bluuebunny/crossref_metadata_2025 huggingface dataset:
Air-stable chiral primary phosphines part (i) synthesis, stability and applications
Authors: Hiney Rachel M. , Ficks Arne , Müller-Bunz Helge , Gilheany Declan G. , Higham Lee J.
Published: January 2023

This article reviews recent findings from our research groups on the preparation and utility of air-stable chiral primary phosphines. Enantiopure primary phosphines (R)-2 and (S)-3 have been synthesized and are remarkably stable to air-oxidation in both the neat state and in solution, by virtue of the extended π-ring system of the binaphthyl backbone. The extent of conjugation was found to be critical to their stability rather than the presence of bulky groups or heteroatoms. Despite this oxidative resistance, the ability to functionalize these atropisomeric primary phosphines remains, and they have proven to be highly useful chiral ligand precursors. Thus the electrophilic dichlorides (R)-8 and (S)-9 have been prepared, and used to synthesize the phosphonites (Rb,Rax)-13a, (Sb,Rax)-13b, (Rb,Sax)-14a and (Sb,Sax)-14b. By contrast, treatment of (R)-2 and (S)-3 with base to generate the phosphides, followed by the addition of a chiral cyclic sulfate gave the hybrid MOP phospholanes (R,R,Rax)-15a, (S,S,Rax)-15b (via their boranes) and the H-MOP phospholanes (R,R,Sax)-17a and (S,S,Sax)-17b respectively. The primary phosphines are also shown to undergo the hydrophosphination reaction: bis(hydroxymethyl)phosphine (R)-20 and the dicyanoethyl (R)-21 derivatives were prepared by the hydrophosphination of (R)-2 with formaldehyde and acrylonitrile respectively. Early results in the asymmetric hydrosilylation of styrene, and the addition of phenylboronic acid to 1-naphthaldehyde, demonstrate the potential of these new ligand libraries.
Main Topics in Entomology: Insects as Disease Vectors
Authors: Manguin S. , Mouchet J. , Carnevale P.
Published: January 2023

A great deal of human and animal diseases is due to pathogens transmitted by insects. Among the deadliest infectious diseases worldwide, malaria and dengue hemorrhagic fever are vector-borne diseases. Many insect vectors belong to the Diptera Order, such as mosquitoes, biting midges, sandflies, blackflies, and tsetse-flies, but insects of other orders can also transmit important pathogens like the lice, fleas, and bloodsucking bugs. Pathogenic agents could be parasites (protozoan, filariae, cestods, etc), bacteria (rickettsiae, borellia, etc), viruses (arboviruses) that undergo a cycle of development inside the insect vector to reach their infective stage. Transmission can be done through the insect's bite with direct inoculation or with pathogens deposited by the insect saliva or faeces on the skin, and entering into their host either through scratching or by active action of the pathogen into the host wound.

For these insect-borne diseases, vector control is one of the first preventive measures, if not the only one in most cases due to the lack of vaccine (except for yellow fever and Japanese encephalitis) and resistance issues in chemoprophylaxis. Therefore, vector control is an integral component of vector-borne disease control programmes. However, in order to reach their full efficiency, vector control operations and programmes must be based on sound knowledge of the targeted vectors (species identification, biology, distribution, etc.), of local and regional ecological context, and socio-cultural conditions of human populations.
Classical Insecticides: Past, Present and Future
Authors: López Ó. , Fernández-Bolaños J. G. , Gil M. V.
Published: January 2023

We present an historical review of the use of classical insecticides, as examples of non-green agrochemicals that must be replaced and their use reviewed. The chapter is divided into two main sections; in the first, the approaches used for insect control before the development of synthetic insecticides are covered. The use of non-rational insecticides, mainly from mineral sources (e.g. sulphur, arsenicals, copper, or boron derivatives) and lacking specificity in most cases is widely reviewed.

The second part of the chapter is focused on the three main families of synthetic insecticides that have dominated the agrochemical sector from the 1940's to nowadays: organochlorine, orgaphosphorus and carbamates. Their syntheses, relative toxicity, selectivity and environmental fate are included.

