Charge migration in DNA: ion-gated transport.

Electron hole (radical cation) migration in DNA, where the quantum transport of an injected charge is gated in a correlated manner by the thermal motions of the hydrated counterions, is described here. Classical molecular dynamics simulations in conjunction with large-scale first-principles electronic structure calculations reveal that different counterion configurations lead to formation of states characterized by varying spatial distributions and degrees of charge localization. Stochastic dynamic fluctuations between such ionic configurations can induce correlated changes in the spatial distribution of the hole, with concomitant transport along the DNA double helix. Comparative ultraviolet light-induced cleavage experiments on native B DNA oligomers and on ones modified to contain counterion (Na(+))-starved bridges between damage-susceptible hole-trapping sites called GG steps show in the latter a reduction in damage at the distal step. This reduction indicates a reduced mobility of the hole across the modified bridge as predicted theoretically.

Structure and magnetism of neutral and anionic palladium clusters.

The properties of neutral and anionic Pd(N) clusters were investigated with spin-density-functional calculations. The ground-state structures are three dimensional for N>3 and they are magnetic with a spin triplet for 2 < or = N < or = 7 and a spin nonet for N = 13 neutral clusters. Structural and spin isomers were determined and an anomalous increase of the magnetic moment with temperature is predicted for a Pd7 ensemble. Vertical electron detachment and ionization energies were calculated and the former agrees well with measured values for Pd(-)(N).

Medically useful criteria for analytic performance of laboratory tests.

To establish medically useful guidelines for analytic precision of commonly used clinical laboratory procedures, the authors conducted a mail survey of physicians selected randomly from national lists of specialists. They were asked to review, briefly, outlined clinical problems and select the change in test results that would alter their diagnosis or treatment or prompt further assessment of the patient's condition. The responses were used to calculate goals for laboratory precision that are sufficient to meet the present requirements of the average physician. The medically useful limits were compared with existing performance of laboratories as reported in national proficiency surveys and regional quality control programs. Almost all the common laboratory procedures they studied are being assayed at a precision level adequate for the perceived needs. The authors suggest that, for the more common constituents, further progress in clinical laboratory testing will depend on factors other than the improvement of analytic precision.

Planning and instituting new tests in the clinical laboratory.

The laboratory director will eventually face the problem of introducing a new test method. A whole spectrum of decisions must be made depending on the degree of novelty and complexity of the new test. The statistical comparison studies discussed in this article are generally applicable for all tests reported in a quantitative manner.

Long-term stability of a stabilized liquid quality-control serum.

To evaluate the long-term stability of a new liquid quality-control serum ("Decision", Beckman Instruments, Inc.) stabilized with ethylene glycol (330 mL/L), we analyzed it for 22 commonly measured analytes during storage at 2--8 degrees C for 24 days or -15 to -20 degrees C for 55 weeks. Three separate laboratories replicated the analyses, using various analytical methodologies. The data were subjected to linear regression analysis, regressing concentration on time. Analytes were considered unstable when the linear regression coefficient was unequal to zero with 95% or greater probability in all three laboratories. By this criterion all of the analytes were stable for at least 24 days when the control serum was stored at refrigerator temperature and for at least 55 weeks at freezer temperature. We conclude this material is a satisfactory substitute for existing lyophilized quality-control materials and offers certain advantages: stability, vial-to-vial uniformity, decreased waste, and eliminated reconstitution.

You can draw blood from the "IV arm" below the intravenous needle if you put a tourniquet in between.

The authors performed a comparative study of the values of 18 serum constituents of blood specimens taken simultaneously from the arm into which an intravenous solution was flowing, using a site distal to the intravenous needle, and from the other arm. Subjects of the study were 15 patients at the Norwalk Hospital. Statistical analysis showed no clinically significant difference between the levels in the two arms except for elevation of glucose in the "iv arm" when the intravenous solution contained glucose.

The medical usefulness of Stat tests.

Although Stat tests are one of the most important features of clinical laboratory performance, the indexed literature is devoid of significant discussion of the subject. The authors, undertook a study by querying hospital laboratories about their current practices and received 38 useable answers dealing with the types of tests done on an urgent basis, the turn-around time for reports, the limitations on ordering, the use of special Stat laboratories and instruments, and decisions regarding priorities.

Elevated bone marrow acid phosphatase: the problem of false positives.

Bone marrow acid phosphatase values were studied in 24 patients (12 men and 12 women) selected at random, including 6 at autopsy. False positive results were noted in 8 of the 18 patients who were alive and in all 6 patients studied at autopsy. The possible causes for these falsely elevated results are discussed. The bone marrow acid phosphatase is a test of poor specificity and should not be used as the sole test on which vital decisions regarding management of the patient are based.

Performance of "kits" used for clinical chemical analysis of GOT (aspartate aminotransferase).

Forty-three kits for clinical chemical analysis of GOT (aspartate aminotransferase) were evaluated. The reference method was the kinetic method performed on the Abott ABA-100 Bichromatic Analyzer. Specific data are tabulated for each kit and include ease and speed of testing and performance data. Most kits failed to provide completely adequate labelling information. Reproducibility CV for the kits varied widely (4.20 to 21.26 for the normal pool and 1.57 to 20.51 for the high pool). Many kits gave significant numbers of false positive and false negative results on patient samples. There is a need for manufacturers to either derive their own normal ranges or to establish exact equivalency values with the method used to establish the normal values. No difference was demonstrated between performance by two skilled technologists. However, we did detect lot-to-lot variation and differences in performance between narrow bandpass and wide bandpass spectrophotometers.