bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orthodontics
Authors: Longridge Nicholas , Clarke Pete , Aftab Raheel , Ali Tariq 
Published: November 2020

Abstract
Orthodontics is ‘the specialty of dentistry concerned with growth of the face, the development of dentition, and the prevention and correction of occlusal anomalies. A malocclusion can be defined as ‘a deviation from the ideal that may be aesthetically or functionally unsatisfactory, with a wide range of occlusal traits’. Orthodontics is a constantly evolving specialty, with ever changing principles and techniques continuing to be developed. There has been huge progress in orthodontics in recent times, with changes in the types of brackets, archwire materials, and appliance systems (such as tem­porary anchorage devices and aligner technology). The key principles of orthodontics date back to 1899 when Edward Angle described ‘the key to a normal occlusion as the anteropos­terior relationship between the upper and lower first molars’. In 1972, Lawrence Andrews described ‘six keys to an ideal static occlusion’. This was the basis of early orthodontic treatment planning. Knowledge of craniofacial development and growth is required as a foundation for understanding the aetiology of a patient’s malocclusion, to reach a diagnosis, and to plan orthodontic treatment. A basic under­standing of the types of orthodontic appliances is beneficial (mainly fixed appliances, functional appliances, some use of removable appliances, and retainers). In addition to the management of a malocclusion, orthodontic treat­ment is often required in conjunction with other specialties, including oral and maxillofacial surgery, paediatric and restorative dentistry Key topics discussed in this chapter include: ● Fixed appliances ● Functional appliances ● Removable appliances ● Retention ● Index of treatment need ● Orthodontic assessment and diagnosis ● Cephalometric analysis ● Malocclusion ● Ectopic canines ● Dental anomalies.
Endodontics
Authors: Longridge Nicholas , Clarke Pete , Aftab Raheel , Ali Tariq 
Published: November 2020

Abstract
Endodontics remains a rapidly advancing branch of restorative dentistry. It is highly likely that, by the time this book is published, several new or updated endodontic file systems will have been released. Despite the fairly rapid technological advances that the profession has seen, the key principles of endodontic treatment remain the same: 1. Eliminate microorganisms from the root canal system 2. Prevent reinfection of the root canal system 3. Retain a functional natural tooth. Whilst these principles are easy to discuss, they are consistently diffi­cult to perform, due, in large part, to the complexity of the root canal system. Multiple theories, principles, and approaches have been discussed to help achieve an optimal technical and clinical outcome. However, evi­dence to favour one specific stage or system over another is lacking, and as such, a large degree of operator preference and experience will ultimately influence the treatment planning and technical strategy. Much like baking a cake, endodontic treatment relies upon a series of proced­ural steps to achieve a desirable outcome, which, for the patient, often equates to a functional, pain-free natural tooth. Good- quality magnification remains a key component of an endodontist’s armamentarium, and dental loupes or a dental operating microscope could not be recommended more highly. Key topics include: ● Endodontic case assessment, including root canal anatomy ● Pain management, including local anaesthesia ● Access and canal identification ● Vital pulp therapy, including caries management ● Canal negotiation and instrumentation ● Root canal irrigation ● Root canal obturation ● Restoration of the endodontically treated tooth.
Prosthodontics
Authors: Longridge Nicholas , Clarke Pete , Aftab Raheel , Ali Tariq 
Published: November 2020

Abstract
Prosthodontics comprises most of the routine restorative treatments that practitioners perform on a daily basis. Much restorative work re¬sults from the impact of caries and periodontal disease. However, the prevalence of toothwear is dramatically increasing and can be expected to form a more prominent feature of the modern practitioner’s work¬load. There is a considerable theory base in prosthodontics, covering all aspects of fixed and removable treatments, both conventional and contemporary. Although the individual management of teeth can be tricky, a challenge many new practitioners struggle with is treatment planning on a patient level. Treatment planning is rarely black and white, with considerable variations in opinion among clinicians, even for more simple cases. The staging of treatment planning is fairly consistent across the profession (e.g. relief of pain first, then investigatory phase, etc.), but in complex cases, a second opinion may be warranted. Not only is treatment plan¬ning a difficult skill, but so is the execution. It takes practice to become adept at the variety of clinical skills in prosthodontics and the staging of treatment, but this makes for a rewarding and fascinating discipline. Modern dentistry has a much greater focus on minimal invasive treat-ment, relying on dentine bonding and adhesive dentistry to limit the need for aggressive preparations of teeth and protect the vitality of the pulp. Moreover, the progression in digital dentistry is exponential, with newer production methods and clinical techniques becoming increasingly accurate and ever more accessible. As such, the modern practitioner needs to have a good understanding of both conventional concepts and modern alternatives in order to be able to apply the material and tech¬nique of choice to achieve an optimal outcome. The questions in the chapter aim to cover a wide range of topics, testing conventional concepts in both fixed and removable prostho¬dontics, whilst touching on contemporary materials and production methods. It is hoped that the reader will be challenged and the more difficult questions will promote wider reading. Key topics include: ● Diagnosis and treatment planning ● Occlusion ● Toothwear ● Complete dentures ● Removable dentures (including denture design principles) ● Direct restorations ● Crown and bridge ● Implant restorations ● Laboratory processes ● Digital dentistry.
Chemoselective and orthogonal ligation techniques
Authors: Tam James P , Lu Y -A 
Published: November 2020

