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1.
Gynecol Endocrinol ; 28(9): 674-7, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22313135

RESUMEN

Follicle development is controlled amongst other factors by pituitary gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) that act in synergy in completing follicle maturation. Exogenous gonadotropins, combined with gonadotropin-releasing hormone agonists, have been successfully used in patients with ovulatory disorders undergoing assisted reproduction. There is some evidence of a beneficial role of androgens or LH administration before FSH stimulation. This study was designed to verify whether the addition of LH in the early follicular phase, in downregulated patients undergoing follicular stimulation for assisted reproduction, would add benefits in terms of general outcomes and pregnancy rates. We compared two groups of patients one of which was treated with recombinant FSH (rFSH) alone and the other with rFSH plus recombinant LH (rLH), in the early follicular phase only. The number of eggs recovered was higher in the group treated with FSH only; however, the number of embryos available at transfer was similar in the two groups and, more importantly, the number of Grades I and II embryos was higher in the group pretreated with LH. Similarly, although biochemical pregnancy rate and clinical pregnancy rates were similar in both groups, a beneficial role of LH priming was demonstrated by the higher implantation rate achieved in these patients.


Asunto(s)
Fertilización In Vitro/métodos , Hormona Luteinizante/uso terapéutico , Folículo Ovárico/fisiología , Inducción de la Ovulación/métodos , Adulto , Femenino , Hormona Folículo Estimulante/uso terapéutico , Humanos , Embarazo , Índice de Embarazo , Proteínas Recombinantes/uso terapéutico , Resultado del Tratamiento
2.
Phys Chem Chem Phys ; 13(27): 12571-7, 2011 Jul 21.
Artículo en Inglés | MEDLINE | ID: mdl-21666930

RESUMEN

The study highlighted the main forces driving the formation of hydroxypropyl-cyclodextrins (HP-CDs) + poly(propylene) glycol 725 g mol(-1) inclusion complexes. The temperature parameter was chosen as the variable to modulate the hydrophobicity of the polymer, and consequently ITC experiments as functions of temperature as well as DSC measurements were done in a systematic way. The polymer is not included into HP-α-CD, it is strongly bound to HP-ß-CD and it is floating in HP-γ-CD. The stability of the inclusion complexes is entropy controlled. The gain of the entropy is a unique result compared to the opposite literature findings for inclusion complexes based on polymers and CDs. This peculiarity is ascribable to the removal of water molecules from cages during complexation and this effect compensates the entropy loss due to constraints caused by the CD threading. In spite the host-guest van der Waals contacts are optimized, the enthalpies for the inclusion complex formation are positive and reveal the large heat required for dehydrating the propylene oxide units. All the macrocycles enhanced the polymer solubility in water. Increasing the affinity of the macrocycle to the macromolecule makes more expanded the one-phase area of the binodal curve. A new thermodynamic approach was proposed to predict quantitatively the binodal curve as well as the dependence of the enthalpy of separation phase on the macrocycle composition. The agreement between the experimental data and the computed values was excellent.


Asunto(s)
Ciclodextrinas/química , Polímeros/química , Glicoles de Propileno/química , Calorimetría , Interacciones Hidrofóbicas e Hidrofílicas , Solubilidad , Temperatura , Termodinámica , Agua/química
3.
Eur Rev Med Pharmacol Sci ; 24(13): 7512-7515, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32706092

RESUMEN

OBJECTIVE: A novel type of Coronavirus was identified in China in December 2019. The first cases of a form of pneumonia of unknown etiology were detected at the beginning of that month in Wuhan. The virus is believed to have emerged at the Wuhan Huanan Seafood Market, where transmission of a zoonotic pathogen to humans occurred. PATIENTS AND METHODS: Some studies conducted in China during the epidemic report small numbers of pregnant women infected with SARS-CoV-2 and some pregnancy complications in patients with COVID-19. However, they fail to document the transplacental passage of the virus from mother to fetus. RESULTS: Following the COVID-19 outbreak, guidelines for couples who are undergoing treatments of assisted reproduction have been issued by the International Federation for Fertility Societies (IFFS), the American Society for Reproductive Medicine (ASRM), the European Society of Human Reproduction and Embryology (ESHRE) and the Latin American Network of Assisted Reproduction (REDLARA). They recommend couples to discuss assisted reproduction with their doctors while those at risk or with SARS-CoV-2 should consider freezing oocytes or embryos and retransferring them later. CONCLUSIONS: Other than the US, Italy is the country with the highest number of cases (197675 positives, 26644 deaths) (updated on April 26). The Italian National Transplant Centre and the Higher Institute of Health advised on March 17 to complete the cycles already started and not to start new cycles. Phase 2 will begin on 4 May with an increase in freedom of action and fertilization treatments will start again. The Society that brings together embryologists (SIERR) has issued the guidelines to be followed when this happens.


