The integration of unmanned aerial vehicles (UAVs) into agriculture has emerged as a transformative approach to enhance resource efficiency and enable precision farming. UAVs are used for various agricultural tasks, including monitoring, mapping and spraying of pesticides, providing detailed data that support targeted and sustainable practices. However, effective deployment of UAVs in these applications faces complex control challenges. This paper presents a comprehensive review of UAVs in agricultural applications, highlighting the sophisticated control strategies required to address these challenges. Key obstacles, such as modelling inaccuracies, unstable centre of gravity (COG) due to shifting payloads, fluid sloshing within pesticide tanks and external disturbances like wind, are identified and analysed. The review delves into advanced control methodologies, with particular focus on adaptive algorithms, backstepping control and machine learning-enhanced systems, which collectively enhance UAV stability and responsiveness in dynamic agricultural environments. Through an in-depth examination of flight dynamics, stability control and payload adaptability, this paper highlights how UAVs can achieve precise and reliable operation despite environmental and operational complexities. The insights drawn from this review underscore the importance of integrating adaptive control frameworks and real-time sensor data processing, enabling UAVs to autonomously adjust to changing conditions and ensuring optimal performance in agriculture. Future research directions are proposed, advocating for the development of control systems that enhance UAV resilience, accuracy and sustainability. By addressing these control challenges, UAVs have the potential to significantly advance precision agriculture, offering practical and environmental benefits crucial to sustaining global food production demands.

Suicidal and self-harming behaviours present a significant challenge for mental health services. Recent national guidelines advocate abandoning tools based on box-ticking and a move towards a personalised psychosocial assessment. This article examines evidence from theoretical and empirical research in this area and attempts to integrate it by introducing the source–problem–solution–motive (SPSM) model. The model, which builds on the contributions of other suicidologists, specially Jean Baechler, could be used as a framework for the assessment and management of these behaviours. The four stages of the model provide a comprehensive approach that enables an exploration of the internal logic of the behaviour. The model covers ‘because’ and ‘in-order-to’ motives. This allows a personalised approach, but also a structured one that can be taught and generalised.

The extended $3/2$ short rate model is a mean reverting model of the short rate which, for suitably chosen parameters, permits a sensible term structure of bond yields and closed-form valuation formulae of zero-coupon bonds and options. This article supplies proofs of the formulae for the expected present values of future cash flows under the real-world probability measure, known as actuarial valuation. Finally, we give formulae for asymptotic levels of bond yields and formulae for bond option prices for the extended $3/2$ model, under particular conditions on its parameters.

The University of California (UC) Davis Clinical and Translational Science Center has established the “Join the Team” model, a Clinical Research Coordinator workforce pipeline utilizing a community-based approach. The model has been extensively tested at UC Davis and demonstrated to generate a viable pathway for qualified candidates for employment in clinical research. The model combines the following elements: community outreach; professional training materials created by the Association for Clinical Research Professionals and adapted to the local environment; financial support to trainees to encourage ethnic and socioeconomic diversity; and internship/shadowing opportunities. The program is tailored for academic medical centers (AMCs) in recognition of administrative barriers specific to AMCs. UC Davis’s model can be replicated at other locations using information in this article, such as key program features and barriers faced and surmounted. We also discuss innovative theories for future program iterations.

Following the introduction of the one-child policy in China, the capital-labor ratio of China increased relative to that of India, while FDI/GDP inflows to China versus India simultaneously declined. These observations are explained in the context of a simple neoclassical overlapping generations paradigm. The adjustment mechanism works as follows: the reduction in the growth rate of the (urban) labor force due to the one-child policy increases the capital per worker inherited from the previous generation. The resulting increase in China’s domestic capital-labor ratio thus "crowds out" the need for foreign direct investment (FDI) in China relative to India. Our paper is a contribution to the nascent literature exploring demographic transitions and their effects on FDI flows.

