bluuebunny/crossref_metadata_2025 huggingface dataset:
The spectrum of carcinoid tumours and carcinoid syndromes
Authors: Lips Cornelis JM , Lentjes Eef GWM , Höppener Jo WM
Published: October 2003

Carcinoids are neuroendocrine tumours of the gut which may also be found in the bronchus, pancreatic islets and retroperitoneum. They probably arise from gastrointestinal or bronchopulmonary pluripotential stem cells. Carcinoid tumours derived from these cells are potentially malignant; the strength of the tendency for aggressive growth correlates with the site of origin, depth of local penetration and the size of the tumour. Carcinoids occur sporadically or result from specific hereditary tumour syndromes. Mutations and/or aberrant expression of specific genes induce and promote tumour growth. Clinical features include local symptoms due to angulation or obstruction and hepatomegaly due to liver metastases.

The carcinoid syndrome commonly involves flushing, diarrhoea, bronchospasm and hypotension. Other distinct syndromes may be caused by tumour release of products that may also be used as biochemical markers in diagnosis and follow-up. Scanning using radiolabelled octreotide, an analogue of somatostatin, sensitively identifies occult primary and metastatic deposits.

Localized carcinoid tumours should be resected. Some patients benefit from hepatic resection. Palliation of symptoms is best achieved with octreotide. Hepatic artery chemoembolization may produce long-acting palliation.

Further genetic characterization of the different types and stages of carcinoid development as well as assessment of gene expression profiles may improve differential diagnosis, prognosis and treatment.
Tumour markers: their use and misuse by clinicians
Authors: McGinley Peter J , Kilpatrick Eric S
Published: October 2003

Background: Several guidelines exist on the appropriate use of serum tumour markers in the management of patients with cancer. This study audited tumour marker requesting against these guidelines in a busy teaching hospital over a 12-month period.

Methods: All marker requests from 1 April 2001 to 31 March 2002 were collected using the laboratory computer. From one 24-h period, the case notes from all hospital requests [excluding prostate-specific antigen (PSA)] were examined.

Results: Tumour marker workload increased by 125% from 1997-98 to 2001-02. Of 27 323 tumour marker requests, 7166 were from general practice, 2312 were requested on hospital admission before further investigation, 612/3636 of CA125 and 98/374 of CA15.3 requests were on men and 12/11585 PSA requests on women. Of 34 case notes examined, 18 had tumour markers measured before biopsy and only nine after. Of 19 patients with 'normal' markers, one had malignancy on biopsy and, of 15 with one or more raised markers, four had normal biopsies.

Conclusions: Tumour marker workload is rapidly increasing. Tumour markers are frequently and inappropriately requested, either because they are on patients of the wrong sex, or because they are taken before a cancer diagnosis is reached. Results from these tests can be falsely reassuring or unduly alarming.
Cystatin C improves the detection of mild renal dysfunction in older patients
Authors: O'Riordan Shelagh E , Webb Michelle C , Stowe Helen J , Simpson David E , Kandarpa Madhu , Coakley Anthony J , Newman David J , Saunders Jean A , Lamb Edmund J
Published: October 2003

Background: Conventional estimates of glomerular dysfunction, including serum creatinine and creatinine clearance, are inadequate in older people. In this study we have compared the diagnostic accuracy of a novel test of kidney disease, cystatin C, against these markers in older patients with a range of renal function.

Methods: Fifty-three patients (mean age 79.6 years, range 69-92 years) with a variety of medical diagnoses were recruited via outpatient clinics. Exclusion criteria included active rheumatoid disease, known current malignancy, renal replacement therapy/renal transplantation and cognitive impairment. 51Cr-EDTA was used as the reference method against which the other markers of glomerular filtration rate were compared using regression analyses.

Results: The best fit with glomerular filtration rate was given by Cockcroft and Gault calculated clearance ( R2 = 0.83), followed by serum cystatin C ( R2 = 0.79), serum creatinine ( R2 = 0.76) and creatinine clearance ( R2 = 0.73). The accuracy for glomerular filtration rate prediction was poor for all markers. Serum cystatin C detected nearly all patients with mild renal impairment whereas serum creatinine only detected half of these cases. Regression modelling predicted that the upper limit of normal for serum cystatin C would be exceeded as glomerular filtration rate fell below 64 mL/min/1.73 m2, compared with 44 mL/min/1.73 m2 for serum creatinine.

Conclusion: Serum cystatin C is a simple and sensitive screening test for kidney dysfunction in older people.
Measurement of renal function in kidney donors using serum cystatin C and β2-microglobulin
Authors: John George T , Fleming Jude Joseph , Talaulikar Girish S , Selvakumar R , Thomas Paaulose P , Jacob Chakko K
Published: October 2003

Background: The usefulness of serum cystatin C and serum β2-microglobulin (B2M) as markers of glomerular filtration rate (GFR) were compared in kidney donors before and after nephrectomy.

Methods: Blood samples were taken from 28 donors (15 women and 13 men) for serum creatinine, urea, cystatin C and B2M estimation a median of 7 days before and 10 days after nephrectomy.

