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Fully revised and updated, the new edition of this classic textbook places a stronger emphasis on real-world test data and trains students in practical materials applications; introduces new testing techniques such as micropillar compression and electron back scatted diffraction; and presents new coverage of biomaterials, electronic materials, and cellular materials alongside established coverage of metals, polymers, ceramics and composites. Retaining its distinctive emphasis on a balanced mechanics-materials approach, it presents fundamental mechanisms operating at micro- and nanometer scales across a wide range of materials, in a way that is mathematically simple and requires no extensive knowledge of materials, and demonstrates how these microstructures determine the mechanical properties of materials. Accompanied by online resources for instructors, and including over 40 new figures, over 100 worked examples, and over 740 exercises, including over 280 new exercises, this remains the ideal introduction for senior undergraduate and graduate students in materials science and engineering.
Two fruit fly (Diptera: Tephritidae) species of economic importance: Ceratitis rosa Karsch and Ceratitis quilicii De Meyer, Mwatawala & Virgilio are present in South Africa. The two species were considered as one species prior to 2016, but were subsequently separated. In this study, the distribution and abundance of the two species were quantified in seven provinces in South Africa through trapping with Enriched Ginger Oil as an attractant. Trapping was conducted over three seasons across two years (2020 and 2021): late summer, autumn-winter, and spring-early summer. Host ranges of the two species were investigated by fruit sampling in and outside of trapping sites. Ceratitis quilicii was more widely distributed than C. rosa with the latter being recorded in only three north-eastern provinces. There were geographical limits for both species with no records of them in Northern Cape Province. Catches of C. quilicii were higher in summer with average temperatures varying from 15 to 27°C while for C. rosa, catches remained low and consistent between seasons. Ceratitis quilicii catches decreased at lower rates than those of C. rosa at temperatures below 15°C. The two species were reared from 13 plant species from nine families. Four of these hosts were infested by both C. quilicii and C. rosa in the same province where they occurred. Preferred hosts of the two species belonged to the Myrtaceae family. The characterisation of the distribution, abundance and host ranges of these pests will provide a baseline for pest status determination and implementation of management actions.
Subglacial lake water-volume changes produce ice-elevation anomalies that provide clues about water flow beneath glaciers and ice sheets. Significant challenges remain in the quantitative interpretation of these elevation-change anomalies because the surface expression of subglacial lake activity depends on basal conditions, rate of water-volume change, and ice rheology. To address these challenges, we introduce an inverse method that reconstructs subglacial lake activity from altimetry data while accounting for the effects of viscous ice flow. We use a linearized approximation of a Stokes ice-flow model under the assumption that subglacial lake activity only induces small perturbations relative to a reference ice-flow state. We validate this assumption by accurately reconstructing lake activity from synthetic data that are produced with a fully nonlinear model. We then apply the method to estimate the water-volume changes of several active subglacial lakes in Antarctica by inverting data from NASA's Ice, Cloud, and land Elevation Satellite 2 (ICESat-2) laser altimetry mission. The results show that there can be substantial discrepancies (20% or more) between the inversion and traditional estimation methods due to the effects of viscous ice flow. The inverse method will help refine estimates of subglacial water transport and further constrain the role of subglacial hydrology in ice-sheet evolution.
Alcohol use is influenced by genetic and environmental factors. We examined the interactive effects between genome-wide polygenic risk scores for alcohol use (alc-PRS) and social support in relation to alcohol use among European American (EA) and African American (AA) adults across sex and developmental stages (emerging adulthood, young adulthood, and middle adulthood). Data were drawn from 4,011 EA and 1,274 AA adults from the Collaborative Study on the Genetics of Alcoholism who were between ages 18–65 and had ever used alcohol. Participants completed the Semi-Structured Assessment for the Genetics of Alcoholism and provided saliva or blood samples for genotyping. Results indicated that social support from friends, but not family, moderated the association between alc-PRS and alcohol use among EAs and AAs (only in middle adulthood for AAs); alc-PRS was associated with higher levels of alcohol use when friend support was low, but not when friend support was high. Associations were similar across sex but differed across developmental stages. Findings support the important role of social support from friends in buffering genetic risk for alcohol use among EA and AA adults and highlight the need to consider developmental changes in the role of social support in relation to alcohol use.
