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1.
Philos Trans A Math Phys Eng Sci ; 379(2189): 20200224, 2021 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-33280567

RESUMO

Indirect drive inertial confinement fusion experiments with convergence ratios below 17 have been previously shown to be less susceptible to Rayleigh-Taylor hydrodynamic instabilities, making this regime highly interesting for fusion science. Additional limitations imposed on the implosion velocity, in-flight aspect ratio and applied laser power aim to further reduce instability growth, resulting in a new regime where performance can be well represented by one-dimensional (1D) hydrodynamic simulations. A simulation campaign was performed using the 1D radiation-hydrodynamics code HYADES to investigate the performance that could be achieved using direct-drive implosions of liquid layer capsules, over a range of relevant energies. Results include potential gains of 0.19 on LMJ-scale systems and 0.75 on NIF-scale systems, and a reactor-level gain of 54 for an 8.5 MJ implosion. While the use of 1D simulations limits the accuracy of these results, they indicate a sufficiently high level of performance to warrant further investigations and verification of this new low-instability regime. This potentially suggests an attractive new approach to fusion energy. This article is part of a discussion meeting issue 'Prospects for high gain inertial fusion energy (part 2)'.

2.
Brain Behav Evol ; 95(3-4): 139-161, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33171468

RESUMO

The volume of the olfactory bulbs (OBs) relative to the brain has been used previously as a proxy for olfactory capabilities in many vertebrate taxa, including fishes. Although this gross approach has predictive power, a more accurate assessment of the number of afferent olfactory inputs and the convergence of this information at the level of the telencephalon is critical to our understanding of the role of olfaction in the behaviour of fishes. In this study, we used transmission electron microscopy to assess the number of first-order axons within the olfactory nerve (ON) and the number of second-order axons in the olfactory peduncle (OP) in established model species within cartilaginous (brownbanded bamboo shark, Chiloscyllium punctatum [CP]) and bony (common goldfish, Carassius auratus [CA]) fishes. The total number of axons varied from a mean of 18.12 ± 7.50 million in the ON to a mean of 0.38 ± 0.21 million in the OP of CP, versus 0.48 ± 0.16 million in the ON and 0.09 ± 0.02 million in the OP of CA. This resulted in a convergence ratio of approximately 50:1 and 5:1, respectively, for these two species. Based on astroglial ensheathing, axon type (unmyelinated [UM] and myelinated [M]) and axon size, we found no differentiated tracts in the OP of CP, whereas a lateral and a medial tract (both of which could be subdivided into two bundles or areas) were identified for CA, as previously described. Linear regression analyses revealed significant differences not only in axon density between species and locations (nerves and peduncles), but also in axon type and axon diameter (p < 0.05). However, UM axon diameter was larger in the OPs than in the nerve in both species (p = 0.005), with no significant differences in UM axon diameter in the ON (p = 0.06) between species. This study provides an in-depth analysis of the neuroanatomical organisation of the ascending olfactory pathway in two fish taxa and a quantitative anatomical comparison of the summation of olfactory information. Our results support the assertion that relative OB volume is a good indicator of the level of olfactory input and thereby a proxy for olfactory capabilities.


Assuntos
Axônios/ultraestrutura , Carpa Dourada/anatomia & histologia , Bulbo Olfatório/citologia , Nervo Olfatório/citologia , Condutos Olfatórios/citologia , Tubarões/anatomia & histologia , Animais , Microscopia Eletrônica de Transmissão , Bulbo Olfatório/ultraestrutura , Córtex Olfatório/citologia , Nervo Olfatório/ultraestrutura , Condutos Olfatórios/ultraestrutura
3.
Micromachines (Basel) ; 13(8)2022 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-35893157

