This work shows how multiple non-covalent interactions are employed to control metallosupramolecular architectures and we demonstrate that a ligand, which contains two bidentate domains separated by ...a ArOH spacer, forms a mesocate when complexed with Ag(i). However, changing this to an ArOCH2CH2Ph spacer unit results in a 1-dimensional helical polymer upon reaction with the same cation. Reaction of Ag(i) with the ArOMe derivative gives a hexanuclear circular helicate which forms inter-assembly Ag...Ag interactions resulting in a 3-dimensional honeycomb-like polymer of hexanuclear circular helicates.
A series of ligands that contain both N-donor and N-oxide donor atoms have been synthesised and ligands
L
5
,
L
6
,
L
7
and
L
8
contain, 4, 6, 5, and 6 donor atoms respectively. The smallest ligand
L
...5
forms a mononuclear complex with Cu
2+
(Cu(
L
5
)(ClO
4
)
2
(MeCN)) whereas
L
6
and
L
7
form dinuclear double helicates with Ni
2+
and Cu
2+
respectively (Ni
2
(
L
6
)
2
4+
and Cu
2
(
L
7
)
2
4+
).
L
8
forms a tetranuclear cyclic helicate upon reaction with Co
2+
(Co
4
(
L
8
)
4
8+
) and in all cases the complexes are characterised by single-crystal X-ray diffraction and ESI-MS. The N-oxide units imparts flexibility in the ligand strand and where the unoxidised ligand strand forms a cyclic helicate, the incorporation of an N-oxide unit allows the formation of the dinuclear double helicate.
Ligands that contain both N-donor and N-oxide donor atoms have been synthesised and reaction with 1st row transition metal ions gives mononuclear, dinuclear double helicate and tetranuclear cyclic helicate complexes.
A series of ligands that contain both N-donor and N-oxide donor atoms have been synthesised and ligands L5, L6, L7 and L8 contain, 4, 6, 5, and 6 donor atoms respectively. The smallest ligand L5 ...forms a mononuclear complex with Cu2+ (Cu(L5)(ClO4)2(MeCN)) whereas L6 and L7 form dinuclear double helicates with Ni2+ and Cu2+ respectively (Ni2(L6)24+ and Cu2(L7)24+). L8 forms a tetranuclear cyclic helicate upon reaction with Co2+ (Co4(L8)48+) and in all cases the complexes are characterised by single-crystal X-ray diffraction and ESI-MS. The N-oxide units imparts flexibility in the ligand strand and where the unoxidised ligand strand forms a cyclic helicate, the incorporation of an N-oxide unit allows the formation of the dinuclear double helicate.
This work shows how multiple non-covalent interactions are employed to control metallosupramolecular architectures and we demonstrate that a ligand, which contains two bidentate domains separated by ...a ArOH spacer, forms a mesocate when complexed with Ag(
i
). However, changing this to an ArOCH
2
CH
2
Ph spacer unit results in a 1-dimensional helical polymer upon reaction with the same cation. Reaction of Ag(
i
) with the ArOMe derivative gives a hexanuclear circular helicate which forms inter-assembly Ag Ag interactions resulting in a 3-dimensional honeycomb-like polymer of hexanuclear circular helicates.
A bis-bidentate ligand forms a hexanuclear circular helicate which results in a 3-dimensional honeycomb-like polymer
via
argentophilic interactions.
The American Stroke Association (ASA) assembled a multidisciplinary group of experts to develop recommendations regarding the potential effectiveness of establishing an identification program for ...stroke centers and systems. "Identification" refers to the full spectrum of models for assessing and recognizing standards of quality care (self-assessment, verification, certification, and accreditation). A primary consideration is whether stroke center identification might improve patient outcomes.
In February 2001, ASA, with the support of the Stroke Council's Executive Committee, decided to embark on an evaluation of the potential impact of stroke center identification. HealthPolicy R&D was selected to prepare a comprehensive report. The investigators reported on models outside the area of stroke, ongoing initiatives within the stroke community (such as Operation Stroke), and state and federal activities designed to improve care for stroke patients. The investigators also conducted interviews with thought leaders in the stroke community, representing a diverse sampling of specialties and affiliations. In October 2001, the Advisory Working Group on Stroke Center Identification developed its consensus recommendations. This group included recognized experts in neurology, emergency medicine, emergency medical services, neurological surgery, neurointensive care, vascular disease, and stroke program planning.
There are a variety of existing identification programs, generally falling within 1 of 4 categories (self-assessment, verification, certification, and accreditation) along a continuum with respect to intensity and scope of review and consumption of resources. Ten programs were evaluated, including Peer Review Organizations, trauma centers, and new efforts by the National Committee on Quality Assurance and the Joint Commission on the Accreditation of Healthcare Organizations to identify providers and disease management programs. The largest body of literature on clinical outcomes associated with identification programs involves trauma centers. Most studies support that trauma centers and systems lead to improved mortality rates and patient outcomes. The Advisory Working Group felt that comparison to the trauma model was most relevant given the need for urgent evaluation and treatment of stroke. The literature in other areas generally supports the positive impact of identification programs, although patient outcomes data have less often been published. In the leadership interviews, participants generally expressed strong support for pursuing some form of voluntary identification program, although concerns were raised that this effort could meet with some resistance.
