bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary embolism: a follow‐up study of the relation between the degree of right ventricle overload and the extent of perfusion defects
Authors: Ribeiro A. , Lindmarker P. , Johnsson H. , Juhlin‐Dannfelt A. , Jorfeldt L.
Published: March 2003

Abstract.Ribeiro A, Lindmarker P, Johnsson H, Juhlin‐Dannfelt A, Jorfeldt L (Karolinska Hospital, Karolinska Institute, Stockholm, Sweden).Pulmonary embolism: a follow‐up study of the relation between the degree of right ventricle overload and the extent of perfusion defects.J Intern Med1999;245: 601–610.

Objectives.To describe the course of changes in perfusion lung scintigraphy (LS) after acute pulmonary embolism (PE) and test the hypothesis that patients with persistent pulmonary hypertension (PH)/right ventricle (RV) dysfunction after acute PE can be differentiated from those without through larger perfusion defects (PDf) on LS.

Design.Prospective, one‐year follow‐up study with repeated LS and echocardiography‐Doppler investigations.

Setting.Single centre, University Hospital.

Subjects.Patients with clinical suspicion of acute PE with a diagnosis confirmed by LS and/or pulmonary angiography and able to undergo repeated investigations. Of the 78 patients included, a six‐week follow‐up was completed in 67 and a one‐year follow‐up in 64.

Main outcome measures.Time course of PDf in relation to time course of pulmonary artery systolic pressure (PAsP) and RV function.

Results.Initially, PDf decreased exponentially, until the beginning of a stable phase, which was achieved within 54 days for 90% of the patients and within 148 days for all. The temporal relation for the regress of PDf and decrease in PAsP was loose. Patients with persistent PDf suffered PH/RV dysfunction more often than those without. However, the variability in the degree of haemodynamic changes for a given extent of PDf was large.

Conclusions.After acute PE, LS is of use for the identification of the group of patients that may have persistent PH/RV dysfunction. However, since the identification of individual patients is uncertain, LS cannot replace echocardiography‐Doppler in the identification of persistent PH/RV dysfunction after acute PE.
Effects of nicotine nasal spray on atherogenic and thrombogenic factors during smoking cessation
Authors: Lúdvíksdóttir D. , Blöndal T. , Franzon M. , Gudmundsson T. V. , Säwe U.
Published: March 2003

Objectives. To investigate changes in cardiovascular risk factor parameters when stopping smoking and to identify any impact of nicotine nasal spray on these factors.

Design and subjects. In a placebo‐controlled, double‐blind 3‐month prospective study, nicotine nasal spray (NNS) or a placebo was given to 157 subjects attending a smoking cessation programme. Blood samples from 46 subjects who remained abstinent for 3 months were analysed. Nasal spray use was given on an ad libitum basis.

Results. The haemoglobin (Hb) decreased from 149.0 to 143.2 g L–1 (P < 0.001). The haematocrit (Hct) decreased from 44.6 to 42.4% (P < 0.001). The mean corpuscular volume (MCV) decreased from 93.4 to 92.3 fl (P < 0.001). The mean corpuscular haemoglobin concentration (MCHC) increased from 333.9 to 338.1 g L–1 (P = 0.029). The white blood cell count (WBC) decreased from 8.4 to 6.6 × 109 L–1 (P < 0.001). The total cholesterol decreased from 5.92 to 5.65 mmol L–1 (P = 0.015). The high‐density lipoprotein cholesterol (HDL) increased from 1.29 to 1.44 mmol L–1 (P = 0.48) and low‐density lipoprotein cholesterol (LDL) decreased from 4.00 to 3.54 mmol L–1 (P = 0.004). The HDL/LDL ratio increased from 0.36 to 0.46 (P = 0.011).

Conclusion. Stopping smoking resulted in positive effects on cardiovascular risk factors. Nicotine treatment for as long as 3 months did not have any significant effect on these ‘stopping smoking changes’. In smoking cessation, nicotine substitution up to 3 months seems to be safe.
Oestrogen receptors – an overview
Authors: Enmark E. , Gustafsson J.‐Å.
Published: March 2003

Enmark E, Gustafsson J‐A (Karolinska Institutet, Huddinge, Sweden). Oestrogen receptors – an overview (Review). J Intern Med 1999; 246: 133–138.

The oestrogen receptor (ER) is a ligand‐activated transcription factor that mediates the effects of the steroid hormone 17β‐oestradiol in both males and females. Since the isolation and cloning of ER, the prevailing opinion has been that only one such receptor exists. The finding of a second subtype of ER (ERβ) has caused considerable excitement and has forced endocrinologists to re‐evaluate many aspects of the actions of oestrogens. In this article, we will try to summarize the current knowledge about the two oestrogen receptor subtypes, with the emphasis on oestrogen receptor β (ERβ), and to comment on the observations in mice lacking either receptor or the hormone itself.
Heart rate and mortality
Authors: Reunanen A. , Karjalainen J. , Ristola P. , Heliövaara M. , Knekt P. , Aromaa A.
Published: March 2003

Abstract.Reunanen A, Karjalainen J, Ristola P, Heliövaara M, Knekt P, Aromaa A (National Public Health Institute, Helsinki, Central Military Hospital, Helsinki, and Kvaerner Masa‐Yards Helsinki New Shipyard, Helsinki, Finland). Heart rate and mortality.J Intern Med2000;247: 231–239.