Abstract
Peptide synthesis through segment ligation of unprotected peptides (total synthesis) and peptides to proteins (semi-synthesis) in aqueous solution is appealingly simple and efficient because protection and activation steps are not required. In addition, this method offers the potential to access a diverse group of macromolecules such as circular proteins, branched peptides, and protein conjugates which are difficult to obtain through conventional approaches using protecting group strategies. Furthermore, the use of unprotected peptide segments overcomes the problem of solubility encountered in the conventional approach to the synthesis of large peptides or proteins in solution. Conceptually, ligation can be approached two ways. In the first approach, a non-amide bond is formed between two peptide segments through a pair of mutually reactive functional groups. Typical methods of non-amide ligation include oxime, hydrazone, and thiazolidine as the coupling linkages. This type of reaction is traditionally referred to as chemoselective ligation. Non-amide ligation is characteristically flexible in joining two segments that result in amino-to-amino end, carboxyl-to-amine or end-to- side chain structures. This flexibility permits synthesis of protein mimetics and branched peptide dendrimers. In the second approach, an amide bond is formed through a two-step reaction sequence involving four functional moieties, two nucleophiles and two electrophiles in the reaction centre. This reaction is usually used for end-to-end coupling between the Cα-moiety of one peptide segment and the Nα-terminus of another peptide segment resulting in a peptide-backbone product. Similar to the non-amide chemoselective ligation, the first step in orthogonal ligation is a capture reaction by a pair of mutually reactive groups. In general, two nucleophiles, a weak-base nucleophile on the side chain and an α-amino, are located at the N-terminus as an N-terminal nucleophile 5 (NTN). The two electrophiles, usually an O-glycol-aldehyde or an S-ester 4, are located at the C-terminus of the another peptide segment. The initial non-amide capture of two segments through the side chain NTN with the O- or S-ester to form a covalent intermediate 6 enables the spontaneous proximity-driven intramolecular acyl transfer to occur. This intramolecular acyl migration achieves orthogonality in amide bond formation 7 between a specific α-amine in the presence of other free α- and ɛ-amines.
Purification of large peptides using chemoselective tags
Authors: Mascagni Paolo 
Published: November 2020

Abstract
In solid phase peptide synthesis (SPPS), deletion sequences are generated at each addition of amino acid due to non-quantitative coupling reactions. Their concentration increases exponentially with the length of the peptide chain, and after many cycles not only do they represent a large proportion of the crude preparation, but they can also exhibit physicochemical characteristics similar to the target sequence. Thus, these deletion-sequence contaminants present major problems for removal, or even detection. In general, purification of synthetic peptides by conventional chromatography is based on hydrophobicity differences (using RP-HPLC) and charge differences (using ion-exchange chromatography). For short sequences, the use of one or both techniques is in general sufficient to obtain a product with high purity. However, on increasing the number of amino acid residues, the peptide secondary and progressively tertiary and quaternary structures begin to play an important role and the conformation of the largest peptides can decisively affect their retention behaviour. Furthermore, very closely related impurities such as deletion sequences lacking one or few residues can be chromatographically indistinguishable from the target sequence. Therefore, purification of large synthetic peptides is a complex and time-consuming task that requires the use of several separation techniques with the inevitable dramatic reduction in yields of the final material. Permanent termination (capping) of unreacted chains using a large excess of an acylating agent after each coupling step prevents the formation of deletion sequences and generates N-truncated peptides. However, even under these more favourable conditions, separation of the target sequence from chromatographically similar N-capped polypeptides requires extensive purification. If the target sequence could be specifically and transiently labelled so that the resulting product were selectively recognized by a specific stationary phase, then separation from impurities should be facilitated. This chapter deals with such an approach and in particular with the purification of large polypeptides, assembled by solid phase strategy, using lipophilic and biotin-based 9-fluorenylmethoxycarbonyl (Fmoc) chromatographic probes. Assuming that the formation of deletion sequences is prevented by capping unreacted chains, a reciprocal strategy can be applied that involves functional protection of all polymer-supported peptide chains that are still growing, with a specially chosen affinity reagent or chromatographic probe.
Give and Take: Neutralization
Authors: Atkins Peter 
Published: November 2020

