Revealing Deformation Mechanisms in Polymer-Grafted Thermoplastic Elastomers via In Situ Small-Angle X-ray Scattering.

The tunable properties of thermoplastic elastomers (TPEs), through polymer chemistry manipulations, enable these technologically critical materials to be employed in a broad range of applications. The need to "dial-in" the mechanical properties and responses of TPEs generally requires the design and synthesis of new macromolecules. In these designs, TPEs with nonlinear macromolecular architectures outperform the mechanical properties of their linear copolymer counterparts, but the differences in the deformation mechanism providing enhanced performance are unknown. Here, in situ small-angle X-ray scattering (SAXS) measurements during uniaxial extension reveal distinct deformation mechanisms between a commercially available linear poly(styrene)-poly(butadiene)-poly(styrene) (SBS) triblock copolymer and the grafted SBS version containing grafted poly(styrene) (PS) chains from the poly(butadiene) (PBD) midblock. The neat SBS (φSBS = 100%) sample deforms congruently with the macroscopic dimensions, with the domain spacing between spheres increasing and decreasing along and transverse to the stretch direction, respectively. At high extensions, end segment pullout from the PS-rich domains is detected, which is indicated by a disordering of SBS. Conversely, the PS-grafted SBS that is 30 vol % SBS and 70% styrene (φSBS = 30%) exhibits a lamellar morphology, and in situ SAXS measurements reveal an unexpected deformation mechanism. During deformation, there are two simultaneous processes: significant lamellar domain rearrangement to preferentially orient the lamellae planes parallel to the stretch direction and crazing. The samples whiten at high strains as expected for crazing, which corresponds with the emergence of features in the 2D SAXS pattern during stretching consistent with fibril-like structures that bridge the voids in crazes. The significant domain rearrangement in the grafted copolymers is attributed to the new junctions formed across multiple PS domains by the grafting of a single chain. The in situ SAXS measurements provide insights into the enhanced mechanical properties of grafted copolymers that arise through improved physical cross-linking that leads to nanostructure domain reorientation for self-reinforcement and craze formation where fibrils help to strengthen the polymer.

More than meets the AI: The possibilities and limits of machine learning in olfaction.

Can machine learning crack the code in the nose? Over the past decade, studies tried to solve the relation between chemical structure and sensory quality with Big Data. These studies advanced computational models of the olfactory stimulus, utilizing artificial intelligence to mine for clear correlations between chemistry and psychophysics. Computational perspectives promised to solve the mystery of olfaction with more data and better data processing tools. None of them succeeded, however, and it matters as to why this is the case. This article argues that we should be deeply skeptical about the trend to black-box the sensory system's biology in our theories of perception. Instead, we need to ground both stimulus models and psychophysical data on real causal-mechanistic explanations of the olfactory system. The central question is: Would knowledge of biology lead to a better understanding of the stimulus in odor coding than the one utilized in current machine learning models? That is indeed the case. Recent studies about receptor behavior have revealed that the olfactory system operates by principles not captured in current stimulus-response models. This may require a fundamental revision of computational approaches to olfaction, including its psychological effects. To analyze the different research programs in olfaction, we draw on Lloyd's "Logic of Research Questions," a philosophical framework which assists scientists in explicating the reasoning, conceptual commitments, and problems of a modeling approach in question.

Nanostructured block copolymer muscles.

High-performance actuating materials are necessary for advances in robotics, prosthetics and smart clothing. Here we report a class of fibre actuators that combine solution-phase block copolymer self-assembly and strain-programmed crystallization. The actuators consist of highly aligned nanoscale structures with alternating crystalline and amorphous domains, resembling the ordered and striated pattern of mammalian skeletal muscle. The reported nanostructured block copolymer muscles excel in several aspects compared with current actuators, including efficiency (75.5%), actuation strain (80%) and mechanical properties (for example, strain-at-break of up to 900% and toughness of up to 121.2 MJ m-3). The fibres exhibit on/off rotary actuation with a peak rotational speed of 450 r.p.m. Furthermore, the reported fibres demonstrate multi-trigger actuation (heat and hydration), offering switchable mechanical properties and various operating modes. The versatility and recyclability of the polymer fibres, combined with the facile fabrication method, opens new avenues for creating multifunctional and recyclable actuators using block copolymers.

Fabricating Robust Constructs with Internal Phase Nanostructures via Liquid-in-Liquid 3D Printing.

