Duct Length Research Articles

Interobserver variability of cochlear duct measurements in pediatric cochlear implant candidates

PurposeThe objective of the study was to evaluate the proposed cochlear duct length estimation based on the cochlear ‘A value’. Furthermore, we assessed the interobserver variability between radiology and otolaryngology attending physicians and otolaryngology trainees.MethodsThirteen pediatric cochlear implant candidates were retrospectively analyzed by three otolaryngology physicians (attending physician, second year, and fourth year trainees) and a radiology attending. The cochlear duct length was calculated based on the formula of Grover et al. The differences in acquired measurements between observers were compared using the Wilcoxon matched signed-rank test.ResultsThe differences in measurements between the attending otolaryngologist and radiologist were not statistically different, while several significant differences were observed with regard to measurements of attending doctors compared to both residents. In particular, a significant difference between the second year otolaryngology resident and otolaryngology and radiology attending was observed for one side (right ear p = 0.034 and p = 0.012, respectively). Moreover, the fourth year resident calculated significantly different cochlear duct measurements when compared to the attending otolaryngologist (left ear p = 0.014) and radiologist (right ear p = 0.047). Interestingly, differently experienced otolaryngology residents provided significantly different measurements for both ears.ConclusionsBased on these results, cochlear duct length measurement according to the proposed method may be a reliable and cost-effective method. Indeed, otolaryngology training may be sufficient to provide measurements comparable to radiologists. On the other hand, additional efforts should be invested during otolaryngology training in terms of the evaluation of radiological imaging which may increase the capabilities of otolaryngology residents in this regard.

Inlet air fogging strategy using natural gas fuel cooling potential for gas turbine power plants

Fogging is an effective cooling system used for gas turbine (GT) inlet air cooling. In this study, three fogging strategies were tested: direct fogging, fogging with a natural gas (NG) heat exchanger (FNGE), and FNGE using a storage tank (FNGET). The discrete phase model (DPM) with the standard k-ω turbulence model was used. A computational parametric study was conducted using the standard k-ω turbulence model on a GT compressor inlet duct to optimize the effect of the FNGET cooling strategy. The effects of duct length, number of nozzles, uniform droplet diameter, and nozzle angle on the compressor inlet air temperature and relative humidity (RH) were examined in this parametric study. A duct with 15 m length, 48 nozzles in each half, 100 μm droplet diameter, and 60° nozzle angle exhibited the maximum decrease in the temperature of the compressor inlet air. The minimum (maximum) reduction in temperature was 5.54 °C (15.77 °C), which was observed at 30 °C (40 °C) ambient dry-bulb temperature (DBT) and 60% (15%) RH. The minimum (maximum) increase in the GT output power was 8.99 MW (26.44 MW), or 3.87% (11.15%), which was under the ambient conditions of 34 °C (30 °C) and 60% (15%) RH. The maximum enhancement in GT thermal efficiency was 1.47%, which occurred under the ambient conditions of 30 °C DBT and 15% RH. The maximum decrease in GT specific fuel consumption (SFC) was 4.30%, which was seen under the ambient conditions of 30 °C and 15% RH. FNGET was the most effective cooling strategy in terms of GT output power, thermal efficiency, and SFC. This novel cooling strategy can be applied to various GT models.

Anatomy of parotid gland and its secretory ducts in sheep.

The parotid gland in sheep ends freely in front of the masseter muscle, and paracondylary section of occipital bone and extends deep until pterygoid extends of sphenoid bone and hyoid bone. The structure of salivary glands in mammals has been thoroughly studied using histological and sialographic method. This study aimed to reveal the detailed anatomic features and race-specific differences of the canal system of the parotid glands in Akkaraman sheep by using the corrosion cast technique. Thirteen sheep parotid glands from 7 Akkaraman sheep were used in this study. Parotid glands were removed from their places with ducts. Measurements were made with a calliper from back to front, top to bottom and inside to outside. After dissection of the parotid glands, their volumes were measured according to the 'Archimedes principle'. Also, 13 sheep parotid glands were examined using the polyester resin method. In the present study, our average metric results were: length of parotid duct was 10.92 ± 1.027 cm, length of parotid gland was 5.87 ± 1.04 cm, volume of parotid gland was 12.50 ± 2.48 cm³, thickness of parotid gland was 0.75 ± 0.36 cm and width of parotid gland was 4.07 ± 0.43 cm. The average weight of the parotid gland of Akkaraman sheep was identified as 25.3 g. Accessory parotid gland was not encountered in the current study. It was observed that polyester entered into the parotid duct and filled up until the acinus and made both acinus and secretory ducts well-examined in this study. It was also observed that the parotid gland consisted of lobes and lobules. The average number of lobes was 12. The number of lobules in a lobe varied between 3 and 16, each lobe consisted of an average of 9 lobules. It was found that each lobe has its own lobar duct.

