bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk factors for thrombosis in patients with immune mediated heparin‐induced thrombocytopenia
Authors: Fabris F. , Luzzatto G. , Soini B. , Ramon R. , Scandellari R. , Randi M. L. , Girolami A.
Published: March 2003

Abstract. Fabris F, Luzzatto G, Soini B, Ramon R, Scandellari R, Randi ML, Girolami A (University of Padua Medical School, Padova, Italy). Risk factors for thrombosis in patients with immune mediated heparin‐induced thrombocytopenia. J Intern Med 2002; 252: 149–154.

Background. As reported by major clinical series in the literature, about 2% of patients receiving unfractionated heparin (UFH) develop immune‐mediated (type II) heparin‐induced thrombocytopenia (HIT) that may be complicated in 30–75% of cases by a paradoxical thrombotic syndrome (HITTS), either arterial or venous. HITTS carries relevant rates of mortality and morbidity, amongst which cerebral and/or myocardial infarction and limb amputations. It is unclear as yet why some patients suffer from isolated thrombocytopenia (HIT), whilst others have HITTS. The aim of the present study was to look for clinical and laboratory features related to the occurrence of HITTS.

Patients and methods. We retrospectively analysed the clinical records of 56 patients with proven HIT, as diagnosed on clinical grounds and by in vitro demonstration of immunoglobulin (IgG)/IgM against the PF4/heparin complex. Thirty‐four patients (61%) had HITTS (19 venous thrombosis, seven arterial thrombosis, five arterial and venous thrombosis, two skin necrosis, one diffuse intravascular coagulation), whereas 22 had uncomplicated HIT. Amongst HITTS patients, two had limb amputation, five had recurrent thrombosis and seven died. Amongst HIT patients three died from causes unrelated to HIT.

Results. No significant difference in sex, age, previous exposure to heparin, UFH route of administration or dose, duration of therapy, time of onset of thrombocytopenia and platelet count recovery, nor antiheparin/PF4 antibodies subtype (IgG or IgM) was detected when comparing HIT and HITTS. In contrast, in the HITTS group a higher prevalence of orthopaedic surgery (15 of 34 vs. 2/22; P=0.01), a significantly lower platelet count nadir (43 ± 32 vs. 75 ± 63 × 109/L; P=0.01) and a significantly higher titre of antiheparin/PF4 antibodies, expressed as optical density of enzyme‐linked immunosorbent assay (ELISA); (1989 ± 1024 vs. 1277 ± 858; P=0.009), were observed in comparison with the HIT group. Amongst HITTS patients, the prevalence of venous thrombosis was significantly higher in orthopaedic patients and in those being treated for venous thromboembolism (18/24 vs. 1/9 patients, χ2 8.4, P=0.004), whilst arterial thrombosis (ART) occurred more often in heparin treatment for arterial disease (3/4 vs. 4/29 patients, χ2 4.6, P=0.03).

Conclusions. Orthopaedic surgery, the severity of thrombocytopenia and high antiheparin/PF4 antibodies titre are adverse prognostic or concurrent factors in the development of HITTS.
Sudden cardiac death in 15–35‐year olds in Sweden during 1992–99
Authors: Wisten A. , Forsberg H. , Krantz P. , Messner T.
Published: March 2003

Abstract.  Wisten A, Forsberg H, Krantz P, Messner T (Sunderby Hospital, Luleå; National Board of Forensic Medicine, Lund; Kiruna District Hospital, Kiruna; and Umeå University Hospital, Umeå; Sweden). Sudden cardiac death in persons 15–35‐year old in Sweden, 1992–99. J Intern Med 2002; 252: 529–536.

Objectives.  To study the incidence, pathogenesis and symptoms preceding sudden cardiovascular death amongst 15–35‐year olds without substance abuse in Sweden during 1992–99.

Design.  This was a register study of a national database of forensic medicine, Rattsbase. Clinical details were obtained from forensic, police and medical records and from interviews with family members.

Setting.  The whole nation of Sweden.

Subjects.  Individuals having suffered a sudden cardiac death.

Results.  We found 181 cases of sudden cardiovascular death in a nationwide database, Rattsbase, in 15–35‐year olds, of which 132 (73%) were male and 49 (27%) were female, and a rather stable incidence of 0.93 per 100 000 per year. Preceding symptoms were seen in half of the cases. The most common forensic diagnoses were: no structural abnormality (21.0%), coronary atherosclerosis (17.7%), dilated cardiomyopathy (12.2%), hypertrophic cardiomyopathy (10.5%) and myocarditis (10.5%).

Conclusion.  Sudden cardiovascular death was uncommon in the young, but the incidence was not decreasing. Postmortem diagnoses were often difficult to establish. There was a high frequency of structurally normal hearts. Because premortal cardiac‐related symptoms are relatively common and treatment methods are developing, we should learn to recognize early symptoms of heart disease. To identify individuals at risk, further studies of preceding symptoms, life‐style factors and electrocardiogram (ECG) changes are needed.
Search for occult secondary osteoporosis: impact of identified possible risk factors on bone mineral density
Authors: Deutschmann H. A. , Weger M. , Weger W. , Kotanko P. , Deutschmann M. J. , Skrabal F.
Published: March 2003

Abstract. Deutschmann HA, Weger M, Weger W, Kotanko P, Deutschmann MJ, Skrabal F (Krankenhaus der Barmherzigen Brüder, Marschallgasse, Teaching Hospital of the Karl‐Franzens University Graz, Austria). Search for occult secondary osteoporosis: impact of identified possible risk factors on bone mineral density. J Intern Med 2002; 252: 389–397.