The high efficiency and economic viability of such compounds allowed an indiscriminate use in crops, household and cattle. Nevertheless, it is strongly highlighted along this chapter that many of such insecticides are bioaccumulated or provoke severe toxicological effects in mammals, fishes and beneficial insects such as bees. It is also discussed the restrictions and bans exerted by the most recognized organizations such as the US EPA, European Union's Committees, or the World Health Organization for reducing or even eliminate their use.
Basic and Applied Aspects of Neonicotinoid Insecticides
Authors: Nauen R. , Jeschke P.
Published: January 2023

Neonicotinoid insecticides are considered the the fastest-growing class of insecticides in modern crop protection since the introduction of pyrethroids, with widespread use against a broad spectrum of sucking and several chewing pests. Seven structurally different neonicotinoid insecticides are commercially availabale. They act selectively as agonists on insect nicotinic acetylcholine receptors (nAChRs), their molecular target site, with little or no binding to vertebrate receptors. Because of the relatively low risk for non-target organisms and environment, the high target-specificity of neonicotinoid insecticides and their versatility in application methods, this important class has to be maintained globally for sustainable integrated pest management strategies and insect resistance management programmes. Combined with innovative concepts for life-cycle management such as optimized formulations, neonicotinoids will be the most important chemical class within the next few years for the control of some of the globally most destructive pest insects in many agronomic cropping systems.
Needles in the Haystack: Exploring Chemical Diversity of Botanical Insecticides
Authors: Isman Murray B. , Paluch Gretchen
Published: January 2023

Prior to the discovery of DDT, botanical insecticides – those prepared directly from plants – represented the majority of pest control products in the farmer's arsenal. Then with the spectacular growth of the agrochemical industry, botanicals were all but trivialized in the pest management marketplace. Research in the field of natural products chemistry indicates that terrestrial plants represent a vast, largely untapped resource with respect to novel chemistry, much of which is presumed to have an ecological function. Many scientists have used these facts to justify the ongoing search for new insecticides derived from plants, even though the actual number of commercially viable botanical insecticides is very small. In this chapter we review the current status of botanical insecticides, their mechanisms of action against pest insects, and the challenges to developing and commercializing new botanical insecticides.
Towards a Healthy Control of Insect Pests: Potential Use of Microbial Insecticides
Authors: Bravo Alejandra , Cristina del Rincon-Castro M. , Ibarra Jorge E. , Soberón Mario
Published: January 2023

Different microbial insect pathogens have been used as insecticides for the control of different insect pests in agriculture and also for the control of insects that are vectors of important human diseases. These microbial pathogens include bacteria, viruses and fungi. These microbes differ in their insect specificity and mode of action. Nevertheless, insecticides based on these microbial insect pathogens have had a limited use in comparison to chemical insecticides. In this chapter we will revise the potential use of some of these microbial pathogens highlighting their mode of action, insect specificity, risk assessments for the environment and also key application practices to assure the development of more healthy insect control products. Bacterial pathogens rely on different virulence factors to invade their hosts. Among these, bacterial toxins are by far the most important virulence factors. Some δ-endotoxins produced by Bacillus thuringensis, have been expressed in transgenic crops resulting in the reduction of the use of chemical insecticides. Other insecticidal toxins from other bacterial species are likely to provide additional tool for insect control in agriculture. Although different viruses and fungi have the potential for use as insect control, their wide use has been limited by their narrow spectrum of action, application practices and in some cases low susceptibility by older larval instars. However, the genetic manipulation of their genomes by the introduction of insect toxins or catabolic enzymes has been shown to significantly improve their insecticidal activity and their potential for wider use as insect control agents.
The Challenge of Green in a Pesticide-Dominant IPM (Integrated Pest Management) World
Authors: Castle S. J. , Prabhaker N.
Published: January 2023

Advances in pest management have supported dramatic Increases in agricultural production that began with the Green Revolution in 1961. Increased irrigation capacity and higher rates of fertilization that contributed to agricultural intensification created a more permissive agro-environment for pest exploitation, yet crop losses have not significantly increased. Pesticides have played a fundamental part in suppressing pest populations, but their role has been better served when used complementarily to natural control rather than exclusively. The excessive dependence on chemical control during the early decades of synthetic organic insecticides was exposed in Rachel Carson's Silent Spring, a book that had a profound cultural effect by raising environmental consciousness, but also by instilling a deep suspicion of agrochemicals and technological innovation in agriculture. Consequently, there has been a tendency to see agrochemicals, and by extension biotech crops, mostly for their destructive or potentially destructive nature and not for the benefit they serve in promoting food security. The concept of green in agriculture must be inclusive not only of concern for the impact that agronomic and pest management practices have on the environment, but for how well global agricultural production is meeting food security and sustainability challenges. Nevertheless, representation of environmental concerns has acted as a vital counterweight to industrialized agriculture and provided the impetus to improve agricultural performance while reducing environmental impact. The development of safer and more effective pesticides along with greater implementation of biotech crops allows unprecedented opportunities to combine with biological control and cultural practices to reduce crop losses and promote a greener IPM.
Animal Models of Parkinson's Disease
Authors: Rideout Hardy J. , Stefanis Leonidas
Published: January 2023