The ability to print soft materials into predefined architectures with programmable nanostructures and mechanical properties is a necessary requirement for creating synthetic biomaterials that mimic living tissues. However, the low viscosity of common materials and lack of required mechanical properties in the final product present an obstacle to the use of traditional additive manufacturing approaches. Here, a new liquid-in-liquid 3D printing approach is used to successfully fabricate constructs with internal nanostructures using in situ self-assembly during the extrusion of an aqueous solution containing surfactant and photocurable polymer into a stabilizing polar oil bath. Subsequent photopolymerization preserves the nanostructures created due to surfactant self-assembly at the immiscible liquid-liquid interface, which is confirmed by small-angle X-ray scattering. Mechanical properties of the photopolymerized prints are shown to be tunable based on constituent components of the aqueous solution. The reported 3D printing approach expands the range of low-viscosity materials that can be used in 3D printing, and enables robust constructs production with internal nanostructures and spatially defined features. The reported approach has broad applications in regenerative medicine by providing a platform to print self-assembling biomaterials into complex tissue mimics where internal supramolecular structures and their functionality control biological processes, similar to natural extracellular matrices.

Climate change attribution and legal contexts: evidence and the role of storylines.

In a recent very influential court case, Juliana v. United States, climate scientist Kevin Trenberth used the "storyline" approach to extreme event attribution to argue that greenhouse warming had affected and will affect extreme events in their regions to such an extent that the plaintiffs already had been or will be harmed. The storyline approach to attribution is deterministic rather than probabilistic, taking certain factors as contingent and assessing the role of climate change conditional on those factors. The US Government's opposing expert witness argued that Trenberth had failed to make his case because "all his conclusions of the injuries to Plaintiffs suffer from the same failure to connect his conditional approach to Plaintiffs' local circumstances." The issue is whether it is possible to make statements about individual events based on general knowledge. A similar question is sometimes debated within the climate science community. We argue here that proceeding from the general to the specific is a process of deduction and is an entirely legitimate form of scientific reasoning. We further argue that it is well aligned with the concept of legal evidence, much more so than the more usual inductive form of scientific reasoning, which proceeds from the specific to the general. This has implications for how attribution science can be used to support climate change litigation. "The question is", said Alice, "whether you can make words mean different things." "The question is", said Humpty Dumpty, "which is to be master - that's all." (Lewis Carroll, Alice's Adventures in Wonderland).

Climate scientists set the bar of proof too high.

Standards of proof for attributing real world events/damage to global warming should be the same as in clinical or environmental lawsuits, argue Lloyd et al. The central question that we raise is effective communication. How can climate scientists best and effectively communicate their findings to crucial non-expert audiences, including public policy makers and civil society? To address this question, we look at the mismatch between what courts require and what climate scientists are setting as a bar of proof. Our first point is that scientists typically demand too much of themselves in terms of evidence, in comparison with the level of evidence required in a legal, regulatory, or public policy context. Our second point is to recommend that the Intergovernmental Panel on Climate Change recommend more prominently the use of the category "more likely than not" as a level of proof in their reports, as this corresponds to the standard of proof most frequently required in civil court rooms. This has also implications for public policy and the public communication of climate evidence. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10584-021-03061-9.

Severe weather event attribution: Why values won't go away.

We start by reviewing the complicated situation in methods of scientific attribution of climate change to extreme weather events. We emphasize the social values involved in using both so-called ″storyline″ and ordinary probabilistic or ″risk-based″ methods, noting that one important virtue claimed by the storyline approach is that it features a reduction in false negative results, which has much social and ethical merit, according to its advocates. This merit is critiqued by the probabilistic, risk-based, opponents, who claim the high ground; the usual probabilistic approach is claimed to be more objective and more ″scientific″, under the grounds that it reduces false positive error. We examine this mostly-implicit debate about error, which apparently mirrors the old Jeffrey-Rudner debate. We also argue that there is an overlooked component to the role of values in science: that of second-order inductive risk, and that it makes the relative role of values in the two methods different from what it first appears to be. In fact, neither method helps us to escape social values, and be more scientifically ″objective″ in the sense of being removed or detached from human values and interests. The probabilistic approach does not succeed in doing so, contrary to the claims of its proponents. This is important to understand, because neither method is, fundamentally, a successful strategy for climate scientists to avoid making value judgments.

Environmental catastrophes, climate change, and attribution.

In our discussion of environmental and ecological catastrophes or disasters resulting from extreme weather events, we unite disparate literatures, the biological and the physical. Our goal is to tie together biological understandings of extreme environmental events with physical understandings of extreme weather events into joint causal accounts. This requires fine-grained descriptions, in both space and time, of the ecological, evolutionary, and biological moving parts of a system together with fine-grained descriptions, also in both space and time, of the extreme weather events. We find that both the "storyline" approach to extreme event attribution and the probabilistic "risk-based" approach have uses in such descriptions. However, the storyline approach is more readily aligned with the forensic approach to evidence that is prevalent in the ecological literature, which cultivates expert-based rules of thumb, that is, heuristics, and detailed methods for analyzing causes and mechanisms. We introduce below a number of preliminary examples of such studies as instances of what could be pursued in the future in much more detail.

