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"Mansoor, Mohammad"
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Water entry of spheres with various contact angles
It is well known that the water entry of a sphere causes cavity formation above a critical impact velocity as a function of the solid–liquid contact angle; Duez et al. (Nat. Phys., vol. 3 (3), 2007, pp. 180–183). Using a rough sphere with a contact angle of
$120^{\\circ }$
, Aristoff & Bush (J. Fluid Mech., vol. 619, 2009, pp. 45–78) showed that there are four different cavity shapes dependent on the Bond and Weber numbers (i.e., quasistatic, shallow, deep and surface). We experimentally alter the Bond number, Weber number and contact angle of smooth spheres and find two key additions to the literature: (1) cavity shape also depends on the contact angle; (2) the absence of a splash crown at low Weber number results in cavity formation below the predicted critical velocity. In addition, we use alternate scales in defining the Bond, Weber and Froude numbers to predict the cavity shapes and scale pinch-off times for various impacting bodies (e.g., spheres, multidroplet streams and jets) on the same plots, merging the often separated studies of solid–liquid and liquid–liquid impact in the literature.
Journal Article
Gelatine cavity dynamics of high-speed sphere impact
We investigate the impact and penetration of a solid sphere passing through gelatine at various impact speeds up to$143.2~\\text{m}~\\text{s}^{-1}$. Tests were performed with several concentrations of gelatine. Impacts for low elastic Froude number$\\mathit{Fr}_{e}$, a ratio between inertia and gelatine elasticity, resulted in rebound. Higher$\\mathit{Fr}_{e}$values resulted in penetration, forming cavities with prominent surface textures. The overall shape of the cavities resembles those observed in water-entry experiments, yet they appear in a different order with respect to increasing inertia: rebound, quasi-seal, deep-seal, shallow-seal and surface-seal. Remarkably, similar to the$We$–$Bo$phase diagram in water-entry experiments, the elastic Froude number$\\mathit{Fr}_{e}$and elastic Grashof number$\\mathit{Gr}_{e}$(a ratio between gravity and gelatine elasticity) classify all five different phenomena into distinguishable regimes. We find that$\\mathit{Fr}_{e}$can be a good indicator to describe the cavity length$H$, particularly in the shallow-seal regime. Finally, the evolution of cavity shape, pinch-off depth, and lower cavity radius are investigated for different$\\mathit{Fr}_{e}$values.
Journal Article
Prosthetic rehabilitation with fixed prosthesis of a 5-year-old child with Hypohidrotic Ectodermal Dysplasia and Oligodontia: a case report
Background
Ectodermal dysplasia is a rare genetic disorder that affects ectodermally derived structures, including teeth, nails, hair, and sweat glands. Hypohidrotic ectodermal dysplasia is the most common type, with oligodontia being the most striking dental feature. Prosthetic rehabilitation in children with ectodermal dysplasia is an important step toward improving their overall quality of life. The fixed prosthesis has the advantages of being more stable in the mouth with good child compliance and a good aesthetic outcome.
Case presentation
Our patient was a 5-year-old Middle Eastern boy with oligodontia caused by ectodermal dysplasia. He was managed by fabrication of an upper functional space maintainer and a lower fixed partial denture to restore occlusion, masticatory function, aesthetics, and overall quality of life.
Conclusions
The use of the fixed prosthesis in children is a new and evolving treatment modality that resolves many of the issues caused by removable prostheses. It accommodates jaw growth in the mandible, reduces the need to remake the prosthesis, and has an overall better aesthetic outcome.
Journal Article
Astrocyte Heterogeneity in Multiple Sclerosis: Current Understanding and Technical Challenges
The emergence of single cell technologies provides the opportunity to characterize complex immune/central nervous system cell assemblies in multiple sclerosis (MS) and to study their cell population structures, network activation and dynamics at unprecedented depths. In this review, we summarize the current knowledge of astrocyte subpopulations in MS tissue and discuss the challenges associated with resolving astrocyte heterogeneity with single-nucleus RNA-sequencing (snRNA-seq). We further discuss multiplexed imaging techniques as tools for defining population clusters within a spatial context. Finally, we will provide an outlook on how these technologies may aid in answering unresolved questions in MS, such as the glial phenotypes that drive MS progression and/or neuropathological differences between different clinical MS subtypes.
