Design Concept for Key Parameters of Reverse Conducting GCT

Presented is design concept for key parameters o f the reverse conducting gate commutated thyristor (RC-GCT),such as the thickness and concentration of n-base region and the transparent anode region,and the wi dth of separation region between asymmetric GCT and PIN diode.A structure model of the RC-GCT is set up based on the design concept and its characteristics are analyzed.The simulation results show the design concept is reasonable.

Monitoring of ducting by using a ground-based GPS receiver

In this paper,we describe the estimation of low-altitude refractivity structure from simulation and real ground-based GPS delays.The vertical structure of the refractive environment is modeled using three parameters,i.e.,duct height,duct thickness,and duct slope.The refractivity model is implemented with a priori constraints on the duct height,thickness,and strength,which might be derived from soundings or numerical weather-prediction models.A ray propagation model maps the refractivity structure into a replica field.Replica fields are compared with the simulation observed data using a squarederror objective function.A global search for the three environmental parameters is performed using a genetic algorithm.The inversion is assessed by comparing the refractivity profiles from the radiosondes to those estimated.This technique could provide near-real-time estimation of the ducting effect.The results suggest that ground-based GPS provides significant atmospheric refractivity information,despite certain fundamental limitations of ground-based measurements.Radiosondes are typically launched just a few times daily.Consequently,estimates of temporally and spatially varying refractivity that assimilate GPS delays could substantially improve over-estimates caused by using radiosonde data alone.

Estimation of co-channel interference between cities caused by ducting and turbulence

With the rapid development of the fifth-generation(5 G)mobile communication technology,the application of each frequency band has reached the extreme,causing mutual interference between different modules.Hence,there is a requirement for detecting filtering and preventing interference.In the troposphere,over-the-horizon propagation occurs in atmospheric ducts and turbulent media.The effects of both ducting and turbulence can increase the probability of occurrence of long-distance co-channel interference(CCI),in turn,severely affecting the key performance indicators such as system access,handover and drop.In the 5 G era,to ensure communication channels and information security,CCI must be reduced.This paper introduces a scattering parabolic equation algorithm for calculating signal propagation in atmospheric ducts on irregular terrain boundaries.It combines Hitney’s radio physical optical model and Wagner’s nonuniform turbulent scattering model for calculating the tropospheric scattering in an evaporation duct or a surface-based duct.The new model proposes a tropospheric scattering parabolic equation algorithm for various tropospheric duct environments.Finally,as a specific case,the topographical boundaries between several cities in the East China Plain were considered,and the over-the-horizon propagation loss was simulated for various ducting and turbulent environments.The simulation results were used to evaluate whether CCI would occur between cities in a specific environment.

Atmospheric Ducting Effect in Wireless Communications:Challenges and Opportunities

Atmospheric ducting has a significant impact on electromagnetic wave propagation.Radio signals that are trapped and guided by the atmospheric duct can travel a much longer distance over the horizon with lower attenuation since the signal power does not spread isotropically through the atmosphere.Atmospheric ducting brings both challenges and opportunities to wireless communications.On one hand,the signals propagating in the atmospheric duct may interfere with a receiver far away as remote co-channel interference.On the other hand,a point-to-point link can be established directly through the atmospheric duct to enable beyond line-of-sight communications.In this article,the formation of the atmospheric duct and its effects on radio wave propagation are first overviewed.Then solutions and standardization activities in the 3rd Generation Partnership Project(3GPP)to mitigate atmospheric duct induced remote interference are presented.Finally,the applications and design challenges of atmospheric duct enabled beyond line-of-sight communications are reviewed and future research directions are suggested.

