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The diabatic dynamical diquark model is designed to unify diquark and molecular approaches for exotic hadrons by including the effects of dimeson thresholds on fundamental diquark-antidiquark states in order to form physical tetraquarks. We generalize this model by implementing the consequences of heavy-quark spin symmetry for each dimeson pair. We include the specific spin factors and mass differences associated with mesons related by this symmetry (such as $D,D^{*}$), both features being necessary for the systematic incorporation of effects beyond the static, heavy-source limit inherent to the (adiabatic) Born-Oppenheimer treatment. We obtain explicit interaction potentials for all $J=0$, 1, 2 states, along the way deriving unusual variants of Fierz reordering identities, and discuss the application of the potentials to specific physical states such as ${\chi }_{c1}\left(3872\right)$and $T_{c\overline{c}1}\left(3900\right)$. 

We generalize our recent analysis of hidden-strangeness tetraquarks within the dynamical diquark model from its adiabatic form (in which each state is described solely by a diquark-antidiquark potential) to its diabatic form (which incorporates effects of dihadron thresholds upon the states). We tabulate all relevant thresholds and compute the dihadron content of each predicted state. Our results produce no particular hidden-strange tetraquark candidate whose structure is dominated by dihadron structure, in contrast to the charm sector, where many exotic states are strongly associated with such thresholds: The hidden-strange states tend to remain compact and less influenced by dihadron thresholds. Multiple states above 2 GeV with peculiar decay properties, including $\varphi \left(2170\right)$, $f_2\left(2340\right)$, and $\eta \left(2370\right)$, continue to serve as excellent hidden-strange tetraquark candidates. 

Marine ice stream dynamics are sensitive to conditions at the grounding line and basal shear stress. Variations in subglacial hydrology have been implicated in ice stream speed-up and shutdown. To investigate the interplay between marine ice stream flow and subglacial hydrology, we couple models of a marine ice stream and a subglacial drainage system. The coupled system evolves dynamically due to a positive feedback between ice flow, heat dissipation at the ice stream bed, and basal lubrication. Our results show that, depending on the hydraulic conductivity of the bed, distinct dynamic regimes can be identified. These regimes include steady streaming, hydraulically controlled oscillations, and thermally controlled oscillations. Periodic fast flow can be initiated by activation waves travelling upstream or downstream or quasi-simultaneously everywhere. Different dynamical regimes are characterized by large differences in grounded ice volume, even under modest changes of grounding line positions. These results imply a strong dependence of marine ice sheet dynamics on evolving hydrological conditions at the bed and highlight the importance of a better understanding of subglacial hydrology. 

The dynamical diquark model describes multiquark exotic hadrons in terms of diquark components nucleated by heavy quarks and successfully explains multiple features of hidden-charm and hidden-bottom exotics. Here, we apply the model to the marginally heavy case of hidden-strange states to probe whether mesons near 2 GeV with peculiar properties, such as $\varphi \left(2170\right)$, $f_2\left(2340\right)$, and $X\left(2370\right)$, are possible tetraquark candidates. We calculate spin-multiplet average masses using potentials obtained through lattice simulations and quark models, and we also describe the detailed spectra of the expected multiplets as a diagnostic to discern the nature of future hadrons likely to be discovered in this mass region by experiments at facilities such as BESIII, JLab, and the EIC. 

Using the diabatic formalism, a rigorous generalization of the Born-Oppenheimer approximation, we study the effects of introducing simple meson-meson molecular potentials to an established diquark model for tetraquark states, and calculate mixed bound states composed of both diquark-antidiquark and meson-meson molecular components.We examine the behavior of properties of the states as one varies the parameters of the dimeson potential, and find that significant regions of parameter space occur in which one may produce mass eigenstates exactly matching the specific examples of χc1 and χc0. We also find regions in which a pure dimeson molecular state emerges, and study the same state properties in such cases. 

ABSTRACT D-glu is a key component of peptidoglycan (PG) and is essential for growth in most bacteria. To assess constraints on PG evolution and bacterial requirements for D-glu, we sought to artificially evolve PG biosynthesis, leading to either replacement of D-glu in the PG peptide or alternative pathways to D-glu incorporation. We previously found that suppression of D-glu auxotrophy in amurI racDmutant ofVibrio fischerigrown on lysogeny broth salts (LBS) medium was rare but could be accomplished by mutation ofbsrF, with restoration of wild-type PG structure. Here, we selected nine additional prototrophic suppressors of the samemurI racDmutant from 10¹⁰colony-forming units (CFU) plated on LBS supplemented with ~2.7 mM D-gln. Each suppressor had a mutation ingltS, which encodes a putative sodium:glutamate symporter. Increased copy numbers of mutantgltSalleles enabled growth on unsupplemented LBS and resulted in PG containing D-glu. Examination of media components suggests that D-gln supplementation had inadvertently added ~14 μM D-glu, and that LBS itself contains ~1.4 μM D-glu. The mutations ingltSenabled growth with similarly low D-glu concentrations, but also increased sensitivity to homocysteic acid, suggesting more promiscuous transport. Surprisingly, we discovered that expression of mutantgltSin the auxotroph leads to incorporation of lysine into PG, in addition to canonical D-glu. When seawater is supplemented with D-glu, thisV. fischerimutant still colonizedEuprymna scolopesand triggered PG-induced morphogenesis. Our results shed light on glutamate transport, highlight trade-offs in GltS structure and function, and reveal an unusual PG modification.IMPORTANCED-glu is an important building block in the peptidoglycan (PG) component of the bacterial cell wall, and its endogenous production is considered essential in most bacteria, even when grown in complex media. InVibrio fischeri,in transexpression of mutant GltS symporters allows D-glu auxotrophic strains to grow on lysogeny broth salts (LBS) medium without exogenous D-glu, although there is a fitness trade-off of increased sensitivity to homocysteic acid. Our finding that LBS contains sufficient D-glu to support robust growth highlights the undervalued importance of D-amino acid transport and the ubiquity of D-amino acids. Moreover, the discovery of D-lysine in the PG peptide is an unusual PG modification that warrants further study. 

Using the diabatic formalism, which generalizes the adiabatic approximation in the Born-Oppen-heimer formalism, we apply well-known Hamiltonian methods to calculate the effect of open di-meson thresholds that lie well below the mass of elementary $c\overline{c}q{\overline{q}}^{\prime }$, $c\overline{c}s\overline{s}$, and $c\overline{c}q\overline{s}$tetraquark bound states. We compute the resulting mass shifts for these states, as well as their decay widths to the corresponding meson pairs. Each mass eigenstate, originally produced using a bound-state approximation under the diabatic formalism, consists of an admixture of a compact diquark-antidiquark configuration (an eigenstate of the original dynamical diquark model) with an extended di-meson configuration induced by the nearest threshold. We compare our results with those from our recent work that employs a scattering formalism, and find a great deal of agreement, but also comment upon interesting discrepancies between the two approaches. Published by the American Physical Society2024