RESUMEN
BACKGROUND: Diagnosing atopic dermatitis (AD) in infants is challenging. OBJECTIVES: To determine the incidence and persistence of eczema and AD in infants using the UK Working Party (UKWP) and Hanifin and Rajka (H&R) criteria. METHODS: A cohort of 1834 infants was examined clinically at 3, 6 and 12 months of age. AD was diagnosed by UKWP (3, 6 and 12 months) and H&R (12 months) criteria. Logistic regression models were used to assess the relationship between AD and eczema. RESULTS: Eczema was observed in 628 (34·2%) infants (n = 240, n = 359 and n = 329 at 3, 6 and 12 months, respectively), with AD diagnosed in 212 (33·7%) infants with any eczema and in 64/78 (82%) infants with eczema at all three visits. The odds of AD were lower with first presentation of eczema at 6 [odds ratio (OR) 0·33, 95% confidence interval (CI) 0·22-0·48] or 12 months (OR 0·49, 95% CI 0·32-0·74) than at 3 months, and higher in infants with eczema at three (OR 23·1, 95% CI 12·3-43·6) or two (OR 6·5, 95% CI 4·3-9·9) visits vs. one visit only. At 12 months, 156/329 (47·4%) fulfilled the UKWP and/or H&R criteria; 27 (8%) fulfilled the UKWP criteria only and 65 (20%) only the H&R criteria. Of the 129 infants who fulfilled the H&R criteria, 44 (34·1%) did not meet the itch criterion. CONCLUSIONS: Used in combination and at multiple timepoints, the UKWP and H&R criteria for AD may be useful in clinical research but may have limited value in most other clinical settings.
Asunto(s)
Dermatitis Atópica , Eccema , Estudios de Cohortes , Dermatitis Atópica/diagnóstico , Dermatitis Atópica/epidemiología , Eccema/diagnóstico , Eccema/epidemiología , Humanos , Incidencia , Lactante , PruritoRESUMEN
BACKGROUND: Loss-of-function mutations in the skin barrier gene filaggrin (FLG) increase the risk of atopic dermatitis (AD), but their role in skin barrier function, dry skin and eczema in infancy is unclear. OBJECTIVES: To determine the role of FLG mutations in impaired skin barrier function, dry skin, eczema and AD at 3 months of age and throughout infancy. METHODS: FLG mutations were analysed in 1836 infants in the Scandinavian population-based PreventADALL study. Transepidermal water loss (TEWL), dry skin, eczema and AD were assessed at 3, 6 and 12 months of age. RESULTS: FLG mutations were observed in 166 (9%) infants. At 3 months, carrying FLG mutations was not associated with impaired skin barrier function (TEWL > 11·3 g m-2 h-1 ) or dry skin, but was associated with eczema [odds ratio (OR) 2·89, 95% confidence interval (CI) 1·95-4·28; P < 0·001]. At 6 months, mutation carriers had significantly higher TEWL than nonmutation carriers [mean 9·68 (95% CI 8·69-10·68) vs. 8·24 (95% CI 7·97-8·15), P < 0·01], and at 3 and 6 months mutation carriers had an increased risk of dry skin on the trunk (OR 1·87, 95% CI 1·25-2·80; P = 0·002 and OR 2·44, 95% CI 1·51-3·95; P < 0·001) or extensor limb surfaces (OR 1·52, 95% CI 1·04-2·22; P = 0·028 and OR 1·74, 95% CI 1·17-2·57; P = 0·005). FLG mutations were associated with eczema and AD in infancy. CONCLUSIONS: FLG mutations were not associated with impaired skin barrier function or dry skin in general at 3 months of age, but increased the risk for eczema, and for dry skin on the trunk and extensor limb surfaces at 3 and 6 months.
