Large Caliber Research Articles

НАУЧНО-ТЕХНИЧЕСКАЯ КОЛЛЕКЦИЯ ГОРНОГО МУЗЕЯ КАК ОТРАЖЕНИЕ ИСТОРИИ ПУШЕЧНОГО ЗАВОДА В МОТОВИЛИХЕ (1863 – 1900 гг.)

The article describes the history of the Perm Cannon Factory founded in the mid-1860s in the village of Motovilikha. The factory was created to produce large-caliber steel rifled cannons for coastal and naval artillery. But cast-iron cannons of large calibers were also produced there. The exhibits of the Mining Museum of the St. Petersburg Mining University are considered as material evidence of the history of the production of artillery weapons and modernization of the Perm Cannon Factory in the second half of the 19th century. These are models of tools and equipment, among which are the developments of graduates of the Mining University — N.V. Vorontsov and M.D. Nazarov. The article also shows the role of the personal factor in the development of the Russian defense industry.

Solvothermal synthesis of organoclay/Cu-MOF composite and its application in film modified GCE for simultaneous electrochemical detection of deoxyepinephrine, acetaminophen and tyrosine.

An organoclay/copper-based metal-organic framework (MOF) composite was synthesized using a solvothermal method by growing a Cu-BTC (copper(ii) benzene-1,3,5-tricarboxylate) MOF from a mixture of the MOF precursor solution in which various amounts of organoclay had been dispersed. The organoclay was obtained by intercalating a cationic dye, namely thionin, into a natural Cameroonian clay sampled in Sagba deposit (North West of Cameroon). The organoclay and the as-synthesized composites were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) techniques. From Scherrer's equation, the crystallite size of the composite was found to be between 55 and 58 nm, twice as large as the pristine MOF's crystallite size. The organoclay/Cu-MOF composite (Sa-TN50/Cu3(BTC)2) exhibiting a BET surface area of 192 m2 g-1, about twice that of pristine clay and about one seventh that of pristine MOF, was then utilized to form a stable thin film onto glassy carbon electrodes (GCE) by drop coating (Sa-TN50/Cu3(BTC)2/GCE). These electrodes demonstrated electrocatalytic behavior toward deoxyepinephrine (DXEP) and thus enabled selective and simultaneous sensitive detection of three analytes: DXEP, acetaminophen (AC) and tyrosine (TYR) compared with bare GCE and clay modified electrode. Under optimum conditions, Sa-TN50/Cu3(BTC)2/GCE exhibited good performance including large calibration curves ranging from 5.0 μM to 138.0 μM for DXEP, 4.0 μM to 153.0 μM for AC and 1.0 μM to 29.4 μM for TYR. The detection limits were found to be, 0.4 μM, 0.7 μM and 0.2 μM for DXEP, AC and TYR, respectively. The developed sensors have been applied successfully in the quantification of AC in a commercial tablet of AC, and DXEP, AC and TYR in tap water.

A curious case of confusion

A curious case of confusion

Krążownik ciężki – problemy klasyfikacyjne. Część 2: Okręty o klasyfikacji spornej

