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Peculiar magnetic domain walls produced in Heusler alloys, which have attracted renewed interest due to their potential application to actuators and spintronic devices, are studied here using electron holography. The observations reveal unexpectedly narrow magnetic domain walls, the width of which showed perfect agreement with that of the antiphase boundaries (APB, e.g., only 3 nm). While the results can be explained by the significant depression of ferromagnetism due to the local chemical disorder, the electron phase shift indicates that ferromagnetic correlation still remains in the APB region.

We performed magnetic imaging of Ni-based ferromagnetic shape memory alloys. The magnetic microstructure was revealed by Lorentz microscopy and electron holography, which are powerful tools based on transmission electron microscopy. Observations of Ni51Fe22Ga27 and Ni50Mn25Al12.5Ga12.5 alloys, both of which have an L21-ordered structure in the parent phase, demonstrated that the antiphase boundaries (i.e., a type of planer defects) caused significant changes in the magnetization distribution due to depression of the atomic order—actually, the magnetization in these alloys depends upon the degree of chemical order. We propose a method which estimates the important magnetic parameters (the magnetocrystalline anisotropy constant and exchange stiffness constant) based on transmission electron microscopy observations. This method should be useful in magnetic measurements of nanometer-scale areas, for which conventional techniques cannot be applied.

We have investigated the vortex dynamics for the ‘ratchet’ operation in a niobium superconductor via a direct imaging of Lorentz microscopy. We directly observe one-directional selective motion of field-gradient-driven vortices along fabricated channels. This results from the rectification of vortices in a spatially asymmetric potential under the oscillating magnetic field in a temporally symmetric manner. Based on the observation of the individual motion of vortices, we clarify the elementary process involved in this rectification.

Vortices in high-Tcsuperconductors have been predicted to behave in unconventional manners that reflect the layered structure of the materials. Our newly developed 1-MV field-emission electron microscope has opened the way to enable individual vortices to be observed inside high-Tcsuperconducting thin films. This makes it possible to investigate the inner structures of vortices, such as those trapped along tilted columnar defects and those of chain vortices that are formed when a magnetic field is obliquely applied with respect to the normal of the layer plane of the materials.

Familial adenomatous polyposis (FAP), which includes familial polyposis coli (FPC) and the Gardner syndrome (GS), is a genetically determined premalignant disease of the colon inherited by a locus (APC) mapping within 5q15–q22. To elucidate the role of 5q loss in FAP tumorigenesis, we analysed 51 colorectal tumors and seven desmoids from 19 cases of FPC and five GS patients, as well as 15 sporadic colon cancers. RFLP analysis revealed a high incidence of allelic deletion in hereditary colon cancers as well as in sporadic colon cancers with a peak at the APC locus. APC loss resulted primarily from interstitial deletion or mitotic recombination. Combined tumor and pedigree analysis in a GS family revealed loss of normal 5q alleles in three tumors, including a desmoid tumor, which suggests the involvement of hemizygosity or homozygosity of the defective APC gene in colon carcinogenesis and, possibly, in extracolonic neoplasms associated with FAP.

We investigated possible association of and linkage between HLA and familial polyposis coli (FPC). In 182 individuals from 66 pedigrees of FPC and 108 individuals from a normal population, HLA-A,-B, and-C antigens were determined. When the frequencies of HLA antigens in 66 unrelated patients and in normal controls were compared, no association of FPC with HLA was observed. For the linkage analysis, HLA haplotypes of 17 affected sib pairs were investigated by the affected sib pair method. The number of pairs which shared two, one, and no haplotypes identical by descent was not significantly different from the number expected with random occurrence (P>0.95). Finally, seven families were analyzed using Morton's sequential test. A maximum lod score of-0.056 at a recombination fraction of 0.4, and a lod of-3.089 at a recombination fraction of 0.05 were obtained. Therefore, there is neither an association of nor linkage between FPC and HLA.

The domain structure of zero magnetostrictive (Co 0.96 Fe 0.04 ) 79 Si 10 B 11 amorphous alloys was observed by both Lorentz electron microscopy and the newly developed technique of electron holography. The latter method clearly manifests, for the first time, the flow of magnetic lines of force both inside and outside an amorphous specimen.