Parkinson's Disease (PD) is the second most common neurodegenerative disorder, characterized by the progressive loss of neurons beginning in the ventral midbrain, eventually spreading to higher cortical areas. Animal models of PD must recapitulate a complex set of motor and non-motor alterations that are the result of degeneration of widespread neuronal circuits and neurotransmitter systems. As expected, no one model has been devised that exhibits all clinical features of PD. Nevertheless, there are multiple model systems that have been developed that accurately reflect specific pathological, neurochemical, or neurophysiological disruptions that have allowed investigators to better understand aspects of the pathogenesis of PD, and begin to develop both symptom-targeted as well as neuroprotective therapeutic strategies. Multiples genetic approaches exist to model the rare familial autosomal dominant (e.g. transgenic and targeted over-expression of the mutant gene of interest; á-synuclein or LRRK2); and recessive cases of PD (targeted deletion of the relevant gene; e.g. parkin, DJ-1, etc.). Alternatively, toxins causing broad or dopamine neuron-specific mitochondrial dysfunction have been employed to model the complex I deficiency reported in sporadic cases of PD; or those that impair proteasomal-based protein degradation effectively model the formation of neuronal Lewy bodies. In this chapter we will present each class of PD animal model, their strengths and weaknesses, as well as insights gained from these approaches into the pathogenesis and treatment of PD.
Animal Models and the Pathogenesis of Parkinson's Disease
Authors: Castaño José G. , Iglesias Teresa , de Yébenes Justo G.
Published: January 2023

Parkinson's disease (PD) is a complex and chronic brain disorder characterized by motor and non-motor deficits. In common with other human chronic diseases, a small percentage of PD patients have inherited forms of the disease due to mutations in certain genes, but the vast majority is idiopathic. This review analyzes the different animal models organized according to the investigators endeavor to determine the role of a specific pathogenic mechanism that may be involved in the PD neurodegenerative process: genetics, environmental stress response (toxins, inflammation, and virus), protein aggregation, development and mitochondrial dysfunction. Finally, a conceptual framework of chronic brain degenerative disorders centered on PD is presented and future research directions are suggested.
Animal Models for Huntington's Disease
Authors: Ortega Zaira , Lucas José J.
Published: January 2023

Neurodegenerative diseases are very complex and their biological causes vary from one to another, but all of them have some characteristics in common: the progressive worsening of the symptoms and the degeneration of different components of the central nervous system that entails physical and mental disabilities. The generation of animal models to study these pathologies means a great advance in the knowledge of the metabolic pathways involved in the diseases, and helps to find out possible therapeutic targets. They are also the most physiological approach to perform global analysis of these diseases. Most of these animal models reproduce the pathogenesis by inserting or removing the mutation responsible for the disease from the animal genome. They can also be chemically generated when the cause of the disease is not genetic or known. The most used animals in laboratories are rodents but, lately, some laboratories are starting to use higher mammals to create new animal models to take advantage of the fact that their central nervous system is more similar to the human one, thus better resembling the human pathology.
Mouse Models of Ischemia
Authors: Henshall David C. , Simon Roger P.
Published: January 2023

Stroke is a leading cause of death and disability. Animal models of stroke have been developed as a means to characterize the pathophysiology of ischemia and evaluate therapeutic treatments to alleviate brain damage and the attendant neurologic deficits. Mice offer investigators a way to address specific gene effects including mutations, complete deletions and overexpression. A plethora of mouse models are available to the investigator including surgical occlusion of major cerebral arteries, intraluminal filament occlusion, thromboembolic, photothrombotic and stroke induced by pharmacologic vasoconstrictors. This chapter describes the origins of these models, technical aspects of procedures, and their strengths and weaknesses. We also highlight the utility of these models for investigating genetic and pharmacologic strategies to protect the brain. Last, we have a special focus on mouse models of ischemic tolerance, whereby brief, non-harmful ischemic episodes preceding a prolonged ischemic event reduce damage, and we highlight the emerging cell and molecular mediators thereof.
Autocrine Effects in White Adipose Tissue and Pancreatic Islets: Emergent Roles in the Regulation of Adipocyte and Pancreatic β-cell Function
Authors: Sugden Mary C. , Holness Mark J.
Published: January 2023

In this chapter, we develop the hypothesis that type 2 diabetes may in part reflect altered autocrine interactions in the adipocytes and the β cells of the pancreatic islets of Langerhans, together with an impaired adipo-insular axis whereby adipokines, as well as metabolic products of triglyceride mobilization released from adipose tissue, adversely impact β-cell function, with emphasis on the roles of fatty acids, derived from the breakdown of stored lipid, the adipokines leptin and adiponectin and the cytokine TNFα. In addition, we discuss the idea that an inappropriate early life environment may be an important player in the metabolic maladaptations leading to type 2 diabetes via augmented FA release in combination with altered secretion or action of adipo/cytokines.
Cell Signaling Mechanisms Underlying the Cardiac Actions of Adipokines
Authors: Karmazyn Morris , Rajapurohitam Venkatesh
Published: January 2023

