Comedones and epidermal cysts on the abdominal skin of a dog occurring after a laparotomy.

An 8-year-old neutered male shih tzu dog underwent laparotomy for cystolithectomy. Ten days later, multiple various-sized cystic nodules were observed on the suture line and surrounding abdominal skin, although the surgical incision had healed well. Microscopically, various-sized cysts lined with thin walls of stratified squamous epithelium in the dermis were dilated and filled with keratin. Adnexal differentiation from the wall was not seen. Thus, the abdominal lesions were diagnosed as comedones and epidermal cysts. Herein, we describe the case of a dog with comedones and epidermal cysts on the abdominal skin after a laparotomy. Key clinical message: Multiple various-sized cystic lesions of the follicles are described. The implantation of epidermal fragments into the dermis by surgery may induce epidermal cysts and comedones in the skin of hyperadrenocorticism-affected dogs.

Comédons et kystes épidermiques sur la peau abdominale d'un chien survenant après une laparotomie. Un chien shih tzu mâle castré de 8 ans a subi une laparotomie pour cystolithectomie. Dix jours plus tard, de multiples nodules kystiques de différentes tailles ont été observés sur la ligne de suture et sur la peau abdominale environnante, bien que l'incision chirurgicale ait bien cicatrisé. Au microscope, des kystes de différentes tailles bordés de fines parois d'épithélium pavimenteux stratifié dans le derme étaient dilatés et remplis de kératine. Aucune différenciation annexielle par rapport à la paroi n'a été observée. Ainsi, les lésions abdominales ont été diagnostiquées comme des comédons et des kystes épidermiques. Nous décrivons ici le cas d'un chien présentant des comédons et des kystes épidermiques sur la peau abdominale après une laparotomie.Message clinique clé:De multiples lésions kystiques des follicules, de différentes tailles, sont décrites. L'implantation chirurgicale de fragments d'épiderme dans le derme peut provoquer des kystes épidermiques et des comédons dans la peau des chiens atteints d'hypercorticisme.(Traduit par Dr Serge Messier).

Development of in-vitro pulsatile flow generator for evaluating the performance of hemodialysis catheters.

Hemodialysis (HD) using an HD catheter is performed widely on renal failure patients. The catheter was evaluated using the recirculation ratio in pre-clinical status, which is a crucial index indicating its performance. However, pre-clinical in-vivo experiments have limitations: high cost, and ethical issues. Hence, computational and in-vitro methods have been developed as alternatives. However, computational methods require fluid dynamic knowledge, whereas in-vitro experiments are complicated and expensive. In this study, we developed a pulsatile flow generator to mimic blood flow achieving cost effectiveness and user convenience. The device used iterative learning control, achieving blood flow in the superior and inferior vena cava within a 3.3% error. Furthermore, the recirculation ratios were measured based on two insertion directions and two different external pipe materials to evaluate the catheter regarding patients' posture and blood vessel stiffness. The results provide a better understanding of cardiovascular device performance without complicated and costly pre-clinical tests.

From shaping to functionalization of micro-droplets and particles.

The structure of microdroplet and microparticle is a critical factor in their functionality, which determines the distribution and sequence of physicochemical reactions. Therefore, the technology of precisely tailoring their shape is requisite for implementing the user demand functions in various applications. This review highlights various methodologies for droplet shaping, classified into passive and active approaches based on whether additional body forces are applied to droplets to manipulate their functions and fabricate them into microparticles. The passive approaches cover batch emulsification, solvent evaporation and diffusion, micromolding, and microfluidic methods. In active approaches, the external forces, such as electrical and magnetic fields or optical lithography, are applied to microdroplets. Special attention is also given to latest technologies using microdroplets and microparticles, especially in the fields of biological, optical, robotic, and environmental applications. Finally, this review aims to address the advantages and disadvantages of the introduced approaches and suggests the direction for further development in this field.