Asunto(s)
Betacoronavirus/aislamiento & purificación , Infecciones por Coronavirus/prevención & control , Pandemias/prevención & control , Neumonía Viral/prevención & control , Técnicas Reproductivas Asistidas , COVID-19 , China/epidemiología , Infecciones por Coronavirus/epidemiología , Infecciones por Coronavirus/virología , Brotes de Enfermedades/prevención & control , Femenino , Humanos , Italia/epidemiología , Neumonía Viral/epidemiología , Neumonía Viral/virología , Embarazo , SARS-CoV-2
4.
Sci Total Environ ; 407(12): 3712-20, 2009 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-19344932

RESUMEN

The impact of industrial and civil activities on an agricultural and residential area is presented in a detailed and global analysis. The examined area is the Pace river valley situated in the northern zone of Messina (Italy). The sources of pollution present in the area are: a Municipal Solid Waste Incinerator operating since 1979, a disused urban solid waste landfill which was used for 30 years, an urban solid waste treatment facility with heavy vehicles traffic, and two open pits for the production of bitumen. Large quantities of toxic, carcinogenic substances and criteria pollutants are released into the environment and represent potential hazards to human health. The analysis is performed using the EHHRA-GIS tool which employs an integrated, multimedia, multi-exposure pathways and multi-receptor risk assessment model that is able to manage all the steps which constitute the human health risk analysis in a georeferenced structure. The transport of pollutants in different environmental media is assessed applying models (AERMOD, GMS, CALINE) that take into account the particular three-dimensional morphology of the terrain. The results obtained, combined with a probabilistic risk assessment and a sensitivity analysis of calculation parameters, are a comprehensive assessment of the total human health risk in the area. Finally human health risks caused by toxic and carcinogenic substances are compared with acceptable legal limits in order to support environmental managers' decisions.


Asunto(s)
Contaminantes Ambientales/análisis , Residuos/análisis , Contaminantes Atmosféricos/análisis , Monitoreo del Ambiente , Contaminantes Ambientales/efectos adversos , Monitoreo Epidemiológico , Humanos , Italia , Neoplasias/epidemiología , Eliminación de Residuos , Medición de Riesgo , Contaminantes del Suelo/análisis , Salud Urbana , Residuos/efectos adversos , Contaminantes del Agua/análisis
5.
J Phys Chem B ; 112(31): 9328-36, 2008 Aug 07.
Artículo en Inglés | MEDLINE | ID: mdl-18620453

RESUMEN

The effect of polyethylene oxide (PEO) or polypropylene oxide (PPO) oligomers of various molecular weight (Mw) as well as of triblock copolymers, based on PEO and PPO blocks, on aqueous laponite RD suspensions was studied with small-angle neutron scattering (SANS). The radius of gyration (RG) increases for low M w whereas the opposite occurs for larger Mw. This behavior is explained on the basis that an effective R G is given by two contributions: (1) the size of the particles coated with the polymer and (2) the interactions between the laponite RD particles which are attractive for small and repulsive for large polymers. The SANS curves in the whole Q-range are well described by a model of noninteracting polydisperse core+shell disks, where the thickness of the polymer layer increases with the Mw. The adsorbed polymer is in a more compact conformation compared to a random coil distribution while the fraction of the polymer in the shell formed around the laponite RD particles is nearly independent of Mw. For increasing laponite RD amounts, at a given polymer composition, the thickness of the polymer slightly changes. In some cases, where also gelation is sped up, a structure factor with attractive interaction was employed which allowed to evaluate the attractive forces between the laponite RD particles. The gelation time was determined for mixtures at fixed copolymer and laponite RD concentrations. Surprisingly, it is observed that gels are formed despite the fact that the binding sites of the laponite RD particles are almost covered but the polymer size is too small to prevent aggregation. The gelation rate is correlated to structure and thermodynamics of these systems. Namely, when the balance between the steric forces and the depletion attractive forces undergoes an abrupt change the gelation time also undergoes a sharp variation. For lower and comparable Mw, PPO speeds up the gelation more efficiently than PEO while for higher Mw the gelation kinetics is slowed down again. Interestingly, copolymers of PEO and PPO blocks do not induce gelation in the time-window where the homopolymers do.

