109 research outputs found
Simulations of a lattice model of two-headed linear amphiphiles: influence of amphiphile asymmetry
Using a 2D lattice model, we conduct Monte Carlo simulations of micellar
aggregation of linear-chain amphiphiles having two solvophilic head groups. In
the context of this simple model, we quantify how the amphiphile architecture
influences the critical micelle concentration (CMC), with a particular focus on
the role of the asymmetry of the amphiphile structure. Accordingly, we study
all possible arrangements of the head groups along amphiphile chains of fixed
length and 16 molecular units. This set of idealized amphiphile
architectures approximates many cases of symmetric and asymmetric gemini
surfactants, double-headed surfactants and boloform surfactants. Consistent
with earlier results, we find that the number of spacer units separating
the heads has a significant influence on the CMC, with the CMC increasing with
for . In comparison, the influence of the asymmetry of the chain
architecture on the CMC is much weaker, as is also found experimentally.Comment: 30 pages, 17 fgure
Generative AI in Computing Education: Perspectives of Students and Instructors
Generative models are now capable of producing natural language text that is,
in some cases, comparable in quality to the text produced by people. In the
computing education context, these models are being used to generate code, code
explanations, and programming exercises. The rapid adoption of these models has
prompted multiple position papers and workshops which discuss the implications
of these models for computing education, both positive and negative. This paper
presents results from a series of semi-structured interviews with 12 students
and 6 instructors about their awareness, experiences, and preferences regarding
the use of tools powered by generative AI in computing classrooms. The results
suggest that Generative AI (GAI) tools will play an increasingly significant
role in computing education. However, students and instructors also raised
numerous concerns about how these models should be integrated to best support
the needs and learning goals of students. We also identified interesting
tensions and alignments that emerged between how instructors and students
prefer to engage with these models. We discuss these results and provide
recommendations related to curriculum development, assessment methods, and
pedagogical practice. As GAI tools become increasingly prevalent, it's
important to understand educational stakeholders' preferences and values to
ensure that these tools can be used for good and that potential harms can be
mitigated.Comment: 10 pages, 1 figur
Simulations of a lattice model of two-headed linear amphiphiles: influence of amphiphile asymmetry
Using a 2D lattice model, we conduct Monte Carlo simulations of micellar
aggregation of linear-chain amphiphiles having two solvophilic head groups. In
the context of this simple model, we quantify how the amphiphile architecture
influences the critical micelle concentration (CMC), with a particular focus on
the role of the asymmetry of the amphiphile structure. Accordingly, we study
all possible arrangements of the head groups along amphiphile chains of fixed
length and 16 molecular units. This set of idealized amphiphile
architectures approximates many cases of symmetric and asymmetric gemini
surfactants, double-headed surfactants and boloform surfactants. Consistent
with earlier results, we find that the number of spacer units separating
the heads has a significant influence on the CMC, with the CMC increasing with
for . In comparison, the influence of the asymmetry of the chain
architecture on the CMC is much weaker, as is also found experimentally.Comment: 30 pages, 17 fgure
Bis[2,2′-(2-aminoethylimino)di(ethylammonium)] di-μ-sulfido-bis[disulfidostannate(IV)]
The asymmetric unit of the title compound, (C6H20N4)2[Sn2S6], comprises half of a [Sn2S6]4− anion and a diprotonated tris(2-aminoethyl)amine cation. The anion lies on an inversion center, while the atoms of the cation occupy general positions. An intramolecular N—H⋯N hydrogen bond is observed in the cation. In the crystal, strong N—H⋯S hydrogen bonding between the terminal sulfur atoms of the anion and the protonated amine N atoms of the cations result in a three-dimensional network
Predators vs. alien: differential biotic resistance to an invasive species by two resident predators