Elastin function is to endow vertebrate tissues with elasticity so that they can adapt to local mechanical constraints. The hydrophobicity and insolubility of the mature elastin polymer have hampered studies of its molecular organisation and structure-elasticity relationships. Nevertheless, a growing number of studies from a broad range of disciplines have provided invaluable insights, and several structural models of elastin have been proposed. However, many questions remain regarding how the primary sequence of elastin (and the soluble precursor tropoelastin) governs the molecular structure, its organisation into a polymeric network, and the mechanical properties of the resulting material. The elasticity of elastin is known to be largely entropic in origin, a property that is understood to arise from both its disordered molecular structure and its hydrophobic character. Despite a high degree of hydrophobicity, elastin does not form compact, water-excluding domains and remains highly disordered. However, elastin contains both stable and labile secondary structure elements. Current models of elastin structure and function are drawn from data collected on tropoelastin and on elastin-like peptides (ELPs) but at the tissue level, elasticity is only achieved after polymerisation of the mature elastin. In tissues, the reticulation of tropoelastin chains in water defines the polymer elastin that bears elasticity. Similarly, ELPs require polymerisation to become elastic. There is considerable interest in elastin especially in the biomaterials and cosmetic fields where ELPs are widely used. This review aims to provide an up-to-date survey of/perspective on current knowledge about the interplay between elastin structure, solvation, and entropic elasticity.

Soil amelioration via strategic deep tillage is occasionally utilized within conservation tillage systems to alleviate soil constraints, but its impact on weed seed burial and subsequent growth within the agronomic system is poorly understood. This study assessed the effects of different strategic deep-tillage practices, including soil loosening (deep ripping), soil mixing (rotary spading), or soil inversion (moldboard plow), on weed seed burial and subsequent weed growth, compared with a no-till control. The tillage practices were applied in 2019 at Yerecoin and Darkan, WA, and data on weed seed burial and growth were collected during the following 3-yr winter crop rotation (2019 to 2021). Soil inversion buried 89% of rigid ryegrass (Lolium rigidum Gaudin) and ripgut brome (Bromus diandrus Roth) seeds to a depth of 10 to 20 cm at both sites, while soil loosening and mixing left between 31% and 91% of the seeds in the top 0 to 10 cm of soil, with broad variation between sites. Few seeds were buried beyond 20 cm despite tillage working depths exceeding 30 cm at both sites. Soil inversion reduced the density of L. rigidum to <1 plant m−2 for 3 yr after strategic tillage. Bromus diandrus density was initially reduced to 0 to 1 plant m−2 by soil inversion, but increased to 4 plants m−2 at Yerecoin in 2020 and 147 plants at Darkan in 2021. Soil loosening or mixing did not consistently decrease weed density. The field data were used to parameterize a model that predicted weed density following strategic tillage with greater accuracy for soil inversion than for loosening or mixing. The findings provide important insights into the effects of strategic deep tillage on weed management in conservational agricultural systems and demonstrate the potential of models for optimizing weed management strategies.

South Africa is a net importer of fertilizer products, importing all of its potassium, as well as 60–70% of its nitrogen requirements. Thus, domestic prices are impacted significantly by international prices, shipping costs, and exchange rates. Producing these fertilizers locally would be far more economical. Phlogopite, a rich source of potassium, is discarded in large quantities during mining operations; the objective of the present study, therefore, was to determine the acid-leaching characteristics and behavior of phlogopite as a means of releasing potassium. Phlogopite samples were leached with nitric acid (source of nitrogen for fertilizers) at various concentrations, temperatures, and reaction times. The feed phlogopite and leached residue samples corresponding to conversions of 14% (LP1), 44% (LP2), and 100% (LP3) were collected and analyzed using X-ray fluorescence spectroscopy (XRF), X-ray diffractometry (XRD), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), Brunauer–Emmett–Teller surface area and porosity analysis (BET), thermogravimetric analysis (TGA), and field emission gun-scanning electron microscopy (FEG-SEM). The feed phlogopite was highly crystalline. The absence of defects in the lattice meant that the motion of H+ atoms penetrating into the lattice was restricted, suggesting internal diffusion-controlled leaching. Furthermore, results obtained from the various analytical techniques corroborated each other in terms of the release of cations during leaching. All leaching experiments were conducted batchwise, in a closed system. The gravimetric data from the experiments were used to identify a suitable model which predicts accurately the leaching behavior. The reaction was found to be internal diffusion-controlled, and the D1 model, which represents one-dimensional diffusion through a flat plate, predicts the leaching behavior most accurately. The observed activation energies (Ea) and pre-exponential constants (k0) varied with initial nitric acid concentration ([H+]0).

