Search

Inorganic salts usually demonstrate simple phasal behaviors in dilute aqueous solution mainly involving soluble (homogeneous) and insoluble (macrophase separation) scenarios. Herein, we report the discovery of complex phase behavior involving multiple phase transitions of clear solution – macrophase separation – gelation – solution – macrophase separation in the dilute aqueous solutions of a structurally well-defined molecular cluster [Mo7O24]6− macroanions with the continuous addition of Fe3+. No chemical reaction was involved. The transitions are closely related to the strong electrostatic interaction between [Mo7O24]6− and their Fe3+ counterions, the counterion-mediated attraction and the consequent charge inversion, leading to the formation of linear/branched supramolecular structures, as confirmed by experimental results and molecular dynamics simulations. The rich phase behavior demonstrated by the inorganic cluster [Mo7O24]6− expands our understanding of nanoscale ions in solution.

Background While 5% of 247 million global malaria cases are reported in Uganda, it is also a top refugee hosting country in Africa, with over 1.36 million refugees. Despite malaria being an emerging challenge for humanitarian response in refugee settlements, little is known about its risk factors. This study aimed to investigate the risk factors for malaria infections among children under 5 years of age in refugee settlements in Uganda. Methods We utilized data from Uganda’s Malaria Indicator Survey which was conducted between December 2018 and February 2019 at the peak of malaria season. In this national survey, household level information was obtained using standardized questionnaires and a total of 7787 children under 5 years of age were tested for malaria using mainly the rapid diagnostic test. We focused on 675 malaria tested children under five in refugee settlements located in Yumbe, Arua, Adjumani, Moyo, Lamwo, Kiryadongo, Kyegegwa, Kamwenge and Isingiro districts. The extracted variables included prevalence of malaria, demographic, social-economic and environmental information. Multivariable logistic regression was used to identify and define the malaria associated risk factors. Results Overall, malaria prevalence in all refugee settlements across the nine hosting districts was 36.6%. Malaria infections were higher in refugee settlements located in Isingiro (98.7%), Kyegegwa (58.6%) and Arua (57.4%) districts. Several risk factors were significantly associated with acquisition of malaria including fetching water from open water sources [adjusted odds ratio (aOR) = 1.22, 95% CI: 0.08–0.59, P = 0.002], boreholes (aOR = 2.11, 95% CI: 0.91–4.89, P = 0.018) and water tanks (aOR = 4.47, 95% CI: 1.67–11.9, P = 0.002). Other factors included pit-latrines (aOR = 1.48, 95% CI: 1.03–2.13, P = 0.033), open defecation (aOR = 3.29, 95% CI: 1.54–7.05, P = 0.002), lack of insecticide treated bed nets (aOR = 1.15, 95% CI: 0.43–3.13, P = 0.003) and knowledge on the causes of malaria (aOR = 1.09, 95% CI: 0.79–1.51, P = 0.005). Conclusions The persistence of the malaria infections were mainly due to open water sources, poor hygiene, and lack of preventive measures that enhanced mosquito survival and infection. Malaria elimination in refugee settlements requires an integrated control approach that combines environmental management with other complementary measures like insecticide treated bed nets, indoor residual spraying and awareness. Graphical Abstract

The authors present sharp transformation inequalities for the zero-balanced hypergeometric function $${}_2F_1(a,b;a+b;r)$$ created by the transformations $$r\mapsto x=[(1-r)/(1+2r)]^3$$ and $$r\mapsto 1-x$$ , $$r\mapsto u=(1/2)r(3+r)^2(1+r)^{-3}$$ and $$r\mapsto 1-u$$ , $$r\mapsto p=(27/2)r(1+r)^4(1+4r+r^2)^{-3}$$ and $$r\mapsto 1-p$$ , by showing the monotonicity properties of certain combinations in terms of hypergeometric functions and elementary functions, thus extending the transformation identities satisfied by $${}_2F_1(1/3,2/3;1;r)$$ with these three pairs of transformations and substantively improving the related known results. With these results, some properties are obtained for the generalized Grotzsch ring functions and the modular functions appearing in Ramanujan’s modular equations. Some other properties of $${}_2F_1(a,b;c;r)$$ are obtained, too.