Risk factors for congenital nasolacrimal duct obstruction in children under two years of age

·AIM:To identify various risk factors that may play a significant role in the development of congenital nasolacrimal duct obstruction(CNLDO).·METHODS:This observational case-control study included a case group of 122 children less than two years of age with CNLDO who underwent probing and irrigation treatment at the ophthalmology department of Imam Khomeini Hospital in Ahvaz,Iran,from June 2022 to June2024.A control group of 122 age-matched children without CNLDO was also included for comparison.Data was collected from the children's medical records.·RESULTS:The study found a significant correlation between the occurrence of CNLDO and several maternal factors,such as preeclampsia,the use of levothyroxine,hypothyroidism,having more than three pregnancies(gravidity>3),natural pregnancy,and gestational diabetes mellitus.Additionally,in children,factors,such as oxygen therapy,anemia,reflux,jaundice,and a family history of CNLDO in first-degree relatives were associated with CNLDO,and maternal preeclampsia and hypothyroidism were found to significantly increase the risk of developing CNLDO in children.·CONCLUSION:Given that CNLDO affects both premature and full-term children,the present findings may potentially facilitate the early identification of children and infants at risk of nasolacrimal duct obstruction,thereby preventing the onset of chronic dacryocystitis.

Effect of cholesterol metabolism on hepatolithiasis

Surgical intervention is currently the primary treatment for hepatolithiasis;how-ever,some patients still experience residual stones and high recurrence rates after surgery.Cholesterol metabolism seems to play an important role in hepatoli-thiasis pathogenesis.A high cholesterol diet is one of the significant reasons for the increasing incidence of hepatolithiasis.Therefore,regular diet and appropriate medical intervention are crucial measures to prevent hepatolithiasis and reduce recurrence rate after surgery.Reducing dietary cholesterol and drugs that increase cholesterol stone solubility are key therapeutic approaches in treating hepato-lithiasis.This article discusses the cholesterol metabolic pathways related to the pathogenesis of hepatolithiasis,as well as food intake and targeted therapeutic drugs.

Practice patterns among ophthalmic surgeons in treating concomitant oculoplastic conditions in preoperative period:A questionnaire-based study

BACKGROUND Addressing oculoplastic conditions in the preoperative period ensures both the safety and functional success of any ophthalmic procedure.Some oculoplastic conditions,like nasolacrimal duct obstruction,have been extensively studied,whereas others,like eyelid malposition and thyroid eye disease,have received minimal or no research.AIM To investigate the current practice patterns among ophthalmologists while treating concomitant oculoplastic conditions before any subspecialty ophthalmic intervention.METHODS A cross-sectional survey was disseminated among ophthalmologists all over India.The survey included questions related to pre-operative evaluation,anaesthetic and surgical techniques preferred,post-operative care,the use of adjunctive therapies,and patient follow-up patterns.RESULTS A total of 180 ophthalmologists responded to the survey.Most practitioners(89%)felt that the ROPLAS test was sufficient during pre-operative evaluation before any subspecialty surgery was advised.The most common surgical techniques employed were lacrimal drainage procedures(Dacryocystorhinostomy)(63.3%),eyelid malposition repair(36.9%),and ptosis repair(58.7%).Post-operatively,47.7%of respondents emphasized that at least a 4-week gap should be maintained after lacrimal drainage procedures and eyelid surgeries.Sixty-seven percent of ophthalmologists felt that topical anaesthetic procedures should be preferred while performing ocular surgeries in thyroid eye disease patients.CONCLUSION Approximately 50%of ophthalmologists handle prevalent oculoplastic issues themselves,seeking the expertise of an oculoplastic surgeon under particular conditions.Many ophthalmologists still favor using ROPLAS as a preliminary screening method before proceeding with cataract surgery.Eyelid conditions and thyroid eye disease are not as commonly addressed before subspecialty procedures compared to issues like nasolacrimal duct obstruction and periocular infections.