RESUMO

The continuous phase plate (CPP) provides excellent beam smoothing and shaping impacts in the inertial confinement fusion application. However, due to the features of its dispersion, its surface gradient is frequently too large (>2 µm/cm) to process. When machining a large gradient surface with continuous ion beam figuring (IBF), the acceleration of the machine motion axis cannot fulfill the appropriate requirements, and the machining efficiency is further influenced by the unavoidable extra removal layer. The pulsed ion beam (PIB) discretizes the ion beam by incorporating frequency-domain parameters, resulting in a pulsed beam with a controlled pulse width and frequency and avoiding the extra removal layer. This research evaluates the processing convergence ability of IBF and PIB for the large gradient surface using simulation and experiment. The findings reveal that PIB offers obvious advantages under the same beam diameter. Compared with the convergence ratio (γ = 2.02) and residuals (RMS = 184.36 nm) of IBF, the residuals (RMS = 27.48 nm) of PIB are smaller, and the convergence ratio (γ = 8.47) is higher. This work demonstrates that PIB has better residual convergence in large gradient surface processing. It is expected to realize ion beam machining with a higher convergence ratio.

4.
Rom J Ophthalmol ; 65(4): 362-364, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-35087977

RESUMO

Aim: To determine if there is a difference at all in proximal convergence to accommodation ratio (PC/ A) between 2 myopic groups. Group A: -0.50D < SE < 3.00D, SE: spherical equivalent, D: Diopter) and Group B (-3.00D SE and above). Patients and methods: In this prospective observational study, 24 consecutive patients with myopia between -0.50D < SE < 3.00D were included in group A and 27 consecutive patients with myopia > -3.00 D SE were included in group B. Patients with pathological myopia, strabismus or heterophoria anomalies were excluded. The PC/ A ratio for both the groups were calculated by measuring the difference between value of accommodative convergence to accommodation ratio (AC/ A) derived from heterophoria and gradient method using a prism bar method. Statistical analysis was performed by analyzing descriptive statistics and the independent sample t-test using SPSS ver. 22.0 software. Results: The average calculated PC/ A ratio was 3.24∆/ D (SD = +0.68/ D) in group B (n=27) and 2.6∆/ D (SD = 0.86/ D) in group A (n=24) (p value <0.05). Conclusion: An evident high AC/ A ratio in group B patients with myopia more than -3.00 D was the predominant cause for high PC/ A ratio in group B patients.


Assuntos
Miopia Degenerativa , Estrabismo , Acomodação Ocular , Humanos , Estudos Prospectivos , Refração Ocular
5.
Front Neuroanat ; 14: 50, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33192338

RESUMO

Certain sensory receptors contain many transducers, converging onto few afferents. Convergence creates star-topology neural networks, of iterative parallel organization, that may yield special functional properties. We quantitated large-scale convergence in electroreceptors on the rostrum of preadult paddlefish, Polyodon spathula (Acipenseriforme vertebrates), and analyzed the afferent terminal branching underlying the convergence. From neurophysiological mapping, a recorded afferent innervated 23.3 ± 9.1 (range 6-45) ampullary organs, and innervated every ampullary organ within the receptive field's sharp boundary. Ampullary organs each contained ∼665 Lorenzinian receptor cells, from imaging and modeling. We imaged three serial types of afferent branching at electroreceptors, after immunofluorescent labeling for neurite filaments, glial sheaths, or nodal ion channels, or by DiI tracing. (i) Myelinated tree: Each of 3.08 ± 0.51 (2-4) parallel afferents from a cranial nerve (ALLn) entered a receptive field from deeper tissue, then branched into a laminar tree of large myelinated dendrites, parallel to the skin, that branched radially until ∼9 extremities with heminodes, which were candidate sites of spike encoders. (ii) Inline transition: Each myelinated extremity led distally into local unmyelinated arbors originating at inline branching structures covered by terminal (satellite) glia. The unmyelinated transition zones included globular afferent modules, 4-6 microns wide, from which erupted fine fascicles of parallel submicron neurites, a possibly novel type of neuronal branching. The neurite fascicles formed loose bundles projecting ∼105 microns distally to innervate local groups of ∼3 adjacent ampullary organs. (iii) Radial arbors: Receptor cells in an electrosensory neuroepithelium covering the basal pole of each ampullary organ were innervated by bouton endings of radial neurites, unmyelinated and submicron, forming a thin curviplanar lamina distal to the lectin+ basal lamina. The profuse radial neurites diverged from thicker (∼2 micron) basolateral trunks. Overall, an average Polyodon electroreceptor formed a star topology array of ∼9 sensor groups. Total convergence ratios were 15,495 ± 6,052 parallel receptor cells per afferent per mean receptive field, assuming 100% innervation. Large-scale convergence likely increases the signal-to-noise ratio (SNR) of stimulus encoding into spiking afferent output, increasing receiver sensitivity. Unmyelinated arbors may also regenerate and repair the afferent innervation of ampullary organs. LSID: urn:lsid:zoobank.org:act:09BCF04C-3C3C-4B6C-9DC9-A2BF43087369.