Objectives. To determine whether the use of more elaborate diagnostic tests can identify possible risk factors for secondary osteoporosis and to evaluate the impact of these possible risk factors on the severity of bone disease in the study population.

Design. Cross‐sectional study.

Setting and participants.  We have investigated 377 subjects (285 females, 92 males) with osteoporosis (T‐score less than −2.5 in dual energy X‐ray absorption) or nontraumatic lumbar vertebral fractures; these patients were referred to our hospital, a secondary care centre, for evaluation and treatment of osteoporosis.

Results. Osteoporosis without attributable risk factor was diagnosed in 106 women (37%) and 30 men (33%). In 241 patients (179 women, 62 men) one or more possible risk factors for osteoporosis (in this paper also called subclinical disease) were revealed. The most common were lactose malabsorption, disturbed exocrine pancreatic function and renal tubular disturbances, including renal hypercalciuria, incomplete renal tubular acidosis and mild phosphate diabetes. The number of possible risk factors in the individual patient was significantly related to the severity of osteoporosis as assessed by Z‐scores (Spearman correlation r = −0.43, P < 0.001, n = 172 for females; r = −0.28, P < 0.05, n = 65 for males).

Conclusions. All the identified subclinical diseases would have remained undetected if the currently accepted guidelines for the investigation of patients with osteoporosis were applied. The statistically significant correlation between the number of identified possible risk factors and the severity of bone disease in the individual patient strongly suggests the pathogenetic significance of the identified subclinical diseases. It is yet to be shown, whether specific treatment of these subclinical diseases yields additional improvement of bone mass as compared with standard treatment of osteoporosis.
Telemedicine used for remote prehospital diagnosing in patients suspected of acute myocardial infarction
Authors: Terkelsen C. J. , Nørgaard B. L. , Lassen J. F. , Gerdes J. C. , Ankersen J. P. , Rømer F. , Nielsen T. T. , Andersen H. R.
Published: March 2003

Abstract. Terkelsen CJ, Nørgaard BL, Lassen JF, Gerdes JC, Ankersen JP, Rømer F, Nielsen TT, Andersen HR (Silkeborg Central Hospital, Silkeborg; Skejby University Hospital, Aarhus N; and Falck, Silkeborg; Denmark). Telemedicine used for remote prehospital diagnosing in patients suspected of acute myocardial infarction. J Intern Med 2002; 252: 412–420.

Introduction.  In patients with acute myocardial infarction (AMI), considerable time elapses from symptom onset until initiation of thrombolytic therapy or primary percutaneous coronary intervention. Prehospital diagnosing can reduce time delays, and remote diagnosing using telemedicine may be appropriate in areas and countries where ambulances are not staffed with physicians.

Objectives.  To evaluate whether it was technically feasible for physicians at a remote university hospital to diagnose ST‐segment‐elevation‐AMI (AMISTelev) in patients suspected of AMI, who were transported by ambulances to a local hospital. To determine associated prehospital delays and in‐hospital treatment delays.

Methods.  Patients carried in telemetry equipped ambulances had 12‐lead electrocardiograms (ECGs) acquired as soon as possible. En route to the local hospital the ECGs were transmitted to a remote university hospital, by use of the GSM‐system. The physician on call at the university hospital interviewed the patients, who were provided with cellular phone headsets, and alerted the local hospital if signs of AMISTelev, bundle‐branch‐block‐AMI or malignant arrhythmia were detected. Patients transported by traditional ambulances were included in a prospective control group.

Results.  In 214 (86%) of 250 patients prehospital diagnosing was successful. Geographically related transmission problems were the primary reason for failure. Ninety‐eight per cent of transmitted electrocardiograms and obtained history takings were technically acceptable for diagnostic purposes. Door‐to‐needle times were shorter amongst patients with AMISTelev who were subjected to prehospital diagnosing (n = 13) as compared with patients transported by traditional ambulances (n = 14) (38 vs. 81 min) (P = 0.004).

Conclusions.  It was technically feasible to use telemedicine for remote prehospital diagnosing of patients suspected of AMI. Patients subjected to prehospital diagnosing had shorter door‐to‐needle times compared with a prospective control group.
Atomic force microscopy of histological sections using a new electron beam etching method
Authors: Osada  , Arakawa  , Ichikawa  , Ikai
Published: March 2003

In order to examine histological sections of the rat vomeronasal epithelium with the atomic force microscope (AFM), we developed an electron beam etching method that improves the resolution of AFM images. This method results in AFM images comparable to those obtained with the transmission electron microscope (TEM). Ultrathin tissue sections embedded in epoxy resin were observed before and after the treatment with electron beam radiation. Before electron beam treatment, epithelial structures such as the microvilli surface, dendritic processes, the supporting cell layers and the neuronal cell layers were all visible using the AFM. However, only a few subcellular structures could also be resolved. The AFM images were not as clear as those obtained with the TEM. After electron beam treatment, however, the resolution of AFM images was greatly improved. Most of the subcellular structures observed in TEM images, including the inner membrane of mitochondria, ciliary‐structure precursor body, junctional complexes between the neurons and supporting cells, and individual microvilli were now visible in the AFM images. The electron beam treatment appeared to melt the embedding resin, bringing subcellular structures into high relief. The result of this study suggests that electron beam etching of histological samples may provide a new method for the study of subcellular structure using the AFM.
A comparative study of thin coatings of Au/Pd, Pt and Cr produced by magnetron sputtering for FE‐SEM
Authors: Stokroos  , Kalicharan  , Van Der Want  , Jongebloed
Published: March 2003