Differences in Orgasm Frequency Among Gay, Lesbian, Bisexual, and Heterosexual Men and Women in a U.S. National Sample.

There is a notable gap between heterosexual men and women in frequency of orgasm during sex. Little is known, however, about sexual orientation differences in orgasm frequency. We examined how over 30 different traits or behaviors were associated with frequency of orgasm when sexually intimate during the past month. We analyzed a large US sample of adults (N = 52,588) who identified as heterosexual men (n = 26,032), gay men (n = 452), bisexual men (n = 550), lesbian women (n = 340), bisexual women (n = 1112), and heterosexual women (n = 24,102). Heterosexual men were most likely to say they usually-always orgasmed when sexually intimate (95%), followed by gay men (89%), bisexual men (88%), lesbian women (86%), bisexual women (66%), and heterosexual women (65%). Compared to women who orgasmed less frequently, women who orgasmed more frequently were more likely to: receive more oral sex, have longer duration of last sex, be more satisfied with their relationship, ask for what they want in bed, praise their partner for something they did in bed, call/email to tease about doing something sexual, wear sexy lingerie, try new sexual positions, anal stimulation, act out fantasies, incorporate sexy talk, and express love during sex. Women were more likely to orgasm if their last sexual encounter included deep kissing, manual genital stimulation, and/or oral sex in addition to vaginal intercourse. We consider sociocultural and evolutionary explanations for these orgasm gaps. The results suggest a variety of behaviors couples can try to increase orgasm frequency.

Women's Experience of Orgasm During Intercourse: Question Semantics Affect Women's Reports and Men's Estimates of Orgasm Occurrence.

Most women report reliably experiencing orgasm from masturbation, but a smaller proportion of women report regularly experiencing orgasm from intercourse. Research suggests that concurrent clitoral stimulation during intercourse increases the likelihood of orgasm, yet most surveys of orgasm during intercourse leave unspecified whether vaginal intercourse does or does not include concurrent clitoral stimulation (assisted intercourse or unassisted intercourse, respectively). Using an online sample of 1569 men and 1478 women, we tested whether phrasing of questions about the occurrence of orgasm in intercourse modulates women's reported frequency and men's estimates of women's frequency of orgasm in intercourse. Participants provided estimates of orgasm when asked explicitly about intercourse with stimulation unspecified, assisted intercourse, and unassisted intercourse. Women's reports of orgasm occurrence were highest in response to assisted intercourse (51-60%), second highest in response to intercourse with clitoral stimulation unspecified (31-40%), and lowest in response to unassisted intercourse (21-30%). Men's estimates of women's orgasms were highest in response to assisted intercourse (61-70%), and lowest in response to unassisted intercourse (41-50%); in both conditions, men's estimates were significantly higher than women's reports. When clitoral stimulation was unspecified, women interpreted "orgasm in intercourse" in three ways: as from intercourse alone, as including concurrent clitoral stimulation though it was unspecified, or as an average of assisted and unassisted intercourse. Taken together, these results demonstrate that the phrasing of questions about women's orgasm produces markedly different orgasm estimates, and suggest that concurrent clitoral stimulation increases the likelihood of women experiencing orgasm in intercourse.

Correction to: Women's Experience of Orgasm During Intercourse: Question Semantics Affect Women's Reports and Men's Estimates of Orgasm Occurrence.

The name of coauthor Kaytlin J. Renfro has been corrected since this article was originally published.

Getting the Hologenome Concept Right: an Eco-Evolutionary Framework for Hosts and Their Microbiomes.

Given the complexity of host-microbiota symbioses, scientists and philosophers are asking questions at new biological levels of hierarchical organization-what is a holobiont and hologenome? When should this vocabulary be applied? Are these concepts a null hypothesis for host-microbe systems or limited to a certain spectrum of symbiotic interactions such as host-microbial coevolution? Critical discourse is necessary in this nascent area, but productive discourse requires that skeptics and proponents use the same lexicon. For instance, critiquing the hologenome concept is not synonymous with critiquing coevolution, and arguing that an entity is not a primary unit of selection dismisses the fact that the hologenome concept has always embraced multilevel selection. Holobionts and hologenomes are incontrovertible, multipartite entities that result from ecological, evolutionary, and genetic processes at various levels. They are not restricted to one special process but constitute a wider vocabulary and framework for host biology in light of the microbiome.

Model robustness as a confirmatory virtue: The case of climate science.