Rolling resistance and angle constraint are important factors affecting the control performance and dynamics of Two-Wheeled Inverted Pendulums (TWIPs, for short), but they are usually neglected in previous studies. Taking both factors into account, this paper presents new control designs for the angle control of the pendulum, for the velocity control and the position control of the TWIP system. Firstly, based on dimensionality reduction and the nonlinear dynamics of the inverted pendulum, a controller with simple structure is designed for controlling the pendulum angle when the rolling resistance is precisely known. Then an improved robust controller against the unknown rolling resistance is designed for the pendulum angle. Secondly, by using the dynamics theory of slow-fast systems, velocity and position controllers for the wheels of the TWIP system are proposed with known and unknown rolling resistance. In the position control, the overshoots can be adjusted close enough to zero. Numerical examples are given to verify and demonstrate the theoretical results.

At present, the treatment of esophageal cancer (EC) is mainly surgical and drug treatment. However, due to drug resistance, these therapies can not effectively improve the prognosis of patients with the EC. Therefore, a multigene prognostic risk scoring system was constructed by bioinformatics analysis method to provide a theoretical basis for the prognosis and treatment decision of EC. The gene expression profiles and clinical data of esophageal cancer patients were gathered from the Cancer Genome Atlas TCGA database, and the differentially expressed genes (DEGs) were screened by R software. Genes with prognostic value were screened by Kaplan Meier analysis, followed by functional enrichment analysis. A cox regression model was used to construct the prognostic risk score model of DEGs. ROC curve and survival curve were utilized to evaluate the performance of the model. Univariate and multivariate Cox regression analysis was used to evaluate whether the model has an independent prognostic value. Network tool mirdip was used to find miRNAs that may regulate risk genes, and Cytoscape software was used to construct gene miRNA regulatory network. GSCA platform is used to analyze the relationship between gene expression and drug sensitivity. 41 DEGs related to prognosis were pre-liminarily screened by survival analysis. A prognostic risk scoring model composed of 8 DEGs (APOA2, COX6A2, CLCNKB, BHLHA15, HIST1H1E, FABP3, UBE2C and ERO1B) was built by Cox regression analysis. In this model, the prognosis of the high-risk score group was poor (P

Stability analysis has been always a key issue in nonlinear dynamics and engineering applications, and it is still a challenging task for time-delay control systems when tuning some parameters like feedback gains and delays. In this paper, firstly we propose a parametric continuation algorithm for calculating the rightmost characteristic root(s), by solving initial value problems of a nonlinear differential equation associated with the characteristic function of the time-delay system. Then we study the static bifurcation caused by multiple characteristic roots that occurs in solving the associated nonlinear initial value problems and present an algorithm for fast calculation of the bifurcation points. We demonstrate the theoretical results with examples arising in vibration control.

Background In Ethiopia, schistosomiasis is caused by Schistosoma mansoni and S. haematobium with the former being widespread and more than 4 million people are estimated to be infected by S. mansoni annually with 35 million at risk of infection. Although many school- and community-based epidemiological surveys were conducted over the past decades, the national distribution of schistosomiasis endemic areas and associated socio-environmental determinants remain less well understood. In this paper, we review S. mansoni prevalence of infections and describe key biogeographical characteristics in the endemic areas in Ethiopia. Methods We developed a database of S. mansoni infection surveys in Ethiopia through a systematic review by searching articles published between 1975 and 2019 on electronic online databases including PubMed, ScienceDirect, and Web of Science. A total of 62 studies involving 95 survey locations were included in the analysis. We estimated adjusted prevalence of infection from each survey by considering sensitivity and specificity of diagnostic tests using Bayesian approach. All survey locations were georeferenced and associated environmental and geographical characteristics (e.g. elevation, normalized difference vegetation index, soil properties, wealth index, and climatic data) were described using descriptive statistics and meta-analysis. Results The results showed that the surveys exhibited a wide range of adjusted prevalence of infections from 0.5% to 99.5%, and 36.8% of the survey sites had adjusted prevalence of infection higher than 50%. S. mansoni endemic areas were distributed in six regional states with the majority of surveys being in Amhara and Oromia. Endemic sites were found at altitudes from 847.6 to 3141.8 m above sea level, annual mean temperatures between 17.9 and 29.8 ℃, annual cumulative precipitation between 1400 and 1898 mm, normalized difference vegetation index between 0.03 and 0.8, wealth index score between –68 857 and 179 756; and sand, silt, and clay fraction in soil between 19.1–47.2, 23.0–36.7, and 20.0–52.8 g/100 g, respectively. Conclusions The distribution of S. mansoni endemic areas and prevalence of infections exhibit remarked environmental and ecological heterogeneities. Future research is needed to understand how much these heterogeneities drive the parasite distribution and transmission in the region. Graphic Abstract