The identification of the adipocyte as a source of production of biologically active peptides has materialized into an active area of research related to the role of these peptides in physiology and pathophysiology. Moreover, this research has resulted in the identification of the adipocyte as an endocrine organ producing potent bioactive compounds. An increasing number of these adipokines are being identified, the first of which was leptin, a product of the obesity gene whose primary function is to act as a satiety factor but which is now known to exert a myriad of effects. It is now recognized that virtually all adipokines produce effects on numerous organ systems including the heart. Indeed various adipokines including leptin, adiponectin and apelin exert potent and diverse cardiovascular effects, which are mediated by their specific receptors and involving complex and multi-faceted cell signaling pathways. Here we focus primarily on the diverse effects of adipokines on the heart and discuss the potential cell signaling mechanisms underlying their actions. Current evidence suggests that the cardiac effects of adipokines can be separated into beneficial and deleterious effects and therefore discussion is also presented on the emerging role of various adipokines in cardiac pathology with an examination of the possible underlying mechanisms which contribute to these effects. The review concentrates primarily on leptin and adiponectin, which are the most studied of the adipokines in terms of cardiac effects and which appear to function in a “yin-yang” type of relationship in exerting their cardiac effects. However, other adipokines including apelin, resistin and visfatin, which are emerging as potentially important in the regulation of cardiac function, are also introduced.
Involvement of Adipokines in Migraine Headache
Authors: Parker Keith K.
Published: January 2023

Even though the set of headaches known as migraine have been difficult to treat with either pharmacotherapy or other approaches, significant progress, particularly in acute episodes, has been made in recent decades. Regardless, much remains to be known about the genesis of migraine headaches, and their treatment, especially in the chronic, prophylactic sense. In this chapter, migraine is introduced in the context of various biochemical factors that have not been traditionally associated with headache. These include neural elements such as astrocytes and chemical parameters associated with metabolic, affective and sleep regulation. The primary focus is to suggest signaling pathways that might be tested for playing a role in the headaches and which could become targets for new drug development. Adipokines like leptin are noteworthy in this regard.
DNA, Nuclear Cell Signaling and Neurodegeneration
Authors: Adams, Jr., Ph.D. James D.
Published: January 2023

During aging, it is normal for neurodegeneration to occur, sometimes leading to Alzheimer's disease, Parkinson's disease and other conditions. Stroke can cause massive neurodegeneration. There is controversy concerning the causes of these conditions. Lifestyle will be examined as a possible cause of many neurodegenerative conditions in this chapter. It is possible that the blood-brain barrier is the initial site of damage that ultimately leads to inflammation in the brain that may produce some brain diseases. During stroke, thrombosis lodged in arteries leading to ischemia and reperfusion produces cell damage in many brain regions. This chapter will discuss mechanisms of adipokine and toxic lipid induced oxygen radical formation and damage to the blood-brain barrier. Active oxygen species such as hydrogen peroxide cross cell membranes, penetrate into the nucleus and very rapidly damage DNA. DNA peroxidation produces DNA fragments. DNA repair enzymes become activated and rapidly deplete cellular energy reserves, such as NAD and ATP. This drastically alters cell function and viability. Endothelial cell death makes the blood-brain barrier leak and may allow the infiltration of activated inflammatory cells that produce oxygen radicals that damage neurons and other brain cells. Neuronal death occurs through apoptosis and necrosis.
G Protein-Coupled Receptors: Conformational “Gatekeepers” of Transmembrane Signal Transduction and Diversification
Authors: Abrol Ravinder , Goddard III, FRSC William A.
Published: January 2023

Proteins in the cellular signaling machinery accomplish an amazing spectrum of functions necessary for the growth and survival of life by a network of signaling events separated in both space and time. Membrane proteins enable signal transduction across the cell membrane, which results in these signaling events inside the cell leading to a physiological response. G protein-coupled receptors (GPCRs) form the largest family of membrane proteins that process a very diverse set of extracellular signals and are capable of transducing multiple intracellular signaling pathways, mediated by G proteins and/or Arrestins, each with potentially different functional consequences. This “pleiotropic” nature of GPCRs is enabled by a high conformational flexibility of GPCRs, which allows for a unique ensemble of possible conformations depending on the state of the GPCR, whether it is in the apo form, or interacting with a ligand/antibody, or interacting with another protein. Each ligand can induce a different set of conformations in a GPCR, which can interact with G protein and Arrestin pathways in different ways, resulting in different physiological outcomes. This chapter provides an overview of how GPCRs use their conformational flexibility to perform a complex array of functions and how this can be used advantageously to bias signaling within the cell. A detailed understanding of the signaling pathways that are turned on by GPCRs, combined with the development of biased agonists and allosteric modulators to select specific outcomes, provides a promising avenue for developing therapeutics with minimal side-effects.
Enhancing the Capacity of DEM/CFD with an Immersed Boundary Method
Authors: Wu C.-Y. , Guo Y.
Published: January 2023

