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  • 1
    Electronic Resource
    Electronic Resource
    A study of placental bed spiral arteries and trophoblast invasion in normal and severe pre-eclamptic pregnancies (1994)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 101 (1994), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective To investigate trophoblast invasion and vascular changes in placental bed spiral arteries in normal and severe pre-eclamptic pregnancies.Design A histological and immunohistochemical study of placental bed biopsies containing spiral arteries.Setting The University Hospital, Leuven, Belgium.Subjects Twenty-one placental bed biopsies from 21 normal pregnancies and 24 placental bed biopsies from 24 severe pre-eclamptic pregnancies, taken at caesarean section.Observations Histological and immunohistochemical appearance of spiral arteries (stained with haematoxylin and eosin), periodic acid schiff, and a monoclonal antibody to low molecular weight cytokeratin.Results One hundred and twenty-seven spiral arteries were studied. In the 21 biopsies from clinically normal pregnancies at term, 100% of the decidual spiral arteries and 76% of the myometrial arteries showed trophoblast invasion. In the 24 biopsies from women with severe pre-eclampsia, trophoblast invasion was seen in 44 % and 18 % of the decidual and myometrial segments, respectively. Endovascular trophoblast invasion was complete, partial or isolated. A variety of morphological features was present not only in different spiral arteries from the same biopsy but also in different segments of the same artery. The vascular change most commonly associated with normal pregnancies was physiological change and subintimal thickening of both segments of the spiral arteries. In pre-eclampsia medial disorganisation and hyperplasia in the myometrial arteries and acute atherosis in decidual arteries were common.Conclusion Endovascular trophoblast did not show an all or none invasive phenomenon in normal and pre-eclamptic pregnancies. More decidual than myometrial arteries were invaded in both groups of patients, and there was a gradient in the percentage of decidual and myometrial arteries invaded from normal pregnancy to pre-eclampsia. Morphological features in one spiral artery may not necessarily be representative of all of those in a placental bed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1994.tb13182.x
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  • 2
    Electronic Resource
    Electronic Resource
    Micromagnetics of Co-based media: Experiment and model (invited) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5540-5543 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The micromagnetics of Co86Cr14 thin-film longitudinal recording media has been investigated using Lorentz transmission electron microscopy, in the Fresnel and differential phase contrast (DPC) modes. The media studied were 350-A(ring)-thick Co86Cr14 on a 200-A(ring) Cr layer, both of which were rf sputtered onto Si3N4 membranes for ease of observation in the TEM. Different magnetization states were investigated by imaging the sample at various points in the remanent hysteresis loop. This allowed direct comparison between experimental conditions and a micromagnetic computer model which assumes the media to be an array of single-domain particles, interacting via magnetostatics and moderate integranular exchange [J.-G. Zhu and H. N. Bertram, J. Appl. Phys. 63, 3248 (1988)]. The DPC imaging technique allows vector maps and two-dimensional histograms of the integrated in-plane magnetic induction to be obtained at each magnetization state for comparison with the computer model. The scale and displacement of magnetization vortices and ripple between different states was also investigated. Both experiment and model show increasing dispersion with increasing reversal field and motion of magnetization vortices. Comparison, using the model, of individual magnetization states in an applied field and at remanence indicate a strong influence of stray fields from the media on the DPC image contrast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345880
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic force microscopy with batch-fabricated force sensors : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5883-5885 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper the properties of force sensors suitable for magnetic force microscopy (MFM) made by coating silicon microcantilevers with various thin magnetic films are analyzed. These MFM force sensors are batch fabricated and their magnetic properties controlled by choosing appropriate coatings. Theoretical calculations show that thin-film MFM tips have a significantly reduced stray field, a good signal-to-noise ratio, and yield improved resolution when compared to etched wire tips. The sample perturbation due to the tip stray field is small, allowing the imaging of low-coercivity samples such as Permalloy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347856
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  • 4
    Electronic Resource
    Electronic Resource
    Microscopic studies of the magnetization-reversal process in Co-alloy thin films (abstract) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4713-4713 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quantitative study of the microscopic magnetization-reversal process in 250-A(ring) thick Co, Co90Pt10, and Co88Cr12 films deposited on top of a 250-A(ring)-thick Cr layer has been carried out. The entire structure was on a SiN membrane to allow ease of observation in the transmission electron microscope (TEM). The magnetization-reversal process was studied by using an electromagnet to saturate the film in one direction; the applied field was then reversed until the sample reached a magnetization state between +Mr and −Mr; the field was then reduced to zero and the sample taken to the TEM for observation of the resulting magnetic structure using Fresnel and DPC Lorentz microscopy.1 This process was repeated for a number of reversal fields ranging