Electron energy loss spectra were measured for Y2O3: Eu, Gd2O3: Eu, Y2O2S : Eu, La2O2S : Eu, Gd2O2S : Eu, YVO4: Eu and CaWO4: Pb. Strong loss-peaks due to interband transitions are observed. Since no correlation is found between cathode-ray efficiencies and the energies of the loss-peaks which presumably originate in plasma resonance, the plasmon excitation is not important in the understanding of the efficiencies.

A description is made of a grating optical system for extracting phase distribution from electron holograms, that has an extremely high stability and can eliminate system aberrations. Phase measurement is achieved with phase-shifting interferometry by stepping the grating laterally. The system is used to extract the phase distribution of a magnesium oxide crystal from its electron hologram.

Holographic interferometry in an electron microscope and its phase analysis technique are described. The fringe scanning method is used to gain high sensitivity in phase detection. An example of measuring a magnetic field of a fine particle is presented. The measurement accuracy for median filtering is about 1/70 fringe corresponding to the magnetic flux sensitivity of 6 × 10^−17 Wb. Noise reduction techniques are also discussed.

This paper describes interference microscopy using a liquid-crystal panel as a rewritable medium. This system makes it possible to observe the dynamic behavior of a magnetic field. Experimental results obtained while observing dynamic domain-wall motion in a thin permalloy film are shown.

The development of a coherent field-emission electron beam has made it possible to observe microscopic magnetic lines of force by detecting the electron-wave phase shifts that are due to vector potentials. Electron-holographic interference microscopy has been used to observe magnetic lines of force of magnetic vortices in superconductors, and Lorentz microscopy has been used to observe the dynamics of the vortices. The observation of vortices not only helps us understand the microscopic mechanism of flux pinning, which holds the key to practical applications of superconductors, but also clarifies fundamental phenomena of superconductivity which have implications for more general physical phenomena.

A method for correcting the aberration of an electron-objective lens during the holographic reconstruction stage is proposed. In this method, a liquid-crystal spatial-light modulator is used as a computer-controlled phase plate on the Fourier plane of an optical reconstruction system. The effective refractive index of the liquid crystals changes with the applied electric field because of the crystals’s birefringence. Thus the phase of light passing through the liquid-crystal spatial-light modulator can be flexibly modulated to compensate for wave aberration. Experimental results on adjusting the focus of the image wave reconstructed from an electron-image hologram of magnesium oxide particles are presented.

A method of reconstructing the three-dimensional electric-potential distribution of a microscopic object with electron-holographic interferometry is presented. A sequence of processing techniques is developed to obtain the projected phase proportional to the potential distribution. A modified backprojection algorithm is used to reconstruct a three-dimensional potential distribution from the projected potentials obtained at different projection directions. In an experiment this method is applied to reconstruct three-dimensional latex particles.

One can correct spherical aberration in a transmission electron microscope by using a newly developed aberration-correction method involving off-axis electron holography. In this method, a liquid-crystal spatial-light modulator (LC SLM) is employed during the holographic reconstruction step to compensate for spherical aberration. Application of this method to high-resolution off-axis electron holograms of fine gold particles is presented. The phase distribution of the corrected object wave is visualized by the Zernike phase-contrast method carried out with the same LC SLM.

Paternal age distribution for 1279 cases of Down's syndrome born in 1952–1968 was compared with the corresponding distribution for the general population, corrected for the maternal age as well as for the year of birth of the patients. Although there was no difference in the mean paternal age, the two distributions differed significantly, largely due to the excess of fathers aged 55 years and over and to the deficit of those aged 40–44 years in the patients born to mothers aged 30 years and over. The overall pattern of the relative incidence of Down's syndrome with advancing paternal age, with maternal age controlled, seems consistent with the hypothesis proposed by Stene et al. (1977). It increased from 0.8 for fathers aged 20–24 years slowly up to 1.2 for those aged 45–49 years, though with an intermediate drop to 0.8 at the age of 40–44 years, and then sharply to 2.4 for those aged 55 years and over. This rising pattern of the relative incidence with paternal age was essentially the same for the patients born in 1952–1960 and for those born in 1961–1968, although the slope was less steep in the latter than in the former group.

Magnetic vortices in superconductors were directly and dynamically observed by using a “coherent” field-emission electron beam. Their dynamics were observed by Lorentz microscopy. The interaction of vortices with both line- and point-defects was investigated by direct observation.