Background Schistosomiasis and fascioliasis are digenean parasitic infections and are among the neglected tropical diseases that have both medical and veterinary importance. They are found mainly in areas having limited access to safe water supply and improved sanitation. Methods A cross-sectional study was conducted to determine the prevalence of Schistosoma mansoni and Fasciola species infections and to identify associated risk factors among school children in Amhara Regional State, Ethiopia. Stool specimens were collected from 798 children (419 males, 379 females) and processed using Kato-Katz and formol-ether concentration techniques. A semi-structured questionnaire was used to collect socio-demographic and other exposure information to explore potential risk factors for the infections. Results The overall prevalence of S. mansoni and Fasciola species infections was 25.6% (95% confidence interval (CI): 22.5-28.6) and 5.5% (95% CI: 3.9-7.1), respectively. S. mansoni was present in all surveyed schools with the prevalence ranging from 12.8% (16/125; 95% CI = 5.6-20.0) to 39.7% (64/161; 95% CI = 32.2-47.2) while Fasciola species was identified in five schools with the prevalence ranging from 2.5% (4/160; 95% CI = 0.001–4.9) to 9.8% (13/133; 95% CI = 4.7–14.8). The prevalence of S. mansoni infection was significantly associated with swimming in rivers (Adjusted odds ratio (AOR): 1.79, 95% CI, 1.22–2.62; P=0.003), bathing in open freshwater bodies (AOR, 2.02; 95% CI, 1.39–2.94; PP=0.004), and was higher in children attending Addis Mender (AOR, 2.56; 95% CI, 1.20–5.46; P=0.015 ) and Harbu schools (AOR, 3.53; 95% CI, 1.64–7.59; P=0.001). Fasciola species infection was significantly associated with consumption of raw vegetables (AOR, 2.47; 95% CI, 1.23-4.97; P=0.011) and drinking water from unimproved sources (AOR, 2.28; 95% CI, 1.11–4.70; P=0.026). Conclusion Both intestinal schistosomiasis and human fascioliasis are prevalent in the study area, affecting school children. Behaviors and access to unimproved water and sanitation are among significant risk factors. The findings are instrumental for targeted interventions.

The cold-rolled 5% medium Mn steel was butt-welded using a fiber laser. The microstructure, distribution of microhardness, and tensile properties of the base metal (BM) and welded joint were investigated. The results showed that the fusion zone of the welded joint had the highest microhardness due to the formation of 100% martensite. A finely mixed microstructure of martensite, ferrite, and austenite was formed in the heat-affected zone, and there was no softened zone in this area. The tensile test results indicated that the ultimate tensile strength and yield strength were higher for the joint than for BM. The joint efficiency was approximately 100%. All samples of the welded joint failed at the location of BM during tensile deformation. The fracture surfaces of the BM and welded joint were mainly ductile fractures. The BM and welded joint exhibited strain rate independence of the tensile strength and yield strength at strain rates of 0.01–1 s−1, while the yield strength of the BM and welded joint increased rapidly when the strain rate reached 5 s−1 due to changes in the dislocation movement mechanisms. The uniform elongation of the BM and welded joint decreased with increasing strain rate.

In this paper, the authors present sharp approximations in terms of sine function and polynomials for the so-called Ramanujan constant (or the Ramanujan $R$-function) $R(a)$, by showing some monotonicity, concavity and convexity properties of certain combinations defined in terms of $R(a)$, $\sin(\pi a)$ and polynomials. Some properties of the Riemann zeta function and its related special sums are presented, too., Comment: 19 pages

For a graph G = (V, E) without isolated vertex, a function f: E(G) → {−1, 1} is said to be a signed star dominating function of G\(\sum\limits_{e \in E(v)} {f(e) \ge 1} \) for every v ∈ V(G), where E(v) = {uv} ∈ E(G)∣ u ∈ V(G)}. The minimum value of \(\sum\limits_{e \in E(G)} {f(e)} \), taken over all signed star dominating functions f of G, is called the signed star domination number of G and is denoted by γss(G). This paper studies the bounds and algorithms of signed star domination numbers in some classes of graphs. In particular, sharp bounds for the signed star domination number of a general graph and a linear-time algorithm for the signed star domination problem in a tree is presented.