Abstract
The almost infinite can spring from the almost infinitesimal. Two almost infinitesimally small fundamental particles are of considerable interest to chemists: the proton and the electron. As to the almost infinite that springs from them, almost the whole of the processes that constitute what we call ‘life’ can be traced to the transfer of one or other of these particles from one molecule to another in a giant network of reactions going on inside our cells. I think it quite remarkable, and rather wonderful, that a hugely complex network of extremely simple processes in which protons and electrons hop from one molecule to another, sometimes dragging groups of atoms with them, sometimes not, results in our formation, our growth, and all our activities. Even thinking about proton and electron transfer, as you are now, involves them. Here I consider the transfer of a proton in some straightforward reactions in preparation for seeing later, in the second part of the book, how the same processes result in eating, growing, reproducing, and thinking. For reactions that involve the transfer of electrons, see Reaction 5. What is a proton? For physicists, a proton is a minute, positively charged, very stable cluster of three quarks; they denote it p. For chemists, who are less concerned with ultimate things, a proton is the nucleus of a hydrogen atom; they commonly denote it H+ to signify that it is a hydrogen atom stripped of its one electron, a hydrogen ion. I shall flit between referring to this fundamental particle as a proton or a hydrogen ion as the fancy takes me: they are synonyms and the choice of name depends on convention and context. An atom is extraordinarily small, but a proton is about 100 000 times smaller than an atom. If you were to think of an atom as being the size of a football stadium, then a proton would be the size of a fly at its centre. It is nearly 2000 times as heavy as an electron. Nevertheless, a proton is still light and nimble enough to be able to slip reasonably easily out from its home at the centre of a hydrogen atom in some types of hydrogen-containing molecules.
Changing Partners: Complex Substitution
Authors: Atkins Peter 
Published: November 2020

Abstract
I shall now describe a special case of the Lewis acid–base reactions I introduced in Reaction 9. I showed there that a Lewis acid is a species that can accept a lone pair from another incoming species and form a bond to it, that a Lewis base is a species that provides that lone pair, and that the result of this sharing is a complex of the two species joined together by a chemical bond. The important special case I would like to share with you here is when the Lewis acid is a metal atom or ion, especially but not necessarily one drawn from the d-block of the periodic table (a ‘transition metal’). The d-block consists of the elements that make up the skinny central rectangle of the periodic table. They include important constructional metals, such as iron, nickel, and copper, and also the chemically aloof ‘noble’ metals gold, platinum, and silver. The Lewis base that I focus on will be a molecule or ion that also has an independent existence in the wild, such as water, H2O, or ammonia, NH3. In most cases the complex consists of the central metal atom or ion with up to six Lewis bases clustering around it. In this context, the Lewis bases are known as ‘ligands’ (from the Latin for ‘bound’) and I shall use that term here. I don’t want you to think that I am embarking on stratospherically esoteric material again. These metal complexes are hugely important in many aspects of the everyday world. For instance, chlorophyll is a complex of magnesium and is responsible for capturing the energy of the Sun for photosynthesis (Reaction 26). There is hardly a more important molecule. One that comes close in importance is haemoglobin, an elaborate complex of iron, which ensures that oxygen reaches all your cells and keeps you alive. Many pigments are complexes, so your life is decorated and made more colourful by them. Some pharmaceuticals are complexes based on platinum, so one day, perhaps even now, you might be kept alive by one of these artificial complexes.
Electronic Warfare: Electrophilic Substitution
Authors: Atkins Peter 
Published: November 2020

