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1.
Environ Sci Technol ; 58(40): 17926-17936, 2024 Oct 08.
Artículo en Inglés | MEDLINE | ID: mdl-39319827

RESUMEN

Per- and polyfluoroalkyl substances (PFAS) are known to be highly persistent in groundwater, making it vital to develop new approaches to important practical questions such as the time scale for future persistence of PFAS in contaminated groundwater. In the approach presented here, groundwater from beneath streambeds was analyzed for PFAS and age-dated using SF6 and 3H/3He. The results were coupled with groundwater flux measurements in a convolution approach to estimate past and future PFAS concentrations in groundwater discharge to the streams. At our test site near the Cape Fear River (CFR) of North Carolina, PFAS were detected in groundwater up to 43 years old, suggesting that some PFAS entered groundwater immediately or shortly after fluorochemical production began at the nearby Fayetteville Works. Results are consistent with little to no retardation in groundwater for perfluoroethers such as hexafluoropropylene oxide-dimer acid (HFPO-DA) and perfluoro-2-methoxypropanoic acid (PMPA), the two most abundant PFAS, with mean concentrations of 229 and 498 ng/L, respectively. Future PFAS concentrations in groundwater discharge to streams were estimated to remain above current MCL or health advisory levels through at least 2050 or 2060 (using 3H/3He and SF6, respectively). Recent atmospheric deposition data suggest lower but non-negligible amounts of PFAS may continue to enter groundwater, likely further extending PFAS persistence in groundwater and the adjacent CFR. This approach shows promise for giving an overall perspective on persistence of PFAS in groundwater discharge from a broad contaminated area.


Asunto(s)
Monitoreo del Ambiente , Fluorocarburos , Agua Subterránea , Ríos , Contaminantes Químicos del Agua , Agua Subterránea/química , Contaminantes Químicos del Agua/análisis , Fluorocarburos/análisis , Ríos/química , North Carolina , Predicción
2.
Chemphyschem ; 20(10): 1301-1304, 2019 05 16.
Artículo en Inglés | MEDLINE | ID: mdl-30843647

RESUMEN

Modification of magnesium diboride, MgB2 , by mechanical milling with THF, MgH2 , and/or Mg results in a lowering of the conditions required for its direct, bulk hydrogenation to magnesium borohydride, Mg(BH4 )2 , by 300 bar and 100 °C. Following mechanical milling with MgH2 or THF and Mg, MgB2 can be hydrogenated to Mg(BH4 )2 at 300 °C under 700 bar of H2 while achieving ∼54-71 % conversion to the borohydride. The discovery of a means of dramatically lowering the conditions required for the hydrogenation of MgB2 is an important step towards the development of a practical onboard hydrogen storage system based on hydrogen cycling between Mg(BH4 )2 and MgB2 . We suggest that mechano-milling with THF, Mg, and/or MgH2 may possibly introduce defects in the MgB2 structure which enhance hydrogenation. The ability to activate the MgB2 through the introduction of structural defects transcends its relevance to hydrogen storage, as a method of overcoming its chemical inertness provides the key to harnessing other interesting properties of this material.