Recent studies have suggested a critical role of specific gene loss in several embryonic tumours1–6and certain adult cancers7–12. In retinoblastoma, hemizygosity or homozygosity of a recessive mutant allele results in the loss of normal gene product2–4, and this seems to cause the manifestation of the disorder. Familial polyposis coli (FPC) is a human autosomal dominant trait characterized by numerous adenomatous polyps of the colon and rectum, and a high incidence of colon carcinoma. Karyotype analyses have failed to detect specific deletion or translocation. We report the use of polymorphic DNA markers to look for the somatic loss of heterozygosity at specific loci. Investigation of 38 tumours from 25 FPC patients and 20 porad colon carcinomas from 19 patients, revealed frequent occurrence of allele loss on chromosome 22, with some additional losses on chromosomes 5, 6, 12q and 15. The FPC gene-linked DNA probe C11p11 also detected frequent allele loss in both familial and sporadic colon carcinomas but not in benign adenomas. These results suggest the possible involvement of more than one chromosomal locus in the development of familial and sporadic colon carcinomas.

SummaryThe case report is that of a 23-year-old female who suffered from Duchenne muscular dystrophy (DMD). Her maternal male cousin had classic DMD and her mother showed evidence of being heterozygous for the DMD gene. By using cultured skin fibroblasts and Epstein-Barr virus transformed lymphoblastoid cell line, her karyotype was identified to be a mosaic, 45,X/46,XX. Three previously reported cases with 45,X/46,XX manifested both DMD and Turner's syndrome, while the present case showed no clinical features of Turner's syndrome. No clinical features of Turner's syndrome may be related to the fact that the majority of lymphocytes and fibroblasts had 46,XX. On the other hand, it is considered that the paternal X chromosome has been preferentially lost by postzygotic non-disjunction and that the DMD gene from the maternal X chromosome is manifested in muscle cells.

SummaryA 2.5-year-old boy with a ring chromosome 10 was described. Clinical features included developmental retardation, short stature, mild mental retardation and cryptorchidism. He had a history of photohypersensitivity. By using PHA stimulated peripheral blood lymphocytes, Epstein-Barr virus transformed lymphoblastoid cell line and cultured skin fibroblasts, his karyotype was identified to be mos45,XY,−10/46,XY/46,XY,r(10) (p15.3q26.3).

SummaryDermatoglyphic examinations were undertaken on the dermal surfaces of two fetuses at the 20th and 22nd week, respectively, from the onset of the last menstrual periods. The fetuses were diagnosed as cases of trisomy 21 by amniocentesis, and abortions were induced.

SummaryHypervariable ‘minisatellite’ regions which are dispersed in the human genome show restriction fragment length polymorphisms (RFLPs) due to allelic differences in the number of tandem repeats containing the core sequence. Southern blot hybridization using minisatellite core probes produces various band patterns, which are completely individual-specific and of which few fragments are shared between two randomly selected individuals. If the band patterns are identical between twins, they must be monozygotic. We report here the use of minisatellite core probe for zygosity determination in five Japanese twin pairs and in a set of triplets.

SummaryThis paper reports a rare case of complex structural rearrangement involving four chromosomes. The patient, a five-year old girl, exhibits mild physical deformities, such as hypertelorism, blepharophimosis, brachydactyly and clinodactyly of both the second and fifth fingers. Using various banding techniques, the complicated multiple rearrangement could be interpreted as a unique combination of non-reciprocal translocation and insertion involving chromosomes 7, 10, 14 and 21.

SummaryA malformed male infant showed a mosaic trisomy 14 with a karyotype of mos 46,XY/46,XY,−14,+i(14q). The mosaicism was found both in peripheral blood cultures and in lymphoblastoid cells transformed by EB virus infection. His clinical picture was compared with those of 5 previously reported cases of trisomy 14 mosaicism, and the following common phenotypic features were noted: growth retardation, psychomotor delay, narrow or asymmetrical palpebral fissures, broad nose, low-set and dysplastic ears, high-arched palate, micrognathia, short neck, congenital heart disease, and undescended testes.

