Obstructed and channelized viscoplastic flow in a Hele-Shaw cell

A theoretical study is presented of the flow of viscoplastic fluid through a Hele-Shaw cell that contains various kinds of obstructions. Circular and elliptical blockages of the cell are considered together with stepwise contractions or expansions in slot width, all within the simplifying approximation of a narrow gap. Specific attention is paid to the flow patterns that develop around the obstacles, particularly any stagnant plugged regions, and the asymptotic limits of relatively small or large yield stress. Periodic arrays of circular contractions or expansions are studied to explore the interference between obstructions. Finally, viscoplastic flow through a cell with randomly roughened walls is examined, and it is shown that constructive interference of local contractions and expansions leads to a pronounced channelization of the flow. An optimization algorithm based on minimization of the pressure drop is derived to construct the path of the channels in the limit of relatively large yield stress or, equivalently, relatively slow flow.D.R.H. is grateful to the Killam Foundation for a Postdoctoral Fellowship.This is the author accepted manuscript. The final version is available from Cambridge University Press via http://dx.doi.org/10.1017/jfm.2016.

Obstructed and channelized viscoplastic flow in a Hele-Shaw cell

A theoretical study is presented of the flow of viscoplastic fluid through a Hele-Shaw cell that contains various kinds of obstructions. Circular and elliptical blockages of the cell are considered together with stepwise contractions or expansions in slot width, all within the simplifying approximation of a narrow gap. Specific attention is paid to the flow patterns that develop around the obstacles, particularly any stagnant plugged regions, and the asymptotic limits of relatively small or large yield stress. Periodic arrays of circular contractions or expansions are studied to explore the interference between obstructions. Finally, viscoplastic flow through a cell with randomly roughened walls is examined, and it is shown that constructive interference of local contractions and expansions leads to a pronounced channelization of the flow. An optimization algorithm based on minimization of the pressure drop is derived to construct the path of the channels in the limit of relatively large yield stress or, equivalently, relatively slow flow.D.R.H. is grateful to the Killam Foundation for a Postdoctoral Fellowship.This is the author accepted manuscript. The final version is available from Cambridge University Press via http://dx.doi.org/10.1017/jfm.2016.

Obstructed viscoplastic flow in a Hele–Shaw cell

Experiments are conducted exploring the flow of Carbopol past obstacles in a narrow slot and compared with predictions of a model based on the Herschel-Bulkley constitutive law and the conventional Hele-Shaw approximation. Although Carbopol is often assumed to be a relatively simple yield-stress fluid, the flow pattern around an obstacle markedly lacks the fore-aft symmetry expected theoretically. Such asymmetry has been observed previously for viscoplastic flows past obstacles in unconfined geometries, but the narrowness of the Hele-Shaw cell ensures that the stress state is very different, placing further constraints on the underlying origin. The asymmetry is robust, as demonstrated by varying the shape and number of the obstacles, the surfaces of the cell walls, and the steadiness of the flow rate. The results suggest that rheological hysteresis near the yield point may be the cause of the asymmetry

Effect of noise pollution on testicular tissue and hormonal assessment in rat

Many studies have focused on the effect of noise stress on the health. So far, few studies have been conducted on the effect of noise on reproductive system. The aim of study was to investigate the effect of noise pollution on morphometric parameters of testicular tissue and hormonal assessment (ACTH, cortisol and testosterone). In this study, 40 male rats were exposed to control, 95, 105 and 115 dB noise intensity for sixty days. At the end of study, blood sampling was performed and ACTH, cortisol and testosterone concentrations were assessed. The results showed that noise stress decreased testosterone levels in the 115 dB-treated group, while it increased the ACTH and cortisol levels. Histological sections of testis showed that the mean diameter of the seminiferous tubules and thickness of the germinal epithelium reduced compared to the control group. Also the ratio of the interstitial tissue area to the total testicular tissue area was increased significantly. Our study shows that noise stress may have negative influences on male fertility

Report of an unusual cause of rhinolithiasis: An 'opioma'

We report an unusual case of unilateral rhinolith. The patient was a 21-year-old man who had a history of left-sided nasal obstruction and recurrent bouts of fetid, purulent rhinorrhea of several years' duration. The rhinolith, which had formed around an impacted foreign body, was extracted in several pieces under local anesthesia. Laboratory evaluation revealed that the foreign body was a hardened mixture of codeine and opium wrapped in a small sheet of nylon - what we called an "opioma."

Cochlear implantation in children with Waardenburg syndrome

Waardenburg syndrome is an autosomal-dominant trait resulting from mutations occurring in different genes. It is often characterized by varying degrees of: congenital hearing loss; dystopia canthorum; synophrys; broad nasal root; depigmentation of hair (white forelock), skin or both; and heterochromic or hypochromic irides. A retrospective case study was done to assess speech perception, speech production, general intelligence and educational setting in six profoundly hearing-impaired children with Waardenburg syndrome (four with type I, one with type II and one with type III) ranging in age from two years to 14 years, seven months (mean = six years, six months). None of the patients had malformation of the cochlea and were implanted using Nucleus 22/24 and Med-el combi40+. Five out of the six cases were of average intelligence and one had a borderline intelligence quotient. The follow-up period ranged from one year, 10 months to six years, six months (mean = three years, six months) after implantation. The evaluation of auditory perception in patients was accomplished using the Persian Auditory Perception Test for the Hearing-Impaired, a Persian Spondee words test and the Categories of Auditory Performance Index. The Speech Intelligibility Rating test was used to evaluate speech production ability. All the patients' speech perception and speech intelligibility capabilities improved considerably after receiving the implants, and they were able to be placed in regular educational settings. Patients used their cochlear-implant devices whenever awake, implying that they benefitted from the devices. We suggest that any further expansion of cochlear-implantation criteria in children include those with Waardenburg syndrome