Objectives.Increased heart rate has shown to be associated with risk of mortality from cardiovascular diseases in some studies, but not in others. Increased heart rate has also been linked to causes of death other than cardiovascular. To clarify the role of heart rate as a predictor of death we studied its predictive value in a large population study.

Design.A prospective population study with a follow‐up time of 23 years.

Subjects and methods.The study population comprised 5598 men and 5119 women 30–59 years of age on entry. Heart rate was measured from resting ECGs.

Main outcome measure.Mortality from specified causes.

Results.A total of 1848 men and 840 women died during the follow‐up period. Increased heart rate was significantly associated with death from all causes, cardiovascular causes, and natural noncardiovascular, nonmalignant causes of death. Increased heart rate was associated with death from cancer in men with heart disease but not in men without heart disease on entry into the study. The increase in cardiovascular mortality with high heart rate was explained by the close association between heart rate and blood pressure. Adjustment for risk factors did not alter the significance of the association between increased heart rate and mortality from noncardiovascular causes.

Conclusions.High heart rate is simple to observe clinically and a significant if nonspecific predictor of mortality. Increased risk of mortality from cardiovascular diseases can be explained by association with high blood pressure. The increased mortality risk associated with high heart rate related mainly to a group of diseases of noncardiovascular or nonmalignant origin.
Adverse endothelial function and the insulin resistance syndrome
Authors: Tooke J. E. , Hannemann M. M.
Published: March 2003

Abstract. Tooke JE, Hannemann MM (School of Postgraduate Medicine and Vascular Health Sciences, University of Exeter, Devon). Adverse endothelial function and the insulin resistance syndrome (Review). J Intern Med 2000; 247: 425–431.

Type 2 diabetes is characterized by impaired endothelial dependent vasodilatation which may contribute to the high prevalence of vascular disease in such patients. Although hyperglycaemia, dyslipidaemia and hypertension can all independently cause a similar defect, recent data suggest that endothelial dysfunction may be intrinsic to the insulin resistance syndrome that commonly precedes type 2 diabetes. Such abnormalities in endothelial function could represent the impact of subclinical disturbance of metabolism or alternatively the presence of a common cellular defect that influences both nitric oxide bioavailability and insulin mediated glucose disposal. Resolution of this puzzle is likely to lead to important advances in our knowledge and ultimately treatment of vascular disease.
Molecular epidemiology of tuberculosis and other mycobacterial infections: main methodologies and achievements
Authors: Van Soolingen D.
Published: March 2003

Abstract. van Soolingen D (National Institute of Public Health and the Environment, Bilthoven, The Netherlands). Molecular epidemiology of tuberculosis and other mycobacterial infections: main methodologies and achievements (Review). J Intern Med 2001; 249: 1–26.

In the last decade, DNA fingerprint techniques have become available to study the interperson transmission of tuberculosis and other mycobacterial infections. These methods have facilitated epidemiological studies at a population level. In addition, the species identification of rarely encountered mycobacteria has improved significantly. This article describes the state of the art of the main molecular typing methods for Mycobacterium tuberculosis complex and non‐M. tuberculosis complex (atypical) mycobacteria. Important new insights that have been gained through molecular techniques into epidemiological aspects and diagnosis of mycobacterial diseases are highlighted.
Diet and breast cancer
Authors: Willett W. C.
Published: March 2003

Abstract. Willett WC (Harvard Medical School and Brigham and Women’s Hospital, Boston, MA, USA). Diet and Breast Cancer. J Intern Med 2001; 249: 395–411.
The effect of 24 h blood pressure levels on early neurological recovery after stroke
Authors: Bhalla A. , Wolfe C.D.A , Rudd A.G.
Published: March 2003

Abstract. Bhalla A, Wolfe CDA, Rudd AG (Guy’s, King’s and St Thomas’ Hospital, London) J Intern Med 2001; 250: 121–130.

Objectives. To assess the influence of 24 h blood pressure (BP) levels on functional recovery 1 week after stroke and the effect of antihypertensive therapy on 24 h BP levels.

Design. Prospective study of patients admitted to hospital over 1 year with first in a lifetime stroke who underwent 24 h BP and casual measurements. Setting. Medical wards in a teaching hospital.

Subjects. Of 160 patients, 72 patients admitted to hospital within 24 h of stroke onset were investigated. Patients with conditions and therapy that interfered with autonomic and sympathetic function were excluded.

Interventions. All subjects underwent 24 h BP and casual recordings on admission to hospital and at day seven after stroke. The mean 24 h, day and night systolic BP (SBP) and diastolic BP (DBP) and their differences (nocturnal BP dip) were recorded. Patients were divided into three groups according to whether they were taking antihypertensive therapy during the first week: (i) no therapy, (ii) therapy continued after stroke, and (iii) new therapy introduced.

Main outcome measures. Functional recovery (Rankin Scale 0–1) and neurological improvement [Scandinavian Stroke Scale (SSS) ≥3 points] by 1 week of stroke. Change in circadian 24 h BP over 1 week.