Identification of stroke centers and stroke systems competencies is in the best interest of stroke patients in the United States, and ASA should support the development and implementation of such processes. The purpose of a stroke center/systems identification program is to increase the capacity for all hospitals to treat stroke patients according to standards of care, recognizing that levels of involvement will vary according to the resources of hospitals and systems.
Disinfection by-products (DBPs) are formed when naturally occurring organic matter reacts with chlorine used in drinking water treatment, and DBPs formed in chlorinated drinking water samples have ...been shown to cause a genotoxic response. The objective of the current study was to further understand the principles of biofiltration and the resulting impacts on the formation of DBPs and genotoxicity. Pilot-scale systems were utilized to assess the performance of engineered biofilters enhanced with hydrogen peroxide, in-line coagulants, and nutrients when compared to passively operated biofilters and conventional treatment (coagulation, flocculation, sedimentation, non-biological filtration). Organic fractionation was completed using liquid chromatography-organic carbon detection (LC-OCD). Water samples were chlorinated after collection and examined for the removal of trihalomethane (THM), haloacetic acid (HAA), and adsorbable organic halide (AOX) precursors. Additionally, the formation potential of two halogenated furanones, 3-chloro-4(dichloromethyl)-2(5H)-furanone (MX) and mucochloric acid (MCA), and genotoxicity was determined. Biofiltration was shown to preferentially remove more DBP precursors than dissolved organic carbon (DOC). Formation potential of the unregulated DBPs, including MX and MCA, and genotoxic response was shown to be correlated to THM formation. These results infer that monitoring for THMs and HAAs provide insight to the formation of more mutagenic DBPs such as halogenated furanones, and that biofiltration may preferentially remove precursors to DBPs at a rate exceeding the removal of DOC.
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•Enhanced and passive biofilters were examined at two pilot plants in Ontario, Canada.•The average formation of THMs, HAAs, and AOX were correlated at each location.•The formation of MX and MCA was correlated to THM and HAA formation at each location.•The average genotoxicity was correlated to the average formation of THMs and HAAs.
Biofiltration has been shown to be effective for disinfection by-product (DBP) precursor control, however few studies have considered its role in the potential formation of DBPs. Biofilm is composed ...of heterogeneous bacteria as well as extracellular polymeric substances (EPS). The objective of this study was to determine the contribution of biofilm-related materials such as EPS to form nitrogen-containing DBPs upon chloramination, and to determine the influence of cyclical (scheduled on-off) biofilter operation on DBP precursor removal. Biologically active media was sampled from a full-scale biofilter operating under cold-water conditions (3.6 ± 0.5 °C) and extracted using a cation exchange resin into a phosphate buffer solution. Biomass concentrations, as determined using adenosine triphosphate (ATP) measurements, remained stable at 298 ± 55 ng ATP/g media over the trial period. N-nitrosodimethylamine (NDMA) and haloacetonitrile (HAN4) formation potential (FP) tests conducted under uniform formation conditions (UFC) using extracted biofilm yielded 0.80 ± 0.27 ng NDMA/g media and 18.7 ± 3.3 ng dichloroacetonitrile (DCAN)/g media. Further analyses of extracted biofilm using fluorescence spectroscopy and liquid chromatography-organic carbon detection indicated the presence of proteins above 20 kDa and humic-like substances. Extracted proteins (93.5 ± 8.1 μg/g media) correlated well (R = 0.90) with UV 280 measurements, indicating that spectrophotometry may serve as a valuable tool to quantify proteins in extracted biofilms. While substances in biofilms can serve as NDMA and DCAN precursors, the full-scale cyclically-operated biofilter that was examined did not show release of NDMA precursors during start-up following stagnation periods of 6 h or more. These biofilters consistently removed 6.9 ± 4.3 ng/L of NDMA precursors; typical NDMA UFC-FP of biofilter effluent was 8.5 ± 2.6 ng/L.
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•Biofilm extracted from filter media contained 93.5 ± 8.1 μg proteins/g media.•Extracted biofilm produced 0.80 ± 0.27 ng NDMA and 18.7 ± 3.3 ng DCAN per g media.•Biofiltration removed ∼50% of NDMA precursors during typical steady-state operation.
Previous studies have reported that biofilm extracted from full-scale biofilters can serve as nitrogenous disinfection by-product (N-DBP) precursors. Detached biofilm materials could escape during ...filter ripening and form N-DBP upon chloramination. This study examined the potential breakthrough of biofilm and N-DBP precursors during filter ripening at two water treatment plants (WTPs). The presence of biofilm material in aqueous samples was estimated by total adenosine triphosphate (tATP) levels; N-DBP formation potential (FP) tests were conducted under uniform formation conditions to quantify N-nitrosodimethylamine (NDMA) and haloacetonitrile (HAN4) precursors. While tATP peaks in filter effluent were observed post backwash at both WTPs, temporary increases of effluent NDMA FP were only observed during filter ripening where particle-associated NDMA precursors served as the dominant contributor. Overall, biofilters examined in this study demonstrated a consistent removal of NDMA FP regardless of the filter ripening process.
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•Elevated NDMA FP and total ATP levels in the influent during filter ripening.•Breakthrough of particulate NDMA precursors during filter ripening.•Biofilters consistently removed NDMA precursors regardless of filter ripening.
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