This article is the second in a series of six texts devoted to classification problems in the group of artillery ships such as heavy cruisers. In the first one, we dealt with the genesis of the heavy cruiser and formulated its definition, necessary for making reliable scientific analyzes. In this section, we confronted this definition with ships with a disputed classification. The following will discuss the fleets of this class of ships from all ten countries that have them, and their global characteristics. Of the 26 ships with a disputed classification in terms of their potential assignment to the category of heavy cruisers, 16 ships should be granted this status, and 10 ships should not, for various reasons. The main disqualifying factors were: the outdated layout of the main artillery towers (Blücher, Effingham, Frobisher, Hawkins, Raleigh, Vindictive), too few main artillery guns (Frobisher, Krasnyj Kavkaz, Hawkins, Vindictive), too small caliber of the main artillery (Effingham, Vindictive), too large caliber of the main artillery (Admiral Scheer, Admiral Graf Spee, Blücher, Lützow). As for the disputed heavy cruisers, which we have maintained in this study on the basis of substantive criteria, the only factor raised against the legitimacy of such a step was the possession of the main armament in the form of guns with a caliber not exceeding 200 mm, as all the other conditions for belonging to this class of ships have been met. The issue of caliber, however, is firmly anchored in naval armaments limitation treaties, in which a total of 6 of the world’s largest maritime powers participated (Great Britain, the United States, Japan, France, Italy and Germany), which together have the overwhelming majority of the world’s naval fleet in general and heavy cruisers in particular. In this situation, the arguments in favor of increasing its minimum limit from 156 to 201 mm should be assessed as insufficient. As a result, we recog- nize that the units discussed in this paper: Almirante Brown, Aoba, Ashigara, Furutaka, Haguro, Kaganovič, Kako, Kalinin, Kinugasa, Kirov, Maksim Gor’kij, Molotov, Myōkō, Nachi, Veinticinco de Mayo and Vorošilov belong to the heavy cruiser class.

Uniaxial MEMS-based 3D reconstruction using pixel refinement.

A uniaxial micro-electro-mechanical systems (MEMS) micro-vibration mirror can be used to construct a new type of fringe projection profilometry (FPP) system. In FPP system calibration, some pixels may be calibrated worse than other pixels due to various error sources, which will affect the final reconstruction accuracy. In addition, there are some difficulties in calibrating the MEMS-based system because a projector using the uniaxial vibration mirror does not have focusing optics and can only project unidirectional fringes. In this paper, we developed an FPP system using a uniaxial MEMS micro-vibration mirror. To solve the calibration problems, we propose a calibration model suitable for the MEMS-based system and a pixel refinement method. These pixels with relatively large calibration errors are called outlier-pixels, which will significantly increase the error of the following 3D mapping. Therefore, the pixel refinement method classifies all pixels based on a frequency distribution histogram of calibration errors during calibration and prevents outlier-pixels from participating in the following 3D mapping. The experimental results show that the proposed method can improve the accuracy of 3D reconstruction, and the feasibility of the self-developed system is verified.

Use of tactile sensors for horizontal stress measurements on a large calibration chamber

Large flexible calibration chambers (CCs) to evaluate and develop interpretation methods for cone penetration tests (CPTs) in cohesionless soils have been used since the late 1960s. Nevertheless, only average boundary stress values are known in almost all tests already performed. Tactile pressure sensors (TPS) represent a useful tool to assess the stress distribution in an area under loading and have been applied in some geotechnical studies. This study presents the results of CPTs carried out on a large flexible CC in a very loose and a medium-dense fine quartz sand. TPS were placed on the walls of the CC, allowing the measurement of horizontal stresses and their spatial distribution in all test phases: sample formation, lateral and cavity cell filling, piston filling, sample stressing and CPT. In particular, TPS were able to measure the horizontal stresses before the cavity and lateral cell filling – that is, when no information is available about the horizontal stresses in regular tests. The measurements contribute to the discussion on the influence of the CC boundaries on the test results. The results encourage the use of TPS on a more routine basis in large flexible CC testing.

Numerical methods for CT reconstruction with unknown geometry parameters

Computed tomography (CT) techniques are well known for their ability to produce high-quality images needed for medical diagnostic purposes. Unfortunately, standard CT machines are extremely large, heavy, require careful and regular calibration, and are expensive, which can limit their availability in point-of-care situations. An alternative approach is to use portable machines, but parameters related to the geometry of these devices (e.g., distance between source and detector, orientation of source to detector) cannot always be precisely calibrated, and these parameters may change slightly when the machine is adjusted during the image acquisition process. In this work, we describe the non-linear inverse problem that models this situation, and discuss algorithms that can jointly estimate the geometry parameters and compute a reconstructed image. In particular, we propose a hybrid machine learning and block coordinate descent (ML-BCD) approach that uses an ML model to calibrate geometry parameters, and uses BCD to refine the predicted parameters and reconstruct the imaged object simultaneously. We show using numerical experiments that our new method can efficiently improve the accuracy of both the image and geometry parameters.