3.
Phys Chem Chem Phys ; 22(1): 368-378, 2019 Dec 18.
Artículo en Inglés | MEDLINE | ID: mdl-31819933

RESUMEN

Metal borohydrides are considered promising materials for hydrogen storage applications due to their high volumetric and gravimetric hydrogen density. Recently, different Lewis bases have been complexed with Mg(BH4)2 in efforts to improve hydrogenation/dehydrogenation properties. Notably, Mg(BH4)2·xTHF adducts involving tetrahydrofuran (THF; C4H8O) have proven to be especially interesting. This work focuses on exploring the physicochemical properties of the THF-rich Mg(BH4)2·3THF adduct using neutron-scattering methods and molecular DFT calculations. Structural analysis, based on neutron diffraction measurements of Mg(11BH4)2·3TDF (D - deuterium), has confirmed a lowering of the symmetry upon cooling, from monoclinic C2/c to P1[combining macron] via a triclinic distortion. Vibrational properties are strongly influenced by the THF environment, showing a splitting in spectral features as a result of changes in the bond lengths, force constants, and lowering of the overall symmetry. Interestingly, the orientational mobilities of the BH4- anions obtained from quasielastic neutron scattering (QENS) are not particularly sensitive to the presence of THF and compare well with the mobilities of BH4- anions in unsolvated Mg(BH4)2. The QENS data point to uniaxial 180° jump reorientations of the BH4- anions around a preferred C2 anion symmetry axis. The THF rings are also found to be orientationally mobile, undergoing 180° reorientational jumps around their C2 molecular symmetry axis with jump frequencies about an order of magnitude lower than those for the BH4- anions. In contrast, no dynamical behavior of the THF rings is observed with QENS for a more THF-deficient 2Mg(BH4)2·THF adduct. This lack of comparable THF mobility may reflect a stronger Mg2+-THF bonding interaction for lower THF/Mg(BH4)2 stoichiometric ratios, which is consistent with DFT calculations showing a decrease in the binding energy with each additional THF ring in the adduct. Based on the combined experimental and computational results, we propose that combining THF and Mg(BH4)2 is beneficial to (i) preventing weakly bound THF from coming free from the Mg2+ cation and reducing the concentration of any unwanted impurity in the hydrogen and (ii) disrupting the stability of the crystalline phase, leading to a lower melting point and enhanced kinetics for any potential hydrogen storage applications.

4.
J Pediatr Gastroenterol Nutr ; 66(4): 620-623, 2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-28991840

RESUMEN

OBJECTIVES: Differentiating ulcerative colitis (UC) and Crohn disease (CD) can be clinically challenging, especially in children. Granulomatous inflammation has traditionally been attributed to CD. Crypt-associated giant cells and granulomas, however, have been observed in colonic biopsies of patients with UC. This phenomenon has not been described in the upper gastrointestinal (UGI) tract with UC. METHODS: Seven pediatric patients with UC with granulomatous UGI (gUGI) lesions were identified. Diagnosis of UC was based on symptoms, clinical course, laboratory results, imaging, and endoscopy. We compared the gUGI patients to a large cohort of pediatric patients with UC (n = 149). RESULTS: All fully evaluated cases were associated with bloody diarrhea and moderate to severe pancolitis. Gastric and/or duodenal biopsies demonstrated giant cells or granulomas near gland destruction. Small bowel imaging did not reveal any involvement. The majority of cases responded to standard medical therapies, except for 2 patients (28.6%) who required total colectomy. Acute severe, refractory colitis (ie, colectomy within 1 month of presentation) was significantly more common in the gUGI group than the large pediatric UC group (28.6% vs 1.3%, Fisher exact P = 0.01). CONCLUSIONS: This is the first report of pediatric UC-associated granulomatous inflammation in the UGI tract. We speculate that these lesions represent extracolonic manifestations of intense colonic disease. These atypical findings expand the diagnostic considerations that should be incorporated during the differentiation between UC and CD in the pediatric age group.


Asunto(s)
Colitis Ulcerosa/patología , Granuloma/patología , Tracto Gastrointestinal Superior/patología , Adolescente , Niño , Preescolar , Colectomía/estadística & datos numéricos , Colitis Ulcerosa/cirugía , Femenino , Granuloma/cirugía , Humanos , Masculino , Estudios Retrospectivos
5.
Inorg Chem ; 54(8): 4120-5, 2015 Apr 20.
Artículo en Inglés | MEDLINE | ID: mdl-25815415