Effects of the inlet duct length on the performance of a dense medium cyclone: An experimental and numerical study

The effects of the inlet duct length on the performance of the dense medium cyclones were investigated in this study. The pressure drops and separation efficiencies of the dense medium cyclones with different inlet duct lengths were measured in a cold test rig. A numerical simulation using the four-way coupling method was also conducted to estimate the flow field inside the dense medium cyclone. The experimental results show that a longer inlet duct length results in a lower static pressure drop. The overall separation efficiency first increases and then keeps almost unchanged as the inlet duct becomes longer. The simulated results show that the energy loss decreases as the inlet duct length increases. The changing trends of the static and total pressure drops with the inlet duct length are similar. According to the simulated flow fields, lengthening the inlet gas reduces tangential velocity near the vortex finder and therefore reduces the gas swirling loss. The inlet duct length affects the separation performance mainly by affecting the swirling particle roof. A longer inlet duct leads to fewer particles moving in the swirling particle roof in the dense medium cyclone, which accounts for a better separation efficiency. It was also found that the conventional one-way coupling method fails to qualitatively analyze the effects of inlet duct length on the separation performance of the dense medium cyclone.

Sperm competition in yellow dung flies: No consistent effect of sperm size.

The male competition for fertilization that results from female multiple mating promotes the evolution of increased sperm numbers and can impact sperm morphology, with theory predicting that longer sperm can at times be advantageous during sperm competition. If so, males with longer sperm should sire more offspring than competitors with shorter sperm. Few studies have directly tested this prediction, and findings are inconsistent. Here we assessed whether longer sperm provide a competitive advantage in the yellow dung fly (Scathophaga stercoraria; Diptera: Scathophagidae). Initially, we let brothers with different temperature-mediated mean sperm lengths compete - thus minimizing confounding effects of genetic background - and found no clear advantage of longer sperm. We then used flies from lines subjected to bidirectional selection on phenoloxidase activity that had shown correlated evolutionary responses in sperm and female spermathecal duct lengths. This experiment also yielded no main effect of sperm size on siring success. Instead, there was a trend for a shorter-sperm advantage, but only when competing in females with longer spermathecal ducts. Our data corroborated many previously reported findings (last-male precedence, effects of copula duration and body size), suggesting our failure to find sperm size effects is not inherently due to our experimental protocols. We conclude that longer sperm are not competitively superior in yellow dung flies under most circumstances, and that, consistent with previous work, in this species competitive fertilization success is primarily determined by the relative numbers of sperm competing.

Measuring the cochlea using atablet-based software package: influence of imaging modality and rater background