Asunto(s)
Dermatitis Atópica , Eccema , Proteínas Filagrina/genética , Dermatitis Atópica/genética , Eccema/genética , Genotipo , Humanos , Lactante , Proteínas de Filamentos Intermediarios/genética , Proteínas de Filamentos Intermediarios/metabolismo , Mutación/genética , Piel/metabolismoRESUMEN
We combine powder neutron diffraction, magnetometry and 57Fe Mössbauer spectrometry to determine the nuclear and magnetic structures of a strongly interacting weberite-type inorganic-organic hybrid fluoride, Fe2F5(H taz). In this structure, Fe2+ and Fe3+ cations form magnetically frustrated hexagonal tungsten bronze layers of corner-sharing octahedra. Our powder neutron diffraction data reveal that, unlike its purely inorganic fluoride weberite counterparts which adopt a centrosymmetric Imma structure, the room-temperature nuclear structure of Fe2F5(H taz) is best described by a non-centrosymmetric Ima2 model with refined lattice parameters a = 9.1467(2) Å, b = 9.4641(2) Å and c = 7.4829(2) Å. Magnetic susceptibility and magnetization measurements reveal that strong antiferromagnetic exchange interactions prevail in Fe2F5(H taz) leading to a magnetic ordering transition at TN = 93 K. Analysis of low-temperature powder neutron diffraction data indicates that below TN, the Fe2+ sublattice is ferromagnetic, with a moment of 4.1(1) µB per Fe2+ at 2 K, but that an antiferromagnetic component of 0.6(3) µB cants the main ferromagnetic component of Fe3+, which aligns antiferromagnetically to the Fe2+ sublattice. The zero-field and in-field Mössbauer spectra give clear evidence of an excess of high-spin Fe3+ species within the structure and a non-collinear magnetic structure. This article is part of the theme issue 'Mineralomimesis: natural and synthetic frameworks in science and technology'.
RESUMEN
OBJECTIVES: As a replacement for traditional phone booths, LinkNYC kiosks provide the ability to make free calls, connect to WiFi, and to charge electronic devices. These structures, which are supported by advertising revenue, are found in growing numbers on the streets of New York City (NYC). The purpose of this study was to determine the prevalence of sugar-sweetened beverage advertisements on LinkNYC kiosks. STUDY DESIGN: Cross-sectional, observational. METHODS: A total of 100 kiosks from a sample of 507 kiosks were randomly selected and observed in Manhattan, NYC. RESULTS: A total of 2025 advertisements, including duplicates, were observed that included 347 (17.1%) viewed at 64 kiosks for non-alcoholic beverages. Over half (n = 206, 59.4%) featured beverages with added sugar. For the 206 beverages with sugar, the mean kilocalories and grams of sugar per serving were 149.90 (SD = 64.95, range = 90-300) and 35.04 (SD = 19.54, range = 17-81), respectively. Differences in the frequency of these 206 advertisements were examined by the median annual income quartile of the census tract where the kiosk was located, and no significant differences were observed, χ2 (3, N = 206) = 3.09, P = 0.38. CONCLUSIONS: As the NYC Department of Health and Mental Hygiene invests in efforts to reduce consumption of sugar-sweetened beverages, promoting these very products through new media controlled by the City does not seem well aligned with the goal of improving dietary intake of citizens.
Asunto(s)
Publicidad/estadística & datos numéricos , Bebidas , Edulcorantes , Estudios Transversales , Sacarosa en la Dieta/administración & dosificación , Humanos , Ciudad de Nueva YorkRESUMEN
Eleven pregnant pony mares (D270-326) were administered ceftiofur sodium intramuscularly at 2.2 mg/kg (n = 6) or 4.4 mg/kg (n = 5), once daily. Plasma was obtained prior to ceftiofur administration and at 0.5, 1, 2, 4, 8, 12, and 24 hr after administration. Eight pony mares were re-enrolled in the study at least 3 days from expected foaling to ensure steady-state concentrations of drug at the time of foaling. Mares were administered ceftiofur sodium (4.4 mg/kg, IM) daily until foaling. Parturition was induced using oxytocin 1 hr after ceftiofur sodium administration. Allantoic and amniotic fluid, plasma, and colostrum samples were collected at time of foaling. Serial foal plasma samples were obtained. Placental tissues were collected. Desfuroylceftiofur acetamide (DCA) concentrations were measured in samples by high-performance liquid chromatography (HPLC). Mean (±SD) peak serum concentrations of DCA were 3.97 ± 0.50 µg/ml (low dose) and 7.45 ± 1.05 µg/ml (high dose). Terminal half-life was significantly (p = .014) shorter after administration of the low dose (2.91 ± 0.59 hr) than after administration of the high dose (4.10 ± 0.72 hr). The mean serum concentration of DCA from mares at time of foaling was 7.96 ± 1.39 µg/ml. The mean DCA concentration in colostrum was 1.39 ± 0.70 µg/ml. DCA concentrations in allantoic fluid, amniotic fluid, placental tissues, and foal plasma were below the limit of quantification (<0.1 µg/ml) and below the minimum inhibitory concentration of ceftiofur against relevant pathogens. These results infer incomplete passage of DCA across fetal membranes after administration of ceftiofur sodium to normal pony mares.