RESUMEN

Mg(B3H8)2·2THF (THF = tetrahydrofuran) was prepared by the addition of BH3·THF to Mg/Hg amalgam. Heating a 1:2 molar mixture of Mg(B3H8)2·2THF and MgH2 to 200 °C under 5 MPa H2 for 2 h leads to nearly quantitative conversion to Mg(BH4)2. The differential scanning calorimetry profile of the reaction measured under 5 MPa H2 shows an initial endothermic feature at ∼65 °C for a phase change of the compound followed by a broad exothermic feature that reaches a maximum at 130 °C corresponding to the hydrogenation of Mg(B3H8)2 to Mg(BH4)2. Heating Mg(B3H8)2·2THF to 200 °C under 5 MPa H2 pressure in the absence of MgH2 gives predominantly MgB12H12 as well as significant amounts of MgB10H10 and Mg(BH4)2. Hydrogenation of a mixture of Mg(B3H8)2·2THF and LiH in a 1:4 molar ratio at 130 °C under 5 MPa H2 yields [B12H12](2-) in addition to [BH4](-), while a 1:4 molar ratio of Mg(B3H8)2·2THF and NaH yields [BH4](-) and a new borane, likely [B2H7](-). Hydrogenation of the NaH-containing mixture at 130 °C gives primarily the alternative borane, indicating it is an intermediate in the two-step conversion of the triborane to [BH4](-). The solvent-free triborane Mg(B3H8)2, derived from the low-temperature dehydrogenation of Mg(BH4)2, also produces Mg(BH4)2, but higher temperature and pressure is required to effect the complete transformation of the Mg(B3H8)2. These results show that the reversible transformation of the triborane depends on the stability of the metal hydride. The more stable the metal hydride, that is, LiH > NaH > MgH2, the lower is the "regeneration" efficiency.

6.
J Pediatr Gastroenterol Nutr ; 58(6): 715-22, 2014 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-24345834

RESUMEN

OBJECTIVE: The aim of the study was to determine whether docosahexaenoic acid (DHA) supplementation improves the behavior of children with autism. METHODS: A group of 3- to 10-year-old children with autism were randomized in a double-blind fashion to receive a supplement containing 200 mg of DHA or a placebo for 6 months. The parents and the investigator completed the Clinical Global Impressions-Improvement scale to rate changes in core symptoms of autism after 3 and 6 months. The parents completed the Child Development Inventory and the Aberrant Behavior Checklist, and both parents and teachers completed the Behavior Assessment Scale for Children (BASC) at enrollment and after 6 months. RESULTS: A total of 48 children (40 [83%] boys, mean age [standard deviation] 6.1 [2.0] years) were enrolled; 24 received DHA and 24 placebo. Despite a median 431% increase in total plasma DHA levels after 6 months, the DHA group was not rated as improved in core symptoms of autism compared to the placebo group on the CGI-I. Based on the analysis of covariance models adjusted for the baseline rating scores, parents (but not teachers) provided a higher average rating of social skills on the BASC for the children in the placebo group compared to the DHA group (P = 0.04), and teachers (but not parents) provided a higher average rating of functional communication on the BASC for the children in the DHA group compared to the placebo group (P = 0.02). CONCLUSIONS: Dietary DHA supplementation of 200 mg/day for 6 months does not improve the core symptoms of autism. Our results may have been limited by inadequate sample size.


Asunto(s)
Trastorno Autístico , Conducta Infantil , Comunicación , Suplementos Dietéticos , Ácidos Docosahexaenoicos , Habilidades Sociales , Trastorno Autístico/tratamiento farmacológico , Niño , Preescolar , Dieta , Ácidos Docosahexaenoicos/sangre , Ácidos Docosahexaenoicos/uso terapéutico , Método Doble Ciego , Femenino , Humanos , Masculino , Padres
7.
Phys Chem Chem Phys ; 15(17): 6179-81, 2013 May 07.
Artículo en Inglés | MEDLINE | ID: mdl-23519072

RESUMEN

The direct synthesis of NaAlH4 has been studied, for the first time, by in situ (27)Al and (23)Na wide-line NMR spectroscopy using high pressure NMR apparatus. Na3AlH6 formation is observed within two minutes of hydrogen addition, while NaAlH4 is detected after a total of four minutes. This indicates the formation of the hexahydride does not proceed to completion before the formation of the tetrahydride ensues.


