Multi-Scale Organization of the Doumbouo-FokouéBauxites Ore Deposits (West Cameroon): Implication to the Landscape Lowering

Landscape distribution, macroscopic, microscopic, mineral and geochemical characterizations were conducted on the Doumbouo-Fokoué bauxite ore deposit in order to estimate bauxites potential and its implication to general lowering of the relief. Fourteen bauxitic plateaus covering a surface area of 5.7 km2 were identified. Bauxitic pedons show deep weathered profiles (10.0 - 12.0 m) with thick bauxitic mantle (4.0 - 8.0 m). Saprolite and pisolith bauxitic facies own high aluminium (47.5% - 49.5% Al2O3), relatively low iron (20.0% - 22.0% Fe2O3) and low silica contents (1.8% - 7.6% SiO2). Gibbsite is the dominant mineral (49% - 68% of minerals detected by X-ray);meanwhile hematite, goethite and kaolinite occur in small amounts. Bauxitization corresponds to intense allitization with abundant accumulation of gibbsite and development of lateritic iron bearing ortho-bauxites. Bauxite ores yielded bauxite reserves of 9.2 million tons. They occur as old and residual bauxitic mantles representing remnants of the Miocene residual lateritic deposits in West Cameroon referring to the African surface of Valeton [1]. Its mean altitude (1532 - 1590 m als) below the African surface reveals general lowering of the relief.

Isolation of an acid producing Bacillus sp. EEEL02: Potential for bauxite residue neutralization

Bauxite residue deposit area(BRDA)is a typical abandoned mining wasteland representing extreme hostile environment with increased alkalinity.Microbially-driven neutralization of bauxite residue,based on the microbial acid producing metabolisms,is a novel strategy for achieving rapid pH neutralization and thus improving its environmental outcomes.The hypothesis was that these extreme conditions promote microbial communities which are capable of novel ecologically relevant functions.Several alkaliphilic acid producing bacteria were isolated in this study.One strain was selected for its superior growth pattern and acid metabolism(termed EEEL02).Based on the phylogenetic analysis,this strain was identified as Bacillus thuringiensis.The optimized fermentation conditions were as follows:pH 10;NaCl concentration 5%;temperature 25℃;EEEL02 preferred glucose and peptone as carbon and nitrogen sources,respectively.Based on optimal fermentation conditions,EEEL02 induced a significant pH reduction from 10.26 to 5.62 in 5-day incubation test.Acetic acid,propionic acid and CO2(g)were the major acid metabolites of fermentation,suggesting that the pH reduction in bauxite residue may be caused by acid neutralization derived from microbial metabolism.This finding provided the basis of a novel strategy for achieving rapid pH neutralization of bauxite residue.

Creation of "Regional Characteristic" in Planning and Design of Farmers' Residential Area at the South of Lower Reaches of the Yangtze River

After analysis of location feature of the south of lower reaches of Yangtze River and its construction of urban and rural integration,the paper pointed out harmonious combination between natural and artificial factors had been neglected in planning and design of farmers' residential area at the south of lower reaches of Yangtze River,"regional characteristic" losing,residential area in the form of "city community" and buildings in European style.In view of these problems,relevant planning and design thoughts and methods had been proposed as to how to create "regional characteristic" from the perspective of planning,architecture and landscape design.It discussed with emphasis the importance of construction base type and combination of environment with residential area construction;inspirations and design methods obtained from traditional architectures;and the content of landscape overall planning and specific design.It was hoped to enlighten designers to shoulder social and historical responsibility,make exploration unremittingly,and construct beautiful homelands for people.

Successful endovascular treatment in patients with acute thromboembolic ischemia of the lower limb including the crural arteries

AIM To examine the efficacy and safety of the 6 French(6F) Rotarex~S catheter system in patients with acute limb ischemia(ALI) involving thromboembolic occlusion of the proximal and mid-crural vessels.METHODS The files of patients in our department with ALI between 2015 and 2017 were examined. In seven patients, the Rotarex~S catheter was used in the proximal segment of the crural arteries. Data related to the clinical examination, Doppler sonography, angiography and followup from these patients were further used for analysis.RESULTS Two patients(29%) had thrombotic occlusion of the common femoral artery, and the remaining five exhibited thrombosis of the superficial femoral artery and popliteal artery. Mechanical thrombectomy was performed in all cases using a 6F Rotarex~S catheter. Additional Rotarex~S catheter thrombectomy due to remaining thrombus formation with no reflow was performed in the anterior tibial artery in two of seven cases(29%), in the tibiofibular tract and posterior tibial artery in two of seven cases(29%) and in the tibiofibular tract and fibular artery in the remaining three of seven cases(43%). Ischemic symptoms resolved promptly in all, and none of the patients experienced a procedural complication, such as crural vessel dissection, perforation or thrombus embolization.CONCLUSION Mechanical debulking using the 6F Rotarex~S catheter system may be a safe and effective treatment option in case of thrombotic or thromboembolic occlusion of the proximal and mid-portion of crural arteries.