Asunto(s)
Antibacterianos/farmacocinética , Cefalosporinas/farmacocinética , Alantoides/química , Líquido Amniótico/química , Animales , Antibacterianos/administración & dosificación , Antibacterianos/análisis , Antibacterianos/sangre , Cefalosporinas/administración & dosificación , Cefalosporinas/análisis , Cefalosporinas/sangre , Calostro/química , Femenino , Feto/química , Semivida , Caballos/metabolismo , Inyecciones Intramusculares/veterinaria , Trabajo de Parto Inducido/veterinaria , Placenta/química , Embarazo/metabolismoRESUMEN
A compact system is developed to measure laser absorptivity for a variety of powder materials (metals, ceramics, etc.) with different powder size distributions and thicknesses. The measured results for several metal powders are presented. The results are consistent with those from ray tracing calculations.
RESUMEN
BACKGROUND: Rituximab-hyper-CVAD alternating with rituximab-high-dose methotrexate and cytarabine is a commonly utilized regimen in the United States for mantle cell lymphoma (MCL) based on phase II single institutional data. To confirm the clinical efficacy of this regimen and determine its feasibility in a multicenter study that includes both academic and community-based practices, a phase II study of this regimen was conducted by SWOG. PATIENTS AND METHODS: Forty-nine patients with advanced stage, previously untreated MCL were eligible. The median age was 57.4 years (35-69.8 years). RESULTS: Nineteen patients (39%) did not complete the full scheduled course of treatment due to toxicity. There was one treatment-related death and two cases of secondary myelodysplastic syndrome (MDS). There were 10 episodes of grade 3 febrile neutropenia, 19 episodes of grade 3 and 1 episode of grade 4 infection. With a median follow-up of 4.8 years, the median progression-free survival was 4.8 years (5.5 years for those ≤ 65 years) and the median overall survival (OS) was 6.8 years. CONCLUSIONS: Although this regimen is toxic, it is active for patients ≤ 65 years of age and can be given both at academic centers and in experienced community centers.
Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/administración & dosificación , Linfoma de Células del Manto/tratamiento farmacológico , Linfoma de Células del Manto/patología , Adulto , Anciano , Anticuerpos Monoclonales de Origen Murino/administración & dosificación , Ciclofosfamida/administración & dosificación , Citarabina/administración & dosificación , Dexametasona/administración & dosificación , Doxorrubicina/administración & dosificación , Femenino , Estudios de Seguimiento , Humanos , Linfoma de Células del Manto/mortalidad , Masculino , Metotrexato/administración & dosificación , Persona de Mediana Edad , Rituximab , Tasa de Supervivencia/tendencias , Resultado del Tratamiento , Vincristina/administración & dosificaciónRESUMEN
In genetic association studies, it is typically thought that genetic variants and environmental variables jointly will explain more of the inheritance of a phenotype than either of these two components separately. Traditional methods to identify gene-environment interactions typically consider only one measured environmental variable at a time. However, in practice, multiple environmental factors may each be imprecise surrogates for the underlying physiological process that actually interacts with the genetic factors. In this paper, we develop a variant of L(2) boosting that is specifically designed to identify combinations of environmental variables that jointly modify the effect of a gene on a phenotype. Because the effect modifiers might have a small signal compared with the main effects, working in a space that is orthogonal to the main predictors allows us to focus on the interaction space. In a simulation study that investigates some plausible underlying model assumptions, our method outperforms the least absolute shrinkage and selection and Akaike Information Criterion and Bayesian Information Criterion model selection procedures as having the lowest test error. In an example for the Women's Health Initiative-Population Architecture using Genomics and Epidemiology study, the dedicated boosting method was able to pick out two single-nucleotide polymorphisms for which effect modification appears present. The performance was evaluated on an independent test set, and the results are promising.