Results: Estimated GFR decreased from a median of 86.2 mL/min/1.73 m2 to 60.3 mL/min/1.73 m2, a median decrease of 28.6%. Serum creatinine increased by 40% and urea by 30.4%; serum cystatin C increased by 31.2% and serum B2M increased by 65.6%. Using published data on biological variation, critical values were calculated. An increase in serum creatinine above 18 µmol/L detected the decline in renal function in 26/28 (92.9%) subjects. Increases in serum B2M greater than a critical value of 0.94 mg/L detected 24/28 (85.7%) of these subjects, but the critical value of 0.59 mg/L for cystatin C detected only 8/28 (28.6%).

Conclusion: Using critical values, serial measurement of serum creatinine was better than serum B2M in detecting reduced renal function. Because of its large intraindividual variation, serial serum cystatin C estimation was very poor in detecting reduced renal function.
Clinical and technical evaluation of the ACS:OV serum assay and comparison with three other CA125-detecting assays
Authors: Davelaar Elvira M , Schutter Eltjo MJ , von Mensdorff-Pouilly Silvia , van Kamp Gerard J , Verstraeten Rob A , Kenemans Peter
Published: October 2003

Background: In this study the clinical and technical performance of the CA125- detecting Bayer ACS:OV immunoluminometric serum assay was compared with three other well-established CA125-detecting assays.

Methods: A total of 1112 serum samples was included in this evaluation: 462 from apparently healthy women, 153 from patients with benign ovarian disease, 163 from patients with malignant ovarian disease, 10 from patients with borderline ovarian malignancies and 78 samples from 12 ovarian cancer patients during monitoring of disease. Serum samples from women with malignant endometrial ( n = 68) and colon ( n = 32) diseases were also included. Moreover, serum samples from women with benign uterine disease and endometriosis ( n = 136) plus 10 serum samples from men ( n = 7) and women ( n = 3) with human anti-mouse antibodies (HAMA) after immunoscintigraphy were included. All samples were tested in duplicate with the Bayer ACS:OV, the Centocor CA125 II, the Abbott IMx CA125 and the Roche (formerly Boehringer Mannheim) Enzymun-Test® CA125 II assays.

Results: The clinical performance of the Bayer ACS:OV assay, assessed in various patient groups, was similar to that of the two other automated assays. In serum from patients with benign diseases the highest values were found in patients with benign ovarian tumours. In the ovarian cancer patients followed during the course of disease we found similar marker patterns with all four assays. In contrast to the Roche Enzymun-CA125 II assay and to a lesser extent the Centocor CA125 II assay, the Bayer ACS:OV assay was less sensitive to interference from HAMA.

Conclusion: The Bayer ACS:OV assay is a precise and reliable test for the quantification of CA125 in serum.
Feedback from a point-of-care test for nicotine intake to reduce smoking during pregnancy
Authors: Cope Graham F , Nayyar Pamela , Holder Roger
Published: October 2003

Background: Smoking is the most important modifiable risk factor for adverse pregnancy outcome in the UK. New tools are needed to improve smoking cessation advice. The aim was to investigate a point-of-care urine test for smoking, to provide feedback to women, to improve awareness about the effects of smoking during pregnancy and to relate the test results to pregnancy outcome.

Methods: A cross-sectional randomized controlled trial involving 856 pregnant women. All intervention patients were interviewed at their initial visit and tested for smoking. The test provided visual and numerical feedback. Smokers were followed up and retested at subsequent visits. The control group received anti-smoking counselling as part of routine care, but their smoking was monitored using the test. Both groups were interviewed and retested at 36 weeks' gestation.

Results: Self-reported cigarette consumption fell significantly ( P < 0.001) in the intervention group, with 16.2% giving up and 33.3% significantly reducing their cigarette consumption. There was a significant fall in test results from 'booking' to 36 weeks' gestation ( P < 0.0001). In the control group, only 8% reported stopping and 23% reducing their cigarette consumption. Combined smoking test results at 36 weeks correlated significantly with birth weight ( P = 0.006) and body length ( P = 0.011).

Conclusions: Point-of-care testing and feedback coupled with counselling can significantly reduce smoking during pregnancy and increase birthweight.
Use of fluorescence polarization immunoassay for salicylate to avoid positive/negative interference by bilirubin in the Trinder salicylate assay
Authors: Dasgupta Amitava , Zaidi Syed , Johnson Myrtle , Chow Loretta , Wells Alice
Published: October 2003

Background: Significant positive bias of bilirubin in the Trinder salicylate method on automated analysers has been reported. Because the fluorescence polarization immunoassay (FPIA) for salicylate is also widely used in the clinical laboratory, we studied the potential interference of bilirubin in the salicylate FPIA.

Methods: Salicylate serum pools (three different pools) were prepared from patients receiving salicylate. We also prepared a normal serum pool containing no salicylate and serum pools containing no salicylate but elevated bilirubin. Aliquots of one salicylate pool were supplemented with various concentrations of bilirubin (42.8- 427.5 µmol/L) and salicylate concentrations were measured by the salicylate FPIA (TDxFLx and AxSYM analysers). We also assayed these specimens with the Trinder salicylate method, using both Synchron LX and Hitachi 917 analysers for comparison with the results obtained by the FPIA method. In another experiment, aliquots of the two other salicylate pools were supplemented with various concentrations of bilirubin (42.8-684.0 µmol/L) in order to further study the effect of very high bilirubin concentrations on the salicylate FPIA. We also added known amounts of salicylate to serum pools containing elevated bilirubin but no salicylate and measured salicylate using the FPIA in order to study the recovery of salicylate in the presence of elevated bilirubin concentrations.

