Medical devices, health care, and consensus standards.

ASTM Committee F04 on Medical and Surgical Materials and Devices has been creating standards for this field since 1962. Dr. Jack Lemons provides a quick overview of the past, present, and future of this committee.     

Microvascular thermal equilibration in rat cremaster muscle

A new experimental approach was developed to obtain the first direct measurements of the axial countercurrent thermal equilibration in a microvascular tissue preparation using high resolution infrared thermography. Detailed surface temperature measurements were obtained for an exteriorized rat cremaster muscle in which pharmacological vasoactive agents were used to change the local blood flow Peclet number from 1 to 14 in the feeding artery. Under normal conditions, only the 1A arteries (> 70 microns diameter) showed thermal nonequilibration with the surrounding tissue. The theoretical model developed by Zhu and Weinbaum (28) for a two-dimensional tissue preparation with arbitrarily embedded countercurrent vessels was modified to include axial conduction and the presence of the supporting glass slide. This modified model was used to interpret the experimental results and to relate the surface temperature profiles to the bulk temperature profiles in the countercurrent artery and vein and the local average tissue temperature in the cross-sectional plane. Surface temperature profiles transverse to the vessel axis are shown to depend significantly on the tissue inlet temperature. The eigenfunction for the axial thermal equilibration depends primarily on the blood flow Peclet number and the environmental convective coefficient. The theoretical results predict that when rho(ar)*Pe is less than 1 mm (the range in our experiments), axial conduction is the dominant mode of axial thermal equilibration. For 1 < rho(ar)*PE < 3 mm, countercurrent blood flow becomes comparable to axial conduction, whereas, when rho(ar)*Pe > 3 mm, countercurrent blood flow is the dominant mode of axial thermal equilibration. Therefore, for rho(ar)*Pe > 3 mm the axial equilibration length is proportional to the blood flow Peclet number, as predicted previously by Zhu and Weinbaum in a study in which axial conduction was neglected. It also is shown that the axial decay of the tissue temperature at low perfusion rates can be described by a simple one-dimensional Weinbaum-Jiji equation with a newly derived conduction shape factor.     

Evaluation of consecutively placed unloaded root-form and plate-form implants in adult Macaca mulatta monkeys

The present paper describes 18 consecutively-treated non-human primates (Macaca mulatta) as part of a balanced block design study of 36 animals to examine osseointegration in root- and plate-form implants prepared by atraumatic preparation of bone. Clinical measurements around selected teeth and digital radiology were utilized to monitor periodontal disease and bone deposition around the unloaded implants. Once a month scaling procedures were utilized as a means of preventing further advance of periodontal disease. Results indicate that once-monthly regimen of scaling and root planing can prevent attachment loss of natural teeth and will not interfere with the healing of either type of implant; once-monthly scalings produce significant reduction in redness (P < .05) and reduced probing depths (P = .01). A second finding is that both root and blade implants show radiographic evidence of osseointegration in this primate model. The quantitative analysis demonstrates bone gain is not stabilized until 6 months after healing. The data may indicate that occlusal loading of mandibular implants at 3 months may be premature.     

PMOS transistors fabricated in large-area laser-crystallised Si on silica

PMOS transistors have been fabricated in device-worthy Si which was achieved by large-area laser-crystallisation of Si on silica. The crystallised Si contains few large-angle grain boundaries due to laser-beam inhomogeneity but exhibits subgrain boundaries aligned along the laser track. Cracking of the Si, a result of the mismatch of the thermal expansion coefficients of Si and silica, has been substantially reduced by removing only a stripped region of the SiO2 encapsulation layer for transistor fabrication. A high yield and good electrical characteristics of the devices were obtained.     

Metabolic balance studies in premature infants

Many investigators over the past three decades have successfully conducted traditional metabolic balance studies in efforts to determine the retention rates of key nutrients important to the optimal growth of preterm infants. Differences in methodologies discussed in this review may explain the inconsistent results of balance studies reported for some nutrients, particularly calcium. These methodologic differences include (1) variability in nutrient intake and nutritional course prior to the balance period, (2) differences in the method of stool collection (with and without markers), (3) use of single versus repeated balance periods, and (4) different durations of balance periods. The data presented here suggest that the variability of net fat absorptions among VLBW infants was decreased when an acclimation period of nutrient intake supportive of growth was provided prior to a metabolic balance study. In addition, the use of markers affected the estimates of net calcium absorption but not fat absorption. Additional factors that may influence net calcium absorption and methods for the estimation of calcium absorption in VLBW infants warrant further investigation. This review describes the methods of specimen collection for metabolic balance studies in VLBW preterm infants that demonstrated reproducible data. The recent application of stable isotope methodology to metabolic balance studies can be extremely advantageous in identifying the rates of nutrient absorption versus endogenous secretion in the GI tract.     