6.
Cell Death Discov ; 4: 34, 2018 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-29531831

RESUMEN

Granulocyte-macrophage colony-stimulation factor plays different crucial roles during embryo implantation and subsequent development. Here we aimed to evaluate the effects of embryo cell culture medium, with the inclusion of granulocyte-macrophage colony-stimulation factor (GM-CSF), on embryo development and pregnancy rate. To this end, we took advantage of our retrospective observational study to correlate the outcomes from two different culture media. We included in this study 25 unselected patient from our IVF Center that underwent heterologous IVF cycle with crypreserved oocytes. We analyze the fertilization rate, pregnancy rate, and embryo quality at different day of transfer obtained from two different media composition. Our results show that the rate of fertilization and the pregnancy rate were increased using medium added with this particular type of cytokines (GM-CSF).

7.
Bone Marrow Transplant ; 53(1): 39-43, 2018 01.
Artículo en Inglés | MEDLINE | ID: mdl-28991245

RESUMEN

Hematopoietic cell transplant (HCT) recipients have a substantial risk of developing secondary solid cancers (SSCs). The aim of this retrospective study was to compare the incidence of SSC in a monocentric cohort of thalassemia major (TM) patients (n=122) who received HCT versus an hematopoietic cell donor monocentric cohort (n=122) and versus a large multicenter cohort of age- and sex-matched TM patients (n=244) who received conventional therapy. With a median follow-up of 24 years, 8 transplanted patients were diagnosed with SSC at a median of 18 years after HCT and at a median age of 33 years. Three patients died of cancer progression and 5 are living after a follow-up ranging from 10 months to 16 years after SSC diagnosis. The 30-year cumulative incidence of developing SSC was 13.24%. The occurrence of solid cancers in the hematopoietic cell donor cohort was limited to only one case for a significantly lower cumulative incidence (3.23%, P=0.02) and to 3 cases in the cohort of nontransplant patients for a significantly lower cumulative incidence (1.32%, P=0.005). This study shows that the magnitude of increased risk of SST is fourfold to sixfold for patients treated with HCT as compared with hematopoietic cell donors and nontransplant patients.


Asunto(s)
Trasplante de Células Madre Hematopoyéticas/efectos adversos , Neoplasias Primarias Secundarias/etiología , Acondicionamiento Pretrasplante/efectos adversos , Talasemia beta/complicaciones , Femenino , Humanos , Masculino , Persona de Mediana Edad , Neoplasias Primarias Secundarias/patología
8.
J Phys Chem B ; 110(51): 25883-94, 2006 Dec 28.
Artículo en Inglés | MEDLINE | ID: mdl-17181236

