直接化学气相沉积法制备二维钴铁氧体用于高效析氧反应

二维(2D)过渡金属氧化物(TMO)的地球丰度高,并且具有独特的物理化学性质和较好的催化性能,是新能源工业领域中非常有应用前景的电催化剂.然而,由于合成高质量和可控厚度的2D TMO具有一定的难度,目前有关2D TMO的微观电化学研究的报道较少.本文采用化学气相沉积法直接合成了2D钴铁氧体(CoFeO),所制得的2D CoFeO呈现结晶性良好的超薄尖晶石结构,其最薄厚度可达到6.8 nm.采用超微电极测试平台考察了碱性条件下2DCoFeO催化析氧反应(OER)的性能.结果表明,2D CoFeO(111)面在10 m Acm^(-2)的电流密度下表现出330 m V的低过电位,在570 m V的过电位下表现出142 m Acm^(-2)的高电流密度.密度泛函理论计算发现2DCoFeO表面上的双金属位点降低了反应能垒.此外,2DCoFeO的超薄厚度使体电阻率降低,同时增加了活性位点的利用率,进而提高了对OER的催化活性,这与在超微电极平台上测得的2D CoFeO厚度-OER活性依赖关系的结果一致.本研究还合成了大面积的2D CoFeO薄膜,其标准三电极体系研究表明2D CoFeO样品仍然表现出较高的催化OER活性和较好的寿命,说明所制备的2D CoFeO具有较好的实际应用潜力.综上,本文采用气相化学沉积法直接合成了超薄2DCoFeO纳米片,其最薄厚度可达6.8 nm,2DCoFeO表现出良好的OER性能,为2DTMOs电催化剂的可控合成开辟了新途径.此外,本文还分析了2DCoFeO电催化OER反应的机理,为二维电催化剂设计提供了新思路.

聚苯胺衍生物膜修饰电极的电化学和催化性质

采用聚-2,5-二甲氧基苯胺(PDMAn)、聚邻甲苯胺(POT)膜修饰电极,以异丙醇(i-P)氧化为模型反应,研究功能性膜电极的电催化性能.两种聚合物的伏安行为都表现为两对氧化还原峰;与镀铂的Pt电极比较,Pt金属化的PDMAn和POT修饰电极,大大提高了i-P氧化电流密度,而且随着循环次数增加,氧化电流不断增大,表明功能性膜修饰电极具有较高的催化活性.POT修饰电极在较低的铂含量下就表现出对i-P的强烈催化活性,而且对低浓度i-P的氧化,具有较高的响应灵敏度;此外POT还具有良好的环境稳定性,可望成为一种具有实际应用前景的电化学传感器.

Ru@沸石催化剂用于醇胺化反应实现高选择性制备伯胺

伯醇与氨气直接反应制备伯胺是一条环境友好的路线。在本工作中成功制备了LTA沸石包覆Ru纳米颗粒催化剂(Ru@LTA),并将其应用于低氨醇比条件下(2.1~2.4)正辛醇直接胺化反应。在5Ru@KA沸石催化剂上正辛胺的选择性可以达到76%。Ru@LTA沸石催化剂中的空间位阻效应对提高伯胺选择性有正面作用。

Epidemiology of Sleep Disorders among Chronic Hemodialysis Patients in Senegal: A Multicentric Study

Introduction: Sleep disorders (SD) are common dialysis patients and can impact their quality of life. In previous studies, black ethnicity was associated with higher incidence of SD but a few data are available in African patients. This study aimed to describe prevalence and risk factors of SD among Senegalese dialysis patients. Methods: We performed a cross-sectional study between February 15th and April 30th 2012 including 127 patients (75 males and 52 females) aged 46.8 ± 16.9 (16 - 85 years) and dialysed since >6 months in three dialysis centres. For each patient, we assessed insomnia according to international definition, obstructive sleep apnea syndrome (OSAS) with the Berlin questionnaire, restless leg syndrome (RLS) using abridged version of Cambridge-Hopkins RLS questionnaire, and excessive daytime sleepiness (EDS) with Epworth sleepiness scale. Logistic multivariate regression was used to identify factors associated with different SD. Results: Overall prevalence of SD was 88% comprising: insomnia (64.3%), OSAS (49.1%), RLS (24.1%) and EDS (20.5%). Forty-two patients presented at least two disorders. No difference was noticed in prevalence of SD between genders (p = 0.14). Level of blood pressure were not different across patients with and without SD. Insomnia correlated with anemia, inflammation and EDS. OSAS was associated with age ≥50 years, EDS and neck circumference ≥25 cm. RLS correlated with anemia and EDS. Other parameters such as gender, dialysis vintage, KT/V, obesity, diabetes status and hypoalbuminemia were not associated with the different SD. The majority of patients had not been diagnosed before the survey and none of them was under treatment. Conclusions: Our findings are compatible with high prevalence of sleep disorders reported in other populations. Insomnia and OSAS are the most frequent SD but some patients combined many disorders. Nephrologists should be more aware of these SD in order to detect them early and provide efficient treatment.