Asunto(s)
Compuestos de Aluminio/síntesis química , Compuestos de Sodio/síntesis química , Aluminio/química , Compuestos de Aluminio/química , Espectroscopía de Resonancia Magnética , Presión , Sodio/química , Compuestos de Sodio/química
8.
J Appl Res Intellect Disabil ; 25(3): 282-7, 2012 May.
Artículo en Inglés | MEDLINE | ID: mdl-22489039

RESUMEN

BACKGROUND: Using mechanical restraints to protect a person who engaged in dangerous self-injury was decreased by manipulation of an establishing operation involving the client choosing the staff person who would work with her. MATERIALS AND METHODS: The client was a 28-year-old woman diagnosed with autism, bipolar disorder, static cerebral encephalopathy, moderate intellectual disabilities, hypotonia and musculoskeletal deformities. She had a history of biting herself and further bites could produce irreversible nerve damage. Mechanical restraints were applied when she bit, tried to bite herself or asked for them. RESULTS: When she was allowed to choose staff members, the use of mechanical restraint decreased. CONCLUSION: Reducing the time spent in mechanical restraint by giving the client a choice of staff members who would work with her demonstrates that such a choice may be an establishing operation. The usefulness of cumulative records and scatterplots to evaluate changes in the occurrence of self-injurious behaviour (SIB) and associated mechanical restraint is shown as are the advantages of using alternating treatment designs to assess the effectiveness of treatment conditions for someone who exhibits long-term cyclic behaviour.


Asunto(s)
Cuidadores/psicología , Trastornos Mentales/enfermería , Restricción Física/métodos , Conducta Autodestructiva/fisiopatología , Adulto , Trastorno Autístico/enfermería , Trastorno Autístico/psicología , Trastorno Bipolar/enfermería , Trastorno Bipolar/psicología , Epilepsia/enfermería , Epilepsia/psicología , Femenino , Humanos , Discapacidad Intelectual/enfermería , Discapacidad Intelectual/psicología , Trastornos Mentales/psicología , Hipotonía Muscular/enfermería , Anomalías Musculoesqueléticas/enfermería , Conducta Autodestructiva/enfermería
9.
J Am Chem Soc ; 133(39): 15593-7, 2011 Oct 05.
Artículo en Inglés | MEDLINE | ID: mdl-21863886

RESUMEN

The direct synthesis of LiAlH(4) from commercially available LiH and Al powders in the presence of TiCl(3) and Me(2)O has been achieved for the first time. The effects of TiCl(3) loadings (Ti/Al = 0, 0.01, 0.05, 0.2, 0.5, 1.0 and 2.0%) and various other additives (TiCl(3)/Al(2)O(3), metallic Ti, Nb(2)O(5), and NbCl(5)) on the formation and stability of LiAlH(4) have been systematically investigated. The yield of LiAlH(4) initially increases, and then decreases, with increasing TiCl(3) loadings. LiH + Al → LiAlH(4) yields above 95% were obtained when the molar ratios of Ti/Al were 0.05 and 0.2%. In the presence of a very tiny amount of TiCl(3) (Ti/Al = 0.01%), LiAlH(4) is still generated, but the yield is lower. In the complete absence of TiCl(3), LiAlH(4) does not form. Addition of metallic Ti, Nb(2)O(5), and NbCl(5) to commercial LiH and Al does not result in the formation of LiAlH(4). Preliminary tests show that TiCl(3)-doped LiAlH(4) can be cycled, making it a suitable candidate for hydrogen storage.