RESUMEN

Within the topic of surfactant enhanced solubilization of additives sparingly soluble in water, volumetric, solubility, conductivity, and small-angle neutron scattering (SANS) experiments on mixtures composed of alpha,omega-dichloroalkane, surfactant, copolymer, and water were carried out at 298 K. The triblock copolymers (ethylene oxide)132(propylene oxide)50(ethylene oxide)132 (F108) and (ethylene oxide)76(propylene oxide)29(ethylene oxide)76 (F68) were chosen to investigate the role of the molecular weight keeping constant the hydrophilic/hydrophobic ratio. The selected surfactants are sodium decanoate (NaDec) and decyltrimethylammonium bromide (DeTAB) with comparable hydrophobicity and different charged heads. The alpha,omega-dichloroalkanes were chosen as contaminant prototypes. For the water + surfactant + copolymer mixtures, both the volume and the SANS results straightforwardly evidenced that (1) monomers of NaDec and copolymer unimers generate small mixed aggregates, (2) monomers of DeTAB combined with copolymer unimers do not form aggregates, and (3) unimeric copolymer is solubilized into NaDec and DeTAB micelles. The alpha,omeaga-dichloroalkanes presence induces the F108 aggregation even at very low copolymer composition. The addition of surfactant disintegrates the F108 aggregates and, consequently, the additive is expelled into the aqueous phase. Once F108 is in the unimeric state, it forms copolymer-micelle aggregates which incorporate the oil. In the case of F68 both the volumetric and the SANS data reveal that the additive does not alter the copolymer unimeric state. Moreover, they show that for the aqueous DeTAB-F68 system the additive trapping in both the copolymer-micelle aggregate and the pure micelles takes place being enhanced in the former aggregate in agreement with solubility experiments. For the NaDec-F68 mixtures, an additional solubilization process in the premicellar copolymer-surfactant microstructures occurs. SANS and conductivity data show that the additive incorporation into the mixed and the pure micelles does not essentially influence the structural properties of the aggregates.

9.
J Colloid Interface Sci ; 300(1): 368-74, 2006 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-16647711

RESUMEN

The thermodynamics of alpha,omega-dichloroalkanes in aqueous solutions of (ethylene oxide)(11)(propylene oxide)(16)(ethylene oxide)(11) (L35) and (propylene oxide)(8)(ethylene oxide)(23)(propylene oxide)(8) (10R5) was determined at 298 and 305 K. Modeling the experimental data allowed to calculate the standard free energy (DeltaG(D)(o)/w) and the volume (DeltaV(D)/w) for the additive-copolymer mixed aggregates formation per additive molecule. DeltaG(D)(o)/w for Cl(2)CH(2) and Cl(2)(CH(2))(2) evidenced that the process is controlled by the forces exercising between the chlorine atoms and the OH groups of the copolymer micelles protruded into the aqueous phase. Cl(2)(CH(2))(3) experiences both the hydrophilic and hydrophobic domains into the aggregates. The hydrophobic interactions are more significant in 10R5 whereas the hydrophilic ones are more significant in L35. Temperature increase does not influence DeltaG(D)(o)/w in 10R5, whereas, it does influence DeltaG(D)(o)/w in L35, enhancing the ability of the aggregate to extract the chlorinated compounds from the aqueous phase. The DeltaV(D)/w values are consistent with the free energy results. These insights agree with those predicted by the Flory liquid lattice theory. The calculations extended to several alpha,omega-dichloroalkanes showed that Cl(2)CH(2) and Cl(2)(CH(2))(2) prefer poly(ethylene oxide) (PEO), Cl(2)(CH(2))(3) exhibits the same affinity for both PEO and poly(propylene oxide) (PPO), whereas the more hydrophobic additives show a preference for PPO. The copolymer architecture plays a relevant role in the alpha,omega-dichloroalkane solubilization into the polymeric aggregates.

10.
Reprod Biomed Online ; 3(3): 190-194, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-12513853

RESUMEN

Twelve patients (17 cycles) who needed >3000 IU of recombinant FSH (rFSH) on previous follicular stimulation attempts for IVF using rFSH (group A) underwent further attempts (a total of 12 cycles) using rFSH supplemented with rLH from day 7 of stimulation (group B). There was no significant difference in the total quantitative administration of rFSH (mean: 4759 versus 4800 IU rFSH), days of stimulation (14.0 versus 12.6), number of M2 oocytes per patient (3.76 versus 4.17) or embryo morphology between group A and group B respectively. However, there was a significant increase in the incidence of fertilization (60.9 versus 86.0%; P = 0.006) and clinical (ongoing) pregnancies (1 versus 6; P = 0.022). The higher incidence of fertilization increased the mean number of embryos transferred per patient, although in this small group the data was not significant (1.75 versus 2.71). This preliminary clinical trial suggests that in poor responders superimposing rLH upon a down-regulated cycle stimulated with rFSH improves relevant outcome data; and this preliminary trial has encouraged the need for a larger and more detailed study.