Results. For each 10 mmHg difference between day and night time DBP, the odds for making a complete recovery were 4.63 (95% CI: 1.57–13.7, P=0.01). For each 10 mmHg difference between day and night SBP, the odds for making an improvement in neurological status was 2.24 (95% CI: 1.16–4.32; P=0.016). Significant falls in 24 h DBP (P=0.01), daytime SBP (P=0.005) and mean arterial BP (MABP) (P=0.04) over 1 week were demonstrated in patients who had just commenced antihypertensive therapy (P=0.001).

Conclusion. An increase in day to night time BP change is favourable in short‐term outcome after acute stroke. Significant falls in BP are more likely in patients started on antihypertensive therapy for the first time. Further research is required to understand the effects of circadian BP rhythm on stroke outcome.
Chemokines in pathology and medicine
Authors: Baggiolini M.
Published: March 2003

Abstract. Baggiolini M (Theodor Kocher Institute, University of Bern, and Institute for Research in Biomedicine, Bellinzona, Switzerland). Chemokines in pathology and medicine (Review). J Intern Med 2001; 250: 91–104.

About 50 human chemokines and nearly 20 receptors have been identified and characterized in little more than a decade since the discovery of interleukin 8 (IL‐8), the first chemotactic cytokine. Research in this field has dramatically changed our understanding of leucocyte traffic in inflammation and immunity. This paper has been written for scientists and practitioners in the field of medicine. It reviews in concise and intelligible form information that I consider useful for understanding the role of chemokines in human pathophysiology. The main areas covered are: (i) the basics of chemokine structures, mode of action, activities and selectivity; (ii) newer aspects of the broad involvement of chemokines in the regulation of immune defence and the housekeeping of the immune system; (iii) the role of chemokines in pathology as illustrated by animal models and studies of human diseases; and (iv) novel therapeutic approaches for a variety of inflammatory conditions, which are based on modulation of chemokine activity.
Evidence for the regulation of levels of plasma adhesion molecules by proinflammatory cytokines and their soluble receptors in type 1 diabetes
Authors: Mohamed‐Ali V. , Armstrong L. , Clarke D. , Bolton C. H. , Pinkney J. H.
Published: March 2003

Abstract. Mohamed‐Ali V, Armstrong L, Clarke D, Bolton CH, Pinkney JH (University College London Medical School, Whittington Hospital, London; University Department of Medicine, Southmead Hospital, Bristol; and Clinical Sciences Centre, University Hospital Aintree, Liverpool, UK). Evidence for the regulation of levels of plasma adhesion molecules by proinflammatory cytokines and their soluble receptors in type 1 diabetes. J Intern Med 2001; 250: 415–421.

Objectives. To investigate the regulation of soluble adhesion molecules by tumour necrosis factor‐α (TNF‐α) and interleukin‐6 (IL‐6), and relationships with circulating cytokine receptors, in vivo, in type 1 diabetes.

Design. Cross‐sectional study.

Setting. University hospital diabetes clinic.

Subjects. A total of 47 non‐nephropathic, Caucasian type 1 diabetics and 39 nondiabetic controls.

Outcome measures. Plasma levels of TNF‐α, IL‐6, their soluble receptors and adhesion molecules intercellular adhesion molecule‐1 (sICAM‐1), vascular cell adhesion molecule‐1 (sVCAM‐1), sE‐selectin and von Willebrand factor (vWF), and risk factors for cardiovascular disease.

Results. Plasma concentrations of IL‐6 were elevated in diabetic patients compared with controls [median (interquartiles) 1.28 (0.89–2.65) vs. 0.66 (0.45–1.73) pg mL−1: P=0.016], and in these patients IL‐6 and soluble IL‐6 receptor (sIL‐6R) levels correlated with concentrations of sICAM‐1 (r=0.41, P=0.012 and r=0.31, P=0.04, respectively). Tumour necrosis factor‐α soluble receptor‐2 (sTNFRII), but not TNF‐α or tumour necrosis factor soluble receptor‐1 (sTNFRI), was elevated in diabetic subjects (P=0.027). Plasma TNF‐α levels correlated with sVCAM‐1 (r=0.39, P=0.008), triglycerides (r=0.36, P=0.021) and diastolic blood pressure (r=0.35; P=0.024). Both sTNFRI and sTNFRII correlated with blood pressure (r=0.46, P=0.002; r=0.32, P=0.034) and triglycerides (r=0.33, P=0.033; r=0.29, P=0.05). In contrast, HDL‐cholesterol and triglyceride were related to sE‐selectin (r=−0.45 and +0.45; both P < 0.001). Neither sE‐selectin nor vWF were related to cytokine concentrations. Finally, both TNF‐α and sIL‐6R correlated sTNFRI and RII (r=0.44–0.49, P < 0.001). None of these interactions were apparent in control subjects.

Conclusions. (i) IL‐6, through effects on sICAM‐1, and TNF‐α via effects on sVCAM‐1, may promote vascular adhesion; (ii) plasma levels of TNF‐α are associated with dyslipidaemia and increased blood pressure, adding to vascular disease risk; (iii) the actions of both cytokines are probably modified by altered production of soluble receptors in diabetic subjects.
The genetical history of humans and the great apes
Authors: KAESSMANN H. , PÄÄBO S.
Published: March 2003

Abstract. Kaessmann H, Pääbo S (Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany). The genetical history of humans and the great apes. J Intern Med 2002; 251: 1–18.

