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Among breast cancer subtypes, triple-negative breast cancer stands out as the most aggressive, with patients facing a 40% mortality rate within the initial five years. The limited treatment options and unfavourable prognosis for triple-negative patients necessitate the development of novel therapeutic strategies. Photodynamic therapy (PDT) is an alternative treatment that can effectively target triple-negative neoplastic cells such as MDA-MB-231. In this in vitro study, we conducted a comparative analysis of the PDT killing rate of unbound Rose Bengal (RB) in solution versus RB-encapsulated chitosan nanoparticles to determine the most effective approach for inducing cytotoxicity at low laser powers (90 mW, 50 mW, 25 mW and 10 mW) and RB concentrations (50 µg/mL, 25 µg/mL, 10 µg/mL and 5 µg/mL). Intracellular singlet oxygen production and cell uptake were also determined for both treatment modalities. Dark toxicity was also assessed for normal breast cells. Despite the low laser power and concentration of nanoparticles (10 mW and 5 µg/mL), MDA-MB-231 cells experienced a substantial reduction in viability (8 ± 1%) compared to those treated with RB solution (38 ± 10%). RB nanoparticles demonstrated higher singlet oxygen production and greater uptake by cancer cells than RB solutions. Moreover, RB nanoparticles display strong cytocompatibility with normal breast cells (MCF-10A). The low activation threshold may be a crucial advantage for specifically targeting malignant cells in deep tissues.
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Fotoquimioterapia , Neoplasias de Mama Triplo Negativas , Humanos , Neoplasias de Mama Triplo Negativas/tratamento farmacológico , Neoplasias de Mama Triplo Negativas/patologia , Rosa Bengala/farmacologia , Rosa Bengala/uso terapêutico , Oxigênio Singlete , Linhagem Celular Tumoral , Fármacos Fotossensibilizantes/farmacologia , Fármacos Fotossensibilizantes/uso terapêuticoRESUMO
Cancer, a prominent cause of death, presents treatment challenges, including high dosage requirements, drug resistance, poor tumour penetration and systemic toxicity in traditional chemotherapy. Photodynamic therapy, using photosensitizers like rose bengal (RB) with a green laser, shows promise against breast cancer cells in vitro. However, the hydrophilic RB struggles to efficiently penetrate the tumour site due to the unique clinical microenvironment, aggregating around rather than entering cancer cells. In this study, we have synthesized and characterized RB-encapsulated chitosan nanoparticles with a peak particle size of ~200 nm. These nanoparticles are readily internalized by cells and, in combination with a green laser (λ = 532 nm) killed 94-98% of cultured human breast cancer cells (MCF-7) and prostate cancer cells (PC3) at a low dosage (25 µg/mL RB-nanoparticles, fluence ~126 J/cm2, and irradiance ~0.21 W/cm2). Furthermore, these nanoparticles are not toxic to cultured human normal breast cells (MCF10A), which opens an avenue for translational applications.
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Neoplasias da Mama , Nanopartículas , Fotoquimioterapia , Neoplasias da Próstata , Masculino , Humanos , Rosa Bengala/farmacologia , Fármacos Fotossensibilizantes/farmacologia , Neoplasias da Próstata/tratamento farmacológico , Neoplasias da Mama/tratamento farmacológico , Microambiente TumoralRESUMO
This study uses 35Cl and 14N solid-state NMR (SSNMR) spectroscopy and dispersion-corrected plane-wave density functional theory (DFT) calculations for the structural characterization of chloride salts of nutraceuticals in their bulk and dosage forms. For eight nutraceuticals, we measure the 35Cl EFG tensor parameters of the chloride ions and use plane-wave DFT calculations to elucidate relationships between NMR parameters and molecular-level structure, which provide rapid NMR crystallographic assessments of structural features. We employ both 35Cl direct excitation and 1Hâ35Cl cross-polarization methods to characterize a dosage form containing α-d-glucosamine HCl, observe possible impurity and/or adulterant phases, and quantify the weight percent of the active ingredient. To complement this, we also investigate 14N SSNMR spectroscopy and DFT calculations to characterize nitrogen atoms in the nutraceuticals. This includes a discussion of targeted acquisition experimental protocols (i.e., acquiring a select region of the overall pattern that features key discontinuities) that allow ultrawideline spectra to be acquired rapidly, even for unreceptive samples (i.e., those with long values of T1(14N), short values of T2eff(14N), or very broad patterns). It is hoped that these experimental and computational protocols will be useful for the characterization of various solid forms of nutraceuticals (i.e., salts, polymorphs, hydrates, solvates, cocrystals, amorphous solid dispersions, etc.), help detect impurity and counterfeit solid phases in dosage forms, and serve as a foundation for future NMR crystallographic studies of nutraceutical solid forms, including studies using ab initio crystal structure prediction algorithms.