Results: The FPIA showed minimal interference from bilirubin. We also observed good recovery of salicylate when specimens high in bilirubin but containing no salicylate were supplemented with known amounts of salicylate and the FPIA was used for the measurement of salicylate concentration. However, we observed falsely low salicylate concentrations with the Trinder method using the Synchron LX (primary wavelength 560 nm, secondary wavelength 700 nm) analyser and falsely increased salicylate concentrations using the same reagent but the Hitachi 917 (primary wavelength 546 nm, no secondary wavelength) analyser in the presence of elevated bilirubin levels compared with the FPIA results.

Conclusion: We conclude that the FPIA for salicylate is not affected by high bilirubin concentrations up to 427.5 µmol/L.
Insulinoma: how reliable is the biochemical evidence?
Authors: Chammas NK , Teale JD , Quin JD
Published: October 2003

Background and methods: We report a case of insulinoma in which the diagnosis was very challenging as some of the biochemical data were consistently equivocal. In order to assess the relative reliability of the analytical tests, retrospective biochemical data on 45 other cases of histologically confirmed insulinoma were evaluated, enabling the most secure diagnostic process to be identified.

Results: The data showed that insulin concentrations alone, although measurable, were equivocal in 17% of cases. The addition of C-peptide values clarified the diagnosis in about 50% of the borderline cases, whilst ketone ( β-hydroxybutyrate) concentrations were low during the prevailing hypoglycaemia in all cases.

Conclusion: The combination of these three tests is suggested as the most effective method for the biochemical diagnosis of hypoglycaemia due to insulinoma.
Evaluation of the Dade Behring Syva® EMIT 2000 tacrolimus assay on the Bayer Advia 1650
Authors: Stephen DWS , Rooke P , Clark S , Coutts M , Crowe L , Docherty D
Published: October 2003

Background: The Dade Behring Syva® EMIT (enzyme multiplied immunoassay technique) method for the measurement of tacrolimus in whole blood was evaluated against the Abbott IMx® microparticle enzyme immunoassay (MEIA) method. EMIT measures tacrolimus colorimetrically, whereas MEIA measures the analyte using fluorimetry. Both methods incorporate a protein precipitation step prior to measurement.

Method: Whole blood specimens were treated by two types of precipitation technique followed by analysis for tacrolimus by either MEIA or EMIT on the Bayer Advia 1650. Linearity and precision were assessed and correlation analysis performed to evaluate the EMIT assay on the Bayer Advia 1650.

Results: The EMIT tacrolimus assay was linear over the concentration range 0.0-22.0 µg/L; the limit of detection was 1.2 µg/L. Correlation between the Syva EMIT and IMx tacrolimus assays was excellent ( r = 0.959) and no significant bias existed between the two methods (mean difference, δ = 0.221 µg/L). Calibration data for the EMIT assay was stable for a period of 24-48 h on the Advia between runs.

Conclusion: The Syva EMIT assay for the measurement of tacrolimus in whole blood is suited for daily routine use on the Bayer Advia 1650.
Biochemical Pathways for Microvascular Complications of Diabetes Mellitus
Authors: Setter Stephen M , Campbell R Keith , Cahoon Clifton J
Published: October 2003

OBJECTIVE:

To review the current biochemical theories on how diabetes contributes to microvascular disease.

DATA SOURCES:

MEDLINE search (1980–June 2003) and bibliographies of articles obtained on this topic.

STUDY SELECTION AND DATA EXTRACTION:

Articles identified from the data sources were evaluated and those deemed relevant to this review were incorporated.

DATA SYNTHESIS:

The prevailing biochemical theories on how diabetes leads to microvascular disease include increased polyol (sorbitol/aldose reductase) pathway flux, production of advanced glycation end-products, generation of reactive oxygen species, and activation of diacylglycerol and protein kinase C isoforms. These pathways contribute to endothelial damage and dysfunction and may alter gene functioning.

CONCLUSIONS:

Each pathway, via varied and often overlapping mechanisms, contributes to altered microvascular function that leads to the development of retinopathy, neuropathy, and nephropathy, the major microvascular complications associated with diabetes.
Efficacy of Stimulants in Adult ADHD
Authors: Maidment Ian D
Published: October 2003

OBJECTIVE:

To review the literature regarding the efficacy of stimulants to treat attention-deficit-hyperactivity disorder (ADHD) in adults.

DATA SOURCES:

The relevant pharmaceutical manufacturers were contacted, and searches of MEDLINE (1966–December 2002) and the reference sections of each article obtained were performed using the key search terms: adult ADHD, stimulants, methylphenidate, amphetamines, and pemoline.

STUDY SELECTION AND DATA EXTRACTION:

All English-language original studies identified from the data sources were evaluated and all information deemed relevant was included in the review.

