摘要 :
Instabilities play a central role in the physics of foams. Some that change the topology of a dryfoam are indicated by the laws promulgated by Plateau in his 1873 book. Their occurrence is lessclearly predictable in wet foams. Var...
展开
Instabilities play a central role in the physics of foams. Some that change the topology of a dryfoam are indicated by the laws promulgated by Plateau in his 1873 book. Their occurrence is lessclearly predictable in wet foams. Various other instabilities are related to gravitational loadingand gas compressibility. We gather up many examples as a guide to future research and identifyproblems that remain, including what we call pre-emptive instabilities, which occur before they areexpected on the basis of Plateau's laws.
收起
摘要 :
Instabilities play a central role in the physics of foams. Some that change the topology of a dryfoam are indicated by the laws promulgated by Plateau in his 1873 book. Their occurrence is lessclearly predictable in wet foams. Var...
展开
Instabilities play a central role in the physics of foams. Some that change the topology of a dryfoam are indicated by the laws promulgated by Plateau in his 1873 book. Their occurrence is lessclearly predictable in wet foams. Various other instabilities are related to gravitational loadingand gas compressibility. We gather up many examples as a guide to future research and identifyproblems that remain, including what we call pre-emptive instabilities, which occur before they areexpected on the basis of Plateau's laws.
收起
摘要 :
The purpose of this work is to investigate, for the first time, excitation of Faraday waves in small containers using two commensurate frequencies. This spatial restriction, which is encountered at low frequencies, leads to a wave...
展开
The purpose of this work is to investigate, for the first time, excitation of Faraday waves in small containers using two commensurate frequencies. This spatial restriction, which is encountered at low frequencies, leads to a wave composed primarily of one spatial eigenmode of the container. When two frequencies are used, the mode resonates primarily with one frequency, while the role of the second is to alter the instability threshold and the resulting nonlinear dynamics. As the parameter space expands greatly as a result of the introduction of three new degrees of freedom, viz. the frequency, amplitude and phase of the new component, the linear theory is first used as a guide to highlight basic two-frequency phenomena. These predictions and nonlinear phenomena are then studied experimentally with the system of Batson, Zoueshtiagh & Narayanan (J. Fluid Mech., vol. 729, 2013, pp. 496-523), who studied single-frequency excitation of different modes in a cylindrical cell. The two-frequency experiments of this work focus on excitation of the fundamental axisymmetric mode, and are quantitatively compared to the model via a posteriori Fourier decomposition of the parametric input. In doing so, experimental dependence of the instability on the new degrees of freedom is demonstrated, in accordance with the model predictions. This is done for a variety of frequency ratios, and overall agreement between the observed and predicted onset conditions is identical to that already reported for the single-frequency experiment. For each frequency ratio, the nonlinear behaviour is experimentally characterized by bifurcation and time series data, which is shown to differ significantly from comparable single-frequency excitations. Finally, we present and discuss a wave in which both temporal frequencies are used to simultaneously excite different spatial modes.
收起
摘要 :
Background: Pathologic activation pattern of muscles can cause shoulder instability. We propose to call this pathology functional shoulder instability (FSI). The purpose of this prospective study was to provide an in-detail descri...
展开
Background: Pathologic activation pattern of muscles can cause shoulder instability. We propose to call this pathology functional shoulder instability (FSI). The purpose of this prospective study was to provide an in-detail description of the characteristics of FSI.
收起
摘要 :
The absolute/convective character of the linear instability of axisymmetric jets is investigated for a wide range of parallel velocity and density profiles. An adjoint-based sensitivity analysis is carried out in order to maximize...
展开
The absolute/convective character of the linear instability of axisymmetric jets is investigated for a wide range of parallel velocity and density profiles. An adjoint-based sensitivity analysis is carried out in order to maximize the absolute growth rate of jet profiles with and without density variations. It is demonstrated that jets without counterflow may display absolute instability at density ratios well above the previously assumed threshold P_(jet)/P∞ = 0.72, and even in homogeneous settings. Absolute instability is promoted by a strong velocity gradient in the low-velocity region of the shear layer, as well as by a step-like density variation near the location of maximum shear. A new efficient algorithm for the computation of the absolute instability mode is presented.
收起
摘要 :
Carpal instability and distal radioulnar joint instability represent an important set of conditions responsible for pain and disability in the wrist. Either condition can occur as a result of ligamentous failure or loss of articul...