Type 2 diabetes in a Senegalese rural area

AIM To estimate the prevalence of diabetes in the rural population of Tessekere(Senegal) and investigate associated risk factors. METHODS Data from a 2015 survey of 500 individuals age 20 and over representative of the population of the municipality of Tessekere were used. Sociodemographic characteristics, health related variables, capillary whole blood glucose, and weight and height measurements of individuals were collected during face-to-face interviews. Statistical analyses used were bivariate tests and binary logistic regressions.RESULTS The percentage of individuals having impaired fasting glucose(IFG) is 6.6%. Those with fasting blood glucose(FBG) levels ≥ 126 mg/dL and/or currently being treated for diabetes is 4.2%. Only mean body mass index(BMI) is significantly higher among diabetic individuals and among those having FBG levels ≥ 110 mg/dL. After adjustment for sex, age, educational level, BMI and hypertension, only BMIis associated with diabetes. CONCLUSION Prevalence of diabetes and IFG in our study correspond to the high range of rural sub-Saharan Africa prevalence. Diabetes is thus becoming a pressing public health concern, even in rural areas. But the risk factors identified in Tessekere suggest that the diabetes epidemic is still in the early stages, such that concerted action would make it possible to contain the devastating impact of this chronic condition.

熔融沉积法制备纤维素纳米纤维增强聚乳酸基复合材料的拉伸性能

生物可降解聚合物可以在保持结构力学性能的同时可以实现碳中性,是石油基聚合物的潜在替代品。在这些聚合物中,聚乳酸(Polylactic acid,PLA)因其良好的力学性能、生物相容性和热塑性而特别有发展前景。本文利用机械脱脂纤维素纳米纤维(Cellulose nanofiber,CNF)来提高聚乳酸的力学性能,该纤维具有显著的力学性能和生物降解性。熔融沉积建模(Fused deposition modeling,FDM)是热塑性聚合物的三维打印方法之一,可以降低制造成本。本研究采用FDM法制备了机械脱脂CNF增强PLA基复合材料,并在两个打印方向(0°/90°和+45°/-45°)上研究了它们的拉伸性能,梳理了机械制备CNF增强PLA基复合材料的印刷方向与拉伸行为之间的关系。此外,利用扫描电镜研究了机械脱脂CNF增强PLA基复合材料的显微组织和断口。

Traditional Pathway of Oil Extraction from <i>Quassia undulate</i>Seeds and Its Chemical Characteristic

In Africa, traditional vegetable oil extraction often involves the use of plants in the manufacturing process. Quassia undulate oil is thus traditionally prepared. An expedition went to Kédougo (a region in southeastern Senegal involving women of the Bassaris community) in June 2018 to study the Q. undulate oil traditional extraction mode. Thus, the objective of this study is to follow the traditional extraction of Q. undulate oil and to perform the physico-chemical analysis of the obtained oil. Oil samples taken after the survey allowed the oil physico-chemical characterization. The traditional oil extraction made by four women from Eganga, Ethiolo, and Ebarack’s villages reveals oil clear that is solid at room temperature. The study of the established chart revealed the use of Pilliostigma thonnintigi leaves during the oil preparation. The oil shows characteristics comparable to shea butter, and the oil stability can be compared to the corn and peanut oil one. The physicochemical analysis showed oil solid at room temperature with an acid value between 1.223 ± 0.013 and 7.333 ± 0.465. The saponification value was between 190.489 ± 3.083 and 199.732 ± 3.107, and the peroxide value between 4.453 ± 0.042 and 8.644 ± 0.285. The iodine values were between 21.455 ± 2.440 and 38.068 ± 0.082, and the refractive index 1.462 - 1.463. Q. undulate oil offers several technological perspectives. However, it would be interesting to study the impact of P. thonnintigi leaves during extraction. The fatty acid profile should also be determined.

