The OKT3 Antibody Response Study: a multicentre study of human anti-mouse antibody (HAMA) production following OKT3 use in solid organ transplantation

Human anti-murine antibody titres following patient exposure to the monoclonal antibody Orthoclone OKT3 (muromonab-CD3) are determined by laboratories using diverse analytical methods which are not standardized and whose concordance is not established. A multicentre study group therefore compared testing for IgG anti-OKT3 antibody among seven laboratories. A set of 270 sera was obtained from 30 heart, 30 kidney and 30 liver transplant recipients with no previous exposure to OKT3 who were receiving OKT3 for induction immunosuppression. Sera were collected from each patient prior to and at 24 +/- 2 days and 31 +/- 2 days following initial OKT3 exposure. Identical aliquots of all 270 sera were tested for IgG anti-OKT3 antibody by each laboratory. In addition, the limit of detection of each laboratory's method was estimated by titration of an affinity-purified IgG anti-OKT3 reference material of known concentration. Anti-OKT3 antibody formation differed greatly among the three organ groups. Cardiac patients demonstrated the least sensitization and almost exclusively lower titres, while kidney recipients had more frequent and higher titre antibody formation. Liver recipients yielded the highest sensitization rate and the most frequent high titre sera. Importantly, the seven laboratories differed widely in the number of pretreatment sera reported as positive (ranging from 0% to 41% among laboratories), the number of post-OKT3 sera reported as positive (17-63%), the number of post-OKT3 samples with titre > or = 1000 (2-31%), and the number of patients sensitized 19-69%). Concordance among laboratories was highly variable, with interlaboratory agreement ranging from 38% to 83% on the sample titres assigned to 180 post-OKT3 sera. Many of the discordant results were consistent with differences in the limit of detection of the analytical methods, which ranged from 0.19 microgram/ml to > or = 15 micrograms/ml, a nearly 100-fold difference among laboratories. This study demonstrated the presence of both good concordance and significant discordance among laboratories in determining human anti-mouse antibody titres, and demonstrated that common titre categories (100, 1000, 10,000) were not equivalent among laboratories. The level of concordance among methods should be considered when comparing anti-OKT3 antibody results from different centres and their correlation with clinical events. Universal comparative testing, patterned after proficiency testing programmes, is needed to assess differences among laboratories and to bring uniformity and a sound interpretative basis to this field of testing.     

Effects of category prototypes on performance-rating accuracy.

Two studies examined whether the accessibility of performance prototypes influences performance appraisals. Pilot studies revealed students used performance prototypes when rating instructor performance. Study 1 manipulated the accessibility of these prototypes and the time delay of performance ratings. Results showed no effect of the prime on rating error and accuracy; however, discrimination accuracy decreased over time and recognition bias became more conservative. Study 2 manipulated prototype accessibility and type of rating stimuli (videotape vs. vignette). Rating accuracy and recall were higher for vignette than videotape stimuli, and only those participants exposed to the vignette exhibited priming effects. Results supported transfer-appropriate processing and implied that cognitive primes may have a stronger effect on performance ratings based on "paper-people" than videotaped stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heat and Fluid Flow in an Optical Switch Bubble

The Agilent all-optical bubble switch uses bubbles in an organic fluid index matched to a silica planar lightwave circuit. The bubble is created and sustained by heaters that are deposited on an attached silicon substrate. Testing of the bubble shows how heater power and ambient pressure affect bubble shape, size, and optical reflection characteristics. Heat and fluid flow in the bubble were modeled in 2D and 3D using the homogeneous bubble model in the Flow3D modeling software. Fluid condensing on the trench wall causes a dimple on the bubble and hence nonoptimum optical reflection. To aid understanding, the bubble, silica walls, and heaters were also modeled as a thermal resistance network. Because the pressure drop across the bubble wall is fixed, the bubble size is determined by P_res/DeltaT_t , where P_res is the heater power and DeltaT_t is the temperature difference between the bubble and the substrate. Heating the trench walls beyond the bubble temperature with heaters located underneath the trench wall will dry out the trench wall and give a stable optical reflection. As DeltaT_t approaches zero, a bubble is sustained without any heater power and with zero fluid flow. This "static" bubble provides for a very stable optical reflection     

Aging and memory for words and action events: Effects of item repetition and list length.

We were concerned with the effects of item repetition, list length, and class of item on free recall in elderly as compared with young adults. In Experiment 1, samples of young and elderly adults recalled a list of 27 words and a list of 27 action events (minitasks performed by the subjects). Some items were presented once and some twice. Although the younger subjects showed better recall on both types of lists, the older sample benefited from item repetition as much as did the younger sample. This finding was replicated in Experiment 2. A second finding in Experiment 2 was a significant aging effect in the recall of long but not of short lists of both words and action events. The absence of an Age?×?Repetition Effect interaction was ascribed to the strength nature of the repetition manipulation. The age effects in the recall of the long lists were attributed to possible deficits in retrieval proficiency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigation of the thermal, mechanical, and fracture properties of alumina-epoxy composites

A combination of dynamic shear rheology, thermomechanical analysis (TMA), scanning electron microscopy (SEM), Near-Edge X-ray Absorption Fine Structure (NEXAFS), and fracture toughness testing was utilized to characterize the thermal, mechanical, chemical, and fracture properties of alumina (α-Al₂O₃)-filled epoxy resins as a function of average filler size, size distribution, particle shape, loading, and epoxy crosslink density. In general the cured properties of the filled composites were robust. Small changes in particle size, shape, and size distribution had little impact on the final properties. Resin crosslink density and filler loading were the most critical variables, causing changes in all properties. However, most applications could likely tolerate small changes in these variables also. SEM and NEXAFS characterization of the fracture surfaces revealed that the fracture occurs at the filler interface and the interfacial epoxy composition is similar to the bulk resin, indicating a weak epoxy-alumina interaction. These results are critical for implementation of particulate-filled polymer composites in practical applications because relaxed material specifications and handling procedures can be incorporated in production environments to improve efficiency.