Enhancement of photocurrent in ferroelectric films via the incorporation of narrow bandgap nanoparticles.

A novel nanostructured ferroelectric photovoltaic material, consisting of the ferroelectric lead zirconate titanate (PZT) film and Ag(2) O semiconductor nanoparticles of comparatively narrow bandgap, has demonstrated a remarkable enhancement in the photovoltaic effects and the highest light-electricity conversion efficiency among those PZT-based photodiodes previously reported. This work sheds light on the design and enhanced performance of new optoelectronic and solar energy devices.

Structure, morphology and magnetic properties of Mg((x))Zn((1 - x))Fe2O4 ferrites prepared by polyol and aqueous co-precipitation methods: a low-toxicity alternative to Ni((x))Zn((1 - x))Fe2O4 ferrites.

The synthesis and properties of Mg((x))Zn((1 - x))Fe(2)O(4) spinel ferrites as a low-toxicity alternative to the technologically significant Ni((x))Zn((1 - x))Fe(2)O(4) ferrites are reported. Ferrite nanoparticles have been formed through both the polyol and aqueous co-precipitation methods that can be readily adapted to industrial scale synthesis to satisfy the demand of a variety of commercial applications. The structure, morphology and magnetic properties of Mg((x))Zn((1 - x))Fe(2)O(4) were studied as a function of composition and particle size. Scanning electron microscopy images show particles synthesised by the aqueous co-precipitation method possess a broad size distribution (i.e. ∼ 80-120 nm) with an average diameter of the order of 100 nm ± 20 nm and could be produced in high process yields of up to 25 g l(-1). In contrast, particles synthesised by the polyol-based co-precipitation method possess a narrower size distribution with an average diameter in the 30 nm ± 5 nm range but are limited to smaller yields of ∼ 6 g l(-1). Furthermore, the polyol synthesis method was shown to control average particle size by varying the length of the glycol surfactant chain. Particles prepared by both methods are compared with respect to their phase purity, crystal structure, morphology, magnetic properties and microwave properties.

Evidence for nanoscale two-dimensional Co clusters in CoPt3 films with perpendicular magnetic anisotropy.

The length scale of the local chemical anisotropy responsible for the growth-temperature-induced perpendicular magnetic anisotropy of face-centered cubic CoPt(3) alloy films was investigated using polarized extended x-ray absorption fine structure (EXAFS). These x-ray measurements were performed on a series of four (111) CoPt(3) films epitaxially grown on (0001) sapphire substrates. The EXAFS data show a preference for Co-Co pairs parallel to the film plane when the film exhibits magnetic anisotropy, and random chemical order otherwise. Furthermore, atomic pair correlation anisotropy was evidenced only in the EXAFS signal from the next neighbors to the absorbing Co atoms and from multiple scattering paths focused through the next neighbors. This suggests that the Co clusters are no more than a few atoms in extent in the plane and one monolayer in extent out of the plane. Our EXAFS results confirm the correlation between perpendicular magnetic anisotropy and two-dimensional Co segregation in CoPt(3) alloy films, and establish a length scale on the order of 10 Å for the Co clusters.

Topochemical growth of textured polycrystalline barium hexaferrite from oriented antiferromagnetic alpha-FeOOH nanorods.

Nanorods of goethite, i.e. alpha-FeOOH, were mixed with BaCO3, dispersed in a polymer solution, and oriented under a 90 kOe magnetic field during polymerization. The orientation arose principally from the interaction of the magnetic field with the anisotropic antiferromagnetism of the goethite particles. The oriented antiferromagnetic particles act as seeds for the topochemical growth of BaFe12O19 ferrite grains along the [0001] direction. The degree of grain orientation was determined using magnetic measurements and orientation distribution functions and pole figures determined by electron backscatter diffraction analysis.

Enhanced Néel temperature in Mn ferrite nanoparticles linked to growth-rate-induced cation inversion.

