Exponential energy decay of solutions for a system of viscoelastic wave equations of Kirchhoff type with strong damping

The initial boundary value problem for a system of viscoelastic wave equations of Kirchhoff type with strong damping is considered. We prove that, under suitable assumptions on relaxation functions and certain initial data, the decay rate of the solutions energy is exponential

Perceptions paysannes et impacts des changements climatiques sur la production et la diversité variétale de l’igname dans la zone aride du nord-ouest du Bénin

L’igname (Dioscorea spp.) est une culture vivrière de grande importance pour la sécurité alimentaire au Bénin. Cependant, sa production dans le département de l’Atakora (extrême Nord-Ouest) est sérieusement affectée par les changements climatiques. Pour analyser les perceptions paysannes des changements climatiques, documenter les impacts de ceux-ci sur la production des ignames et les stratégies d'adaptation développées pour y faire face, quinze (15) villages ont été sélectionnés au hasard et explorés. Les producteurs ont signalé des fluctuations de température et de pluviométrie, une augmentation de la température et une diminution de la pluviométrie corroborées par l’analyse des données météorologiques. L’âge et le genre influencent significativement la perception paysanne des changements climatiques. Les impacts les plus importants sont la baisse de rendement, la pourriture des tubercules et des semences, l’appauvrissement et la dégradation des sols et la prolifération des insectes et ravageurs. Les stratégies adoptées inclus entre autres le paillage des buttes, le déplacement vers les zones humides et l’utilisation de bonnes pratiques culturales et de la diversité variétale. Cette capacité d’adaptation des producteurs pourrait être accompagnée par les politiques publiques mais ceux-ci devront tenir compte des différents facteurs influençant la capacité d’adaptation des producteurs déterminés au cours de cette étude.Mots clés : Critères de préférence, cultivars tolérants, sécheresse, stratégies d’adaptation, variabilité climatique

Accuracy of Clinical Techniques for Evaluating Lower Limb Sensorimotor Functions Associated With Increased Fall Risk

BackgroundIn prior work, laboratoryâ based measures of hip motor function and ankle proprioceptive precision were critical to maintaining unipedal stance and fall/fallâ related injury risk. However, the optimal clinical evaluation techniques for predicting these measures are unknown.ObjectiveTo evaluate the diagnostic accuracy of common clinical maneuvers in predicting laboratoryâ based measures of frontal plane hip rate of torque development (HipRTD) and ankle proprioceptive thresholds (AnkPRO) associated with increased fall risk.DesignProspective, observational study.SettingBiomechanical research laboratory.ParticipantsA total of 41 older subjects (aged 69.1 ± 8.3 years), 25 with varying degrees of diabetic distal symmetric polyneuropathy and 16 without.AssessmentsClinical hip strength was evaluated by manual muscle testing (MMT) and lateral plank time, defined as the number of seconds that the laterally lying subject could lift the hips from the support surface. Foot/ankle evaluation included Achilles reflex and vibratory, proprioceptive, monofilament, and pinprick sensations at the great toe.Main Outcome MeasuresHipRTD, abduction and adduction, using a custom wholeâ body dynamometer. AnkPRO determined with subjects standing using a foot cradle system and a staircase series of 100 frontal plane rotational stimuli.ResultsPearson correlation coefficients (r) and receiver operator characteristic (ROC) curves revealed that LPT correlated more strongly with HipRTD (r/P = 0.61/1.0°.ConclusionsLPT is a more effective measure of HipRTD than MMT. Similarly, clinical vibratory sense and monofilament testing are effective measures of AnkPRO, whereas clinical proprioceptive sense is not.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146801/1/pmrj331.pd

Malaria Antifolate Resistance With Contrasting Plasmodium Falciparum Dihydrofolate Reductase (DHFR) Polymorphisms in Humans and Anopheles Mosquitoes

