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•A new DGA-PAMAM-SDB chelating resin has been synthesized for actinide sorption.•Maximum sorption capacities of resin are 682 and 544.2mgg−1for U(VI) and Th(IV).•DGA-PAMAM-SDB ...chelating resin could be regenerated and reused.•DFT calculation of actinides interaction with resin corroborates the experimental.•Resin is effective for sorption of actinides from both aqueous and HNO3 medium.
A novel chelating resin obtained via growth of PAMAM dendron on surface of styrene divinyl benzene resin beads, followed by diglycolamic acid functionalization of the dendrimer terminal. Batch experiments were conducted to study the effects of pH, nitric acid concentration, amount of adsorbent, shaking time, initial metal ion concentration and temperature on U(VI) and Th(IV) adsorption efficiency. Diglycolamic acid terminated PAMAM dendrimer functionalized styrene divinylbenzene chelating resin (DGA-PAMAM-SDB) is found to be an efficient candidate for the removal of U(VI) and Th(IV) ions from aqueous (pH >4) and nitric acid media (>3M). The sorption equilibrium could be reached within 60min, and the experimental data fits with pseudo-second-order model. Langmuir sorption isotherm model correlates well with sorption equilibrium data. The maximum U(VI) and Th(IV) sorption capacity onto DGA-PAMAMG5-SDB was estimated to be about 682 and 544.2mgg−1 respectively at 25°C. The interaction of actinides and chelating resin is reversible and hence, the resin can be regenerated and reused. DFT calculation on the interaction of U(VI) and Th(IV) ions with chelating resin validates the experimental findings.
Despite increasing regulatory attention and literature linking roadside air pollution to health outcomes, studies on near roadway air quality have not yet been well synthesized. We employ data ...collected from 1978 as reported in 41 roadside monitoring studies, encompassing more than 700 air pollutant concentration measurements, published as of June 2008. Two types of normalization, background and edge-of-road, were applied to the observed concentrations. Local regression models were specified to the concentration-distance relationship and analysis of variance was used to determine the statistical significance of trends. Using an edge-of-road normalization, almost all pollutants decay to background by 115−570 m from the edge of road; using the more standard background normalization, almost all pollutants decay to background by 160−570 m from the edge of road. Differences between the normalization methods arose due to the likely bias inherent in background normalization, since some reported background values tend to underpredict (be lower than) actual background. Changes in pollutant concentrations with increasing distance from the road fell into one of three groups: at least a 50% decrease in peak/edge-of-road concentration by 150 m, followed by consistent but gradual decay toward background (e.g., carbon monoxide, some ultrafine particulate matter number concentrations); consistent decay or change over the entire distance range (e.g., benzene, nitrogen dioxide); or no trend with distance (e.g., particulate matter mass concentrations).
Abstract Publicly available electric vehicle (EV) infrastructure is pivotal for the United States EV transition by 2030. Existing infrastructure lacks equitably distribution to low-income and ...underrepresented communities, impeding mass adoption. Our study, utilizing 2021 micro-level data from 121 million United States households, comprehensively examines income and racial disparities in EV infrastructure accessibility. Our analysis of national averages indicates that lower-income groups face less accessibility to public EV infrastructure in both urban and rural geographies. Black households experience less rural accessibility, but greater urban accessibility compared to White households conditioning on income. However, our localized analysis uncovers significant variations in accessibility gaps among counties, rural and urban settings, and dwelling types. While Black households experience greater urban accessibility nationally, a closer look at the county level reveals diminishing advantages. This study identifies areas with pronounced inequality and urgent needs for enhanced accessibility, emphasizing the necessity for tailored solutions by local governments to enhance equitable access to EV infrastructure.
The Goel-Harms atlantoaxial screw fixation technique for the treatment of atlantoaxial instability and unstable odontoid fractures is reliable and reproducible for a variety of anatomies. The ...drawbacks of the technique are the potential for significant bleeding from the C2 nerve root venous plexus and the risks associated with posterior midline exposure and retraction, such as pain and wound complications. The authors developed a minimally invasive surgical (MIS) modification of the Goel-Harms technique using intra-articular grafting to facilitate placement of percutaneous lateral mass and pars screws with extended tabs for minimally invasive subfascial rod placement. The objective of this study was to present the authors' first series of 5 patients undergoing minimally invasive modification in comparison with 51 patients undergoing open atlantoaxial fusion.