DATA SYNTHESIS:

Studies involving methylphenidate, amphetamines, and pemoline were identified. There was evidence for the efficacy of amphetamines from 5 studies (4 controlled, 1 open). Methylphenidate data from 6 controlled trials were conflicting. Three studies indicated efficacy; 2 studies failed to show efficacy, possibly due to methodologic reasons; and the results from 1 study were conflicting. The limited data from 1 controlled and 1 open study indicated that pemoline may be less effective than methylphenidate and amphetamines.

CONCLUSIONS:

While the current limited data indicate that stimulants may be effective in adult ADHD, more data are required to confirm long-term efficacy.
Trastuzumab for the Treatment of Non—Small-Cell Lung Cancer
Authors: Ferrone Marcus , Motl Susannah E
Published: October 2003

OBJECTIVE:

To evaluate trastuzumab for the treatment of advanced non—small-cell lung cancer (NSCLC).

DATA SOURCES:

Clinical literature was accessed through MEDLINE (1966–January 2003), EMBASE (1974–January 2003), International Pharmaceutical Abstracts (1970–January 2003), Proceedings of the American Society of Clinical Oncology (1995–January 2003), and Genentech. Key search terms included trastuzumab, lung cancer, Herceptin, and NSCLC.

DATA SYNTHESIS:

Research has revealed that NSCLC specimens may express the protein HER-2/neu. The monoclonal antibody against HER-2/neu, trastuzumab, could prove valuable for patients. An evaluation of the studies exploring trastuzumab for management of NSCLC was conducted. Phase II clinical trials reveal variable response rates from no improvement to a partial response rate of 42%. Due to a lack of clinical trials and deficiencies in the literature, the ultimate benefit of this agent remains to be proven.

CONCLUSIONS:

Clinical data from ongoing trials indicate potential synergy when trastuzumab is added to standard chemotherapy. The ultimate benefit in NSCLC remains to be proven.
Intravenous Valproate Associated with Circulatory Collapse
Authors: Kumar Prashant , Vallis Christopher J , Hall Catherine M
Published: October 2003

OBJECTIVE:

To report a case of severe circulatory collapse following an intravenous injection of sodium valproate.

CASE SUMMARY:

A 5-year-old white girl, who was receiving vasopressor support, developed a severe circulatory collapse following an intravenous injection of valproate 480 mg. Her invasive arterial blood pressure dropped after valproate was started, and she went into cardiac arrest requiring full resuscitation including 2 doses of epinephrine. She was successfully resuscitated.

DISCUSSION:

To the best of our knowledge, this is the first case report of such severe circulatory collapse associated with intravenous valproate. Although hypotension has been reported following the use of intravenous valproate, severe circulatory compromise leading to cardiorespiratory arrest has not been previously described. An objective causality assessment using the Naranjo probability scale revealed that the adverse drug event was highly possible.

CONCLUSIONS:

In view of this patient's circulatory collapse associated with valproate, intravenous sodium valproate should be used with caution, particularly in hemodynamically unstable patients.
Effect of Renal Function on the Pharmacodynamics of Argatroban
Authors: Arpino Paul A , Hallisey Robert K
Published: October 2003

BACKGROUND:

Argatroban is a direct thrombin inhibitor used to treat heparin-induced thrombocytopenia (HIT). Argatroban is primarily cleared by hepatic mechanisms, with only small amounts of unchanged drug cleared by the kidneys.

OBJECTIVE:

To assess the effects of renal function on argatroban dose and activated partial thromboplastin time (aPTT).

METHODS:

Patients treated with argatroban were identified and prospectively screened. Patients with liver dysfunction were excluded from the analysis. Charts and laboratory data were reviewed daily until a therapeutic aPTT was reached or argatroban was discontinued. Data points collected included age, weight, gender, admitting diagnosis, past medical history, indication for anticoagulation, indication for argatroban, initial dose, goal aPTT, titration instructions, liver function tests, serum creatinine (Scr), blood urea nitrogen, and estimated creatinine clearance (Clcr).

RESULTS:

A total of 66 patients were evaluated and 44 met criteria for inclusion. Baseline Scr was elevated at 1.5 mg/dL (0.9, 2.3; median 25th, 75th percentile), with an estimated Clcr 40 mL/min/1.73 m2 (26, 74). The median dose of argatroban to reach the predefined therapeutic range was 1 μg/kg/min (0.68, 2), with a corresponding aPTT of 60 seconds (54, 66). After univariate analysis, Clcr significantly predicted the therapeutic dose (coefficient b ± SE 0.019 ± 0.004; r2 0.35; p < 0.001). Covariates that predicted dose were the presence of HIT (coefficient b ± SE −0.61 ± 0.3; p = 0.045), history of myocardial infarction (coefficient b ± SE −0.74 ± 0.3; p = 0.02), and an indication for anticoagulation of deep-vein thrombosis/pulmonary embolism (coefficient b ± SE 0.69 ± 0.3; p = 0.03).