Abstract
Benzene, 1, is a hard nut to crack. The hexagonal ring of carbon atoms each with one hydrogen atom attached has a much greater stability than its electronic structure, with an alternation of double and single carbon–carbon bonds, might suggest. But for reasons fully understood by chemists, that very alternation, corresponding to a continuous stabilizing cloud of electrons all around the ring, endows the hexagon with great stability and the ring persists unchanged through many reactions. The groups of atoms attached to the ring, though, may come and go, and the reaction type responsible for replacing them is commonly ‘electrophilic substitution’. Whereas the missiles of Reaction 15 sniff out nuclei by responding to their positive electric charge shining through depleted regions of electron clouds, electrophiles, electron lovers, are missiles that do the opposite. They sniff out the denser regions of electron clouds by responding to their negative charge. Let’s suppose you want to make, for purposes you are perhaps unwilling to reveal, some TNT; the initials denote trinitrotoluene. You could start with the common material toluene, which is a benzene ring with a methyl group (–CH3) in place of one H atom, 2. Your task is to replace three of the remaining ring H atoms with nitro groups, –NO2, to achieve 3. And not just any of the H atoms: you need the molecule to have a symmetrical array of these groups because other arrangements are less stable and therefore dangerous. It is known that a mixture of concentrated nitric and sulfuric acids contains the species called the ‘nitronium ion’, NO2+, 4, and this is the reagent you will use. Before we watch the reaction itself, it is instructive to see what happens when concentrated sulfuric acid and nitric acid are mixed. If we stand, suitably protected, in the mixture, we see a sulfuric acid molecule, H2SO4, thrust a proton onto a neighbouring nitric acid molecule, HNO3. (Funnily enough, according to the discussion in Reaction 2, nitric ‘acid’ is now acting as a base, a proton acceptor! I warned you of strange fish in deep waters.) The initial outcome of this transfer is unstable; it spits out an H2O molecule which wanders off into the crowd. We see the result: the formation of a nitronium ion, the agent of nitration and the species that carries out the reaction for you.
Dark Matter: Photochromism
Authors: Atkins Peter 
Published: November 2020

Abstract
Let’s start with the ‘ionization’ of an atom, the formation of an ion by the ejection of an electron when the atom is struck by a sufficiently energetic photon. This kind of process is the basis of the operation of early versions of photochromic glasses, which darken when exposed to bright sunlight, specifically in response to the high-energy ultraviolet component of sunlight that is present outdoors. That kind of photochromic glass was made by adding silver and copper nitrates to molten glass. As the glass cools, small crystallites of the salts form. The crystallites are too small to scatter or absorb visible light, so the glass appears transparent. Now we step into the solid glass and watch what happens when we step outside and ultraviolet photons rain down on us. We see a photon plunge into the glass and strike a copper ion, Cu+. The photon has enough energy to expel an electron from the ion, so forming Cu2+. We see the ejected electron wander off through the solid. Almost immediately, however, it is captured by a silver ion, Ag+, converting it to a silver atom, Ag. (Recall that Ag is the chemical symbol for silver, from the Latin argentum.) Sunlight has induced a redox reaction, an electron transfer reaction (Reaction 5). Now, as we continue to watch, several Ag atoms cluster together to give a microscopic dot of silver metal. These little clusters act like tiny shutters to block some of the light passing through the glass, and the image is dimmed. The clusters of atoms survive for a short time, but inevitably break up and release the additional electron back into the solid. It finds its way back to the strongly attracting double positive charge of a Cu2+ ion and attaches to it, so recreating the original Cu+ ion. However, if you stay outside in the sunlight, ionization and Ag atom formation continue, and your glasses stay dimmed. Only when you come back indoors and the ultraviolet radiation no longer reaches you do the ionization processes cease, and the glass reverts to being fully transparent.
Green Chemistry: Photosynthesis
Authors: Atkins Peter 
Published: November 2020

Abstract
Each square metre of the Earth receives up to 1 kW of solar radiation, with the exact intensity depending on latitude, season, time of day, and weather. A significant amount of this energy is harnessed by the almost magical process we know as ‘photosynthesis’ in which water and carbon dioxide are combined to form carbohydrates. Thus, from the air and driven by sunlight, vegetation plucks vegetation. That new vegetation is at the start of the food chain, for its metabolism is used to forge protein and, in our brains, drive imagination. There is probably no more important chemical reaction on Earth. A large proportion of solar radiation is absorbed by the atmosphere. Ozone and oxygen molecules absorb a lot of ultraviolet radiation, and carbon dioxide and water molecules absorb some of the infrared radiation. As a result, plants, algae, and some species of bacteria have to make do with what gets through and evolved apparatus that captures principally visible radiation. The early forms of these organisms stumbled into a way to use the energy of visible radiation, which arrives in the packets we call photons, to extract hydrogen atoms from water molecules and use them and carbon dioxide to build carbohydrate molecules, which include sugars, cellulose, and starch. The oxygen left over from splitting up water for its hydrogen went to waste. Most of the oxygen currently in the atmosphere has been generated and is maintained by photosynthesis since Nature first stumbled on the process about 2 billion years ago and thereby caused the first great pollution. That pollution, in Nature’s characteristically careless and wholly thoughtless and unplanned way, was to turn out to be to our great advantage. Photosynthesis begins in the organelle (a component of a cell) known as a ‘chloroplast’, so you need to poke around inside one if you are to understand what is going on. I shall focus on the light harvesting and the accompanying ‘light reactions’. What follows them, the so called ‘dark reactions’ in which the captured energy is put to use to string CO2 molecules together into carbohydrates, is controlled in a highly complex way by enzymes.