A retrospectiveanalysis of patient comorbid conditions, blood loss, length of surgery, and length of stay was performed on patients undergoing Goel-Harms instrumented fusion (GHIF) for unstable odontoid fractures performed between 2016 and 2021.
Patients undergoing the minimally invasive procedure showed significantly less blood loss than those undergoing the open atlantoaxial fusion procedure, with a median blood loss of 30 ml compared with 150 ml using the open technique (p < 0.01). The patients showed no significant differences in length of stay (2 days for MIS vs 4 days for open atlantoaxial fusion, p = 0.25). There were no significant differences in length of surgery for MIS, but a possible trend toward increased operative duration (234 vs 151 minutes, p = 0.112).
In this small pilot study, it was shown that MIS-GHIF can be performed with decreased blood loss in atlantoaxial instability and odontoid fractures. This technique may allow for greater and safer application of the procedure in the elderly and infirm.
Isotope effect is a quantum mechanical phenomenon and thus poses a challenge for the separation of isotopes of an element of interest, especially for heavy elements. Isotopic fractionation of zinc is ...also quite difficult and challenging but is necessitated due to various applications of its isotopes ranging from nuclear medicine to nuclear power reactors. Here, we developed the dibenzo-18-crown-6 (DB18C6) ether-functionalized poly(methacrylic acid) (PMA) resin by exploiting the ion and isotope recognition ability of the crown ether using DFT/MD simulations followed by experiments for isotopic fractionation of zinc. The PMADB18C6 adsorbent was prepared and suitably characterized. Both computational and experimental findings demonstrate that the adsorption and isotope separation of zinc with PMADB18C6 are due to the molecular recognition effect of the "O" dipole of the crown ether. Furthermore, both MD simulations and experiments suggest Langmuir type adsorption isotherms. The adsorption of Zn
2+
ions on the PMA resin is predicted to be endothermic, whereas it is exothermic on the PMADB18C6 resin, as revealed from the experimentally observed enthalpy change. A small scale fixed bed column study was demonstrated to test the scale-up application. The values of the experimental separation factors: 1.0013 for 66/64 and 1.0027 for 68/64 confirm the computationally predicted results of 1.00088 and 1.0010, respectively, thus establishing the combined strength of the theory and experiments for the identification of efficient fractionating agents for a complex quantum isotope effect which eventually helps in planning further experiments in view of medicinal and technological applications of zinc isotopes.
Isotope effect is a quantum mechanical phenomenon and thus poses a challenge for the separation of isotopes of an element of interest, especially for heavy elements.
The isolation of Am(
iii
) ion from Ln(
iii
) ions is very crucial for the safe disposal of nuclear wastes and thus, studies are being continuously pursued to accomplish this goal. In view of this, ...herein, a new conformationally rigid bitopic ligand,
N
,
N
,
N
′,
N
′-tetra(2-ethylhexyl)piperazine-di-methylenecarboxamide (PIPDA) has been synthesized and studied for the separation of Am(
iii
) from Ln(
iii
) ions. The effect of structural rigidification on the selectivity of Am(
iii
) over Ln(
iii
) was compared with an open chain flexible compound, namely,
N
,
N
,
N
′,
N
′-tetra(2-ethylhexyl)-3,6-(
N
′′,
N
′′′-dibutyl)diaza-octane-1,8-diamide (DADA). Two oxygen atoms of the diamide moiety seem to be responsible for controlling the metal ion extraction ability of PIPDA, whereas two nitrogen atoms of the piperazine moiety most probably dictate the separation factor between the Am(
iii
) and Eu(
iii
) ions in PIPDA. In addition, scalar relativistic density functional theory (DFT) in conjunction with Born-Haber thermodynamics was used herein to compliment the experimental selectivity. The experimentally observed preferential selectivity of PIPDA for Am(
iii
) ion over the Ln(
iii
) ion was corroborated by the computed extraction free energy, Δ
G
ext
. The covalent nature of bonding between the metal ions and the ligand was confirmed by analyzing the Mayer bond order and bond character analysis using the atom in molecule concept. Though the conformational rigidity of PIPDA gives stronger interaction than DADA, it does not offer a significant advantage over DADA in terms of the separation factor. The marginal increase in the separation factor for PIPDA over DADA might be attributed to the piperazine nitrogen and to the ligand architecture during complex formation.
The isolation of Am(
iii
) ion from Ln(
iii
) ions is very crucial for the safe disposal of nuclear wastes and thus, studies are being continuously pursued to accomplish this goal.