Nanostructured ceramics for biomedical implants

Recent progress in the synthesis, characterization, and biological compatibility of nanostructured ceramics for biomedical implants is reviewed. A major goal is to develop ceramic coating technology that can reduce the friction and wear in mating total joint replacement components, thus contributing to their significantly improved function and longer life span. Particular attention is focused on the enhancement of mechanical properties such as hardness, toughness, and friction coefficient and on the bioactivity as they pertain to the nanostructure of the material. The development of three nanostructured implant coatings is discussed: diamond, hydroxyapatite, and functionally graded metalloceramics based on the Cr-Ti-N ternary system. Nanostructured diamond produced by chemical vapor deposition (CVD) techniques and composed of nano-size diamond grains have particular promise because of the combination of ultrahigh hardness, improved toughness over conventional microcrystalline diamond, low friction, and good adhesion to titanium alloys. Nanostructured processing applied to hydroxyapatite coatings is used to achieve the desired mechanical characteristics and enhanced surface reactivity and has been found to increase osteoblast adhesion, proliferation, and mineralization. Finally, nanostructured metalloceramic coatings provide continuous variation from a nanocrystalline metallic bond at the interface to the hard ceramic bond on the surface and have the ability to overcome adhesion problems associated with ceramic hard coatings on metallic substrates.     

CTNS mutations in an American-based population of cystinosis patients

Nephropathic cystinosis is an autosomal recessive lysosomal storage disease characterized by renal failure at 10 years of age and other systemic complications. The gene for cystinosis, CTNS, has 12 exons. Its 2.6-kb mRNA codes for a 367-amino-acid putative cystine transporter with seven transmembrane domains. Previously reported mutations include a 65-kb "European" deletion involving marker D17S829 and 11 small mutations. Mutation analysis of 108 American-based nephropathic cystinosis patients revealed that 48 patients (44%) were homozygous for the 65-kb deletion, 2 had a smaller major deletion, 11 were homozygous and 3 were heterozygous for 753G-->A (W138X), and 24 had 21 other mutations. In 20 patients (19%), no mutations were found. Of 82 alleles bearing the 65-kb deletion, 38 derived from Germany, 28 from the British Isles, and 4 from Iceland. Eighteen new mutations were identified, including the first reported missense mutations, two in-frame deletions, and mutations in patients of African American, Mexican, and Indian ancestry. CTNS mutations are spread throughout the leader sequence, transmembrane, and nontransmembrane regions. According to a cystinosis clinical severity score, homozygotes for the 65-kb deletion and for W138X have average disease, whereas mutations involving the first amino acids prior to transmembrane domains are associated with mild disease. By northern blot analysis, CTNS was not expressed in patients homozygous for the 65-kb deletion but was expressed in all 15 other patients tested. These data demonstrate the origins of CTNS mutations in America and provide a basis for possible molecular diagnosis in this population.     

Chronic localized osteomyelitis caused by atypical infection with Blastomyces dermatitidis in a dog

A 4-year-old male Golden Retriever was evaluated because of chronic non-weight-bearing lameness of the right hind limb associated with penetrating tarsal wounds. Arthritis of the tarsal joint and osteomyelitis of the talus were initially evident. Tarsal arthrodesis was performed 7 months after initial injury, but the lameness persisted. Ten months later, blastomycosis was diagnosed on the basis of results of histologic examination of bone biopsy specimens and serologic tests. No other site of involvement was detected. The limb was amputated, and Blastomyces dermatitidis was isolated from the affected bone. Adjuvant antifungal treatment was not given. Ten months after amputation, the dog was in good health, and the antibody titer for B dermatitidis was low, indicating resolution of the infection. Localized bone infection with B dermatitidis is rare in dogs. In this dog, it was believed that blastomycosis was contracted through direct inoculation of the organism, because the lesion was associated with puncture wounds and other sites of involvement were not found.     

The relative efficacy of four methods of human milk expression

In view of the current trend toward increased breast-feeding, both of normal term infants as well as sick or premature infants, a successful means for milk expression in order to establish and maintain lactation is of major importance to the mother. The present study was designed to evaluate four methods of milk expression, measuring the amount as well s the fat content of milk expressed by each method during a 10-min period. The four methods included the Egnell electric pump, the Loyd B pump, the Evenflo system, and manual expression. The electric pump enabled mothers to express significantly more milk with adequate fat content during the expression period than any of the other methods tested. No significant differences were found between the other three methods. The Egnell or similar electric pump may be a preferred method for milk expression for some mothers, particularly those anticipating a prolonged need for pumping.     

Examining the Effect of the Transformational Leader on Software Quality

Developing and maintaining quality software is paramount in the information-intensive society. A myriad of concepts, tools and techniques exist that can be employed to improve the quality of software and at the same time increase developmental efficiencies. Approaches used by many software development units include: Capability Maturity Model (CMM), Total Quality Management (TQM), and ISO 9000-3. Implementation of these approaches without appropriate management oversight does not guarantee success. This study examines the role of the manager vis-à-vis leadership style with software quality. Data collected using a questionnaire administered to members of the American Society for Quality (ASQ) - Software Division, suggest that the Transformational leadership style of the manager has a significant positive relationship with the quality of the software developed.