11.
Anat Embryol (Berl) ; 202(2): 95-101, 2000 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-10985429

RESUMEN

During early cardiac development the atrial myocardium is continuous with the ventricular myocardium throughout the atrioventricular canal. The atrioventricular canal undergoes complex remodelling involving septation, formation of atrioventricular valves and insulation between atria and ventricles except at the level of the atrioventricular node. Understanding of these processes has been hampered by the lack of markers specific for this heart region. We have generated transgenic mice expressing beta-galactosidase under the control of the cardiac troponin I gene that show transgene expression mainly confined to the atrioventricular canal myocardium during early embryonic development. With further development beta-galactosidase positive cells are observed in the atrioventricular node and in the lower rim of both right and left atria, supporting the view that atrioventricular canal myocardium contributes to the atrioventricular node and is in part incorporated into the lower rim of the atria. These results identify the atrioventricular canal myocardium as a distinct transcriptional domain.


Asunto(s)
Nodo Atrioventricular/embriología , Corazón/embriología , Troponina I/genética , Animales , Nodo Atrioventricular/química , Expresión Génica , Atrios Cardíacos/embriología , Ventrículos Cardíacos/embriología , Ratones , Ratones Transgénicos , Miocardio/química , Cadenas Pesadas de Miosina/análisis , beta-Galactosidasa/análisis , beta-Galactosidasa/genética
12.
Reprod Fertil Dev ; 7(2): 169-74; discussion 174-5, 1995.
Artículo en Inglés | MEDLINE | ID: mdl-7480835

RESUMEN

The use of high insemination concentration (HIC) for in vitro fertilization (IVF) was compared with intracytoplasmic sperm injection (ICSI) in cases of male factor infertility. Sibling oocytes (n = 252) from 24 patients were used, 123 for HIC and 129 for ICSI. Although the incidence of fertilization was decreased with HIC (48% v. 61%), this treatment was nevertheless a viable option for many patients, especially when ICSI was not available. However, there was a higher incidence of cytoplasmic fragmentation of embryos after HIC compared with ICSI (36% v. 10%, P = 0.003) and the outcome was significantly affected by the severity of teratozoospermia. Using a cut-off of 5% normal forms, the incidence of fertilization with HIC for the group with < 5% normal forms was 37% compared with 72% for the group with > 5% normal forms; there was also a significant decrease in cleavage rate (P = 0.05) and the number of regular embryos (P = 0.005), and an increase in cytoplasmic fragmentation (P = 0.006) in patients with < 5% normal forms. No distinction was made between cases of teratozoospermia when ICSI was used. The present study confirms the value of HIC as a first line treatment for male infertility, as long as ICSI remains significantly more expensive and concerns on safety are mooted. However, the use of sibling oocytes for ICSI is recommended, especially in cases with < 5% normal sperm morphology.


Asunto(s)
Fertilización In Vitro/métodos , Infertilidad Masculina/terapia , Microinyecciones , Recuento de Espermatozoides , Adulto , Fase de Segmentación del Huevo , Citoplasma , Transferencia de Embrión , Femenino , Humanos , Masculino , Oocitos/ultraestructura , Espermatozoides/anomalías
13.
Waste Manag ; 24(8): 831-9, 2004.
Artículo en Inglés | MEDLINE | ID: mdl-15381235

RESUMEN

Markets for scrap tires have expanded since the early 1990s with the development of value-added applications such as tire-derived fuel and crumb-rubber-amended asphalt. Granulated tires have also displayed the ability to adsorb volatile organic compounds, indicating that the rubber material can be a useful filter media. Sand-based root zones, typically used for golf course putting green and athletic field construction, lack sufficient cation exchange capacity to restrict nitrogen and phosphorus migration through the root zone and into sub-surface drainage systems. Therefore, the adsorptive properties of tire rubber for retaining nitrogen and phosphorus were studied when applied as a distinct sub-surface drainage or intermediate layer in golf course putting greens. A statistically significant reduction in the concentration of nitrate in leachate was achieved by replacing traditional pea gravel with equally sized granulated tires for the drainage layer media, although the mechanism of nitrate mitigation remains unclear. The results indicate that using granulated tires as a drainage layer or fill material beneath sand-based root zones does not compromise the function of the profile or quality of the vegetation while creating an environmentally beneficial and value-added option for scrap tire reuse.