Management of Free Fillet Flap Transfers in Large Oncologic Resections

A retrospective review of the medical records of eight patients who underwent fillet flap reconstruction from 2013 to 2021 at Mayo Clinic, Arizona, were analyzed. Eight patients who underwent four hemipelvectomies, three forequarter amputations, and one below the knee amputation were identified. Patients' ages ranged between 24 and 66 years. All indications for oncologic ablation were curative. Defect sizes ranged from 16 × 20 to 30 × 60 cm. Four pedicled flaps and four free fillet flaps were performed. Indication for free fillet flap was tumor invasion of local vascular structures. There was no flap loss in the pedicled group (follow-up ranged from 1 to 9 years), and one of four free fillet flaps had a successful long-term outcome (follow-up 36 months). Successful free fillet flap reconstruction in the setting of oncologic resection is a difficult task to achieve. Changes to the management of case 3F allowed for a successful transfer. Immediate elevation and anastomosis of the flap before oncologic resection, large caliber recipient vessels and isolation from the zone of injury, protection of the anastomosis, and delay in flap inset all contributed to flap survival. It is our belief that applying these general considerations in large oncologic resections with free fillet flap transfer may aid in successful flap transfer and improve its survival odds.

Diffusion MRI anisotropy in the cerebral cortex is determined by unmyelinated tissue features

Diffusion magnetic resonance imaging (dMRI) is commonly used to assess the tissue and cellular substructure of the human brain. In the white matter, myelinated axons are the principal neural elements that shape dMRI through the restriction of water diffusion; however, in the gray matter the relative contributions of myelinated axons and other tissue features to dMRI are poorly understood. Here we investigate the determinants of diffusion in the cerebral cortex. Specifically, we ask whether myelinated axons significantly shape dMRI fractional anisotropy (dMRI-FA), a measure commonly used to characterize tissue properties in humans. We compared ultra-high resolution ex vivo dMRI data from the brain of a marmoset monkey with both myelin- and Nissl-stained histological sections obtained from the same brain after scanning. We found that the dMRI-FA did not match the spatial distribution of myelin in the gray matter. Instead dMRI-FA was more closely related to the anisotropy of stained tissue features, most prominently those revealed by Nissl staining and to a lesser extent those revealed by myelin staining. Our results suggest that unmyelinated neurites such as large caliber apical dendrites are the primary features shaping dMRI measures in the cerebral cortex.

One for All and All for One.

A 76-year-old woman with a history of hypertension and hypercholesterolemia was seen in the outpatient cardiology clinic for atypical chest pain. According to current chronic coronary syndrome guidelines, owing to female sex, age > 70 years, and atypical chest pain, the patient's pretest probability of obstructive coronary artery disease was 19%, and therefore a computed tomography (CT) coronary angiography was performed, which showed a calcium score of 0. The left main (LM) coronary artery was long, hypoplasic, tortuous, and bifurcated in the proximal left auriculoventricular groove into a hypoplasic proximal left circumflex (LCX) and a left anterior descending (LAD) coronary artery with a larger calibre than the LM (Fig. 1A and B).

Hypogastric artery ligation. Presentation of a case from the Teófilo Dávila General Hospital

Hemorrhage etymologically comes from the Latin haemorragia, from the Greek, αἱμορραγία composed of haima (blood) and regnymi (break), passed to Latin hemorrhage and later to Spanish, documenting it as emorragia in 1493. From a conceptual point of view, postpartum hemorrhage is defined as a blood loss greater than 500 ml in a vaginal delivery and greater than 1000 ml in a cesarean section, being among the leading causes of maternal death worldwide. The hypogastric artery is a large caliber vessel, responsible for the irrigation of a large area of ​​the pelvis and the organs located there. Hypogastric artery ligation is a surgical technique that was first described in 1894 with the aim of reducing gynecological and obstetric hemorrhage, since it endangers the life of the patient, increasing morbidity and mortality. This therapeutic surgical procedure should be taken into account as an effective method in the control of severe gynecological hemorrhages, where intraoperative complications are foreseeable with adequate knowledge of retroperitoneal anatomy.

