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1.
Phys Rev Lett ; 123(4): 045501, 2019 Jul 26.
Artículo en Inglés | MEDLINE | ID: mdl-31491265

RESUMEN

Understanding the local atomic order in amorphous thin film coatings and how it relates to macroscopic performance factors, such as mechanical loss, provides an important path towards enabling the accelerated discovery and development of improved coatings. High precision x-ray scattering measurements of thin films of amorphous zirconia-doped tantala (ZrO_{2}-Ta_{2}O_{5}) show systematic changes in intermediate range order (IRO) as a function of postdeposition heat treatment (annealing). Atomic modeling captures and explains these changes, and shows that the material has building blocks of metal-centered polyhedra and the effect of annealing is to alter the connections between the polyhedra. The observed changes in IRO are associated with a shift in the ratio of corner-sharing to edge-sharing polyhedra. These changes correlate with changes in mechanical loss upon annealing, and suggest that the mechanical loss can be reduced by developing a material with a designed ratio of corner-sharing to edge-sharing polyhedra.

2.
Opt Express ; 24(5): 4365-4374, 2016 Mar 07.
Artículo en Inglés | MEDLINE | ID: mdl-29092264

RESUMEN

Ge on Si micro-disk, ring and racetrack cavities are fabricated and strained using silicon nitride stressor layers. Photoluminescence measurements demonstrate emission at wavelengths ≥ 2.3 µm, and the highest strained samples demonstrate in-plane, tensile strains of > 2 %, as measured by Raman spectroscopy. Strain analysis of the micro-disk structures demonstrate that shear strains are present in circular cavities, which can detrimentally effect the carrier concentration for direct band transitions. The advantages and disadvantages of each type of proposed cavity structure are discussed.

3.
Ultramicroscopy ; 217: 113069, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-32659452

RESUMEN

We outline a simple routine to correct for non-uniformities in the energy dispersion of a post-column electron energy-loss spectrometer for use in scanning transmission electron microscopy. We directly measure the dispersion and its variations by sweeping a spectral feature across the full camera to produce a calibration that can be used to linearize datasets post-acquisition, without the need for reference materials. The improvements are illustrated using core excitation electron energy-loss spectroscopy (EELS) spectra collected from NiO and diamond samples. The calibration is rapid and will be of use in all EELS analysis, particularly in assessments of the chemical states of materials via the chemical shift of core-loss excitations.

4.
J Microsc ; 230(Pt 3): 445-54, 2008 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-18503671

RESUMEN

Reliable EBSD mapping of 90 degree domains in a tetragonal ferroelectric perovskite has been achieved for the first time, together with reliable automated orientation determination from TEM-Kikuchi patterns. This has been used to determine misorientation angles at 90 degree domain boundaries and thus local c/a ratios. The sources of orientation noise/error and their effects on the misorientation angle data have been thoroughly analyzed and it is found that this gives a cosine distribution of misorientation angles about the mean with a characteristic width related to the width of the orientation noise distribution. In most cases, a good agreement is found between local c/a ratios and global measurements by X-ray diffraction, but some clear discrepancies have also been found suggesting that real local variations are present, perhaps as a consequence of compositional inhomogeneities.


Asunto(s)
Cristalografía/métodos , Plomo/química , Titanio/química , Difracción de Rayos X , Circonio/química , Cristalización , Plomo/análisis , Microscopía Electrónica , Titanio/análisis , Circonio/análisis
5.
Ultramicroscopy ; 182: 44-53, 2017 11.
Artículo en Inglés | MEDLINE | ID: mdl-28654827

RESUMEN

In this paper we report quantitative measurements of the imaging performance for the current generation of hybrid pixel detector, Medipix3, used as a direct electron detector. We have measured the modulation transfer function and detective quantum efficiency at beam energies of 60 and 80keV. In single pixel mode, energy threshold values can be chosen to maximize either the modulation transfer function or the detective quantum efficiency, obtaining values near to, or exceeding those for a theoretical detector with square pixels. The Medipix3 charge summing mode delivers simultaneous, high values of both modulation transfer function and detective quantum efficiency. We have also characterized the detector response to single electron events and describe an empirical model that predicts the detector modulation transfer function and detective quantum efficiency based on energy threshold. Exemplifying our findings we demonstrate the Medipix3 imaging performance recording a fully exposed electron diffraction pattern at 24-bit depth together with images in single pixel and charge summing modes. Our findings highlight that for transmission electron microscopy performed at low energies (energies <100keV) thick hybrid pixel detectors provide an advantageous architecture for direct electron imaging.