HintergrundDie Größe der Cochlea ist individuell unterschiedlich, was sich in der variablen Länge des Ductus cochlearis (CDL) ausdrücken lässt. In der Cochleaimplantatversorgung ist ein in der Länge angepasster Elektrodenträger durch eine optimale Abdeckung der Cochlea erfolgversprechend. Dazu kann die CDL auf Höhe des Corti-Organs (CDLOC) mittels eines Tablet-basierten Softwarepakets ausgemessen werden, um abgestimmt auf die Anatomie einen passenden Elektrodenträger auszuwählen.FragestellungHaben die Modalität der Bildgebung und der Untersucherhintergrund einen Einfluss auf die Vermessung der CDL?MethodenDie Datensätze der Magnetresonanztomographie (MRT) und Flachdetektor-Volumen-Computertomographie (fpVCT) von 10 Patienten (20 Cochleae) wurden in der Software OTOPLAN (MED-EL, Innsbruck, Österreich) analysiert. Als Untersucher wurden eine Oberärztin der Hals-Nasen-Ohren-Heilkunde, eine Assistenzärztin der HNO-Heilkunde und ein Audiologe ausgewählt. Zur Analyse der Effekte der Bildgebung und des Untersucherhintergrunds auf die CDL-Messungen wurden linear gemischte Modelle konstruiert.ErgebnisseDie Messungen ergaben einen Mittelwert CDLOC(fpVCT) = 36,69 ± 1,78 mm und CDLOC(MRT) = 36,81 ± 1,87 mm. Die Analysen zeigten keinen signifikanten Effekt des Untersucherhintergrunds auf die Messergebnisse (F (2, 105) = 0,84; p = 0,437). Die Bildgebungsmodalität zeigte einen signifikanten Einfluss (F (1, 105) = 20,70; p < 0,001), wobei die Messungen an MRT im Mittel um 0,89 mm größer waren.SchlussfolgerungDa der Untersucherhintergrund keinen Einfluss auf die Messungen hatte, lässt sich schließen, dass die Messungen nicht ausschließlich von ärztlichem Personal, insbesondere nicht nur von erfahrenen Neurootologen, durchgeführt werden müssen. Die Methode der Bildgebung (fpVCT vs. MRT) kann die CDL-Werte statistisch signifikant beeinflussen, wobei eine klinische Relevanz fraglich ist.

Converted-hepatopancreatoduodenectomy for an intraoperative positive ductal margin after pancreatoduodenectomy in distal cholangiocarcinoma.

Pancreatoduodenectomy (PD) is the standard treatment for distal cholangiocarcinoma, and a negative ductal margin (DM0) is indispensable for the long-term survival. When intraoperative frozen sections of ductal margin after PD are positive, converted-hepatopancreatoduodenectomy (C-HPD) is the final option available to gain an additional ductal margin. However, the efficacy of C-HPD remains unclear. Patients who underwent PD or C-HPD for distal cholangiocarcinoma between 2002 and 2019 were analyzed. The type of hepatectomy in C-HPD was restricted to left hepatectomy to prevent posthepatectomy liver failure. Of 203 patients who underwent PD for distal cholangiocarcinoma, 49 patients exhibited intraoperative positive ductal margin (DM1) after PD. Eleven patients underwent C-HPD for intraoperative DM1 after PD, in which intraoperative DM1 with invasive carcinoma (DM1inv) was observed in 3 patients, and intraoperative DM1 with carcinoma in situ (DM1cis) was observed in 8 patients. The median additional ductal margin yielded by C-HPD was 9mm (interquartile range 7-13mm). C-HPD eradicated intraoperative DM1inv in 3 patients, with 2 patients showing DM0 and 1 patient showing DM1cis. Regarding 8 patients who underwent C-HPD for intraoperative DM1cis, 4 patients had DM0, but the others had DM1cis. C-HPD was associated with a high complication rate, but no mortality was observed. The median survival time of patients who underwent C-HPD was 48.8months. C-HPD was able to safely eradicate intraoperative DM1inv after PD. However, the length of the resected bile duct according to C-HPD may not be sufficient to remove intraoperative DM1cis after PD.

Extrahepatic Biliary Tract Variations is an Effect for Acute Calculous Cholecystitis.

To evaluate the anatomy of the extrahepatic bile duct and to reveal its importance in the formation of acute calculous cholecystitis (ACC). Case-control study. Department of General Surgery and Radiology, Kanuni Sultan Suleyman Training and Research Hospital of the University of Health Sciences, Turkey, between January 2016 and December 2021. The data of the patients treated with ACC were analysed on MRCP by an experienced radiologist. The patients were divided into two groups; asymptomatic gallstones (AsGS, control group) and ACC. The cystic duct, common hepatic duct, and common bile duct lengths and variations in cystic duct opening were measured. Receiver operating characteristics (ROC) analysis was conducted to define a cut-off value and compared categorical results of the two groups by Mann-Whitney U test. One-hundred and seventy-three patients were analysed, one-hundred and seven were females, and 66 were males. The median age was 46 years in the AsGS group and 53 years in the ACC group. It was statistically significant that ACC had a higher median age value than AsGS (p=0.014). In the analysis of extrahepatic variations, cystic duct, common hepatic duct, and common bile duct length, were statistically longer in the calculous cholecystitis group (p<0.001, p=0.022, and p=0.019 respectively). ROC analysis was performed for cystic, common hepatic, and common bile duct length, respectively. Cut-off values ​​were 30.5 mm, 36.5 mm, and 42.5 mm. Extrahepatic bile duct variations are of critical importance in ACC surgery. In the data, as the cystic duct and common bile duct lengthens, the possibility of ACC increases. There is need for studies with larger samples. Acute calculous cholecystitis, Extrahepatic biliary tract, Anatomical variations, Cholelithiasis.