Visualization of structural details of specimens in field emission scanning electron microscopy (FE‐SEM) requires optimal conductivity. This paper reports on the differences in conductive layers of Au/Pd, Pt and Cr, with a thickness of 1.5–3.0 nm, deposited by planar magnetron sputtering devices. The coating units were used under standard conditions for source–substrate distance, current, HT and argon pressure. Carbon films, deposited by high‐vacuum evaporation on small, freshly cleaved pieces of mica, were used as substrate and mounted on copper grids for TEM and SEM inspection. Au/Pd, Pt and, to a lesser extent, Cr coatings varied in particle density, size and shape. Au/Pd coatings have a slightly more granular appearance than Cr and Pt coatings, but this is strongly dependent on the type of sputtering device employed. In FE‐SEM images there is almost no difference in contrast and particle size between the Au/Pd layer and the Pt layers of a similar thickness. The nuclei of Au/Pd are rather small with almost no growth to the sides or in height, making Au/Pd coatings a good alternative to chromium and platinum for FE‐SEM of biological tissues because of its higher yield of secondary electrons.
Time‐gated fluorescence lifetime imaging and microvolume spectroscopy using two‐photon excitation
Authors: Sytsma  , Vroom  , De Grauw  , Gerritsen
Published: March 2003

A scanning microscope utilizing two‐photon excitation in combination with fluorescence lifetime contrast is presented. The microscope makes use of a tunable femtosecond titanium:sapphire laser enabling the two‐photon excitation of a broad range of fluorescent molecules, including UV probes. Importantly, the penetration depth of the two‐photon exciting (infra)red light is substantially greater than for the corresponding single‐photon wavelength while photobleaching is significantly reduced.

The time structure of the Ti:Sa laser can be employed in a straightforward way for the realization of fluorescence lifetime imaging. The fluorescence lifetime is sensitive to the local environment of the fluorescent molecule. This behaviour can be used for example to quantify concentrations of ions, such as pH and Ca2+, or pO2 and pCO2. In the set‐up presented here the fluorescence lifetime imaging is accomplished by time‐gated single photon counting.

The performance and optical properties of the microscope are investigated by a number of test measurements on fluorescent test beads. Point‐spread functions calculated from measurements on 230‐nm beads using an iterative restoration procedure compare well with theoretical expectations.

Lifetime imaging experiments on a test target containing two different types of test bead in a fluorescent buffer all with different lifetimes (2.15 ns, 2.56 ns and 3.34 ns) show excellent quantitative agreement with reference values obtained from time correlated single photon counting measurements. Moreover, the standard deviation in the results can be wholly ascribed to the photon statistics.

Measurements of acridine orange stained biofilms are presented as an example of the potential of two‐photon excitation combined with fluorescence lifetime contrast. Fluorescence lifetime and intensity images were recorded over the whole sample depth of 100 μm. Fluorescence intensity imaging is seriously hampered by the rapid decrease of the fluorescence signal as a function of the depth into the sample. Fluorescence lifetime imaging on the other hand is not affected by the decrease of the fluorescence intensity.
Simultaneous confocal lifetime imaging of multiple fluorophores using the intensity‐modulated multiple‐wavelength scanning (IMS) technique
Authors: Carlsson  , Liljeborg
Published: March 2003

We demonstrate the simultaneous recording of confocal lifetime images of multiple fluorophores. The confocal microscope used in the study combines intensity‐modulated laser illumination, lock‐in detection and spectral separation of the fluorescent light. A theoretical investigation is presented that describes how the signal‐to‐noise ratio (SNR) depends on various factors such as modulation frequency, degree of modulation and number of detected photons. Theory predicts that, compared with ordinary intensity images, lifetime images will have a SNR that is, at best, approximately four times lower. Experimental results are presented that confirm this prediction.
Continuous wave excitation two‐photon fluorescence microscopy exemplified with the 647‐nm ArKr laser line
Authors: Booth  , Hell
Published: March 2003

We report on efficient two‐photon fluorescence imaging in beam scanning microscopy by exciting UV dyes at the 647‐nm line of a continuous wave ArKr mixed gas laser. For a numerical aperture of 1.4 (oil), we used an illumination power of up to 210 mW at the sample. High‐resolution images were obtained for DAPI‐labelled cell nuclei within 4–60 s. Our method is a simple two‐photon alternative to UV confocal imaging with the potential of becoming a very useful feature of laser scanning microscopy.
Real‐time three‐dimensional imaging of macroscopic structures
Authors: Wilson  , Neil  , Juškaitis
Published: March 2003

We describe an extremely simple method of obtaining optically sectioned images with conventional low‐power imaging systems in real time. A single spatial frequency grid pattern is projected onto an object. Images taken at three spatial positions of the grid projection are processed to provide 3D images of macroscopic structures.
Three‐dimensional diffusion measurements by scanning microphotolysis
Authors: Kubitscheck  , Wedekind  , Peters
Published: March 2003

