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1.
S Afr Med J ; 110(3): 204-209, 2020 Feb 26.
Artículo en Inglés | MEDLINE | ID: mdl-32657697

RESUMEN

BACKGROUND: South Africa (SA) has very low and unchanging organ donation rates. A key point in the pathway of organ donation is obtaining informed consent from the family, which is necessary before organ donation can proceed. There is no published SA research on the consent rate and factors that influence this. OBJECTIVES: To describe the number of requests for consent and factors influencing this process in the SA context. METHODS: A prospective descriptive study was performed of all requests to families for organ donation in Western Cape Province, SA, by Groote Schuur Hospital (state sector), Red Cross War Memorial Children's Hospital (state sector) and Netcare (private sector) transplant co-ordinators from 1 May 2017 to 1 May 2018 to describe factors influencing consent rates. RESULTS: The 6 co-ordinators (3 state sector and 3 private sector) recorded data of 83 consecutive families approached in 16 hospitals over the 1-year period. Consent to organ donation was granted for 23 family requests (n=18 (state sector); n=5 (private sector)). The number of families approached was greater in the state sector (n=74) than in the private sector (n=9). The overall consent rate was 27.7% (24.3% (state sector); 55.5% (private sector)). The majority of referrals came from trauma and emergency units (n=55; 66.3%) and very few from intensive care units (n=25; 30.1%). Immediate fluid resuscitation was required in 56 (67.5%) potential donors. The majority of families (n=74; 89.2%) were receptive to the organ donation request, independent of their ultimate decision regarding donation. The main reason given for refusing to consent was that it was against their religion (n=21) or culture (n=18). CONCLUSIONS: This study showed that the number of families approached for consent to organ donation were low in the Western Cape (lower in the private sector), with a low consent rate (lower in the state sector). Donor management by clinical teams needs to be ongoing and active during the consent process. Consent discussions (and public awareness initiatives) need to be sensitive to and deal with religious and cultural reservations about organ donation.


Asunto(s)
Obtención de Tejidos y Órganos/estadística & datos numéricos , Cultura , Familia , Humanos , Consentimiento Informado , Estudios Prospectivos , Religión , Sudáfrica
2.
Nat Commun ; 11(1): 1097, 2020 02 27.
Artículo en Inglés | MEDLINE | ID: mdl-32107369

RESUMEN

Manipulating the surface energy, and thereby the wetting properties of solids, has promise for various physical, chemical, biological and industrial processes. Typically, this is achieved by either chemical modification or by controlling the hierarchical structures of surfaces. Here we report a phenomenon whereby the wetting properties of vermiculite laminates are controlled by the hydrated cations on the surface and in the interlamellar space. We find that vermiculite laminates can be tuned from superhydrophilic to hydrophobic simply by exchanging the cations; hydrophilicity decreases with increasing cation hydration free energy, except for lithium. The lithium-exchanged vermiculite laminate is found to provide a superhydrophilic surface due to its anomalous hydrated structure at the vermiculite surface. Building on these findings, we demonstrate the potential application of superhydrophilic lithium exchanged vermiculite as a thin coating layer on microfiltration membranes to resist fouling, and thus, we address a major challenge for oil-water separation technology.