A high-accuracy calibration method for fusion systems of millimeter-wave radar and camera

Multi-sensor information fusion is widely used in the field of unmanned aerial vehicles obstacle avoidance flight, particularly in millimeter-wave (MMW) radar and camera fusion systems. Calibration accuracy plays a crucial role in fusion systems. The low-angle measurement accuracy of the MMW radar usually causes large calibration errors. To reduce calibration errors, a high-accuracy calibration method based on a region of interest (ROI) and an artificial potential field was proposed in this paper. The ROI was selected based on the initial calibration information and the MMW radar’s angle measurement error range from the image. An artificial potential field was established using the pixels of the ROI. Two moving points were set at the left and right ends of the ROI initially. The potential forces of the two moving points are different because the pixels of the obstacle and the background are different in the image. The two moving points were iteratively moved towards each other according to the force until their distance was less than the iteration step. The new calibration point is located in the middle of the final position of the two moving points. In contrast to the existing calibration methods, the proposed method avoids the limitations of low angle measurement accuracy by using image pixels. The experimental results show that the calibration errors decrease by 83.95% and 75.79%, which is significantly improved compared to the traditional methods and indicates the efficiency of the proposed method.

S2813 Compacted Periampullary Diverticulum Masquerading as Pancreatic Head Mass on Endoscopic Ultrasound

Introduction: Endoscopic ultrasound (EUS) has become an increasingly important modality in the diagnosis and treatment of gastrointestinal malignancy as well as both pancreatic and biliary disease. It provides high-resolution, real-time imaging of the GI tract and surrounding structures. EUS is classically operator dependent and can often display suboptimal sensitivity and specificity. Numerous techniques such as Endoscopic guided fine-needle aspiration (EUS-FNA), EUS fine needle biopsy (EUS-FNB), rapid on-site cytological evaluation (ROSE) and contrast harmonic-enhanced EUS (CH-EUS) help to increase the sensitivity and specificity of this diagnostic modality. The following case describes a patient with initial EUS findings concerning for pancreatic head malignancy which was ultimately identified as a periampullary diverticulum compacted with sludge. Case Description/Methods: A 70-year-old patient with a past medical history of prostate cancer and cholelithiasis status post recent cholecystectomy presented with CT imaging findings concerning for pancreatic head mass. The patient underwent initial EGD with EUS which illustrated a well circumscribed, heterogeneously echoic 26.8 x 24 mm uncinate process mass concerning for neuroendocrine tumor (NET). FNB was performed and cytology ultimately showed no evidence of malignancy. Due to continued concern for pancreatic NET, patient underwent repeat EGD and EUS. EUS redemonstrated the large heterogeneously echoic pancreatic head lesion concerning for mass. Attempts were made to visualize the ampulla with linear EUS scope, however there was significant debris in the second portion of the duodenum. Duodenoscope was then passed and a large caliber but narrow opening periampullary diverticulum was visualized and appeared to be filled with compacted sludge. A combination of biopsy forceps and water lavage was used to clean out the compacted sludge. The EUS scope was then re-advanced into the second part of the duodenum and the suspected mass which was previously visualized was no longer visible. (Figure) Discussion: EUS is a an important, minimally invasive diagnostic procedure that has both high clinical success rate with relatively few adverse events. EUS, like many other diagnostic modalities, has limitations when identifying and ruling out malignancy. This case highlights one such limitation showing that although initial findings were concerning for malignancy, further investigation revealed a duodenal diverticulum with compacted debris masquerading as an uncinate mass.Figure 1.: A. EUS showing heterogeneously echoic 26.8 x 24 mm uncinate process mass B. Duodenoscope showing periampullary diverticulum compacted with sludge, removed with lavage and biopsy forceps C. Repeat EUS showing absence of previously visualized uncinate mass.