Inverted Meckel's diverticulum as a cause of occult lower gastrointestinal hemorrhage

Meckel's diverticulum is a common asymptomatic congenital gastrointestinal anomaly,but rarely it can present with hemorrhage.Over the last few years inverted Meckel's diverticulum has been reported in the literature with increasing frequency as an occult source of lower gastrointestinal hemorrhage.Here,we report a case of a 54-year-old male,who was referred for surgical evaluation with persistent anemia and occult blood per rectum after a work up which failed to localize the source over 12 mo,including upper and capsule endoscopy,colonoscopy,enteroclysis,Meckel scan,and tagged nuclear red blood cell scan.An abdominal computed tomography scan showed a possible mid-ileal intussusception and intraluminal mass.During the abdominal exploration,inverted Meckel's diverticulum was diagnosed and resected.We review the literature,discuss the forms in which the disease presents,the diagnostic modalities utilized,pathological findings,and treatment.Although less than 40 cases have been reported in the English literature from 1978 to 2005,19 cases have been reported in the last 6 years alone(2006-2012) due to improved diagnostic modalities.Successful diagnosis and treatment of this disease requires a high index of clinical suspicion,which is becoming increasingly relevant to general gastroenterologists.

ON THE LOWER BOUND FOR A CLASS OF HARMONIC FUNCTIONS IN THE HALF SPACE

The main objective is to derive a lower bound from an upper one for harmonic functions in the half space, which extends a result of B. Y. Levin from dimension 2 to dimension n 〉 2. To this end, we first generalize the Carleman＇s formula for harmonic functions in the half plane to higher dimensional half space, and then establish a Nevanlinna＇s representation for harmonic functions in the half sphere by using HSrmander＇s theorem.

Thoracoscopic resection of a large lower esophageal schwannoma:A case report and review of the literature

BACKGROUND Esophageal schwannomas originating from Schwann cells are extremely rare esophageal tumors.They commonly occur in the upper and middle esophagus but less frequently in the lower esophagus.Herein,we report a rare case of a large lower esophageal schwannoma misdiagnosed as a leiomyoma.We also present a brief literature review on lower esophageal schwannomas.CASE SUMMARY A 62-year-old man presented with severe dysphagia lasting 6 mo.A barium esophagogram showed that the lower esophagus was compressed within approximately 5.5 cm.Endoscopy revealed the presence of a large submucosal protuberant lesion in the esophagus at a distance of 32-38 cm from the incisors.Endoscopic ultrasound findings demonstrated a 4.5 cm×5.0 cm hypoechoic lesion.Chest computed tomography revealed a mass of size approximately 53 mm×39 mm×50 mm.Initial tests revealed features indicative of leiomyoma.After multidisciplinary discussions,the patient underwent a video-assisted thoracoscopic partial esophagectomy.Further investigation involving immunohistochemical examination confirming palisading spindle cells as positive for S100 and Sox10 led to the final diagnosis of a lower esophageal schwannoma.There was no tumor recurrence or metastasis during follow-up.CONCLUSION The final diagnosis of esophageal schwannoma requires histopathological and immunohistochemical examination.The early appropriate surgery favors a remarkable prognosis.

