Poly(vinyl alcohol)-based buffering membranes for isoelectric trapping separations

Isoelectric trapping (IET) in multicompartment electrolyzers (MCE) has been widely used for the electrophoretic separation of ampholytic compounds such as proteins. In IET, the separation occurs in the buffering membranes that form a step-wise pH gradient in the MCE. Typically, buffering membranes have been made by copolymerizing acrylamide with Immobiline compounds, which are acidic and basic acylamido buffers. One major problem, however, is that these buffering membranes are not stable when exposed to high concentrations of acid and base due to hydrolysis of the amide bonds. Poly(vinyl alcohol)-based, or PVA-based, membranes were made as an alternative to the polyacrylamide-based membranes since they provide more hydrolytic and mechanical stability. Four mid-pH, PVA-based buffering membranes that contain single ampholytes were synthesized. These buffering membranes were used to trap small molecular weight pI markers for up to three hours, and were also used in desalting experiments to remove strong electrolytes from a solution of ampholytes. Additionally, the membranes were used in IET experiments to separate mixtures of pI markers, and to fractionate the major proteins in chicken egg white. The membranes did not show any degradation when stored in 3 M NaOH for up to 6 months and were shown to tolerate current densities as high as 16 mA/cm2. In addition, six series of PVA-based membranes, whose pH values can be tuned over the 3 < pH < 10 range, were synthesized by covalently binding aminodicarboxylic acids, and monoamines or diamines to the PVA matrix. These tunable buffering membranes were used in trapping experiments to trap ampholytes for up to three hours, and in desalting experiments to remove strong electrolytes from a solution of ampholytes. These tunable buffering membranes were also used in IET experiments to separate proteins, some with pI values that differ by only 0.1 pH unit. The tunable buffering membranes did not show any signs of degradation when exposed to 3 M NaOH for up to 3 months, and could be used in IET experiments with current densities as high as 20 mA/cm2. These tunable buffering membranes are expected to broaden the application areas of isoelectric trapping separations

Long-Term Potentiation: One Kind or Many?

Do neurobiologists aim to discover natural kinds? I address this question in this chapter via a critical analysis of classification practices operative across the 43-year history of research on long-term potentiation (LTP). I argue that this 43-year history supports the idea that the structure of scientific practice surrounding LTP research has remained an obstacle to the discovery of natural kinds

High Tc superconductors: The scaling of Tc with the number of bound holes associated with charge transfer neutralizing the multivalence cations

It is observed that for the known high-T(sub c) Cu-, Tl-, and Bi-based superconductors, T(sub c) scales consistently with the number of bound holes per unit cell which arise from charge transfer excitations of frequency approximately = 3 x 10(exp 13) that neutralized the multivalence cations into diamagnetic states. The resulting holes are established on the oxygens. Extrapolation of this empirical fit in the up-temperature direction suggests a T(sub c) of about 220-230 K at a value of 25 holes/unit cell (approximately the maximum that can be materials-engineered into a high-T(sub c) K2MnF4 or triple Perovskite structure). In the down-temperature direction, the extrapolation gives a T(sub c) in the vicinity of 235 K for the Y-Ba-Cu-O system as well as the known maximum temperature of 23 K for low-T(sub c) materials shown by Nb3Ge. The approach is also consistent with the experimental findings that only multivalence ions which are diamagnetic in their atomic state (Cu, Tl, Bi, Pb, and Sb) associate with high-T(sub c) compounds

Functionalization of silver nanoparticles on membranes and its influence on biofouling

The aim of this project is modifying the attachment of silver nanoparticles (Ag-NPs) on water treatment membranes, such as cellulose acetate (CA), and to observe its effect towards biofouling. Biofouling results from the accumulation of live/dead microorganisms present in water on the membrane surface and pores, and it creates several performance problems such as clogging of pores, higher operating cost, higher pressure drop, etc. Minimizing this would be ideal to lower operating cost and save expensive materials. In this project, Pseudomonas Fluorescens Migula are used because this species generates extracellular polymeric substances (EPS). EPS produced from bacteria helps create a viable structural foundation for biofilm accumulation with densely packed matrices, which in turn fouls the polymeric membranes. In this study, Ag-NPs are added to CA membranes for biofouling minimization. A concern with combining Ag-NP with membranes is the leaching of nanoparticles. If the Ag-NPs are chemically attached to the membranes, it is believed that leaching can be prevented. Different methods of introducing the Ag-NPs to the membranes studied here will include physical blending, chemically-activated blending, and chemically-crosslinked blending

