Discrepancies in normative data between Lunar and Hologic DXA systems

Many studies have shown the high correlation between Lunar and Hologic DXA bone mineral density (BMD) measurements despite differences in absolute calibration. However, in clinical practice, raw BMD values (in g/cm2) are not normally used for assessing skeletal status and fracture risk. Instead, the BMD values are expressed in terms of the number of standard deviations above or below the young normal value (commonly referred to as the T-score). If the normative populations of the various systems are consistent, the standard deviation scores should also be consistent. For this reason, the World Health Organization (WHO) recently established diagnostic criteria for osteoporosis based on T-scores and not BMD. However, few studies have compared the instruments in terms of their standard deviation scores. In this study, we used linear regression to compare T-scores in 83 women at L1-4 and 120 women at the femoral neck obtained on a Lunar DPX and a Hologic QDR-1000/W system. patient BMD and T-score measurements were highly correlated between the two systems (r > 0.95). No clinically significant difference in L1-4 T-scores was seen (less than 0.1 SD). However, linear regression analysis confirmed a systematic difference of 0.9 SD between the femoral neck T-scores. This discrepancy is caused by: (1) differences in the normal populations, and (2) differences in statistical models used to determine the young normal mean and standard deviation. In an attempt to correct the discrepancy, the female young normal mean and standard deviation were recalculated for the femoral neck using published epidemiological data from NHANES and existing DXA cross-calibration equations. The Hologic young normal value (mean +/- SD) was redefined as 0.85 +/- 0.11 g/cm2, while the Lunar value was redefined as 1.00 +/- 0.11 g/cm2. When the femoral neck T-scores for the study population were recalculated on the basis of these new values, the results were equivalent between manufactures, effectively eliminating the discrepancy. However, the revised values should be confirmed by additional measurements in young normal adults.     

Laminaria augmentation of midtrimester pregnancy termination by intramuscular prostaglandin 15 (S) 15-methyl F2 alpha

A group of 15 midtrimester gravid patients underwent intracervical laminaria tent insertion prior to repeated intramuscular injections of 250mu g of prostaglandin 15 (S) 15-methyl F2 alpha at two-hour intervals for elective termination of pregnancy. This group was compared with a previously reported group of 80 patients who had received identical treatment without laminaria insertion. A significant reduction in mean abortion time and an increased 24-hour abortion rate were observed with the addition of laminaria. There was a proportionate decrease in gastrointestinal side effects as well as a reduced need for analgesia in the laminaria group with no complications attributable to the laminaria insertion.     

Probability of malignant degeneration of ovarian tumors. Clinical study on the probability of malignant degeneration

More than 600 cases of ovarian tumors were analyzed for histological type, age of patient, bilateral occurrence, mobility and malignant degeneration in restant ovaries. Tumors of germinal epithelial origin show the highest incidence (24%) of malignant degeneration, tumors of germ cells the lowest (3,5%). Incidence of malignant degeneration increases in relation to the age of the patient from 2% (and under 30 years) to 36,5% (60-70 years). Each form of tumor has its typical age peak, which is about 20 years higher for carcinomas than for their benign counterpart. Bilateral ovarian tumors are malignant in 29%, one-sided only in 13%. Among freely movable ovarian tumors, only 6% enclose a malignant tumor, among adhaerent ones 34%. The examination of the prognosis of granulosacell-tumors, dysgerminomas and teratoblastomas is based on a larger material.     

Warranty periods for production lots based on fatigue-test data

A two-parameter Weibull model for failure time is assumed. An easily implemented method is developed for calculating, from information obtained from a possibly censored life test, an approximate warranty period before which the $\text{k}$th failure occurs in a production lot of given size with some small specified probability. The precision of the approximation is investigated and a numerical example applied to failure data is given.The procedure developed can also be used for obtaining lower prediction limits for ultimate strengths of composite structures in production lots of specified size and for certain models other than the Weibull.     

Cycle time distribution in circulating systems

The cycle time distribution (CTD) within closed, continuously circulating systems is defined and related to the residence time distributions of flow regions which make up such systems. Examples of the application of the CTD are noted and experimental methods for determining CTDs for various systems are summarized.     

Collisions and traffic violations of alcohol, cannabis and cocaine abuse clients before and after treatment

Prior research has shown that those with alcohol problems have significantly elevated rates of traffic events (i.e. traffic violations and collisions) than licensed drivers from the general population and that treatment is associated with reductions in alcohol-related collisions. However, very little research exists on traffic events and the impact of treatment for cannabis or cocaine clients. The objectives of this research are: (1) to determine whether clients in treatment for a primary problem of alcohol, cannabis or cocaine have significantly elevated rates of traffic events than a matched control group of licensed drivers; and (2) to assess whether a significant reduction in traffic events occurs after treatment for each client group compared to a control group. Driver records of patients admitted to substance abuse treatment in 1994 for a primary problem of alcohol (n = 117), cannabis (n = 80) or cocaine (n = 169) were accessed from the Ministry of Transportation for Ontario, Canada. A comparison group of 504 licensed drivers frequency matched by age, sex and place of residence, was also randomly selected. Data was collapsed into two 6-year time periods: 1988-1993 (i.e. before treatment) and 1995-2000 (i.e. after treatment). Six repeated measures analysis of variance tests were conducted where traffic violations and collisions of three treatment groups (i.e. alcohol, cannabis or cocaine) and a control group were compared before and after treatment. All three treatment groups had significantly more traffic violations than the control group and no significant interactions between time period and group membership were found. For collisions, there was a significant interaction between the alcohol and control groups and between the cocaine and control groups. The average number of collisions for the alcohol and cocaine groups decreased after completing treatment, whereas the number for the control group was stable over the same time periods. Neither the interaction term nor the between group effect was significant in the comparison of the cannabis and control groups. When rates of collisions were calculated based on the period that each driver had a valid license, the interaction term was still significant for the comparison of the alcohol and control groups but not for the cocaine and control groups. The results contribute to existing literature by demonstrating that cocaine and cannabis clients have a higher risk of traffic violations than matched controls and that reductions in collision risk was found after treatment for the alcohol and cocaine groups. More research is needed to better understand the reasons for the higher risk of traffic events and to determine reasons for declines.     

Constant-distance mode scanning potentiometry. 1. Visualization of calcium carbonate dissolution in aqueous solution

Constant-distance mode scanning potentiometry was established by integrating potentiometric microsensors as ion-selective scanning probes into a SECM setup that was equipped with a piezoelectric shear force-based tip-to-sample distance control. The combination of specially designed micrometer-sized potentiometric tips with an advanced system for tip positioning allowed simultaneous acquisition of both topographic and potentiometric information at solid/liquid interfaces with high spatial resolution. The performance of the approach was evaluated by applying Ca(2+)-selective constant-distance mode potentiometry to monitor the dissolution of calcium carbonate occurring either at the (104) surface of calcite crystals or in proximity to the more complex surface of cross sections of a calcium carbonate shell of Mya arenaria exposed to slightly acidic aqueous solutions. Micrometer-scale heterogeneities in the apparent calcium activity profiles have successfully been resolved for both samples.