3.
J Strength Cond Res ; 32(2): 356-363, 2018 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-29369953

RESUMEN

Marcos, MA, Koulla, PM, and Anthos, ZI. Preseason maximal aerobic power in professional soccer players among different divisions. J Strength Cond Res 32(2): 356-363, 2018-The purpose of this study was to examine and compare the anthropometric, maximal oxygen uptake (V[Combining Dot Above]O2max), and positional differences of first division (D1) professional football players from players of second (D2) and third (D3) divisions in Cyprus football leagues. Four hundred twenty-one professional male football players participated in this study. All subjects underwent anthropometric and body composition evaluation. In addition, they performed an incremental cardiopulmonary exercise testing (CPET) on a treadmill for V[Combining Dot Above]O2max evaluation. The results were analyzed using 1-way analysis of variance, between subjects design revealing significant effects among the divisions. Tukey's honest significant difference (HSD) tests demonstrated that players from D1 scored significantly higher on V[Combining Dot Above]O2max and lasted significantly longer on the treadmill than participants of D2 and D3 (p ≤ 0.05). Similar findings were demonstrated when D2 was contrasted against D3 players. Goalkeepers, defenders, and forwards demonstrated significantly higher anthropometric measurements, whereas wingers and midfielders demonstrated significantly higher V[Combining Dot Above]O2max (p ≤ 0.05) than goalkeepers and defenders. The findings of this study clearly demonstrated that cardiovascular fitness, as determined by CPET, is an important fitness parameter that differentiates professional football players who play at a more advanced level. This could be attributed to the different seasonal schedules that allow for longer transition time for lower division players and thus favoring greater detraining effects. Emphasis should be given by fitness professionals on transition period training to minimize the detraining effects especially in lower divisions.


Asunto(s)
Consumo de Oxígeno/fisiología , Fútbol/fisiología , Ejercicio de Calentamiento/fisiología , Adulto , Antropometría , Composición Corporal , Prueba de Esfuerzo , Frecuencia Cardíaca/fisiología , Humanos , Masculino , Reproducibilidad de los Resultados , Adulto Joven
4.
J Hum Hypertens ; 31(12): 795-800, 2017 12.
Artículo en Inglés | MEDLINE | ID: mdl-28972573

RESUMEN

This pilot study evaluated the efficacy of a Hypertension Prevention Program (HPP) administered through a mobile application platform with human coaching (app) on reduction in blood pressure and weight in 50 adults with prehypertension or hypertension. Participants were recruited into a 24-week mobile application intervention to administer the HPP between January 2016 and July 2016. Dietary elements of the programme were based on the Dietary Approaches to Stop Hypertension. The programme included in-app human coaching with bi-weekly phone calls, meal logging, blood pressure tracking and educational material. Main outcome variables included change in systolic and diastolic blood pressure, hypertension category, and weight loss. Data were analysed between October 2016 and December 2016. The HPP yielded overall improvements in weight (-3.04±4.04 kg, P=<0.001), diastolic blood pressure (-5.06±11.89 mm Hg, P=0.004), and hypertension category (-0.48±0.74 mm Hg, P=<0.001). Sustained engagement of 80% resulted in significant reductions in systolic blood pressure (-7.75±12.56, P=<0.001) and weight (-3.73±4.01 kg, P<0.001) for programme completers, contributing to hypertension category change (-0.58±0.64 mm Hg, P<0.001). Mobile delivery of a lifestyle intervention for hypertension prevention showed short-term potential to reduce risk of hypertension, supporting the need for longer studies to investigate the use of mHealth lifestyle modification to reduce the risk of hypertension, a public health priority.


Asunto(s)
Hipertensión/prevención & control , Aplicaciones Móviles/estadística & datos numéricos , Adulto , Presión Sanguínea , Femenino , Humanos , Masculino , Persona de Mediana Edad , Proyectos Piloto , Pérdida de Peso
5.
Nat Mater ; 16(4): 461-466, 2017 04.
Artículo en Inglés | MEDLINE | ID: mdl-27842073

RESUMEN

The interaction of water with TiO2 is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO2(110) interface with water. This has provided an atomic-level understanding of the water-TiO2 interaction. However, nearly all of the previous studies of water/TiO2 interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO2(110) surface pre-characterized at the atomic level. Scanning tunnelling microscopy and surface X-ray diffraction are used to determine the structure, which is comprised of an ordered array of hydroxyl molecules with molecular water in the second layer. Static and dynamic density functional theory calculations suggest that a possible mechanism for formation of the hydroxyl overlayer involves the mixed adsorption of O2 and H2O on a partially defected surface. The quantitative structural properties derived here provide a basis with which to explore the atomistic properties and hence mechanisms involved in TiO2 photocatalysis.

