648 research outputs found
E151 (sym15), A Pleiotropic Mutant of Pea (Pisum sativum L.), Displays Low Nodule Number, Enhanced Mycorrhizae, Delayed Lateral Root Emergence, and High Root Cytokinin Levels
In legumes, the formation of rhizobial and mycorrhizal root symbioses is a highly regulated process which requires close communication between plant and microorganism. Plant mutants that have difficulties establishing symbioses are valuable tools for unravelling the mechanisms by which these symbioses are formed and regulated. Here E151, a mutant of Pisum sativum cv. Sparkle, was examined to characterize its root growth and symbiotic defects. The symbioses in terms of colonization intensity, functionality of micro-symbionts, and organ dominance were compared between the mutant and wild type. The endogenous cytokinin (CK) and abscisic acid (ABA) levels and the effect of the exogenous application of these two hormones were determined. E151 was found to be a low and delayed nodulator, exhibiting defects in both the epidermal and cortical programmes though a few mature and functional nodules develop. Mycorrhizal colonization of E151 was intensified, although the fungal functionality was impaired. Furthermore, E151 displayed an altered lateral root (LR) phenotype compared with that of the wild type whereby LR emergence is initially delayed but eventually overcome. No differences in ABA levels were found between the mutant and the wild type, but non-inoculated E151 exhibited significantly high CK levels. It is hypothesized that CK plays an essential role in differentially mediating the entry of the two micro-symbionts into the cortex; whereas it would inhibit the entry of the rhizobia in that tissue, it would promote that of the fungus. E151 is a developmental mutant which may prove to be a useful tool in further understanding the role of hormones in the regulation of beneficial root symbioses
Electrode Polarization Effects in Broadband Dielectric Spectroscopy
In the present work, we provide broadband dielectric spectra showing strong
electrode polarization effects for various materials, belonging to very
different material classes. This includes both ionic and electronic conductors
as, e.g., salt solutions, ionic liquids, human blood, and
colossal-dielectric-constant materials. These data are intended to provide a
broad data base enabling a critical test of the validity of phenomenological
and microscopic models for electrode polarization. In the present work, the
results are analyzed using a simple phenomenological equivalent-circuit
description, involving a distributed parallel RC circuit element for the
modeling of the weakly conducting regions close to the electrodes. Excellent
fits of the experimental data are achieved in this way, demonstrating the
universal applicability of this approach. In the investigated ionically
conducting materials, we find the universal appearance of a second dispersion
region due to electrode polarization, which is only revealed if measuring down
to sufficiently low frequencies. This indicates the presence of a second
charge-transport process in ionic conductors with blocking electrodes.Comment: 9 pages, 6 figures, experimental data are provided in electronic form
(see "Data Conservancy"
Factors associated with failed ‘test of cure’ in the NHS cervical screening programme: a retrospective cohort study
Objective: To determine predictive factors associated with failed ‘test of cure’ (TOC) in the NHS Cervical Screening Programme (NHSCSP). Methods: Retrospective cohort study of all patients treated by large loop excision of transformation zone (LLETZ) between 1st April 2014 and 1st April 2019. Those with no documented HPV genotype on referral, no TOC outcome, those having a hysterectomy, chemotherapy and/or radiotherapy were excluded from final analysis. Results: Patients referred with a singular HPV genotype of HPV 16, HPV 18, or HPV Other types (HPV O) were significantly more likely to pass TOC than those referred with multiple HPV genotypes (p 51 yrs. and infection with multiple hr-HPV types were predictors of post treatment hr-HPV persistence. Knowledge of HPV genotype both at referral, and following treatment, could allow a more individualised, and patient-centred, approach to both the management and follow up of CIN. HPV genotype should be reported as standard on all cervical screening sample results. The term HPV O should not be utilised and instead actual HPV genotype should be reported. This would enable us to optimise not only future research but would also allow future monitoring of the efficacy of vaccination programmes
Nondissipative Drag Conductance as a Topological Quantum Number
We show in this paper that the boundary condition averaged nondissipative
drag conductance of two coupled mesoscopic rings with no tunneling, evaluated
in a particular many-particle eigenstate, is a topological invariant
characterized by a Chern integer. Physical implications of this observation are
discussed.Comment: 4 pages, no figure. Title modified and significant revision made to
the text. Final version appeared in PR
Effects of the field modulation on the Hofstadter's spectrum
We study the effect of spatially modulated magnetic fields on the energy
spectrum of a two-dimensional (2D) Bloch electron. Taking into account four
kinds of modulated fields and using the method of direct diagonalization of the
Hamiltonian matrix, we calculate energy spectra with varying system parameters
(i.e., the kind of the modulation, the relative strength of the modulated field
to the uniform background field, and the period of the modulation) to elucidate
that the energy band structure sensitively depends on such parameters:
Inclusion of spatially modulated fields into a uniform field leads occurrence
of gap opening, gap closing, band crossing, and band broadening, resulting
distinctive energy band structure from the Hofstadter's spectrum. We also
