Search

Understanding the nature of dopant dynamics in the solid state is critical for improving the longevity and stability of organic electronic devices and for optimizing the doping-induced solubility control (DISC) patterning method. In this work, we use quasi-elastic neutron scattering (QENS) and fluorescence quenching techniques to develop a comprehensive picture of both the microscopic and macroscopic dynamics of the soluble p-type molecular dopant tetrafluoromethyloxycarbonyltricyanoquinodimethane (F4MCTCNQ) in the conductive polymer poly(3-hexylthiophene-2,5-diyl) (P3HT). Specifically, fast dynamics (ps-ns) of the dopant, such as the methyl and the methoxycarbonyl group rotations, are observed in QENS experiments. From confocal fluorescence microscope experiments, longer-range/slower dopant diffusion (ms-days) is captured. However, in order to fit these data, it is necessary to incorporate a Langmuir isotherm equilibrium between the neutral and ionized dopant molecules. Ionized F4MCTCNQ is strongly favored by the equilibrium, but it diffuses 3 orders of magnitude slower than neutral species. Moreover, the macroscopic diffusion is found to depend mostly on the minority concentration of neutral dopant molecules in the film. Finally, the global diffusion coefficient of the monoester-substituted dopant F4MCTCNQ is shown to be more than an order of magnitude smaller than that of the widely used dopant F4TCNQ.

In liquids, the ability of neighboring molecules to rearrange and jostle past each other is directly related to viscosity, the property which describes the propensity to flow. The presence of hydrogen bonds (H-bonds) complicates the molecular scale picture of viscosity. H-Bonds are attractive, directional interactions between molecules which, in some cases, result in transient network structures. In this work, we use experimental and computational methods to demonstrate that the timescale of H-bond network reorganization is the dominant dynamical timescale associated with viscosity for the case of the model H-bonding liquid n-methylacetamide (NMA). This molecule is a peptide analog which forms a transient linear H-bond network. Individual H-bond lifetimes and dynamical fluctuations were observed on the timescale of 1.5 ps, while collective motions and the longest lived population of H-bond partner lifetimes were observed on the order of 20 ps, in agreement with the Maxwell relaxation time. This identifies a mechanism which may aid in understanding the emergence of various complex phenomena arising from transient molecular structures, with implications ranging from the internal dynamics of proteins, to the glass transition, to better understanding the origins of the unique properties of H-bonding liquids. [ABSTRACT FROM AUTHOR]

We studied child malaria treatment practices among mothers living in the District of Yanfolila in southern Mali. For sampling, we first chose five of 13 health areas with probability proportional to size. Then villages, compounds and mothers with at least one child aged 1-5 years were randomly chosen. We assessed the spleen size of one 1-5 year-old child of each mother, collected a thick blood film and recorded the body temperature of every child whose mother thought he/she was sick. 399 mothers in 28 villages were interviewed with a structured questionnaire divided into two parts. If the child had had soumaya (a term previously associated with uncomplicated malaria) during the past rainy season, we asked about signs and symptoms, health-seeking behaviour (who the mother consulted first) and treatment. If not, information about knowledge of the disease and treatment to be given was collected. 86% of the mothers interviewed stated that their child had been sick and almost half of them had had soumaya. All mothers named at least one sign by which they recognized the disease. Vomiting, fever and dark urine/yellow eyes/jaundice were the three most common signs mentioned. 75.8% managed their child's disease at home and used both traditional and modern treatment. The most common anti-malarial drug was chloroquine, often given at inappropriate dosage. The sensitivity and specificity of the mothers' diagnosis was poor, although this might be explained by the large percentage of children who had already been treated at the time of the interview. The results of our survey call for prompt educational action for the correct treatment of uncomplicated malaria/soumaya, particularly for mothers and possibly for shopkeepers. The high spleen rate (58.1%) among randomly selected children confirms that malaria is a common disease in this area. Improved case-management at home could only be beneficial. [ABSTRACT FROM AUTHOR]

The characteristic nanoscale dynamics of the alkyl side groups in the light‐emitting polymer poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylene vinylene] have been investigated using quasi‐elastic neutron scattering (QENS). The measurements were taken below the polymer's glass transition (T ≤ Tg ≃ 353 K), where the main backbone is in a rigid state and does not contribute to the broadening of the QENS signal. An analytical diffusion model consisting of a static term and two dynamical components, characterizing the flexible side groups, provide an excellent fit to the experimental data. The two observed dynamical processes are all localized in character, with no meaningful dependence on temperature. The faster process, with characteristic timescale of ∼18 ps at room temperature (RT), can be linked to the average mobility of the terminal protons of the alkyl chain, while the slower process, with characteristic timescale of ∼170 ps at RT, to those protons at the other end of the alkyl chain, closest to the backbone. While the fraction of mobile protons contributing to the QENS signal increases with increasing temperature, the characteristic timescale and confining volume within which the protons are able to move locally depend chiefly on the polymer conformational state. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47394. [ABSTRACT FROM AUTHOR]