6.
J Chem Phys ; 140(4): 041103, 2014 Jan 28.
Artículo en Inglés | MEDLINE | ID: mdl-25669494

RESUMEN

Ab initio simulations that account for nuclear quantum effects have been used to examine the order-disorder transition in squaric acid, a prototypical H-bonded antiferroelectric crystal. Our simulations reproduce the >100 K difference in transition temperature observed upon deuteration as well as the strong geometrical isotope effect observed on intermolecular separations within the crystal. We find that collective transfer of protons along the H-bonding chains - facilitated by quantum mechanical tunneling - is critical to the order-disorder transition and the geometrical isotope effect. This sheds light on the origin of isotope effects and the importance of tunneling in squaric acid which likely extends to other H-bonded ferroelectrics.

7.
J Hum Hypertens ; 26(7): 443-51, 2012 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-21633378

RESUMEN

The aim of this study was to determine cardiovascular (CV) risk factors (RFs) and target organ damage clustering in 21280 Greek hypertensives stratified by gender and age. Glycemic and lipid profile were determined, left ventricular mass index, estimated gromerular filtration rate (eGFR), 10-years CV risk according to Framingham risk score (FRS) and HeartScore (HS) were calculated. Only 10.2% of patients had no concomitant RFs, 53.1% had one (48.8% dyslipidemia, 3.4% smoking, 0.9% diabetes), 32.9% had two (26% dyslipidemia and smoking, 6.6% dyslipidemia and diabetes, 0.3% smoking and diabetes) and 3.7% had all four traditional RFs. Obesity was present in 30%, metabolic syndrome in 38%, low eGFR in 24% and left ventricular hypertrophy in 49%. Mean FRS risk was 35% for males, 24.1% for females whereas in high risk (>20%) were 68.7 and 50.7%, respectively (P<0.0001). Mean HS risk was 8.4% for males, 6.2% for females whereas in high risk (>5%) were 48.6 and 36.2%, respectively (P<0.0001). Age was correlated to pulse pressure, eGFR, left ventricular mass index and CV risk (P<0.0001). Ageing increased the risk difference between genders for total (P=0.001) but not for fatal events (P=nonsignificant). In conclusion, as RFs cluster in hypertensives, CV risk calculation should guide treatment decisions.


Asunto(s)
Enfermedades Cardiovasculares/etiología , Adulto , Factores de Edad , Anciano , Anciano de 80 o más Años , Femenino , Tasa de Filtración Glomerular , Grecia , Humanos , Masculino , Persona de Mediana Edad , Prevalencia , Estudios Retrospectivos , Factores de Riesgo , Factores Sexuales , Fumar/efectos adversos
8.
Phys Chem Chem Phys ; 13(44): 19988-96, 2011 Nov 28.
Artículo en Inglés | MEDLINE | ID: mdl-22008902

RESUMEN

Using a combination of X-ray photoemission and near-edge X-ray absorption spectroscopy (NEXAFS) as well as density-functional theory (DFT), we have investigated the adsorption of acetone on ice in the temperature range from 218 to 245 K. The adsorption enthalpy determined from experiment (45 kJ mol(-1)) agrees well with the adsorption energy predicted by theory (41 to 44 kJ mol(-1)). Oxygen K-edge NEXAFS spectra indicate that the presence of acetone at the ice surface does not induce the formation of a pre-melted layer at temperatures up to 243 K. DFT calculations show that the energetically most favored adsorption geometry for acetone on ice is with the molecular plane almost parallel to the surface.

9.
Nat Mater ; 10(10): 794-8, 2011 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-21892176

RESUMEN

Resolving the atomic structure of the surface of ice particles within clouds, over the temperature range encountered in the atmosphere and relevant to understanding heterogeneous catalysis on ice, remains an experimental challenge. By using first-principles calculations, we show that the surface of crystalline ice exhibits a remarkable variance in vacancy formation energies, akin to an amorphous material. We find vacancy formation energies as low as ~0.1-0.2 eV, which leads to a higher than expected vacancy concentration. Because a vacancy's reactivity correlates with its formation energy, ice particles may be more reactive than previously thought. We also show that vacancies significantly reduce the formation energy of neighbouring vacancies, thus facilitating pitting and contributing to pre-melting and quasi-liquid layer formation. These surface properties arise from proton disorder and the relaxation of geometric constraints, which suggests that other frustrated materials may possess unusual surface characteristics.