Fluorescence microphotolysis techniques have been used widely to measure lateral diffusion in two‐dimensional microsystems such as cell membranes. However, a general microphotolysis method for the analysis of truly three‐dimensional diffusion processes has not been developed so far. Here we combine microphotolysis with confocal laser scanning microscopy and numerical data evaluation in such a manner that small volumes (≥ 0.5 μm3) can be photolysed within extended three‐dimensional samples and that fluorescence changes can be monitored at high time resolution (measuring interval  0.5 ms) and evaluated for lateral diffusion coefficients. We show furthermore that diffusion measurements can be performed according to three different experimental modes: (i) the instantaneous mode, (ii) the continuous mode and (iii) the mixed mode. For the evaluation of experimental data in terms of diffusion coefficients we have developed and thoroughly characterized a theoretical framework which is based on the numerical simulation of appropriate reaction–diffusion systems. The theoretical framework is rather general and flexible and can be applied to any microphotolysis geometry, makes provision for photolysis during fluorescence monitoring and takes into account the convolution of concentration distributions with imaging point spread functions. The new method was tested employing simple well‐defined model systems.
Accurate structure determination from image reconstruction in ADF STEM
Authors: Nellist P. D. , Pennycook S. J.
Published: March 2003

Annular dark‐field (ADF) imaging in a scanning transmission electron microscope results in direct structure images of the atomic configuration of the specimen. Since such images are almost perfectly incoherent they can be treated as a convolution between a point‐spread function, which is simply the intensity of the illuminating electron probe, and a sharply peaked object function that represents the projected structure of the specimen. Knowledge of the object function for an image region of perfect crystal allows the point‐spread function to be directly determined for that image. We examine how the object function for an image can then be reconstructed using a Wiener filter, the CLEAN algorithm and a maximum entropy reconstruction. Prior information is required to perform a reconstruction, and we discuss what nature of prior information is suitable for ADF imaging.
Real‐time imaging of two‐photon‐induced fluorescence with a microlens‐array scanner and a regenerative amplifier
Authors: Fujita K. , Nakamura O. , Kaneko T. , Kawata S. , Oyamada M. , Takamatsu T.
Published: March 2003

A real‐time two‐photon fluorescence microscope with a microlens‐array scanner using a regenerative amplifier is presented. The regenerative amplifier generates pulsed laser lights with extremely high peak power and produces brighter two‐photon‐induced fluorescence compared with that produced without the amplifier. Experimental results obtained from the observation of some biological samples with the proposed microscope are given.
Magnetic domain imaging with a scanning near‐field optical microscope using a modified Sagnac interferometer
Authors: Bauer A. , Petersen B. L. , Crecelius T. , Meyer G. , Wegner D. , Kaindl G.
Published: March 2003

We report on the combination of a scanning near‐field optical microscope and a modified Sagnac interferometer for magnetic‐domain imaging in the reflection mode. The Sagnac interferometer is used for detection of the magneto‐optical Kerr effect. Since the interferometer is inherently insensitive to polarization changes caused by topography effects, magnetic‐domain imaging is not limited to samples with flat surfaces. In this way, it is possible to image magnetic bits written on the tracks of a magneto‐optical disc that has a rather pronounced surface profile.
Evanescent field excitation and measurement of dye fluorescence in a metallic probe near‐field scanning optical microscope
Authors: Hayazawa N. , Inouye Y. , Kawata S.
Published: March 2003

We introduce a method of dye fluorescence excitation and measurement that utilizes a near‐field scanning optical microscope (NSOM). This NSOM uses an apertureless metallic probe, and an optical system that contains a high numerical aperture (NA) objective lens (NA = 1.4). When the area which satisfies NA < 1 is masked, the objective lens allows for the rejection of possible transmitted light (NA < 1) through the sample. In such conditions, the focused spot consists of only the evanescent field. We found that this NSOM system strongly reduces the background of the dye fluorescence and allows for the measurement of the fluorescence intensity below the diffraction limit of the excitation source.
Freeze‐substitution of rabbit tibial articular cartilage reveals that radial zone collagen fibres are tubules
Authors: Ap Gwynn  , Wade  , Kääb  , Owen  , Richards
Published: March 2003

Investigations of the micromorphology of rabbit tibial articular cartilage using scanning and transmission electron microscopy revealed that the collagenous elements in the tissue form fluid‐containing tubular structures. The commonly described radial or deep zone longitudinal fibres were found to be tubular structures with internal diameters of 1–2 μm. The walls of the tubules were composed of tightly packed fibrils of collagen. The tangential zone, close to the tibial plateau, was composed mainly of a spongy arrangement of collagen fibrils, containing bunches of tangentially lying small (< 1 μm) diameter tubules. The application of conventional chemical fixation techniques resulted in the fine detail of this tissue being obscured. When the tissue was frozen, followed by cryo‐scanning electron microscopy or freeze‐drying, prior to observation in the scanning electron microscope the tubule structures were not obviously present. It was only by applying freeze‐substitution techniques, followed by critical point drying or resin embedding, that the structure was revealed clearly. Segregation of water into ice crystals did occur during the freezing process, but the formation of those crystals played no part in creating the tubular morphology observed. A similar structure was still revealed following pre‐treatment with glycerol, methanol or Triton X‐100, provided that concentration of these additives was not too high. The walls of the tubules in the radial region were composed of straight, longitudinally arranged as well as helically arranged, 30 nm diameter fibrils. The lumen of the tubules appears to be lined by a circumferentially arranged array of approximately 10 nm diameter fibres, spaced at regular intervals of 50–70 nm.
Interfacial reaction and its influence on the mechanical properties of the ASZ short fibre‐reinforced Al alloy composite
Authors: Lee J.‐C. , Shim J.‐H. , Seok H.‐K. , Lee H.‐I.
Published: March 2003