Maintenance and Sudden Change of a Strong Elevated Ducting Event Associated with High Pressure and Marine Low-Level Jet

Capture of a strong elevated ducting event,especially its maintenance and sudden change,is of great value to airborne radar to achieve its beyond-the-line-of-sight detection.However,the knowledge is not easily accessible over the open ocean and hence very rare.During the Air–Sea Interaction Survey(ASIS)over the western North Pacific(WNP)in May 2016,a strong elevated ducting event with a long-life period and sudden change in its evolution was observed.Measurements from the ASIS,images from the Himawari-8 satellite,reanalysis data from the ECMWF,and Weather Research and Forecasting(WRF)model,were used to analyze the maintenance and sudden change of this strong ducting event,together with the model performance on simulating it.The results showed that the maintenance of strong elevated ducts,with their tops ranging from 750 to 1050 m and average strength of approximately 38 M units,was caused by a strong dry air mass capping over the wet marine atmospheric boundary layer(MABL),together with the subsidence inversion associated with high pressure.The WRF model performs well in simulating them.However,a sudden increase in duct height with a slight decrease of strength was recorded by the subsequent GPS radiosonde,which was finally contributed to the mechanical turbulent inversion and hydrolapse associated with the marine low-level jet(MLLJ).The height of the maximum horizontal wind speed(Umh)of the MLLJ corresponds well with the bottom of the trapping layer.However,these jet-relevant ducts are generally weak and it is difficult to accurately simulate them by using the mesoscale numerical model,since the wind-shear produced eddies are too small to be properly parameterized.

Heat stress alleviation for dairy cows housed in an open-sided barn by cooling fan and perforated air ducting(PAD)system

Curtain-sided barns with circulation fans above stall are commonly used to house dairy cows in China.Many farms equipped with circulation fans are unable to provide appropriate cooling,especially for the naturally ventilated shed,which can result in decreasing feed intake and milk production.For alleviating heat stress and improving animal comfort,a system consisting of an air cooler and a 30 m perforated air duct(PAD)was integrated to evenly distribute cooling air.The air was cooled by underground water and delivered to targeted zones above stall bed.The system was evaluated in an open sided dairy barn in Tianjin,China.For the stalls equipped with PAD system,air velocity reached above 1.1 m/s at 0.5 m height plane of the stall space,and was more uniformly distributed.Compared to the stalls equipped with circulation fans,the PAD system lowered air temperature by 1.5℃,and increased relative humidity by 8.1%.On average,Temperature Humidity Index(THI)and Equivalent Temperature Index(ETI)were decreased by 0.5 and 0.6,respectively.After a 15 days’operation of the system,rectal temperatures of the treated dairy cows were significantly lowered.The results also showed that the cows under PADs had a higher milk production.These findings suggest the PAD can be an effective cooling alternative for naturally ventilated dairy barns to alleviate heat stress.

Removal of intrahepatic bile duct stone could reduce the risk of cholangiocarcinoma

Hepatolithiasis(HL)poses a significant risk for cholangiocarcinoma(CCA)development,with reported incidences ranging from 5%-13%.Risk factors include older age,smoking,hepatitis B infection,and prolonged HL duration.Chronic inflammation and mechanical stress on the biliary epithelium contribute to CCA pathogenesis.Hepatectomy reduces CCA risk by removing stones and atrophic liver segments.However,residual stones and incomplete removal increase CCA risk.Kim et al identified carbohydrate antigen 19-9,carcinoembryonic antigen,and stone laterality as CCA risk factors,reaffirming the importance of complete stone removal.Nonetheless,challenges remain in preventing CCA recurrence post-surgery.Longer-term studies are needed to elucidate CCA risk factors further.

Response letter to “Acute cholangitis: Does malignant biliary obstruction vs choledocholithiasis etiology change the outcomes?” with imaging aspects

Radiological imaging findings may contribute to the differentiation of malignant biliary obstruction from choledocholithiasis in the etiology of acute cholangitis.

