More Like this

1. Growth and morphogenesis of the gastropod shell

   https://doi.org/10.1073/pnas.1816089116  

   Johnson, Adam B.; Fogel, Nina S.; Lambert, J. David (March 2019, Proceedings of the National Academy of Sciences)

   Gastropod shell morphologies are famously diverse but generally share a common geometry, the logarithmic coil. Variations on this morphology have been modeled mathematically and computationally but the developmental biology of shell morphogenesis remains poorly understood. Here we characterize the organization and growth patterns of the shell-secreting epithelium of the larval shell of the basket whelkTritia(also known asIlyanassa). Despite the larval shell’s relative simplicity, we find a surprisingly complex organization of the shell margin in terms of rows and zones of cells. We examined cell division patterns with EdU incorporation assays and found two growth zones within the shell margin. In the more anterior aperture growth zone, we find that inferred division angles are biased to lie parallel to the shell edge, and these divisions occur more on the margin’s left side. In the more posterior mantle epithelium growth zone, inferred divisions are significantly biased to the right, relative to the anterior–posterior axis. These growth zones, and the left–right asymmetries in cleavage patterns they display, can explain the major modes of shell morphogenesis at the level of cellular behavior. In a gastropod with a different coiling geometry,Planorbellasp., we find similar shell margin organization and growth zones asTritia, but different left–right asymmetries than we observed in the helically coiled shell ofTritia. These results indicate that differential growth patterns in the mantle edge epithelium contribute to shell shape in gastropod shells and identify cellular mechanisms that may vary to generate shell diversity in evolution. 

   more » « less
2. Shell Thickness and Heterogeneity Dependence of Triplet Energy Transfer between Core–Shell Quantum Dots and Adsorbed Molecules

   https://doi.org/10.1021/jacs.5c01838  

   Jin, Tao; Zhang, Zhendian; He, Sheng; Kaledin, Alexey_L; Xu, Zihao; Liu, Yawei; Zhang, Peng; Beratan, David_N; Lian, Tianquan (April 2025, Journal of the American Chemical Society)
3. Shell model results for nuclear β−-decay properties of sd-shell nuclei

   https://doi.org/10.1093/ptep/ptaa012  

   Kumar, Anil; Srivastava, Praveen C; Suzuki, Toshio (March 2020, Progress of Theoretical and Experimental Physics)

   Abstract We evaluate the allowed $$\beta^-$$-decay properties of nuclei with $Z = 8$$–$$15$ systematically under the framework of the nuclear shell model using the valence space Hamiltonians derived from modern ab initio methods, such as in-medium similarity renormalization group and coupled-cluster theory. For comparison we also show results obtained with fitted interaction derived from chiral effective field theory and phenomenological universal $sd$-shell Hamiltonian version B interaction. We have performed calculations for O $$\rightarrow$$ F, F $$\rightarrow$$ Ne, Ne $$\rightarrow$$ Na, Na $$\rightarrow$$ Mg, Mg $$\rightarrow$$ Al, Al $$\rightarrow$$ Si, Si $$\rightarrow$$ P, and P $$\rightarrow$$ S transitions. Theoretical results for $B(GT)$, $$\log ft$$ values, and half-lives are discussed and compared with the available experimental data. 

   more » « less
4. Methane Hydration‐Shell Structure and Fragility

   https://doi.org/10.1002/anie.201809372  

   Wu, Xiangen; Lu, Wanjun; Streacker, Louis M.; Ashbaugh, Henry S.; Ben‐Amotz, Dor (October 2018, Angewandte Chemie International Edition)

   Abstract The influence of oily molecules on the structure of liquid water is a question of importance to biology and geology and many other fields. Previous experimental, theoretical, and simulation studies of methane in liquid water have reached widely conflicting conclusions regarding the structure of hydrophobic hydration‐shells. Herein we address this question by performing Raman hydration‐shell vibrational spectroscopic measurements of methane in liquid water from −10 °C to 300 °C (at 30 MPa, along a path that parallels the liquid‐vapor coexistence curve). We show that, near ambient temperatures, methane's hydration‐shell is slightly more tetrahedral than pure water. Moreover, the hydration‐shell undergoes a crossover to a more disordered structure above ca. 85 °C. Comparisons with the crossover temperature of aqueous methanol (and other alcohols) reveal the stabilizing influence of an alcohol OH head‐group on hydrophobic hydration‐shell fragility. 

   more » « less
5. Valence shell electronically excited states of norbornadiene and quadricyclane

   https://doi.org/10.1063/5.0187707  

   Cooper, Joseph_C; Holland, David_M_P; Ingle, Rebecca_A; Bonanomi, Matteo; Faccialà, Davide; De_Oliveira, Nelson; Abid, Abdul_R; Bachmann, Julien; Bhattacharyya, Surjendu; Borne, Kurtis; et al (February 2024, The Journal of Chemical Physics)

   The absolute photoabsorption cross sections of norbornadiene (NBD) and quadricyclane (QC), two isomers with chemical formula C7H8 that are attracting much interest for solar energy storage applications, have been measured from threshold up to 10.8 eV using the Fourier transform spectrometer at the SOLEIL synchrotron radiation facility. The absorption spectrum of NBD exhibits some sharp structure associated with transitions into Rydberg states, superimposed on several broad bands attributable to valence excitations. Sharp structure, although less pronounced, also appears in the absorption spectrum of QC. Assignments have been proposed for some of the absorption bands using calculated vertical transition energies and oscillator strengths for the electronically excited states of NBD and QC. Natural transition orbitals indicate that some of the electronically excited states in NBD have a mixed Rydberg/valence character, whereas the first ten excited singlet states in QC are all predominantly Rydberg in the vertical region. In NBD, a comparison between the vibrational structure observed in the experimental 11B1–11A1 (3sa1 ← 5b1) band and that predicted by Franck–Condon and Herzberg–Teller modeling has necessitated a revision of the band origin and of the vibrational assignments proposed previously. Similar comparisons have encouraged a revision of the adiabatic first ionization energy of NBD. Simulations of the vibrational structure due to excitation from the 5b2 orbital in QC into 3p and 3d Rydberg states have allowed tentative assignments to be proposed for the complex structure observed in the absorption bands between ∼5.4 and 7.0 eV. 

   more » « less