Asunto(s)
Conservación de los Recursos Naturales , Nitrógeno/aislamiento & purificación , Fósforo/aislamiento & purificación , Eliminación de Residuos , Goma , Biodegradación Ambiental , Filtración , Nitrógeno/análisis , Fósforo/análisis , Raíces de Plantas , Dióxido de Silicio , Contaminación del Agua/prevención & control
14.
J Genet Psychol ; 156(2): 231-40, 1995 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-7798081

RESUMEN

Seventy-five grade-school children were administered three tasks that measured their ability to represent the Euclidean horizontal coordinate: a traditional water-level test (WLT) that used a square-shaped vessel, a WLT that used a spherical vessel, and a task that used a crossbar apparatus. The latter two tasks differed from the traditional task in terms of the degree to which the apparatus presented a frame of reference that conflicted with environmental Euclidean coordinates. Performance was analyzed according to Piaget and Inhelder's (1956) stage-scoring system; that is, the testing procedures (a) allowed children to inspect the apparatus when it was rotated to discrete orientations; (b) corrected initial errors; and (c) included 0 degrees, 30 degrees, 60 degrees, and 90 degrees trials. Age-related stages were identified on each task. Levels of performance on one task were significantly correlated with levels on each of the other two tasks. Performance was less accurate on the traditional WLT than on either of the other two measures. These results provide evidence of the validity of the alternative tasks to measure children's horizontality representation. The findings suggest that horizontality assessment procedures should include orthogonal and oblique rotations and contain an inspection phase. Use of apparatuses with conflicting frames of reference renders tasks more difficult but is not necessary to observe age-related developmental progress during the grade-school years.


Asunto(s)
Aprendizaje , Instituciones Académicas , Percepción Espacial , Estudiantes , Factores de Edad , Niño , Desarrollo Infantil , Femenino , Humanos , Masculino , Análisis y Desempeño de Tareas
15.
J Genet Psychol ; 158(3): 333-45, 1997 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-9255960

RESUMEN

An experimental study of the effects of a didactic teaching approach and a constructivist teaching approach on 3rd- and 5th-grade boys' and girls' performance on arithmetic computation problems was conducted. Two groups of children, matched on the basis of initial computation performance as well as grade and gender, were taught how to solve arithmetic problems using one of these two instructional approaches. Analysis of subsequent computation test performance revealed that 5th graders scored higher than 3rd graders, and there was a significant interaction between gender and instruction group. After instruction, girls in the didactic group outperformed boys in both instruction groups and girls who had been taught using constructivist approaches. Gender differences in computation performance can appear relatively early, by 3rd grade, if didactic instruction strategies are used to teach computational rules. The pattern of gender differences suggests that didactic teaching does not handicap boys. Rather, it appears that didactic instruction enhances computational performance in girls.


Asunto(s)
Identidad de Género , Matemática , Solución de Problemas , Estudiantes/psicología , Enseñanza/métodos , Logro , Niño , Curriculum , Femenino , Humanos , Masculino , Aprendizaje Basado en Problemas
16.
Percept Mot Skills ; 82(2): 595-603, 1996 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-8724933

RESUMEN

90 undergraduates with low spatial perceptual ability were assigned to one of three groups of control, learner-guided instructions, and tutor-guided instructions. The groups differed in amount and type of spatial training administered in a laboratory setting. Participants completed horizontality and vertically spatial perceptual tasks immediately after pretesting and again one month later. Both groups given training showed more accurate performance at posttest than at pretest. In addition, the learner-guided instruction group outperformed the tutor-guided instruction group and control group at posttest and on novel but related tasks. Gender differences in posttest performance favoring males (n = 35) were obtained in the tutor-guided performance group and control group but not in the learner-guided instruction group. The number of hints the latter needed during training was predictive of posttest performance. Implications for assessment and remediation of undergraduates' spatial perceptual abilities are discussed.