Superior uptake capacity of MWCNT-AA for Hg(II) over other sorbents leading to small bed height in continuous fixed bed column treatment of Hg-waste water.
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•Amidoamine functionalized ...multi-walled carbon nanotubes (MWCNT-AA) have been prepared and characterized.•MWCNT-AA was used for removal of Hg(II)•The adsorbent showed superior selectivity with high adsorption capacity towards mercury compared to other metal ions.•The nano adsorbent exhibits a good reusability.•Density functional theoretical calculations correlate the experimental selectivity.
Amidoamine functionalized multi-walled carbon nanotubes (MWCNT-AA) have been prepared and characterized. Separation of mercury(II) ions from aqueous solution by solid-liquid extraction has been investigated using the synthesized material as an adsorbent. Batch adsorption studies as a function of pH, contact time, initial metal ion concentration, and temperature have been carried out. The best fit for the adsorption equilibrium data was observed with Redlich-Peterson isotherm model and the kinetics data showed superior fitting for pseudo second order model, signifying chemisorption. The adsorbent showed superior selectivity with high adsorption capacity towards mercury as compared to other metal ions present in industrial waste water containing mercury. The MWCNT-AA was successfully used for six adsorption-desorption cycles without significant loss of uptake using 0.05M EDTA as desorbing agent. A small scale fixed bed column study was demonstrated to test the scale up application. DFT theoretical calculations establish the bi-dentate mode of complexation and correlate the experimental selectivity.
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•DFT and MD simulations was used to develop a crown ether functionalized resins for the isotope separation of gadolinium.•The column chromatography experiments for isotope separation ...of Gd were carried out using PMADB18C6 resin.•Both MD simulations and experiments suggest Temkin type adsorption isotherm.•The adsorption capacity for gadolinium with prepared PMADB18C6 resin was modest.•The separation coefficient(ε) for Gd155/158, Gd156/158, Gd157/158, and Gd155/160 isotopic pairs were encouraging.
Di-benzo-18-crown-6 ether (DB18C6) functionalized polymethyl acrylic acid (PMA) resin was synthesized after screening by employing density functional theory (DFT) and molecular dynamics (MD) simulations for the enrichment of gadolinium isotopes, Gd-155 and Gd-157. Batch adsorption and column chromatography studies were performed at various pH, gadolinium ion concentration and temperatures to check its efficacy and validation of theoretical approach. The adsorption capacity of gadolinium ion with the PMADB18C6 resin was found to be quite modest with a value of 1.128 mg/g. Both MD simulations and adsorption experiments confirm the Temkin type of adsorption isotherm. The positive entropy change along with the positive enthalpy change indicates that sorption of the Gd3+ ion with PMADB18C6 is entropy driven process. From the chromatography experiments, the lighter isotope (Gd-155) is seen to be depleted in the breakthrough volume samples which specify that the resin phase is depleted with heavier isotope (e.g Gd-160) contrast to natural Gd composition. The separation coefficient (ε) for Gd155/158, Gd156/158, Gd157/158, Gd155/160 and Gd157/160 isotopic pairs were found to be 1.67 × 10−3, 2.65 × 10−3, 5.40 × 10−4, 3.18 × 10−3 and 1.87 × 10−3 respectively. The experimental isotopic separation factor corroborates the DFT findings. Further, both DFT and MD simulations confirm the experimentally observed endothermic complexation of Gd3+ ion with PMADB18C6 resin. The present findings employing combined DFT, MD simulations and experimental approaches are expected to benefit in the fundamental understanding of molecular complexation based isotope separation and design and development of future gadolinium isotopic enrichment technologies using chemical exchange methods.
Within coastal communities, sea level rise (SLR) will result in widespread intermittent flooding and long-term inundation. Inundation effects will be evident, but isolation that arises from the loss ...of accessibility to critical services due to inundation of transportation networks may be less obvious. We examine who is most at risk of isolation due to SLR, which can inform community adaptation plans and help ensure that existing social vulnerabilities are not exacerbated. Combining socio-demographic data with an isolation metric, we identify social and economic disparities in risk of isolation under different SLR scenarios (1-10 ft) for the coastal U.S. We show that Black and Hispanic populations face a disproportionate risk of isolation at intermediate levels of SLR (4 ft and greater). Further, census tracts with higher rates of renters and older adults consistently face higher risk of isolation. These insights point to significant inequity in the burdens associated with SLR.
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