Researchers have identified genetic and neural risk factors for externalizing behaviors. However, it has not yet been determined if genetic liability is conferred in part through associations with more proximal neurophysiological risk markers.
Methods
Participants from the Collaborative Study on the Genetics of Alcoholism, a large, family-based study of alcohol use disorders were genotyped and polygenic scores for externalizing (EXT PGS) were calculated. Associations with target P3 amplitude from a visual oddball task (P3) and broad endorsement of externalizing behaviors (indexed via self-report of alcohol and cannabis use, and antisocial behavior) were assessed in participants of European (EA; N = 2851) and African ancestry (AA; N = 1402). Analyses were also stratified by age (adolescents, age 12–17 and young adults, age 18–32).
Results
The EXT PGS was significantly associated with higher levels of externalizing behaviors among EA adolescents and young adults as well as AA young adults. P3 was inversely associated with externalizing behaviors among EA young adults. EXT PGS was not significantly associated with P3 amplitude and therefore, there was no evidence that P3 amplitude indirectly accounted for the association between EXT PGS and externalizing behaviors.
Conclusions
Both the EXT PGS and P3 amplitude were significantly associated with externalizing behaviors among EA young adults. However, these associations with externalizing behaviors appear to be independent of each other, suggesting that they may index different facets of externalizing.
To determine the proportion of hospitals that implemented 6 leading practices in their antimicrobial stewardship programs (ASPs). Design: Cross-sectional observational survey.
Setting:
Acute-care hospitals.
Participants:
ASP leaders.
Methods:
Advance letters and electronic questionnaires were initiated February 2020. Primary outcomes were percentage of hospitals that (1) implemented facility-specific treatment guidelines (FSTG); (2) performed interactive prospective audit and feedback (PAF) either face-to-face or by telephone; (3) optimized diagnostic testing; (4) measured antibiotic utilization; (5) measured C. difficile infection (CDI); and (6) measured adherence to FSTGs.
Results:
Of 948 hospitals invited, 288 (30.4%) completed the questionnaire. Among them, 82 (28.5%) had <99 beds, 162 (56.3%) had 100–399 beds, and 44 (15.2%) had ≥400+ beds. Also, 230 (79.9%) were healthcare system members. Moreover, 161 hospitals (54.8%) reported implementing FSTGs; 214 (72.4%) performed interactive PAF; 105 (34.9%) implemented procedures to optimize diagnostic testing; 235 (79.8%) measured antibiotic utilization; 258 (88.2%) measured CDI; and 110 (37.1%) measured FSTG adherence. Small hospitals performed less interactive PAF (61.0%; P = .0018). Small and nonsystem hospitals were less likely to optimize diagnostic testing: 25.2% (P = .030) and 21.0% (P = .0077), respectively. Small hospitals were less likely to measure antibiotic utilization (67.8%; P = .0010) and CDI (80.3%; P = .0038). Nonsystem hospitals were less likely to implement FSTGs (34.3%; P < .001).
Conclusions:
Significant variation exists in the adoption of ASP leading practices. A minority of hospitals have taken action to optimize diagnostic testing and measure adherence to FSTGs. Additional efforts are needed to expand adoption of leading practices across all acute-care hospitals with the greatest need in smaller hospitals.
This article is a clinical guide which discusses the “state-of-the-art” usage of the classic monoamine oxidase inhibitor (MAOI) antidepressants (phenelzine, tranylcypromine, and isocarboxazid) in modern psychiatric practice. The guide is for all clinicians, including those who may not be experienced MAOI prescribers. It discusses indications, drug-drug interactions, side-effect management, and the safety of various augmentation strategies. There is a clear and broad consensus (more than 70 international expert endorsers), based on 6 decades of experience, for the recommendations herein exposited. They are based on empirical evidence and expert opinion—this guide is presented as a new specialist-consensus standard. The guide provides practical clinical advice, and is the basis for the rational use of these drugs, particularly because it improves and updates knowledge, and corrects the various misconceptions that have hitherto been prominent in the literature, partly due to insufficient knowledge of pharmacology. The guide suggests that MAOIs should always be considered in cases of treatment-resistant depression (including those melancholic in nature), and prior to electroconvulsive therapy—while taking into account of patient preference. In selected cases, they may be considered earlier in the treatment algorithm than has previously been customary, and should not be regarded as drugs of last resort; they may prove decisively effective when many other treatments have failed. The guide clarifies key points on the concomitant use of incorrectly proscribed drugs such as methylphenidate and some tricyclic antidepressants. It also illustrates the straightforward “bridging” methods that may be used to transition simply and safely from other antidepressants to MAOIs.
