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B C Dalton

Publications and source records attributed to B C Dalton.

8 recordsLinked to original sources
PubMed2004

Spin mixing and spin-current asymmetry measured by domain wall magnetoresistance.

By making a straightforward reformulation of the Levy-Zhang spin-mistracking model, we show that it is possible to extract the spin asymmetry of a current from measurements of domain wall resistance. Experiments on epitaxial films of L1(0) FePd are reported, showing that, while the micromagnetic structure of the sample is stable, the resistivity and the domain wall resistance change by a factor approximately 3 between helium and room temperature. The temperature dependence of the spin asymmetry of the current has been determined over a wide range in a single material.

Journal Article↗
PubMed1998

Strengthening immature teeth during and after apexification.

The purpose of this study was to evaluate the strengthening effect of an internal resin bonding technique. One hundred central incisors were endodontically treated and divided equally into five groups. Group 1, without any cervical preparation and with access repaired with bonded resin, served as the positive control. Teeth in groups 2 to 5 were cervically prepared to simulate the thin dentinal wall of immature teeth, and obturation material was removed to 3 mm below the cementoenamel junction (CEJ). In group 2, the negative control, the access was restored with bonded composite to the level of the CEJ. In group 3, access was restored with composite resin 3 mm apical to the CEJ using a clear post system. Group 4 was treated similarly to group 3, but an opaque post replaced the clear post. Group 5 was treated like group 3, after which a metal post was cemented into the channel left after removal of the clear post. All teeth were subjected to compression testing and the force required to fracture the teeth cervically was recorded for each group and the Kruskal-Wallis analysis performed to detect intergroup differences. All of the bonded resin techniques significantly strengthened the teeth against fracture, compared with the negative control group (p < 0.05). None of the experimental groups (3-5) were significantly different from the positive control group.

Composite Resins↗
PubMed1998

Bacterial reduction with nickel-titanium rotary instrumentation.

The purpose of this study was to compare intracanal bacterial reduction on teeth instrumented with 0.04 tapered nickel-titanium (NiTi) rotary instrumentation to bacterial reduction when using a stainless-steel K-file step-back technique using sterile saline irrigation. Forty-eight patients with apical periodontitis were randomly assigned treatment type. The canals were sampled before, during, and after instrumentation. The samples were incubated anaerobically for 7 days at 37 degrees C, colony-forming unit numbers calculated, and a log transformation performed to normalize the counts. Teeth exhibiting apical periodontitis were uniformly infected, whereas vital control teeth were not. A similar and uniform reduction occurred with progressive filing, regardless of technique (p < 0.0001). There was no detectable difference in colony-forming unit count after NiTi rotary or stainless-steel hand instrumentation (p = 0.42). Neither technique could predictably render canals free of bacteria. The results of this study indicate NiTi rotary and stainless-steel hand K-file step-back instrumentation techniques were not significantly different in their ability to reduce intracanal bacteria.

Analysis of Variance↗
PubMed1978

The effect of hemodilution with albumin or Ringer's lactate on water balance and blood use in open-heart surgery.

To determine the effect of intraoperative albumin administration on blood use, water balance, and postoperative clinical course, we studied two groups of adult cardiac surgical patients. Group I (30 patients) received 25 gm of albumin during withdrawal of 2 units of blood prior to cardiopulmonary bypass (CPB) and 50 gm of albumin in the oxygenator prime. Group II (32 patients) received no albumin prior to the end of CPB. No difference in clinical course could be identified, nor was there a significant difference in blood use. Group I patients had lower hematocrit values intraoperatively from the time of blood withdrawal until the conclusion of operation. Coronary artery bypass operations were associated with greater positive water balance than were heat valve operations. Forty-three percent of the patients having coronary artery bypass grafting had a positive water balance greater than 5 liters, whereas 50% of those undergoing valve procedures had a balance less than 3 liters. We conclude that the principal effect of withholding albumin under these circumstances is to increase net positive water balance. The greater positive water balance does not appear to be detrimental.

Adult↗
PubMed1975

Localization of tissue plasminogen activator in relation to morphologic changes in human saphenous veins used as coronary artery bypass autografts.

Employing the histochemical fibrin slide technique, we studied the localization of fibrinolytically active sites in relation to morphologic changes in saphenous veins used as coronary artery bypass autografts. Of veins from 100 patients undergoing surgery for coronary heart disease, 63 samples revealed well-demarcated intimal fibrinolytic activity. Distinct foci of lysis were present in the media and adventitia of all vein samples corresponding to the distribution of the vasa vasorum. Graft specimens obtained by autopsy from 13 patients surviving from 30 minutes to 13 days revealed considerable intimal damage with loss of fibrinolytic activity. Medial fibrinolytic activity disappeared early concomitant with disorganization of the medial muscle fibers, followed by necrosis, atrophy and fibrous transformation of the muscular structures. Adventitial activity disappeared later. One reoperation sample obtained after 8 weeks in situ showed moderate proliferative intimal fibrosis without an apparent neo-intima and without fibrinolytic activity, and one section showed evidence of valve cusp fibrosis, while most of the media had been replaced by fibrous tissue. Numerous foci of "medial" -adventitial fibrinolytic activity indicated presence of vascular structures in the venous wall. The fibrin slide technique is a convenient tool for studying the process of revascularization.

Atrophy↗