展开
Carpal instability and distal radioulnar joint instability represent an important set of conditions responsible for pain and disability in the wrist. Either condition can occur as a result of ligamentous failure or loss of articular congruity from fractures or a combination of both. Instability itself is a clinical diagnosis supported by relevant imaging modalities. Carpal and distal radioulnar joint instability needs to be considered according to its stage and severity as well as other factors like etiology and chronicity to determine the optimal treatment option. This article summarizes the conditions most relevant to the practice of a hand surgeon, with emphasis divided equally between assessment and diagnosis, staging, and treatment. The 3 most common carpal instability conditions are outlined in this article together with a review on acute and chronic distal radioulnar joint instability.
收起
摘要 :
A liquid drop impacting a solid surface may splash either by emitting a thin liquid sheet that subsequently breaks apart or by promptly ejecting droplets from the advancing liquid-solid contact line. Using high-speed imaging, we s...
展开
A liquid drop impacting a solid surface may splash either by emitting a thin liquid sheet that subsequently breaks apart or by promptly ejecting droplets from the advancing liquid-solid contact line. Using high-speed imaging, we show that surface roughness and air pressure influence both mechanisms. Roughness inhibits thin-sheet formation even though it also increases prompt splashing at the advancing contact line. If the air pressure is lowered, droplet ejection is suppressed not only during thin-sheet formation but also for prompt splashing.
收起
摘要 :
A theoretical study of linear global instability of incompressible flow over a rectangular spanwise-periodic open cavity in an unconfined domain is presented. Comparisons with the limited number of results available in the literat...
展开
A theoretical study of linear global instability of incompressible flow over a rectangular spanwise-periodic open cavity in an unconfined domain is presented. Comparisons with the limited number of results available in the literature are shown. Subsequently, the parameter space is scanned in a systematic manner, varying Reynolds number, incoming boundary-layer thickness and length-to-depth aspect ratio. This permits documenting the neutral curves and leading eigenmode characteristics of this flow. Correlations constructed using the results obtained collapse all available theoretical data on the three-dimensional instabilities.
收起
摘要 :
One prototypical instability in granular flows is the shear-banding instability, in which a uniform granular shear flow breaks into alternating bands of dense and dilute clusters of particles having low and high shear (shear stres...
展开
One prototypical instability in granular flows is the shear-banding instability, in which a uniform granular shear flow breaks into alternating bands of dense and dilute clusters of particles having low and high shear (shear stress or shear rate), respectively. In this work, the shear-banding instability in an arbitrarily inelastic granular shear flow is analyzed through the linear stability analysis of granular hydrodynamic equations closed with Navier-Stokes-level constitutive relations. It is shown that the choice of appropriate constitutive relations plays an important role in predicting the shear-banding instability. A parametric study is carried out to study the effect of the restitution coefficient, channel width, and mean density. Two global criteria relating the control parameters are found for the onset of the shear-banding instability.
收起
摘要 :
Sporadic colorectal cancer (CRC) is a somatic genetic disease in which pathogenesis is influenced by the local colonic environment and the patient's genetic background. Consolidating the knowledge of genetic and epigenetic events ...
展开
Sporadic colorectal cancer (CRC) is a somatic genetic disease in which pathogenesis is influenced by the local colonic environment and the patient's genetic background. Consolidating the knowledge of genetic and epigenetic events that occur with initiation, progression, and metastasis of sporadic CRC has identified some biomarkers that might be utilized to predict behavior and prognosis beyond staging, and inform treatment approaches. Modern next-generation sequencing of sporadic CRCs has confirmed prior identified genetic alterations and has classified new alterations. Each patient's CRC is genetically unique, propelled by 2-8 driver gene alterations that have accumulated within the CRC since initiation. Commonly observed alterations across sporadic CRCs have allowed classification into a (1) hypermutated group that includes defective DNA mismatch repair with microsatellite instability and POLE mutations in similar to 15%, containing multiple frame-shifted genes and BRAF(V600E); (2) nonhypermutated group with multiple somatic copy number alterations and aneuploidy in similar to 85%, containing oncogenic activation of KRAS and PIK3CA and mutation and loss of heterozygosity of tumor suppressor genes, such as APC and TP53; (3) CpG island methylator phenotype CRCs in similar to 20% that overlap greatly with microsatellite instability CRCs and some nonhypermutated CRCs; and (4) elevated microsatellite alterations at selected tetranucleotide repeats in similar to 60% that associates with metastatic behavior in both hypermutated and nonhypermutated groups. Components from these classifications are now used as diagnostic, prognostic, and treatment biomarkers. Additional common biomarkers may come from genome-wide association studies and microRNAs among other sources, as well as from the unique alteration profile of an individual CRC to apply a precision medicine approach to care.
收起
原文获取