Asunto(s)
Orientación , Desempeño Psicomotor , Educación Compensatoria , Percepción Espacial , Estudiantes/psicología , Adulto , Femenino , Identidad de Género , Humanos , Masculino
17.
Percept Mot Skills ; 68(3 Pt 1): 739-46, 1989 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-2748290

RESUMEN

Girls and boys from Grades 4 (ns = 15) and 9 (ns = 15 and 16) in Bombay, India were individually administered water-level and crossbar assessments of horizontality representation. Ninth graders were more successful than fourth graders, especially on trials in which the apparatus was obliquely rotated. Ninth graders, however, did not perform at ceiling levels, and a sex difference with a moderate effect size favoring male over female adolescents was obtained for the water-level task. These findings of both developmental and individual differences in horizontality performance replicate previous findings in Western cultures.


Asunto(s)
Desarrollo Infantil , Comparación Transcultural , Orientación , Desempeño Psicomotor , Percepción Espacial , Adolescente , Niño , Aprendizaje Discriminativo , Femenino , Humanos , India , Masculino
19.
Phys Chem Chem Phys ; 10(6): 794-9, 2008 Feb 14.
Artículo en Inglés | MEDLINE | ID: mdl-18231681

RESUMEN

Polystyrene nanoparticles were synthesized by emulsion polymerization of styrene. They were functionalized using the conventional surfactant N,N-dimethyloctylamine-N-oxide (ODAO), the tri-block copolymer (ethylene oxide)(13)(propylene oxide)(30)(ethylene oxide)(13) (L64) and their mixtures. To this purpose, dynamic light scattering and calorimetric experiments were carried out and provided information consistent to each other. The L64 adsorption is Langmuir-type in the copolymer dilute regime and generates complex structures at larger concentrations. In the region where ODAO is in the unimeric state, the adsorption process is cooperative leading to hemi-micelle formation at the polystyrene nanoparticle/water interface. In the concentrated region (above the critical micellar concentration), ODAO forms micelles which interact with the solid substrate most likely through ion-dipole forces. The ODAO addition to the dispersion containing polystyrene particles already wrapped by L64 creates an ODAO thickness around the dispersed particles the size of which is equal to that in the absence of the copolymer, but is built at much lower concentrations. A plausible interpretation of this behavior is that the adsorbed L64 confers to the nanoparticles surface novel properties which enhance the attractive forces with the ODAO molecules.


Asunto(s)
Óxido de Etileno/análogos & derivados , Luz , Nanopartículas/química , Octanos/química , Óxidos/química , Poliestirenos/química , Dispersión de Radiación , Adsorción , Calorimetría , Óxido de Etileno/química , Poliestirenos/síntesis química , Soluciones/química , Estireno/química , Propiedades de Superficie , Agua/química
20.
Langmuir ; 22(19): 8056-62, 2006 Sep 12.
Artículo en Inglés | MEDLINE | ID: mdl-16952241

RESUMEN

The affinity of functionalized Laponite clay toward an organic material in the aqueous phase was explored. Functionalization was performed by using triblock copolymers based on ethylene oxide (EO) and propylene oxide (PO) units that are EO(11)PO(16)EO(11) (L35) and PO(8)EO(23)PO(8) (10R5). Phenol (PhOH) was chosen as organic compound, which represents a contaminant prototype. To this purpose, densities and enthalpies of mixing as well as PhOH UV-absorption spectra were determined. The enthalpy and the spectrophotometry revealed PhOH-Laponite interactions whereas the volume did not. It emerged that the area occupied by PhOH on the Laponite surface is equal to that computed from the partial molar volume of PhOH in water, corroborating the insensitivity of the experimental volumes to the adsorption process. The situation where both PhOH and copolymer are simultaneously present in the aqueous Laponite suspension was also investigated. It turned out that the copolymer replaces PhOH from the water/Laponite clay interface, resulting in L35 being the more efficient. Moreover, the lateral copolymer-phenol interactions enhance the anchoring of PhOH to the solid surface. The reverse copolymer exercises the most important relevant effect. The UV-absorption spectra of PhOH in the water + copolymer + Laponite mixtures provided information that is consistent with those given by the calorimetric experiments. In conclusion, the aqueous copolymer-functionalized Laponite presents surface properties very different from the bare Laponite, favoring the removal of the organic compound from the solid surface.

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