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Cloretos , Suplementos Nutricionais , Cloretos/química , Teoria da Densidade Funcional , Espectroscopia de Ressonância Magnética/métodos , Estrutura MolecularRESUMO
Organophosphates (OPs) are used worldwide as pesticides. However, acute and chronic exposure to OPs can cause serious adverse health effects. The mechanism of delayed OP toxicity is thought to involve off-target inhibition of serine proteases, although the precise molecular details remain unclear owing to the lack of an analytical method for global detection of protein targets of OPs. Here, we report the development of a mass spectrometry method to identify OP-adducted proteins from complex mixtures in a nontargeted manner. Human plasma was incubated with the OP dichlorvos that was 50% isotopically labeled and 50% unlabeled. Proteins and protein adducts were extracted, digested, and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to detect "twin ions" of peptides that were covalently modified by a chemical reaction with dichlorvos. The LC-MS/MS data were processed by a blended data analytics software (Xenophile) to detect the amino acid residue sites of proteins that were covalently modified by exposure to OPs. We discovered that OPs can transmethylate the N, S, and O side chains of His, Cys, Glu, Asp, and Lys residues. For model systems, such transmethylation reactions were confirmed by LC-MS, nuclear magnetic resonance (NMR), and rationalized using electronic structure calculations. Methylation of the ubiquitous antioxidant glutathione by dichlorvos can decrease the reducing/oxidizing equilibrium of glutathione in liver extracts, which has been implicated in diseases and pathological conditions associated with delayed OP toxicity.
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Proteínas Sanguíneas/química , Nitrogênio/química , Organofosfatos/química , Oxigênio/química , Enxofre/química , Cromatografia Líquida , Humanos , Metilação , Organofosfatos/toxicidade , Espectrometria de Massas em TandemRESUMO
This paper introduces an 1 H NMR method to identify individual divalent metal cations Be2+ , Mg2+ , Ca2+ , Sr2+ , Zn2+ , Cd2+ , Hg2+ , Sn2+ , and Pb2+ in aqueous salt solutions through their unique signal shift and coupling after complexation with the salt of ethylenediaminetetraacetic acid (EDTA). Furthermore, quantitative determination applied for the divalent metal cations Ca2+ , Mg2+ , Hg2+ , Sn2+ , Pb2+ , and Zn2+ (limit of quantification: 5-22 µg/ml) can be achieved using an excess of EDTA with aqueous model salt solutions. An internal standard is not required because a known excess of EDTA is added and the remaining free EDTA can be used to recalculate the quantity of chelated metal cations. The utility of the method is demonstrated for the analysis of divalent cations in some food supplements and in pharmaceutical products.
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Quelantes/química , Suplementos Nutricionais/análise , Ácido Edético/química , Metais Alcalinoterrosos/análise , Metais Pesados/análise , Preparações Farmacêuticas/química , Cátions Bivalentes/análise , Espectroscopia de Prótons por Ressonância Magnética , Sais/química , SoluçõesRESUMO
Correction for 'The value of universally available raw NMR data for transparency, reproducibility, and integrity in natural product research' by James B. McAlpine et al., Nat. Prod. Rep., 2018, DOI: .
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Covering: up to 2018With contributions from the global natural product (NP) research community, and continuing the Raw Data Initiative, this review collects a comprehensive demonstration of the immense scientific value of disseminating raw nuclear magnetic resonance (NMR) data, independently of, and in parallel with, classical publishing outlets. A comprehensive compilation of historic to present-day cases as well as contemporary and future applications show that addressing the urgent need for a repository of publicly accessible raw NMR data has the potential to transform natural products (NPs) and associated fields of chemical and biomedical research. The call for advancing open sharing mechanisms for raw data is intended to enhance the transparency of experimental protocols, augment the reproducibility of reported outcomes, including biological studies, become a regular component of responsible research, and thereby enrich the integrity of NP research and related fields.