Removal of intrahepatic bile duct stone could reduce the risk of cholangiocarcinoma: A single-center retrospective study in South Korea

BACKGROUND Intrahepatic duct(IHD)stones are among the most important risk factors for cholangiocarcinoma(CCC).Approximately 10%of patients with IHD stones develop CCC;however,there are limited studies regarding the effect of IHD stone removal on CCC development.AIM To investigate the association between IHD stone removal and CCC development.METHODS We retrospectively analyzed 397 patients with IHD stones at a tertiary referral center between January 2011 and December 2020.RESULTS CCC occurred in 36 of the 397 enrolled patients.In univariate analysis,chronic hepatitis B infection(11.1%vs 3.0%,P=0.03),carbohydrate antigen 19-9(CA19-9,176.00 vs 11.96 II/mL,P=0.010),stone located in left or both lobes(86.1%vs 70.1%,P=0.042),focal atrophy(52.8%vs 26.9%,P=0.001),duct stricture(47.2%vs 24.9%,P=0.004),and removal status of IHD stone(33.3%vs 63.2%,P<0.001)were significantly different between IHD stone patients with and without CCC.In the multivariate analysis,CA19-9>upper normal limit,carcinoembryonic antigen>upper normal limit,stones located in the left or both lobes,focal atrophy,and complete removal of IHD stones without recurrence were independent factors influencing CCC development.However,the type of removal method was not associated with CCC risk.CONCLUSION Complete removal of IHD stones without recurrence could reduce CCC risk.

Percutaneous transhepatic cholangioscopy-assisted biliary polypectomy for local palliative treatment of intraductal papillary neoplasm of the bile duct

BACKGROUND Intraductal papillary neoplasm of the bile duct(IPNB)is a premalignant biliarytype epithelial neoplasm with intraductal papillary or villous growth.Currently reported local palliative therapeutic modalities,including endoscopic nasobiliary drainage,stenting and biliary curettage,endoscopic biliary polypectomy,percutaneous biliary drainage,laser ablation,argon plasma coagulation,photodynamic therapy,and radiofrequency ablation to relieve mechanical obstruction are limited with weaknesses and disadvantages.We have applied percutaneous transhepatic cholangioscopy(PTCS)-assisted biliary polypectomy(PTCS-BP)technique for the management of IPNB including mucin-hypersecreting cast-like and polypoid type tumors since 2010.AIM To assess the technical feasibility,efficacy,and safety of PTCS-BP for local palliative treatment of IPNB.METHODS Patients with mucin-hypersecreting cast-like or polypoid type IPNB and receiving PTCS-BP between September 2010 and December 2019 were included.PTCS-BP was performed by using a half-moon type snare with a soft stainless-steel wire,and the tumor was snared and resected with electrocautery.The primary outcome was its feasibility,indicated by technical success.The secondary outcomes were efficacy,including therapeutic success,curative resection,and clinical success,and safety.RESULTS Five patients(four with mucin-hypersecreting cast-like type and one with polypoid type IPNB)were included.Low-and high-grade intraepithelial neoplasia(HGIN)and recurrent IPNB with invasive carcinoma were observed in one,two,and two patients,respectively.Repeated cholangitis and/or obstructive jaundice were presented in all four patients with mucin-hypersecreting cast-like type IPNB.All five patients achieved technical success of PTCS-BP.Four patients(three with mucin-hypersecreting cast-like type and one with polypoid type IPNB)obtained therapeutic success;one with mucin-hypersecreting cast-like type tumors in the intrahepatic small bile duct and HGIN had residual tumors.All four patients with mucin-hypersecreting IPNB achieved clinical success.The patient with polypoid type IPNB achieved curative resection.There were no PTCS-BP-related serious adverse events.CONCLUSION PTCS-BP appears to be feasible,efficacious,and safe for local palliative treatment of both mucin-hypersecreting cast-like and polypoid type IPNB.