Surveillance for drug-resistant parasites in human blood is a major effort in malaria control. Here we report contrasting antifolate resistance polymorphisms in Plasmodium falciparum when parasites in human blood were compared with parasites in Anopheles vector mosquitoes from sleeping huts in rural Zambia. DNA encoding P. falciparum dihydrofolate reductase (EC 1.5.1.3) was amplified by PCR with allele-specific restriction enzyme digestions. Markedly prevalent pyrimethamine-resistant mutants were evident in human P. falciparum infections - S108N (\u3e90%), with N51I, C59R, and 108N+51I+59R triple mutants (30-80%). This resistance level may be from selection pressure due to decades of sulfadoxine/pyrimethamine use in the region. In contrast, cycloguanil-resistant mutants were detected in very low frequency in parasites from human blood samples - S108T (13%), with A16V and 108T+16V double mutants (∼4%). Surprisingly, pyrimethamine-resistant mutants were of very low prevalence (2-12%) in the midguts of Anopheles arabiensis vector mosquitoes, but cycloguanil-resistant mutants were highly prevalent - S108T (90%), with A16V and the 108T+16V double mutant (49-57%). Structural analysis of the dihydrofolate reductase by in silico modeling revealed a key difference in the enzyme within the NADPH binding pocket, predicting the S108N enzyme to have reduced stability but the S108T enzyme to have increased stability. We conclude that P. falciparum can bear highly host-specific drug-resistant polymorphisms, most likely reflecting different selective pressures found in humans and mosquitoes. Thus, it may be useful to sample both human and mosquito vector infections to accurately ascertain the epidemiological status of drug-resistant alleles

Structural basis for conductance by the archaeal aquaporin AqpM at 1.68 Å

To explore the structural basis of the unique selectivity spectrum and conductance of the transmembrane channel protein AqpM from the archaeon Methanothermobacter marburgensis, we determined the structure of AqpM to 1.68-A resolution by x-ray crystallography. The structure establishes AqpM as being in a unique subdivision between the two major subdivisions of aquaporins, the water-selective aquaporins, and the water-plus-glycerol-conducting aquaglyceroporins. In AqpM, isoleucine replaces a key histidine residue found in the lumen of water channels, which becomes a glycine residue in aquaglyceroporins. As a result of this and other side-chain substituents in the walls of the channel, the channel is intermediate in size and exhibits differentially tuned electrostatics when compared with the other subfamilies

Genetic diversity and population structure of cacao (Theobroma cacao L.) germplasm from Sierra Leone and Togo based on KASP- SNP genotyping

Open Access JournalBackground Cacao (Theobroma cacao L.) is a tropical tree species belonging to Malvaceae family and originated in the lowland rainforests of the Amazon. It is one of the major agricultural commodities contributing towards the GDP (gross domestic product) of West African countries contributing about 70% of world’s production. Methodology A sample of 376 cacao (Theobroma cacao L.) germplasm accessions (235 from Sierra Leone and 141 from Togo) collected from different seed gardens and farmers’ fields across the cacao producing states/regions of these countries were assembled for genetic diversity and population structure studies using single nucleotide polymorphism (SNP) markers. The 376 cacao accessions were genotyped using 20 highly informative and reproducible KASP-SNPs markers. The genetic diversity among different accessions was assessed using three complementary clustering methods including the model-based population structure, discriminant analysis of principal components (DAPC), and phylogenetic trees. A network analysis was further carried out to understand the genetic relationships among cacao accessions from Sierra Leone and Togo. Analysis of molecular variance (AMOVA) was carried out to estimate the genetic differentiation among and within groups. Results The STRUCTURE and DAPC exhibited some consistency in the allocation of accessions in subpopulations or groups, although some discrepancy was identified in the grouping based on these two methods. Hierarchical clustering analysis grouped all the individuals into two major groups and represented several sub-clusters. AMOVA revealed high genetic diversity (86%) within accessions. A high rate of mislabeling/duplicate genotype names was revealed in both countries, which may be attributed to errors from the sources of introduction, labeling errors, and lost labels. Conclusion This study demonstrates the use of KASP-SNPs for fingerprinting that can help identify mislabeled accessions and provide strong evidence for improving the accuracy and efficiency in cacao germplasm management as well as distribution of correct materials to farmers

Aquaporin-4 and brain edema.