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Produtos Biológicos/química , Espectroscopia de Ressonância Magnética/métodos , Conformação Molecular , Reprodutibilidade dos TestesRESUMO
Tertiary phosphines remain widely utilized in synthesis, most notably as supporting ligands in metal complexes. A series of triarylphosphines bearing one to three hexa-peri-hexabenzocoronene (HBC) substituents has been prepared by an efficient divergent route. These "superphenylphosphines", P{HBC(t-Bu)5}nPh3-n (n = 1-3), form the palladium complexes PdCl2L2 and Pd2Cl4L2 where the isomer distribution in solution is dependent on the number of HBC substituents. The crystalline structures of five complexes all show intramolecular π-stacking between HBC-phosphines to form a supramolecular bidentate-like ligand that distorts the metal coordination geometry. When n = 2 or 3, the additional HBC substituents engage in intermolecular π-stacking to assemble the complexes into continuous ribbons or sheets. The phosphines adopt HBC's characteristics including strong optical absorption, green emission, and redox activity.
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PbS submicron crystals were formed by thermolysis of two different lead dithiocarbamate complexes. These precursors were readily synthesized and fully characterized, and in situ synchrotron powder diffraction experiments were performed to characterize their decomposition. The structure and purity of resultant PbS was examined using scanning electron and transmission electron microscopies, powder X-ray diffraction, and infrared spectroscopy. Submicron crystalline PbS was used to create a new PbS thermistor with excellent sensitivity and an ultrarapid thermal response time.
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OBJECTIVE: We aim to quantify the impact of obesity on maternal intensive care unit (ICU) admission. MATERIALS AND METHODS: This is a population-based, retrospective cohort study of Ohio live births from 2006 to 2012. The primary outcome was maternal ICU admission. The primary exposure was maternal body mass index (BMI). Relative risk (RR) of ICU admission was calculated by BMI category. Multivariate logistic regression quantified the risk of obesity on ICU admission after adjustment for coexisting factors. RESULTS: This study includes 999,437 births, with peripartum maternal ICU admission rate of 1.10 per 1,000. ICU admission rate for BMI 30 to 39.9 kg/m2 was 1.24 per 1,000, RR: 1.20 (95% confidence interval [CI]: 1.07, 1.35); BMI 40 to 49.9 kg/m2 had ICU admission rate of 1.80 per 1,000, RR: 1.73 (95% CI: 1.38, 2.17); and BMI ≥ 50 kg/m2 had ICU admission rate of 2.98 per 1,000, RR: 1.73 (95% CI: 1.77, 4.68). After adjustment, these increases persisted in women with BMI 40 to 49.9 kg/m2 with adjusted relative risk (adjRR) of 1.37 (95% CI: 1.05, 1.78) and in women with BMI ≥ 50 kg/m2, adjRR: 1.69 (95% CI: 1.01, 2.83). CONCLUSION: Obesity is a risk factor for maternal ICU admission. Risk increases with BMI. After adjustment, BMI ≥ 40 kg/m2 is an independent risk factor for ICU admission.
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Unidades de Terapia Intensiva , Obesidade/complicações , Admissão do Paciente/estatística & dados numéricos , Complicações na Gravidez/epidemiologia , Adolescente , Adulto , Índice de Massa Corporal , Cesárea , Feminino , Humanos , Modelos Logísticos , Análise Multivariada , Ohio/epidemiologia , Gravidez , Cuidado Pré-Natal , Sistema de Registros , Estudos Retrospectivos , Fatores de Risco , Adulto JovemRESUMO
Metal-free polymeric carbon nitrides (PCNs) are promising photocatalysts for solar hydrogen production, but their structure-photoactivity relationship remains elusive. Two PCNs were characterized by dynamic-nuclear-polarization-enhanced solid-state NMR spectroscopy, which circumvented the need for specific labeling with either 13 C- or 15 N-enriched precursors. Rapid 1D and 2D data acquisition was possible, providing insights into the structural contrasts between the PCNs. Compared to PCN_B with lower performance, PCN_P is a more porous and more active photocatalyst that is richer in terminal N-H bonds not associated with interpolymer chains. It is proposed that terminal N-H groups act as efficient carrier traps and reaction sites.