10.
J Pediatr ; 157(6): 900-5, 2010 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-20655543

RESUMEN

OBJECTIVE: We previously reported better psychomotor development at 30 months of age in infants whose mothers received a docosahexaenoic acid (DHA) (22:6n-3) supplement for the first 4 months of lactation. We now assess neuropsychological and visual function of the same children at 5 years of age. STUDY DESIGN: Breastfeeding women were assigned to receive identical capsules containing either a high-DHA algal oil (∼200 mg/d of DHA) or a vegetable oil (containing no DHA) from delivery until 4 months postpartum. Primary outcome variables at 5 years of age were measures of gross and fine motor function, perceptual/visual-motor function, attention, executive function, verbal skills, and visual function of the recipient children at 5 years of age. RESULTS: There were no differences in visual function as assessed by the Bailey-Lovie acuity chart, transient visual evoked potential or sweep visual evoked potential testing between children whose mothers received DHA versus placebo. Children whose mothers received DHA versus placebo performed significantly better on the Sustained Attention Subscale of the Leiter International Performance Scale (46.5 ± 8.9 vs 41.9 ± 9.3, P < .008) but there were no statistically significant differences between groups on other neuropsychological domains. CONCLUSIONS: Five-year-old children whose mothers received modest DHA supplementation versus placebo for the first 4 months of breastfeeding performed better on a test of sustained attention. This, along with the previously reported better performance of the children of DHA-supplemented mothers on a test of psychomotor development at 30 months of age, suggests that DHA intake during early infancy confers long-term benefits on specific aspects of neurodevelopment.


Asunto(s)
Lactancia Materna , Desarrollo Infantil/efectos de los fármacos , Ácidos Docosahexaenoicos/uso terapéutico , Desempeño Psicomotor/efectos de los fármacos , Agudeza Visual/efectos de los fármacos , Preescolar , Femenino , Humanos , Masculino , Pruebas Neuropsicológicas , Embarazo , Atención Prenatal , Nacimiento a Término , Factores de Tiempo
11.
J Am Chem Soc ; 131(14): 5032-3, 2009 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-19296609

RESUMEN

LiH and Ti-doped Al react quantitatively with H(2) in Me(2)O solution to form LiAlH(4) under mild conditions. The solvent is easily vented along with excess H(2) on completion, leaving dry Ti-doped LiAlH(4); this releases approximately 7 wt % H(2) commencing at 80 degrees C with excellent kinetics.

12.
Nanotechnology ; 20(20): 204027, 2009 May 20.
Artículo en Inglés | MEDLINE | ID: mdl-19420675

RESUMEN

A new approach to the incorporation of MgH2 in the nanometer-sized pores of a carbon aerogel scaffold was developed, by infiltrating the aerogel with a solution of dibutylmagnesium (MgBu2) precursor, and then hydrogenating the incorporated MgBu2 to MgH2. The resulting impregnated material showed broad x-ray diffraction peaks of MgH2. The incorporated MgH2 was not visible using a transmission electron microscope, which indicated that the incorporated hydride was nanosized and confined in the nanoporous structure of the aerogel. The loading of MgH2 was determined as 15-17 wt%, of which 75% is reversible over ten cycles. Incorporated MgH2 had >5 times faster dehydrogenation kinetics than ball-milled activated MgH2, which may be attributed to the particle size of the former being smaller than that of the latter. Cycling tests of the incorporated MgH(2) showed that the dehydrogenation kinetics are unchanged over four cycles. Our results demonstrate that confinement of metal hydride materials in a nanoporous scaffold is an efficient way to avoid aggregation and improve cycling kinetics for hydrogen storage materials.


Asunto(s)
Carbono/química , Cristalización/métodos , Hidrógeno/química , Hidrógeno/aislamiento & purificación , Magnesio/química , Nanoestructuras/química , Nanoestructuras/ultraestructura , Aire , Gases/química , Geles/química , Sustancias Macromoleculares/química , Ensayo de Materiales , Conformación Molecular , Nanotecnología/métodos , Tamaño de la Partícula , Propiedades de Superficie
13.
J Phys Chem A ; 112(33): 7551-5, 2008 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-18665574

RESUMEN

LiSc(BH4)4 has been prepared by ball milling of LiBH4 and ScCl3. Vibrational spectroscopy indicates the presence of discrete Sc(BH4)4(-) ions. DFT calculations of this isolated complex ion confirm that it is a stable complex, and the calculated vibrational spectra agree well with the experimental ones. The four BH4(-) groups are oriented with a tilted plane of three hydrogen atoms directed to the central Sc ion, resulting in a global 8 + 4 coordination. The crystal structure obtained by high-resolution synchrotron powder diffraction reveals a tetragonal unit cell with a = 6.076 A and c = 12.034 A (space group P-42c). The local structure of the Sc(BH4)4(-) complex is refined as a distorted form of the theoretical structure. The Li ions are found to be disordered along the z axis.