The coupled Discrete Element Method with Computational Fluid Dynamics (DEM/CFD) is a numerical technique for modelling fluid-solid particle flows, in which the motion of particles is modeled using DEM and that of fluid is solved using CFD. The interaction between the fluid and particles is approximated by an empirical correlation for the drag force. In this study, an immersed boundary method (IBM) is incorporated into DEM/CFD in order to model complex fluid-solid particle flows involving large objects and moving arbitrary shaped boundaries. The modified DEM/CFD is verified by comparing the numerical simulations with the experimental observation of the separation of binary mixtures in a vibrated bed. Its capacity is demonstrated with two case studies: i) fluidisation with a large immersed inclusion and ii) roll compaction in the presence of air. It is shown that the capacity of DEM/CFD is significantly enhanced with IBM and it can be used to simulate a range of particulate flows consisting of fluids and particles with large objects, complex and/or moving boundaries.
DEM Simulation of Migration Phenomena in Slow, Dense Slurry Flow with Brownian Motion Effects
Authors: Koenders M.A. , Ibrahim M. , Vahid S.
Published: January 2023

When a dense particle-fluid mixture is made to flow in a conduit experiments show that the particles tend to migrate to the centre where the magnitude of the shear rate is smallest. The effect vanishes when the particles are sufficiently small for thermal agitation by Brownian motion to dominate. A DEM procedure has been designed to simulate conduit flow using a lubrication interaction, modified to allow for rough particle surfaces. The Brownian motion is simulated by giving an extra force pulse at each time step. The magnitude distribution of these steps is determined by comparison with dilute media. The simulations at various Péclet numbers in two dimensions show encouraging similarity to reported experiments.
DEM Modelling of Subsidence of a Solid Particle in Granular Media
Authors: Goey C. H. , Pei C. , Wu C.-Y.
Published: January 2023

Granular media are materials possessing complex mechanical behaviour and can manifest themselves as solids or liquids, depending on their stress states. In this study, the subsidence of a solid particle (an intruder) in a granular medium was analysed using discrete element methods. 2D DEM simulations were performed to investigate the subsiding behaviour of an intruder with zero initial velocity (i.e., being placed onto the top surface of the granular bed) in a randomly generated granular bed. In addition, the effect of density ratio of the intruder to the particles in the granular bed on the subsiding behaviour of the intruder was explored. Furthermore, the effect of finite size of the granular bed (i.e. boundary constraints) on the subsiding behaviour of the granular bed was also examined. It has been found that the density ratio plays an important role in the subsidence of the intruder. When the density ratio is close to unity (i.e. the intruder and the particles in the bed have similar densities), the subsiding depth is almost zero, indicating that there is negligible subsidence. However, as the density ratio increases, the intruder subsides and penetrates through the granular bed, and the subsiding depth increases linearly with the density ratio. It was also observed that the finite size of the granular bed can affect the maximum subsiding depth, especially at the higher density ratios (say > 200) when a shallow bed was used.
Exploring the Controlling Parameters Affecting Specimens Generated in a Pluviator Using DEM
Authors: Cui L.
Published: January 2023

Engineering properties of specimens generated using a pluviator are of great interests for many researchers in geotechnical engineering, chemical engineering, pharmaceutical engineering, etc. In the present study, the sensitivity of the specimen properties to the controlling parameters were explored in a virtual pluviator using DEM. Inter-particle friction, damping coefficient, falling height, were varied systematically to investigate the resulting void ratio, coordination number, K0, and fabric anisotropy.

From this study, it can be found that the inter-particle friction plays a key role in the resultant specimen characteristics. Void ratio increases with increasing coefficient of inter-particle friction between 0.0 and 0.5, while remains unchanged with friction coefficient between 0.5 and 1.0. The void ratio increases remarkably with reducing damping at higher falling height. It also increases greatly with increasing falling height at low damping. The coordination number decreases at a reducing rate as friction coefficient increases from 0.0 to 1.0; however, it does not show significant sensitivity to falling height or damping coefficient. The “at-rest” stress ratio, k0 (σ'h/σ'v), reduces with increasing friction at very high damping or low falling height. The influence of friction coefficient on the fabric anisotropy is not very consistent. It can only find that fabric anisotropy is lower at higher damping coefficient at high falling height.
3D DEM Simulations of Undrained Triaxial Behaviour with Preshearing History
Authors: Gong G. , Chan A.H.C.
Published: January 2023

