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Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of −3.0 ± 0.4 nN and −330 ± 43 aJ (10 −18  J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions.

The objective of this study was to compare the relative impact of humic and non-humic natural organic matter (NOM) on the aggregation behaviors of engineered TiO₂nanoparticles (nano-TiO₂). After exposure of nano-TiO₂to varying concentrations of Suwannee River fulvic acid (SRFA) and Bacillus subtilis exudate in high and low ionic strength (IS) solutions at pH 3 to pH 7.5, aggregation behaviors were evaluated via dynamic light scattering (DLS) measurements and sedimentation studies. Although pH, IS, and NOM concentration exerted strong controls on nano-TiO₂aggregation behaviors, suspensions exposed to either SRFA or bacterial exudate at normalized dissolved organic carbon (DOC) concentrations exhibited remarkably similar behaviors. In high IS systems, nano-TiO₂exposed to either SRFA or bacterial exudate sedimented rapidly, except in the presence of high NOM concentrations at pH 6 and 7.5. Low IS treatments exhibited a larger range of effects. In fact, relative to NOM-free controls, nano-TiO₂aggregates in SRFA and bacterial exudate exposures sedimented up to 14 times faster at pH 3 and up to 13 times slower at pH 7.5. Adsorption of organic molecules onto nano-TiO₂can enhance aggregation via colloidal bridging and/or charge neutralization, or with more complete surface coverage, can diminish aggregation via electrostatic repulsion and/or steric hindrance. Collectively, these data suggest that solution pH, IS, and NOM concentration, and to a lesser extent NOM origin, can control the fate and mobility of nano-TiO₂in geologic systems.

The objective of this study was to compare the relative impact of humic and non-humic natural organic matter (NOM) on the aggregation behaviors of engineered Ti[O.sub.2] nanoparticles (nano-Ti[O.sub.2]). After exposure of nano-Ti[O.sub.2] to varying concentrations of Suwannee River fulvic acid (SRFA) and Bacillus subtilis exudate in high and low ionic strength (IS) solutions at pH 3 to pH 7.5, aggregation behaviors were evaluated via dynamic light scattering (DLS) measurements and sedimentation studies. Although pH, IS, and NOM concentration exerted strong controls on nano-Ti[O.sub.2] aggregation behaviors, suspensions exposed to either SRFA or bacterial exudate at normalized dissolved organic carbon (DOC) concentrations exhibited remarkably similar behaviors. In high IS systems, nano-Ti[O.sub.2] exposed to either SRFA or bacterial exudate sedimented rapidly, except in the presence of high NOM concentrations at pH 6 and 7.5. Low IS treatments exhibited a larger range of effects. In fact, relative to NOM-free controls, nano-Ti[O.sub.2] aggregates in SRFA and bacterial exudate exposures sedimented up to 14 times faster at pH 3 and up to 13 times slower at pH 7.5. Adsorption of organic molecules onto nano-Ti[O.sub.2] can enhance aggregation via colloidal bridging and/or charge neutralization, or with more complete surface coverage, can diminish aggregation via electrostatic repulsion and/or steric hindrance. Collectively, these data suggest that solution pH, IS, and NOM concentration, and to a lesser extent NOM origin, can control the fate and mobility of nano-Ti[O.sub.2] in geologic systems. Keywords Bacterial exudate * Fulvic acid * Natural organic matter (NOM) * Nano-Ti[O.sub.2] * Aggregation * Fate and transport

X-ray absorption spectroscopy (XAS) and cadmium (Cd) isotherm experiments determine how Cd adsorbs to the surface of halophilic archaeon Halobacterium noricense. This archaeon, isolated from the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico could be involved with the transport of toxic metals stored in the transuranic waste in the salt mine. The isotherm experiments show that adsorption is relatively constant across the tolerable pH range for H. noricense. The XAS results indicate that Cd adsorption occurs predominately via a sulfur site, most likely sulfhydryl, with the same site dominating all measured pH values.

Environmental toxic metal contamination remediation and prevention is an ongoing issue. Graphene oxide is highly sorptive for many heavy metals over a wide pH range under different ionic strength conditions. We present x-ray absorption fine structure (XAFS) spectroscopy results investigating the binding environment of Pb(II), Cd(II) and U(VI) ions onto multi-layered graphene oxide (MLGO). Analysis indicates that the dominant sorption mechanism of Pb to MLGO changes as a function of pH, with increasing inner sphere contribution as pH increases. In contrast, the sorption mechanism of Cd to MLGO remains constant under the studied pH range. This adsorption mechanism is an electrostatic attraction between the hydrated Cd+2 ion and the MLGO surface. The U(VI), present as the uranyl ion, changes only subtly as a function of pH and is bound to the surface via an inner sphere bond. Knowledge of the binding mechanism for each metal is necessary to help in optimizing environmental remediation or prevention in filtration systems.