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OBJECTIVE: We describe a technique to maintain amniotic fluid in fetuses with severe oligo-/anhydramnios secondary to lower urinary tract obstruction or fetal renal disease when urine production is inadequate to maintain a normal amniotic fluid volume (AFV). METHODS: An amnioport was inserted into the amniotic space. The catheter was secured to prevent dislodgment and tunneled to a subcutaneous reservoir. The reservoir was accessed as necessary, infusing normal saline to maintain AFV. Pregnancy continued until term or indicated delivery. RESULTS: Since 2010, 15 patients in this category were considered for an amnioport. Six chose comfort care and one elected percutaneous amnioinfusions. Nine amnioport procedures were performed in eight patients. There were no fetal deaths. All eight had successful restoration and maintenance of amniotic fluid. Delivery ranged from 9 to 96 days after placement (mean 63.7 days). One died due to unrecognized laryngeal web and another one died of pulmonary hypoplasia after preterm premature rupture of membranes. None of the remaining six had pulmonary hypoplasia. Three remain alive. DISCUSSION: Severe oligo-/anhydramnios in the second trimester secondary to fetal anomalies is almost uniformly lethal due to pulmonary hypoplasia without restoration of amniotic fluid. The amnioport procedure may allow pulmonary survival but commits families to postnatal care decisions regarding pulmonary and renal complications.
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Cateterismo/métodos , Oligo-Hidrâmnio/terapia , Doenças Urológicas/complicações , Feminino , Humanos , Oligo-Hidrâmnio/diagnóstico por imagem , Gravidez , Resultado do Tratamento , Doenças Urológicas/diagnóstico por imagem , Doenças Urológicas/terapiaRESUMO
BACKGROUND: In 2011, the US national rate of smoking early in pregnancy was 11.5%. Unfortunately, our home state of Ohio had a rate twice as high at 23%. Smoking in pregnancy remains one of the most important modifiable risk factors for pregnancy complications, specifically preterm birth. OBJECTIVE: The objective of the study was to quantify the preterm birth risk to various trimester-specific smoking behaviors. STUDY DESIGN: The study was a population-based, retrospective cohort study of singleton non-anomalous live births, using Ohio birth records 2006 to 2012. Preterm birth rates were compared between non-smokers and women who smoked in the preconception period only, those who quit smoking after the 1st and 2nd trimesters, and those who smoked throughout pregnancy. Multivariate logistic regression quantified the risk of smoking with cessation at various times in pregnancy and preterm birth risk, adjusted for maternal race, education, age, Medicaid use, marital status, and parity. A stratified analysis was performed on the basis of preterm birth subtype: spontaneous preterm birth versus indicated preterm birth. We also performed an additional analysis stratifying for maternal race using the 2 largest categories of race (non-Hispanic white and non-Hispanic black). RESULTS: Of the 913,757 birth records analyzed, nearly 25% of the women reported some smoking behavior on the birth certificate data. Of smokers, less than half quit during pregnancy (38.8% vs 61.2% smoked throughout pregnancy). Early quitters had a similar preterm birth rate compared with non-smokers. Women who smoked through the 1st trimester only did not have a significant increase in their overall preterm birth odds ratio <37 weeks; however, it did increase the odds of extreme preterm birth <28 weeks by 20% (adjusted odds ratio, 1.20; 95% confidence interval [CI], 1.02, 1.40). Quitting late in pregnancy resulted in the highest odds ratio increase: 70% for preterm birth <37 weeks (adjusted odds ratio 1.70; CI, 1.60, 1.80), even after adjustment for the confounding influences. Quitting smoking early in pregnancy after the 1st trimester did not increase the overall risk of spontaneous or indicated preterm birth <37 weeks significantly. However, quitting after the 1st trimester was associated with a significant increase in risk of extreme spontaneous preterm birth <28 weeks, an effect not seen with indicated preterm birth <28 weeks. Delaying cessation until late in pregnancy-after the 2nd trimester-was associated with the highest risk increases, 65% increased odds of spontaneous and 78% increase in odds of indicated preterm births. The rate of preterm births to non-Hispanic black mothers was increased in all categories over those of non-Hispanic white mothers. The relative influence of smoking cessation in pregnancy was similar in black compared with white mothers. The effect modification in the regression model was analyzed and revealed no significant interaction between race and smoking patterns on preterm birth risk. CONCLUSION: Smoking throughout pregnancy is associated with an increased risk of preterm birth. However, quitting early in pregnancy negates this risk. Widespread programs aimed at smoking cessation early in pregnancy could have a significant impact on reducing the rate of preterm birth nationally.