Despite the intensive studies on neurons, the control mechanism in real interactions of neurons is still unclear. This paper presents an understanding of this kind of control mechanism, controlling a neuron by stimulating another coupled neuron, with the uncertainties taken into consideration for both neurons. Two observers and a differentiator, which comprise the first-order low-pass filters, are first designed for estimating the uncertainties. Then, with the estimated values combined, a robust nonlinear controller with a saturation function is presented to track the desired membrane potential. Finally, two typical bursters of neurons with the desired membrane potentials are proposed in the simulation, and the numerical results show that they are tracked very well by the proposed controller.

Treated groundwater is a major source of drinking water but subject to potential contamination of fecal–oral pathogens. To understand ecology of the pathogens in the treated water, this study evaluated survival and growth of Vibrio cholerae and Escherichia coli in the treated groundwater in northern Cameroon. E. coli and V. cholerae O1 were isolated from human feces. Water samples were collected from the following sources: a well, tap water from the Cameroon Water Utilities Company, and mineral and borehole waters sold in Maroua, respectively. These waters were treated by one or more processes, including autoclaving, filtration, chlorination and ozonation and were used for the constitution of microcosms. E. coli and V. cholerae were inoculated into each microcosm at respective concentrations of 50 CFU/10 mL (separately) and 40 CFU/10 mL each (together). All bacterial strains survived in all microcosms were used. The ability to survive and grow varied with the bacterial strain and microcosm (P V. cholerae grew faster than E. coli with the latter even showing decrease in concentration in mineral water. When inoculated together, V. cholerae grew faster than E. coli, except in autoclaved well water and filtered and autoclaved well water. Autochthonous ultramicroflora inhibited the growth of E. coli in filtered well water (P

A new two-dimensional (2D) 3d–4f heterometallic coordination polymer, which is {[Tb2Zn4(µ3-TFMIDC)4(µ4-HTFMIDC)(H2O)8]·2H2O}n, has been successfully synthesized by the solvothermal reaction of 2-(trifluoromethyl)-1H-4,5-imidazole dicarboxylic acid (H3TFMIDC) with Zn(II) and Tb(III) ions. The title compound was structurally characterized by diverse characterization techniques including single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Single-crystal structure analysis reveals that the as-preprared compound is a 2D heterometallic 3d–4f coordination network based on interesting planar tetranuclear squares [Zn4(TFMIDC)4] as building blocks, representing the first example of novel heterometallic coordination polymer based on the H3TFMIDC ligand. In addition, the title compound exhibits very intense green luminescence and characteristic transitions of the Tb(III) ion when excited at 291 nm. Lattice parameters for the title compound: a = 11.1449(12) A, b = 12.8498(13) A, c = 37.553(4) A, α = β = γ = 90°, V = 5378.0(10) A3, Z = 4. A unique 2D 3d–4f heterometallic coordination polymer containing interesting planar tetranuclear square building blocks has been constructed by the solvothermal reaction of 2-(trifluoromethyl)-1H-4,5-imidazole dicarboxylic acid (H3TFMIDC) with Zn(II) and Tb(III) ions.

A new 3D Zn(II) MOF based on 2-(hydroxymethyl)-1H-imidazole-4,5-dicarboxylic acid (H4hmIDC), formulated as {[Zn3(HhmIDC)2(H2O)2]·2H2O}n, has been successfully prepared under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction, elemental analysis and infrared spectroscopy, as well as power X-ray diffraction. It is worth noting that the unique HhmIDC3− ligand in the title compound adopts an unusual coordination mode, namely µ4-kN,O: kN′,O′: kO″,O‴: kO′′′′ to link the Zn(II) ions into an interesting 3D coordination framework. Such a 3D network can be further simplified as a binodal 4-connected mog (moganite) topology with the Schlafli symbol of (4·64·8)2(42·62·82). Moreover, the title Zn(II) MOF shows a relatively high thermal stability up to 340 °C, and exhibits an intense blue emission centered at 450 nm upon excitation at 370 nm. A new 3D microporous Zn(II) MOF with an uncommon binodal 4-connected mog topology has been constructed from 2-(hydroxymethyl)-1H-imidazole-4,5-dicarboxylic acid (H4hmIDC). Such a Zn(II) MOF displays a relatively high thermal stability and exhibits very strong blue photoluminescence with a maximum emission band at 450 nm when excited at 370 nm.