The effect of interfacial reaction on the mechanical properties of the AC8A Al alloy reinforced with ASZ short fibres (ASZ/AC8A composite) was studied. In the ASZ/AC8A composite, the interfacial reaction was observed to proceed between the SiO2 binder layer and Mg of the matrix to form MgAl2O4 at the interface. Formation of MgAl2O4 was believed to enhance the interfacial bonding strength, resulting in the improved composite strength. However, the interfacial reaction in the ASZ/AC8A composite always took place at the expense of Mg in the matrix, resulting in the composite devoid of the Mg bearing precipitates such as Al2CuMg and Mg2Si. Interfacial reaction mechanisms were investigated for composites containing various Mg contents. The resultant mechanical properties of the composite were measured to determine the adequate amount of Mg within the composite. Microstructural changes of the composite were observed using transmission electron microscopy and differential scanning calorimetry to provide qualitative analyses on the experimental observations.
Subsurface nanoindentation deformation of Cu–Al multilayers mapped in 3D by focused ion beam microscopy
Authors: Inkson B. J. , Steer T. , Möbus G. , Wagner T.
Published: March 2003

A new technique for the three‐dimensional analysis of subsurface damage of nanocomposites is presented. Cu–Al multilayers, grown epitaxially on (0001)Al2O3 single crystals by ultra high vacuum molecular beam epitaxy, have been deformed by nanoindentation. Systematic slicing and imaging of the deformed region by focused ion beam microscopy enables a 3D data set of the damaged region to be collected. From this 3D data set, profiles of the deformed sub‐surface interfaces can be extracted. This enables the deformation of the individual layers, substrate and overall film thickness to be determined around the damage site. These 3D deformation maps have exciting implications for the analysis of mechanical deformation of nanocomposites on a sub‐micrometre scale.
Novel MMC microstructure with tailored distribution of the reinforcing phase
Authors: Peng H. X. , Fan Z. , Evans J. R. G.
Published: March 2003

Saffil short fibre agglomerates with diameters of 0.4 mm to 1 mm have been prepared using a tumbling technique. These were packed and infiltrated with molten 6061 Al alloy to make a metal matrix composite (MMC) with a novel microstructure in which the composite spheres are randomly distributed in the fibre‐free aluminium matrix. In parallel, a commercial preform made of identical Saffil alumina short fibres and having the same fibre volume faction was used to prepare a conventional MMC by the same technique. Microstructural observation indicates that, within the composite spheres, the local volume fraction of fibre decreases from the outer layer to the centre region.

The energy absorption during fracture was estimated by using a three point loading test on notched samples and was compared with that for conventional MMCs. Preliminary results suggest that this novel MMC possesses higher energy absorption capability and hence better damage tolerance. The fracture surfaces were examined by scanning electron microscopy in order to inform these experimental results.
Transmission electron microscopy studies of squeeze cast Al–AlN composites
Authors: Chédru M. , Vicens J. , Chermant J. L. , Mordike B. L.
Published: March 2003

Aluminium‐matrix composites containing ∼45 vol.% AlN particles were fabricated by melt infiltration of aluminium into an AlN preform under a pressure up to 130 MPa. Three types of aluminium alloy (2024, 6060 and 5754) were used. The as‐prepared composites were studied by light microscopy, scanning and transmission electron microscopies, and energy‐dispersive X‐ray spectroscopy. As a result of the melt infiltration process, the composites are very dense and the microstructure shows a homogeneous distribution of the reinforcement. The interfaces are clean with very little porosity. Composites with 2024 and 6060 matrices were carefully studied by transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) after heat treatments. Dislocation density in the matrix of the reinforced material increases due to the difference in thermal expansion coefficients of aluminium alloys and AlN. This can induce an accelerated ageing response of the coherent and semicoherent precipitations of age‐hardened matrices. This behaviour has been studied in the 2024 and 6060 composites by using microhardness measurements and TEM. Reactions between the AlN reinforcement and aluminium matrices (6060 and 5754) were observed and analysed by TEM. Matrices containing some of magnesium display a MgAl2O4 spinel formation at the AlN/matrix interface. The spinel formation is probably due to the reaction between magnesium of the matrix and the thin Al2O3 layer on the AlN surfaces. This reaction can affect the mechanical behaviour of the composite infiltrated with the 5754 matrix. This has been confirmed by overageing some samples at high temperatures (300 °C and 550 °C) for 10 days in order to emphasize the interfacial reactions.
Near‐field effects in single molecule emission
Authors: Gersen H. , García‐Parajó M. F. , Novotny L. , Veerman J. A. , Kuipers L. , Van Hulst N. F.
Published: March 2003