The objective of this study was to compare the relative impact of humic and non-humic natural organic matter (NOM) on the aggregation behaviors of engineered TiO sub(2) nanoparticles (nano-TiO sub(2)). After exposure of nano-TiO sub(2) to varying concentrations of Suwannee River fulvic acid (SRFA) and Bacillus subtilis exudate in high and low ionic strength (IS) solutions at pH 3 to pH 7.5, aggregation behaviors were evaluated via dynamic light scattering (DLS) measurements and sedimentation studies. Although pH, IS, and NOM concentration exerted strong controls on nano-TiO sub(2) aggregation behaviors, suspensions exposed to either SRFA or bacterial exudate at normalized dissolved organic carbon (DOC) concentrations exhibited remarkably similar behaviors. In high IS systems, nano-TiO sub(2) exposed to either SRFA or bacterial exudate sedimented rapidly, except in the presence of high NOM concentrations at pH 6 and 7.5. Low IS treatments exhibited a larger range of effects. In fact, relative to NOM-free controls, nano-TiO sub(2) aggregates in SRFA and bacterial exudate exposures sedimented up to 14 times faster at pH 3 and up to 13 times slower at pH 7.5. Adsorption of organic molecules onto nano-TiO sub(2) can enhance aggregation via colloidal bridging and/or charge neutralization, or with more complete surface coverage, can diminish aggregation via electrostatic repulsion and/or steric hindrance. Collectively, these data suggest that solution pH, IS, and NOM concentration, and to a lesser extent NOM origin, can control the fate and mobility of nano-TiO sub(2) in geologic systems.

During the last decade, renewed tensions between Russia and the West have inspired efforts to conceptualize current international relations in terms of a “new Cold War” (NCW). In this article, we explore the historical origins of the NCW analogy, its rise and decline in public discourse, and the terms of recent debates over its appropriateness. Whereas historical analogies are often employed to foster consensus, the NCW analogy is shown to be peculiarly divisive and double-edged—driving a wedge not only between proponents and their critics, but also between rival factions of proponents. Broadly, we suggest that analogies become double-edged, and potentially explosive, when they rely on divided memories of an earlier era.

Systemic adjuvant treatment might mitigate the high risk of disease recurrence in patients with resected stage IIC–III melanoma. The BRIM8 study evaluated adjuvant vemurafenib monotherapy in patients with resected, BRAFV600 mutation-positive melanoma. BRIM8 was a phase 3, international, double-blind, randomised, placebo-controlled study that enrolled 498 adults (aged ≥18 years) with histologically confirmed stage IIC–IIIA–IIIB (cohort 1) or stage IIIC (cohort 2) BRAFV600 mutation-positive melanoma that was fully resected. Patients were randomly assigned (1:1) by an interactive voice or web response system to receive twice-daily adjuvant oral vemurafenib 960 mg tablets or matching placebo for 52 weeks (13 × 28-day cycles). Randomisation was done by permuted blocks (block size 6) and was stratified by pathological stage and region in cohort 1 and by region in cohort 2. The investigators, patients, and sponsor were masked to treatment assignment. The primary endpoint was disease-free survival in the intention-to-treat population, evaluated separately in each cohort. Hierarchical analysis of cohort 2 before cohort 1 was prespecified. This trial is registered with ClinicalTrials.gov, number NCT01667419. The study enrolled 184 patients in cohort 2 (93 were assigned to vemurafenib and 91 to placebo) and 314 patients in cohort 1 (157 were assigned to vemurafenib and 157 to placebo). At the time of data cutoff (April 17, 2017), median study follow-up was 33·5 months (IQR 25·9–41·6) in cohort 2 and 30·8 months (25·5–40·7) in cohort 1. In cohort 2 (patients with stage IIIC disease), median disease-free survival was 23·1 months (95% CI 18·6–26·5) in the vemurafenib group versus 15·4 months (11·1–35·9) in the placebo group (hazard ratio [HR] 0·80, 95% CI 0·54–1·18; log-rank p=0·026). In cohort 1 (patients with stage IIC–IIIA–IIIB disease) median disease-free survival was not reached (95% CI not estimable) in the vemurafenib group versus 36·9 months (21·4–not estimable) in the placebo group (HR 0·54 [95% CI 0·37–0·78]; log-rank p=0·0010); however, the result was not significant because of the prespecified hierarchical prerequisite for the primary disease-free survival analysis of cohort 2 to show a significant disease-free survival benefit. Grade 3–4 adverse events occurred in 141 (57%) of 247 patients in the vemurafenib group and 37 (15%) of 247 patients in the placebo group. The most common grade 3–4 adverse events in the vemurafenib group were keratoacanthoma (24 [10%] of 247 patients), arthralgia (17 [7%]), squamous cell carcinoma (17 [7%]), rash (14 [6%]), and elevated alanine aminotransferase (14 [6%]), although all keratoacanthoma events and most squamous cell carcinoma events were by default graded as grade 3. In the placebo group, grade 3–4 adverse events did not exceed 2% for any of the reported terms. Serious adverse events were reported in 40 (16%) of 247 patients in the vemurafenib group and 25 (10%) of 247 patients in the placebo group. The most common serious adverse event was basal cell carcinoma, which was reported in eight (3%) patients in each group. One patient in the vemurafenib group of cohort 2 died 2 months after admission to hospital for grade 3 hypertension; however, this death was not considered to be related to the study drug. The primary endpoint of disease-free survival was not met in cohort 2, and therefore the analysis of cohort 1 showing a numerical benefit in disease-free survival with vemurafenib versus placebo in patients with resected stage IIC–IIIA–IIIB BRAFV600 mutation-positive melanoma must be considered exploratory only. 1 year of adjuvant vemurafenib was well tolerated, but might not be an optimal treatment regimen in this patient population. F Hoffman–La Roche Ltd.