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Notes: Silver particles of average diameters in the range 10.3–25.7 nm have been grown within a gel medium by an electrodeposition technique. Detailed optical absorption characteristics in the wavelength range 250–600 nm have been investigated for nanocomposites comprising these particles dispersed in a polystyrene matrix. Absorption maximum occurs at a wavelength around 350 nm, which increases as the metal particle size is increased. Mie theory with the incorporation of a distribution of particle size gives remarkable agreement with the experimental data. The electrical conductivity as extracted from the theoretical analysis for particles with diameters ∼3 nm is found to be less than Mott's minimum metallic conductivity. This indicates the possibility of a metal insulator transition in this system, which appears to be consistent with earlier electrical conductivity measurements. © 1998 American Institute of Physics.

Notes: We report on the effects of the wet and dry oxidation processes on the interfacial roughness and time dependent dielectric breakdown (TDDB) characteristics of the poly-Si/SiO2/Si(100) trilayer. The interface roughness of the oxide layers buried under a thick poly-Si electrode has been investigated using an x-ray reflectivity technique. Analysis of x-ray reflectivity data for the trilayer samples and for a bare oxide film shows that interface roughness of poly-Si electrode/SiO2 interfaces depends on oxidation process while oxide layers have smooth SiO2/Si-subtstrate interfaces. TDDB of the SiO2 layer has also been observed to depend on the oxidation process, indicating that the interface roughness is a crucial factor affecting the TDDB characteristics. The wet oxidized SiO2 film is more stable to dielectric breakdown and has smoother interfaces than the dry oxidized sample. © 1998 American Institute of Physics.

Notes: Composites containing copper particles with nanometer dimensions in a silica gel medium have been synthesized by an electrodeposition technique. The precursor composition of the gel was in the system Cu(NO3)2–SiO2 and the copper particle diameters were in the range of 3.2–11.4 nm. The dc electrical resistivity of pellets obtained from the nanocomposite powders was measured in the temperature range of 110–300 K. A temperature dependence with a fractional exponent of 0.25 was observed. This behavior has been explained on the basis of a variable range hopping mechanism. © 1998 American Institute of Physics.

Notes: Composites of nanometer-sized copper metal with diameters varying from 3.2 to 11.4 nm dispersed in a silica gel medium were synthesized by an electrodeposition method. The ac conductivity and dielectric dispersion of these nanocomposites were measured over the frequency range 0.2 kHz–1.5 MHz at temperatures varying from 150 to 300 K. The ac conductivity showed a frequency dependence of ∝ωn where ω is the angular frequency and n∼0.62 the latter being temperature independent. The quantum mechanical tunneling model was used to explain this result. The dielectric modulus data were analyzed on the basis of a stretched exponential relaxation function. The values of the exponent β as extracted from such analysis were found to be in the range 0.31–0.42 and were temperature independent for different gel compositions. The activation energies were estimated from the temperature variation of frequency at which the imaginary part of the dielectric modulus was maximum. The activation energy value ∼0.24 eV could be explained satisfactorily on the basis of an electron tunneling mechanism. © 1998 American Institute of Physics.

Notes: Aims: To describe the clinicopathological and immunophenotypic features of 25 cases of Kikuchi–Fujimoto disease (K–F), which remains a poorly recognized entity and is still frequently confused with malignant lymphoma, and to discuss the main diagnostic problems experienced by the referring pathologist.〈section xml:id="abs1-1"〉〈title type="main"〉Methods and resultsHaematoxylin and eosin sections of 27 lymph node biopsies were re-examined. Immunostains for B-lymphocytes, T-lymphocytes and macrophages were performed. Clinical and follow-up data were obtained through a questionnaire to the referring pathologist or from the patients' notes where available. The suggested initial diagnoses are discussed. The lymph nodes showed a necrotizing process characterized by patchy or confluent areas of necrosis associated with karyorrhexis and absence or paucity of granulocytes. This was associated with a proliferation of large blastic cells consisting of a mixture of T-lymphocytes and histiocytes. Fragmentation of the biopsy was a frequent feature. The diagnosis of K–F was suggested by the referring pathologist in three cases only. The most common suggested diagnosis was that of a non-Hodgkin's lymphoma.〈section xml:id="abs1-2"〉〈title type="main"〉ConclusionThis series documents continuing difficulties in the diagnosis of Kikuchi–Fujimoto disease in the UK and emphasizes that cases are still being mistakenly diagnosed as malignant lymphomas. The diagnosis of Kikuchi–Fujimoto disease merits active consideration in any nodal biopsy showing fragmentation, necrosis and karyorrhexis, especially in young women presenting with cervical lymphadenopathy.

