Density Matrix Renormalization Group Study of One-Dimensional Acoustic Phonons

We study the application of the density matrix renormalization group (DMRG) to systems with one-dimensional acoustic phonons. We show how the use of a local oscillator basis circumvents the difficulties with the long-range interactions generated in real space using the normal phonon basis. When applied to a harmonic atomic chain, we find excellent agreement with the exact solution even when using a modest number of oscillator and block states (a few times ten). We discuss the use of this algorithm in more complex cases and point out its value when other techniques are deficient.Comment: 12 pages. To be published in PRB rapid co

Equity and excellence in English language education in the USA: A literature review from the 1960s to 2020s

This study examined the trends in English language education (ELE) using a literature review from the 1960s to the 2020s as a research method. After reading the 1012 journal article abstracts, 210 articles emerged using the 37 keywords, which were supposed to embrace racial and linguistic equity. After multiple iterations of reading and open coding these abstracts, thirty-two articles were selected for the final analysis. One research question guided this study, “What were the emerging trends of PK-12 ELE in the USA in terms of equity and excellence from the 1960s to the 2020s?” Three phases were identified: Phase 1 (1968-1999) on remedial service; Phase 2 (2000-2007) on test accountability; and Phase 3 (2008-2020) on asset-based ELE. We integrated Feiman-Nemser’s central tasks into the four themes: 1) gaining EBLs' funds of knowledge (FoK), 2) enacting EBLs' racial, linguistic, and cultural repertoires, 3) forming teacher beliefs, and 4) deepening knowledge of the curriculum. The findings revealed shifts in three phases under each theme: from assimilating to the target language and culture and devaluing EBLs' assets in Phase 1 to interweaving EBLs’ FoK but with racialized attitude towards EBLs in Phase 2 and valuing EBLs’ FoK as assets, seeing them as ‘language architect’, and integrating translanguaging and resisting raciolinguistic ideologies into ELE in Phase 3

Specific Ions Modulate Diffusion Dynamics of Hydration Water on Lipid Membrane Surfaces

Effects of specific ions on the local translational diffusion of water near large hydrophilic lipid vesicle surfaces were measured by Overhauser dynamic nuclear polarization (ODNP). ODNP relies on an unpaired electron spin-containing probe located at molecular or surface sites to report on the dynamics of water protons within ∼10 Å from the spin probe, which give rise to spectral densities for electron–proton cross-relaxation processes in the 10 GHz regime. This pushes nuclear magnetic resonance relaxometry to more than an order of magnitude higher frequencies than conventionally feasible, permitting the measurement of water moving with picosecond to subnanosecond correlation times. Diffusion of water within ∼10 Å of, i.e., up to ∼3 water layers around the spin probes located on hydrophilic lipid vesicle surfaces is ∼5 times retarded compared to the bulk water translational diffusion. This directly reflects on the activation barrier for surface water diffusion, i.e., how tightly water is bound to the hydrophilic surface and surrounding waters. We find this value to be modulated by the presence of specific ions in solution, with its order following the known Hofmeister series. While a molecular description of how ions affect the hydration structure at the hydrophilic surface remains to be answered, the finding that Hofmeister ions directly modulate the surface water diffusivity implies that the strength of the hydrogen bond network of surface hydration water is directly modulated on hydrophilic surfaces

Correlating steric hydration forces with water dynamics through surface force and diffusion NMR measurements in a lipid-DMSO-H2O system.

Dimethyl sulfoxide (DMSO) is a common solvent and biological additive possessing well-known utility in cellular cryoprotection and lipid membrane permeabilization, but the governing mechanisms at membrane interfaces remain poorly understood. Many studies have focused on DMSO-lipid interactions and the subsequent effects on membrane-phase behavior, but explanations often rely on qualitative notions of DMSO-induced dehydration of lipid head groups. In this work, surface forces measurements between gel-phase dipalmitoylphosphatidylcholine membranes in DMSO-water mixtures quantify the hydration- and solvation-length scales with angstrom resolution as a function of DMSO concentration from 0 mol% to 20 mol%. DMSO causes a drastic decrease in the range of the steric hydration repulsion, leading to an increase in adhesion at a much-reduced intermembrane distance. Pulsed field gradient NMR of the phosphatidylcholine (PC) head group analogs, dimethyl phosphate and tetramethylammonium ions, shows that the ion hydrodynamic radius decreases with increasing DMSO concentration up to 10 mol% DMSO. The complementary measurements indicate that, at concentrations below 10 mol%, the primary effect of DMSO is to decrease the solvated volume of the PC head group and that, from 10 mol% to 20 mol%, DMSO acts to gradually collapse head groups down onto the surface and suppress their thermal motion. This work shows a connection between surface forces, head group conformation and dynamics, and surface water diffusion, with important implications for soft matter and colloidal systems

Correlating steric hydration forces with water dynamics through surface force and diffusion NMR measurements in a lipid-DMSO-H2O system.