Journal Article
Bioactivities of the Green Synthesized Silver Nanoparticles Reduced Using Allium cepa L Aqueous Extracts Induced Apoptosis in Colorectal Cancer Cell Lines
Allium cepa L (A. cepa) extract is frequently used as an adjuvant food in cancer treatment. We hypothesized that it contains a source of anticancer activity. There is a need to synthesize the silver nanoparticles (AgNPs) using an environment-friendly green synthesis reduction method using an aqueous extract of A. cepa. The AgNPs-CEPA were prepared by reduction method using the aqueous extract of A. cepa. The formed AgNPs-CEPA were characterized for their sizes and charge distribution. The AgNP-CEPA was investigated for its antioxidant and anticancer properties. Cell viability was evaluated by MTT assay. Gene expression was evaluated by real-time polymerase chain reaction (RT-PCR), and apoptosis measurement was carried out by flow cytometry in AgNP-CEPA-treated cells. The results showed a uniform size for AgNPs-CEPA of 155±2.1 nm with a zeta potential of −37.3±−2.92 mv. The produced AgNPs-CEPA are biocompatible with anticancer action and a moderate level of antioxidant reactivity. AgNPs-CEPA showed better reducing activity for A. cepa extract compared to the AgNPs-CEPA. AgNP-CEPA treatment of human colorectal cancer cell lines (HT-29 and SW620) inhibited cell proliferation and altered Bcl2 family gene expression. Moreover, exposure of cell lines to AgNPs-CEPA resulted in the significant induction of apoptosis compared to A. cepa and AgNO3. These findings indicate that AgNP-CEPA induces apoptosis by inhibiting Bcl2 family gene expression, suggesting that this formula is a promising anticancer agent for treating colorectal cancer.
Journal Article
From Prostate Enlargement to Bladder Stone: Large Bladder Stone as a Complication of Long‐Standing BPH: A Case Study
Vesicular calculi, or bladder stones, are a common occurrence in males of older age. Although there is a variety of different etiologies reported, one of the less common ones includes a background of benign prostatic hyperplasia (BPH). This case report describes a rare presentation of a large vesicular calculus in an old male patient that was diagnosed along with BPH. The patient, with a history of alcohol abuse and hypertension, previously had a percutaneous nephrolithotomy. Diagnosis was confirmed through transrectal ultrasound, x‐ray Kidney–Ureter‐Bladder, and cystourethroscopy. He underwent transurethral resection of prostate and open vesicolithotomy, with a smooth recovery. This case highlights the pathophysiological and urodynamical relationship between bladder stones formation and BPH, and explores other factors in stone formation.
Journal Article
The effect of initial conditions on mixing transition of the Richtmyer–Meshkov instability
We investigate the late-time Richtmyer–Meshkov instability (RMI) growth of sinuous perturbations on an air/sulphur hexafluoride interface (Atwood number, $A \\sim 0.67$) subjected to a Mach 1.2 planar shock wave at Los Alamos National Laboratory's vertical shock tube facility. Interface perturbations are established using a novel membraneless technique where cross-flowing air and SF$_6$ separated by an oscillating splitter plate create a perturbed density interface. The interface formed has multi-modal features and residual small perturbations, however, a dominant mode is still noticeable. The late-time perturbation growths scale with $ka_0$ initial conditions (where $k$ is the wavenumber and $a_0$ is the initial amplitude of the dominant mode) as measured at the pre-shock interface. Past nonlinear models based on potential-flow theory, heuristic/interpolation approaches, Padé approximants and numerical simulations are evaluated against present experimental results. Accounting for an explicit $ka_0$ dependence in Sadot et al.'s (Phys. Rev. Lett., vol. 80, issue 8, 1998, pp. 1654–1657) model, we propose an empirical rational function that captures the asymptotic behaviour of perturbation growth for a broad range of initial conditions ($0.30 \\leq ka_0 \\leq 0.86$). The onset of mixing transition and its initial condition dependence are investigated with respect to the minimum state criterion ($Re = 1.6 \\times 10^5$) for unsteady flows by Zhou (Phys. Plasmas, vol. 14, 2007, 082701). Earlier mixing transitions for higher $ka_0$ initial conditions are noted from local and global Reynolds number estimates which are corroborated by the existence of an inertial sub-range and formation of mixing regions indicating the physical significance of the minimum state criterion in RMI flows. The transition is accompanied by the increasing teapot-like appearance of joint probability density functions of $p$–$q$ (invariants of the reduced velocity gradient tensor), establishing the technique as a useful tool for turbulence detection in two-dimensional diagnostics.
Journal Article
DEMOCRATIC ELECTIONS IN AFGHANISTAN INSTITUTIONAL FLAWS AND SECURITY CHALLENGES
Election is considered as the main pillar of democratic regime, though not the only one. Transparency as well as impartiality of electoral institutions for holding an inclusive election is important for evolution of democracy. Impartiality of electoral institutions, transparency, and inclusiveness are the main ingredients which brings changes to democratic test of any political society. However, politicization of electoral institutions and to hold election for gaining political legitimacy may lead towards democratic disaster, political instability and ultimately may lead to totalitarianism. As in case of Afghanistan, there have never been independent electoral institutions. The electoral institutions have been under immense influence of executive - political elites in power, as well as local forces including warlords, chief of tribes,ethnic and religious leaders and more or less the international donors. The permanence of electoral officials depends on their loyalty to political elites at the center of power. The performance of electoral authorities is driven by their ethnic and political affiliation than the rules and regulations under the constitution of Afghanistan and election law. This article evaluates the process of presidential and parliamentary elections in Afghanistan during post-Taliban era and explains the historical, social and political reasonsfor the dysfunctionality of the electoral institutions to act as independent, impartial and transparent establishment in Afghanistan.
Journal Article