When and where did modern humans evolve? How did our ancestors spread over the world? Traditionally, answers to questions such as these have been sought in historical, archaeological, and fossil records. However, increasingly genetic data provide information about the evolution of our species. In this review, we focus on the comparison of the variation in the human gene pool to that of our closest evolutionary relatives, the great apes, because this provides a relevant perspective on human genetical evolution. For instance, comparisons to the great apes show that humans are unique in having little genetic variation as well as little genetic structure in their gene pool. Furthermore, genetic data indicate that humans, but not the great apes, have experienced a period of dramatic growth in their early history.
Cardiovascular disease, hypertension and renal function in primary hyperparathyroidism
Authors: Hedbäck G. M. , Odén A. S.
Published: March 2003

Abstract. Hedbäck GM, Odén AS (Sahlgrenska University Hospital, Göteborg University, Göteborg, Sweden). Cardiovascular disease, hypertension, and renal function in primary hyperparathyroidism. J Intern Med 2002; 251: 476–483.

Objectives. Patients with primary hyperparathyroidism run an increased risk of death in cardiovascular disease. Long ago, hypertension was found to frequently occur in these patients. The aim of this study was to compare the death risk after surgery for hyperparathyroidism of hypertensive patients with that of normotensive ones, and to investigate relations between variables of cardiovascular disease and variables of hyperparathyroidism and renal function.

Methods. A series of 845 patients with primary hyperparathyroidism and serum creatinine ≤160 μmol L−1 was followed‐up mean 10.2 (SD 5.7) years after surgery. Survival and correlation tests were performed. Death risk was estimated using a hazard function according to Poisson.

Results. The death risk of hypertensive hyperparathyroid patients was 50% higher compared with that of the normotensive patients, but the yearly death risk decrease after surgery for the hypertensive patients was almost doubled as compared with the decrease of the normotensive patients. Cardiovascular disease was directly related to serum calcium level, adenoma weight, osteitis fibrosa, and serum creatinine, and inversely related to glomerular filtration rate and urine osmolality, but unrelated to the symptom variables. A negative relation was found between cardiovascular disease and renal stone disease.

Conclusions. It can be concluded that cardiovascular disease is more a part of primary hyperparathyroidism than just associated with it, being related to both serum calcium and adenoma weight. There was also a relationship between cardiovascular disease and decreased renal function. Death risk decrease after surgery was rather more pronounced for the hypertensive patients compared with the normotensive ones.
Prevalence and significance of cardiovascular risk factors in a large cohort of patients with familial hypercholesterolaemia
Authors: De Sauvage Nolting P. R. W. , Defesche J. C. , Buirma R. J. A. , Hutten B. A. , Lansberg P. J. , Kastelein J. J. P.
Published: March 2003

Abstract.  de Sauvage Nolting PRW, Defesche JC, Buirma RJA, Hutten BA, Lansberg PJ, Kastelein JJP (Academic Medical Center, Amsterdam; Clinical Research, Haarlem; Slotervaart Hospital, Amsterdam; the Netherlands). Prevalence and significance of cardiovascular risk factors in a large cohort of patients with familial hypercholesterolaemia. J Intern Med 2003; 253: 161–168.

Objective.  Patients with familial hypercholesterolaemia (FH) vary widely in terms of onset of cardiovascular disease (CVD).

Design.  The association between cardiovascular risk factors and prevalent CVD was examined in a cross‐sectional study in order to elucidate their contribution to atherogenesis.

Setting and subjects.  Patients were recruited from 37 Dutch Lipid Clinics. The diagnosis of FH was based on a uniform diagnostic protocol, confirmed by DNA analysis in 62% of the cases. All patients were investigated free from any lipid‐lowering drug for at least 6 weeks.

Main outcome measures.  Differences in lipids, lipoproteins and other risk factors for CVD were analysed in FH patients with and without CVD.

Results.  A total of 526 patients were assessed and more than 37% had a history of CVD with a mean age of onset of 46.8 years. Mean LDL cholesterol (LDL‐C) levels were severely elevated (8.38 ± 2.13 mmol L−1). In univariate analysis, age, presence of hypertension or diabetes, body mass index, triglycerides (TG) and low HDL cholesterol (HDL‐C) were all significantly associated with CVD. Also in multivariate analysis, all these risk factors, except TG and diabetes, were significantly linked to CVD.

Conclusion.  A high CVD risk in this large well‐documented characterized sample of FH patients is not only conferred by elevated LDL‐C but also by low HDL‐C.
Highly efficient upconverters for multiphoton fluorescence microscopy
Authors: Cheng  , Pan  , Shih  , Kim  , Liou  , Park
Published: March 2003

A new generation of efficient two‐photon absorbing fluorescent molecules has been developed and used effectively for two‐photon laser scanning microscopy. Several examples of the use of these new fluorophores have been presented. In addition, issues relating to the two‐photon absorption cross‐section, excitation power, sample properties and resolution in two‐photon laser scanning microscopy are discussed.
Automatic high‐precision measurements of the location and width of Kikuchi bands in electron backscatter diffraction patterns
Authors: Krieger Lassen
Published: March 2003

The demands for reliability and precision of crystal orientation data obtained through automatic analysis of electron backscattering patterns (EBSPs) in the SEM result in similar demands on the quality of the band position data which is provided by an image analysis procedure.