Asunto(s)
Teorema de Bayes , Interacción Gen-Ambiente , Estudios de Asociación Genética , Polimorfismo de Nucleótido Simple , Salud de la Mujer , Ensayos Clínicos como Asunto , Demografía , Femenino , Humanos , Fenotipo , Estados Unidos/epidemiologíaRESUMEN
PURPOSE: The Southwest Oncology Group (SWOG) coordinated an Intergroup study with the participation of Radiation Therapy Oncology Group (RTOG), and Eastern Cooperative Oncology Group (ECOG). This randomized phase III trial compared chemoradiotherapy versus radiotherapy alone in patients with nasopharyngeal cancers. MATERIALS AND METHODS: Radiotherapy was administered in both arms: 1.8- to 2.0-Gy/d fractions Monday to Friday for 35 to 39 fractions for a total dose of 70 Gy. The investigational arm received chemotherapy with cisplatin 100 mg/m2 on days 1, 22, and 43 during radiotherapy; postradiotherapy, chemotherapy with cisplatin 80 mg/m2 on day 1 and fluorouracil 1,000 mg/m2/d on days 1 to 4 was administered every 4 weeks for three courses. Patients were stratified by tumor stage, nodal stage, performance status, and histology. RESULTS: Of 193 patients registered, 147 (69 radiotherapy and 78 chemoradiotherapy) were eligible for primary analysis for survival and toxicity. The median progression-free survival (PFS) time was 15 months for eligible patients on the radiotherapy arm and was not reached for the chemo-radiotherapy group. The 3-year PFS rate was 24% versus 69%, respectively (P < .001). The median survival time was 34 months for the radiotherapy group and not reached for the chemo-radiotherapy group, and the 3-year survival rate was 47% versus 78%, respectively (P = .005). One hundred eighty-five patients were included in a secondary analysis for survival. The 3-year survival rate for patients randomized to radiotherapy was 46%, and for the chemoradiotherapy group was 76% (P < .001). CONCLUSION: We conclude that chemoradiotherapy is superior to radiotherapy alone for patients with advanced nasopharyngeal cancers with respect to PFS and overall survival.
RESUMEN
Understanding recharge in the Mekong Delta is critical for the delta's groundwater resources, and requires the investigation of recharge processes at the local scale. In this study of the north eastern area of the Mekong Delta, time-series of environmental tracer data (δ18O, δ2H, major ions and 3H) and markers of rural pollution (NH4 and NO3) were used to highlight localized recharge and impacts on groundwater quality. Results highlighted new hydrological insights into recharge processes, including that the Pleistocene aquifer receives recent recharge (< 60 years), predominantly during high rainfall months (> 100 mm/month). However, due to shallow clay layers there are significant spatial variations in these recharge processes, which were observed in the seasonal fluctuation of groundwater δ18O values in groundwater. Wet season δ18O changes ranged from below analytical uncertainty (≤ 0.10 ) to up to 0.56 , and the calculated fraction of rainfall contribution to the aquifer is ≤5 % to 16 %. Rainfall recharge via the acrisol soils results in low groundwater EC (20-55 µS/cm), acidic groundwater (pH 3.6-5.6), and may also have resulted in the low groundwater NO3 concentrations (≤ 5.3 mg NO3/L) at many sites due to adsorption, therefore delaying not reducing NO3 contamination. Site specific variations in nitrogen processes includes increased NO3 (to 29.7 mg/L) from fertiliser transfers or nitrification, and increased NH4 (to 1.4 mg/L) likely due to the recharge of irrigation waters. Unlike other recharge areas across the northern Mekong Delta, this north-eastern region provides a groundwater resource unaffected by arsenic contamination. Therefore, these results should inform on priority areas for protection from further contamination by rural anthropogenic activities.