We present the first experimental proof of the influence of a nearby nano‐sized metal object on the angular photon emission by a single molecule. A novel angular sensitive detection scheme is implemented in an existing near‐field scanning optical microscope (NSOM). The positioning accuracy (∼1 nm) of the NSOM allows a systematic investigation of the intensity ratio between two different half‐spaces as a function of the position of the metal–glass interfaces of the probe with respect to the single emitter. The observed effects are shown to be particularly strong for molecules that are excited mainly below the rims of the aperture. An excellent agreement is found between experiments and numerical simulations for these molecules. The observed angular redistribution of the angular emission of a single molecule could explain the alteration of the emission polarization observed for certain molecules in earlier experiments (Veerman et al.(1999)J. Microsc.194, 477–482).
Near‐field mapping of surface polariton fields
Authors: Bozhevolnyi S. I.
Published: March 2003

Using the general approach to image formation in collection near‐field optical microscopy, I derive the symmetry relations for the amplitude coupling coefficients in the case of a weakly guiding single‐mode fibre terminated with a probe tip possessing axial symmetry. It is shown that, for the symmetrical detection configuration, six elements of the coupling matrix can be expressed by using only three independent coupling coefficients. The obtained relations are further applied to describe near‐field mapping of surface plasmon polariton (SPP) fields. I demonstrate that, for the symmetrical detection configuration, the near‐field optical image reflects the intensity distribution of the SPP field components parallel to the surface plane, even though the strong perpendicular component is also being detected. This conclusion is supported with numerical simulations that elucidate the influence of symmetry of the fibre probe on the resulting near‐field optical image. The near‐field optical images simulated for scattering systems typical for SPP microoptics and localization are presented. It is found that the presence of asymmetry in the detection configuration increases the contribution of the perpendicular field component and results in the images approaching the corresponding SPP intensity distributions.
Autocorrelation spectroscopy on single ultrathin layers of CdSe/ZnSe: hints for a non‐thermal distribution of excitons in quantum islands
Authors: Von Freymann G. , Kurtz E. , Klingshirn C. , Litvinov D. , Gerthsen D. , Schimmel T. H. , Wegener M.
Published: March 2003

Autocorrelation spectroscopy on the basis of thousands of individual near‐field photoluminescence spectra of single ultrathin CdSe layers at low temperatures exhibits a strong positive correlation peak around 18 meV energy with a width of 5 meV. Using simulations and experiments as a function of temperature and laser intensity, we can exclude interpretations along the lines of biexcitons or phonon sidebands. We attribute this feature to the splitting of ground state and an excited state in individual quantum islands. This interpretation implies that the potential minima are rather uniform in size and that the distribution of excitons is nonthermal.
Non‐optically probing near‐field microscopy with illumination of total internal reflection
Authors: Kitano H. , Murakami M. , Kawata Y. , Egami C. , Sugihara O. , Okamoto N. , Tsuchimori M. , Watanabe O.
Published: March 2003

We have developed a non‐optically probing near‐field microscope with illumination of total internal reflection. Because the illumination light does not pass through the specimens, it is possible to observe thick specimens or highly absorptive materials. It reduces the background noise because the decay length of the evanescent wave is a few hundred nanometres. We found that although in the total internal reflection illumination system the light passed through the photosensitive film and illuminated the specimen, it did not affect the photosensitive film severely and did not limit the resolution. The imaging properties of reflection illumination and transmission illumination are analysed using a finite‐differential time domain method.
Stereological estimation of eye volume using the Pappus method
Authors: Reed M. G. , Shanks E. , Beech D. J. , Barlow L. , Howard C. V.
Published: March 2003

The estimation of object volume from rotationally randomised sections relies on an ancient geometrical principle due to the Alexandrian mathematician Pappus. In this paper we describe two studies that make estimates of eye volume using a stereological version of the Pappus principle. The first study uses a design‐based version of the Pappus theorem to make estimates of eye volume in Sprague–Dawley rats and the second uses a model‐based implementation for estimating eye volume in juvenile Dover sole. In the sole study we compare the estimates of volume with estimates made using the Cavalieri method and show that the Pappus method gives identical volume estimates with a markedly lower coefficient of variation (2.5%) than the Cavalieri method (13.5%).
High‐resolution electron microscope observation of interface microstructure of a cast Al‐Mg‐Si‐Bi‐Pb(6262)/Al2O3p composite
Authors: Zhou Z. , Fan Z. , Peng H. X. , Li D. X.
Published: March 2003

High‐resolution electron microscopy was employed to characterize the interface structure of a cast Al‐Mg‐Si‐Bi‐Pb aluminium(6262)‐based composite reinforced by α alumina particles with a trace of β alumina in order to investigate the behaviour of alloying elements in cast composites. Except for a few primary Mg2Si particles, few reaction products were detected at the interface of Al/α‐Al2O3 due to the unfavourable reaction kinetics during the squeeze‐casting process. The Mg2Si particle has an orientation relationship with α‐Al2O3 of [011]Mg2Si//[1210]α‐Al2O3 (111)Mg2Si//(0006)α‐Al2O3. A significant amount of MgAl2O4 was found on the surface of the β‐Al2O3 particles, which is in contrast to the small degree of reaction found on α‐Al2O3 particles. MgAl2O4 and β‐Al2O3 particles have the following orientation relationship: [011]MgAl2O4//[1210]β‐Al2O3 (111) MgAl2O4//(0006)β‐Al2O3. The similar crystal structure of β‐Al2O3 to MgAl2O4 favours MgAl2O4 nucleation and growth on the surface of β‐Al2O3. Interfacial energy minimization dominates the atomic structure of the interface with the result that close packed planes and directions in the Al2O3 reinforcement and reaction products are parallel to the interfaces. Bi and Pb were found in the form of metallic nanometre particles between Al2O3 particles, or between the MgAl2O4 and Al2O3 particles, or in the open channels of β‐Al2O3 filled by the Al matrix.
Experimental statistics of near‐field intensity distributions at nanostructured surfaces
Authors: Coello V. , Bozhevolnyi S. I.
Published: March 2003