S2498 Endoscopic Treatment of a Dieulafoy’s Lesion in the Appendiceal Orifice

Introduction: A Dieulafoy’s lesion, typically a large caliber submucosal artery that erodes gastrointestinal (GI) mucosa, is a less common cause of GI bleeding. While these vascular abnormalities may occur throughout the GI tract, appendiceal Dieulafoy’s lesions are exceedingly rare, with described cases often resulting in surgical intervention. We present a case of a Dieulafoy’s lesion in the appendiceal orifice leading to massive GI bleeding which was successfully diagnosed and treated endoscopically. Case Description/Methods: A 75-year-old female with end stage renal disease, hypertension, hyperlipidemia, and heart failure with preserved ejection fraction presented with abdominal pain and rectal bleeding for 2 weeks duration. At onset, she was admitted to an outside hospital where computed tomography (CT) angiography showed aortoiliac and mesenteric atherosclerosis without evidence of large vessel occlusion. Esophagogastroduodenoscopy did not reveal a bleeding source. She reported infraumbilical abdominal pain and continued rectal bleeding and was transferred to our medical center. Upon arrival, the patient was hemodynamically stable with active rectal bleeding on exam. Laboratory analysis revealed hemoglobin of 6.9 grams per deciliter, platelet count of 101 per milliliter, blood urea nitrogen of 6.6 milligrams/deciliter (mg/dl), and creatinine of 6 mg/dl. She was treated with 3 units of packed red blood cell and a proton pump inhibitor. Colonoscopy showed a Dieulafoy’s lesion at the appendiceal orifice. Hemostasis was achieved with placement of 2 hemoclips (Figure). She was discharged 6 days after colonoscopy without recurrence of bleeding. Discussion: Only 6 cases of appendiceal Dieulafoy’s lesions have been reported in the literature and all were treated with laparoscopic appendectomy (Table 1). To our knowledge, this is the first reported case of an appendiceal Dieulafoy’s lesion that was successfully treated with endoscopic placement of hemoclips. There is no data comparing the efficacy of endoscopic intervention versus laparoscopic appendectomy in treating appendiceal Dieulafoy’s lesions; however, this case highlights that therapeutic endoscopy may be both safe and effective. Further reports are needed to inform recognition and optimal approach to appendiceal Dieulafoy’s lesions. Furthermore, in cases where hemostasis is achieved endoscopically, longer term follow-up may inform if appendectomy can be safely avoided.Figure 1.: Successful hemostasis of a Dieulafoy’s lesion at the appendiceal orifice after placement of 2 hemoclips. Table 1. - Previously reported Appendiceal Dieulafoy’s Lesions% and Outcomes Case Report Patient Clinical presentation and course Endoscopic hemostasis attempted? Management? Xue et al, 2020 21 F Massive hematochezia with lower abdominal pain and LOC* N Laparoscopic appendectomy Choi et al, 2016 72 M Hematochezia with associated mild abdominal pain and bloating sensation, previous melena from duodenal ulcer N Laparoscopic appendectomy and cecum wedge resection Johnson et al, 2014 51 M RLQ# pain, Acute appendicitis with incidental finding of Dieulafoy’s lesion on mid-distal appendiceal wall N Laparoscopic appendectomy Reynolds et al, 2013 68 M Massive hematochezia with perfusion requirement N Laparoscopic appendectomy Lee et al, 2011 22 M Severe lower GI† bleed N Laparoscopic appendectomy So et al, 1995 42 M Melena and dizziness N Laparoscopic appendectomy %In all previously reported cases, a Dieulafoy’s lesion was diagnosed using colonoscopy to visualize blood emerging from the appendiceal orifice, then subsequent resection revealing an ulcerated appendiceal mucosal lesion and microscopy and histopathology demonstrating tortuous vasculature penetrating the circumferential and longitudinal muscular wall of the appendix. Abbreviations: *Loss of consciousness, #Right lower quadrant, †Gastrointestinal.