The paper presents results of three dimensional (3D) Discrete Element Method (DEM) simulations of undrained axisymmetric/triaxial tests on loose assemblies of polydisperse spheres with and without preshearing history using a periodic cell. Undrained tests were modelled by deforming the samples under constant volume conditions. The simulations show that the preshearing process will not induce initial structural anisotropy, and that the presheared and unpresheared samples follow the same initial stress path along a limiting boundary in q-p space as observed in published laboratory experimental results, which was not crossed over by any of stress paths of the presheared samples. It is also shown that the presheared samples are denser compared with the original unpresheared one, and therefore exhibit higher resistance to (temporary) liquefaction. At the grain scale, such higher resistance is found to be attributed to the evolution of redundancy index, a microscopic definition of liquefaction (temporary liquefaction) proposed in another paper. The Lade instability (peak deviator stress) is found to correspond to a unique mechanical coordination number of 4.5, independent of preshearing history. It is also found that the onset of liquefaction (temporary liquefaction) in terms of redundancy index lags behind the onset of the macroscopic strain softening in terms of the Lade instability for the presheared and unpresheared samples under undrained conditions.
Strong Force Network of Granular Mixtures Under One-dimensional Compression
Authors: Minh N.H. , Cheng Y.P.
Published: January 2023

We studied one dimensional compressive behaviour of gap-graded granular mixtures, using the numerical simulations of the three-dimensional Discrete Element Method (DEM). Spherical particles of different size ranges were generated inside a cubical box to numerically create granular samples with the particle size distributions of a sand-like material mixed with different proportions of a uniform silt-size material. The DEM samples were subjected to one-dimensional compression similar to the loading path of the oedometer test in soil mechanics. Micromechanical characteristics behind the compressibility of granular mixtures were investigated with an emphasis on the strong force network. Unlike monodisperse assemblies, the deviatoric stress is mainly attributed to contact forces with a magnitude greater than the mean contact force of the system, the deviatoric stress of these mixture materials is attributed to a combination of the different contact types between different particle sizes. There is a primary shear-strength related load-bearing contact network, and this depends on the relative proportion of the silt particles in the system. For systems with a very little amount of silt, mainly consisting of sand particles, the main contribution to deviatoric stress is due to the contacts between the sand particles. On the other hand, for systems that have the void space between sand particles efficiently occupied by silt particles, all contact types contribute to the deviatoric stress. If strong forces of a particulate system are those responsible for the deviatoric stress, the characteristic force - that separates strong and weak forces - depends on the contact-type, the particle size distribution and the stress level; the value of the overall characteristic force however is not far from the mean force value of the system.
Verification of the Double Slip and Rotation Rate Model for Elliptical Granular Flow Using the Distinct Element Method
Authors: Li L.Q. , Jiang M.J. , Shen Z.F.
Published: January 2023

The investigation in this paper focuses on the numerical verification of the double slip and rotation rate model (DSR2 model) for elliptical particles by the discrete element method (DEM). The averaged micro-pure rotation rate (APR) based on the relative movement of contact between two ellipses has been firstly deduced, then the variable was introduced into the DSR2 model, which is originally proposed for plastic flow of granular assemblages. A developed DEM code NS2D was used to generate assemblages that were composed of elliptical particles with aspect ratio of 1.4 and 1.7, respectively. Then undrained simple shear tests on these samples were conducted to reproduce the plastic flow of elliptical particles and validate the DSR2 model. The results show that the DSR2 model appears to be able to predict the variation of angular velocity in kinematic models of both circular and elliptical particle assemblies, and the variable APR is a rational and important parameter, which considers the effect of particle rotation in the energy dissipation process and bridges discrete and continuum granular mechanics.
Mechanical Behaviour of Methane Hydrate Soil Sediments Using Discrete Element Method: Pore-filling Hydrate Distribution
Authors: Yu Y. , Cheng Y. P. , Soga K.
Published: January 2023

Methane hydrate bearing soil is usually found under deep seabed and permafrost regions. It attracts research interest as a possible energy resource, but it also has potential impacts on climate change and geotechnical issues during methane gas production. Due to the limitations of laboratory studies, in this research, Discrete Element Method (DEM) simulations were performed to provide unique insights into the mechanical behaviour of hydrate-bearing sediments with pore-filling hydrate distribution. A series of drained triaxial shearing tests were systematically conducted to study the effects of hydrate saturation on the hydrate-bearing samples. It is shown that the peak shear strength increased and dilation was enhanced as hydrate saturation increased, especially when the hydrate saturation was above 20%. However, the critical state shear strength reduced slightly when hydrate saturation increased from 20%, with the dilation being reduced to zero in the critical state. The hardening effect of hydrate at the peak strength and the softening behaviour of samples in the critical state also reflected the peak and critical state friction angles. The strength of samples was enhanced with increasing confining pressure. It is found that for pore-filling hydrate distribution, the hydrate contribution to the strength of the sediments is of a frictional nature.
On the Effect of Soil Modification with Lime Using Grading Entropy
Authors: Imre E. , Szendefy J. , Lőrincz J. , Trang P.Q. , Singh Vijay P.
Published: January 2023

