Understanding the Salt-Dependent Outcome of Glycine Polymorphic Nucleation

The salt-dependent polymorphs of glycine crystals formed from bulk solutions have been a longstanding riddle. In this study, in order to shed fresh light, we studied the effects of seven common salts on primary nucleation of the metastable α-glycine and the stable γ-glycine. Our nucleation experiments and in-depth data analyses enabled us to reveal that (NH4)2SO4, NaCl and KNO3, in general, promote γ-glycine primary nucleation very significantly while simultaneously inhibiting α-glycine primary nucleation, thereby explaining why these three salts induce γ-glycine readily. In comparison, Ca(NO3)2 and MgSO4 also promote γ-glycine and inhibit α-glycine primary nucleation but not sufficiently to induce γ-glycine. More interestingly, Na2SO4 and K2SO4 promote not only γ-glycine but also α-glycine primary nucleation, which is unexpected and presents a rare case where a single additive promotes the nucleation of both polymorphs. As a result, the promoting effects of Na2SO4 and K2SO4 on γ-glycine do not enable γ-glycine nucleation to be more competitive than α-glycine nucleation, with γ-glycine failing to appear. These observations help us to better understand salt-governed glycine polymorphic selectivity.

Characterization of Wetting of Deep Silica Nanoholes by Aqueous Solutions Using ATR-FTIR

In advanced semiconductor manufacturing, deep hydrophilic nanoholes are found in various applications, which require a wet clean after patterning. In this work, we use an in-situ ATR-FTIR spectroscopy technique to characterize the wetting of nanoholes in a silica matrix by UPW and electrolyte solutions. Wetting was much slower than predicted by a numerical model, while temperature cycling evidenced the formation of unexpectedly stable gas pockets in the wetted nanoholes. Water structuring in the nanoholes was characterized by an analysis of the OH stretching peak. Besides, monitoring the dissolution of CO2 in the wetted nanoholes allowed to compare the diffusivity in the nano-confined solutions with that in bulk solutions. Our results strongly suggest that the gas pockets were stabilized by the decreased gas diffusivity resulting from water structuring.

Radial cutoffs and holographic entanglement

Tensor networks, $$ T\overline{T} $$ T T ¯ , and broader notions of a holographic principle all motivate the idea that some notion of gravitational holography should persist in the presence of a radial cutoff. But in the absence of time-reflection symmetry, the areas of Hubeny-Rangamani-Takayanagi surfaces anchored to the radial cutoff generally violate strong sub-additivity, even when the associated boundary regions are spacelike separated as defined by both bulk and boundary notions of causality. We thus propose an alternate definition of cutoff-holographic entropy using a restricted maximin prescription anchored to a codimension 2 cutoff surface. For bulk solutions that respect the null energy condition, we show that the resulting areas satisfy SSA, entanglement wedge nesting, and monogamy of mutual information in parallel with cutoff free results in AdS. These results hold even when the cutoff surface fails to be convex.

Multiscale Simulations of Polyzwitterions in Aqueous Bulk Solutions and Brush Array Configurations

Zwitterionic polymers are very promising candidate antifouling materials that exhibit high chemical stability as compared to polyethylene glycol-based systems. A count of simulation and experimental studies have emerged over the...

Students’ interpretation and use of graphical representations: insights afforded by modeling the varied population schema as a coordination class

Explanations of phenomena in chemistry are grounded in discussions of particulate-level behavior, but there are limitations to focusing on single particles, or as an extension, viewing a group of particles as displaying uniform behavior. More sophisticated models of physical processes evoke considerations related to the dynamic nature of bulk solutions, in which an ensemble of molecules exists with a distribution of values that vary with respect to different parameters (e.g., speed, kinetic energy, etc.). Viewing phenomena as a varied population instead of a homogenous solution has been identified as a foundational idea that is critical for reasoning in chemistry, but little work has investigated how students reason about these ideas and how instructors can support students in viewing phenomena as a distribution of states. In this qualitative study, during semi-structured interivews twelve undergraduate general chemistry students were provided with frequency distribution graphs (number of molecules vs. speed, number of molecules vs. kinetic energy) and were asked to provide explanations and make predictions. The design and analysis of this study was informed by coordination class theory, a model within the knowledge-in-pieces perspective of cognition that defines a concept as a combination of approaches for obtaining information (read-out strategies) and a cluster of knowledge elements used to draw conclusions (causal net). Framing the varied population schema as a coordination class, this work focuses on the interaction between features students attended to in distribution graphs and the ideas they discussed. Analysis indicates students have productive resources for reasoning about a varied population in general terms, but these ideas are not necessarily activated when interpreting graphs, as reflected in the students’ readout strategies. Moreover, we posit that one of the barriers toward interpreting distribution graphs was the inappropriate application of covariational reasoning. As a practical consideration, we encourage interested instructors to review the Appendix, which provides a short summary of the main findings and suggestions for practitioners.

Fast Surface Immobilization of Native Proteins through Metal-Free Amino-yne Click Bioconjugation

In this work, we use a spontaneous and catalyst-free amino-yne click bioconjugation to generate activated ethynyl group functionalized surfaces for fast immobilizing native proteins and cells. Biomolecules, such as bovine serum albumin (BSA), human IgG and peptide of C(RGDfK), could be covalently immobilized on the surfaces in as short as 30 min. Notably, the bioactivity of the anchored biomolecules remain intact, which is verified by efficiently capturing target antibodies and cells from the bulk solutions. This strategy represents an alternative for highly efficient surface biofunctionalization.

Fast Surface Immobilization of Native Proteins through Metal-Free Amino-yne Click Bioconjugation

In this work, we use a spontaneous and catalyst-free amino-yne click bioconjugation to generate activated ethynyl group functionalized surfaces for fast immobilizing native proteins and cells. Biomolecules, such as bovine serum albumin (BSA), human IgG and peptide of C(RGDfK), could be covalently immobilized on the surfaces in as short as 30 min. Notably, the bioactivity of the anchored biomolecules remain intact, which is verified by efficiently capturing target antibodies and cells from the bulk solutions. This strategy represents an alternative for highly efficient surface biofunctionalization.