Risk factors and prognostic value of acute severe lower gastrointestinal bleeding in Crohn’s disease

BACKGROUND Acute severe lower gastrointestinal bleeding(LGIB)is an uncommon but challenging complication of Crohn’s disease(CD).AIM To identify the predictors of acute severe LGIB and to evaluate the impact of acute severe LGIB on the subsequent clinical course in CD patients.METHODS A retrospective inception cohort study was conducted in 75 CD patients with acute severe LGIB and 1359 CD patients without acute severe LGIB who were diagnosed between February 1991 and November 2019 at Asan Medical Center,a tertiary university hospital in Korea.Multivariable analysis with Cox proportional hazard regression was performed to identify the risk factors for acute severe LGIB.A matched analysis using 72 patients with bleeding and 267 matched patients without within the cohort was also conducted to investigate whether acute severe LGIB is a predictor of clinical outcomes of CD.RESULTS Multivariable Cox regression analysis revealed that early use of thiopurines[hazard ratio(HR):0.23,95%confidence interval(CI):0.12-0.48;P<0.001]and female sex(HR:0.51,95%CI:0.27-0.94;P=0.031)were significantly associated with a lower risk of acute severe LGIB.The cumulative risks of behavioral progression and intestinal resection were not significantly different between the two matched groups(P=0.139 and P=0.769,respectively).The hospitalization rate was higher in the bleeding group than in the matched non-bleeding group(22.1/100 vs 13.2/100 patient-years;P=0.012).However,if hospitalizations due to bleeding episodes were excluded from the analysis,the hospitalization rate was not significantly different between the bleeding group and the matched nonbleeding group(14.5/100 vs 13.2/100 patient-years;P=0.631).CONCLUSION Early use of thiopurines may reduce the risk of acute severe LGIB.History of acute severe LGIB may not have a significant prognostic value in patients with CD.

Kaposi’s sarcoma manifested as lower gastrointestinal bleeding in a HIV/HBV-co-infected liver cirrhosis patient: A case report

BACKGROUND Kaposi’s sarcoma(KS)is one of the most common cancers in human immunodeficiency virus(HIV)-positive patients and leads to a high prevalence of morbidity and mortality.It usually appears as cutaneous or mucous lesions.Patients with visceral KS are asymptomatic and clinically silent.As the disease advances,patients may progress from a normal condition to exhibiting severe symptoms.CASE SUMMARY A 27-year-old man presented with a 2-mo history of fever,bearing-down pain,and rectal bleeding.His hepatitis B virus DNA level was 2.7×107 IU/mL.Abdominal computed tomography(CT)indicated liver cirrhosis.Before he was admitted to our hospital,he was diagnosed with HIV infection.His CD4 count was 24 cells/μL.Pelvic cavity CT suggested a thickened rectum wall accompanied by multiple enlarged lymph nodes.The patient was initially treated as having haemorrhoidal varices with bleeding,telbivudine for anti-hepatitis B virus treatment,and antibiotics for anti-infection.After half a month of treatment,the patient felt that his lower lumbus ache and bearing-down pain had not improved,and a colonoscopy was conducted.The result revealed a rectal mass that was histologically confirmed as KS with rectal spindle cells that were positive for cluster of differentiation 117(CD117),CD34,human herpes virus 8,and CD31.He was administered systemic chemotherapy with 36 mg/d liposomal doxorubicin six times.The patient experienced no sign of lower gastrointestinal bleeding again.CONCLUSION This case highlights the diagnosis of primary KS with lower gastrointestinal bleeding in HIV-positive patients,which means visceral KS could not be excluded.The gold standard relies on colonoscopy and biopsy findings.

Accelerated Infliximab Induction for Severe Lower Gastrointestinal Bleeding in a Young Patient with Crohn’s Disease:A Case Report

BACKGROUND Severe lower gastrointestinal bleeding(SLGIB)is a rare complication of Crohn's disease(CD).The treatment of these patients is a clinical challenge.Monoclonal anti-TNFαantibody(IFX)can induce relatively fast mucosal healing.It has been reported for the treatment of SLGIB,but there are few reports on accelerated IFX induction in CD patients with SLGIB.CASE SUMMARY A 16-year-old boy with a history of recurrent oral ulcers for nearly 1 year presented to the Gastroenterology Department of our hospital complaining of recurrent periumbilical pain for more than 1 mo and having bloody stool 4 times within 2 wk.Colonoscopy showed multiple areas of inflammation of the colon and a sigmoid colon ulcer with active bleeding.Hemostasis was immediately performed under endoscopy.The physical examination of the patient showed scattered small ulcers in the lower lip of the mouth and small cracks in the perianal area.Combined with his medical history,physical examination,laboratory examinations with high C-reactive protein(CRP),platelet count(PLT),erythrocyte sedimentation rate(ESR)and fecal calprotectin levels,imaging examinations and pathology,a diagnosis of CD was taken into consideration.According to the pediatric CD activity index 47.5,methylprednisolone(40 mg QD)was given intravenously.The abdominal pain disappeared,and CRP,PLT,and ESR levels decreased significantly after the treatment.Unfortunately,he had a large amount of bloody stool again after 1 wk of methylprednisolone treatment,and his hemoglobin level decreased quickly.Although infliximab(IFX)(5 mg/kg)was given as a combination therapy regimen,he still had bloody stool with his hemoglobin level decreasing from 112 g/L to 80 g/L in a short time,so-called SLGIB.With informed consent,accelerated IFX(5 mg/kg)induction was given 7 days after initial presentation.The bleeding then stopped.Eight weeks after the treatment,repeat colonoscopy showed mucosal healing;thus far,no recurrent bleeding has occurred,and the patient is symptom-free.CONCLUSION This case highlights the importance of accelerated IFX induction in SLGIB secondary to CD,especially after steroid hormone treatment.