Hem-o-lok clip migration to duodenal bulb post-cholecystectomy:A case report

BACKGROUND Hem-o-lok clips are typically used to control the cystic duct and vessels during laparoscopic cholecystectomy(LC)and common bile duct exploration for stones in the bile duct and gallbladder.Here,we report a unique example of Hem-o-lok clip movement towards the duodenal bulb after LC,appearing as a submucosal tumor(SMT).Additionally,we provide initial evidence of gradual and evolving endoscopic manifestations of Hem-o-lok clip migration to the duodenal bulb wall and review the available literature.CASE SUMMARY A 72-year-old man underwent LC for gallstones,and Hem-o-lok clips were used to ligate both the cystic duct and cystic artery.Esophagogastroduodenoscopy(EGD)2 years later revealed an SMT-like lesion in the duodenal bulb.Due to the symptomatology,the clinical examination did not reveal any major abnormalities,and the patient was followed up as an outpatient.A repeat EGD performed 5 months later revealed an SMT-like lesion in the duodenal bulb with raised edges and a central depression.A third EGD was conducted,during which a Hem-o-lok clip was discovered connected to the front side of the duodenum.The clip was extracted easily using biopsy forceps,and no complications occurred.Two months after the fourth EGD,the scar was surrounded by normal mucosa.CONCLUSION Clinicians should be aware of potential post-LC complications.Hem-o-lok clips should be removed if symptomatic.

Undifferentiated high-grade pleomorphic sarcoma of the common bile duct:A case report and review of literature

BACKGROUND Undifferentiated pleomorphic sarcoma(UPS)is a rare malignant mesenchymal tumor with a poor prognosis.It mainly occurs in the extremities,trunk,head and neck,and retroperitoneum regions.Owing to the lack of specific clinical manifestations and imaging features,UPS diagnosis mainly depends on pathological and immunohistochemical examinations for exclusive diagnosis.Here we report an extremely rare case of high-grade UPS in the common bile duct(CBD).There are limited available data on such cases.CASE SUMMARY A 70-year-old woman was admitted to our department with yellow eyes and urine accompanied by upper abdominal distending pain for 2 wk.Her laboratory data suggested significantly elevated hepatorenal function levels.The imaging data revealed calculous cholecystitis,intrahepatic and extrahepatic bile duct dilation with extrahepatic bile duct calculi,and a space-occupying lesion at the distal CBD.After endoscopic biliary stenting and symptomatic support therapy,CBD exploration and biopsy were performed.The frozen section indicated malignant spindle cell tumor of the CBD mass,and further radical pancreaticoduodenectomy was performed.Finally,the neoplasm was diagnosed as a high-grade UPS combined with the light-microscopic morphology and immunohistochemical results.CONCLUSION This extremely rare case highlighted the need for increasing physicians'vigilance,reducing the odds of misdiagnosis,and providing appropriate treatment strategies.

Mirizzi syndrome:Problems and strategies

Mirizzi syndrome is a serious complication of gallstone disease.It is caused by the impacted stones in the gallbladder neck or cystic duct.One of the features of Mirizzi syndrome is severe inflammation or dense fibrosis at the Calot’s triangle.In our clinical practice,bile duct,branches of right hepatic artery and right portal vein clinging to gallbladder infundibulum are often observed due to gallbladder infundibulum adhered to right hepatic hilum.The intraoperative damage of branches of right hepatic artery occurs more easily than that of bile duct,all of which are hidden pitfalls for surgeons.Magnetic resonance cholangiopancreatography(MRCP)and endoscopic retrograde cholangiopancreatography(ERCP)are the preferable tools for the diagnosis of Mirizzi syndrome.Anterograde cholecystectomy in Mirizzi syndrome is easy to damage branches of right hepatic artery and bile duct due to gallbladder infundibulum adhered to right hepatic hilum.Subtotal cholecystectomy is an easy,safe and definitive approach to Mirizzi syndrome.When combined with the application of ERCP,a laparoscopic management of Mirizzi syndrome by well-trained surgeons is feasible and safe.The objective of this review was to highlight its existing problems:(1)low preoperative diagnostic rate,(2)easy to damage bile duct and branches of right hepatic artery,and(3)high concomitant gallbladder carcinoma.Meanwhile,the review aimed to discuss the possible therapeutic strategies:(1)to enhance its preoperative recognition by imaging findings,and(2)to avoid potential pitfalls during surgery.