This paper describes a new image processing procedure which is capable of providing accurate measurements of the location and width of typically 10–15 bands in digitized EBSPs of average quality. The new procedure is based on the Hough transform (HT) for line detection, and employs a special backmapping technique for generating two simplified HTs which separately focus on bright and dark lines in the images. A coordinated search for peaks in the two HTs leads to precise estimates of both the position and the width of bands in the patterns.

A visual evaluation of the data produced by the new procedure shows that it performs significantly better than the conventional procedure with regard to both reliability and precision. Additionally, the measured band width data are fairly precise and can be used for obtaining a more robust and reliable indexing of the bands. Finally, the computational costs of the new procedure are smaller than for the conventional procedure.
Heptane and isooctane as embedding fluids for high‐pressure freezing of Petunia ovules followed by freeze‐substitution
Authors: Thijssen  , Van Went  , Van Aelst
Published: March 2003

In comparison with other fixation methods, high‐pressure freezing and freeze‐substitution of Petunia ovules lead to improved ultrastructural preservation of all tissues. Crucial for adequate high‐pressure freezing is the absence of air in the specimen sandwich; air has to be replaced by an embedding fluid. Frequently, 1‐hexadecene is used for this purpose. Using 1‐hexadecene as an embedding fluid resulted in only 5–10% of Petunia ovules being preserved without disturbance of the ultrastructure due to ice‐crystal damage. Since 1‐hexadecene is not soluble in acetone at − 90 °C, freeze‐substitution is hindered when ovules remained completely surrounded by it; this results in recrystallization when the temperature is raised. We tested and compared the suitability of heptane and isooctane as embedding fluids for high‐pressure freezing and freeze‐substitution, reasoning that because of their low melting points and low relative densities, phase separation during freeze‐substitution would result in complete exposure of the ovules to the substitution medium, leading to adequate freeze‐substitution. Using either heptane or isooctane as an embedding fluid yielded up to 90% ice‐crystal‐free ovules. Both compounds, however, have some damaging effects on the outer one or two cell layers of the ovule, but not on the inner tissues.
Assessment of fibre orientation in reinforced concrete using Fourier image transform
Authors: Redon  , Chermant  , Chermant  , Coster
Published: March 2003

In this study, ribbon‐shaped amorphous cast‐iron fibres were used to reinforce a concrete matrix. X‐ray photographs have been taken to detect fibres in situ. Their orientation has been investigated by automatic image analysis methods. However, this measurement should not be influenced by the digitization on the square frame of the analyser. For that purpose, the Fourier transform was used rather than the rose of direction method. This analysis revealed the transverse isotropic nature of the spatial arrangement of these fibres, whose axis of revolution corresponds to the concrete casting axis. Such a morphological characterization of the fibre‐reinforced concrete reveals its mechanical behaviour.
The axonal transmission of Herpes simplex virus to epidermal cells: a novel use of the freeze substitution technique applied to explant cultures retained on cover slips
Authors: Holland D.J. , Cunningham A.L. , Boadle R.A.
Published: March 2003

Retaining the ultrastructural arrangement of a mixed‐cell culture on a solid support while processing for immunocytochemical study is a technical challenge. We developed a technique to study the axonal transport of the Herpes simplex virus from dorsal root ganglia sensory neurones to epidermal cells. Autologous explants of human foetal dorsal root ganglia and skin were cultured on plastic cover slips. Axon fascicles grew from the ganglia to the epidermal cells and the ganglia were inoculated selectively with virus. The whole preparation, retained on the cover slip, was fixed with formaldehyde 4% (freshly prepared from paraformaldehyde)/glutaraldehyde 0.1%, processed by freeze substitution, and embedded in Lowicryl HM20 resin. The edges of the cover slip in the block were trimmed, allowing clean and complete separation from the resin block, which retained the tissue. The resin block was placed in fresh HM20 and repolymerized. The polymerizing resin bonded strongly to the existing block. After trimming, serial sections were easily obtained and successfully immunolabelled for viral proteins. This is a convenient technique for immunolabelling tissue grown on cover slips in which the preservation of the ultrastructural interactions between different cells is important. It should be adaptable to a number of cell‐culture applications and has a number of advantages over other techniques.
Iterative structure retrieval techniques in HREM: a comparative study and a modular program package
Authors: Möbus G. , Schweinfest R. , Gemming T. , Wagner T. , Rühle M.
Published: March 2003

A retrieval technique for crystal structures using high‐resolution electron microscopy is presented. The inversion of the complex structure‐to‐image relation is performed by numerical optimization of the configuration space of object models. Unlike structure refinement in X‐ray crystallography, the method operates on unknown defect structures on a nanometre scale. The diversity of crystal defects examined and the differences in microscope types and alignment conditions makes it necessary to adapt the basic algorithm to a broad variety of needs resulting in a modular program package for general use. New developments, such as a real space slice function calculation, problem adapted optimization strategies, and finally an examination of iterative matching of image series and exit wavefunctions are presented.
Quantitative HREM observation of the Σ11(113)/[1¯10] grain‐boundary structure in aluminium and comparison with atomistic simulation
Authors: King W. E. , Campbell G. H. , Foiles S. M. , Cohen D. , Hanson K. M.
Published: March 2003