Agglomeration may take place in the presence of a cementing agent like lime. If the failure of an agglomerated body is caused by the failure of bonds then the processes are symmetric. This study shows that the effect of lime modification on the grading curve evolution in the non-normalised grading entropy diagram is basically opposite to the effect of the usual particle breakage. Both can be related to the “entropy principle” through the grading entropy concept. In the normalised grading entropy diagram the grading curve evolution path is the same except that discontinuity occurs upon the change in the fraction number. The entropy coordinate A can be used as a stability measure (i.e. in the sense that the stability increasing with A). The discontinuous change in A results in a more stable structure for breakage and less stable structure if lime is added to a small plasticity soils. In case of very high clay content the discontinuity at lime modification was stabilized.
Platinum Group Metals
Authors: Mudd Gavin M.
Published: January 2023

This chapter reviews the platinum group metals, focusing particularly on current economic resources and production trends. Most of the world's platinum group metals (PGMs) are found in South Africa, with moderate amounts in Russia and Zimbabwe and minor amounts in Canada and other countries. Based on a detailed compilation of reported resources for 2010, there are about 90 400t of PGMs globally, compared with current annual production of about 465t. It is clear that there are abundant amounts of PGMs to meet growing global demands for some decades. The primary constraints which are already proving challenging for the PGMs sector are environmental and social in nature – such as economic benefits sharing, energy and emissions intensity, water consumption and impacts on water resources. Overall, PGMs can certainly provide a range of metals for sustainable materials and technologies into the future, but they will come at increasing environmental and social costs which need to be carefully assessed and managed to ensure the most sustainable outcomes for the countries involved and also global issues such as greenhouse gas emissions and climate change risks.
Aquatic Biomass for the Production of Fuels and Chemicals
Authors: Dibenedetto Angela , Colucci Antonella
Published: January 2023

This chapter highlights the potential of aquatic biomass as a source of chemicals and fuels. Aquatic biomass can be considered an interesting alternative to fossil fuels because with respect to terrestrial or residual biomass it has a higher solar energy utilisation efficiency (6–8% versus 1.5–2.2%).

Aquatic biomass, i.e. micro-algae, macro-algae and plants, has a chemical composition that depends on the species and on the light, temperature, nutrients and salinity, and also biotic interactions, so it is better to use a selected cultivated strain in order to have an optimal energetic yield. In particular, the co-production of chemicals and fuels can be of great importance in order to make more positive the economic balance of growing algae for commercial purposes. Compounds of particular commercial interest include pigments, lipids and fatty acids, proteins, polysaccharides and phenolics, all of which display considerable diversity between and within taxa.
Methane for Transportation Fuel and Chemical Production
Authors: de Klerk Arno , Prasad Vinay
Published: January 2023

Methane is the main component of natural gas. Natural gas is an important energy carrier for distributed heating and transportation applications and it is the most efficient carbon source for the production of synthesis gas (H2+CO). The value of natural gas lies in its high H:C ratio, low heteroatom content and fluid nature. Sustainability is best served by restricting the use of methane for distributed and mobile energy applications, where the clean-up of combustion gases is impractical or infeasible, and also for the synthesis of hydrogen-rich products. For the production of fuels and chemicals, both direct methods, such as liquefied natural gas, and indirect methods, such as methanol and Fischer–Tropsch synthesis, are considered. Guidelines for sustainability as applied to gas-to-liquids conversion are provided. The processes and the refining requirements to produce on-specification transportation fuels are discussed. The processes for petrochemical and lubricant production from methane are likewise discussed.
Sustainable Materials in Building and Architecture
Authors: Van Wyk, Llewellyn , Mapiravana Joe , Ampofo-Anti Naa Lamkai
Published: January 2023