Studies suggest that alcohol consumption and alcohol use disorders have distinct genetic backgrounds.
Methods
We examined whether polygenic risk scores (PRS) for consumption and problem subscales of the Alcohol Use Disorders Identification Test (AUDIT-C, AUDIT-P) in the UK Biobank (UKB; N = 121 630) correlate with alcohol outcomes in four independent samples: an ascertained cohort, the Collaborative Study on the Genetics of Alcoholism (COGA; N = 6850), and population-based cohorts: Avon Longitudinal Study of Parents and Children (ALSPAC; N = 5911), Generation Scotland (GS; N = 17 461), and an independent subset of UKB (N = 245 947). Regression models and survival analyses tested whether the PRS were associated with the alcohol-related outcomes.
Results
In COGA, AUDIT-P PRS was associated with alcohol dependence, AUD symptom count, maximum drinks (R2 = 0.47–0.68%, p = 2.0 × 10−8–1.0 × 10−10), and increased likelihood of onset of alcohol dependence (hazard ratio = 1.15, p = 4.7 × 10−8); AUDIT-C PRS was not an independent predictor of any phenotype. In ALSPAC, the AUDIT-C PRS was associated with alcohol dependence (R2 = 0.96%, p = 4.8 × 10−6). In GS, AUDIT-C PRS was a better predictor of weekly alcohol use (R2 = 0.27%, p = 5.5 × 10−11), while AUDIT-P PRS was more associated with problem drinking (R2 = 0.40%, p = 9.0 × 10−7). Lastly, AUDIT-P PRS was associated with ICD-based alcohol-related disorders in the UKB subset (R2 = 0.18%, p < 2.0 × 10−16).
Conclusions
AUDIT-P PRS was associated with a range of alcohol-related phenotypes across population-based and ascertained cohorts, while AUDIT-C PRS showed less utility in the ascertained cohort. We show that AUDIT-P is genetically correlated with both use and misuse and demonstrate the influence of ascertainment schemes on PRS analyses.
Taking a unique materials science approach, this text introduces students to the basic concepts and applications of materials and biomedical engineering and prepares them for the challenges of the new interdisciplinary field of biomaterials science. Split into three sections - Basic Biology Principles, Biological Materials, and Bioinspired Materials and Biomimetics - it presents biological materials along with the structural and functional classification of biopolymers, bioelastomers, foams, and ceramic composites. More traditional biomimetic designs such as Velcro are then discussed in conjunction with new developments that mimic the structure of biological materials at the molecular level, mixing nanoscale with biomolecular designs. Bioinspired design of materials and structures is also covered. Focused presentations of biomaterials are presented throughout the text in succinct boxes, emphasising biomedical applications, whilst the basic principles of biology are explained, so no prior knowledge is required. The topics are supported by approximately 500 illustrations, solved problems, and end-of-chapter exercises.
Nature has evolved a palette of biological materials to address different structural requirements such as:
hardness,
toughness,
stretchability,
light weight.
The intricate and ingenious hierarchical structure is responsible for the outstanding performance. Toughness is conferred by the presence of controlled interfacial features, buckling resistance can be achieved by filling a slender column with a lightweight foam, and armor protection is accomplished by small dermal plates with unique attachment arrangements, resulting in controlled and prescribed flexibility. In Chapters 6–10 we present and interpret selected examples of biological materials. In addition to the structural requirements, there are also functional requirements such as adhesion and optical properties.
The number of elements and compounds that can be synthesized at ambient temperature and in aqueous environments is limited, and therefore the architecture of the structure is of utmost importance.