6.
Cancer Res ; 49(11): 3007-14, 1989 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-2470500

RESUMEN

Undifferentiated cervical carcinomas vary considerably in their intercellular organization and patterns of invasion. In spite of its clinical significance, the basis for such variation is poorly understood. We investigated the cellular properties that may be responsible for this diversity, using as a model two human cervical carcinoma cell lines that were derived from the same tumor specimen and the same clone. It was shown previously that, in spite of their common origin, each line forms a histologically distinct type of undifferentiated carcinoma when heterotransplanted in vivo: cells of line C-4I grow as compact expanding masses with central necrosis, while tumors of line C-4II infiltrate host tissues as small, well-vascularized, dispersed cell groups. The characteristic behavior of each line was retained in culture, where C-4I cells formed highly multilayered cohesive colonies, while C-4II cells formed diffuse, monolayered colonies and shed into the culture medium. These observations as well as ultrastructural data suggested that each line may be arrested at a different stage of stratified squamous differentiation. In the present study, this hypothesis was tested by examining specific differentiation markers. An analysis of the cultures by immunofluorescence microscopy and immunoblotting revealed that keratin was more abundant in the compact C-4I line than in the dispersed C-4II line. C-4I cells expressed keratins 5, 6, 8, 16, 18, and 19, while C-4II expressed only keratins 8, 16, 18, and 19. In the multilayered C-4I colonies, involucrin-positive cells occurred in the apical cell layers only. In C-4II, involucrin-positive cells occurred in monolayers and domes, and they were most consistently located apically in crowded cultures. Laminin was secreted by both lines, but only C-4II cells deposited a fibronectin matrix. The results suggest that C-4I cells resemble normal cervical cells at the spinous stage of stratified squamous differentiation, while C-4II cells resemble basal/suprabasal cells. The different growth patterns of the tumors, formed by the lines in vivo, therefore likely reflect functional and behavioral differences that normally exist between spinous and basal cervical epithelial cells. The results suggest that differentiation-related functional properties may lead to histological diversity among cervical carcinomas that are categorized as undifferentiated by histopathological criteria.


Asunto(s)
Carcinoma/análisis , Fibronectinas/análisis , Queratinas/análisis , Laminina/análisis , Proteínas de Neoplasias/análisis , Precursores de Proteínas/análisis , Neoplasias del Cuello Uterino/análisis , Carcinoma/patología , Carcinoma/ultraestructura , Diferenciación Celular , Femenino , Humanos , Células Tumorales Cultivadas , Neoplasias del Cuello Uterino/patología , Neoplasias del Cuello Uterino/ultraestructura
7.
Biochim Biophys Acta ; 427(1): 238-50, 1976 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-816380

RESUMEN

Precipitation of serum proteins of the house mouse, Mus musculus, by trichloroacetic acid and redissolving part of the precipitate in ethanol proved to be a very efficient procedure for isolating mouse serum albumin. Electrophoretic and immunoelectrophoretic analyses showed only albumin to be dissolved at a detectable level in the ethanol. Electrophoretic studies also showed that isolated albumin underwent polymerization with the polymers being readily separated by exculsion chromatography on Sephadex G-150. Comparisons of such physicochemical characteristics of the albumin monomers, as extinction coefficient (5.2), sedimentation coefficient (4.5 S), molecular weight (67 000), free sulfhydral groups per molecule (0.6) and amino acid composition with albumins of other mammals showed strong similarity. Finally, a comparison was made between the common mouse albumin or albumin A, and a variant, albumin C. The two types of albumin molecules were found very similar in all respcets except electrophoretic migration.


