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P D Hatton

Publications and source records attributed to P D Hatton.

9 recordsLinked to original sources
PubMed2005

Resonant soft X-ray diffraction - in extremis.

The use of softer-energy X-rays produced by synchrotron radiation for diffraction is an area of current interest. In this paper, experiments exploiting resonant scattering at the L absorption edges of 3d transition metal elements are reported. Such energies, typically 500-1000 eV, are at the extreme limit of soft X-ray diffraction where absorption effects are so severe that the sample and diffractometer must be placed in a windowless high-vacuum vessel. In addition, the Ewald sphere is so small as to likely contain, at most, only a single Bragg reflection. Advantages of using such radiation for the study of weak diffraction effects such as anomalous scattering, charge ordering, magnetic diffraction and orbital ordering are reported.

Computer Simulation↗
PubMed2003

Direct observation of orbital ordering in La0.5Sr1.5MnO4 using soft x-ray diffraction.

We report the first direct resonant soft x-ray scattering observations of orbital ordering. We have studied the low temperature phase of La0.5Sr1.5MnO4, a compound that displays charge and orbital ordering. Previous claims of orbital ordering in such materials have relied on observations at the manganese K edge. These claims have been questioned in several theoretical studies. Instead we have employed resonant soft x-ray scattering at the manganese L(III) and L(II) edges which probes the orbital ordering directly. Energy scans at constant wave vector are compared to theoretical predictions and suggest that at all temperatures there are two separate contributions to the scattering: direct orbital ordering and strong cooperative Jahn-Teller distortions of the Mn3+ ions.

Journal Article↗
PubMed2003

Soft X-ray resonant magnetic diffraction.

We have conducted the first soft x-ray diffraction experiments from a bulk single crystal, studying the bilayer manganite La2-2xSr1+2xMn2O7 with x=0.475 in which we were able to access the (002) Bragg reflection using soft x rays. The Bragg reflection displays a strong resonant enhancement at the L(III) and L(II) manganese absorption edges. We demonstrate that the resonant enhancement of the magnetic diffraction of the (001) is extremely large, indeed so large that it exceeds that of the nonresonant Bragg diffraction. Resonant soft x-ray scattering of 3d transition metal oxides is the only technique for the atomic selective measurement of spin, charge, and orbital correlations in materials, such as high temperature superconductors, colossal magnetoresistance manganites, and charge stripe nickelates.

Journal Article↗
PubMed1989

Transsternal radical thymectomy for myasthenia gravis: a 15-year review.

Thymectomy is an accepted therapeutic modality for patients with myasthenia gravis. The selection of patients for operation and the surgical approach are controversial. We reviewed 52 patients (aged 18 months to 82 years; mean age, 34 years) treated with transsternal radical thymectomy between 1972 and 1987. Patients were symptomatically staged according to the modified Osserman classification. There was one hospital death and postoperative follow-up was obtained on 51 patients. Improvement after thymectomy was observed in 3 of 11 patients (27%) in Osserman stage I, 16 of 25 patients (64%) in Osserman stage IIA, and 13 of 15 patients (86%) in combined Osserman stages IIB, III, and IV. Preoperative Osserman stage, patient sex, and thymic histology correlated with postoperative clinical response. Transsternal radical thymectomy is effective therapy for myasthenia gravis. Sustained improvement is obtained in patients with moderate and advanced disease. The majority of patients with ocular disease do not benefit from operation.

Adult↗
PubMed1985

Calcified hematoma of the greater omentum in an F-15 fighter pilot.

A high performance aircraft test pilot who presented with acalculous cholecystitis was found to have a calcified omental hematoma adjacent to the gallbladder. Omental hematomas have not previously been linked to flight in high performance aircraft. Current prevailing hypotheses regarding etiologies of omental hematomas include rapid blood flow shifts and venous fragility. Forces encountered in high performance aircraft may increase the chance of omental hemorrhage.

Adult↗
PubMed1984

Survival following aggressive treatment of secondary aortocolonic fistula.

Secondary aortocolonic fistula is an uncommon complication of prosthetic aortic grafts; apparently there have been only two previously described long-term survivors. We describe a long-term survivor with this complication in which preoperative computed tomographic scanning and percutaneous abscess drainage allowed early diagnosis and intervention and contributed to optimal treatment and survival. Adherence to time-honored principles of abscess drainage and graft removal, followed by extra-anatomic bypass when indicated, are essential to successful treatment.

Abscess↗
PubMed1984

Surgical management of the failed Nissen fundoplication.

A significant percentage of surgery performed for complications of gastroesophageal reflux at a major medical center has been performed for problems related to prior surgery. Our patients who required remedial surgery fell into three categories. Those with recurrent reflux generally fared well. Patients with dysphagia, gastric stasis, or both presented difficult problems. The key to success for these patients lies in choosing the operation best suited to the anatomic and physiologic situation as defined by preoperative contrast studies, pH monitoring, endoscopy, and selective gastric emptying studies.

Adult↗
PubMed1984

Xeromammographic screening: is it helping?

We have reviewed our experience with xeromammography over a five-year period in a setting where there is no protocol for mammographic screening. Only 8.9% of breast carcinomas were found by xeromammography alone, a ratio substantially smaller than that found in large screening programs. While 80% of the occult carcinomas were localized, only 47% of women with palpable disease had localized tumors. It appears that screening mammography is underused, and that more localized tumors would be detected if more mammograms were ordered.

Adult↗