Notes: The structural features of turbulence at the free surface of a channel flow have been experimentally investigated. The experiments were conducted in a horizontal channel of large aspect ratio in the (depth based) Reynolds number range of 2800–8800. The results indicate that the persistent structures on the free surface can be classified as upwellings, downdrafts, and spiral eddies. Upwellings are shown to be related to the bursts originating in the sheared region at the channel bottom and the eddies are seen to be generated at the edges of the upwellings. The eddies often merge if rotating in the same direction, and form "pairs" if rotating in opposite directions—though there are occasional mergers of such counter-rotating ones. The spiral eddies decay slowly and are sometimes annihilated by fresh upwellings. The population densities and the persistence times of the various structures were measured for different flow conditions. The resulting data show that the physical parameters characterizing the structures at the interface, scale with a mix of inner (wall shear stress and viscosity) and outer variables. Measurement of the streamwise and spanwise velocities at the free-surface were made by particle imaging velocimetry (PIV) and the surface normal velocity near the free-surface estimated by continuity. The results indicate that the upwellings and spiral eddy regions would be expected to dominate scalar transport rates at high Prandtl/Schmidt numbers. The one-dimensional energy spectra of the flow field at the free-surface compare well with direct numerical simulations and show a region with −5/3 slope at low wave numbers. This experimentally confirms a previous result regarding the two-dimensionality of turbulence near the free surface, based on numerical simulations by Pan and Banerjee [Phys. Fluids 7, 1649 (1995)]. © 1998 American Institute of Physics.

Notes: A method for particle image velocimetry (PIV) is presented which improves upon the accuracy, computational efficiency and dynamic range (i.e., the difference between the largest and smallest resolvable particle displacement vectors) of conventional PIV techniques. The technique is applied to free-surface turbulence to resolve energy spectra for motions with a wide dynamic range. The methodology—based on multi-grid image processing algorithms for rigid body motion analysis, estimates the displacement vectors at discrete particle locations. The essence of this technique is to estimate large scale motions from image intensity patterns of low spatial frequencies and small scale motions from intensity patterns of high spatial frequencies. Cross-correlation between a pair of time separated particle images is implemented by the hierarchical computational scheme of Burt ["Fast filter transforms for image processing," Int. J. Comput. Vision 16, 20 (1981)]. Each image is convolved with a series of band-pass filters and subsampled to obtain a set of images progressively decreasing in resolution and size. A coarse estimate of the displacement field obtained from pairs of lower resolution images are used to obtain more accurate estimates at the next (finer) level. Processing starts at the level of lowest resolution and stops at the highest resolution level, which contains the original image pair. Due to subsampling of low resolution images, the match template size can be kept constant for all stages of computation, thus eliminating the dependence of the largest resolvable displacement on the size of match template. In the present work, the search area at each level is kept constant at 3×3 pixels and the match template size at 5×5 pixels for all levels of computation. The algorithm has been implemented using simple thresholding based on the confidence level of an estimated displacement vector, as suggested by Anandan ["A computational framework and an algorithm for measurement of visual motion," Int. J. Comput. Vision, 2, 283, (1987)]. However, the confidence-level-based smoothing technique for rigid body motions (continuous velocity fields) could not be applied to displacement estimates obtained at discrete points i.e., the particle locations. Instead, smoothing was performed over the area covered by each particle. The algorithm has been tested against direct numerical simulations of turbulent flows when the flow field is known and particle images have been generated from these with the addition of noise. Both the accuracy of motion estimation and the computation time are seen to improve as compared to conventional PIV methods. Finally, video images taken of particle motion on the free-surface of a channel flow have been used to determine the capabilities of the technique in an experimental study. The resulting spectra show a quasi-two-dimensional character of the free-surface turbulent flow field, which corresponds well with the direct numerical simulations. © 1998 American Institute of Physics.