Diseases of bile duct in children

Several diseases originate from bile duct pathology.Despite studies on these diseases,certain etiologies of some of them still cannot be concluded.The most common disease of the bile duct in newborns is biliary atresia,whose prognosis varies according to the age of surgical correction.Other diseases such as Alagille syndrome,inspissated bile duct syndrome,and choledochal cysts are also time-sensitive because they can cause severe liver damage due to obstruction.The majority of these diseases present with cholestatic jaundice in the newborn or infant period,which is quite difficult to differentiate regarding clinical acumen and initial investigations.Intraoperative cholangiography is potentially necessary to make an accurate diagnosis,and further treatment will be performed synchronously or planned as findings suggest.This article provides a concise review of bile duct diseases,with interesting cases.

A Review of Type 1 and Type 2 Intraductal Papillary Neoplasms of the Bile Duct

Intraductal papillary neoplasm of the bile duct(IPNB)is a heterogeneous disease similar to intraductal papillary mucinous neoplasm of the pancreas.These lesions have been recognized as one of the three major precancerous lesions in the biliary tract since 2010.In 2018,Japanese and Korean pathologists reached a consensus,classifying IPNBs into type l and type 2 IPNBs.IPNBs are more prevalent in male patients in East Asia and are closely related to diseases such as cholelithiasis and schistosomiasis.From a molecular genetic perspective,IPNBs exhibit early genetic variations,and different molecular pathways may be involved in the tumorigenesis of type 1 and type 2 IPNBs.The histological subtypes of IPNBs include gastric,intestinal,pancreaticobiliary,or oncocytic subtypes,but type 1 IPNBs typically exhibit more regular and well-organized histological features than type 2 IPNBs and are more commonly found in the intrahepatic bile ducts with abundant mucin.Due to the rarity of these lesions and the absence of specific clinical and laboratory features,imaging is crucial for the preoperative diagnosis of IPNB,with local bile duct dilation and growth along the bile ducts being the main imaging features.Surgical resection remains the optimal treatment for IPNBs,but negative bile duct margins and the removal of lymph nodes in the hepatic hilum significantly improve the postoperative survival rates for patients with IPNBs.

Nasal flap preservation in endoscopic dacryocystorhinostomy for nasolacrimal duct obstruction

AIM:To compare surgical outcomes between the conventional endoscopic dacryocystorhinostomy(DCR)and a modified endoscopic DCR for the treatment of nasolacrimal duct obstruction(NLDO),and evaluate factors associated with the surgical success rate.METHODS:Medical records of patients who underwent primary DCR surgery between January 2016 and July 2020 at the Otorhinolaryngology Department of Eye and Ear International Hospital,Lebanon were reviewed.RESULTS:The study group consisted of 50 consecutive modified endoscopic DCR and the control group consisted of 138 consecutive conventional endoscopic DCR.The success rates at 1y were 98.0%(49 out of 50)for modified DCR,significantly higher compared to 84.8%(117/138)for the conventional DCR;there was no significant difference in the success rate throughout the years in terms of both surgical techniques.The modified surgery vs traditional[adjusted odds ratio(aOR)=14.96]and having an adjunctive septoplasty surgery vs not(aOR=3.99)were significantly associated with higher odds of success.CONCLUSION:Mucosal flap preservation and apposition shows significant improvement in the surgical success rate.Moreover,there is no statistically significant difference found in terms of complication rate and mean operative time between the conventional and the modified techniques.

Is there a place for endoscopic management in postcholecystectomy iatrogenic bile duct injuries?

In this editorial we comment on the article by Emara et al published in the recent issue of the World Journal of Gastrointestinal Surgery.Previously,surgery was the primary treatment for bile duct injuries(BDI).The treatment of BDI has advanced due to technological breakthroughs and minimally invasive procedures.Endoscopic and percutaneous treatments have largely supplanted surgery as the primary treatment for most instances in recent years.Patient management,including the specific technique,is typically impacted by local knowledge and the kind and severity of the injury.Endoscopic therapy is a highly successful treatment for postoperative benign bile duct stenosis and offers superior long-term outcomes compared to surgical correction.Based on the damage features of BDI,therapeutic options include endoscopic duodenal papillary sphincterotomy,endoscopic nasobiliary drainage,and endoscopic biliary stent implantation.