6.
Ann Otol Rhinol Laryngol ; 127(12): 937-945, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30295066

RESUMO

OBJECTIVES:: The aims of this study were to compare nondysphonic adult and pediatric voices using linear and nonlinear acoustic parameters and to evaluate the ability of adult spectrum convergence ratio (SCR) and rate of divergence (ROD) reference values to correctly identify a pediatric voice type as periodic or aperiodic. METHODS:: Twenty adult and 36 pediatric nondysphonic voice samples were collected and analyzed using linear and nonlinear acoustic parameters. Absence of voice disorder was confirmed using perceptual acoustic and spectral analysis. Mean values for jitter, shimmer, SCR, and ROD were compared between adults and children, across specific age groups, and within genders. Using adult reference values for SCR and ROD, samples were classified as primarily periodic or aperiodic and typed using spectral analysis. Rates of accurate typing were also compared between subject groups. RESULTS:: Overall, jitter and shimmer were similar among the adult and pediatric age groups. ROD was significantly different among the 3 pediatric and 1 adult group; the pediatric age groups were similar to one another. Adult SCR was also significantly different from all of the pediatric age groups. In adult men, ROD and SCR were significantly different from all of the pediatric age groups; the pediatric age groups were similar to one another. In female subjects, ROD was significantly different among all age groups. The ROD and SCR reference values were significantly better at categorizing adult voice types compared with pediatric voice types. CONCLUSIONS:: In healthy subjects, SCR and ROD have discriminatory power for identifying adult versus pediatric voices, while jitter and shimmer cannot differentiate between the 2 groups. However, age- and gender-specific pediatric reference values must be determined to accurately classify voice types using SCR and ROD.


Assuntos
Acústica da Fala , Qualidade da Voz/fisiologia , Adulto , Fatores Etários , Criança , Precisão da Medição Dimensional , Feminino , Voluntários Saudáveis , Humanos , Masculino , Dinâmica não Linear , Valores de Referência , Fatores Sexuais
7.
J Voice ; 30(6): 664-669, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26474718

RESUMO

OBJECTIVES: Currently, there are no objective measures capable of distinguishing between all four voice signal types proposed by Titze in 1995 and updated by Sprecher in 2010. We propose an objective metric that distinguishes between voice signal types based on the aperiodicity present in a signal. STUDY DESIGN: One hundred fifty voice signal samples were randomly selected from the Disordered Voice Database and subjectively sorted into the appropriate voice signal category on the basis of the classification scheme presented in Sprecher 2010. METHODS: Short-time Fourier transform was applied to each voice sample to produce a spectrum for each signal. The spectrum of each signal was divided into 250 time segments. Next, these segments were compared to each other and used to calculate an outcome named spectrum convergence ratio (SCR). Finally, the mean SCR was calculated for each of the four voice signal types. RESULTS: SCR was capable of significantly differentiating between each of the four voice signal types (P < 0.001). Additionally, this new parameter proved equally as effective at distinguishing between voice signal types as currently available parameters. CONCLUSION: SCR was capable of objectively distinguishing between all four voice signal types. This metric could be used by clinicians to quickly and efficiently diagnose voice disorders and monitor improvements in voice acoustical signals during treatment methods.