from zero to the loop closure field. This study shows that as the reversal field was increased from zero towards the coercivity, the magnetization dispersion, i.e., the range of angles between the local magnetization and the original saturation direction, increased. The local magnetization direction varied markedly from one region of the film to the next, indicating that it is strongly tied to the local anisotropy of the film. Once the steep part of the B-H loop is reached, small reversed regions are nucleated. These reversed regions consume the entire film by continued growth and nucleation as the reverse field is increased. The nucleation occurs at the same site when the magnetization is cycled around the B-H loop. This indicates that the local anisotropy determines the sites in which critical nuclei are formed in a given applied field. The boundary between the switched and unswitched regions consists of a complex magnetization vortex structure. Once the entire film has been switched, the local magnetization dispersion decreases as the reverse field is increased. Comparison of the results among the Co-alloy films will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344809
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  • 5
    Electronic Resource
    Electronic Resource
    Implementation of differential phase contrast Lorentz microscopy on a conventional transmission electron microscope (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6011-6013 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Differential phase contrast (DPC) Lorentz microscopy is a powerful technique for investigating magnetization distributions within magnetic thin films. Previously this imaging technique has only been used on microscopes with nonstandard electron optical configurations because of two conflicting requirements: (1) The electron beam must be focused to a very fine probe on the specimen to obtain a high spatial resolution. (2) The specimen cannot be in the magnetic field of the objective lens, as this would destroy the magnetic domain structures of interest. This paper will describe the implementation of the technique on a conventional microscope, a JEOL JEM 2000 FX fitted with an ASID 20 scanning attachment, which satisfies these two requirements. We have modified the controls for the lenses and deflection coils in the microscope to allow an electron probe of less than 40 nm to be formed using the three condenser lenses, with the objective lens off. A position sensitive quadrant detector, required for DPC imaging, is mounted on a sliding O-ring below the projector lens and can be moved in for DPC work or out for standard microscope operation. Attached to the microscope is a digital image acquisition system based on an IBM PC AT. This system is used to acquire signals from the four quadrants of the detector simultaneously. The signals are then mixed digitally to produce the DPC images and an incoherent bright-field image. These images can be further processed to produce vector maps of the in-plane magnetization distributions within the sample. The spatial resolution of 40 nm is less than that of the VG HB501 STEM vacuum generators (VG) HB501 scanning transmission electron microscope (STEM) previously used for DPC imaging. This is due to the larger emitting area of the LaB6 filament compared to the field emission gun of the VG. The LaB6 has a much lower brightness than the FEG and this necessitates long image acquisition times. DPC images and the corresponding vector map from a NiFe film will be shown to demonstrate the technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342134
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  • 6
    Electronic Resource
    Electronic Resource
    Zinc and copper in Asian pregnancies–is there evidence for a nutritional deficiency? (1985)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 92 (1985), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. In 92 Hindu Asians, 59% of them vegetarian, and 51 Europeans longitudinal measurements were made during pregnancy of the zinc and copper concentrations in plasma and hair together with urinary zinc excretion, as indices of their zinc and copper status. Maternal diets were assessed once at booking. Zinc intakes ranged from 3·1 to 16·9 mg/day, with average intakes least in vegetarian Hindus and most in Europeans. Average copper intakes ranged between 1·48 and 1·80 mg/day and were similar in the three patient groups. Both ethnic groups showed the pregnancy-associated fall in the plasma concentration of zinc and rise in that of copper but throughout the study Hindus had statistically significant lower levels of zinc and higher levels of copper than Europeans. Urinary zinc excretion was not only significantly lower throughout the study in Hindus than in Europeans but the increase in excretion which occurred after 20 weeks gestation was smaller. There were no ethnic differences in the zinc content of hair. Urinary zinc excretion correlated with both plasma zinc levels and dietary zinc. Mean birth-weight in the Hindus was 2912 g and 34% of infants were below the 10th centile, using the Aberdeen standards, compared with 6% of the European babies (mean birthweight 3349 g). No association was found between crude or adjusted birthweight and any of the measures of zinc or copper status in either ethnic group. The Hindus had an apparently lower average zinc status than the Europeans, but there was no evidence that this had acted as a nutritional constraint and was the cause of their slower rate of intrauterine growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1985.tb03066.x
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  • 7
    Electronic Resource
    Electronic Resource