Quantitative high‐resolution electron microscopy (QHREM) involves the detailed comparison of experimental high‐resolution images with image simulation based on a model and weighted by the estimated uncertainty in the experimental results. For simple metals, such as Al, models have been systematically improved using nonlinear least‐squares methods to obtain simulated images that are indistinguishable from experimental images within the experimental error. QHREM has been used to study the atomic structure of the Σ11(113)/[1¯10] in Al. In this paper, we focus on the method of refining electron‐optical imaging parameters and atomic structure to bring the simulated HREM image into agreement with the experimental result to within the experimental error and thus yield a result more useful to the materials scientist. Uncertainties in fitted parameters are studied using the conditional probability distribution function. We discuss experimental results for atomic column locations compared with atomistic simulations of the structure of the grain boundary.
Dynamic etching method for fabricating a variety of tip shapes in the optical fibre probe of a scanning near‐field optical microscope
Authors: Muramatsu H. , Homma K. , Chiba N. , Yamamoto N. , Egawa A.
Published: March 2003

A novel etching method for an optical fibre probe of a scanning near‐field optical microscope (SNOM) was developed to fabricate a variety of tip shapes through dynamic movement during etching. By moving the fibre in two‐phase fluids of HF solution and organic solvent, the taper length and angle can be varied according to the movement of the position of the meniscus on the optical fibre. This method produces both long (sharp angle) and short (wide angle) tapered tips compared to tips made with stationary etching processes. A bent‐type probe for a SNOM/AFM was fabricated by applying this technique and its throughput efficiency was examined. A wide‐angle probe with a 50° angle at the tip showed a throughput efficiency of 3.3 × 10−4 at a resolution of 100 nm.
Polarization properties of the near‐field intensity reflected by metallic and dielectric one‐dimensional structures
Authors: Wang S. , Méndez E. R.
Published: March 2003

We investigate the state of polarization and near‐field intensity distribution in the vicinity of rectangular groove objects ruled on metallic and dielectric materials. The sample is illuminated from the vacuum side by a linear combination of p‐ and s‐polarised waves. Two rigorous methods of solution are used and compared in calculations of the total intensity at constant height when the light is incident normally onto the surface. Some calculations of the total intensity in the ‘follow‐the‐profile mode’ are also presented. It is shown that in the constant height mode, the contrast in the image can be reversed as the plane of observation moves away from the mean plane of the sample. We also found that the state of polarization depends strongly on the material and the distance to the plane of detection.
I5M: 3D widefield light microscopy with better than 100 nm axial resolution
Authors: Gustafsson  , Agard  , Sedat
Published: March 2003

Sevenfold improved axial resolution has been achieved in three‐dimensional widefield fluorescence microscopy, using a novel interferometric technique in which the sample is observed and/or illuminated from both sides simultaneously using two opposing objective lenses. Separate interference effects in the excitation light and the emitted light give access to higher resolution axial information about the sample than can be reached by conventional widefield or confocal microscopes. Here we report the experimental verification of this resolution performance on complex biological samples.
Adaptation of a super‐sensitive epitope detection technique for the immunoelectron microscopy of titin filaments in vertebrate striated muscle
Authors: Trombitás  , Pollack  , Greaser
Published: March 2003

A super‐sensitive epitope‐detection technique based on gold–silver intensification was adapted for pre‐embedding immunolabelling of titin filaments in vertebrate striated muscle. Indirect immunoelectron microscopy of titin filaments was performed with monoclonal titin antibodies as primary antibodies and Fab anti‐mouse IgG conjugated with 1.4 nm gold particles as secondary antibodies. The secondary antibodies penetrated easily into the tissue owing to their reduced size and the very small gold particles. After the labelling procedure, the tissue was fixed in glutaraldehyde. Since the gold particles were not visible by conventional transmission electron microscopy, they were intensified with a silver developing system. Although the particle size varied nonlinearly with the developing time, very fine grain size was achievable. The technique provided super‐sensitive detection with excellent contrast and demonstrated epitopes with both strong and weak affinities.
AFM tips: how sharp are they?
Authors: Sheng  , Czajkowsky  , Shao
Published: March 2003

From both simple estimates and a ‘blind’ reconstruction based on cryo‐AFM images of filamentous actin, we find that the radius of curvature at the apex of Si3N4 tips can be as small as 1 nm with a conical angle in the range 30~40°, revealing a relatively high aspect ratio that is much greater than previously anticipated. Our results show that commercially available cantilevers are often sharp enough for routine high resolution imaging of biological materials, and suggest that factors other than an inherent blunt tip are probably responsible for frequent occurrences of poor resolution.
An optical sectioning programmable array microscope implemented with a digital micromirror device
Authors: Hanley  , Verveer  , Gemkow  , Arndt‐Jovin  , Jovin
Published: March 2003