We introduce the different classes of biological materials in these chapters, following the Wegst–Ashby classification. These were defined in Chapter 2 (Fig. 2.11) as:
It is a misunderstanding to think that the ultimate goal of biomimetics is to reproduce living organisms. There are essential differences, as we list in the following.
(a) Organisms are composed of cells (in the case of humans, 1013 of them). They direct a great deal of the activity. As seen in Chapter 4, each mammalian cell contains 10 000 different proteins, for a total of 500 million. There are numerous types of cells in each organism, and they have complex lives.
(b) Organisms are, for the most part, composed of a limited number of elements: C, Ca, H, O, P, N, and S. Synthetic materials have, on the other hand, a cornucopia of elements, made possible by the synthesis and processing techniques developed by humans.
What we try to do is to emulate the design and assembly principles used in natural materials. In this book we have seen many examples where superior properties are obtained through a hierarchical design and ingenious solutions. Bone, nacre, and dentin have toughnesses significantly superior to those of the mineral constituents, hydroxyapatite and calcium carbonate. Silk reaches strengths higher than 1 GPa using the weak hydrogen bond, through the existence of nano-scale β-sheet crystals with proper dimensions. Bioinspiration requires identification, understanding, and quantification of natural design principles and their replication in synthetic materials, taking into account the intrinsic properties (Studart, 2012). This approach is being pursued not only for structural materials, but also for functional materials and devices. The areas of sensing, optics, architecture, and robotics are exploring biological solutions.
Hydroxylapatite or hydroxyapatite (HAP) is a calcium-phosphate-based mineral of the apatite family. Its chemical formula is Ca10(PO4)6(OH)2. It can be found widely in nature and is the major component of bone, enamel, and dentin in teeth, antler, ganoid fish scales (in alligator gar and Senegal bichir), turtle shells, and armadillo and alligator osteoderms. It exists in minute quantities in the brain (brain sand), without significantly affecting its function. Thus, the expression “having sand in the head” is not without reason. The density of HAP is 3.15 g/cm3. Nonstoichiometric minerals can exist with Ca10(PO4)6(OH, F, Cl, Br)2; if the OH group is replaced by F it is called fluoroapatite; if it is replaced by Cl, it is called chloroapatite. It can be occasionally used as a gem, and the cat’s eye is a commonly known use.
In this chapter, we will concentrate on bone and teeth with emphasis on their structure and mechanical properties. They are HAP–collagen composites and their mechanical properties are the result of the complex interplay and hierarchy built by these structures. Selected calcium-phosphate-based bony tissues with unique functionalities, such as antler, turtle shells, alligator osteoderms, and fish scales, will also be described in the second part of this chapter.
The ultimate goal for a materials engineer is to learn from the lessons of nature and to apply this knowledge to new materials and design. This is not a new quest, and humans have sought inspiration from nature since prehistory. The early materials used by humans were primarily natural: stones, bones, wood, skins, bark. The accelerating pace of the civilizing process has been attributed to the introduction of new synthetic materials; thus, the bronze and iron ages followed the stone age. We have now entered the brave new world of the silicon age, which is bound to produce unimaginable change. Homo silicensis, connected 24/7 to computerized contraptions, can already be seen on campuses and elite coffee houses, sipping lattes.
The constant quest for new materials and designs is leading us to a systematic inquiry of nature in order to unravel its secrets. This is the field of biomimetics, and VELCRO® is the standard example of bioinspired design. It is inspired by the burrs of plants that contain small hooks that attach themselves to animal wool or our clothes.
The quest to mimic nature is now reaching a new chapter. Whereas in the past, structural and functional characteristics served as inspiration for designs and materials, with attention given to mesoscopic and, perhaps, microscopic aspects, the arsenal of new experimental techniques and computational methods is descending to the nanometer scale. This is the scale at which atoms assemble into molecules, and molecules form molecular arrangements such as DNA, RNA, plasmids, and proteins.
Prominent characterization techniques available to modern researchers are (e.g. Gronau et al., 2012):
transmission and scanning electron microscopy at higher and higher resolutions;