Notes: Testicular Leydig cell tumours are rare. Although most behave benignly ≈ 10% are malignant. Clinicopathological features have been described which have some value in predicting malignant behaviour, although as with other endocrine tumours uncertainties remain in many individual cases. Our aim was to determine the clinicopathological features of 20 testicular Leydig cell tumours. We wished to investigate whether, in addition to established clinicopathological features, the MIB1 index and/or flow cytometric analysis of nuclear DNA content are of value in predicting malignancy. We also wished to investigate the frequency of p53 protein accumulation in these neoplasms.〈section xml:id="abs1-2"〉〈title type="main"〉Methods and resultsTwenty testicular Leydig cell tumours were studied and the clinical case notes examined. Histological sections were assessed by pathologists involved in the study. Pathological features evaluated included: tumour size, extratesticular extension, nuclear pleomorphism, mitotic activity, necrosis and vascular invasion. Immunohistochemical staining was performed with the anti-p53 monoclonal antibody DO-7 and the cell proliferation marker MIB1. A flow cytometric analysis of nuclear DNA content was also performed. Three tumours behaved in a malignant fashion with the development of metastases. Another had morphological features of malignancy but the patient died a short time after diagnosis from unrelated causes. These four neoplasms were larger than benign tumours, often contained areas of necrosis and sometimes exhibited vascular invasion. They generally exhibited greater nuclear pleomorphism and a higher mitotic rate than benign tumours. Three of the four malignant tumours had a high MIB1 index (20–50%) and the fourth exhibited DNA aneuploidy by flow cytometry. Two malignant tumours showed increased expression of p53 protein, with ≈ 50% of nuclei staining with DO-7. All benign tumours had a low MIB1 index (0–2%) and a diploid DNA profile, except for one case where there was DNA aneuploidy. There was little or no staining of benign tumours with DO-7.〈section xml:id="abs1-3"〉〈title type="main"〉ConclusionsThe study confirms that large size, marked nuclear pleomorphism, high mitotic rate, necrosis and vascular invasion are important factors in predicting malignant behaviour in testicular Leydig cell tumours. Additional prognostic value may be derived from the MIB1 index and flow cytometry. Accumulation of p53 protein, through mutational or other events, may be important in malignant progression in these tumours.

Notes: To study the clinical and histopathological features of sclerosing epithelioid fibrosarcoma, and to define diagnostic criteria for this uncommon soft-tissue tumour.〈section xml:id="abs1-2"〉〈title type="main"〉Methods and resultsStandard histological, immunohistochemical and ultrastructural techniques were applied to five tumours from head and neck, chest wall and groin. Tumours consisted of groups of monomorphic rounded/epithelioid cells surrounded by a prominent collagenous stroma. Tumour cells showed positive vimentin staining but were negative for other markers. They contained prominent rough endoplasmic reticulum and a large Golgi apparatus which in one case was producing collagen secretion granules, an ultrastructural marker for collagen production. Three patients had medium to long-term survival (3–7 years). Of these, one was disease-free for 3 years, and two experienced multiple recurrences: one of the latter died of metastatic disease.〈section xml:id="abs1-3"〉〈title type="main"〉ConclusionCriteria for diagnosing this uncommon tumour include: small to medium cell size, clear or pale cytoplasm, cellular arrangement in cords and strands, dense collagenous stroma; vimentin staining; rough endoplasmic reticulum and a Golgi apparatus producing, in well preserved examples, collagen secretion granules. The paper emphasizes the value of electron microscopy, supporting an appropriate histological picture and immunophenotype, in identifying these relatively low-grade sarcomas.

Notes: Aims: To document the clinical, morphological and immunohistochemical features of two cases of primary mucosal melanoma with osteocartilaginous differentiation.〈section xml:id="abs1-1"〉〈title type="main"〉Materials and methodsTwo cases of mucosal melanoma with cartilage and bone formation are reported, one arising in the vagina of a 79-year-old woman and one in the oral cavity of a 67-year-old man. The vaginal melanoma exhibited only cartilaginous differentiation. The oral cavity mucosal melanoma exhibited both bone and cartilage formation and was remarkable for its multifocality, long history not associated with metastases and its lengthy manifestation of dual morphologies: some of the tumours were typical in situ/invasive melanotic melanomas whilst the others were composed of amelanotic spindle and epithelioid cells with osteocartilaginous tissue. One of the lesions exhibited in situ and invasive melanoma with transition to an osteogenic tumour in places. The patient also developed non-osteogenic malignant melanomas in the nasal cavity and nasopharynx.〈section xml:id="abs1-2"〉〈title type="main"〉ConclusionsMalignant melanomas showing foci of osteocartilaginous differentiation are extremely rare with only 18 cases reported. Primary mucosal malignant melanomas of vagina and oral cavity showing osteocartilaginous differentiation have not previously been documented. Primary vaginal melanoma with cartilaginous differentiation must be distinguished from primary malignant mixed Müllerian tumour whilst malignant change in a pleomorphic adenoma, sarcomatoid carcinoma, osteogenic sarcoma and mesenchymal chondrosarcoma are included in the differential diagnosis of primary oral mucosal melanomas with osteocartilaginous differentiation. In this context, immunohistochemistry using antibodies to cytokeratin, S100 protein and MIC2 is of value.