Characterization of meso-scale mechanical properties of Longmaxi shale using grid microindentation experiments

Mechanical properties,such as the hardness H,Young’s modulus E,creep modulus C,and fracture toughness Kc,are essential parameters in the design of hydraulic fracturing systems for prospective shale gas formations.In this study,a practical methodology is presented for obtaining these properties through microindentation experiments combined with quantitative observations of the mineralogical phases using X-ray diffraction(XRD),scanning electron microscopy(SEM)with backscattered electron(BSE)imaging,and energy-dispersive X-ray spectroscopy(EDS)analyses.We apply this method in the case of three types of Longmaxi shales with different mineralogies(i.e.carbonate-,clay-,and quartz-rich,respectively),which allows us to determine the characteristic indentation depth,hc?8e10 mm,beyond which the mechanical response of the carbonate-rich shale is homogeneous and independent of its complex heterogeneous microstructure.Moreover,exploiting the results of a large number of indentation tests,we demonstrate that the indentation modulus M of the shale increases as a power-law of hardness H,and its creep modulus C increases linearly with H.We also compute the fracture toughness Kc from the indentation data by assuming a perfectly plastic behavior of the sample.Our results are in good agreement with independent measurements of Kc determined by microscratch tests.Finally,further tests on quartz-and clay-rich samples of the Longmaxi shale suggest further variations in the samples’mechanical properties depending on their burial conditions and the mechanical properties of their dominant mineral phases.

Rambutan-like hollow carbon spheres decorated with vacancy-rich nickel oxide for energy conversion and storage

Transition metal oxides hold great promise for lithium-ion batteries(LIBs)and electrocatalytic water splitting because of their high abundance and high energy density.However,designing and fabrication of efficient,stable,high power density electrode materials are challenging.Herein,we report rambutan-like hollow carbon spheres formed by carbon nanosheet decorated with nickel oxide(NiO)rich inmetal vacancies(denoted as h-NiO/C)as a bifunctional electrode material for LIBs and electrocatalytic oxygen evolution reaction(OER).When being used as the anode of LIBs,the h-NiO/C electrode shows a large initial capacity of 885mAh g−1,a robust stability with a high capacity of 817mAh g−1 after 400 cycles,and great rate capability with a high reversible capacity of 523mAh g−1 at 10Ag−1 after 600 cycles.Moreover,working as an OER electrocatalyst,the h-NiO/C electrode shows a small overpotential of 260mV at 10mAcm−2,a Tafel slope of 37.6mVdec−1 along with good stability.Our work offers a cost-effective method for the fabrication of efficient electrode for LIBs and OER.

出版业的新发展方向：为图书馆提供复合型的信息媒体

出版业的新发展方向：为图书馆提供复合型的信息媒体保罗·杜居白华浩著张屹编译现代图书馆是信息世界的入口，是民族文化与传统的宝库。图书馆里有各种信息媒体，专业人员解答读者的问题，还有各种资源指引读者到相应的地方去寻找他们所需要的信息。今天的图书馆员在信息...

A phononic rectifier based on carbon schwarzite host–guest system

Thermal rectification is a promising way to manipulate the heat flow,in which thermal phonons are spectrally and collectively controlled.As phononic devices are mostly relying on monochromatic phonons,in this work we propose a phononic rectifier based on the carbon schwarzite host–guest system.By using molecular dynamic simulations,we demonstrate that the phononic rectification only happens at a specific frequency of the hybridized mode for the host–guest system,due to its strong confinement effect.Moreover,a significant rectification efficiency,~134%,is observed,which is larger than most of the previously observed efficiencies.The study of length and temperature effects on the phononic rectification shows that the monochromaticity and frequency of the rectified thermal phonons depend on the intrinsic anharmonicity of the host–guest system and that the on-center rattling configuration with weak anharmonicity is preferable.Our study provides a new perspective on the rectification of thermal phonons,which would be important for controlling monochromatic thermal phonons in phononic devices.