The defining feature of a programmable array microscope (PAM) is the presence of a spatial light modulator in the image plane. A spatial light modulator used singly or as a matched pair for both illumination and detection can be used to generate an optical section. Under most conditions, the basic optical properties of an optically sectioning PAM are similar to those of rotating Nipkow discs. The method of pattern generation, however, is fundamentally different and allows arbitrary illumination patterns to be generated under programmable control, and sectioning strategies to be changed rapidly in response to specific experimental conditions. We report the features of a PAM incorporating a digital micromirror device, including the axial sectioning response to fluorescent thin films and the imaging of biological specimens. Three axial sectioning strategies were compared: line scans, dot lattice scans and pseudo‐random sequence scans. The three strategies varied widely in light throughput, sectioning strength and robustness when used on real biological samples. The axial response to thin fluorescent films demonstrated a consistent decrease in the full width at half maximum (FWHM), accompanied by an increase in offset, as the unit cells defining the patterns grew smaller. Experimental axial response curves represent the sum of the response from a given point of illumination and cross‐talk from neighbouring points. Cross‐talk is minimized in the plane of best focus and when measured together with the single point response produces a decrease in FWHM. In patterns having constant throughput, there appears to be tradeoff between the FWHM and the size of the offset. The PAM was compared to a confocal laser scanning microscope using biological samples. The PAM demonstrated higher signal levels and dynamic range despite a shorter acquisition time. It also revealed more structures in x‐z sections and less intensity drop‐off with scanning depth.
The response of SiC fibres to vacuum plasma spraying and vacuum hot pressing during the fabrication of titanium matrix composites
Authors: Baker  , Grant  , Jenkins
Published: March 2003

Vacuum plasma spraying (VPS) and vacuum hot pressing (VHP) have been used to fabricate Ti‐6Al‐4V matrix composite material reinforced longitudinally with DERA Sigma C coated SiC 1140+ fibres. VPS of Ti‐6Al‐4V onto Sigma 1140+ SiC fibres caused no fibre/matrix interfacial reaction. During VHP a fibre/matrix reaction occurred, producing a mixture of fine (< 50 nm) TiCx(x ≤ 1) adjacent to the fibre coating and coarse‐grained (0.3–0.5 μm) equiaxed TiCxadjacent to the Ti matrix. A decrease in C concentration with increasing distance from the C coating is proposed, and is consistent with the evidence presented. A similar thickness and morphology of reaction product arose from conventional foil–fibre foil processing, but the matrix coated fibre/hot isostatic pressing process led to a slightly thicker reaction layer. The TiCxreaction product acted as a diffusion barrier, inhibiting further reaction more effectively than in experiments on earlier SiC fibres having a C coating.

Surface damage was shown to be a factor in lowering 1140+ SiC fibre failure stress. Surface damage to 1140+ fibres resulted from both VPS and VHP, the former causing a slight reduction in mean ultimate tensile strength (UTS), and a large reduction in the bend strain to failure Weibull modulus. This damage was caused by both fibre winding and by deposition of metal during VPS, giving rise to coating flaws, and is not in itself considered to be a major problem. Surface damage increased after VHP, reducing the mean UTS and tensile Weibull modulus, and the mean bend strain to failure. This damage arose from bending and flattening of the rough monotapes, and from the fibre/matrix reaction caused by thermal exposure. The level of damage to 1140+ SiC fibre from VHP was reduced by modification of the process path. Increasing the VHP temperature and lowering the pressure ramp rate reduced fibre damage sufficiently to enable a macroscopic composite UTS of 95% of the theoretical maximum to be achieved.
Imaging damage evolution in a small particle metal matrix composite
Authors: Evans  , Phaneuf  , Boyd
Published: March 2003

It is difficult to study effectively microstructural damage in metal matrix composites (MMCs) due to artefacts arising from traditional metallographic sample preparation techniques. The sectioning and imaging capabilities of the focused ion beam (FIB) microscope provide an excellent method for studying damage accumulation in MMCs.

The capabilities of the FIB system have been used to carry out a study of damage evolution in a powder‐processed/hot‐extruded Al2080/SiCp MMC. Microvoid damage is found to be preserved accurately during FIB sectioning, allowing measurements of the fraction of decohered particles and the void area fraction. These microscopic damage measurements are correlated with the macroscopic damage parameter, D, as determined by density measurements.

Using transmission electron microscopy, the evolution of dislocation structures at the SiC–matrix interfaces has been examined. A previously unreported decohesion mechanism has been observed.
Minimal compression of ultrathin sections with use of an oscillating diamond knife
Authors: Studer  , Gnaegi
Published: March 2003

With the aim to minimize compression artefacts in ultrathin sections, coincident with the stroke direction, we have invented an oscillating diamond knife. Results and theoretical considerations explaining its function are discussed. During conventional ultrathin sectioning the resultant compression is in the order of 20–35% of section height. This holds true for sections of samples embedded into Lowicryl HM20 and of the polymer polystyrene, cut with a 45° diamond knife and floated on water. The oscillating knife reduces this compression almost completely. It consists of a diamond knife on which a low voltage piezoelectric translator (piezo) is mounted, which oscillates when the piezo is driven by an alternating voltage source. No additional cutting artefacts were observed in the micrographs when they were compared with sections produced without oscillating the knife.
Soft X‐ray spectroscopy from image sequences with sub‐100 nm spatial resolution
Authors: Jacobsen  , Wirick  , Flynn  , Zimba
Published: March 2003

A method is described whereby a sequence of X‐ray images at closely spaced photon energies is acquired using a scanning transmission X‐ray microscope, and aligned. Near‐edge absorption spectra can then be obtained both from large, irregular regions, and from regions as small as the spatial resolution of the microscope (about 40 nm in the examples shown here). The use of the technique is illustrated in examination of a layered polymer film, a micrometeorite section, and an interplanetary dust particle section.
Retrospective shading correction based on entropy minimization
Authors: Likar  , Maintz  , Viergever  , Pernuš
Published: March 2003