Auditory electrical tinnitus suppression in patients with and without implants

The aim of this study was to evaluate the effectiveness of electrical tinnitus suppression in two groups of chronic severe tinnitus sufferers. Through standard tinnitus questionnaires, we compared the effectiveness of extratympanic and intratympanic auditory electrical stimulation (AES) by cochlear implants (CI) for the suppression or abolition of the perception of tinnitus and the decrease of its associated complaints. We made otolaryngological and comprehensive audiological assessment and also tinnitus measurement in each group of patients before and after AES and 50 days later. We investigated the dimensions of psychological complaints due to chronic and disabling tinnitus by means of the tinnitus questionnaire (TQ). The control examination during at least seven sessions (50 days) after AES in the group of patients without implants showed improvement in 20 of 32 patients (62.5); 12 (37.5) did not notice any change. In the comparative group of patients with implants, improvement occurred in 16 of 20 patients (75); during the switch-on of the speech processor, these patients reported significant attenuation or complete suppression of their tinnitus. Complete suppression of the tinnitus after CI was observed for 11 patients (55), and 5 patients (25) demonstrated significant attenuation of tinnitus. Nonsuppression of tinnitus was observed for only 4 patients (25). None of our patients was affected by an increment in the tinnitus owing to CI. The differences of means of scores in the standard TQ were significant in both groups of patients. A comparison of TQ score differences between patients with and without implants showed no significance. We concluded that AES is a useful and effective therapeutic intervention in patients with tinnitus. Extratympanic AES reduces the effects of the tinnitus but presents limitations, mainly owing to the short duration of the electrical residual inhibition of the tinnitus. CI is shown to be more efficient for the treatment of tinnitus, mainly because the electrical stimulation affects a wider area of the cochlea and is presented for longer sessions. Therefore, patients affected by incapacitating tinnitus should be considered for continuous use of electrical stimulation

The potential role of auditory prediction error in decompensated tinnitus: An auditory mismatch negativity study

Introduction: Some tinnitus subjects habituate to their tinnitus but some others do not and complain of its annoyance tremendously. Normal sensory memory and change detection processes are needed for detecting the tinnitus signal as a prediction error and habituation to tinnitus. The purpose of this study was to compare auditory mismatch negativity as the index of sensory memory and change detection among the studied groups to search for the factors involving in the perception of tinnitus and preventing habituation in decompensated tinnitus subjects. Methods: Electroencephalography was recorded from scalp electrodes in compensated tinnitus, decompensated tinnitus, and no tinnitus control subjects. Mismatch negativity was obtained using the oddball paradigm with frequency, duration, and silent gap deviants. Amplitude, latency, and area under the curve of mismatch negativities were compared among the three studied groups. Results: The results showed lower mismatch negativity amplitude and area under the curve for the higher frequency deviant and for the silent gap deviant in decompensated tinnitus group compared to normal control and compensated tinnitus group. Conclusions: This study revealed a deficit in sensory memory and change detection processing in decompensated tinnitus subjects. This causes persistent prediction errors; tinnitus signal is consistently detected as a new signal and activates the brain salience network and consequently prevents habituation to tinnitus. Mismatch negativity is proposed as an index for monitoring tinnitus rehabilitation. © 2019 The Authors. Brain and Behavior published by Wiley Periodicals, Inc

Association between concentration of interleukin-6, 17 and 23 and Helicobacter pylori infection in otitis media with effusion

Background: Helicobacter pylori (H. pylori) cause various diseases especially gastrointestinal disorders. Clinical diagnosis of H. pylori infection can be done in different ways, and new diagnostic methods are under study .This study aimed to assess the levels of interleukin (IL) 6, 17 and 23 in the middle ear effusion of patients with otitis media, and the association between these levels with H. pylori infection. Methods: This cross-sectional study conducted in 40 patients who nominated for ventilation tube (VT) placement due to otitis media with effusion, and admitted to ear, nose, and throat (ENT) clinics of Tehran University of Medical Sciences from March 2012 to August 2013. All of patients underwent myringotomy with VT insertion, and then aspirated effusion sample was tested. H. pylori infection diagnosed by polymerase chain reaction (PCR) and bacterial culture. The concentration of IL-6, IL-17 and IL-23 measured by enzyme-linked immunosorbent assay (ELISA). The levels of each interleukins were compared between the two positive and negative PCR groups. Results: In all of samples, PCR test result was positive in 22.5. The mean and standard deviation of IL-6 level was 10.11±2.95, IL-17 was 5.89±0.91 and IL-23 was 4.07±1.34. The mean±standard deviation (SD) of IL-6 level in patients with a positive PCR (H. pylori) was 22.29±6.40 and in patients with a negative PCR was 6.16±3.88 that difference was significant (P=0.01). The mean±SD of IL-17 level in patients with a positive PCR was 6.16±1.29 and in patients with a negative PCR was 5.81±1.13 that difference was not significant (P=0.42). The mean±SD of IL-23 level in patients with a positive PCR was 6.15±3.77 and in patients with a negative PCR was 3.42±1.33 that difference was not significant (P=0.27). Conclusion: According to finding, association between H. pylori infection and increased levels of IL-6 in the middle ear effusion was approved. It is recommended to conduct researches aimed to identify other cytokines as inflammatory markers. © 2015, Tehran University of Medical Sciences. All Rights Reserved