CONCLUSIONS:

Estimated Clcr significantly predicted the dose of argatroban needed to reach a therapeutic aPTT.
Colchicine-Induced Myopathy in a Teenager with Familial Mediterranean Fever
Authors: Sayarlioglu Mehmet , Sayarlioglu Hayriye , Ozen Suleyman , Erkoc Reha , Gul Ahmet
Published: October 2003

OBJECTIVE:

To report a case of colchicine-induced myopathy in a teenager with familial Mediterranean fever (FMF).

CASE SUMMARY:

A 15-year-old boy of Turkish origin, diagnosed as having FMF at the age of 14 years, was treated with colchicine 1.5 mg/d. He had experienced only 2 mild peritonitis attacks with fever within 1 year. The patient used the recommended dose regularly, and he described progressive proximal muscle weakness and generalized myalgias, which started 1 month before presentation. Physical examination showed proximal muscle weakness in his arms and legs. Laboratory tests revealed elevated serum creatine kinase, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase. All other laboratory values were within normal range. Electromyographic investigation revealed a myopathic pattern in proximal muscles without any neuropathic changes. A biopsy of the deltoid muscle showed vacuolar degeneration of striated muscle fibers with no inflammatory findings.

DISCUSSION:

Colchicine, the most important drug in treatment of FMF, can cause myopathy in patients with impaired renal and hepatic function. In our patient, an objective causality scale showed that therapeutic doses of colchicine for FMF were the definite cause of myopathy, even though his renal and hepatic function were normal. The treatment of FMF attacks in patients who cannot use colchicine is an important problem. There are insufficient data about the use of immunosuppressive agents in the treatment of FMF attacks; however, we now successfully control the attacks with colchicine 0.5 mg/d and azathioprine 2 mg/kg/d.

CONCLUSIONS:

Colchicine-induced myopathy should be excluded in patients with FMF who present with generalized muscle weakness. Clinicians should be aware that myopathy can occur in patients with FMF who have normal renal and hepatic function.
Education and Training, Public Education about Genetic Technology
Authors: McInerney Joseph D.
Published: October 2003

Introduction

Challenge 1: Selecting the Content

Challenge 2: Explaining the Nature of Science

Challenge 3: The Principles of Technology

Challenge 4: The Personal and Social Impact of Science and Technology
Federal Policy Making for Biotechnology, Executive Branch,
N
ational
B
ioethics
A
dvisory
C
ommission
Authors: Shapiro Harold T.
Published: October 2003

Introduction

Historical Background

The National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research (The National Commission)

The Ethics Advisory Board

The President's Commission

The Biomedical Ethics Advisory Committee

The NIH Human Fetal Tissue Transplantation Research Panel

The NIH Human Embryo Research Panel

Bioethical Analyses in Other Federal Settings

President's Advisory Committee on Human Radiation Experiments

Establishment of the National Bioethics Advisory Commission
Gene Therapy, Ethics, Somatic Cell Gene Therapy
Authors: Wivel Nelson A.
Published: October 2003

Introduction

Development of Science and Concepts Leading to Gene Therapy

Origins and Evolution of Public Oversight of Human Gene Therapy

Principles of Review for Human Gene Therapy

Human Gene Therapy and the Industry Model for Drug Development

Challenges for the Future
Eugenics, Ethics
Authors: McGee Glenn , Magnus David
Published: October 2003

Introduction

History

Coercive Versus Voluntary

Positive and Negative

Population and Individual

Modern Dilemmas and Eugenics
Genetic Determinism, Genetic Reductionism, and Genetic Essentialism
Authors: Wachbroit Robert
Published: October 2003

Introduction

Determinism: Genetic and Otherwise

Reductionism: Genetic and Otherwise

Essentialism: Genetic and Otherwise
Gene Therapy: Overview
Authors: Walters LeRoy
Published: October 2003

Terminology

Major Modes of Human Genetic Intervention

Early Attempts at Human Gene Transfer

Development of a Review Process for Gene Transfer Research in the United States

Early Years of Publicly Approved Gene Transfer Research

Gene‐Transfer Research and Oversight Policies in Other Nations

Audits of 1995 and the Crisis of 1999 in the United States

Prospects for the Future
Patents and Licensing, Ethics, Organizations with Prominent Positions on Gene Patenting
Authors: Cole‐Turner R.
Published: October 2003

Introduction

Religious Organizations

Indigenous Peoples and their Coalitions

Environmental Groups

Public Interest Science Groups

Scientific Organizations

Industry Organizations
Bonding in Metals
Authors: Watson R.E. , Weinert M.
Published: October 2003

The conditions controlling alloy phase formation have been of concern for a long time, even in the period prior to the advent of the first computer‐based electronic structure calculations in the 1950s. In those days, the role of such factors as atomic size and valence were considered, and significant insight was gained, associated with names such as Hume‐Rothery. In recent times, electronic structure calculations have yielded the total energies of systems, and hence the heats of formation of competing real and hypothetical phases. Doing this accurately has become of increasing importance as the groups capable of thermodynamic measurements have dwindled in number.