Lower Extremity Arterial Occlusive Disease As a Rare Complication of Crohn’s Disease

Objective To investigate the clinical characteristics and treatment strategy of lower extremity arterial occlusive disease in patients with Crohn's disease (CD). Methods Clinical information of 9 cases suffering from lower extremity arterial occlusion and CD was investigated retrospectively. Results All the cases were less than 50 years old and the most were females (8/9). Arterial occlusions occurred in either active (5/9) or inactive (4/9) stage of CD. Besides the arteries of lower extremities, other arteries could also be involved such as aorta, iliac artery, renal artery or mesentery artery. Seven cases had atherosclerotic imaging findings (4 had aortic plaques and 6 had iliac artery stenoses). Embolectomy or thromboendarterectomy were mostly performed. Four (44.4%) cases had recurrent lower limb ischemia. Conclusions Arterial occlusive disease is a rare extraintestinal manifestation of CD. A thorough inspection of aorta is necessary. Embolectomy is mostly preferred. Anticoagulation treatment is highly recommended after the operation.

Modeling of the drain-induced barrier lowering effect and optimization for a dual-channel 4H silicon carbide metal semiconductor field effect transistor

A new analytical model to describe the drain-induced barrier lowering （DIBL） effect has been obtained by solving the two-dimensional （2D） Poisson＇s equation for the dual-channel 4H-SiC MESFET （DCFET）. Using this analytical model, we calculate the threshold voltage shift and the sub-threshold slope factor of the DCFET, which characterize the DIBL effect. The results show that they are significantly dependent on the drain bias, gate length as well as the thickness and doping concentration of the two channel layers. Based on this analytical model, the structure parameters of the DCFET have been optimized in order to suppress the DIBL effect and improve the performance.

Cecum Dieulafoy＇s Lesion Presenting with Recurrent Lower Gastrointestinal Bleeding： Case Report

Introduction： Gastrointestinal Dieulafoy＇s lesion is a rare entity, of unknown etiology, and corresponds to an arterial malformation at the submucosal space that can be a source of life-threatening hemorrhage. We report a case of a Cecum Dieulafoy＇s bleeding lesion that was managed endoscopically with a favorable outcome. Case report： Female, 70-year-old, diagnosed with type 2 diabetes, hypothyroidism, and chronic heart failure associated with rheumatic mitral stenosis, submitted to biological valve replacement in 2006 and with permanent atrial fibrillation using vitamin K antagonist anticoagulant for thrombosis prophylaxis. Her background includes a stroke in 2004 without any permanent disability. In 2016, the patient experienced voluptuous and painless lower gastrointestinal bleeding with severe acute anemia, requiring hospital admission, fluid resuscitation and blood transfusion. Urgent colonoscopy revealed a small reddish vascular malformation at the cecum with oozing active bleeding, about 3 mm in size. Initially argon plasma coagulation was performed with satisfactory and immediate hemostasis. One week later, she recurred with hematochezia. The lesion at the cecum was reassessed and it was possible to notice a large caliber vessel surrounded by a normal appearance mucosa, compatible with Dieulafoy＇s lesion and it was treated with an endoscopic clip placement with a good long-term response. Conclusion： Endoscopy is the method of choice for diagnosis of Dieulafuy＇s lesion and may provide efficient treatment with mechanical hemostasis such as endoclip placement with a high success rate.

