Abstract Human cases of avian influenza virus (AIV) infections are associated with an age-specific disease burden. As the influenza virus N2 neuraminidase (NA) gene was introduced from avian sources ...during the 1957 pandemic, we investigate the reactivity of N2 antibodies against A(H9N2) AIVs. Serosurvey of healthy individuals reveal the highest rates of AIV N2 antibodies in individuals aged ≥65 years. Exposure to the 1968 pandemic N2, but not recent N2, protected against A(H9N2) AIV challenge in female mice. In some older adults, infection with contemporary A(H3N2) virus could recall cross-reactive AIV NA antibodies, showing discernable human- or avian-NA type reactivity. Individuals born before 1957 have higher anti-AIV N2 titers compared to those born between 1957 and 1968. The anti-AIV N2 antibodies titers correlate with antibody titers to the 1957 N2, suggesting that exposure to the A(H2N2) virus contribute to this reactivity. These findings underscore the critical role of neuraminidase immunity in zoonotic and pandemic influenza risk assessment.
Many locations around the world have used real-time estimates of the time-varying effective reproductive number (Formula: see text) of COVID-19 to provide evidence of transmission intensity to inform ...control strategies. Estimates of Formula: see text are typically based on statistical models applied to case counts and typically suffer lags of more than a week because of the latent period and reporting delays. Noting that viral loads tend to decline over time since illness onset, analysis of the distribution of viral loads among confirmed cases can provide insights into epidemic trajectory. Here, we analyzed viral load data on confirmed cases during two local epidemics in Hong Kong, identifying a strong correlation between temporal changes in the distribution of viral loads (measured by RT-qPCR cycle threshold values) and estimates of Formula: see text based on case counts. We demonstrate that cycle threshold values could be used to improve real-time Formula: see text estimation, enabling more timely tracking of epidemic dynamics.
The biofouling propensity and cleaning effectiveness were evaluated for a new generation of polyamide thin-film composite (PA-TFC) membranes that are surface nano-structured (SNS) with terminally ...anchored hydrophilic polymer chains. The SNS-PA-TFC membranes were formed via surface graft polymerization onto the surface of polyamide base membranes previously activated via surface treatment with atmospheric pressure plasma. Poly(methacrylic acid) (PMMA) and polyacrylamide (PAAm) SNS-PA-TFC membranes were synthesized and evaluated with respect to their biofouling resistance using secondary wastewater from a municipal wastewater treatment (MWT) plant. Biofouling resistance and cleaning effectiveness were quantified via flux decline measurements in addition to imaging of the biofouled membranes before and after DI water and chemical (Na2·EDTA) cleaning. Increased biofouling resistance was highest for the PMAA-SNS-PA-TFC membrane being a factor of 4.2 greater than for the commercial membrane of about the same salt rejection used in the MWT plant. Moreover, permeability recovery for the PMAA-SNS-PA-TFC membrane was higher by factors of up to ~1.2 relative to the reference commercial membrane upon cleaning with DI water and more aggressive chemical cleaning at high pressure. The present evaluation of the SNS-PA-TFC membranes suggests that biofouling resistance and cleaning effectiveness of RO membranes can be enhanced via hydrophilic brush layers.
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•RO membrane surface nanostructured with a hydrophilic polymer brush layer.•Reduced membrane biofouling propensity.•Improved membrane cleaning effectiveness.•Increased membrane permeability.
The kinetics of gypsum surface crystallization on polymeric surfaces was studied using a quartz crystal microbalance demonstrating the importance of both surface topography and chemistry on crystal ...nucleation and growth.
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► Gypsum crystallization on polymeric surfaces was evaluated via QCM measurements. ► Gypsum mass density, for same surfaces polarity, was lower for smoother surfaces. ► Surface chemical functionality impacts surface crystallization.
Surface crystallization of calcium sulfate dihydrate (gypsum) on a series of polymeric surfaces was studied using a quartz microbalance system. Polyelectrolyte multilayer films (positively and negatively charged surfaces) were formed on the quartz crystal microbalance (QCM) sensors utilizing a layer-by-layer spin-assembly method. The kinetics of gypsum surface crystallization was quantified in terms of the evolution of gypsum mineral scale on the different surfaces. For comparison mineral scaling was also evaluated on silica and polyamide surfaces. For surfaces of the same charge polarity (+/-), the mass density of gypsum scale was lower (PSS
<
PAA, PEI
<
PAH) for smoother surfaces. The extent of surface mineral scaling (quantified in terms of both mass density and aerial coverage) were the combined result of the rate of nucleation and crystal growth kinetics. Although aerial scale coverage correlated with the crystal mass density, the crystal number density did not correlate with the extent of surface scaling. Surface crystal size, morphology and crystal number density varied significantly at similar roughness levels, suggesting that surface chemical functionality may also affect surface crystallization. The present results suggest that there is merit in exploring methods for mitigation of mineral scaling on polymeric surfaces via alteration of surface both surface topography and chemistry. In this regards, an expanded systematic study is needed in order to quantitatively clarify the interplay between the above two factors in controlling surface crystallization.