    The relation between vaginal pH and the microbiological status in vaginitis (1985)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 92 (1985), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. The vaginal pH, microbial flora and presence of clue cells were investigated in 89 women who were seen a t a sexually transmitted diseases clinic with a vaginal discharge or because they were contacts of men with gonococcal or non-gonococcal urethritis or because they were seeking a routine examination. None of the women had received antibiotics for at least 4 weeks before examination. A clinically normal vaginal secretion was found in 21 (55%) of 38 women who had a vaginal pH of 5.0–5.5. while such a secretion was found in only 7 (14%) of 51 women who had a pH value of 6·0–7·5. Clue cells, Chlatmydia trachomatis and Mycoplasrna hominis were found two to three times more often in women with the higher pH value than in those with the lower value and Ureaplasma urealyticum and Trichomonas vaginalis also occurred more frequently in the former group. Furthermore. large numbers of M. hominis organisms (〈inlineGraphic alt="geqslant R: gt-or-equal, slanted" extraInfo="nonStandardEntity" href="urn:x-wiley:14700328:BJO1267:ges" location="ges.gif"/〉 106colour changing units/ml) were associated significantly with the higher pH value. However, there was no appreciable difference in the distribution of Candida albicans between the two groups. C. trachomatis but not the other micro-organisms was isolated most often from women who were taking oral contraceptives. The results indicate that a pH of 2.6.0 is strongly predictive of infection and may be more useful than the type of discharge in suggesting a need for confirmatory microbiological tests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1985.tb04874.x
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  • 8
    Electronic Resource
    Electronic Resource
    Concentrations of hypoxanthine, xanthme, undine and urate in amniotic fluid at caesarean section and the association of raised levels with prenatal risk factors and fetal distress (1983)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 90 (1983), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. Samples of amniotic fluid were obtained at caesarean section from 33 of 80 consecutive unselected patients in whom the membranes were intact. Concentrations of the ATP metabolites, hypoxanthine and xanthine, as well as uridine and urate were determined using high pressure liquid chromatography. Independent ‘clinical’ factors associated with reduced fetal growth and well-being were identified and the patients were assigned to one of three groups: those with no recognized risk, those with moderate risk and a small group of four patients with high risk. The mean hypoxanthine concentration was higher in the moderate-risk group than in the group with no risk. Two of the three patients with proteinuric hypertension in the high-risk group had normal hypoxanthine concentrations. There were seven patients with fetal distress, and concentrations of hypo xanthine, xanthine, uridine and urate were significantly higher in the three patients who had meconium stained amniotic fluid in addition to abnormal fetal heart rate tracings than in the remaining four who had fetal heart rate abnormalities only. It is suggested that fetal distress at emergency caesarean sections might be quantitated by such analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1983.tb09321.x
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  • 9
    Electronic Resource
    Electronic Resource
    Fetal urinary tract obstruction: is active intervention before delivery indicated? (1983)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 90 (1983), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. Obstruction of the urinary tract was diagnosed by ultrasound in four fetuses at 16—30 weeks: three of these diagnoses were confirmed after delivery; the fourth fetus had multicystic kidneys with hydroureter and hydronephrosis but no obstruction. The fetus with obstruction diagnosed at 16 weeks was terminated: it had lung hypoplasia with the prune-belly syndrome. The other two fetuses with obstruction were diagnosed at 25 and 34 weeks; the urinary tracts of both were drained for 5–14 days with reduction of distension. Both were born alive but that diagnosed at 25 weeks died of lung hypoplasia, the other survived, required nephrectomy and at the age of 3 is small but developing normally. Fetal urinary tract obstruction may prevent normal development of the lungs, be associated with other anomalies which cannot be diagnosed before delivery and retard infant development in survivors. Drainage of the dilated urinary tract does not harm the fetus or mother but has not been shown to improve neonatal survival or infant development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1983.tb08921.x
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  • 10
    Electronic Resource
    Electronic Resource
    High oestrogen excretion in pregnancy (1982)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 89 (1982), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. Fifty-one women with singleton pregnancies whose urinary oestrogen excretion was above the 95th centile of the hospital's reference range on two or more occasions were reviewed. The women did not differ from the general population in race, parity, age, height or weight gain during pregnancy, but they were slightly heavier. Fetal and placental weights were greater than the corresponding values in the general population, as were the volumes of urine containing the oestrogen, but none of these differences was sufficient to account for oestrogen excretion above the 95th centile. Eleven patients, has a glucose tolerance test, two of them had abnormal results and nine had normal results but heavy babies. Patterns of oestrogen excretion did not identify a high-risk population but the women with consistently high excretion gave birth to eight of the nine babies that weighed 〈inlineGraphic alt="geqslant R: gt-or-equal, slanted" extraInfo="nonStandardEntity" href="urn:x-wiley:14700328:BJO994:ges" location="ges.gif"/〉4 kg in this population. Twenty-two of the women had 23 subsequent pregnancies in which oestrogen excretion was measured: excretion was normal in 17, low in two and above the 95th centile in four.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1982.tb04653.x
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