Aquaporin-4 (AQP4) is a water-channel protein expressed strongly in the brain, predominantly in astrocyte foot processes at the borders between the brain parenchyma and major fluid compartments, including cerebrospinal fluid (CSF) and blood. This distribution suggests that AQP4 controls water fluxes into and out of the brain parenchyma. Experiments using AQP4-null mice provide strong evidence for AQP4 involvement in cerebral water balance. AQP4-null mice are protected from cellular (cytotoxic) brain edema produced by water intoxication, brain ischemia, or meningitis. However, AQP4 deletion aggravates vasogenic (fluid leak) brain edema produced by tumor, cortical freeze, intraparenchymal fluid infusion, or brain abscess. In cytotoxic edema, AQP4 deletion slows the rate of water entry into brain, whereas in vasogenic edema, AQP4 deletion reduces the rate of water outflow from brain parenchyma. AQP4 deletion also worsens obstructive hydrocephalus. Recently, AQP4 was also found to play a major role in processes unrelated to brain edema, including astrocyte migration and neuronal excitability. These findings suggest that modulation of AQP4 expression or function may be beneficial in several cerebral disorders, including hyponatremic brain edema, hydrocephalus, stroke, tumor, infection, epilepsy, and traumatic brain injury

Phenotypic and molecular assessment of genetic structure and diversity in a panel of winged yam (Dioscorea alata) clones and cultivars

Open Access Journal; Published online: 03 Dec 2019A better understanding of the structure and extent of genetic variability in a breeding population of a crop is essential for translating genetic diversity to genetic gain. We assessed the nature and pattern of genetic variability and differentiation in a panel of 100 winged-yam (Dioscorea alata) accessions using 24 phenotypic traits and 6,918 single nucleotide polymorphism (SNP) markers. Multivariate analysis for phenotypic variability indicated that all phenotypic traits assessed were useful in discriminating the yam clones and cultivars. Cluster analysis based on phenotypic data distinguished two significant groups, while a corresponding analysis with SNP markers indicated three genetic groups. However, joint analysis for the phenotypic and genotypic data provided three clusters that could be useful for the identification of heterotic groups in the D. alata breeding program. Our analysis for phenotypic and molecular level diversity provided valuable information about overall diversity and variation in economically important traits useful for establishing crossing panels with contrasting traits of interest. The selection and hybridization of parental lines from the different heterotic groups identified would facilitate maximizing diversity and exploiting population heterosis in the D. alata breeding program

Genome-wide association study of root mealiness and other texture-associated traits in cassava

Open Access Journal; Published online: 17 Dec 2021Cassava breeders have made significant progress in developing new genotypes with improved agronomic characteristics such as improved root yield and resistance against biotic and abiotic stresses. However, these new and improved cassava (Manihot esculenta Crantz) varieties in cultivation in Nigeria have undergone little or no improvement in their culinary qualities; hence, there is a paucity of genetic information regarding the texture of boiled cassava, particularly with respect to its mealiness, the principal sensory quality attribute of boiled cassava roots. The current study aimed at identifying genomic regions and polymorphisms associated with natural variation for root mealiness and other texture-related attributes of boiled cassava roots, which includes fibre, adhesiveness (ADH), taste, aroma, colour, and firmness. We performed a genome-wide association (GWAS) analysis using phenotypic data from a panel of 142 accessions obtained from the National Root Crops Research Institute (NRCRI), Umudike, Nigeria, and a set of 59,792 high-quality single nucleotide polymorphisms (SNPs) distributed across the cassava genome. Through genome-wide association mapping, we identified 80 SNPs that were significantly associated with root mealiness, fibre, adhesiveness, taste, aroma, colour and firmness on chromosomes 1, 4, 5, 6, 10, 13, 17 and 18. We also identified relevant candidate genes that are co-located with peak SNPs linked to these traits in M. esculenta. A survey of the cassava reference genome v6.1 positioned the SNPs on chromosome 13 in the vicinity of Manes.13G026900, a gene recognized as being responsible for cell adhesion and for the mealiness or crispness of vegetables and fruits, and also known to play an important role in cooked potato texture. This study provides the first insights into understanding the underlying genetic basis of boiled cassava root texture. After validation, the markers and candidate genes identified in this novel work could provide important genomic resources for use in marker-assisted selection (MAS) and genomic selection (GS) to accelerate genetic improvement of root mealiness and other culinary qualities in cassava breeding programmes in West Africa, especially in Nigeria, where the consumption of boiled and pounded cassava is low