Asunto(s)
Agua Subterránea , Contaminantes Químicos del Agua , Monitoreo del Ambiente/métodos , Nitratos/análisis , Nitrógeno , Contaminantes Químicos del Agua/análisisRESUMEN
A new generation UV absorber is obtained by microwave-heating-assisted hydrothermal synthesis: [Hgua](2)·(Ti(5)O(5)F(12)). The structure of this hybrid titanium(IV) oxyfluoride is ab initio determined from powder X-ray data by combining a direct space method, Rietveld refinement [orthorhombic, Cmm2, a = 22.410(1) Å, b = 11.191(1) Å, c = 3.802(1) Å], and density functional theory geometry optimization. The three-dimensional network is built up from infinite inorganic layers (∞)(Ti(5)O(5)F(12)) separated by guanidinium cations. The theoretical optical gap (3.2 eV) estimated from density of state calculations is in good agreement with the experimental gap (3.3 eV) obtained by UV-vis diffuse reflectivity. The optical absorption is mainly due to O(2p) â Ti(3d) and F(2p) â Ti(3d) transitions at higher energies. The refraction index is low in the visible range (n ≈ 1.9) compared to that of TiO(2) and, consequently, [Hgua](2)·(Ti(5)O(5)F(12)) shows a good transparency adapted to UV shielding. Under UV irradiation at 254 nm for 40 h, the white microcrystalline powder turns to light purple-gray. This color change is caused by the reduction of Ti(IV) to Ti(III), confirmed by magnetic measurements.
RESUMEN
Mediterranean peatlands remain largely under-documented, except for detailed biological data such as fauna and flora taxa lists, and yet are increasingly threatened by water withdrawal and agriculture practices. This lack of information, particularly on their hydrogeological functioning, makes it impossible to evaluate their response to changing climate conditions. A pilot study on a representative Mediterranean peatland on the island of Corsica (France) was conducted to evaluate recharge modalities in the peatland using a coupled water-level monitoring, geochemical and isotope multi-tracing approach (electric conductivity, major ions, δ18O, δ2H, 3H, 87Sr/86Sr). The goal was to understand how water budgets in peatland ecosystems were maintained throughout the year, especially during the summer. Despite the remarkable stability of the peatland water level, the recharge contributions of varied water bodies through an alluvial aquifer vary significantly from one season to another. An end-member mixing analysis (EMMA) indicates that the peatland is mainly recharged by an alluvial aquifer. During fall-winter, the alluvial aquifer on which the peatland depends is recharged by the rainfall, a river, and shallow groundwater (colluvium). During spring-summer, water supply is provided mostly by a river, shallow, and deep groundwater (fractured granite). However, this specific hydrogeological functioning is not taken into account by environmental management policies making peatlands vulnerable to anthropogenic and climatic pressures. Thus, their actual status regarding water and aquatic environment management policies is discussed to provide recommendations for better consideration and preservation.
RESUMEN
BACKGROUND: The purpose was to examine the prognostic impact of features of tumor cells and immune microenvironment in patients with follicular lymphoma treated with and without anti-CD20 monoclonal antibody therapy. PATIENTS AND METHODS: Tissue microarrays were constructed from archived tissue obtained from patients on three sequential Southwest Oncology Group (SWOG) trials for FL. All three trials included anthracycline-based chemotherapy. Anti-CD20 monoclonal antibodies were included for patients in the latter two trials. Immunohistochemistry was used to study the number and distribution of cells staining for forkhead box protein P3 (FOXP3) and lymphoma-associated macrophages (LAMs) and the number of lymphoma cells staining for myeloma-associated antigen-1 (MUM-1). Cox proportional hazards regression was used to evaluate the association between marker expression and overall survival (OS). RESULTS: The number or pattern of infiltrating FOXP3 cells and LAMs did not correlate with OS in sequential SWOG studies for FL. The presence of MUM-1 correlated with lower OS for patients who received monoclonal antibody but not for those treated with chemotherapy alone. CONCLUSIONS: Immune cell composition of lymph nodes did not correlate with OS in this analysis of trials in FL. The mechanism of the observed correlation between MUM-1 expression and adverse prognosis in patients receiving monoclonal antibody therapy requires confirmation.