Construction remains one of the most intensive material consumers. The primary factors driving future material growth include increased investment in the residential and commercial sectors, increased spending by governments in infrastructure, improving liquidity in the financial markets, a softening of interest rates and ongoing industrialisation in developing economies. The building material manufacturing and supply sector is in a state of transformation, driven in large part by regulations requiring environmentally friendly or ‘green’ materials. The push for green products has spurred interest in bio-based materials, recycled materials, and the inclusion of waste materials. In addition, green building has raised performance requirements for buildings resulting in analysts forecasting a double-digit growth in green materials every year to 2013. From an environmental perspective, ‘green’ materials would be those materials with the least ‘embodied effects', where the word embodied refers to attribution or allocation in an accounting sense as opposed to true physical embodiment, and includes energy, water and toxicity. A five-pillared strategy, based on optimising existing environmentally sound technologies and the research and development of new environmentally sound technologies, is proposed, namely optimise conventional technologies and mainstream fringe technologies, accelerate hybrid technology uptake, develop biotechnology applications and develop nanotechnology applications. It is highly unlikely, however, that there will be a reduction in or a major shift away from conventional bulk materials in the short to medium term. Some new trends will emerge, however, most likely in insulation materials, in a shift away from ceramic products, in a shift away from zinc and copper use in piping towards PVC and other plastics, in a shift towards biocomposite materials in and an uptake of recycled materials most notably in concrete (aggregate substitution), steel and aluminium. It is critical that the construction industry in general, and construction material manufacturers in particular, identify first, the environmental bottlenecks related to current and future material production and consumption, and second, the technological opportunities to mitigate those environmental problems. The construction industry needs to concentrate on those environmental impacts of materials that are caused during material production (extraction, energy and water use) and end-of-life management (waste management and recycling). In some cases, the in-use phase may dominate the overall environmental impacts of product life cycles because of a continuous supply of energy and/or materials during use, e.g. buildings (operation, maintenance, repair).
Enhancing the Capacity of Molecular Dynamics Simulations with Trajectory Fragments
Authors: Cardenas Alfredo E. , Elber Ron
Published: January 2023

We examine theoretical and computational approaches that use fragments of Molecular Dynamic trajectories to compute kinetic and thermodynamic properties of complex systems. The trajectory fragments replace a single long trajectory that is widely used for these problems. We discuss the theories, approximations, and computational implementations, and why trajectory fragments lead to more efficient calculations. We further provide a numerical example (a transition in the Mueller potential) for the methods of Milestoning and Forward Flux, which exploit trajectory fragments differently. Advantages and disadvantages of the different approaches that use fragments and of the single trajectory calculations are discussed.
Chemistry and Pollution of the Marine Environment
Authors: Preston Martin R.
Published: January 2023

Human activities continue to place great strains on the marine environment through the deliberate or accidental release of hazardous materials. Recent events, notably the 2010 subsea oil spill at the Macondo well in the Gulf of Mexico, have been the receipt of major international attention. However many other, more insidious, forms of marine contamination are much less widely recognised. This chapter makes some basic observations about the nature of marine systems and then reviews nature and occurrence of the major marine contaminants together with their principal effects. Topics discussed include oil, persistent organic chemicals, sewage and nutrients, metals and radioactive materials with the intention of reflecting the current state of knowledge and identifying future threats.
Drinking Water Quality and Health
Authors: Fawell John K.
Published: January 2023

Safe drinking water is essential for living and for an acceptable level of health. In this chapter, the guidelines and standards are discussed for both microbial and chemical contaminants which have been developed in order to assure safe drinking water,. As new sources of water and new contaminants emerge, new approaches will be required. This process has been started by WHO with their framework for safe drinking water and water safety plans in the third and fourth editions of Guidelines for Drinking-water Quality. The framework is supported by the numerical guidelines and standards that provide a benchmark for managing drinking water sources and supplies.
Water Pollution Biology
Authors: Mayes William M.
Published: January 2023

Freshwater systems are disproportionately diverse, yet they are experiencing extinction rates several times higher than terrestrial systems. Water pollution is a key pressure on our freshwaters and biological monitoring plays a crucial role in identifying, understanding and managing these impacts. This chapter reviews the sources and effects of a range of common pollutants on aquatic organisms such as organics, nutrient enrichment, acidification, as well as the threats posed by some of the important emerging contaminants (e.g. engineered nanoparticles and personal health care products). The chapter concludes with a review of the increasingly important role of biological monitoring in routine environmental assessments of freshwaters, both in the laboratory and in the field. From laboratory toxicity tests and new molecular tools providing early warning systems for pollutant impacts, to the integrated monitoring of freshwater systems at a catchment scale, we consider how biological assessments are being used for improving and safeguarding the ecological status of our lakes and rivers.
Chemistry of the Troposphere
Authors: Harrison Roy M.
Published: January 2023

The concept of pollutant cycling in the atmosphere is introduced in this chapter and the basic determinants of atmospheric lifetime and concentration variability described. The hydroxyl radical is central to atmospheric chemistry and its formation pathways are discussed leading into a description of the formation chemistry and behaviour of tropospheric ozone. A subsequent description of other atmospheric oxidants (peroxyacetylnitrate and oxides of nitrogen) is followed by a consideration of the sources and sinks of atmospheric acids and bases. Amongst the most important constituents in the atmosphere in relation to human health and climate regulation are atmospheric aerosols whose typical composition and formation pathways are outlined. Finally, the inter-relationships between pollutants, environmental effects and impacts in relation to climate, eco-systems and human health are presented.