Development of New Hemodialysis Catheter Using Numerical Analysis and Experiments.

A hemodialysis (HD) catheter, especially one with a symmetric tip design, plays an important role in the long-term treatment of patients with renal failure. It is well known that the design of the HD catheter has a considerable effect on blood recirculation and thrombus formation around it, which may cause inefficiencies or malfunctions during HD. However, hemodynamic analyses through parametric studies of its designs have been rarely performed; moreover, only comparisons between the existing models have been reported. In this study, we numerically analyzed the design of the HD catheter's side hole and distal tip for evaluating their effects on hemodynamic factors such as recirculation rate (RR), shear stress, and blood damage index (BDI). The results indicated that a larger side hole and a nozzle-shaped distal tip can significantly reduce the RR and shear stress around the HD catheter. Furthermore, based on these hemodynamic insights, we proposed three new HD catheter designs and compared their performances with existing catheters using numerical and in vitro methods. These new designs exhibited lower RRs and BDI values, thus providing better performance than the existing models. These results can help toward commercialization of more efficient HD catheters.

Electro-Hydrodynamics of Emulsion Droplets: Physical Insights to Applications.

The field of droplet electrohydrodynamics (EHD) emerged with a seminal work of G.I. Taylor in 1966, who presented the so-called leaky dielectric model (LDM) to predict the droplet shapes undergoing distortions under an electric field. Since then, the droplet EHD has evolved in many ways over the next 55 years with numerous intriguing phenomena reported, such as tip and equatorial streaming, Quincke rotation, double droplet breakup modes, particle assemblies at the emulsion interface, and many more. These phenomena have a potential of vast applications in different areas of science and technology. This paper presents a review of prominent droplet EHD studies pertaining to the essential physical insight of various EHD phenomena. Here, we discuss the dynamics of a single-phase emulsion droplet under weak and strong electric fields. Moreover, the effect of the presence of particles and surfactants at the emulsion interface is covered in detail. Furthermore, the EHD of multi-phase double emulsion droplet is included. We focus on features such as deformation, instabilities, and breakups under varying electrical and physical properties. At the end of the review, we also discuss the potential applications of droplet EHD and various challenges with their future perspectives.

Deformation of Emulsion Droplet with Clean and Particle-Covered Interface under an Electric Field.

The electrohydrodynamic deformation of an emulsion droplet with a clean and particle-covered interface was explored. Here, the electrohydrodynamic deformation was numerically and experimentally demonstrated under the stimuli of moderate and strong electric fields. The numerical method involves the coupling of the Navier-Stokes equation with the level set equation of interface tracking and the governing equations of so-called leaky dielectric theory. The simulation model developed for a clean interface droplet was then extended to a capsule model for densely particle-covered droplets. The experiments were conducted using various combinations of immiscible oils and particle suspensions while the electric field strength ~105 V/m was generated using a high voltage supply. The experimental images obtained by the camera were post-processed using an in-house image processing code developed on the plat-form of MATLAB software. The results show that particle-free droplets can undergo prolate (deformation in the applied electric field direction) or oblate deformation (deformation that is perpendicular to the direction of the applied electric field) of the droplet interface, whereas the low-conductivity particles can be manipulated at the emulsion interface to form a 'belt', 'helmet' or 'cup' morphologies. A densely particle-covered droplet may not restore to its initial spherical shape due to 'particle jamming' at the interface, resulting in the formation of unique droplet shapes. Densely particle-covered droplets behave like droplets covered with a thin particle sheet, a capsule. The deformation of such droplets is explored using a simulation model under a range of electric capillary numbers (i.e., the ratio of the electric stresses to the capillary stresses acting at the droplet interface). The results obtained are then compared with the theory and experimental findings. It was shown that the proposed simulation model can serve as a tool to predict the deformation/distortion of both the particle-free and the densely particle-covered droplets within the small deformation limit. We believe that this study could provide new findings for the fabrication of complex-shaped species and colloidosomes.