Assuntos
Acústica , Processamento de Sinais Assistido por Computador , Acústica da Fala , Medida da Produção da Fala/métodos , Distúrbios da Voz/diagnóstico , Qualidade da Voz , Análise de Variância , Bases de Dados Factuais , Análise de Fourier , Humanos , Valor Preditivo dos Testes , Espectrografia do Som , Fatores de Tempo , Distúrbios da Voz/fisiopatologia , Distúrbios da Voz/terapia
8.
Strabismus ; 22(3): 120-4, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25027358

RESUMO

AIM: To determine whether the convergence accommodation to convergence (CA/C) ratio during divergence with base-in (BI) prisms is of a similar or different magnitude to that measured during convergence with base-out (BO) prisms. METHODS: Eighteen participants with normal binocular single vision were recruited. The participants viewed a pseudo-Gaussian target, which consisted of a light emitting diode (LED) behind a diffusing screen at 40 cm. After 5 minutes of dark adaptation, the refractive status of the eye was measured without any prism using a Shin-Nippon SRW-5000 autorefractor. The participant held the selected prism (5Δ or 10Δ BO or BI, counterbalanced) in front of their right eye and obtained a single, fused image of the target while refractive measures were taken with each. A 30-second rest period was given between measurements. The mean age of the participants was 20.6±3.22 years. RESULTS: The mean CA/C ratios for the 5Δ BO, 10Δ BO, 5Δ BI, and 10Δ BI were 0.108 (±0.074) D/Δ, 0.110 (±0.056) D/Δ, 0.100 (±0.090) D/Δ, and 0.089 (±0.055) D/Δ, respectively. A 2-factor repeated measures ANOVA found that the CA/C ratio did not significantly change with differing levels of prism-induced convergence and divergence (p=0.649). CONCLUSIONS: Change in accommodation induced by manipulating vergence is similar whether convergence or divergence are induced. The CA/C ratio did not show any change with differing levels of prism-induced convergence and divergence.


Assuntos
Acomodação Ocular/fisiologia , Convergência Ocular/fisiologia , Transtornos da Motilidade Ocular/fisiopatologia , Visão Binocular/fisiologia , Adolescente , Adulto , Feminino , Humanos , Masculino , Adulto Jovem
9.
Korean Journal of Anatomy ; : 171-177, 2009.
Artigo em Coreano | WPRIM | ID: wpr-647040

RESUMO

The developmental changes of convergence ratios of medial nucleus of trapezoid body (MNTB) axons to single lateral superior olive (LSO) neuron were investigated using voltage clamp technique in homologous (cir/cir) circling mice, animal model for the congenital deafness with autosomal recessive inheritance. As the developmental reduction of convergence ratio reported in rats indicates the presence of synaptic refinement, we aimed to find out whether the similar reduction of convergence ratio also occurs in circling mice. Heterologous (+/cir) mice were used as control and mice younger than postnatal (P) day 4 or older than P9 were used. The convergence ratios of MNTB axons to single LSO neuron were 29.16+/-2.7 (n=12, P9) in homologous (cir/cir) mice, while they were 37.89+/-3.8 (n=9, P9) in heterozygous (+/cir) mice. The significant changes were observed only in heterozygous (+/cir) mice, which indicated that synaptic refinement of MNTBLSO synapses occurs in heterozygous (+/cir) mice, not in homozygous (cir/cir) mice. Considering homologous (cir/cir) mice being animal model for the congenital deafness, our data might contribute to the understanding of developmental changes of brain stem auditory circuits of congenitally deaf patients.


Assuntos
Animais , Humanos , Camundongos , Ratos , Axônios , Tronco Encefálico , Surdez , Modelos Animais , Neurônios , Olea , Sinapses , Testamentos
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