14.
Congenit Heart Dis ; 13(1): 124-130, 2018 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-28924998

RESUMEN

OBJECTIVE: We describe the long-term follow-up of a child with recurrent hemoptysis due to severe pulmonary vein stenosis decompressing via collaterals to esophageal varices. DESIGN: Case report SETTING: Tertiary children's hospital PATIENT: Single child through ages 2- to 11-year old INTERVENTIONS: The child underwent cutting balloon angioplasty, bare metal stenting, and implantation of a PTFE-covered stent, all of which failed rapidly. Only after placement of a paclitaxel drug eluting stent did he have prolonged relief from hemoptysis and long-term patency of the treated vein. The stents were serially dilated to keep up with somatic growth of the child, eventually culminating in the need to induce intentional stent fracture. CONCLUSIONS: We highlight novel transcatheter techniques to treat this vexing condition, discuss mechanisms of disease treatment and progression, and present the only patient with this rare combination of lesions to have achieved both longstanding pulmonary vein patency and resolution of esophageal varices.


Asunto(s)
Angioplastia de Balón/métodos , Materiales Biocompatibles Revestidos , Circulación Colateral , Várices Esofágicas y Gástricas/cirugía , Paclitaxel/farmacología , Politetrafluoroetileno , Estenosis de Vena Pulmonar/cirugía , Antineoplásicos Fitogénicos/farmacología , Niño , Preescolar , Angiografía Coronaria , Stents Liberadores de Fármacos , Várices Esofágicas y Gástricas/complicaciones , Várices Esofágicas y Gástricas/diagnóstico , Femenino , Estudios de Seguimiento , Humanos , Lactante , Masculino , Estenosis de Vena Pulmonar/complicaciones , Estenosis de Vena Pulmonar/diagnóstico , Factores de Tiempo , Tomografía Computarizada por Rayos X , Resultado del Tratamiento
15.
Clin Pediatr (Phila) ; 46(6): 523-9, 2007 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-17579105

RESUMEN

To compare the validity of direct pediatric developmental evaluation with developmental screening by parent report, parents completed a developmental screen (the Child Development Review), a pediatrician performed a direct developmental evaluation (Capute Scales), and a psychologist administered the Bayley Scales of Infant Development to a group of 30-month-old children. The agreement between these instruments was tested. All developmental quotient scores derived from the Capute Scales were more highly correlated with concurrent Bayley Mental Development Index scores than developmental quotient scores derived from the Child Development Review. Differences between developmental quotient scores derived from the Capute Scales and corresponding Bayley Mental Development Index scores were significantly smaller than those derived from the Child Development Review. Thus, direct pediatric developmental evaluation more reliably predicted concurrent Mental Development Index scores at 30 months of age than developmental screening by parent report. Increased emphasis on training of pediatric health care providers in direct developmental evaluation should be considered.


Asunto(s)
Trastornos del Conocimiento/diagnóstico , Discapacidad Intelectual/diagnóstico , Trastornos del Lenguaje/diagnóstico , Madres/psicología , Desarrollo Infantil , Preescolar , Trastornos del Conocimiento/epidemiología , Estudios de Cohortes , Recolección de Datos/métodos , Femenino , Humanos , Discapacidad Intelectual/epidemiología , Trastornos del Lenguaje/epidemiología , Pruebas del Lenguaje , Masculino , Pruebas Neuropsicológicas , Pediatría , Desempeño Psicomotor/fisiología , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
16.
ACS Appl Mater Interfaces ; 9(18): 15502-15509, 2017 May 10.
Artículo en Inglés | MEDLINE | ID: mdl-28436647