Dimethyl sulfoxide (DMSO) is a common solvent and biological additive possessing well-known utility in cellular cryoprotection and lipid membrane permeabilization, but the governing mechanisms at membrane interfaces remain poorly understood. Many studies have focused on DMSO-lipid interactions and the subsequent effects on membrane-phase behavior, but explanations often rely on qualitative notions of DMSO-induced dehydration of lipid head groups. In this work, surface forces measurements between gel-phase dipalmitoylphosphatidylcholine membranes in DMSO-water mixtures quantify the hydration- and solvation-length scales with angstrom resolution as a function of DMSO concentration from 0 mol% to 20 mol%. DMSO causes a drastic decrease in the range of the steric hydration repulsion, leading to an increase in adhesion at a much-reduced intermembrane distance. Pulsed field gradient NMR of the phosphatidylcholine (PC) head group analogs, dimethyl phosphate and tetramethylammonium ions, shows that the ion hydrodynamic radius decreases with increasing DMSO concentration up to 10 mol% DMSO. The complementary measurements indicate that, at concentrations below 10 mol%, the primary effect of DMSO is to decrease the solvated volume of the PC head group and that, from 10 mol% to 20 mol%, DMSO acts to gradually collapse head groups down onto the surface and suppress their thermal motion. This work shows a connection between surface forces, head group conformation and dynamics, and surface water diffusion, with important implications for soft matter and colloidal systems

Broad-spectrum neutralization of avian influenza viruses by sialylated human milk oligosaccharides: in vivo assessment of 3′-sialyllactose against H9N2 in chickens

Abstract Two sialylated human milk oligosaccharides (SHMOs) 3′-sialyllactose (3′-SL) and 6′-sialyllactose (6′-SL) were accessed for their possible antiviral activity against six different subtypes of thirteen avian influenza (AI) viruses in vitro. 3′-SL exhibited promising antiviral activity against almost all subtypes of tested AI viruses in hemagglutination inhibition assay, whereas 6′-SL showed activity against few selected H1N1, H1N2, and H3N2 subtype strains. 3′-SL has minimum inhibitory concentration values of 15.62 mM or less in more than half of the viruses examined. 3′-SL also showed effective inactivation of H9N2 Korea isolate (A/Chicken/Korea/MS96/1996) at 12.5 mM concentration in Madin Darby Canine Kidney (MDCK) cell line. Thus, 3′-SL was further studied for in vivo study against H9N2 virus in pathogen free chicken experiment models. In vivo study exhibited improved clinical symptoms on H9N2 infected chickens when treated with 3′-SL. Moreover, treating chickens with 3′-SL resulted in complete elimination of H9N2 viruses within 24 h of virus infection (0.8 HAU of H9N2). Indirect ELISA assay confirmed complete wash-out of H9N2 viruses from the colon after neutralization by 3′-SL without entering the blood stream. These in vivo results open up possible applications of 3′-SL for the prevention of AI virus infections in birds by a simple cleansing mechanism

Correlating steric-hydration forces with water dynamics through surface force and diffusion NMR measurements in a lipid-DMSO-H2O system

Dimethyl sulfoxide (DMSO) is a common solvent and biological additive possessing well-known utility in cellular cryoprotection and lipid membrane permeabilization, but the governing mechanisms at membrane interfaces remain poorly understood. Many studies have focused on DMSO-lipid interactions and the subsequent effects on membrane-phase behavior, but explanations often rely on qualitative notions of DMSO-induced dehydration of lipid head groups. In this work, surface forces measurements between gel-phase dipalmitoylphosphatidylcholine membranes in DMSO-water mixtures quantify the hydration-and solvation-length scales with angstrom resolution as a function of DMSO concentration from 0 mol% to 20 mol%. DMSO causes a drastic decrease in the range of the steric hydration repulsion, leading to an increase in adhesion at a much-reduced intermembrane distance. Pulsed field gradient NMR of the phosphatidylcholine (PC) head group analogs, dimethyl phosphate and tetramethylammonium ions, shows that the ion hydrodynamic radius decreases with increasing DMSO concentration up to 10 mol% DMSO. The complementary measurements indicate that, at concentrations below 10 mol%, the primary effect of DMSO is to decrease the solvated volume of the PC head group and that, from 10 mol% to 20 mol%, DMSO acts to gradually collapse head groups down onto the surface and suppress their thermal motion. This work shows a connection between surface forces, head group conformation and dynamics, and surface water diffusion, with important implications for soft matter and colloidal systems.close0