This article concentrates on the alloys of the transition metals and considers both the old and the new. In the first part, some of the ideas concerning metallic bonding that derive from the early days are inspected. Many of these ideas are still applicable and offer insights into alloy phase behavior that are computationally cheaper, and in some cases rather different, from those obtainable from detailed computation. In the second part, the present‐day total‐energy calculations are presented. Comparisons between theoretical and experimental heats of formation are not made, because the spreads between experimental heats and their computed counterparts are not altogether satisfying for metallic systems. Instead, the factors controlling the accuracy of the computational methods and the precision with which they are carried out are inspected. All too often, consideration of computational costs leads to results that are less precisely defined than is needed.
Dynamical Diffraction
Authors: Shen Qun
Published: October 2003

Diffraction‐related techniques using x rays, electrons, or neutrons are widely used in materials science to provide basic structural information on crystalline materials. To describe a diffraction phenomenon, one has the choice of two theories: kinematic or dynamical.

Kinematic theory assumes that each x‐ray photon, electron, or neutron scatters only once before it is detected. This assumption is valid in most cases for x rays and neutrons since their interactions with materials are relatively weak. This single‐scattering mechanism is also called the first‐order Born approximation or simply the Born approximation. The kinematic diffraction theory can be applied to a vast majority of materials studies and is the most commonly used theory to describe x‐ray or neutron diffraction from crystals that are imperfect.

There are, however, practical situations where the higher‐order scattering or multiple‐scattering terms in the Born series become important and cannot be neglected. This is the case, for example, with electron diffraction from crystals, where an electron beam interacts strongly with electrons in a crystal. Multiple scattering can also be important in certain application areas of x‐ray and neutron scattering, as described below. In all these cases, the simplified kinematic theory is not sufficient to evaluate the diffraction processes and the more rigorous dynamical theory is needed where multiple scattering is taken into account.

Dynamical diffraction is the predominant phenomenon in almost all electron diffraction applications, such as low‐energy electron diffraction and reflection high‐energy electron diffraction. For x rays and neutrons, areas of materials research that involve dynamical diffraction may include the situations discussed.
Tension Testing
Authors: Antolovich Stephen D.
Published: October 2003

Of all mechanical properties, perhaps the most fundamental are related to what happens when a material is subjected to simple uniaxial tension. In its essence, a tensile test is carried out by attaching a specimen to a load‐measuring device, applying a load (or imposing a given deformation), and measuring the load and corresponding deformation.

The result obtained from a tensile test is a so‐called stress/strain curve, a plot of stress (force/unit area) versus strain. The results of such a test (along with the results of other tests, to be sure) are basic to determination of the suitability of a given material for a particular load‐bearing application. In this regard the results obtained from such a test are of great engineering significance. Tensile‐test results also provide a great deal of information relative to the fundamental mechanisms of deformation that occur in the specimen. Coupled with microscopic examination, tensile test results are used to develop theories of hardening and to develop new alloys with improved properties. Tensile tests can be used to obtain information on the following types of properties: elastic properties, plastic properties, toughness.
Tribological and Wear Testing
Authors: Bayer Raymond G.
Published: October 2003

Tribology is the science of friction, wear, and lubrication. More fundamentally, tribology is concerned with the interaction of contacting surfaces in relative motion. Friction is the resisting tangential force that occurs between two surfaces in contact when they move or tend to move relative to one another. For solid surfaces the magnitude of this force is characterized by the coefficient of friction, defined as the dimensionless ratio of the magnitude of the friction force to the magnitude of the normal force. In the absence of an externally applied normal force, this tangential force is sometimes referred to as sticktion. Wear is damage to a solid surface due to the relative motion between that surface and a contacting substance or substances. It involves the progressive loss of material. Lubrication is the ability of an interposing material to reduce either the friction between or the wear of surfaces.

The tribological behavior that a material exhibits is dependent on both the properties of the material and the contact conditions. As a result, parameters used to characterize the friction, wear, and lubrication of a material are system properties of the material, not intrinsic properties such as an elastic modulus or coefficient of thermal expansion. The collection of all those elements that can influence tribological behavior is referred to as the tribosystem. The primary elements of a tribosystem are (1) materials, (2) shapes and contours, (3) surface roughness, (4) motions, (5) loading, (6) lubrication, and (7) environment.
Differential Thermal Analysis and Differential Scanning Calorimetry
Authors: Lexa Dusan , Leibowitz Leonard
Published: October 2003

Differential thermal analysis (DTA) and differential scanning calorimetry (DSC) are two closely related methods in which a material under investigation is typically subjected to a programmed temperature change and thermal effects in the material are observed. (Isothermal methods are also possible though they are less common.) The term “differential” indicates that the difference in behavior between the material under study and a supposedly inert reference material is examined. In this manner the temperature at which any event either absorbs or releases heat can be found. This allows the determination of, e.g., phase transition temperatures and the study of order‐disorder transitions and chemical reactions. Similarly, heat capacity measurements can be performed, although DTA and DSC differ significantly in the ease and precision of such measurements. These two methods are ideally suited for quality control, stability, and safety studies.

Measurement of heat capacity can be performed by other methods and these are discussed.

In DTA, the temperature difference between a substance and a reference material is measured as a function of temperature while the substance and reference material are subjected to a controlled temperature program.