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Trimestres da Gravidez , Nascimento Prematuro/etiologia , Abandono do Hábito de Fumar/estatística & dados numéricos , Fumar/efeitos adversos , Fumar/epidemiologia , Adulto , Feminino , Humanos , Ohio/epidemiologia , Vigilância da População , Gravidez , Estudos Retrospectivos , Fatores de Risco , Adulto JovemRESUMO
Dramatic changes in molecular structure, degradation pathway, and porosity of biochar are observed at pyrolysis temperatures ranging from 250 to 550 °C when bamboo biomass is pretreated by iron-sulfate-clay slurries (iron-clay biochar), as compared to untreated bamboo biochar. Electron microscopy analysis of the biochar reveals the infusion of mineral species into the pores of the biochar and the formation of mineral nanostructures. Quantitative (13)C nuclear magnetic resonance (NMR) spectroscopy shows that the presence of the iron clay prevents degradation of the cellulosic fraction at pyrolysis temperatures of 250 °C, whereas at higher temperatures (350-550 °C), the clay promotes biomass degradation, resulting in an increase in both the concentrations of condensed aromatic, acidic, and phenolic carbon species. The porosity of the biochar, as measured by NMR cryoporosimetry, is altered by the iron-clay pretreatment. In the presence of the clay, at lower pyrolysis temperatures, the biochar develops a higher pore volume, while at higher temperature, the presence of clay causes a reduction in the biochar pore volume. The most dramatic reduction in pore volume is observed in the kaolinite-infiltrated biochar at 550 °C, which is attributed to the blocking of the mesopores (2-50 nm pore) by the nonporous metakaolinite formed from kaolinite.
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Carbono , Carvão Vegetal/química , Biomassa , Minerais , Estrutura Molecular , PorosidadeRESUMO
Objective The objective of this study was to quantify the influence of various patient characteristics on early smoking cessation to better identify target populations for focused counseling and interventions. Study Design This study was a population-based retrospective cohort study of 1,003,532 Ohio live births more than 7 years (2006-2012). Women who quit smoking in the first trimester were compared with those who smoked throughout pregnancy. Logistic regression estimated the strength of association between patient factors and smoking cessation. Results The factors most strongly associated with early smoking cessation were non-white race and Hispanic ethnicity, at least some college education, early prenatal care, marriage, and breastfeeding. Numerous factors commonly associated with adverse perinatal outcomes were found to have a negative association with smoking cessation: low educational attainment, limited or late prenatal care, prior preterm birth, age < 20 years, age ≥ 35 years, and indicators of low SES. In addition, the heaviest smokers (≥ 20 cigarette/day) were least likely to quit (adjusted relative risk [RR], 0.35; 95% confidence interval 0.34, 0.36). Conclusion Early prenatal care and initiation of breastfeeding before discharge from the hospital are associated with increased RR of quitting early in pregnancy by 52 and 99%, respectively. Public health initiatives and interventions should focus on the importance of early access to prenatal care and education regarding smoking cessation for these particularly vulnerable groups of women who are at inherently high risk of pregnancy complications.
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Complicações na Gravidez/epidemiologia , Gravidez , Abandono do Hábito de Fumar/estatística & dados numéricos , Fumar/epidemiologia , Fumar/terapia , Adulto , Aleitamento Materno/estatística & dados numéricos , Aconselhamento/métodos , Feminino , Humanos , Recém-Nascido , Modelos Logísticos , Ohio/epidemiologia , Complicações na Gravidez/etiologia , Cuidado Pré-Natal/métodos , Estudos Retrospectivos , Fatores de Risco , Fumar/tendências , Fatores de Tempo , Adulto JovemRESUMO
In order to understand reaction outcomes in ionic liquids, it is crucial to be able to follow the progress of these reactions. This review highlights the advantages of NMR spectroscopy over other analytical techniques in following reaction progress in ionic liquids, particularly addressing the practical aspects of the methodology and highlighting the range of processes that can be readily followed. Copyright © 2014 John Wiley & Sons, Ltd.