Chinese Guideline for Percutaneous Coronary Intervention in Patients with Left Main Bifurcation Disease

The coronary left main (LM) artery is characterized by large caliber, length varying from <8 to >15 mm, and 2 large daughter vessels branching from it; it supplies blood to a large area (>75%) of the myocardium. LM bifurcation lesion is defined as the presence of atherosclerosis involving either or both of the 2 daughter vessels. Thus, the optimal strategy of revascularization for diseased LM has been an interesting research topic for a long time. With developments in percutaneous techniques, design, and materials of drug-eluting stents; intravascular imaging; new generation of antiplatelet medications; and particularly recent pooled evidence from randomized clinical trials comparing percutaneous coronary intervention with coronary artery bypass grafting, implantation of a drug-eluting stenting with or without other approved techniques is considered an important therapeutic approach for LM bifurcation lesions. Mirroring the anatomical complexity of the LM, stenting LM bifurcations is technically demanding, and intraprocedural complications can be catastrophic given the large amount of jeopardized myocardium. Therefore, the Chinese Society of Cardiology designed a writing committee with members from 3 working groups (ie, clinical research, intravascular imaging and physiology, and interventional cardiology) for the first time, to write a guideline on percutaneous treatment for LM bifurcation lesions, with view to improve the procedural quality and clinical outcomes. This guideline consists of introduction, anatomical description of the LM tree, risk stratification, strategies of revascularization, antiplatelet strategy, follow-up, and long-term management for patients with LM bifurcation lesions.

New approaches to achieving hemostasis after venous access in cardiovascular patients.

Recent decades have seen a series of advances in percutaneous transvenous procedures for cardiac arrhythmias, including the implantation of leadless pacemakers. Many of these procedures require the insertion of large caliber sheaths in large veins, usually the femoral vein. Securing hemostasis efficiently and reliably at the access site is a key step to improving a procedure's safety profile. Traditionally, hemostasis was achieved by manual compression of venous access sites, but the trend toward larger sheaths and the increased use of uninterrupted anticoagulation has pushed the limits of this method. Achieving hemostasis by compression alone in these circumstances requires more attention and longer duration, leading to greater patient discomfort and prolonged immobility. In turn, manual compression may be more time-consuming for medical professionals and increase the number of occupied hospital beds. New approaches have been developed to facilitate early ambulation, decrease patient discomfort, and address the risk of access site complications. These approaches include vascular closure devices and subcutaneous suture techniques including figureof- eight and purse-string sutures. This article reviews the new approaches applied to achieve venous access site hemostasis in patients undergoing transvenous procedures for cardiac arrhythmias.

658 The Use of AlliumTM Stents in the Management of Ureteric Strictures

Abstract Aim Stents are widely used in the management of ureteric strictures but require changes every 6–12 months and stent related symptoms are commonly reported. AlliumTM ureteric stents are large calibre, metallic stents that aim to reduce the incidence of stent-related complications, with an indwelling time up to three years. These were introduced within our local hospital trust for patients requiring frequent stent changes and this study aims to review the early use of AlliumTM stents and associated complications. Method An electronic database of patients was searched for records including the words “Allium stent” between 01/01/17–01/01/21. The resulting patient electronic records were then interrogated to extract data. Results 13 patients were included in data analysis. Mean age was 62.7 years and male:female ratio was 6:7. 5 underwent antegrade insertion and 8 retrograde. 3 were inserted under local anaesthetic and 10 under general. Median follow-up time was 459 days. No cases of renal deterioration were noted, and no patients sought medical attention with pain or irritative symptoms. The majority remained in situ, however one patient reported spontaneous passage of the stent; and one patient later required a nephrectomy, necessitating stent removal. Three patients developed post-operative urinary tract infections (two requiring hospital admission); two patients required further intervention for urolithiasis causing stent blockage; and two patients died from other disease processes prior to analysis. Conclusions There are clear advantages in reducing repeated admission and anaesthesia for patients. Initial results demonstrate good patency and tolerability of AlliumTM stents though further investigation is required to analyse the long-term benefits.