10.
Heart ; 97(10): 832-7, 2011 May.
Artículo en Inglés | MEDLINE | ID: mdl-21357374

RESUMEN

BACKGROUND: Exercise improves the clinical outcome of patients with coronary artery disease (CAD); however, the ideal exercise duration for each patient remains unclear. OBJECTIVE: To investigate the effects of exercise duration on arterial elastic properties and antioxidant/pro-oxidant mechanisms in patients with CAD. DESIGN, SETTING, PATIENTS, INTERVENTIONS: Sixty male patients with CAD were randomised into two groups, and underwent exercise for 30 min or 60 min in a crossover design with 2 weeks' wash-out period. In all participants aortic and radial blood pressures (BP) and arterial elastic properties (augmentation index (AIx)/pulse wave velocity (PWV)) were determined at baseline and 24 h after exercise. Plasma malonyldialdehyde (MDA) and superoxide dismutase (SOD)1 and SOD2 levels were also measured. RESULTS: Exercise had no effect on aortic and radial BP (p=NS for all). Walking for 30 min improved AIx (from 33.79 ± 0.91% to 31.73 ± 0.86%, p<0.001) and PWV (from 9.26 ± 0.95 m/s to 9.06 ± 0.21 m/s, p<0.001), while exercise for 60 min had adverse effects on vascular stiffness (for AIx: from 33.37 ± 0.93% to 33.73 ± 1.05%, p=NS and for PWV: from 9.25 ± 0.19 m/s to 9.37 ± 0.21 m/s, p < 0.05 mainly in older patients). Exercise for 60 min was associated with a significant 20% increase in MDA levels (p<0.05). Exercise had no effects on SOD1 levels, however it significantly increased SOD2 levels after 30 min (from 2.26 ± 0.22 ng/mL to 2.36 ± 0.18 ng/mL, p < 0.05) but not after 60 min (p=NS). Conclusion Shorter exercise duration was associated with favourable antioxidant and vascular effects, while longer exercise blunted these beneficial effects and was accompanied by adverse effects on vascular function, mainly in older coronary patients. Further studies are required to explore the hypothesis that a more individualised approach to the selection of the appropriate exercise programme should be considered for patients with CAD.


Asunto(s)
Antioxidantes/metabolismo , Enfermedad de la Arteria Coronaria/fisiopatología , Ejercicio Físico/fisiología , Anciano , Velocidad del Flujo Sanguíneo/fisiología , Enfermedad de la Arteria Coronaria/terapia , Estudios Cruzados , Elasticidad/fisiología , Terapia por Ejercicio/métodos , Humanos , Masculino , Malondialdehído/metabolismo , Persona de Mediana Edad , Superóxido Dismutasa/metabolismo , Superóxido Dismutasa-1 , Resistencia Vascular/fisiología , Caminata/fisiología
11.
Faraday Discuss ; 141: 277-92; discussion 309-46, 2009.
Artículo en Inglés | MEDLINE | ID: mdl-19227362

RESUMEN

The effect of temperature on the structure of the ice Ih (0001) surface is considered through a series of molecular dynamics simulations on an ice slab. At relatively low temperatures (200 K) a small fraction of surface self-interstitials (i.e. admolecules) appear that are formed exclusively from molecules leaving the outermost bilayer. At higher temperatures (ca. 250 K), vacancies start to appear in the inner part of the outermost bilayer exposing the underlying bilayer and providing sites with a high concentration of dangling hydrogen bonds. Around 250-260 K aggregates of molecules formed on top of the outermost bilayer from self-interstitials become more mobile and have diffusivities approaching that of liquid water. At approximately 270-280 K the inner bilayer of one surface noticeably destructures and it appears that at above 285 K both surfaces are melting. The observed disparity in the onset of melting between the two sides of the slab is rationalised by considering the relationship between surface energy and the spatial distribution of protons at the surface; thermodynamic stability is conferred on the surface by maximising separations between dangling protons at the crystal exterior. Local hotspots associated with a high dangling proton density are suggested to be susceptible to pre-melting and may be more efficient at trapping species at the external surface than regions with low concentrations of protons thus potentially helping ice particles to catalyse reactions. A preliminary conclusion of this work is that only about 10-20 K below the melting temperature of the particular water potential employed is major disruption of the crystalline lattice noted which could be interpreted as being "liquid", the thickness of this film being about a nanometre.