Dendrochronological Potential and Impact of Climate Factors on Radial Growth of Two Species in the Sahelian Zone: <i>Boscia senegalensis</i>(Pers.) Lam. ex Poir and <i>Sclerocarya birrea</i>(A. Rich) Hoscht (Ferlo Nord/Senegal)

The objective of this study is to analyze the dendrochronological potential of two Sahelian species (B. senegalensis and S. birrea) and to evaluate the relationships between their growth rings and the climate. The study was conducted in 2016 in the Ferlo area of Senegal. The biological material consists of wood slices, taken from the trunks of these adult woody species at 0.30 m and 1.30 m from the ground after they have been felled. The technique used to examine the slices consists in identifying their rings, establishing their structures, inter-dating them and studying the relationship between the identified rings and climatic factors. The results showed that the species had thin, clear, highly visible and sharp rings. The limit of growth is marked by a line of parenchyma. Intradatation series carried out on the chronologies made it possible to estimate the ages of the individuals, which vary from 10 to 38 years for B. senegalensis and from 29 to 50 years for S. birrea. Their average growth rates are estimated at 0.906 mm/year and 0.89 mm/year respectively. The chronological sequences are 29 years (1987-2016) for B. senegalensis and 38 years (1964-2012) for S. birrea. The results revealed that there is no significant correlation between the growth chronologies of B. senegalensis and the climatic regressors (temperature and precipitation). In contrast, the ring-climate relationship shows that in S. birrea winter precipitation positively influences ring growth while temperature has no effect on ring growth in this species. This study provides a better understanding of the response of forest ecosystems to possible climate change, particularly in the current context of sustainable forest management.

Development of Allometric Models for Estimating the Biomass of <i>Sclerocarya birrea</i>(A.Rich) Hoscht and <i>Boscia senegalensis</i>(Pers.) Lam. ex Poir.

The objective of this study was to develop allometric models for estimating the biomass of Sclerocarya birrea (A.Rich) Hoscht and Boscia senegalensis (Pers.) Lam. ex Poir. The inventory of these ligneous was carried out at Widou Thiengoly (North of Senegal). The sample consists of 43 individuals of Boscia senegalensis and 15 individuals of Sclerocarya birrea. The selected individuals were dendrometrically characterized before being cut, compartmentalized (trunk, branches, and twigs) and weighed entirely. Simple regression tests were performed to examine the most explanatory dendrometric parameter (x) for biomass (y) according to two types of models: the linear model (y = ax + b) and the polynomial model of degrees 2 (y = ax2 + bx + c). The criteria for selection and validity of the models are based firstly on the tests of normality, nullity, heterogeneity and autocorrelation of the residues. The results showed that the most explanatory dendrometric parameter of the biomass was the crown surface for Boscia senegalensis and the 1.30 m diameter for Sclerocarya birrea of all the tests performed, the second-order Polynomial model is the best predictor of above ground biomass for these two species. Thus, the allometric models established to predict the biomass of these two species are: y = 0.0023x2 + 0.4851x - 0.0519 for Boscia senegalensis and y = 0.35x2 + 10.35x - 12.90 for S. birrea;with very significant correlation coefficients (R2) of 0.85 and 0.94 respectively. These results can be used for a sequestered carbon assessment study and will play a role in monitoring the carbon market in Africa.

Quassia undulata Oil Exploitation: Extraction’s Yield, Phytochemical Profile of Seeds and Oilcake Nutritional Value