Applying machine learning for large scale field calibration of low‐cost PM2.5and PM10air pollution sensors

AbstractLow‐cost air quality monitoring networks can potentially increase the availability of high‐resolution monitoring to inform analytic and evidence‐informed approaches to better manage air quality. This is particularly relevant in low and middle‐income settings where access to traditional reference‐grade monitoring networks remains a challenge. However, low‐cost air quality sensors are impacted by ambient conditions which could lead to over‐ or underestimation of pollution concentrations and thus require field calibration to improve their accuracy and reliability. In this paper, we demonstrate the feasibility of using machine learning methods for large‐scale calibration of AirQo sensors, low‐cost PM sensors custom‐designed for and deployed in Sub‐Saharan urban settings. The performance of various machine learning methods is assessed by comparing model corrected PM usingk‐nearest neighbours, support vector regression, multivariate linear regression, ridge regression, lasso regression, elastic net regression, XGBoost, multilayer perceptron, random forest and gradient boosting with collocated reference PM concentrations from a Beta Attenuation Monitor (BAM). To this end, random forest and lasso regression models were superior for PM2.5and PM10calibration, respectively. Employing the random forest model decreased RMSE of raw data from 18.6 μg/m3to 7.2 μg/m3with an average BAM PM2.5concentration of 37.8 μg/m3while the lasso regression model decreased RMSE from 13.4 μg/m3to 7.9 μg/m3with an average BAM PM10concentration of 51.1 μg/m3. We validate our models through cross‐unit and cross‐site validation, allowing analysis of AirQo devices' consistency. The resulting calibration models were deployed to the entire large‐scale air quality monitoring network consisting of over 120 AirQo devices, which demonstrates the use of machine learning systems to address practical challenges in a developing world setting.

Reinforcement learning-based calibration method for cameras with large FOV

The accuracy of camera calibration is of great importance to vision measurements. Target-based calibration methods should cover the whole field of view (FOV), which leads to complex operation in large FOVs and rely on personal experiences. To overcome the difficulty in accurate calibration, a calibration method based on reinforcement learning is proposed. First, a Markov decision process (MDP) model of the calibration procedure is established. Then, the reward function is designed, combining the requirement of calibration accuracy and the state-space constraint. Finally, the optimized target locations and poses are obtained by continuous interaction with the calibration environment based on Q-learning, which plays a key guiding role in camera calibration. Simulation experiments and real experiments are performed, which indicate that the proposed method effectively improves the success rate of large FOV camera calibration, and solves the problems of relying on personal experiences, low calibration accuracy, and poor stability caused by target placement in the camera calibration process.

The Superthin Profunda artery perforator flap for Extremity Reconstruction: Clinical Implications

The profunda artery perforator flap has numerous advantages. For coverage of extremity wounds, however, traditional subfascial harvest results in a thick flap, which routinely requires secondary thinning. The author describes his approach and experience with thin and superthin profunda artery perforator flaps for extremity reconstruction. With preoperative perforator localization via computed tomography angiogram, color Doppler, and handheld Doppler, the author used a single dominant perforator for extremity reconstruction in 10 consecutive patients. The mean age of patients who had a thin or superthin profunda artery perforator flap for extremity reconstruction was 41.2 ± 21.3 years. Flaps were used to cover wounds in the upper ( n = 3) and lower ( n = 7) extremities. Mean flap thickness was 0.7 ± 0.2 cm. Mean flap artery diameter was 16 ± 3 mm; mean flap vein diameter was 21 ± 6 mm. Mean pedicle length was 6.8 ± 1.2 cm. The difference between the actual measured intraoperative proximal-distal distance and the preoperative computed tomography angiogram measurement for each patient was calculated, with a mean difference of 1.2 ± 0.6 cm. Advantages of the profunda artery perforator flap include a concealed donor site, large perforator caliber, long pedicle length, and a straightforward perforator dissection. Intraoperative measurement of the proximal-distal distance of the dominant perforator fell within 2 cm of the preoperative computed tomography angiogram measurement in all cases. The thin and superthin profunda artery perforator flaps provide new reconstructive options, particularly suited for use in the extremities. Therapeutic, IV.