Establishing correlations between normal pancreatic and submandibular gland ducts

BackgroundThe objectives of this study were to evaluate the relationship between ductal morphometry and ramification patterns in the submandibular gland and pancreas in order to validate their common fractal dimension.MethodsX-ray ductography with software-aided morphometry were obtained by injecting barium sulphate in the ducts of post-mortem submandibular gland and pancreas specimens harvested from 42 adult individuals.ResultsThree cases were excluded from the study because of underlying pathology. There was a significant correlation between the length of the main pancreatic duct (MPD) and the intraglandular portion of the right submandibular duct (SMD) (r = 0.3616; p = 0.028), and left SMD (r = 0.595; p < 0.01), respectively, but their maximal diameters did not correlate (r = 0.139—0.311; p > 0.05). Both dimensions of the SMD showed a significant right-left correlation (p < 0.05). The number of MPD side branches (mean = 37) correlated with the number of side branches of left SMD, but not with the right one (mean = 9). Tortuosity was observed in 54% of the MPD, 32% of the right SMD, and 24% of the left SMD, with mutual association only between the two salivary glands.ConclusionsAlthough the length of intraglandular SMD and MPD correlate, other morphometric ductal features do not, thus suggesting a more complex relationship between the two digestive glands.

Artificial neural network based shape optimization of supersonic ejectors in the critical flow regime

Supersonic ejectors are widely used in energy, refrigeration, and aerospace propulsion applications. A supersonic ejector is a passive gasdynamic device consisting of a converging–diverging nozzle located in a varying area mixing duct where the secondary fluid is compressed by mixing with high momentum primary fluid. The entrainment ratio (ER, ratio of mass flow rates of the secondary to primary flow) is dependent on the mixing duct geometry, necessitating shape optimization. Complex gasdynamic interactions in the ejector are not fully understood, thus making physics-based or CFD modeling, a challenging exercise. In this paper, experimental data for ejector performance with varying geometries and operating parameters, viz. area ratio, primary flow Mach number, mixing duct length to height ratio (L/D), and stagnation pressure ratio is presented. The mixing length parameter is quantified using data derived from high-speed schlieren images. Improvement in ER to the extent of 20% is achieved by changing L/D to 15 for the AR of 3.33, with further increase in L/D resulting in a reduction in ER. Subsequently, computationally inexpensive model using ANN is developed to predict the ejector performance using the experimental database. The model predicts ER with an accuracy of 7%. Finally, the ANN model is used to optimize the ejector geometry for critical mode operation, which provides a 30% enhancement in entrainment ratio compared to the baseline geometry.

Difference in cochlear length between male and female patients

Objective: To compare cochlear duct length (CDL) between male and female patients by evaluating the diameter of the basal turn (distance A) on CT scans. Method: All temporal bone CT scans performed between 2014 and 2020 were reviewed in our medical center. Using multiplanar reconstructions, the length A, which is the greatest distance of the basal turn was measured on both sides. We performed an analysis of variance considering two factors: sex and side. Two different physicians carried out the measurements, an otolaryngologist and a neuroradiologist. The patients who had several CT scans allowed us to evaluate the reliability of our procedure. Results: Among the 888 CT scans reviewed, 8 were excluded because of cochlear malformations. The inter-sex difference of length A was found to be 0.29 millimeters(mm) 95% IC [0.26-0.34] and was longer in the male group (p < 0.0001). Using Alexiades' equation, we found that CDL was 34.5mm [34.37-34.61] in the male group and 33.3mm [33.13-33.38] in the female group. When one side was compared to the other, there was no significant difference (p = 0.226). An intra-class correlation found a good absolute agreement between the two screeners of 0.79. Conclusion: Males have a statistically significant longer CDL than females.