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The exceptional strength and extensibility of spider dragline silk have been thought to be facilitated by two spidroins, major ampullate spidroin 1 (MaSp1) and major ampullate spidroin 2 (MaSp2), under the assumption that protein secondary structures are coupled with the expressed spidroins. We tested this assumption for the dragline silk of three co-existing Australian spiders, Argiope keyserlingi, Latrodectus hasselti and Nephila plumipes. We found that silk amino acid compositions did not differ among spiders collected in May. We extended these analyses temporally and found the amino acid compositions of A. keyserlingi silks to differ when collected in May compared to November, while those of L. hasselti did not. To ascertain whether their secondary structures were decoupled from spidroin expression, we performed solid-state nuclear magnetic resonance spectroscopy (NMR) analysis on the silks of all spiders collected in May. We found the distribution of alanine toward ß-sheet and 3,10helix/random coil conformations differed between species, as did their relative crystallinities, with A. keyserlingi having the greatest 3,10helix/random coil composition and N. plumipes the greatest crystallinity. The protein secondary structures correlated with the mechanical properties for each of the silks better than the amino acid compositions. Our findings suggested that a differential distribution of alanine during spinning could decouple secondary structures from spidroin expression ensuring that silks of desirable mechanical properties are consistently produced. Alternative explanations include the possibility that other spidroins were incorporated into some silks.
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Fibroínas/química , Proteínas de Insetos/química , Seda/química , Aminoácidos/química , Animais , Cromatografia Líquida de Alta Pressão , Espectroscopia de Ressonância MagnéticaRESUMO
Adjacent ecosystems are influenced by organisms that move across boundaries, such as insects with aquatic larval stages and terrestrial adult stages, which transport energy and nutrients from water to land. However, the ecosystem-level effect of aquatic insects on land has generally been ignored, perhaps because the organisms themselves are individually small. At the naturally productive Lake Mývatn, Iceland, we used two readily measured quantities: total insect emergence from water and relative insect density on land, to demonstrate an approach for estimating aquatic insect deposition (e.g., kg N x m(-2) x yr(-1)) to shore. Estimates from emergence traps between 2008 and 20.11 indicated a range of 0.15-3.7 g x m(-2) x yr(-1), or a whole-lake emergence of 3.1-76 Mg/yr; all masses are given as dry mass. Using aerial infall trap measurements of midge relative abundance over land, we developed a local-maximum decay function model to predict proportional midge deposition with distance from the lake. The dispersal model predicted midge abundance with R2 = 0.89, a pattern consistent among years, with peak midge deposition occurring 20-25 m inland and 70% of midges deposited within 100 m of shore. During a high-midge year (2008), we estimate midge deposition within the first 50 m of shoreline to be 100 kg xha(-1) x yr(-1), corresponding to inputs of 10 kg N x ha(-1) x yr(-1) and 1 kg P x ha(-1) x yr(-1), or about three to five times above background terrestrial N deposition rates. Consistent with elevated N input where midges are most dense, we observed that soil available nitrate in resin bags decreases with increasing distance from the lake. Our approach, generalizable to other systems, shows that aquatic insects can be a major source of nutrients to terrestrial ecosystems and have the capacity to significantly affect ecosystem processes.
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Chironomidae/fisiologia , Ecossistema , Lagos , Animais , Densidade DemográficaRESUMO
Quantitative NMR spectroscopy (qNMR) has been examined for purity assessment using a range of organic calibration standards of varying structural complexities, certified using the traditional mass balance approach. Demonstrated equivalence between the two independent purity values confirmed the accuracy of qNMR and highlighted the benefit of using both methods in tandem to minimise the potential for hidden bias, thereby conferring greater confidence in the overall purity assessment. A comprehensive approach to purity assessment is detailed, utilising, where appropriate, multiple peaks in the qNMR spectrum, chosen on the basis of scientific reason and statistical analysis. Two examples are presented in which differences between the purity assignment by qNMR and mass balance are addressed in different ways depending on the requirement of the end user, affording fit-for-purpose calibration standards in a cost-effective manner.
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Espectroscopia de Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/normas , Calibragem , Modelos Teóricos , Padrões de ReferênciaRESUMO
A range of solid-state NMR techniques is used to characterise a molecular host:guest complex consisting of a [5]polynorbornane bisurea host binding a terephthalate dianion guest. Detailed information is obtained on the molecular dynamics and associations from the point of view of both the host and guest molecules. The formation of the complex in the solid state is confirmed using (1)H 2D exchange NMR, and the 180° flipping of the (2)H-labelled terephthalate guest and its eventual expulsion from the complex at elevated temperatures are quantified using variable-temperature (2)H spin-echo experiments. Two-dimensional (1)H-(13)C HETCOR spectra obtained under fast magic angle spinning conditions (60 kHz) show a high resolution despite the poor crystallinity of the solid complex, and clearly reveal changes in the rigidity of the host molecule when complexed. Short-range intra- and intermolecular (1)H-(1)H proximities are also detected using 2D SQ-DQ correlation methods, providing insight into the molecular packing in the solid phase.