I propose a distinct type of robustness, which I suggest can support a confirmatory role in scientific reasoning, contrary to the usual philosophical claims. In model robustness, repeated production of the empirically successful model prediction or retrodiction against a background of independently-supported and varying model constructions, within a group of models containing a shared causal factor, may suggest how confident we can be in the causal factor and predictions/retrodictions, especially once supported by a variety of evidence framework. I present climate models of greenhouse gas global warming of the 20th Century as an example, and emphasize climate scientists' discussions of robust models and causal aspects. The account is intended as applicable to a broad array of sciences that use complex modeling techniques.

Variation in orgasm occurrence by sexual orientation in a sample of U.S. singles.

INTRODUCTION: Despite recent advances in understanding orgasm variation, little is known about ways in which sexual orientation is associated with men's and women's orgasm occurrence. AIM: To assess orgasm occurrence during sexual activity across sexual orientation categories. METHODS: Data were collected by Internet questionnaire from 6,151 men and women (ages 21-65+ years) as part of a nationally representative sample of single individuals in the United States. Analyses were restricted to a subsample of 2,850 singles (1,497 men, 1,353 women) who had experienced sexual activity in the past 12 months. MAIN OUTCOME MEASURES: Participants reported their sex/gender, self-identified sexual orientation (heterosexual, gay/lesbian, bisexual), and what percentage of the time they experience orgasm when having sex with a familiar partner. RESULTS: Mean occurrence rate for experiencing orgasm during sexual activity with a familiar partner was 62.9% among single women and 85.1% among single men, which was significantly different (F1,2848 = 370.6, P < 0.001, η(2) = 0.12). For men, mean occurrence rate of orgasm did not vary by sexual orientation: heterosexual men 85.5%, gay men 84.7%, bisexual men 77.6% (F2,1494 = 2.67, P = 0.07, η(2) = 0.004). For women, however, mean occurrence rate of orgasm varied significantly by sexual orientation: heterosexual women 61.6%, lesbian women 74.7%, bisexual women 58.0% (F2,1350 = 10.95, P < 0.001, η(2) = 0.02). Lesbian women had a significantly higher probability of orgasm than did either heterosexual or bisexual women (P < 0.05). CONCLUSIONS: Findings from this large dataset of U.S. singles suggest that women, regardless of sexual orientation, have less predictable, more varied orgasm experiences than do men and that for women, but not men, the likelihood of orgasm varies with sexual orientation. These findings demonstrate the need for further investigations into the comparative sexual experiences and sexual health outcomes of sexual minorities.

Female sexual arousal: genital anatomy and orgasm in intercourse.

In men and women sexual arousal culminates in orgasm, with female orgasm solely from sexual intercourse often regarded as a unique feature of human sexuality. However, orgasm from sexual intercourse occurs more reliably in men than in women, likely reflecting the different types of physical stimulation men and women require for orgasm. In men, orgasms are under strong selective pressure as orgasms are coupled with ejaculation and thus contribute to male reproductive success. By contrast, women's orgasms in intercourse are highly variable and are under little selective pressure as they are not a reproductive necessity. The proximal mechanisms producing variability in women's orgasms are little understood. In 1924 Marie Bonaparte proposed that a shorter distance between a woman's clitoris and her urethral meatus (CUMD) increased her likelihood of experiencing orgasm in intercourse. She based this on her published data that were never statistically analyzed. In 1940 Landis and colleagues published similar data suggesting the same relationship, but these data too were never fully analyzed. We analyzed raw data from these two studies and found that both demonstrate a strong inverse relationship between CUMD and orgasm during intercourse. Unresolved is whether this increased likelihood of orgasm with shorter CUMD reflects increased penile-clitoral contact during sexual intercourse or increased penile stimulation of internal aspects of the clitoris. CUMD likely reflects prenatal androgen exposure, with higher androgen levels producing larger distances. Thus these results suggest that women exposed to lower levels of prenatal androgens are more likely to experience orgasm during sexual intercourse.

Response to Puts and Dawood's 'the evolution of female orgasm: adaptation or byproduct?'--Been there.

David Puts and Khytam Dawood's recent critique of my book, The Case of the Female Orgasm: Bias in the Science of Evolution, attempts to make plausible an adaptive account of female orgasm based on a hypothesized mechanism of uterine upsuck and sperm competition. Yet the authors fail to respond to the criticisms of such accounts that I detailed previously in my book. They raise a further concern about my definition of adaptation--a red herring--and manufacture a conceptual error regarding heritability that they then attribute to me. Most seriously, they fail to address the glaring failure of sperm competition accounts to accord with evidence from sexology. Specifically, the distribution curve of orgasm-with-intercourse--according to Dawood et al.'s own data, as well as others'--is relatively flat across the various classes. This curve needs to be tested against a well-formed multistrategy adaptive hypothesis; it cannot be explained by the adaptive account defended by Puts and Dawood in their critique.