The record is the differential thermal, or DTA, curve; the temperature difference should be plotted on the ordinate with endothermic reactions downward and temperature or time on the abscissa increasing from left to right.

The term “quantitative differential thermal analysis” (quantitative DTA) covers those uses of DTA where the equipment is designed to produce quantitative results in terms of energy and/or any other physical parameter.

In DSC, the difference in energy inputs into a substance and a reference material is measured as a function of temperature while the substance and reference material are subjected to a controlled temperature program.

Two modes, power compensation differential scanning calorimetry (power compensation DSC) and heat‐flux differential scanning calorimetry (heat‐flux DSC), can be distinguished, depending on the method of measurement used.

These thermal analysis methods can be conducted simultaneously with other measurement methods to provide a greatly enhanced ability to understand material behavior.

There is widespread confusion in the literature and elsewhere regarding the terms DTA and DSC that stems, in part, from how these methods developed and this is discussed.
Hall Effect in Semiconductors
Authors: Look David
Published: October 2003

The Hall effect, which was discovered in 1879, determines the concentration and type (negative or positive) of charge carriers in metals, semiconductors, or insulators. In general, the method is used in conjunction with a conductivity measurement to also determine the mobility (ease of movement) of the charge carriers. At low temperatures and high magnetic fields, quantum effects are sometimes evident in lower dimensional structures; however, such effects are not be considered here. Also, this article concentrates on semiconductors, rather than metals or insulators, although the same theory generally applies.

Three, strong advantages of Hall effect measurements are ease of instrumentation, ease of interpretation, and wide dynamic range. With respect to implementation, the only elements necessary, at the lowest level, are a current source, a voltmeter, and a modest‐sized magnet. The carrier concentration can then be calculated within a typical accuracy of 20% without any other information about the material. Measurments of concentrations ranging from 10
4
to 10
20
cm
−3
have been obtained. Also, the type (
n
or
p
) can be unambiguously determined from the sign of the Hall voltage.

Competing techniques include capacitance‐voltage (
C
‐
V
) measurements to determine carrier concentration; thermoelectric probe (TEP) measurements to determine carrier type; and magnetoresistance (MR) measurements to determine mobility.
Magnetometry
Authors: Guertin Robert P. , Foner Simon
Published: October 2003

All materials possess a magnetic moment; techniques for measuring that bulk macroscopic property are defined here as magnetometry. This article reviews the most common techniques for measuring the total magnetic moments of small samples (volume ≤1 cm3and/or mass ≤1 g). Several factors contribute to the bulk magnetic moment of a sample. Essentially all materials show weak diamagnetism from filled electronic core states of the atoms. Metallic materials show an additional contribution to their diamagnetism from the orbital motion of the otherwise degenerate spin‐up and spin‐down conduction electrons as well as Pauli paramagnetism from splitting of the conduction bands. The largest contribution to the magnetic moment of materials comes from unpaired localized spins of elemental constituents.

It is important for many reasons to know a material's magnetic moment, a thermodynamic quantity. For strongly magnetic materials, it is probably the most useful and important physical property, determining their utility in applications. For magnetically ordered systems, magnetic moment measurements provide information about spin structure, anisotropy (in the case of nonpolycrystalline samples), and phase transitions. For paramagnetic systems, the total moment at high fields or the temperature dependence of the magnetic susceptibility can yield a measure of the moment per chemical constituent or magnetic impurity concentration, whether introduced purposefully or as impurities. The temperature dependence of the moment yields information on interactions between the paramagnetic ions or with the lattice. Certain features of the electronic structure of metallic materials can be determined from magnetic susceptibility, such as the density of states at the Fermi surface. For superconductors, high field magnetization can provide information about the critical field and critical current density.

This article is restricted to the centimeter‐gram‐second (cgs) system of units for the magnetic moment, which is given in electromagnetic units (emu), where 1 emu = 10−3A‐m2.

There are two direct techniques for measuring the magnetic moment of materials: one utilizes the detection of a change in magnetic flux produced by a sample, and the other utilizes the detection of a change in the force experienced by a sample.
Cyclic Voltammetry
Authors: Bocarsly Andrew B.
Published: October 2003

A system is completely characterized from an electrochemical point of view if its behavior in the three‐dimensional (3D) space composed of current, potential, and time is fully specified. In theory, from such phenomenologic data one can determine all of the system's controlling thermodynamic and kinetic parameters, including the mechanism of charge transfer, rate constants, diffusion coefficients, standard redox potentials, electron stoichiometry, and reactant concentrations.

The enormous information content and complexity of electrochemical dynamics in the current‐potential‐time domain introduces two major experimental complications associated with electrochemical data. First is the pragmatic consideration of how much time is necessary to obtain a sufficiently complete data set to allow for a useful analysis. The second, far more serious complication is that different charge‐transfer mechanisms often translate into subtle changes in the
i
(
E
,
t
) response. Thus, even after one has access to a complete data set, visual inspection is typically an insufficient means to determine the mechanism of charge transfer. Furthermore, knowledge of this mechanism is critical to determining the correct approach to data analysis. Thus, given the requisite data set, one must rely on a series of large calculations to move from the data to chemically meaningful parameters.

