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Cylinder buckling is notoriously sensitive to small geometric imperfections. This is an underlying motivation for the use of knock-down factors in the design process, especially in circumstances in which minimum weight is a key design goal, an approach well-established at NASA, for example. Not only does this provide challenges in the practical design of this commonly occurring structural load-bearing configuration, but also in the carefully controlled laboratory setting. The recent development of 3D-printing (additive manufacturing) provides an appealing experimental platform for conducting relatively high-fidelity experiments on the buckling of cylinders. However, in addition to geometric precision, there are a number of shortcomings with this approach, and this article seeks to describe the challenges and opportunities associated with the use of 3D-printing in cylinder buckling in general, and probing the robustness of equilibrium configurations in particular. This article is part of the theme issue ‘Probing and dynamics of shock sensitive shells’. 

The past ∼200 million years of Earth's geomagnetic field behavior have been recorded within oceanic basalts, many of which are only accessible via scientific ocean drilling. Obtaining the best possible paleomagnetic measurements from such valuable samples requires an a priori understanding of their magnetic mineralogies when choosing the most appropriate protocol for stepwise demagnetization experiments (either alternating field or thermal). Here, we present a quick, and non‐destructive method that utilizes the amplitude‐dependence of magnetic susceptibility to screen submarine basalts prior to choosing a demagnetization protocol, whenever conducting a pilot study or other detailed rock‐magnetic characterization is not possible. We demonstrate this method using samples acquired during International Ocean Discovery Program Expedition 391. Our approach is rooted in the observation that amplitude‐dependent magnetic susceptibility is observed in basalt samples whose dominant magnetic carrier is multidomain titanomagnetite (∼TM_60–65, (Ti_0.60–0.65Fe_0.35–0.40)Fe₂O₄). Samples with low Ti contents within titanomagnetite or samples that have experienced a high degree of oxidative weathering do not display appreciable amplitude dependence. Due to their low Curie temperatures, basalts that possess amplitude‐dependence should ideally be demagnetized either using alternating fields or via finely‐spaced thermal demagnetization heating steps below 300°C. Our screening method can enhance the success rate of paleomagnetic studies of oceanic basalt samples.

 

Viruses that infect phytoplankton are abundant in all regions of the global ocean. Despite their ubiquity, little is understood regarding how biotic interactions can alter virus infection success as well as the fate of phytoplankton hosts. In previous work, the bacterially derived compound 2-heptyl-4-quinolone (HHQ) has been shown to protect the cosmopolitan coccolithophoreEmiliania huxleyifrom virus-induced mortality. The present study explores the potential mechanisms through which protection is conferred. Using a suite of transmission electron microscopy and physiological diagnostic staining techniques, we show that whenE. huxleyiis exposed to HHQ, viruses can gain entry into cells but viral replication and release is inhibited. These findings are supported by a smaller burst size, as well as lower infectious and total virus production when the host is treated with nanomolar concentrations of HHQ. Additionally, diagnostic staining results indicate that programmed cell death markers commonly associated with viral infection are not activated when infectedE. huxleyiare exposed to HHQ. Together, these results suggest that the ability of HHQ to inhibit infectious viral production protects the alga not from getting infected, but from cell lysis. This work identifies a new mechanistic role of bacterial quorum sensing molecules in mediating viral infections in marine microbial systems.