Spearing mantis shrimps are aggressive crustaceans using specialized appendages with sharp spikes to capture fishes with a fast movement. Each spike is a biological tool that have to combine high toughness, as required by the initial impact with the victim, with high stiffness and strength, to ensure sufficient penetration while avoid breaking. We performed a multimodal analysis to uncover the design strategies of this harpoon based on chitin. We found that the spike is a slightly hooked hollow beam with the outer surface decorated by serrations and grooves to enhance cutting and interlocking. The cuticle of the spike resembles a multilayer composite: an outer heavily mineralized, stiff and hard region (with average indentation modulus and hardness of 68 and 3 GPa), providing high resistance to contact stresses, is combined with a less mineralized region, which occupies a large fraction of the cuticle (up to 50%) and features parallel fibers oriented longitudinally, enhancing stiffness and strength. A central finding of our work is the presence of a tiny interphase (less than 10 μm in width) based on helical fibers and showing a spatial modulation in mechanical properties, which has the critical task to integrate the stiff but brittle outer layer with the more compliant highly anisotropic parallel fiber region. We highlighted the remarkable ability of this helicoidal region to stop nanoindentation-induced cracks. Using three-dimensional multimaterial printing to prototype spike-inspired composites, we showed how the observed construction principles can not only hamper damage propagation between highly dissimilar layers (resulting in composites with the helical interphase absorbing 50% more energy than without it) but can also enhance resistance to puncture (25% increase in the force required to penetrate the composites with a blunt tool). Such findings may provide guidelines to design lightweight harpoons relying on environmentally friendly and recyclable building blocks.
We recount the life, work, and legacy of the theoretical physicist Roy Glauber (1925-2018). Admitted to Harvard at age sixteen, called upon to participate in the Manhattan Project at age eighteen, and appointed to the Harvard Physics faculty at age twenty-nine, Glauber is credited with seminal contributions to three separate fields of physics: nuclear scattering, statistical physics, and foundational work in quantum optics, which earned him the 2005 Nobel Prize in Physics. Over decades, Glauber was also a dedicated teacher of high-school, college, and graduate students. His pedagogical gifts are reflected in his lucid papers that read as if they were written yesterday.
The mid-infrared (mid-IR) anisotropic optical response of a material probes vibrational fingerprints and absorption bands sensitive to order, structure and direction dependent stimuli. Such anisotropic properties play a fundamental role in catalysis, optoelectronic, photonic, polymer and biomedical research and applications. Infrared dual-comb polarimetry (IR-DCP) is introduced as a powerful new spectroscopic method for the analysis of complex dielectric functions and anisotropic samples in the mid-IR range. IR DCP enables novel hyperspectral and time-resolved applications far beyond the technical possibilities of classical Fourier-transform IR (FTIR) approaches. The method unravels structure–spectra relations at high spectral bandwidth (100 cm–1) and short integration times of 65 µs, with previously unattainable time resolutions for spectral IR polarimetric measurements for potential studies of noncyclic and irreversible processes. The polarimetric capabilities of IR-DCP are demonstrated by investigating an anisotropic inhomogeneous free-standing nanofiber scaffold for neural tissue applications. Polarization sensitive multi-angle dual-comb transmission amplitude and absolute phase measurements (separately for ss-, pp-, ps- and sp-polarized light) allow the in-depth probing of the samples’ orientation dependent vibrational absorption properties. Mid-IR anisotropies can be quickly identified by cross-polarized IR-DCP polarimetry.
There is a pseudo-embryology existing today, well nourished by popular science, religious ideologies, and the public media. Just as eugenics was a pseudoscience that influenced (and still influences) American popular culture and which was responsible for racist anti-immigration laws (such as the Immigration Restriction Act of 1924), pseudo-embryology is also influencing popular culture and legislation. This new pseudoscience promotes the belief that science supports current zygotic and fetal personhood movements and anti-abortion legislation. However, what often passes for science are actually ideological myths, often grounded in and supporting male superiority. Indeed, the first myth of pseudo-embryology is that fertilization is a masculine act that can be viewed as a classical hero narrative. The second myth is that fertilization is ensoulment, allowing it to displace the feminine act of birth as to when life begins. Here, DNA is seen to play the secular analogue of soul. The third myth is that the fetus in the womb is an independent autonomous entity and that birth merely moves the fetus from the womb to the outside world. This expresses the “seed-in-the-soil” myth that was also prevalent in ancient cultures. In this manner, masculine stories of fertilization are valorized while feminine narratives of birth are suppressed. So when public narratives discuss what “science” says about when human life begins, we are not really discussing science. Rather, we are allowing our discussions to fall back into tenacious ancient misogynist myths that have nothing to do with the conclusions of modern developmental biology.