Asunto(s)
Anticuerpos Monoclonales/uso terapéutico , Factores Reguladores del Interferón/metabolismo , Linfoma Folicular/diagnóstico , Linfoma Folicular/terapia , Macrófagos/patología , Linfocitos T Reguladores/patología , Adulto , Anciano , Recuento de Células Sanguíneas , Ensayos Clínicos Fase II como Asunto , Terapia Combinada , Femenino , Humanos , Inmunoterapia/métodos , Linfoma Folicular/inmunología , Linfoma Folicular/metabolismo , Macrófagos/metabolismo , Masculino , Oncología Médica/métodos , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Pronóstico , Ensayos Clínicos Controlados Aleatorios como Asunto , Sudoeste de Estados Unidos , Linfocitos T Reguladores/efectos de los fármacos , Linfocitos T Reguladores/metabolismoRESUMEN
CONTENTS: Rapid physical uterine clearance is paramount for fertility. Mares that are unable to clear the by-products of insemination or foaling quickly may develop post-mating-induced or acute endometritis. If endometritis is not promptly resolved, the infection can become chronic. Endometritis can be difficult to identify because clinical signs, ultrasonographic and laboratory findings can vary between uterine pathogens. Some micro-organisms are associated with an influx of neutrophils and fluid into the uterine lumen while others are associated with only heavy debris on cytological specimens. Identifying the inciting cause may require more than swabbing the endometrium. Culturing endometrial biopsy tissue or uterine fluids are more sensitive methods for identifying Escherichia coli than culture swab while endometrial cytology identifies twice as many mares with acute inflammation than uterine culture swab. While post-mating-induced endometritis is classically treated with uterine irrigation and ecbolics and acute endometritis is treated with either systemic or intra-uterine antibiotics, these therapies are not always effective in resolving chronic uterine inflammation or infections. Mucolytics can be used to break up mucus produced by an irritated endometrium, steroids can modulate the inflammatory response associated with insemination and buffered chelating agents can remove biofilm, a protective mechanism used primarily by gram-negative organisms and yeast to evade the host immune response.
Asunto(s)
Infecciones Bacterianas/veterinaria , Cruzamiento , Endometritis/veterinaria , Enfermedades de los Caballos/diagnóstico , Enfermedades de los Caballos/terapia , Micosis/veterinaria , Animales , Antibacterianos/administración & dosificación , Antiinflamatorios/administración & dosificación , Infecciones Bacterianas/terapia , Biopelículas , Quelantes/administración & dosificación , Enfermedad Crónica , Endometritis/diagnóstico , Endometritis/terapia , Expectorantes/uso terapéutico , Femenino , Enfermedades de los Caballos/etiología , Caballos , Micosis/terapia , Neutrófilos , Embarazo , Ultrasonografía/veterinaria , Útero/microbiología , Útero/patologíaRESUMEN
CONTENTS: Ascending placentitis is a common cause of premature birth, abortion and delivery of compromised, ill foals. Recent experimental models have investigated diagnostic procedures and treatment strategies in an attempt to improve live foal rate. Diagnostics such as transrectal and transabdominal ultrasonography are used to evaluate foetal well-being and placental separation, while measurement of plasma progestins or oestrogen identifies a stressed or hypoxic foetus. Treatment is directed at stopping spread of infection, maintaining uterine quiescence and blocking production of pro-inflammatory cytokines. It must be instituted early if a pregnancy is to be saved. Treatments include antibiotics, tocolytics and immunomodulators. Prompt, aggressive treatment with antibiotics has improved foal viability in experimental models of placentitis.