RESUMEN

An effective route based on space-confined chemical reaction to synthesize uniform Li2Mg(NH)2 nanoparticles is reported. The hierarchical pores inside the one-dimensional carbon nanofibers (CNFs), induced by the creation of well-dispersed Li3N, serve as intelligent nanoreactors for the reaction of Li3N with Mg-containing precursors, resulting in the formation of uniformly discrete Li2Mg(NH)2 nanoparticles. The nanostructured Li2Mg(NH)2 particles inside the CNFs are capable of complete hydrogenation and dehydrogenation at a temperature as low as 105 °C with the suppression of ammonia release. Furthermore, by virtue of the nanosize effects and space-confinement by the porous carbon scaffold, no degradation was observed after 50 de/rehydrogenation cycles at a temperature as low as 130 °C for the as-prepared Li2Mg(NH)2 nanoparticles, indicating excellent reversibility. Moreover, the theoretical calculations demonstrate that the reduction in particle size could significantly enhance the H2 sorption of Li2Mg(NH)2 by decreasing the relative activation energy barrier, which agrees well with our experimental results. This method could represent an effective, general strategy for synthesizing nanoparticles of complex hydrides with stable reversibility and excellent hydrogen storage performance.

17.
Am J Clin Nutr ; 83(6 Suppl): 1452S-1457S, 2006 06.
Artículo en Inglés | MEDLINE | ID: mdl-16841854

RESUMEN

n-3 Fatty acids exert important effects on eicosanoid metabolism, membrane properties, and gene expression and therefore are biologically important nutrients. One n-3 fatty acid, docosahexaenoic acid, is an important component of neural and retinal membranes and accumulates rapidly in the brain and retina during the later part of gestation and early postnatal life. It is reasonable to hypothesize that maternal n-3 fatty acid intakes might have significant effects on several pregnancy outcomes as well as on subsequent infant visual function and neurodevelopmental status. Studies, both observational and interventional, assessing the influence of n-3 fatty acids during pregnancy or the early postpartum period on duration of gestation and infant size at birth, preeclampsia, depression, and infant visual function and neurodevelopment have been reported. n-3 Fatty acid intakes (both in terms of absolute amounts of docosahexaenoic acid and eicosapentaenoic acid and the ratio of these 2 fatty acids) varied widely in these studies, however, and no clear consensus exists regarding the effects of n-3 fatty acids on any of these outcomes. The available data suggest a modest effect of these fatty acids on increasing gestational duration and possibly enhancing infant neurodevelopment. Although data from earlier observational studies suggested a potential role of these fatty acids in decreasing the incidence of preeclampsia, this has not been confirmed in randomized, prospective trials. Because of the paucity of data from randomized, prospective, double-blind trials, the effect of n-3 fatty acids on depression during pregnancy or the early postpartum period remains unresolved.


Asunto(s)
Ácidos Grasos Omega-3/administración & dosificación , Recién Nacido/crecimiento & desarrollo , Lactancia/metabolismo , Fenómenos Fisiologicos Nutricionales Maternos , Fenómenos Fisiologicos de la Nutrición Prenatal , Encéfalo/efectos de los fármacos , Encéfalo/embriología , Encéfalo/crecimiento & desarrollo , Depresión Posparto/epidemiología , Ácidos Grasos Omega-3/farmacología , Femenino , Humanos , Lactante , Lactancia/efectos de los fármacos , Embarazo , Complicaciones del Embarazo/epidemiología , Resultado del Embarazo , Retina/efectos de los fármacos , Retina/embriología , Retina/crecimiento & desarrollo
18.
J Phys Chem B ; 110(6): 2740-5, 2006 Feb 16.
Artículo en Inglés | MEDLINE | ID: mdl-16471879

RESUMEN

NaAlH(4) with TiCl(3) and Al were mixed by ball-milling and cycled three times. The hydrogen storage properties were monitored during cycling, and the products were characterized by synchrotron X-ray diffraction. Because of the previously described formation of Al(1)(-)(y)Ti(y) with y approximately 0.15 during cycling that traps Al beyond the amount associated with the formation of NaCl, some Na(3)AlH(6) has no free Al to react with to form NaAlH(4). This was counteracted in the present work by adding a stoichiometric amount of Al that increases the theoretical storage capacity. Due to limitations in metal diffusion small amounts of Na(3)AlH(6) were still detected. When approximately 7 mol % more Al than the stoichiometric amount was added, the observed storage capacity increased significantly, and the Na(3)AlH(6) content was negligible after prolonged rehydrogenation. Cycled NaAlH(4) + 10 mol % TiCl(3) were desorbed to two different levels, and the diffraction patterns were compared. There is no change in unit-cell dimensions during desorption, and there is no sign of changes in the bulk composition of the Al(1)(-)(y)Ti(y) phase during a cycle. Adding pure Ti to a NaH + Al mixture by ball-milling in argon or hydrogen results in formation of TiH(2) that is stable during at least one cycle.