End stage renal disease (ESRD), characterized by cessation in kidney function, has been linked to severe metabolic disturbances, caused by buildup of toxic solutes in blood. To remove these solutes, ESRD patients undergo dialysis. As a proof of concept, we tested whether ESRD-related metabolic signatures can be detected in perspiration samples using a combined methodology. Our rapid methodology involves swabbing a glass slide across the patient’s forehead, detecting the metabolites in the imprint using desorption electrospray ionization mass spectrometry, and identifying the key differences using machine learning methods. Based on collecting 42 healthy and 27 ESRD samples, we find saturated fatty acids are consistently suppressed in ESRD patients, with little change after dialysis. Also, our method enables the detection of uremic solutes, where we find elevated levels of uric acid (6.7 fold higher on average) that sharply decrease after dialysis. Beyond the study of individual metabolites, we find that a lasso model, which selects for 8 m/z fragments from 24,602 detected analytes, achieves area under the curve performance of 0.85 and 0.87 on training (n=52) and validation sets (n=17) respectively. Together, these results suggest that this methodology is promising for detecting signatures relevant for Precision Health.
Preface by Prof. Titia de Lange, Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, NY 10065, USA The 19th Annual Wiley Prize in Biomedical Sciences celebrated a breakthrough in cell biology: how membrane-less cellular compartments are formed. The existence of membrane-less organelles, often called bodies or puncta, have been known for a long time, but what exactly they represented and how they were formed was not known. This problem was solved by a physicist, Clifford Brangwynne, a cell biologist, Anthony Hyman and a chemist, Michael Rosen. Each, synergistically, made groundbreaking contributions to the discovery that membrane-less organelles are liquid-liquid phase-separated entities. The two independent discoveries leading to the principle that multivalent low-affinity interactions between selected sets of macromolecules, some containing intrinsically disordered regions, formed a molecular condensate with unique dynamic properties, gave birth to the large, blossoming field of biomolecular condensates. The implications of those findings have influenced almost all further research of intracellular processes, including RAS signaling, immune synapses, DNA repair, transcriptional activation, and the functions of nuclear pores, the nucleolus and centrosomes. In this Perspective article, the laureates of the award take us on their personal and professional trip that led to their scientific discoveries. Their stories are a celebration of the interdisciplinary essence of Natural Sciences and the potential unlocked when scientists from different fields work together to solve mysteries.
Hot excitons are usually neglected in optical spectroscopy in 2D semiconductors for the sake of momentum conservation, as the majority of hot excitons are out of light cones. In this letter, we elaborate the contribution of hot excitons to optical properties of monolayer MoSe2 with photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy. With the excitation-intensity-dependent PL, temperature-dependent PL and PLE experiments combined with the simulations, we experimentally distinguish the influences of the exciton temperature and the lattice temperature in the PL spectrum. It is concluded that the acoustic phonon assisted photoluminescence accounts for the non-Lorentzian high energy tail in the PL spectrum and the hot exciton effect is significant to linear optical properties of TMDs. Besides, the effective exciton temperature is found to be several tens of Kelvin higher than the lattice temperature at non-resonant optical excitation. It indicates that the exciton temperature needs to be carefully taken into account when considering the exciton related quantum phase phenomena such as exciton condensation. It is experimentally demonstrated that the effective exciton temperature can be tuned by excitation energy.