The dynamics of water in polyethylene oxide (PEO)/LiCl solution has been studied with quasielastic neutron scattering experiments and molecular dynamics (MD) simulations. Two different time scales of water diffusion representing interfacial water and bulk water dynamics have been identified. The measured diffusion coefficient of interfacial water remained 5-10 times smaller than that of bulk water, but both were slowed by approximately 50% in the presence of Li+. Detailed analysis of MD trajectories suggests that Li+ is favorably found at the surface of the hydration layer, and the probability to find the caged Li+ configuration formed by the PEO is lower than for the noncaged Li+-PEO configuration. In both configurations, however, the slowing down of water molecules is driven by reorienting water molecules and creating water-Li+ hydration complexes. Performing the MD simulation with different ions (Na+ and K+) revealed that smaller ionic radius of the ions is a key factor in disrupting the formation of PEO cages by allowing spaces for water molecules to come in between the ion and PEO. [ABSTRACT FROM AUTHOR]

Little is known about folk perception of pearl millet livestock fodder status across the Niger republic. Thus, this work assesses farmers' perceptions of the main pearl millet accessions fodder performance features in Niger. To that end, we: (i) Identify farmers' criteria for choosing pearl millet accessions fodder-profile, (ii) Analyze the farmer preferences for pearl millet accessions adapted to local cropping systems, and (iii) Analyze current cropping systems. Data have been derived from semi-structured surveys based on individual and focus group interviews of 508 stakeholders which were sampled from seven major ethnic groups across the eight country regions. Generated database was submitted to multivariate analysis in XLSTAT software. As results, the farmers' perception of a fodder profile may combine long and wide leaves, abundant tillers, slender stems, coupled to a large biomass and a plant capacity to regrow after grazing or mowing. Height accessions were agro-ecologically and socio-culturally chosen and valued by Farmers across the country, i.e. Haïni Kirey at Tillabéry, Niamey and Dosso, HKP and Guerguéra at Tahoua, Ankoutess at Agadez, Goudiss and Môro at Diffa, Batoukouché at Zinder, and HKP and Zongo at Maradi. Distinctive producers' groups occur despite wider similarities in crop management practices. The prominent cropping system associated pearl millet to cowpea or groundnut. Therefore, identifying, characterizing or improving pearl millet accessions with a grain or fodder profile requires significant involvement of the farmers across Niger., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors.)

Background: An ethnobotanical study was conducted in the eight regions of Niger to identify local knowledge variation of millet (Pennisetum glaucum (L.) R. Br) uses. In fact, the level of individual knowledge can be affected by many factors such as gender, age, ethnicity, occupation, religious and cultural beliefs, etc. This study documented indigenous knowledge of millet uses in Niger and aimed specifically to (i) identify the different types of millet organ uses and (ii) assess the variation of local knowledge of millet uses along with ethnicity, occupation, and age., Methods: The data were collected in 32 major millet-producing villages in Niger through individual semi-structured interviews and focus group discussions. About 508 individuals from 5 ethnic groups were interviewed. The assessment of the knowledge was performed by calculating five ethnobotanical indices such as the number of reported uses by parts of the plant (RU), the use-value of the parts of the plant (PPV), the specific use-value (SU), the intraspecific use-value (IUV), and the relative frequency of citations (FRC). Data were analyzed using descriptive, univariate, and multivariate statistical analyses., Results: The results indicated a significant variation in uses across ethnic groups (H = 38.14, P = 0.000) and socio-occupational categories (H = 6.80, P = 0.033). The Hausa, Kanuri, and Zarma-Sonhrai ethnic groups, farmers were the largest users of the species. Dietary (51.40%) and forage (40.35%) were the most reported uses. The most commonly used parts of the plant were the stubble (74.92%) and grains (73.68%)., Conclusions: The study showed the importance of P. glaucum in the daily life of local people. It also confirmed the uneven distribution of indigenous knowledge of millet uses in Niger due to social factors. Now, the challenge is how to incorporate these social differences in knowledge of millet uses in view to sustainable management and conservation of local genetic resources of millet. Finally, this work could be an important decision-making tool for future millet valuing.