Asunto(s)
Albúmina Sérica , Aminoácidos/análisis , Animales , Electroforesis en Gel de Almidón , Inmunodifusión , Inmunoelectroforesis , Sustancias Macromoleculares , Ratones , Ratones Endogámicos C3H , Peso Molecular , Conformación Proteica , Albúmina Sérica/aislamiento & purificación , Especificidad de la Especie
8.
Nanoscale Res Lett ; 10(1): 407, 2015 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-26474888

RESUMEN

The atomic structure and chemistry of thin films of Bi(Fe,Mn)O3 (BFMO) films with a target composition of Bi2FeMnO6 on SrTiO3 are studied using scanning transmission electron microscopy imaging and electron energy loss spectroscopy. It is shown that Mn(4+)-rich antiphase boundaries are locally nucleated right at the film substrate and then form stepped structures that are approximately pyramidal in three dimensions. These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å. Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is much closer to bulk values for BFMO. This suggests that to improve the crystallographic perfection of the films whilst retaining the strain state through as much of the film as possible, ways need to be found to prevent nucleation of the antiphase boundaries. Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3 on the SrTiO3 substrate to minimise any Mn-Ti interactions.

9.
Am J Clin Pathol ; 98(2): 240-2, 1992 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-1510037

RESUMEN

Investigation of a patient with an unexpected prolonged activated partial thromboplastin time showed on repeat testing that the patient had normal coagulation times, but had been preceded on the automated coagulation analyzer run (ACL 300R--Instrumentation Laboratory, Lexington, MA) by a heparin-contaminated apheresis line sample taken from a different patient. Heparin carryover was suspected, and subsequent experiments showed that ex vivo heparinization of normal plasmas will produce similar effects in following normal plasma samples in a test series. This effect increases with the baseline activated partial thromboplastin time and the heparin concentration. It is recommended that coagulation analyzers that are susceptible to carryover be cleaned after testing of plasmas likely to have heparin concentration of more than 5 x 10(3) U/L. Furthermore, when using analyzers of this type, investigation of an unexplained activated partial thromboplastin time must include a review of the preceding samples tested, particularly when duplicate testing has been discontinued.


Asunto(s)
Pruebas de Coagulación Sanguínea/instrumentación , Contaminación de Equipos , Heparina , Niño , Errores Diagnósticos , Humanos , Masculino , Tiempo de Tromboplastina Parcial , Valores de Referencia
10.
Am J Clin Pathol ; 100(2): 123-6, 1993 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-8356944

RESUMEN

The standard reference method for hemoglobin determination for years has been the photometric quantitation of cyanmethemoglobin. Other existing methods have not gained popularity in North America. In an attempt to eliminate hazardous cyanide waste, a method to determine the hemoglobin concentration in whole blood using sodium lauryl sulfate has been devised and recently was released as a commercial reagent. The authors compare this new method with the cyanmethemoglobin method using two hematology analyzers. Their results show that there is excellent correlation between the two methods (r2 = 0.996). In addition, other elements of the complete blood count also show good correlation. Thus, it was confirmed that the sodium lauryl sulfate method of estimating hemoglobin concentration is an appropriate alternative to the cyanmethemoglobin method and avoids the generation of toxic wastes.


Asunto(s)
Hemoglobinometría/métodos , Hemoglobinas/análisis , Dodecil Sulfato de Sodio , Recuento de Células Sanguíneas , Estudios de Evaluación como Asunto , Humanos , Metahemoglobina/análogos & derivados
11.
Ultramicroscopy ; 99(2-3): 103-13, 2004 May.
Artículo en Inglés | MEDLINE | ID: mdl-15093937

RESUMEN

Fresnel fringe analysis is shown to be unreliable for grain boundaries in yttrium-doped alumina: the determined thicknesses do not agree well with those measured from high resolution transmission electron microscopy (HRTEM), the asymmetry between under- and overfocus is very large, and Fresnel fringes are sometimes shown at boundaries which contain no amorphous film. An alternative approach to the analysis of HRTEM images of grain boundary films is demonstrated: Fourier filtering is used to remove the lattice fringes from the image thereby significantly enhancing the visibility of the intergranular films. The apparent film thickness shows a discrepancy between measurements from the original HRTEM image and the filtered image. It was shown that fringe delocalisation and diffuseness of the amorphous/crystalline interfaces will lead to a significant underestimate of the thickness in unprocessed HRTEM images. In contrast to this, the average thickness can be much more accurately measured from the Fourier-filtered image, provided the boundary is oriented accurately edge-on.