Fe(II)–Fe(III) green rust identified in soil as a natural mineral is responsible for the blue-green color of gley horizons, and exerts the main control on Fe dynamics. A previous EXAFS study of the structure of the mineral confirmed that the mineral belongs to the group of green rusts (GR), but showed that there is a partial substitution of Fe(II) by Mg(II), which leads to the general formula of the mineral: ${[{\text{Fe}}_{1-x}^{2+}{\text{Fe}}_x^{3+}{\text{Mg}}_y{(\text{OH})}_{2+2y}]}^{x+}{[x{\text{OH}}^{-}\cdot m{\text{H}}_2\text{O}]}^{x-}$${[{\rm{Fe}}_{1 - x}^{2 + }{\rm{Fe}}_x^{3 + }{\rm{M}}{{\rm{g}}_y}{({\rm{OH}})_{2 + 2y}}]^{x + }}{[x{\rm{O}}{{\rm{H}}^ - } \cdot m{{\rm{H}}_2}{\rm{O}}]^{x - }}$. The regular binary solid-solution model proposed previously must be extended to ternary, with provision for incorporation of Mg in the mineral. Assuming ideal substitution between Mg(II) and Fe(II), the chemical potential of any Fe(II)-Fe(III)-Mg(II) hydroxy-hydroxide is obtained as: $\text{μ}=X_1{\text{μ}}_{\text{1}}^{\text{o}}+X_2{\text{μ}}_{\text{2}}^{\text{o}}+X_3{\text{μ}}_{\text{3}}^{\text{o}}+\text{R}T[X_1\text{ln}{X}_1+X_2\text{ln}{X}_2+X_3\text{ln}{X}_3]+A_{12}{X}_2(1-X_2)$${\rm{\mu }} = {X_1}{\rm{\mu }}_{\rm{1}}^{\rm{o}} + {X_2}{\rm{\mu }}_{\rm{2}}^{\rm{o}} + {X_3}{\rm{\mu }}_{\rm{3}}^{\rm{o}} + {\rm{R}}T[{X_1}{\rm{ln}}{X_1} + {X_2}{\rm{ln}}{X_2} + {X_3}{\rm{ln}}{X_3}] + {A_{12}}{X_2}(1 - {X_2})$. All experimental data show that the mole ratio X2 = Fe(III)/[Fetotal + Mg] is constrained (1) structurally and (2) geochemically. Structurally, Fe(III) ions cannot neighbor each other, which leads to the inequality $X_2\alpha \raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right..$${X_2}\leqslant {\raise0.5ex\hbox{$\scriptstyle 1$}\kern-0.1em/\kern-0.15em\lower0.25ex\hbox{$\scriptstyle 3$}}.$ Geochemically, Fe(III) cannot be too remote from each other for GR to form as Fe(OH)2 and Mg(OH)2 are very soluble, so $X_2\alpha \raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$4$}\right.$${X_2}\geqslant {\raise0.5ex\hbox{$\scriptstyle 1$}\kern-0.1em/\kern-0.15em\lower0.25ex\hbox{$\scriptstyle 4$}}$. A linear relationship is obtained between the Gibbs free energy of formation of GR, normalized to one Fe atom, and the electronegativity ϰ of the interlayer anion, as: μo/n = −76.887ϰ — 491.5206 (r2 = 0.9985, N = 4), from which the chemical potential of the mineral fougerite μ is obtained in the limiting case X3 = 0, and knowing ${\text{μ}}_{\text{1}}^{\text{o}}=-489.8$${\rm{\mu }}_{\rm{1}}^{\rm{o}} = - 489.8$ kJmol−1 for Fe(OH)2, and ${\text{μ}}_{\text{3}}^{\text{o}}=-832.16$${\rm{\mu }}_{\rm{3}}^{\rm{o}} = - 832.16$ kJmol−1 for Mg(OH)2, the two unknown thermodynamic parameters of the solid-solution model are determined as

${\text{μ}}_{\text{2}}^{\text{o}}=+119.18{\text{kJmol}}^{-1}$${\rm{\mu }}_{\rm{2}}^{\rm{o}} = + 119.18\;{\rm{kJmo}}{{\rm{l}}^{ - 1}}$ for Fe(OH)3 (virtual), and A12 = −1456.28 kJmol−1 (non-ideality parameter). From Mössbauer in situ measurements and our model, the chemical composition of the GR mineral is constrained into a narrow range and the soil solutions-mineral equilibria computed. Soil solutions appear to be largely overstaurated with respect to the two forms observed.