Quassia undulata is a plant that belongs to the Simaroubaceae family. In Africa, it occurs in the wooded savannah from Senegal in the west to the Central African Republic in the east. The seeds from the plant are very rich in oil. The traditional extraction of this oil involves a phase of boiling the powder from the seeds in a decoction of Piliostigma thonningii leaves. Thus, the aim of this study is to determine the impact of Piliostigma thonningii leaves on the extraction yield, to assess the phytochemical profile of seeds and oilcake and, to determine the nutritional value of the cakes obtained after extraction. Thus, the traditional extraction of oil was carried out in the laboratory and physico-chemical and phytochemical analyses were carried out on the water decoction, the oil and, the oilcake. The results showed that the traditional extraction gives a low extraction yield (5.18% with PD and 6.12% without PD) compared to the Soxhlet extraction (56.9%). On the other hand, it was found that oil obtained by traditional extraction in the presence of Piliostigma thonningii leaves was of better physicochemical quality. Finally, oilcake very rich in proteins (36.71% - 42.69%) and mineral elements (110.9 - 152.33 mg/100g of calcium, 544.75 - 620.77 mg/100g of Potassium and 331.11 - 459.68 mg/100g of Magnesium) justify their use in human food. However, investigations should point to the impact of this traditional technique on the elimination of quassinoids, toxins and antihelminth compounds present in the seeds.

Modeling Microbial Decomposition in Real 3D Soil Structures Using Partial Differential Equations

Partial Differential Equations (PDEs) have been already widely used to simulate various complex phenomena in porous media. This paper is one of the first attempts to apply PDEs for simulating in real 3D structures. We apply this scheme to the specific case study of the microbial decomposition of organic matter in soil pore space. We got a 3D geometrical representation of the pore space relating to a network of volume primitives. A mesh of the pore space is then created by using the network. PDEs system is solved by free finite elements solver Freefem3d in the particular mesh. We validate our PDEs model to experimental data with 3D Computed Tomography (CT) images of soil samples. Regarding the current state of art on soil organic matter decay models, our approach allows taking into account precise 3D spatialization of the decomposition process by a pore space geometry description.

HPTLC Phytochemical Screening and Hydrophilic Antioxidant Activities of <i>Apium graveolens</i>L., <i>Cleome gynandra</i>L., and <i>Hibiscus sabdariffa</i>L. Used for Diabetes Management

Diabetes mellitus is a socially significant disease characterized by chronic hyperglycemia and metabolic disorders of proteins, carbohydrates, and lipids due to reduced function of insulin. Medicinal plants, rich in bioactive components that promote prevention and treatment, are inexpensive and no side effects. Apium graveolens, Cleome gynandra, and Hibiscus sabdariffa from Burkina Faso were investigated for their phytochemical profile and antioxidant activities. The high-performance thin-layer chromatography profile revealed flavonoids, tannins, and sterols in these herbaceous. The Hibiscus sabdariffa methanolic extract exhibited the highest total phenolic (138.4 ± 0.5 mg GAE/g DW) and flavonoid (52.8 ± 0.6 mg RuE/g DW) contents comparatively to Cleome gynandra and Apium graveolens. Hibiscus sabdariffa methanolic extract also presented the highest antioxidant activity (IC50 = 0.31 ± 0.002 mg/mL) using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity assay. A high correlation between flavonoid contents and hydrophilic antioxidant activities (r = 0.99) was observed, indicating that flavonoids contribute significatively to these herbaceous antioxidant properties. Apium graveolens, Cleome gynandra, and Hibiscus sabdariffa constitute a natural source of phenolic compounds that could be exploited in diabetes mellitus management.

Wild Fruits Traditionally Gathered by the Malinke Ethnic Group in the Edge of Niokolo Koba Park (Senegal)

In rural areas, the local population draws from several forest resources needed for survival including food. Then it is a granary for these native people. Unfortunately, useful wild plants are highly threatened, especially by various human activities. Because of this situation we started with open semi-structured interviews to identify wild fruit plants, their consumed organs and their seasonality in the rural community of Tomboronkoto. Tomboronkoto is located at the edge of the Niokolo-Koba National park (Senegal) and is mainly inhabited by Malinke. We identified 45 wild fruit species belonging to 38 genera that can be divided in 28 botanical families. The more diversified are successively the Anacardiaceae, Tiliaceae, Apocynaceae and Caesalpiniaceae. More than half of the plants inventoried are trees (53%). We can distinguish three categories of fruits depending on their Fidelity Level (FL) that informs us about their popularity: the well-known or common fruits, moderately known fruits and little known fruits. A dozen wild fruits happen to be greatly appreciated with very high fidelity level (100% to 84%). The fruits of Saba senegalensis, Adansonia digitata, Parkia biglobosa, Tamarindus indica and Vitellaria paradoxa are the most variously used because they are appreciated being fresh or cooked. Only fruits of Ficussur are available all year long. The large majority of the most consumed fruits are available between the end of the hot dry season until the middle of the rainy season. This period coincides with the period where crops from the previous rainy season are depleted and the new crops are not yet ripe. Thus, these wild fruits would greatly contribute to food security in this area during the lean period.