Shading is a prominent phenomenon in microscopy, manifesting itself via spurious intensity variations not present in the original scene. The elimination of shading effects is frequently necessary for subsequent image processing tasks, especially if quantitative analysis is the final goal. While most of the shading effects may be minimized by setting up the image acquisition conditions carefully and capturing additional calibration images, object‐dependent shading calls for retrospective correction. In this paper a novel method for retrospective shading correction is proposed. Firstly, the image formation process and the corresponding shading effects are described by a linear image formation model, which consists of an additive and a multiplicative parametric component. Secondly, shading correction is performed by the inverse of the image formation model, whose shading components are estimated retrospectively by minimizing the entropy of the acquired images. A number of tests, performed on artificial and real microscopical images, show that this approach is efficient for a variety of differently structured images and as such may have applications in and beyond the field of microscopical imaging.
The influence of the regularization parameter and the first estimate on the performance of Tikhonov regularized non‐linear image restoration algorithms
Authors: Van Kempen  , Van Vliet
Published: March 2003

This paper reports studies on the influence of the regularization parameter and the first estimate on the performance of iterative image restoration algorithms. We discuss regularization parameter estimation methods that have been developed for the linear Tikhonov–Miller filter to restore images distorted by additive Gaussian noise. We have performed experiments on synthetic data to show that these methods can be used to determine the regularization parameter of non‐linear iterative image restoration algorithms, which we use to restore images contaminated by Poisson noise. We conclude that the generalized cross‐validation method is an efficient method to determine a value of the regularization parameter close to the optimal value. We have also derived a method to estimate the regularization parameter of a Tikhonov regularized version of the Richardson–Lucy algorithm.  These iterative image restoration algorithms need a first estimate to start their iteration. An obvious and frequently used choice for the first estimate is the acquired image. However, the restoration algorithm could be sensitive to the noise present in this image, which may hamper the convergence of the algorithm. We have therefore compared various choices of first estimates and tested the convergence of various iterative restoration algorithms. We found that most algorithms converged for most choices, but that smoothed first estimates resulted in a faster convergence.
Improved estimation of the pair correlation function of random sets
Authors: Mattfeldt T. , Stoyan D.
Published: March 2003

The texture of binary spatial structures can be characterized by second‐order methods of spatial statistics. The pair correlation function, which describes the structure in terms of spatial correlation as a function of distance, is of central importance in this context. Conventionally, the pair correlation function of stationary and isotropic random sets is estimated as the ratio of the covariance to the square of volume fraction of the phase of interest. In the present paper, an improved estimator of the pair correlation function is presented, where the covariance is divided by the square of a distance‐adapted estimator of volume fraction. The new estimator is explained mathematically and applied to simulated images of the Boolean model and to microscopic images from neoplastic and non‐neoplastic human glandular tissues. It leads to a considerable reduction of bias and variance of estimated pair correlation functions, in particular for large distances.
Coaxial scanning near‐field optical microscope tips: an alternative for conventional tips with high transmission efficiency?
Authors: Demming F. , Jersch J. , Klein S. , Dickmann K.
Published: March 2003

Since the development of the first scanning near‐field optical microscope, great effort has been put into the development of near‐field optical probe tips with a good lateral resolution of the order of several tens of nanometres and a high power throughput. Several groups have proposed the use of scanning near‐field optical tips with a coaxial structure. From electromagnetic theory, it is known that such structures have no cut‐off frequency and a power transmission close to unity. In this paper we discuss some topics concerning the stimulation of optical coaxial waves and their propagation behaviour.
Phase identification of individual crystalline particles by electron backscatter diffraction
Authors: Small J. A. , Michael J. R.
Published: March 2003

Recently, an electron backscatter diffraction (EBSD) system was developed that uses a 1024 × 1024 CCD camera coupled to a thin phosphor. This camera has been shown to produce excellent EBSD patterns. In this system, crystallographic information is determined from the EBSD pattern and coupled with the elemental information from energy or wavelength dispersive X‐ray spectrometry. Identification of the crystalline phase of a sample is then made through a link to a commercial diffraction database. To date, this system has been applied almost exclusively to conventional, bulk samples that have been polished to a flat surface. In this investigation, we report on the application of the EBSD system to the phase identification analysis of individual micrometre and submicrometre particles rather than flat surfaces.
Tapping‐mode tuning‐fork near‐field scanning optical microscopy of low power semiconductor lasers
Authors: Lu N. H. , Lin W. C. , Tsai D. P.
Published: March 2003

The newly developed inverted tapping‐mode tuning‐fork near‐field scanning optical microscopy (TMTF‐NSOM) is used to study the local near‐field optical properties of strained AlGaInP/Ga0.4In0.6P low power visible multiquantum‐well laser diodes. In contrast to shear‐force mode NSOM, TMTF‐NSOM provides the function to acquire the evanescent wave intensity ratio |I(2ω)|/|I(ω)| image, from which the evanescent wave decay coefficient q can be evaluated for a known tapping amplitude. Moreover, we probe the near‐field stimulated emission spectrum, which gives the free‐space laser light wavelength λo and the index of refraction nr of the laser diode resonant cavity. Once q, λo, and nr are all measured, we can determine the angle of incidence θo of the dominant totally internally reflected waves incident on the front mirror facet of the resonator. Determination of such an angle is very important in modelling the stability of the laser diode resonator.