12.
Can J Public Health ; 88(2): 80-4, 1997.
Artículo en Inglés | MEDLINE | ID: mdl-9170683

RESUMEN

The iron status and feeding practices of 434 infants in Vancouver were determined at 39 +/- 1 week of age. Iron-deficiency anaemia (haemoglobin < or = 101 g/L, or < or = 110 g/L with two or three abnormal results from tests of serum ferritin, zinc erythrocyte protoporphyrin and total iron binding capacity) occurred in 7% of infants. Low iron stores (serum ferritin < 10 micrograms/l) occurred in about 24% of infants. Iron-deficiency anaemia was significantly associated (p < 0.001) with duration of breastfeeding. The prevalence of iron-deficiency anaemia among infants breastfed for 8 months was 15%. At 39 weeks (9 months) of age, about 5% and 13% of the infants were bottle-fed with cows milk or low iron infant formula, respectively, and this was also significantly associated (p < 0.02) with low iron stores. Iron-fortified infant cereals had been introduced to 95% of the infants by six months of age. This study shows iron-deficiency anaemia is a problem among a significant number of nine-month-old infants in Canada, and is not explained by failure to introduce iron-fortified infant cereals.


Asunto(s)
Anemia Ferropénica/epidemiología , Canadá/epidemiología , Humanos , Incidencia , Lactante , Fenómenos Fisiológicos Nutricionales del Lactante , Hierro/sangre , Estilo de Vida , Tamizaje Masivo , Prevalencia
16.
J R Coll Surg Edinb ; 45(6): 392-7, 2000 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-11153431

RESUMEN

In 1791, the year in which Mozart died, there was born in Edinburgh a man who had some of the attributes of genius and whose name, but for a trivial mischance, might today occupy a distinguished place in the illustrious history of the Edinburgh Medical School. Instead of this, his career was shattered and his reputation blighted forever by fortuitous association with a gruesome and macabre scandal the story of which is as shocking today as it was to our forebears 172 years ago. To the world at large the memory of this man, Robert Knox, is almost as infamous as Bluebeard or Jack the Ripper, while his outstanding abilities and substantial achievements are largely forgotten, and yet he was never formally accused, far less convicted of any crime.


Asunto(s)
Anatomía/historia , Homicidio/historia , Museos/historia , Facultades de Medicina/historia , Educación Médica/historia , Robo de Tumbas/historia , Historia del Siglo XVIII , Humanos , Escocia
17.
World J Surg ; 14(1): 19-27, 1990.
Artículo en Inglés | MEDLINE | ID: mdl-2407034

RESUMEN

Chronic pancreatitis was a recognized clinical entity in the British Isles at the beginning of the twentieth century, but until little more than 30 years ago, it was considered to be a rare condition and received scant attention from British surgeons. During the second half of the twentieth century, the incidence of the disease in the British Isles has increased significantly and alcohol abuse has become, by far, the most important etiological factor. Per capita consumption of alcohol in the British Isles has increased very markedly in the past 30 years and alcohol abuse is becoming a major social problem, but, although chronic pancreatitis is more common now than it was 30 years ago, the increase in its incidence is a good deal less than might be expected. British surgeons are agreed that intractable pain is the cardinal indication for surgical intervention in chronic pancreatitis and success depends on selection of the operative procedure most appropriate to the pathological state of the pancreas and, in particular, of its ductal system. In recent years, British surgeons in highly specialized units have become more radical in their approach to the treatment of chronic pancreatitis with total pancreatectomy in selected patients currently being advised more frequently than in previous decades.