Since a polyvalent strategy has recently been assumed to be adopted by Deinococcus radiodurans that can generate various resistance against many different detrimental sources of oxidative damage (e.g. reactive oxygen species, heavy metal ions and ionising radiation), investigating more than one restorative metabolic activities and their interrelation of the very same entities of Deinococcus radiodurans is of great significance for exploring its polyextremophile nature, which will be insightful for obtaining fundamental generic insights into life sustainability. Herein, we apply mainly fluorescence microscopy and back reflection microscopy to visibly assess the respective activities of superoxide radical generation and silver ion metabolism for individual Deinococcus radiodurans. Strikingly, only a minority (<20%) of the bacteria which show low superoxide radical levels is revealed to exhibit considerable formation of silver nanoparticles whilst those containing more superoxide radicals all show minimum silver ion metabolism. The discovery of the strong negative correlation for the small subpopulation between the two visualised different metabolic activities not only provides direct experimental evidence in terms of bacterial functionality for the inferred survival regime of the extreme microbe, but also suggests a new way of chemically examining biology from the perspective of inter-functional relationship.
Mitochondria continuously undergo morphologically dynamic processes of fusion and fission to maintain their size, shape, amount, and function; yet the precise molecular mechanisms by which mitochondrial dynamics is regulated remain to be fully elucidated. Here, we report a previous unappreciated but critical role of eukaryotic elongation factor 2 (eEF2) in regulating mitochondrial fission. eEF2, a G-protein superfamily member encoded by EEF2 gene in human, has long been appreciated as a promoter of the GTP-dependent translocation of the ribosome during protein synthesis. We found unexpectedly in several types of cells that eEF2 was not only present in the cytosol but also in the mitochondria. Furthermore, we showed that mitochondrial length was significantly increased when the cells were subjected to silencing of eEF2 expression, suggesting a promotive role for eEF2 in the mitochondrial fission. Inversely, overexpression of eEF2 decreased mitochondrial length, suggesting an increase of mitochondrial fission. Inhibition of mitochondrial fission caused by eEF2 depletion was accompanied by alterations of cellular metabolism, as evidenced by a reduction of oxygen consumption and an increase of oxidative stress in the mitochondria. We further demonstrated that eEF2 and Drp1, a key driver of mitochondrial fission, co-localized at the mitochondria, as evidenced by microscopic observation, co-immunoprecipitation, and GST pulldown assay. Deletion of the GTP binding motif of eEF2 decreased its association with Drp1 and abrogated its effect on mitochondria fission. Moreover, we showed that wild-type eEF2 stimulated GTPase activity of Drp1, whereas deletion of the GTP binding site of eEF2 diminished its stimulatory effect on GTPase activity. This work not only reveals a previously unrecognized function of eEF2 (i.e., promoting mitochondrial fission), but also uncovers the interaction of eEF2 with Drp1 as a novel regulatory mechanism of the mitochondrial dynamics. Therefore, eEF2 warrants further exploration for its potential as a therapeutic target for the mitochondria-related diseases.
This Research Highlight showcases the two Research Papers entitled, A precise photometric ratio via laser excitation of the sodium layer – I. One-photon excitation using 342.78 nm light, https://doi.org/10.1093/mnras/stab1621 and A precise photometric ratio via laser excitation of the sodium layer – II. Two-photon excitation using lasers detuned from 589.16 nm and 819.71 nm resonances, https://doi.org/10.1093/mnras/stab1619.
Silicon-based anodes with lithium ions as charge carriers have the highest predicted theoretical specific capacity of 3579 mA h g-1 (for Li15Si4). Contemporary electrodes do not achieve this theoretical value largely because conventional production paradigms rely on the mixing of weakly coordinated components. In this paper, a semi-conductive triazine-based graphdiyne polymer network is grown around silicon nanoparticles directly on the current collector, a copper sheet. The porous, semi-conducting organic framework (i) adheres to the current collector on which it grows via cooperative van der Waals interactions, (ii) acts effectively as conductor for electrical charges and binder of silicon nanoparticles via conjugated, covalent bonds, and (iii) enables selective transport of electrolyte and Li-ions through pores of defined size. The resulting anode shows extraordinarily high capacity at the theoretical limit of fully lithiated silicon. Finally, we combine our anodes in proof-of-concept battery assemblies using a conventional layered Ni-rich oxide cathode.