SummaryA further case of partial trisomy 2p inherited from a maternal balanced translocation with a karyotype of 46,XX,t(2;15)(p21;q26) is reported. The female patient had an unbalanced karyotype with duplication of the distal part of the short arm of chromosome 2 (region 2p21→2pter). On the basis of the cytogenetic finding, clinical features of this patient were compared with those of the reported two cases with the similar duplication of region 2p21→2pter. The clinical features common to the three cases were hypertelorism, triangular face, large abnormal ears, congenital heart defect and long fingers, but microcephaly, prominent nasal bridge and long toes noted in the reported cases were replaced with hydrocephalus, wide, flat nasal bridge and short toes in the present case.

The present paper describes observations concerning the growth of two different rat ascites tumors, MTK-sarcoma II and Takeda sarcoma, implanted in the same host. Two types of tumor cells inoculated in the same host affect each other; the mitotic rate of the tumor cells is strikingly decreased and their damage with consequent retardation of tumor growth is remarkable. Growth of Takeda sarcoma is inhibited by either co-existence or pre-existance of MTK-sarcoma II in the same host. In the pre-existence of Takeda sarcoma, the damage to tumor cells of both tumors and consequent retardation of the tumor growth are very remarkable, prolonging the life of tumor-bearing animals in many cases.

A 25-year-old male hermaphrodite with the sex chromosome constitution of 46,XX is reported. Clinical, endocrinological, pathological and cytogenetical studies are presented and discussed in comparison with findings in the so-called XX males reported in the literature.Some theories to explain the paradoxical occurrence of a testis in XX males and XX male hermaphrodites are mentioned and a possible aetiological relationship between these XX male syndromes and Klinefelter's syndrome is suggested.

The chromosome conditions were investigated in thirty cases of primary human tumors in two types of material, solid and effusion, by the use of the water-pretreatment squash method.

An electron-holographic interference microscope that produces a time-sequential interference micrograph at a TV rate is developed. In this system, the electron off-axis hologram detected with a TV camera is transferred to a liquid-crystal spatial light modulator as a video signal. The liquid-crystal spatial light modulator can function as a thin amplitude hologram or a thin phase hologram. Time-sequential interference micrograph is obtained at a TV rate by superimposition of a plane reference wave onto the reconstructed object wave. Experimental results for observing a dynamic domain-wall motion in thin Permalloy film are demonstrated.

A generalized phase-shifting algorithm is implemented in the electron-wave interferometry with a transmission electron microscope, based on simultaneous measurement of the initial phases of the interferograms. The initial phase of each interferogram that has inherent linear carrier fringes is calculated using the Fourier co-efiicients of the interferogram itself corresponding to the carrier-frequency. Taking advantage of this phase-shifting method in both spatial resolution and precision, the phase distribution of a biological weak phase object is successfully measured. This promises to be one of the most spectacular application fields for this new technology.

Individual vortices in superconductors are directly observed with our holography electron microscope. Vortices cannot be viewed as an electron micrograph, but only as a holographic interference micrograph or a defocused micrograph (Lorentz micrograph), since vortices are phase objects to the illumination electron beam. Since the flux itself, and not its replica, is detected, even the dynamic behavior can be observed. The dynamics of vortices in a Nb thin film can be observed in real time when the sample conditions, such as the temperature or the applied magnetic field, change.

The phenomenon of ferromagnetic domain switching, which occurred in a colossal magnetoresistive manganite La0.25Pr0.375Ca0.375MnO3, was studied by sophisticated transmission electron microscopy techniques. Lorentz microscopy observations revealed the size dependence of the magnetization reversal behaviors. A small single-domain (70 nm) exhibited a direct switching process to another single-domain form, while a large single domain (150 nm) showed a multiple-domain configuration before the transformation to another single-domain state. We also demonstrated significant magnetic interaction in an assembly of single domains; i.e., neighboring single domains underwent magnetization reversal simultaneously. The results provide useful information for a deeper understanding of the switching process in a single-domain state, which can be observed in many advanced materials related to magnetic data storage media.