19.
J Phys Chem B ; 110(18): 9105-11, 2006 May 11.
Artículo en Inglés | MEDLINE | ID: mdl-16671722

RESUMEN

A systematic study of the dehydrogenation process of undoped and of catalyzed NaAlH4 by means of anelastic spectroscopy is presented. Evidence is reported of the formation of a highly mobile species during decomposition, which has been identified in off-stoichiometric AlH6-x units, giving rise to fast H vacancy local dynamics. The formation of such stoichiometry defects starts at temperatures much lower in Ti doped than in undoped samples, and concomitantly with the decomposition reaction. The catalyst atoms decrease the energy barrier to be overcome by H to break the bond, thus enhancing the kinetics of the chemical reactions and decreasing the temperature at which the dehydrogenation processes take place. The experimental data show that not all the hydrogen released by the formula units during the evolution of decomposition evolves out of the sample, but part of it remains in the lattice and migrates on a long-range scale within the sample. We identify, in this H mobilized population, the species which induces the fast tetragonal to monoclinic phase transformation accompanying decomposition. A partial spontaneous thermally activated regression of decomposition has also been observed by aging experiments. A model is proposed which accounts for the action of the Ti catalyst and for the atomistic mechanism of decomposition.

20.
Am J Clin Nutr ; 82(1): 125-32, 2005 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-16002810

RESUMEN

BACKGROUND: Normal brain and visual development is thought to require exogenous docosahexaenoic acid (DHA; 22:6n-3) intake, but the amount needed is debatable. Because the supplementation of breastfeeding mothers with DHA increases the DHA content of their infants' plasma lipids, we hypothesized that it might also improve brain or visual function in the infants. OBJECTIVE: The objective was to determine the effect of DHA supplementation of breastfeeding mothers on neurodevelopmental status and visual function in the recipient infant. DESIGN: Breastfeeding women received capsules containing either a high-DHA algal oil ( approximately 200 mg DHA/d) or a vegetable oil (no DHA) for 4 mo after delivery. Outcome variables included the fatty acid pattern of maternal plasma phospholipid and milk lipids 4 mo postpartum, the fatty acid pattern of plasma phospholipids and visual function in infants at 4 and 8 mo of age, and neurodevelopmental indexes of the infants at 12 and 30 mo of age. RESULTS: Milk lipid and infant plasma phospholipid DHA contents of the supplemented and control groups were approximately 75% and approximately 35% higher, respectively, at 4 mo postpartum. However, neither the neurodevelopmental indexes of the infants at 12 mo of age nor the visual function at 4 or 8 mo of age differed significantly between groups. In contrast, the Bayley Psychomotor Development Index, but not the Mental Development Index, of the supplemented group was higher (P < 0.01) at 30 mo of age. CONCLUSION: DHA supplementation of breastfeeding mothers results in higher infant plasma phospholipid DHA contents during supplementation and a higher Bayley Psychomotor Development Index at 30 mo of age but results in no other advantages either at or before this age.


Asunto(s)
Desarrollo Infantil/efectos de los fármacos , Ácidos Docosahexaenoicos/farmacología , Leche Humana/química , Agudeza Visual/efectos de los fármacos , Adulto , Lactancia Materna , Preescolar , Ácidos Docosahexaenoicos/metabolismo , Método Doble Ciego , Potenciales Evocados Visuales , Femenino , Humanos , Lactante , Masculino , Fosfolípidos/sangre , Desempeño Psicomotor/efectos de los fármacos
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