13.
Phys Rev Lett ; 96(14): 146101, 2006 Apr 14.
Artículo en Inglés | MEDLINE | ID: mdl-16712097

RESUMEN

Scanning tunneling microscopy (STM) and density-functional theory are used to reexamine the structure of the renowned p(4 x 4)-O/Ag(111) surface oxide. The accepted structural model [C. I. Carlisle, Phys. Rev. Lett. 84, 3899 (2000)10.1103/PhysRevLett.84.3899] is incompatible with the enhanced resolution of the current STM measurements. An "Ag6 model" is proposed that is more stable than its predecessor and accounts for the coexistence of the p(4 x 4) and a novel c(3 x 5log3)rect phase. This coexistence is an indication of the dynamic complexity of the system that until now has not been appreciated.

14.
Phys Rev Lett ; 93(11): 116101, 2004 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-15447355

RESUMEN

Scanning tunneling microscopy (STM) images of water submonolayers on Pd(111) reveal quasiperiodic and isolated adclusters with internal structure that would ordinarily be ascribed to icelike puckered hexagonal units. However, density functional theory and STM simulations contradict this conventional picture, showing instead that the water adlayers are composed mainly of flat-lying molecules arranged in planar water hexagons. A new rule for two dimensional (2D) water growth is offered that generates the structures observed experimentally from planar hexamer units.

15.
Phys Rev Lett ; 92(13): 136104, 2004 Apr 02.
Artículo en Inglés | MEDLINE | ID: mdl-15089633

RESUMEN

Based on the results of density functional theory calculations, a novel mechanism for the diffusion of water dimers on metal surfaces is proposed, which relies on the ability of H bonds to rearrange through quantum tunneling. The mechanism involves quasifree rotation of the dimer and exchange of H-bond donor and acceptor molecules. At appropriate temperatures, water dimers diffuse more rapidly than water monomers, thus providing a physical explanation for the experimentally measured high diffusivity of water dimers on Pd[111] [Science 297, 1850 (2002)]].

16.
Bone Marrow Transplant ; 32(8): 795-800, 2003 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-14520424

RESUMEN

Cytomegalovirus viral load measurement is a powerful new tool for monitoring of CMV disease; however, the optimal strategy for use is unknown. Weekly plasma CMV viral loads and CMV-related outcomes were monitored in 46 consecutive allogeneic bone marrow transplantation (BMT) recipients receiving standardised antiviral prophylaxis. A total of 412 CMV viral loads were quantitated in the first 100 days post transplantation with 77 positive samples (19%) in 20 patients (43%). No patient with all negative CMV viral load results developed CMV disease. Two of three patients with highly positive CMV viral loads (first positive < or =30 days post transplant, maximum viral load > or =5000 copies/ml, and > or =50% of samples positive) developed CMV disease. A total of 17 patients with positive CMV viral loads, who did not meet the criteria for highly positive, did not develop CMV disease. CMV viral load detection was higher in recipients who were CMV sero-positive. In conclusion, CMV disease did not occur in the setting of a persistently negative CMV viral load. A positive CMV viral load result occurred commonly after allogeneic BMT, even in patients receiving antiviral prophylaxis.


Asunto(s)
Antivirales/administración & dosificación , Trasplante de Médula Ósea/efectos adversos , Infecciones por Citomegalovirus/diagnóstico , Infecciones por Citomegalovirus/prevención & control , Ganciclovir/administración & dosificación , Carga Viral , Enfermedad Aguda , Adolescente , Adulto , Enfermedad Crónica , Infecciones por Citomegalovirus/tratamiento farmacológico , Femenino , Estudios de Seguimiento , Enfermedad Injerto contra Huésped/diagnóstico , Enfermedad Injerto contra Huésped/mortalidad , Humanos , Masculino , Persona de Mediana Edad , Estudios Prospectivos
17.
Phys Rev Lett ; 90(24): 246103, 2003 Jun 20.
Artículo en Inglés | MEDLINE | ID: mdl-12857205