discuss the effect of the field modulation on the symmetries appeared in the
Hofstadter's spectrum in detail.Comment: 7 pages (in two-column), 10 figures (including 2 tables
Saliva sampling method influences oral microbiome composition and taxa distribution associated with oral diseases
Saliva is a readily accessible and inexpensive biological specimen that enables investigation of the oral microbiome, which can serve as a biomarker of oral and systemic health. There are two routine approaches to collect saliva, stimulated and unstimulated; however, there is no consensus on how sampling method influences oral microbiome metrics. In this study, we analyzed paired saliva samples (unstimulated and stimulated) from 88 individuals, aged 7-18 years. Using 16S rRNA gene sequencing, we investigated the differences in bacterial microbiome composition between sample types and determined how sampling method affects the distribution of taxa associated with untreated dental caries and gingivitis. Our analyses indicated significant differences in microbiome composition between the sample types. Both sampling methods were able to detect significant differences in microbiome composition between healthy subjects and subjects with untreated caries. However, only stimulated saliva revealed a significant association between microbiome diversity and composition in individuals with diagnosed gingivitis. Furthermore, taxa previously associated with dental caries and gingivitis were preferentially enriched in individuals with each respective disease only in stimulated saliva. Our study suggests that stimulated saliva provides a more nuanced readout of microbiome composition and taxa distribution associated with untreated dental caries and gingivitis compared to unstimulated saliva
Dynamic Critical Behavior of an Extended Reptation Dynamics for Self-Avoiding Walks
We consider lattice self-avoiding walks and discuss the dynamic critical
behavior of two dynamics that use local and bilocal moves and generalize the
usual reptation dynamics. We determine the integrated and exponential
autocorrelation times for several observables, perform a dynamic finite-size
scaling study of the autocorrelation functions, and compute the associated
dynamic critical exponents . For the variables that describe the size of the
walks, in the absence of interactions we find in two dimensions
and in three dimensions. At the -point in two dimensions
we have .Comment: laTeX2e, 32 pages, 11 eps figure
Literature review – assessing groundwater recharge estimates under conventional tillage and conservation agriculture
The purpose of this review is to identify studies from across the world that evaluated the impact of
conservation agriculture (CA) on potential groundwater recharge in comparison to conventional tillage
(CT), taking into consideration the techniques that have been used in measuring the soil or
groundwater fluxes. In this review, we quantify case studies in which direct and indirect methods have
been used to calculate a direct or proxy value of groundwater recharge under the different agricultural
treatments of CA and CT.
This review revealed that CA systems have the potential to improve infiltration or deep drainage and
therefore potential recharge to the groundwater as evidenced by 54% of the case studies, including
all studies (n=5) in the SADC region, however significant proportion of studies, mainly from the
Americas and Europe, also reported either reduced potential recharge or no significant difference
under different treatments. A majority of these studies used infiltration rates as a proxy. This review
demonstrates that consideration on the methods used in estimating infiltration rates is important
when evaluating the impact of agricultural systems on groundwater recharge in different climate
zones. Issues such as the infiltration measurement technique used, timing of the measurements
within the season, rainfall intensity, and soil type, are some of the parameters that must be carefully
stated in studies to allow the infiltration rates within and across treatments to be comparable.
The review revealed a gap in the literature for studies that used direct methods of recharge estimation
to evaluate the impact of CA vs CT treatments. Unsaturated zone techniques provide only estimates
of potential recharge based on drainage rates below the root zone and in some cases, drainage is
diverted laterally and does not reach the water table. Use of direct methods that allow collection of
data from the saturated zone such as groundwater level fluctuations in monitoring boreholes and
environmental tracers such as Cl and stable isotopes of water, would be greatly beneficial to further
our understanding of groundwater recharge processes beneath CA and CT systems. However, direct
observations are more challenging to acquire and do have limitations
Potential of microbiome-based solutions for agrifood systems
Host-associated microbiomes are central to food production systems and human nutrition and health. Harnessing the microbiome may help increase food and nutrient security, enhance public health, mitigate climate change and reduce land degradation. Although several microbiome solutions are currently under development or commercialized in the agrifood, animal nutrition, biotechnology, diagnostics, pharmaceutical and health sectors , fewer products than expected have been successfully commercialized beyond food processing, and fewer still have achieved wider adoption by farming, animal husbandry and other end-user communities. This creates concerns about the translatability of microbiome research to practical applications. Inconsistent efficiency and reliability of microbiome solutions are major constraints for their commercialization and further development, and demands urgent attention
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