￼￼￼￼￼￼￼The free propagation in time of a normalisable wave packet is the oldest problem of continuum quantum mechanics. Its motion from microscopic to macroscopic distance is the way in which most quantum systems are detected experimentally. Although much studied and analysed since 1927 and presented in many text books, here the problem is re-appraised from the standpoint of semi-classical mechanics. Particular aspects are the emergence of deterministic trajectories of particles emanating from a region of atomic dimensions and the interpretation of the wave function as describing a single particle or an ensemble of identical particles. Of possible wave packets, that of gaussian form is most studied due to the simple exact form of the time-dependent solution in real and in momentum space. Furthermore, this form is important in laser optics. Here the equivalence of the time-dependent Schroedinger equation to the paraxial equation for the propagation of light is demonstrated explicitly. This parallel helps to understand the relevance of trajectory concepts and the conditions necessary for the perception of motion as classical.
This Research Highlight provides context for the report of Gope et al. on experimental and computational probes of the decay of doubly-ionized methanol to H3+ and HCO+/COH+. The formation of the H3+ ionic product is shown to occur through the agency of a roaming H2 molecule generated from the carboxyl moiety that undergoes prompt proton transfer from the carbon atom, or, delayed proton transfer from the oxygen atom. This novel method for H3+ formation is contrasted with the conventional ion-molecule pathway, known for over a century, that forms the basis for interstellar molecule formation.
Background: Oral squamous cell carcinoma (OSCC) accounts for 90 % of oral cancers. If a necessary intervention before tumorigenesis could be conducted, the current 60% 5-year survival rate would be expected to be majorly improved. This fact motivates the search for developing a highly sensitive and specific in vitro diagnostic method to conduct rapid OSCC screening. Method: Serum samples from 819 volunteers, consisted of 241 healthy contrast (HC) and 578 OSCC patients, were collected, and their metabolic profiles were acquired using conductive polymer spray ionization mass spectrometry (CPSI-MS). Univariate analysis was used to select significantly changed metabolite ions in the OSCC group compared to the HC group. Identities of these metabolite ions were determined by MS/MS experiments and reconfirmed at the tissue level by desorption electrospray ionization mass spectrometry (DESI-MS). The supporting vector machine (SVM) algorithm was employed as the machine learning model to implement the automatic prediction of OSCC. Results: Through statistical analysis, 65 metabolites were selected as potential characteristic marker candidates for serum OSCC screening. In situ validation by DESI-MSI revealed that 8 out of top 10 metabolites showed the same trends of change in tissue and serum. With the aid of machine learning, OSCC can be distinguished from HC with an accuracy of 98.0 % by cross-validation in the discovery cohort and 89.2% accuracy in the validation cohort. Furthermore, orthogonal partial least square-discriminant analysis (OPLS-DA) also showed the potential for recognizing OSCC stages. Conclusion: Using CPSI-MS combined with SVM, it is possible to distinguish OSCC from HC in a few minutes with high specificity and sensitivity, making this rapid diagnostic procedure a promising approach for high-risk population screening.
Molecular motors change conformation under the influence of light and when attached to host molecules they may find applications as sensors and switchable catalysts. Here we present a porphyrin macrocyclic host functionalized with two motor appendages for future catalytic applications. The compound is formed as a mixture of six stereoisomers (three sets of enantiomers), which have been separated by (chiral) chromatography. 1H NMR and chiral spectroscopy revealed that in one set of diastereomers the two motors interact with the cavity of the host (bound-bound), whereas in a second set one interacts and the other one does not (bound-loose). In the third set both motors do not interact with the host compound (loose-loose). The motorized hosts bind guest molecules in the order: (loose-loose) > (bound-loose) > (bound-bound). They can be switched with light to pseudo-identical diastereomers, leading to orthogonal behavior in the light-gated binding of guest molecules. Whereas the photo-isomerization of the diastereomer set loose-loose significantly lowers the binding affinity for viologen guests, the opposite is true for the diastereomer set bound-bound, i.e. the binding affinity increases. For the diastereomer set bound-loose no influence on guest binding is observed as the effect of photoisomerization on the motors is cancelled out.