We developed a 1-MV field-emission transmission electron microscope to help in further improving electron holography, Lorentz microscopy, and high-resolution electron microscopy. This microscope is characterized by an electron beam having the highest brightness ever, 2×1010A/cm2, and by the highest lattice-resolution below 0.5 Å. These two features were attained by minimizing the mechanical vibration of the whole column and by improving the stability of both the electron beam and the high voltage. If the tiny electron source located at the top of the 7-m-high microscope moves by as little as a fraction of the source size, 50 Å in diameter relative to the column, due to mechanical vibration or beam deflection by the AC magnetic fields, the beam brightness will be greatly degraded. If the ripples ΔE of the high-voltage E exceed ΔE/E = 5 × 10−7/min, then the inherent monochromatic feature of the beam is deteriorated by the increase in energy spread.Through the preliminary experiments testing the vibration and magnetic shielding of the acceleration tube as well as the high stability of the high voltage, and through the numerical simulations on the vibration modes of the whole column, we were led to the conclusion that the microscope must be separated into three parts that are connected by cables.

Bright and coherent electron beams have been opening new frontiers in science and technology. So far, we have developed several field-emission transmission electron microscopes (FE-TEM) with increasing accelerating voltages to provide higher beam brightness. By using a 200-kV FE-TEM and electron holography techniques, we directly confirmed the Aharonov-Bohm effect. A 350-kV FE-TEM equipped with a low-temperature specimen stage enabled us to observe moving vortices in superconductors.2 Most Recently, we have developed a new 1-MV FE-TEM with a newly designed FE gun to obtain an even brighter and more coherent electron beam.Electron beam brightness, Br,defined in Figure 1,is suitable for measuring the performance of electron guns, since both lens aberrations and mechanical/electrical vibrations contribute to a decrease in beam brightness, and beam coherency is proportional to (Br)1/2.Therefore, we optimized design of the illuminating system and its operation by maximizing the electron beam brightness.

Tiny magnetic vortices hold the key in practical applications of superconductors, since the dynamic behaviors of vortices at pinning centers determine the critical current. These vortices have become observable directly and dynamically by using a “coherent” field-emission electron beam: The magnetic lines of force of vortices can be quantitatively observed as contour fringes in an electron-holographic interference micrograph. The change in the vortex radius could actually be measured when the temperature of a superconducting thin film changed. Vortices were also dynamically observed in a Lorentz micrograph. Both vortices and defects in the thin film can be observed simultaneously with this method, though the defects image is blurred.This paper reports the dynamic observation of vortices at defects when the applied magnetic field changes. A superconducting Nb thin film, set on a low-temperature stage, is tilted 45° to an incident beam of 300kV electrons (see Fig. 1), and an external magnetic field is applied in the horizontal direction. When an electron beam passes through the vortices, their magnetic fields deflect the electron beam. Therefore, when observed in the lower plane, a vortex can be viewed as a pair of black and white spots.

Blakemore1found aquatic bacteria that swim along magnetic lines of force. Such bacteria have small particles of magnetite (magnetosomes) within them2,3of various shapes3–5. We describe here the morphology and structure of bacterial magnetosomes investigated by high-resolution electron microscopy. From direct observation of various kinds of lattice images, the particles are determined to be single crystals with a hexagonal prism shape truncated by {111} planes. The lattice spacings measured agree with those of magnetite.

Magnetic vortices in superconductors have become directly and dynamically observable[l] by Lorentz microscopy in our 300 kV field-emission TEM[2]. Since material defects can also be observed simultaneously though the images are defocused, the microscopic flux pinning mechanism can be directly observed. Using this technique, we observed when and how vortices trapped at artificial defects were depinned.Artificial point defects were produced by the irradiation of a focused Ga ion beam. Electron microscopy revealed that the defect consisted of a pit 300 Å in radius surrounded by entangled dislocations. The depth of a pit increased with the ion dose.We first investigated the pinning force of individual defect: by observing the depinning of vortices from defects produced with various ion-doses. When a force was exerted on vortices trapped at the defects by changing the magnetic field and increased, we found that the pinning force of defects increased with the ion doses.

Magnetic vortices in superconductors have become directly and dynamically observable[l] by Lorentz microscopy in our 300 kV field-emission TEM[2]. Since material defects can also be observed simultaneously though the images are defocused, the microscopic flux pinning mechanism can be directly observed. Using this technique, we observed when and how vortices trapped at artificial defects were depinned.Artificial point defects were produced by the irradiation of a focused Ga ion beam. Electron microscopy revealed that the defect consisted of a pit 300 Å in radius surrounded by entangled dislocations. The depth of a pit increased with the ion dose.We first investigated the pinning force of individual defect: by observing the depinning of vortices from defects produced with various ion-doses. When a force was exerted on vortices trapped at the defects by changing the magnetic field and increased, we found that the pinning force of defects increased with the ion doses.