Asunto(s)
Infecciones Bacterianas/veterinaria , Enfermedades de los Caballos/diagnóstico , Enfermedades de los Caballos/tratamiento farmacológico , Enfermedades Placentarias/veterinaria , Animales , Antibacterianos/administración & dosificación , Antiinflamatorios/administración & dosificación , Infecciones Bacterianas/diagnóstico , Infecciones Bacterianas/tratamiento farmacológico , Estrógenos/fisiología , Femenino , Enfermedades de los Caballos/microbiología , Caballos , Hidrocortisona/fisiología , Enfermedades Placentarias/diagnóstico , Enfermedades Placentarias/tratamiento farmacológico , Embarazo , Nacimiento Prematuro/microbiología , Nacimiento Prematuro/prevención & control , Nacimiento Prematuro/veterinaria , Progestinas/fisiología , Prostaglandinas/fisiologíaRESUMEN
Crystals of two new 3D hybrid compounds, trans-Zn3TiF7(H2O)2(taz)3·3H2O and cis-Zn3TiF7(H2O)2(taz)3·C2H5OH, have been obtained by solvothermal synthesis ((taz)- = 1,2,4-triazolate C2H2N3 ligand). Their structures, determined from X-ray single crystal diffraction data in Cm and Pnma space groups, respectively, are based on Zn3N9(H2O)2F3 trimers linked by TiF6 octahedra that build trans- or cis-chains ∞[Zn3TiN9(H2O)2F7]. Water or ethanol in the structure cavities is released below 110 °C to give trans- or cis-Zn3TiF7(H2O)2(taz)3 and, on further heating, these intermediate phases dehydrate and lead to anhydrous trans- or cis-Zn3TiF7(taz)3. At 110 °C, the loss of ethanol concerns only ≈1/3 of the weight of cis-Zn3TiF7(H2O)2(taz)3·C2H5OH while the remaining part subsists up to 180 °C. This behaviour is attributed to a core-shell type configuration. Rehydration in humid air occurs at room temperature for the anhydrous cis-phase. All desolvated, dehydrated or rehydrated phase structures have been determined by X-ray powder diffraction and ab initio Rietveld refinements. All transformations from solvated or hydrated to anhydrous phases are realised without any symmetry change and the trans or cis connection of the TiF6 octahedra is maintained together with the overall features of the 3D networks. The final loss of water molecules induces a condensation reaction that implies the connection of the trimers by fluorine atoms; the structures of the anhydrous phases Zn3TiF7(taz)3 are then described by Zn3N9F4 trimers. 1H and 19F MAS NMR studies, coupled with DFT calculations of NMR parameters, confirm the water loss and support the strutural models while evidencing both the positional disorders, more likely of the organic parts, and the F motions within TiF6 octahedra.
RESUMEN
Similar to many southern and southeast Asian regions, the mobilisation of arsenic (As) from sediments has driven a widespread contamination problem for groundwater resources in the Cambodian Mekong Delta. For the first time, the seasonal changes in As concentrations and potential links to groundwater pumping for irrigation in shallow aquifers of the Cambodian Mekong Delta are investigated. Using environmental tracers (δ18O, δ2H, 3H, major/trace ions and rare earth elements) the natural and pumping-induced changes in hydrogeological processes are identified. Three conceptual models are proposed: Model 1, where there is limited local recharge or low recharge rates (3H mean residence time > 60 years) and groundwater has a large range in As concentrations (0.2 to 393.8 µg/L). In this semi-confined aquifer, only one of the six groundwater sites has As concentrations that increase (by 10.9 µg/L) potentially due to groundwater pumping and resultant mixing with high-As and low (Pr/Sm)NASC groundwater. However, data on groundwater extraction volumes is required to verify the link with irrigation practices. Model 2, where groundwater is recharged by evaporated surface waters (fractionated δ18O and δ2H). There are moderate As concentrations (64.1-106.1 µg/L) but no significant seasonal changes even though the recharging waters have relatively greater organic carbon contents during the dry season (reduced Ce/Ce*anomaly). Finally model 3, where groundwater is significantly recharged by wet season rainfall (~50% from δ18O data). There is a minor increase in As concentrations with recharge (by 6. µg/L). These combined results highlight an aquifer system in the irrigated region of the Cambodian Mekong Delta where As concentrations are largely impacted by natural rather than irrigation processes. Seasonal-scale recharge processes control As processes where the aquifer is not confined by shallow clay layers, and where the aquifer is semi-confined As concentrations largely reflect longer-term natural processes.