The approach described so far is of limited value as a survey tool, or as a global mechanistic probe of electrochemical phenomena. It is, however, a powerful technique for obtaining precise thermodynamic and kinetic parameters once the reaction mechanism is known. The mathematical resolution to the problem posed here is to consider the projection of the
i
(
E
,
t
) surface onto a plane that is not parallel to the
i
‐
E
‐
t
axis system. This is the basis of cyclic voltammetry. A single projection is not sufficient to completely characterize a system; however, if judiciously chosen, a limited set of projections (on the order of a half dozen) will provide sufficient information to determine the reaction mechanism and obtain the key reaction parameters to relatively high precision. Perhaps more importantly, reduction of the data to two dimensions allows one to determine the mechanism based on pattern recognition, and thus no calculational effort is required.

The qualitative aspect of cyclic voltammetry has made it a general tool for the evaluation of electrochemical systems. With regard to materials specifically, the technique has found use as a method for investigating the electrosynthesis of materials (including conducting polymers and redox‐produced crystalline inorganics), the mechanism of corrosion processes, the electrocatalytic nature of various metallic systems, and the photoelectrochemical properties of semiconducting junctions. Here a general description of the cyclic voltammetric technique is provided along with some examples focusing on materials science applications.
Optical Imaging and Spectroscopies
Authors: Samuels Alan C.
Published: October 2003

All materials absorb and emit electromagnetic radiation. The characteristics of a material frequently manifest themselves in the way it interacts with radiation. The fundamental basis for the interaction varies with the wavelength of the radiation, and the information gleaned from the material under study will likewise vary. Materials interact with radiation in some fashion across the entire electromagnetic spectrum, which can be thought of as spanning the frequency realm from near DC oscillations found in circuits (<1 Hz) through the extremely high frequency oscillations typical of gamma radiation (>10
19
Hz).

The articles in this category present methods that are useful in the optical characterization of materials. The preceding discussion illustrates how spectroscopy permeates the entire encyclopedia—called upon where appropriate to specific materials studies. Spectroscopy, as a general category of techniques, will certainly remain central to the characterization of materials as materials science continues its advance.
Resonance Methods
Authors: Fultz Brent
Published: October 2003

This chapter shows how nuclear and electron resonance spectroscopies can help solve problems in materials science. The concept of a probe, located centrally within a material, is common to all resonance spectroscopy techniques. For example, the nucleus serves as the probe in nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), and Mössbauer spectrometry, while a paramagnetic atom (i.e., one containing unpaired electrons) often serves as a probe in electron spin resonance (ESR). Sometimes the interest is in measuring the total numbers of probes within a material, or the concentration profiles of probe nuclei as in the case for basic NMR imaging. More typically, details of the measured energy spectra are of interest. The spectra provide the energies of photons that are absorbed by the probe, and these are affected by the electronic and/or nuclear environment in the neighborhood of the probe. It is often a challenge to relate this local electronic information to larger features of the structure of materials.

The articles in this category describe how local electronic and magnetic structure can be studied with resonance techniques.
Electron Paramagnetic Resonance Spectroscopy
Authors: Eaton Sandra S. , Eaton Gareth R.
Published: October 2003

Electron paramagnetic resonance (EPR) spectroscopy, also called electron spin resonance (ESR) or electron magnetic resonance (EMR), measures the absorption of electromagnetic energy by a paramagnetic center with one or more unpaired electrons. In the presence of a magnetic field, the degeneracy of the electron spin energy levels is removed and transitions between the energy levels can be caused to occur by supplying energy. When the energy of the microwave photons equals the separation between the energy levels of the unpaired electrons, there is absorption of energy by the sample and the system is said to be at “resonance”. Typically the experiment is performed with magnetic fields such that the energies are in the microwave region. Hyperfine splitting of the signal occurs due to interaction with nuclear spins and can therefore be used to identify the number and types of nuclear spins in proximity to the paramagnetic center.

The information content of EPR arises from the ability to detect a signal and from characteristics of the signal, including integrated intensity, hyperfine splitting by nuclear spins,gvalue, line shape, and electron spin relaxation time. The characteristics of the signal may depend on environmental factors, including temperature, pressure, solvent, and other chemical species. Various types of EPR experiments can optimize information concerning these observables. Some commonly asked materials science questions that one might seek to answer based on these observables and some corresponding experimental design considerations are listed. Some general information and practical considerations are given in this article.

Whenever unpaired electrons are involved, EPR is potentially the best physical technique for studying the system. Historically, the majority of applications of EPR have been to the study of organic free radicals and transition metal complexes. Today, these applications continue, but in the context of biological systems, where the organic radicals are naturally occurring radicals, spin labels, and spin‐trapped radicals, and the transition metals are in metalloproteins. Applications to the study of materials are extensive, but deserve more attention than they have had in the past. Recent studies include the use of EPR to monitor the age of archeological artifacts, characterize semiconductors and superconductors, measure the spatial distribution of radicals in processed polymers, monitor photochemical degradation of paints, and characterize the molecular structure of glasses. In this article enough information is provided so that a potential user can determine whether EPR is likely to be informative for a particular type of sample, and which type of EPR experiment would most likely be useful.