The success of invading species can be restricted by interspecific interactions such as competition and predation (i.e. biotic resistance) from resident species, which may be natives or previous invaders. Whilst there are myriad examples of resident species preying on invaders, simply showing that such an interaction exists does not demonstrate that predation limits invader establishment, abundance or spread. Support for this conclusion requires evidence of negative associations between invaders and resident predators in the field and, further, that the predator-prey interaction is likely to strongly regulate or potentially de-stabilise the introduced prey population. Moreover, it must be considered that different resident predator species may have different abilities to restrict invaders. In this study, we show from analysis of field data that two European predatory freshwater amphipods, Gammarus pulex and Gammarus duebeni celticus, have strong negative field associations with their prey, the invasive North American amphipod Crangonyx pseudogracilis. This negative field association is significantly stronger with Gammarus pulex, a previous and now resident invader in the study sites, than with the native Gammarus duebeni celticus. These field patterns were consistent with our experimental findings that both resident predators display potentially population de-stabilising Type II functional responses towards the invasive prey, with a significantly greater magnitude of response exhibited by Gammarus pulex than by Gammarus duebeni celticus. Further, these Type II functional responses were consistent across homo- and heterogeneous environments, contrary to the expectation that heterogeneity facilitates more stabilising Type III functional responses through the provision of prey refugia. Our experimental approach confirms correlative field surveys and thus supports the hypothesis that resident predatory invertebrates are differentially limiting the distribution and abundance of an introduced invertebrate. We discuss how the comparative functional response approach not only enhances understanding of the success or failure of invasions in the face of various resident predators, but potentially also allows prediction of population- and community-level outcomes of species introductions
Measurement properties of the EQ-5D across four major geriatric conditions: Findings from TOPICS-MDS
Background: As populations age, chronic geriatric conditions linked to progressive organ failure jeopardize health-related quality of life (HRQoL). Thus, this research assessed the validity and applicability of the EQ-5D (a common HRQoL instrument) across four major chronic geriatric conditions: hearing issues, joint damage, urinary incontinence, or dizziness with falls. Methods: The study sample comprised 25,637 community-dwelling persons aged 65 years and older residing in the Netherlands (Data source: TOPICS-MDS, www.topics-mds.eu ). Floor and ceiling effects were examined. To assess convergent validity, random effects meta-correlations (Spearman's rho) were derived between individual EQ-5D domains and related survey items. To further examine construct validity, the association between sociodemographic characteristics and EQ-5D summary scores were assessed using linear mixed models. Outcomes were compared to the overall study population as well as a 'healthy' subgroup reporting no major chronic conditions. Results: Whereas ceiling effects were observed in the overall study population and the 'healthy' subgroup, such was not the case in the geriatric condition subgroups. The majority of hypotheses regarding correlations between survey items and sociodemographic associations were supported. EQ-5D summary scores were lower in respondents who were older, female, widowed/single, lower educated, and living alone. Increasing co-morbidity had a clear negative effect on EQ-5D scores. Conclusion: This study supported the construct validity of the EQ-5D across four major geriatric conditions. For older persons who are generally healthy, i.e. reporting few to no chronic conditions, the EQ-5D confers poor discriminative ability due to ceiling effects. Although the overall dataset initially suggested poor discriminative ability for the EQ-5D, such was not the case within subgroups presenting with major geriatric conditions
Rethinking energy, climate and security: a critical analysis of energy security in the US
Understanding the complicated relationship between energy, climate and security is vital both to the study of international relations and to ensure the continued survival of a world increasingly threatened by environmental change. Climate change is largely caused by burning fossil fuels for energy, but while discussions on the climate consider the role of energy, energy security debates largely overlook climate concerns. This article traces the separation between energy and climate through an analysis of US energy security discourse and policy. It shows that energy security is continually constructed as national security, which enables very particular policy choices and prioritises it above climate concerns. Thus, in many cases, policies undertaken in the name of energy security contribute directly to climate insecurity. The article argues that the failure to consider securing the climate as inherently linked to energy security is not just problematic, but, given global warming, potentially harmful. Consequently, any approach to dealing with climate change has to begin by rethinking energy security and security more broadly, as national (energy) security politics no longer provides security in any meaningful sense
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