RESUMEN

For many decades it has been assumed that an adsorbate centered above a metal surface and with a net negative charge should increase the work function of the surface. However, despite their electronegativity, N adatoms on W[100] cause a significant work function decrease. Here we present a resolution of this anomaly. Using density functional theory, we demonstrate that while the N atom carries a negative charge, of overriding importance is a reduction in the surface overspill electron density into the vacuum, when that charge is engaged in bonding to the adatom. This novel interpretation is fundamentally important in the general understanding of work function changes induced by atomic adsorbates.

18.
Phys Rev Lett ; 90(21): 216102, 2003 May 30.
Artículo en Inglés | MEDLINE | ID: mdl-12786566

RESUMEN

Ab initio density functional theory has been used to investigate the adsorption of H2O on several close-packed transition and noble metal surfaces. A remarkably common binding mechanism has been identified. On every surface H2O binds preferentially at an atop adsorption site with the molecular dipole plane nearly parallel to the surface. This binding mode favors interaction of the H2O 1b(1) delocalized molecular orbital with surface wave functions.

19.
J Am Chem Soc ; 125(9): 2746-55, 2003 Mar 05.
Artículo en Inglés | MEDLINE | ID: mdl-12603164

RESUMEN

Density functional theory has been used to perform a comparative theoretical study of the adsorption and dissociation of H(2)O monomers and icelike bilayers on Ru[0001]. H(2)O monomers bind preferentially at atop sites with an adsorption energy of approximately 0.4 eV/H(2)O. The main bonding interaction is through the H(2)O 1b(1) molecular orbital which mixes with Ru d(z)2 states. The lower-lying set of H(2)O molecules in an intact H(2)O bilayer bond in a similar fashion; the high-lying H(2)O molecules, however, do not bond directly with the surface, rather they are held in place through H bonding. The H(2)O adsorption energy in intact bilayers is approximately 0.6 eV/H(2)O and we estimate that H bonding accounts for approximately 70% of this. In agreement with Feibelman (Science 2002, 295, 99) we find that a partially dissociated OH + H(2)O overlayer is energetically favored over pure intact H(2)O bilayers on the surface. The barrier for the dissociation of a chemisorbed H(2)O monomer is 0.8 eV, whereas the barrier to dissociate a H(2)O incorporated in a bilayer is just 0.5 eV.

20.
Eur Radiol ; 11(8): 1502-5, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-11519565

RESUMEN

The aim of this study was to examine the effectiveness of helical CT in the assessment of intraocular foreign bodies, evaluating two protocols with different collimation. We performed helical-CT studies in 30 patients. Fifteen patients were examined with 1.5-mm collimation and the other 15 patients with 3.0-mm collimation. All other imaging parameters were identical in both protocols. Multiplanar images were reconstructed. The examinations were reviewed for presence, localization and size of intraocular foreign bodies. We compare our results with the surgical data. We estimate the required examination time. In the first group (collimation 1.5 mm) an intraorbital foreign body was detected in 8 of 15 patients. In 3 of 8 patients an intraocular foreign body (all were metallic) was detected. In the second group (collimation 3.0 mm) an intraorbital foreign body was detected in 9 of 15 patients. In 8 of 9 patients an intraocular foreign body (all were metallic) was detected. Our results were confirmed by surgery in all cases. Examination time was 36 s in the first group and 18 s in the second group. Computed tomography should be considered the imaging modality of choice in the assessment of metallic intraocular foreign bodies and 3.0-mm collimation is optional, because of reduced examination time and radiation exposure.


Asunto(s)
Cuerpos Extraños en el Ojo/diagnóstico por imagen , Procesamiento de Imagen Asistido por Computador , Tomografía Computarizada por Rayos X , Adulto , Femenino , Cuerpos Extraños/diagnóstico por imagen , Humanos , Masculino , Metales , Persona de Mediana Edad , Órbita/diagnóstico por imagen , Estudios Prospectivos , Tomografía Computarizada por Rayos X/métodos
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