Scanning near‐field optical microscopy is a technique in which the resolution is primarily determined by the size of a probe and not by the wavelength of illumination as in classical (far‐field) microscopy. However, the relationship between a sample and its near‐field optical image is usually rather complex. Typical factors responsible, at least partially, for such a complexity are the conditions of illumination and detection, sample characteristics (e.g. roughness and dielectric constant) and optical properties of the probe. Theoretical and experimental works conducted to improve our understanding of the relation between the object and the image have been reported (Greffet & Carminati, 1997). Recently, with the help of a photon scanning tunnelling microscope we have carried out an extensive study of the resultant near‐field intensity distributions due to the elastic (in the plane) scattering of surface plasmon polaritons (SPPs) at metal film surfaces. We have also directly observed (in similar experimental conditions) localized dipolar excitations in silver colloid fractals (Bozhevolnyi et al., 1998). In both cases, the studied phenomena are intimately related to the regime of multiple light scattering, in which the interference effects are rather complicated and therefore a proper interpretation of them was far from being trivial. Thus, even though a certain understanding of many features inherent to the subwavelength light interference phenomena was gained (Bozhevolnyi & Coello, 1998; Bozhevolnyi et al., 1998; Coello & Bozhevolnyi, 1999), it is clear from the outcome of the investigations that more systematic studies in this context are still needed. A different and more powerful approach may be a statistical study of the recorded near‐field intensity distributions. In this work, we report what we believe to be the first results on experimental statistics of near‐field optical images exhibiting localized optical excitations (related to the regime of multiple scattering of light). We investigated optical images obtained with SPPs excited at different light wavelengths and scattered at different film surfaces, and with different polarizations and wavelengths of light scattered by silver colloid fractal structures. We have found significant differences in statistics between near‐field intensity distributions taken at rough and smooth metal film surfaces and fractal structures. Finally, our predictions seem to be in agreement with theoretical studies reported by other authors (Sanchez‐Gil & Garcia‐Ramos, 1998).
Well‐shaped fibre tips by pulling with a foil heater
Authors: Gallacchi R. , Kölsch S. , Kneppe H. , Meixner A. J.
Published: March 2003

The length of the molten zone determines the length of pulled optical fibre tips. Tips produced by laser or filament heating are rather lengthy. By using a foil heater the taper length can be shortened and cone angles in the order of 30° can reproducibly be obtained. For varying the drawing force there is an optimum temperature range where the taper shape is monotonic for the whole tip. The tip end diameter is well below 100 nm for optimized pulling conditions.
Photoconductive imaging in a photon scanning tunnelling microscope capable of point‐contact current sensing using a conductive fibre probe
Authors: Iwata F. , Someya D. , Sakaguchi H. , Igasaki Y. , Kitao M. , Kubo T. , Sasaki A.
Published: March 2003

A photoconductive photon scanning tunnelling microscope was developed to investigate the point‐contact photoconductive properties of condensed matter. In order to detect the current and the optical signal at a local point on a surface, we coated the edge of a bent type fibre probe with indium tin oxide. Thus it was possible to measure both photocurrent and optical property with subwavelength resolution. The performance of the novel microscope was evaluated by analysing an organic thin film of copper phthalocyanine (CuPc), which is known to be an efficient photoconductive material. Photocurrent and current–voltage characteristics were observed at the local point on the CuPc thin films. Furthermore, photoconductive images were obtained with topography and near‐field optical imaging using this system. The photoconductive PSTM shows potential in various areas of future optics and electronics.
In situ optical microscopic recording of slip line development during plastic deformation of Cu–15at%Al single crystals with high resolution – estimation of dislocation velocities
Authors: Hoffmann U. , Hampel A. , Neuhäuser H.
Published: March 2003

Observations and measurements of slip line evolution during plastic deformation are performed by optical microscopic video recording. In addition, high resolution in time is achieved by means of photodiodes positioned in the intermediate image plane of the microscope. Examples of measurements at room temperature on short‐range ordered Cu−15at%Al single crystals are given and evaluated to estimate the velocities of edge and screw dislocation groups from the observed rates of growth of slip steps in height and in length, respectively, on one side of the specimen. By means of a second microscope observing the opposite side, the average rates for the dislocations to cross the whole specimen can be obtained. The measured values are discussed in terms of the movement of correlated dislocation groups in the crystals.
In situ observation of superdislocation motion in pre‐strained Ni3Ge single crystals
Authors: Murakumo T. , Haruta K. , Yoneyama N. , Sato A.
Published: March 2003