Mn ferrite (MnFe(2)O(4)) nanoparticles, having diameters from 4 to 50 nm, were synthesized using a modified co-precipitation technique in which mixed metal chloride solutions were added to different concentrations of boiling NaOH solutions to control particle growth rate. Thermomagnetization measurements indicated an increase in Néel temperature corresponding to increased particle growth rate and particle size. The Néel temperature is also found to increase inversely proportionally to the cation inversion parameter, delta, appearing in the formula (Mn(1-delta)Fe(delta))(tet)[Mn(delta)Fe(2-delta)](oct)O(4). These results contradict previously published reports of trends between Néel temperature and particle size, and demonstrate the dominance of cation inversion in determining the strength of superexchange interactions and subsequently Néel temperature in ferrite systems. The particle surface chemistry, structure, and magnetic spin configuration play secondary roles.

Growth induced magnetic and chemical anisotropy in CoPt3 alloy films.

We report the results of polarized Co EXAFS experiments on a series of CoPt3 films grown by molecular beam epitaxy on (100) MgO singe crystal substrates over a range of temperatures from 473 K to 1073 K. These samples exhibit substantial perpendicular magnetic anisotropy that is strongly dependent on the substrate growth temperature Tg. We measure a preference for in-plane Co-Co pairs that is correlated with the magnetic properties.

Selective-resputtering-induced perpendicular magnetic anisotropy in amorphous TbFe films.

Perpendicular magnetic anisotropy energy in rf magnetron sputtered amorphous TbFe films is measured to increase exponentially with pair-order anisotropy induced by the selective resputtering of surface adatoms during film growth.

Sample-angle feedback for diffraction anomalous fine-structure spectroscopy.

Diffraction anomalous fine-structure (DAFS) experiments measure Bragg peak intensities as continuous functions of photon energy near a core-level excitation. Measuring the integrated intensity at each energy makes the experiments prohibitively slow; however, in many cases DAFS can be collected quickly by measuring only the peak intensity at the center of the rocking curve. A piezoelectric-actuator-driven stage has been designed and tested as part of a sample-angle feedback circuit for locking onto the maximum of the rocking curve while the energy is scanned. Although software peak-tracking requires only a simple calculation of diffractometer angles, it is found that the additional hardware feedback dramatically improves the reproducibility of the data.

A study to evaluate Chlamydia screening in colposcopy clinics.

A preliminary study of 329 colposcopy patients was conducted to investigate the prevalence of endocervical chlamydial infection using the VIDAS Chlamydia Enzyme Immune Assay (EIA) and Chlamydia Immune Fluorescent Antigen (IFA) collection kits. The overall antigen positive rates of five of the 329 (1.5%) in the study group compared exactly with the four out of the 260 (1.5%) in the gynaecological outpatient controls. Women in the age group 16-20 years had the highest Chlamydia detection rates (7%) followed by those aged 21-30 years (2.3%). Four of the 119 (3.4%) single women in the study group were Chlamydia antigen positive compared with one of the 210 (0.5%) married women (P < 0.005). Among the controls, three of the 65 (4.6%) single and one of the 195 (0.5%) married women were positive. In both the study and control populations, Chlamydia antigen was more prevalent among younger women and non-contraceptive users. Routine screening in colposcopy patients may not be cost effective, but a policy of selective screening in young single women aged 20 years or less should be considered. Larger sample studies using the more specific and sensitive DNA amplification techniques would have probably yielded higher detection rates and are recommended.

Detection of abnormal cervical smears. A comparative study.

The inefficiency of the Ayres Spatula in detecting abnormality in cervical cytology has been demonstrated recently in a number of trials. In a randomized single-blind trial we have compared the Multispatula with the Ayres Spatula in a group of 158 women who previously had abnormal smears and had been referred to colposcopy clinics in the Lewisham and North Southwark Health Authority of London. The quality of the smears, as assessed by the presence or absence of endocervical cells, revealed that the Multispatula (87.3% pick-up) produced significantly better smears (p less than 0.005) compared with the Ayres Spatula (54.4% pick-up). In 149 smears collected with the Multispatula, atypia was confirmed. However, in only 129 smears taken with the Ayres Spatula were abnormal smears detected (p decreases less than 0.005). We concluded that the Multispatula produces a better quality smear which results in a decreased false negative rate in comparison with the Ayres Spatula.

The incidence of urological symptoms in normal pregnancy.