Ternary analytic porosity-reduction model of sandstone compaction trend and its significance in petroleum geology: A case study of tight sandstones in Permian Lower Shihezi Formation of Shilijiahan area, Ordos Basin, China

The tight sandstones in the Permian Lower Shihezi Formation of Shilijiahan area in the Ordos Basin was taken as study object in this research to quantitatively determine the effects of burial depth, burial time and compaction strength on porosity during densification of reservoir. Firstly, sandstone compaction profiles were analyzed in detail. Secondly, the theoretical study was performed based on visco-elasto-plastic stress–strain model. Thirdly, multiple regression and iterative algorithm were used respectively to ascertain the variation trends of Young's modulus and equivalent viscosity coefficient with burial depth and burial time. Accordingly, the ternary analytic porosity-reduction model of sandstone compaction trend was established. Eventually, the reasonability of improved model was tested by comparing with thin-section statistics under microscope and the models in common use. The study shows that the new model can divide the porosity reduction into three parts, namely, elastic porosity loss, visco-plastic porosity loss and porosity loss from cementation. And the results calculated by the new model of litharenite in He 2 Member are close to the average value from the thin-section statistics on Houseknecht chart, which approximately reveals the relative magnitudes of compaction and cementation in the normal evolution trend of sandstone porosity. Furthermore, the model can more exactly depict the compaction trend of sandstone affected little by dissolution than previous compaction models, and evaluate sandstone compaction degree and its contribution to reservoir densification during different burial and uplift processes.

THE APPLICATION OF WEINSTEIN-CHIEN′S METHOD——THE UPPER AND LOWER LIMITS OF FUNDAMENTAL FREQUENCY OF RECTANGULAR PLATES WITH EDGES ARE THE MIXTURE OF SIMPLY SUPPORTED PORTIONS AND CLAMPED PORTIONS

In this paper, the method of relaxed boundary conditions is applied to rectangular plates with edges which are a sort of the mixture of simply supported portions and clamped portions, so that the lower limit of fundamental frequency of such plates is evaluated. A kind of polynomial satisfying the displacement boundary conditions is designed, os that it is enabled to evaluate the upper limit of fundamental frequency by Ritz' method. The practical calculation examples solved by these methods have given satisfactory results. At the end of this paper, it is pointed out that the socalled exact solution of such plates usually evaluated by the force superposition method is essentially a kind of lower limit of solution, if the truncated error of series which occurs in actual calculation is considered.

lower Oil Prices Test Africa’s growth

The foundations of the ＂Africa rising＂ narrative may have increasingly been tested in recent months. Security concerns, the Ebola crisis in West Africa and conflict in Libya have been some of the stumbling blocks the continent has had to face. These have continuously challenged its ability to respond to events that could derail the past years＇ economic growth. The impact of lower oil prices particularly could be a major shock to the region, especially for oilexporting countries.

多分S-近似空间

基于知识空间理论的多分推广,提出了多分S-近似空间的概念,研究多分S-近似空间模型上、下近似在不同运算和不同决策映射下的性质.进一步,定义上、下近似多分知识状态,利用上、下近似算子的性质研究上、下近似多分知识状态集族形成多分知识结构的条件,特别地,探讨多分知识结构分别满足交封闭和并封闭的条件.多分S-近似空间为多分知识结构的构建及其应用提供了一种新的研究思路和方法,所得成果将丰富和发展S-近似空间理论和知识空间理论.

Modeling of the drain-induced barrier lowering effect and optimization for a dual-channel 4H silicon carbide metal semiconductor field effect transistor

A new analytical model to describe the drain-induced barrier lowering(DIBL) effect has been obtained by solving the two-dimensional(2D) Poisson’s equation for the dual-channel 4H-SiC MESFET(DCFET).Using this analytical model,we calculate the threshold voltage shift and the sub-threshold slope factor of the DCFET,which characterize the DIBL effect.The results show that they are significantly dependent on the drain bias,gate length as well as the thickness and doping concentration of the two channel layers.Based on this analytical model,the structure parameters of the DCFET have been optimized in order to suppress the DIBL effect and improve the performance.

3S技术在新疆塔里木河下游生态环境动态研究中的应用

塔里木河下游多年来水量不断减少 ,造成了该地区地下水位普遍下降 ,导致了植被衰败 ,风沙频繁 ,土地沙漠化普遍发生。在 3S技术支持下 ,通过 1 959年、1 983年、1 992年及1 996年航空及航天遥感信息的对比分析发现 ,下游地区生态环境的变化与自然及人为因素密切相关 。