A novel system of electron interferometry and holography using two electron biprisms has been developed. The first biprism is installed in the image plane of the objective lens and the second one is set behind the first magnifying lens, inside the shadow area of the first biprism. The system can independently control two important parameters for interferograms and holograms, the fringe spacing and interference width. Thus, it gives us more flexibility on performing electron interferometry and holography. The good performance of the system was demonstrated using a 1MV field-emission electron microscope. We introduce a variety of optical set-ups for the system and explain the advantages of each set-up in detail, with experimental results.

Profile magnetic configuration of a quantized flux line and flux‐line lattice penetrating a type‐II superconductor thin foil, niobium, was observed by electron holography and Lorentz microscopy using a 300 kV field‐emission electron microscope. Each single flux line was distributed periodically as lattice structure in the mixed state just below its critical temperature of 8.5 K, while at low temperature of 5 K the flux lines were weakly bound as bundles. In order to observe the flux‐line distribution over a wide area, discrete Fourier transform reconstruction in the holography was extended for a rectangular area without loss of information and data precision.

A newly developed 1 MV field‐emission transmission electron microscope has recently been applied to the field of superconductivity by utilizing its bright and monochromatic field‐emission electron beam. This microscope allows individual magnetic vortices inside high‐Tc superconductors to be observed, thus, opening the way to investigate the unusual behaviour of vortices, which reflects the anisotropic layered structure of these superconducting materials. One example is the observation of the arrangements of chain vortex lines that are formed when a magnetic field is applied obliquely to the layer plane of the materials.

A bright field‐emission electron beam was used to observe magnetic vortices in superconducting thin films by electron holography and Lorentz microscopy. Especially in Lorentz microscopy, the dynamic behaviour of individual vortices became directly observable for the first time. As material defects can be observed simultaneously, the vortex pinning phenomena, which are indispensable for practical applications of superconductors, can now be observed microscopically and dynamically. This study revealed the existence of various kinds of vortex movements, such as individual hopping among defects, vortex rivers, and vortex–antivortex pair annihilation.

We developed a 1 MV field-emission transmission electron microscope. This paper reports details and specifications of the instrument. The microscope was designed to obtain a bright and coherent electron beam by using the field emission gun equipped with a pre-accelerating magnetic lens and the highvoltage power supply with high stability (0.5 ppm min−1). Using this microscope, the brightness of 1.8�1010 A cm−2 sr−1 and the lattice resolution of 49.8 pm were attained.

Interaction of vortices (quantized magnetic flux lines) and antivortices(oppositely polarized flux lines) in a superconductor, such as pair annihilation,was directly observed by Lorentz microscopy with a 300-kV field emission electron microscope. When the direction of the magnetic field applied to a Nb film was reversed, antivortices were created and coexisted to interact with original vortices in cases such as when (i) the film was not uniform in thickness and had morphological undulations and when (ii) the strong pinning centres were distributed, even in a fairly uniform film. Vortices and antivortices were found to successively attract and then annihilate each other.Different behaviours of the vortex-antivortex interaction were observed for the above two cases

A field emission electron microscope with highly stabilized gun and illuminating system was developed. Several experiments were made to demonstrate the high performance of the microscope. The brightness of the beam was more than that of the conventional ones, which feature was demonstrated by taking 300 Fresnel fringes and 3,000 bi-prism fringes. Furthermore, monochromatic feature of the microscope makes the effect of chromatic aberration smaller and the half-spacing fringes of nickel {220} planes (1/2 d220=62Å) were observed.

Single magnetic-domain particles of barium ferrite and iron are directly observed by electron holographic microscopy. Holograms of barium ferrite particles about 1 μm in size are formed without using the objective lens but with controlling the intermediate lens. Holograms of iron particles with diameters of several tens of nanometers are also formed using a specially designed low magnetic-field pole piece. The phase distribution of the object electron wave is digitally reconstructed by the Fourier transform method and then converted to interference micrographs, in which magnetic flux lines are directly observed. Isolated barium ferrite particles in the single magnetic-domain state are observed in these interference micrographs directly. A string of iron particles in the single-domain state is also observed.