidade , Neoplasias/patologia , Resultado do Tratamento
16.
J Perinat Med ; 49(1): 104-110, 2020 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-32892178

RESUMO

OBJECTIVES: Most studies of inhaled nitric oxide (iNO) for prevention of bronchopulmonary dysplasia (BPD) in premature infants have focused on short-term mortality and morbidity. Our aim was to determine the long-term effects of iNO. METHODS: A 7-year follow-up was undertaken of infants entered into a multicenter, double-blind, randomized, placebo-controlled trial of iNO for prevention of BPD in premature infants born between 24 and 28 weeks plus six days of gestation. At 7 years, survival and hospital admissions since the 2-year follow-up, home oxygen therapy in the past year, therapies used in the previous month and growth assessments were determined. Questionnaires were used to compare general health, well-being, and quality of life. RESULTS: A total of 305 children were assessed. No deaths were reported. Rates of hospitalization for respiratory problems (6.6 vs. 10.5%, iNO and placebo group, respectively) and use of respiratory medications (6.6 vs. 9.2%) were similar. Two patients who received iNO and one who received placebo had received home oxygen therapy. There were no significant differences in any questionnaire-documented health outcomes. CONCLUSIONS: iNO for prevention of BPD in very premature infants with respiratory distress did not result in long-term benefits or adverse long-term sequelae. In the light of current evidence, routine use of iNO cannot be recommended for prevention of BPD in preterm infants.


Assuntos
Broncodilatadores/uso terapêutico , Displasia Broncopulmonar/prevenção & controle , Desenvolvimento Infantil/efeitos dos fármacos , Hospitalização/estatística & dados numéricos , Óxido Nítrico/uso terapêutico , Administração por Inalação , Broncodilatadores/farmacologia , Displasia Broncopulmonar/mortalidade , Criança , Europa (Continente)/epidemiologia , Feminino , Seguimentos , Nível de Saúde , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Masculino , Óxido Nítrico/farmacologia
17.
Philos Trans R Soc Lond B Biol Sci ; 375(1806): 20190544, 2020 08 31.
Artigo em Inglês | MEDLINE | ID: mdl-32654641

RESUMO

Many recent studies have addressed the mechanisms operating during the early stages of speciation, but surprisingly few studies have tested theoretical predictions on the evolution of strong reproductive isolation (RI). To help address this gap, we first undertook a quantitative review of the hybrid zone literature for flowering plants in relation to reproductive barriers. Then, using Populus as an exemplary model group, we analysed genome-wide variation for phylogenetic tree topologies in both early- and late-stage speciation taxa to determine how these patterns may be related to the genomic architecture of RI. Our plant literature survey revealed variation in barrier complexity and an association between barrier number and introgressive gene flow. Focusing on Populus, our genome-wide analysis of tree topologies in speciating poplar taxa points to unusually complex genomic architectures of RI, consistent with earlier genome-wide association studies. These architectures appear to facilitate the 'escape' of introgressed genome segments from polygenic barriers even with strong RI, thus affecting their relationships with recombination rates. Placed within the context of the broader literature, our data illustrate how phylogenomic approaches hold great promise for addressing the evolution and temporary breakdown of RI during late stages of speciation. This article is part of the theme issue 'Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.


Assuntos
Populus/genética , Isolamento Reprodutivo , Filogenia
19.
Animal Model Exp Med ; 3(1): 98-102, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32318666

RESUMO

The most commonly used preclinical models of hepatocellular carcinoma (HCC) are limited for use in testing of intra-arterial therapies such as transarterial chemoembolization and radioembolization. Issues encountered with the more commonly used animal models include dissimilarity in their disease development compared with humans and the size of the vasculature which can make intra-arterial therapy testing difficult or impossible. Here we describe the suitability of the woodchuck HCC model for testing of intra-arterial therapies. We describe the techniques for pre-embolization imaging assessment using CT and MRI, technical tips on performing angiography and embolization, and pathological assessment of treated liver.

20.
Neuroimage ; 213: 116679, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32112961

RESUMO

Retinal image motion is a composite signal that contains information about two behaviourally significant factors: self-motion and the movement of environmental objects. It is thought that the brain separates the two relevant signals, and although multiple brain regions have been identified that respond selectively to the composite optic flow signal, which brain region(s) perform the parsing process remains unknown. Here, we present original evidence that the putative human ventral intraparietal area (pVIP), a region known to receive optic flow signals as well as independent self-motion signals from other sensory modalities, plays a critical role in the parsing process and acts to isolate object-motion. We localised pVIP using its multisensory response profile, and then tested its relative responses to simulated object-motion and self-motion stimuli; results indicated that responses were much stronger in pVIP to stimuli that specified object-motion. We report two further observations that will be significant for the future direction of research in this area; firstly, activation in pVIP was suppressed by distant stationary objects compared to the absence of objects or closer objects. Secondly, we describe several other brain regions that share with pVIP selectivity for visual object-motion over visual self-motion as well as a multisensory response.


Assuntos
Percepção de Movimento/fisiologia , Fluxo Óptico/fisiologia , Lobo Parietal/fisiologia , Adulto , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Adulto Jovem
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