We questioned 181 healthy pregnant women about their urological symptoms during pregnancy; frequency and stress incontinence were commonest. The incidences of stress incontinence and urge incontinence were increased and that of hesitancy was decreased by pregnancy. Descent of the presenting part did not affect any of these symptoms.

Assessment of a pilot child playground injury prevention project in New York State.

Following a child playground equipment injury prevention project conducted in New York State in 1977, there was a 42 per cent reduction in playground equipment hazards, and a 22.4 per cent reduction in playground related injuries treated in the two largest hospitals of one of the program sites. Knowledge about unsafe playground practices and equipment hazards improved after the workshops for playground personnel. This approach to injury prevention deserves further study.

Changes in the oral glucose tolerance test during the puerperium.

Oral glucose tolerance tests were performed during late pregnancy, on the second and fifth days of the puerperium and finally six weeks after delivery in a group of 12 healthy women. The glucose response showed no significant change from the pregnancy values on the second and fifth days of the puerperium but each woman had returned to 'normal' by the sixth week post partum. In contrast, the insulin response had returned to the non-pregnant value by the second day of the puerperium.

Relation between placental site and length of gestation.

Two theories related to uterine action have been brought together to see whether the site of placental implantation influences the onset of labour: (1) that uterine contractions begin asymmetrically from a "pacemaker" in one uterine horn, and (2) that progesterone from the placenta blocks myometrial contractility primarily at the site of implantation. Case records were examined of 182 patients who had placental locations performed and who had a spontaneous onset of labour. Where the placenta was implanted in the right upper quadrant of the uterus labour occurred on average four days sooner than when it was implanted in the left upper quandrant: the difference was statistically significant.

Purine analogue sensitivity and lipase activity of leptospires.

The genus Leptospira can be divided into three groups based on purine analogue sensitivity and lipase (trioleinase) activity. Group 1 contains members of the "parasitic complex" of leptospires which initially cannot grow in media containing 10 mug of 2,6-diaminopurine (DAP) per ml or 200 mug of 8-azaguanine per ml. In addition, leptospires in this group possess lipase activity. Group 2 also contains members of the "parasitic complex" of leptospires. Although these leptospires are similarly sensitive to 8-azaguanine, they differ from group 1 leptospires in that they grow in media containing 10 mug of DAP per ml, and they do not possess detectable lipase activity. Group 3 consists of leptospires belonging to the "biflexa complex." These leptospires are resistant to both purine analogues and have lipase activity.

Differentiation of pathogenic and saprophytic letospires. I. Growth at low temperatures.

The minimal growth temperature of the pathogenic leptospires is between 13 and 15 C. The saprophytic leptospires have a minimal growth temperature between 5 and 10 C, or approximately 5 C below that of the pathogens. The capability of the saprophytic leptospires to grow at temperatures below those which allow the growth of the pathogenic leptospires provides a simple method of discrimination. With an inoculum yielding approximately 8 x 10(7) cells per ml in the test medium and an incubation temperature of 13 C, the saprophytic leptospires were easily differentiated from the pathogenic leptospires. All 13 saprophytic leptospires tested grew in the 10% rabbit serum medium at 13 C, whereas none of the 20 pathogens grew during the 30-day incubation period.

Antileptospiral activity of serum. II. Leptospiral virulence factor.

A definite relationship exists between the resistance of leptospires to the antibody-complement system and virulence. Leptospires capable of producing either lethal or renal infections in hamsters or guinea pigs were resistant to the leptospiricidal action of antibody and complement. Avirulent leptospires, in contrast to the virulent organisms, were rapidly immobilized and killed by these serum substances. The change of a virulent culture to the avirulent state as a result of growth in culture media was accompanied by the loss of resistance to antibody and complement. Virulent leptospires were phenotypically altered when grown in the presence of the purine analogue, 8-azaguanine. The cells became sensitive to antibody and complement without a corresponding decrease in virulence. The basis for a leptospiral virulence factor, the ability to multiply in vivo, appears to reside in their capacity to resist the leptospiricidal activity of the host antibody-complement system. The immune leptospiricidal assay provides a simple and rapid method of determining the virulence of a culture.