Dislocation structures and their effect on the superdislocation motion in Ni3Ge single crystals have been studied by two‐step deformation. In these tests either octahedral or cube slips were induced by prestraining. A difference in the induced dislocation structure is found to cause a notable change in the second deformation step depending on the combination of the stress axes. In order to understand the orientation sensitive hardening, in‐situ deformation experiments have been made on the prestrained specimens in a high voltage electron microscope. Besides observation of the structural change due to dislocation motion, electron irradiation, which decorates antiphase boundary tubes, is utilized to trace the history of the rapid dislocation motion. Based on these observations, the origin of the anomalous strengthening in Ni3Ge is discussed with particular interest in the fine and non‐planar dislocation structures induced by cross slips and dislocation–dislocation interactions.
In situ observations of unusual dislocation mechanisms in the intermetallic alloy Ti3Al
Authors: Legros M. , Caillard D.
Published: March 2003

In situ straining experiments in a transmission electron microscope have been carried out on a Ti3Al intermetallic alloy, with the aim of determining the microscopic mechanisms controlling glide in prism, basal and pyramidal planes. Five different antiphase boundary energies have been measured and compared with the corresponding densities of incorrect first nearest neighbour atoms. The determination of a tension–compression asymmetry in pyramidal slip, and the detailed analysis of the complex microscopic mechanisms involved illustrate the efficiency of in situ experiments to solve complex problems in plasticity. A comparison between the properties of the different slip systems shows that they are controlled by different microscopic mechanisms, none of them being of covalent origin.
Improved spatial discrimination of protein reaction states in cells by global analysis and deconvolution of fluorescence lifetime imaging microscopy data
Authors: Verveer P. J. , Squire A. , Bastiaens P. I. H.
Published: March 2003

The deconvolution of fluorescence lifetime imaging microscopy (FLIM) data that were processed with global analysis techniques is described. Global analysis of FLIM data enables the determination of relative numbers of molecules in different protein reaction states on a pixel‐by‐pixel basis in cells. The three‐dimensional fluorescence distributions of each protein state can then be calculated and deconvolved. High‐resolution maps of the relative concentrations of each state are then obtained from the deconvolved images. We applied these techniques to quantitatively image the phosphorylation state of ErbB1 receptors tagged with green fluorescent protein in MCF7 cells.
Cation segregation in Nb16W18O94 using high angle annular dark field scanning transmission electron microscopy and image processing
Authors: Kirkland A. I. , Saxton W. O.
Published: March 2003

We report the characterization of the complex oxide Nb16W18O94 using high angle annular dark field imaging at 200 kV in a scanning transmission electron microscope. The results of this study suggest that the W and Nb cations are not uniformly distributed among the cation columns projected along [001] but that there is preferential segregation of the heavier species to certain column sites. In order to analyse the experimental data obtained, an image processing methodology has been developed which may also find application in locating specific motifs within a generally distorted image field.
Automated reconstruction of curvilinear fibres from 3D datasets acquired by X‐ray microtomography
Authors: Eberhardt C. N. , Clarke A. R.
Published: March 2003

The characterization of fibrous structures is important in both composites and textiles research for relating to the bulk properties of the material. However, the microscopic nature of the fibres and their high densities make them very difficult to characterize. Many techniques have been developed for the measurement and characterization of fibrous structures but they tend to be restricted to measurements on the sample surface or within physical cross‐sections. X‐ray microtomography can be used to non‐destructively probe the internal structure of a range of fibrous materials, providing large amounts of 3D data. A technique has been developed for tracing fibres within 3D datasets acquired by X‐ray microtomography and this has been applied to a glass fibre reinforced composite and also a non‐woven textile sample. The 3D fibrous structures of both samples were successfully reconstructed and their fibre orientation distributions calculated. This technique enables novel characterizations, such as the through‐thickness variation of fibre orientation in non‐wovens.
Improving the quality of electron backscatter diffraction (EBSD) patterns from nanoparticles
Authors: Small J. A. , Michael J. R. , Bright D. S.
Published: March 2003

In this study, we investigated the relative contributions of atomic number (Z) and density (ρ) to the degradation of the electron backscatter diffraction (EBSD) pattern quality for nanoparticles < 500 nm in diameter. This was accomplished by minimizing the diffuse scattering from the conventional thick mounting substrate through the design of a sample holder that can accommodate particles mounted on thin‐film TEM substrates. With this design, the contributions of incoherently scattered electrons that result in the diffuse background are minimized. Qualitative and quantitative comparisons were made of the EBSD pattern quality obtained from Al2O3particles approximately 200 nm in diameter mounted on both thick‐ and thin‐film C substrates. For the quantitative comparison we developed a ‘quality’ factor for EBSD patterns that is based on the ratio of two Hough transforms derived from a given EBSD pattern image. The calculated quality factor is directly proportional to the signal‐to‐noise ratio for the EBSD pattern. In addition to the comparison of the thick and thin mounting substrates, we also estimated the effects of Z and ρ by comparing the EBSD pattern quality from the Al2O3particles mounted on thin‐film substrates with the quality of patterns obtained from Fe–Co nanoparticles approximately 120 nm in diameter.

The results indicate that the increased background generated in EBSD patterns by the electrons escaping through the bottom of the small particles is the dominant reason for the poor EBSD pattern quality from nanoparticles < 500 nm in size. This was supported by the fact that we were able to obtain usable EBSD patterns from Al2O3particles as small as 130 nm using the thin‐film mounting method.