End-of-day Far-red Lighting with a Low Daily Light Integral Increases Stem Length But Does Not Promote Early Leaf Expansion for Petunia ×hybrida Seedlings

Greenhouse production of high-quality young annual bedding plants (plugs) at northern latitudes often requires supplemental lighting to compensate for a low natural daily light integral (DLI), but radiation interception by plugs is limited by a low leaf area index. Some species show an increase in leaf area in response to growth under a low ratio of red to far-red radiation (R:FR), and an early increase in leaf area may allow for more effective radiation capture by seedlings and a reduction in wasted radiation. Thus, the objective of this study was to examine the effects of end-of-day far-red (EOD-FR) radiation treatments varying in intensity, R:FR (600–700 nm/700–780 nm), and duration on early leaf expansion and plug quality for petunia (Petunia ×hybrida) ‘Wave Purple’ and ‘Dreams Midnight’. Seedlings were grown in 128-cell trays in a common greenhouse environment under a simulated winter DLI (∼5.3 mol·m−2·s−1) and received one of four EOD-FR treatments, control conditions (no EOD-FR or supplemental lighting), or supplemental lighting (target photosynthetic photon flux density of 70 μmol·m−2·s−1). The EOD-FR treatments were provided for 3 weeks on cotyledon emergence and included the following: 10 μmol·m−2·s−1 of far-red radiation for 30 minutes with a R:FR of ∼0.8 (EODFL), 10 or 20 μmol·m−2·s−1 of far-red radiation for 30 minutes with a R:FR of ∼0.15 (EOD10:30 and EOD20:30, respectively), or 20 μmol·m−2·s−1 of far-red radiation for 240 minutes with a R:FR of ∼0.15 (EOD20:240). Destructive data were collected 14 and 21 days after cotyledon emergence. Seedlings that received EOD-FR treatments did not show any increase in leaf area compared with control or supplemental lighting treatments. Stem length generally increased under EOD-FR treatments compared with supplemental lighting and control treatments; greater elongation was observed when the R:FR decreased from 0.8 to 0.15, and when treatment duration increased from 30 minutes to 240 minutes. However, at a R:FR of 0.15 and a treatment duration of 30 minutes, an increase in far-red radiation intensity from 10 to 20 μmol·m−2·s−1 did not promote further stem elongation resulting in similar stem lengths for both cultivars under EOD10:30 and EOD20:30. Results of this study indicate that under low DLIs, EOD-FR radiation applied in the first 3 weeks of seedling production does not promote early leaf area expansion, and generally decreases seedling quality for petunia. As responses to far-red radiation may vary based on study taxa, incident radiation, and DLI, future research examining EOD-FR–induced morphological changes is warranted

Parity nonconserving observables in thermal neutron capture on a proton

We calculate parity nonconserving observables in the processes where a neutron is captured on a proton at the threshold energy radiating a photon. Various potential models such as Paris, Bonn and Argonne $v18$ are used for the strong interactions, and the meson-exchange description is employed for the weak interactions between hadrons. The photon polarization $P_\gamma$ in the unpolarized neutron capture process and photon asymmetry $A_\gamma$ in the polarized neutron capture process are obtained in terms of the weak meson-nucleon coupling constants. $A_\gamma$ turns out to be basically insensitive to the employed strong interaction models and thus can be uniquely determined in terms of the weak coupling constants, but $P_\gamma$ depends significantly on the strong interaction models.Comment: 13 pages, 11 eps figure

Prediction and Topological Models in Neuroscience

In the last two decades, philosophy of neuroscience has predominantly focused on explanation. Indeed, it has been argued that mechanistic models are the standards of explanatory success in neuroscience over, among other things, topological models. However, explanatory power is only one virtue of a scientific model. Another is its predictive power. Unfortunately, the notion of prediction has received comparatively little attention in the philosophy of neuroscience, in part because predictions seem disconnected from interventions. In contrast, we argue that topological predictions can and do guide interventions in science, both inside and outside of neuroscience. Topological models allow researchers to predict many phenomena, including diseases, treatment outcomes, aging, and cognition, among others. Moreover, we argue that these predictions also offer strategies for useful interventions. Topology-based predictions play this role regardless of whether they do or can receive a mechanistic interpretation. We conclude by making a case for philosophers to focus on prediction in neuroscience in addition to explanation alone