► Gypsum scaling of polyamide membranes of varying topography was evaluated via QCM. ► Polyamide surfaces were interfacially polymerized onto modified QCM sensors. ► Surface scaling increases ...nonlinearly with increased surface roughness. ► Crystal size and shape are affected by surface topography (micro- and nano-scale). ► Presence and separation of “hills” and “alleys” impacted surface crystallization.
The mineral scaling propensity of aromatic polyamide membrane surfaces was evaluated for surfaces ranging in roughness from about 1 to 94
nm, surface feature heights ranging from a few nanometers to as high as 400–450
nm and average peak separation of ∼140
nm to 2
μm. The polyamide surfaces were interfacially polymerized onto quartz crystal microbalance (QCM) sensors and silicon wafer substrates which were previously structured with a polyelectrolyte film formed by a layer-by-layer self-assembly method. Mineral scaling was quantified via QCM measurements of the time evolution of surface crystallization along with SEM and AFM surface characterization. Crystal surface mass density and rate of surface crystallization increased with increasing surface roughness. However, surface scaling propensity was also significantly impacted by the details of surface topography revealing fewer but larger crystals on rough surfaces that possessed large features with large separation distances. It is hypothesized that the separation distance between features and feature heights (dictating the geometry of surface “valleys”), for a given surface roughness, could affect the availability of surface nucleation sites as well as constrain growth of crystals within surface valleys.
Surface nano-structuring of polyamide desalination membrane with a hydrophilic poly(methacrylic acid) was shown to reduce the membrane mineral scaling propensity as demonstrated with calcium sulfate ...dihydrate (gypsum). A two-step approach was employed, whereby the active polyamide (PA) layer of a thin-film composite (TFC) synthesized membrane was activated with impinging atmospheric plasma, followed by a solution free-radical graft polymerization (FRGP) of a water soluble methacrylic acid (MAA) monomer, at 60
°C and initial monomer concentration of 5–20% (v/v), onto the surface of the PA-TFC membrane. The approach of creating a layer of end-grafted poly(methacrylic acid) (PMAA) surface chains was first developed and evaluated using a surrogate polyamide membrane layer interfacially polymerized onto a thin poly(ethyleneimine) (PEI) film coated onto a silicon wafer. The resulting PMAA–PA-PEI–Si surrogate membrane surface was hydrophilic with a water contact angle range of 10–17°. Structuring of the PA-TFC membrane at equivalent FRGP reaction conditions resulted in membranes of higher permeability (by a factor of 1.3–2.26) relative to a commercial RO membrane of a similar surface roughness (∼70
nm) and salt rejection. Flux tests of membrane mineral scaling demonstrated that membrane mineral scaling propensity can be measurably reduced, relative to commercial membrane of the same salt rejection, while yielding equivalent or higher water permeability. The onset time for gypsum scaling for the optimal membrane surface (prepared at 10% (v/v) initial MAA concentration) was retarded by a factor of 2–5 relative to the commercial RO membrane. Current work is ongoing to further optimize the surface structure in order to increasing scaling resistance and assess the impact of surface structuring on nucleation of mineral salt crystals.
We report here a simple method to generate ordered nanocavity arrays on a Si wafer and use it in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). A close-packed SiO2 ...nanosphere array was first deposited on a low-resistivity Si wafer using a convective self-assembly method. The nanoparticle array was then used as a mask in a reactive ion etching (RIE) process to selectively remove portions of the Si surface. Subsequent sonication removed those physically adsorbed SiO2 nanoparticles and exposed an ordered nanocavity array underneath. The importance of this approach is its capability of systematically varying surface geometries to achieve desired features, which makes detailed studies of the impacts of surface features on the desorption/ionization mechanism feasible. We demonstrated that the in-plane width and out-of-plane depth of the cavities were adjustable by varying etching times, and the intercavity spacing was controllable by varying the number of particle layers deposited. MS detection of small peptides on these substrates showed comparable sensitivity to conventional porous Si substrates (DIOS, desorption/ionization on porous silicon). The desorption and ionization efficiency of these roughened surfaces exhibited a nonmonotonic relationship to the increased total surface area. Several possible factors contributing to the observed phenomenon are speculated upon. The application of this arrayed surface in metabolite detection of Arabidopsis thaliana root extracts is also demonstrated.
Our current natural product program utilizes new actinomycetes originating from unexplored and underexplored ecological niches, employing cytotoxicity against a selected panel of cancer cell lines as ...the preliminary screen to identify hit strains for natural product dereplication, followed by mechanism-based assays of the purified natural products to discover potential anticancer drug leads. Three new linear polyketides, actinopolysporins A (1), B (2), and C (3), along with the known antineoplastic antibiotic tubercidin (4), were isolated from the halophilic actinomycete Actinopolyspora erythraea YIM 90600, and the structures of the new compounds were elucidated on the basis of spectroscopic data interpretation. All four compounds were assayed for their ability to stabilize the tumor suppressor programmed cell death protein 4 (Pdcd4), which is known to antagonize critical events in oncogenic pathways. Only 4 significantly inhibited proteasomal degradation of a model Pdcd4–luciferase fusion protein, with an IC50 of 0.88 ± 0.09 μM, unveiling a novel biological activity for this well-studied natural product.
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