Asunto(s)
Pancreatitis/cirugía , Alcoholismo/complicaciones , Enfermedad Crónica , Femenino , Humanos , Masculino , Pancreatitis/etiología , Reino Unido
18.
Surg Gynecol Obstet ; 163(2): 117-20, 1986 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-3738709

RESUMEN

In a retrospective review of 108 patients treated for perforator insufficiency, we evaluated 99 limbs of 80 returning patients, 80 per cent of whom had had the operation at least five years before. In 64 of the patients reviewed, good to excellent results were achieved. These patients did not have a recurrence of the ulceration, eczema or prominent varices. Two instances of recurrent ulceration and one of incipient ulceration were discovered in the study. Wound complications were a problem because of the nature of the skin problems encountered. We concluded that division of incompetent perforating veins combined with excision of the superficial venous system yields good results.


Asunto(s)
Insuficiencia Venosa/cirugía , Adulto , Anciano , Comportamiento del Consumidor , Femenino , Humanos , Cuidados Intraoperatorios , Úlcera de la Pierna/complicaciones , Ligadura/métodos , Masculino , Métodos , Persona de Mediana Edad , Cuidados Posoperatorios , Complicaciones Posoperatorias , Estudios Retrospectivos , Vena Safena/cirugía , Várices/cirugía
19.
Biochem Genet ; 14(1-2): 67-73, 1976 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-1259705

RESUMEN

Two albumins, albumin A from C3H mice and albumin C isolated from descendents of the wild mice in which the variant was first uncovered, were found to differ in their electrophoretic properties. Albumin C was shown to bind two more H+ ions than albumin A at pH 5.4. Peptide mapping after trypsin digestion revealed that albumin C had three peptides (TP-C1, TP-C2, and TP-C3) which were missing in albumin A. The latter likewise had a peptide (TP-A1) which was not found in albumin C. An amino acid analysis of the variant peptides suggests that TP-A1 had been split into TP-C1 and TP-C2 on digestion with trypsin, because a glutamic acid in TP-A1 was replaced by a lysine. This change would also appropriately alter the electrophoretic properties of albumin C. No obvious counterpart was discovered for TP-C3 of albumin C in albumin A.


Asunto(s)
Variación Genética , Albúmina Sérica , Aminoácidos/análisis , Animales , Glutamatos/análisis , Lisina/análisis , Ratones , Ratones Endogámicos C3H , Fragmentos de Péptidos/análisis , Tripsina
20.
Biol Reprod ; 44(4): 717-24, 1991 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-1710511

RESUMEN

The ovarian surface epithelium (OSE) is known to contribute to postovulatory repair of the ovarian cortex by proliferation and migration over the site of follicular rupture, and by deposition of a basement membrane. We examined the production of other extracellular matrix components in culture by OSE cells of the rat (ROSE), using immunofluorescence microscopy, electron microscopy, and proline incorporation. We compared recently explanted cells in low passage, the immortal line ROSE 239, whose growth pattern resembles low passage cultures, and the immortal line ROSE 199, which forms ridges and papillae. The epithelial nature of all three cell types was confirmed by the presence of keratin and laminin. All three cell types secreted collagen types I and III and at least one (ROSE 199) produced highly polymerized banded fibrils, which are characteristic for stromal or interstitial extracellular matrix. Simultaneous production of collagen types I and III, keratin, and laminin by cloned subpopulations ruled out an origin of the lines in mixed epithelial/fibroblast populations. The results demonstrate that OSE has the capacity to synthesize major components of connective tissue stroma. They suggest that this epithelium, in addition to its postulated proteolytic role, may also express synthetic activity in the remodelling of the ovarian cortical stroma. A capacity of OSE cells to produce stromal components autonomously might be an important factor in the formation of ovarian surface papillae and in neoplastic progression of OSE-derived ovarian carcinomas.


Asunto(s)
Ovario/metabolismo , Animales , Células Cultivadas , Colágeno/metabolismo , Tejido Conectivo/metabolismo , Epitelio/metabolismo , Matriz Extracelular/metabolismo , Femenino , Queratinas/metabolismo , Neoplasias Ováricas/etiología , Neoplasias Ováricas/metabolismo , Neoplasias Ováricas/patología , Ovario/ultraestructura , Ratas
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