Research on Arterial Stiffness Status in Type 2 Diabetic Patients Based on Pulse Waveform Characteristics

For patients with type 2 diabetes,the evaluation of pulse waveform characteristics is helpful to understand changes in arterial stiffness.However,there is a lack of comprehensive analysis of pulse waveform parameters.Here,we aimed to investigate the changes in pulse waveform characteristics in patients with type 2 diabetes due to increased arterial stiffness.In this study,25 patients with type 2 diabetes and 50 healthy subjects were selected based on their clinical history.Age,height,weight,blood pressure,and pulse pressure were collected as the subjects’basic characteristics.The brachial-ankle pulse wave velocity(baPWV)was collected as an index of arterial stiffness.Parameters of time[the pulse wave period(T),the relative positions of peak point(T1)and notch point(T2),and pulse wave time difference between upper and lower limbs(T3)]and area[the total waveform area(A),and the areas of the waveform before(A1)and after(A2)the notch point]were extracted from the pulse wave signals as pulse waveform characteristics.An independent sample t-test was performed to determine whether there were significant differences between groups.Pearson’s correlation analysis was performed to determine the correlations between pulse waveform parameters and baPWV.There were significant differences in T3,A,A1,and A2 between the groups(p<0.05).For patients with type 2 diabetes,there were statistically significant correlations between baPWV and T3,A,A1,and A2(p<0.05).This study quantitatively assessed changes in arterial pulse waveform parameters in patients with type 2 diabetes.It was demonstrated that pulse waveform characteristics(T3,A,A1,and A2)could be used as indices of arterial stiffness in patients with type 2 diabetes.

Severity and Magnitude of Caries among Rural Populations in Ferlo in Senegal

Oral diseases belong to non-communicable diseases. They are characterized by their importance especially in disadvantaged areas. The objective of this study was to measure the extent and severity of caries among rural populations of Widou, an area located in central Ferlo. It was a descriptive and cross-sectional study which involved 300 individuals selected using simple random sampling. The socio-demographic characteristics collected were sex, age, educational level and occupation. The dental status was rated by the prevalence of dental caries and DMF and its components. The data were analyzed with the software Epi info 3.4.5 with 5% of threshold statistical significance. The prevalence of dental caries was 89%. The mean DMF was 5.4 ± 5.6 with a maximum of 26. The mean of component “D” was 3.8 with a maximum of 24. Variables significantly associated with dental caries were sex (p = 0.012) and occupation (p = 0.03). The extent and severity of caries in rural areas of the Ferlo evoke a relatively low support or management and require efforts in prevention, directed on oral hygiene and dietary habits.

Oral care offerings in populations of Ferlo (Senegal): The contribution of traditional dentistry

The aim of this study was to examine whether the offering of traditional treatments can constitute a positive contribution to integrate in an oral public health care settings. Method: This was a cross-sectional study involving 300 people living in the area of Ferlo in East Central Senegal. Selected individuals must be residents of the area over the age of 15 years. Cluster sampling was used as a recruitment method. Data collected concerned the type of oral health care used whether modern or traditional, the periodontal condition (plaque, gingival and bleeding index, attachment loss, pocket depth and CPITN). Dental status was evaluated by DMFT. The data were analyzed with R software and the Student’s t test was used to compare the averages of indices in both groups at the threshold of 5%. A co-variance analysis was allowed in order to determine associations between some indices and therapy type in multivariate approach. Results: Averages of dental and periodontal indices were globally higher in people using modern therapies. DMFT, CPITN and gingival index increased significantly when the type of therapy was modern after adjustment on the plaque index and age. Conclusion: The traditional dentistry could constitute a positive contribution to a public health care, especially in a context of developing country. However, this practice should be guided and validated by a research-based evidence to allow better use of the therapeutic processes, and promote the health of populations.