Optimizing clinical outcomes for endoscopic lacrimal duct recanalization in patients with complete PANDO.

The study aims to describe modifications and refinements in the technique and technology of Transcanalicular Endoscopic Lacrimal Duct Recanalization (TELDR) based on anatomical foundations to optimize its clinical outcomes in patients with complete Primary Acquired Nasolacrimal Duct Obstruction (PANDO). The medical records of 115 patients who underwent TELDR procedures from January 2018 to July 2020 were reviewed retrospectively. Of the 115 patients, only those 35 patients with complete PANDO characterized by longstanding epiphora of 3-5years duration, dense, diffuse fibrous tissue obstruction involving the sac, sac duct junction and the entire length of the nasolacrimal duct were included in the study. Parameters for success were analyzed based on patency on irrigation, functional endoscopic dye test, and improvement of epiphora. Forty-five cases from 35 patients with complete PANDO were included in the study. The mean length of time from the date of operation to silicone stent removal was 8.1weeks, while the mean length of follow-up starting from the removal of silicone stent to last follow-up was 61.0weeks. There were 95.6% anatomic patency on canalicular irrigation with saline and 95.6% functional patency based on functional endoscopic dye test. There was significant improvement of epiphora (p value of < 0.0001) post-operatively. The results of modified TELDR improved clinical outcomes and could be a definitive treatment in patients with complete PANDO with longstanding, dense, diffuse, fibrous tissue obstruction. Patients who experience reobstruction, may undergo a repeat of the recanalization approach.

Noise distribution law of air-conditioning ducts for metro vehicles

The passenger comforts are directly affected by the air supply uniformity and noise of air-conditioning duct inside the metro vehicle. In order to solve the integrated design problem of air supply uniformity and noise control of air-conditioning ducts, a theoretical model is established to analyze the air supply uniformity, noise attenuation, and airflow regeneration noise of the air-conditioning duct. The distribution law of the sound pressure level along the longitudinal air outlet was calculated, and the calculated results were compared with test ones. For a typical air supply duct with a constant cross section: (1) In order to ensure air supply uniformity at the outlet of the static pressure chamber, the area of the side air hole should be gradually increased in an exponential form along the direction of the main flow, and cannot be designed in the equal area form. (2) The airflow speed of each side hole decreased in sequence along the air duct length. In order to ensure the uniformity air supply of each side hole, the area of each side hole must be gradually increased. (3) The noise in the air conditioner duct was mainly concentrated at the front end of the air duct, and the noise at the subsequent air outlet can fully meet the current requirements of subway vehicles for indoor noise. Therefore, the front end of the air duct is the most important area for noise control.

Morphological and Genetic Variability in Radix auricularia (Mollusca: Gastropoda: Lymnaeidae) of Lake Baikal, Siberia: The Story of an Unfinished Invasion into the Ancient Deepest Lake

This article aims to reconstruct the invasion of the ear-shaped pond snail, Radix auricularia (Linnaeus, 1758), to Lake Baikal, East Siberia. This species is widely distributed in the Palaearctic and Northern America, and since the early 20th century has formed abundant and sustained populations in Lake Baikal. The data provided on the morphological and genetic variability of R. auricularia help to better describe and delineate the species. With an integrative approach involving morphological and molecular data, we improved the knowledge of the intraspecific variability of R. auricularia in the most important characteristics used for its determination. Molecular sequences of nuclear spacer fragment ITS-2 and mitochondrial gene fragment cyt–b were obtained from 32 individuals of Radix (including seven outgroup Radix species) collected from various parts of Lake Baikal and adjacent waterbodies and compared with sequences of 32 individuals of R. auricularia from different regions of the Palaearctic as well as with individuals determinated as R. intercisa from Lake Baikal, R. iturupica from the Kurile Islands, R. ussuriensis from the Khabarovsk region, R. narzykulovi from Tajikistan, and R. schubinae from the Amur region. Molecular genetic analyses revealed that all specimens collected from Lake Baikal belong to R. auricularia. There are no genetically distinct groups of snails that would correspond to two morphospecies previously recorded in Lake Baikal (e.g., R. auricularia s. str. and R. intercisa). Variability of the characteristics that are commonly used for species identification (shell morphology, mantle pigmentation, shape and position of the bursa copulatrix, length and position of the bursa duct, length ratio of preputium to penial sheath) were found in individuals analysed with molecular genetics to be broader than recognised in the current literature. Some shells of R. auricularia collected from Lake Baikal resemble shells of another lymnaeid species, R. balthica, and without molecular assessment can be confused with the latter. Geometric morphometric analysis of more than 250 shells revealed no observed hiatus between Baikalian and non-Baikalian R. auricularia. The probable stages and pathways of R. auricularia invasion to Lake Baikal’s ecosystem are outlined and discussed. Factors such as global climate warming and human activity stimulated and facilitated the ongoing dispersal of ear pond snails within Lake Baikal.

Right posterior bile duct stricture after central bisectionectomy or anterior sectionectomy.

Before performing anterior sectionectomy (AS) or central bisectionectomy (CBS), the anatomy of the right posterior bile duct (RPBD) must be cautiously assessed owing to the many variations of the RPBD and its variations could be related to bile duct injury. Clinical data of patients who underwent AS or CBS from 2009 to 2018 were reviewed. The bile duct anatomy according to Okubo's criteria and the right bile duct (RBD) length were evaluated using MRI, and we performed a risk factor analysis of the RPBD stricture (RPBDS). A total of 68 patients were included. Type A bile ducts were the most common (n = 36, 52.9%). Five (7.2%) patients had RPBDS requiring intervention. RPBDS only occurred in patients with a type A bile duct and a type A portal vein undergoing surgery using the Glissonian sheath approach. Moreover, when the RBD length was > 12mm, the sensitivity and specificity were 0.8 and 0.889, respectively. In multivariate analysis, RBD length of > 12mm was significant. A careful review of RPBD anatomy especially in patient with long RBD and caution when using the anterior Glissonian sheath approach might be helpful to prevent RPBDS during AS or CBS.

On the effect of inter compressor duct length on compressor performance

AbstractCompression systems of modern, civil aircraft engines consist of three components: Fan, low-pressure compressor (LPC) and high-pressure compressor (HPC). The efficiency of each component has improved over the last decades by means of rising computational power which made high level aerodynamic optimisations possible. Each component has been addressed individually and separated from the effects of upstream and downstream components. But as much time and effort has been spend to improve performance of rotating components, the stationary inter-compressor duct (ICD) has only received minor attention. With the rotating compression components being highly optimised and sophisticated their performance potential is limited. That is why more aggressive, respectively shorter, ICDs get more and more into the focus of research and engine manufacturers. The length reduction offers high weight saving and thus fuel saving potential as a shorter ICD means a reduction in aircraft engine length. This paper aims at evaluating the impact of more aggressive duct geometries on LPC and HPC performance. A multi objective 3D computational fluid dynamics (CFD) aerodynamic optimisation is performed on a preliminary design of a novel two spool compressor rig incorporating four different operating line and two near-stall (NST) conditions which ensure operability throughout the whole compressor operating range. While the ICD is free to change in length, shape and cross-section area, the blades of LPC and HPC are adjusted for changing duct aerodynamics via profile re-staggering to keep number of free parameters low. With this parametrisation length, reductions for the ICD of up to 40% are feasible while keeping the reduction in isentropic efficiency at aerodynamic design point for the compressor below 1%pt. Three geometries of the Pareto front are analysed in detail focusing on ICD secondary flow behaviour and changes of aerodynamics in LPC and HPC. In order to asses changes in stall margin, speedlines for the three geometries are analysed.

Optimization design of airflow arrangement device for shiitake mushroom based on dynamic modeling and simulation

As there is no mature agricultural automation device for trimming roots and stipes of shiitake mushrooms, this paper proposes a novel arrangement method to improve its processing efficiency. A dynamic model of shiitake mushrooms in airflow is established to analyze their motion states to assess the feasibility of this methodology, and computational fluid dynamics is used to establish aerodynamic coefficients. The dynamic model presents the relationship between the motion state and the airflow. In this device, a stable state is needed, which means the shiitake mushroom should maintain its stipe pointing up. Then the Monte Carlo simulation method is conducted to optimize the device to achieve a high probability of stipe upward with an appropriate length of ventilation duct and wind velocity. Thus, our methodology can be effectively used to arrange mushrooms for further application in a trimming and separation device.

Mathematical modeling of pulmonary acinus structure: Verification of acinar shape effects on pathway structure using rat lungs

The pulmonary acinus is the gas exchange unit in the lung and has a very complex microstructure. The structure model is essential to understand the relationship between structural heterogeneity and mechanical phenomena at the acinus level with computational approaches. We propose an acinus structure model represented by a cluster of truncated octahedra in conical, double-conical, inverted conical, or chestnut-like conical confinement to accommodate recent experimental information of rodent acinar shapes. The basis of the model is the combined use of Voronoi and Delaunay tessellations and the optimization of the ductal tree assuming the number of alveoli and the mean path length as quantities related to gas exchange. Before applying the Voronoi tessellation, controlling the seed coordinates enables us to model acinus with arbitrary shapes. Depending on the acinar shape, the distribution of path length varies. The lengths are more widely spread for the cone acinus, with a bias toward higher values, while most of the lengths for the inverted cone acinus primarily take a similar value. Longer pathways have smaller tortuosity and more generations, and duct length per generation is almost constant irrespective of generation, which agrees well with available experimental data. The pathway structure of cone and chestnut-like cone acini is similar to the surface acini's features reported in experiments. According to space-filling requirements in the lung, other conical acini may also be acceptable. The mathematical acinus structure model with various conical shapes can be a platform for computational studies on regional differences in lung functions along the lung surface, underlying respiratory physiology and pathophysiology.

Dynamics of Small Particle Inertial Migration in Curved Square Ducts

Microchannels are well known in microfluidic applications for the control and separation of microdroplets and cells. Often the objects in the flow experience inertial effects, resulting in dynamics that is a departure from the underlying channel flow dynamics. This paper considers small neutrally buoyant spherical particles suspended in flow through a curved duct having a square cross-section. The particle experiences a combination of inertial lift force induced by the disturbance from the primary flow along the duct, and drag from the secondary vortices in the cross-section, which drive migration of the particle within the cross-section. We construct a simplified model that preserves the core topology of the force field yet depends on a single parameter $\kappa$, quantifying the relative strength of the two forces. We show that $\kappa$ is a bifurcation parameter for the dynamical system that describes motion of the particle in the cross-section of the duct. At large values of $\kappa$ there exists an attracting limit cycle in each of the upper and lower halves of the duct. At small $\kappa$ we find that particles migrate to one of four stable foci. Between these extremes, there is an intermediate range of $\kappa$ for which all particles migrate to a single stable focus. Noting that the positions of the limit cycles and foci vary with the value of $\kappa$, this behavior indicates that, for a suitable particle mixture, duct bend radius might be chosen to segregate particles by size. We evaluate the time and axial distance required to focus particles near the unique stable node, which determines the duct length required for particle segregation.

Anatomy of the nasolacrimal duct in Persian cats determined by computed tomographic dacryocystography.

This study sought to describe the anatomical characteristics of the nasolacrimal duct of Persian cats as observed by computed tomographic dacryocystography. Ten cats weighing 3-6kg (three live cats and seven cadaveric specimens). The animals were submitted to bilateral computed tomographic dacryocystography, totaling 20 nasolacrimal ducts. Dorsal, sagittal, and transverse planes were studied. Two additional skulls were also dissected following latex injection into the nasolacrimal duct. The length and width of the nasolacrimal duct and lacrimal canaliculi, and the distance between the nasolacrimal duct and the root of the upper canine tooth at the point of closest proximity were measured. The nasolacrimal duct followed a convoluted course, particularly in the middle and rostral portions. Duct stenosis (width reduction equal to or >75%) and dilations (width increase equal to or >50%) were also detected, particularly in the rostral portion. Nasolacrimal duct length and width ranged from 1.3 to 1.5cm and 1.5 to 2.3mm, respectively. Mean lacrimal canaliculus length and width corresponded to 3.1mm and 0.4mm, respectively. Mean distance from the nasolacrimal duct to the canine tooth was 2.4mm. The root of this tooth interfered with the course of the nasolacrimal duct. This study provided anatomical information for clinical assessment of the nasolacrimal drainage system in Persian cats.