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P Pfeifer

Publications and source records attributed to P Pfeifer.

18 recordsLinked to original sources
PubMed2000

Nonstandard roughness of terraced surfaces

We present a class of surfaces which are simultaneously flat and rough over the same range of lengths. They are self-affine, have well-defined roughness exponents, and consist of terraces of all sizes. The coexistence of flat and rough makes them respond to different external interactions with variable roughness. We demonstrate this for optical scattering (including x rays), two wetting situations, diffusion currents, and catalysis. A terraced Cu surface is a "self-assembled" experimental example, and designs for nano- and micromachined examples are presented.

Journal Article↗
PubMed1998

Renal lesions in Von Hippel-Lindau disease: the benign, the malignant, the unknown.

OBJECTIVES: To describe the features and treatment of renal lesions in von Hippel-Lindau disease (VHL) from a series of patients, to highlight important issues in the management of these lesions. MATERIALS AND METHODS: We performed a retrospective study in 7 patients with VHL who underwent surgery for renal lesions between January 1990 and July 1996. The initial evaluation consisted of an abdominal CT scan and renal arteriography. RESULTS: The mean age of patients at the time of discovery was 38 (+/- 12.01 years). All cases were of type 1. Radiology assessment underestimated the gravity of the lesions in 5 patients. In all patients, unilateral surgery was performed with the kidney being conserved in 4 cases. Of the 44 lesions removed, 23 had signs of progressiveness (atypical or malignant cyst, renal cell carcinoma), most of the cancers were of low grade. 84% of the lesions did not exceed 3 cm and 48% were </=1 cm. During follow-up (42 months), 2 patients relapsed. CONCLUSION: The clinical and pathological features of renal lesions in VHL require strict and early follow-up (from the age of 15). Only under these circumstances should primary conservative surgery be performed, however, recurrences are frequent. This conservative approach remains to be validated by multicentric prospective studies.

Adult↗
PubMed1997

[The Indiana pouch: a technic for simple continent urinary diversion].

OBJECTIVE: Description of the Indiana pouch, a continent urinary diversion after cystectomy for urogenital tumours, and for the sequelae of neurogenic and traumatic bladders. MATERIAL AND METHOD: This was a retrospective study of 16 patients undergoing, between June 1991 and March 1995, cutaneous urinary diversion by ileocaecal graft, detubularized in the colonic segment, with continence ensured by the ileocaecal valve. The postoperative follow-up (4 to 36 months) was performed at 3, 6 and 12 months (abdominal ultrasonography alternating with abdominopelvic CT scan), then annually (CT scan). Finally, a urodynamic assessment was performed in 7 patients. RESULTS: No early complications related to the reservoir were observed. Late complications of the diversion were related to the uretero-colonic anastomosis with 3 dilated renal subunits. Continence was achieved in 12 out of 15 patients, while one patient finally refused self-catheterization. In the patients in whom a urodynamic assessment was performed, the mean capacity of the reservoir was 671.4 +/- 273.9 mL for a filling pressure of between 3.7 +/- 1.6 and 11 +/- 2.5 cm H2O and an ileocaecal valve closure pressure of 97.9 +/- 117.1 cm H2O (full reservoir). CONCLUSION: The Indiana pouch is a useful urinary diversion as it is simple to perform and is associated with a low revision rate, while ensuring low-pressure continence.

Abdomen↗
PubMed1994

[The role of ultrasound-guided trans-rectal puncture in the treatment of prostatic abscess].

Prostatic abscess is a rare complication of urinary tract infection, whose symptoms and signs are not often specific. Prostatic abscess can now be easily diagnosed by transrectal ultrasonography. The authors report six cases of prostatic abscess diagnosed by ultrasonography. These abscess were successfully drained by ultrasound-guided transrectal aspiration, which may constitute a useful solution, as the classical treatments to date consist of transurethral resection or rectotomy.

Abscess↗
PubMed1992

Documentation of care in an oncology outpatient setting.

Finding time to perform thorough documentation in a busy oncology outpatient setting is an increasingly difficult task. This article describes the development of a new documentation system designed for an oncology outpatient unit. The system consists of a set of documentation tools that are specific for the type of patient visit, an initial assessment form, and guidelines for using the forms. The system was developed to reduce the amount of nursing time spent on documentation and to improve the quality of the documentation. Evaluation of the system indicated that the forms decreased charting time by 50%. Suggestions for modifying and revising the tools are included. This system could be adapted for use in any ambulatory oncology setting.

Documentation↗
PubMed1990

Microbial growth patterns described by fractal geometry.

Fractal geometry has made important contributions to understanding the growth of inorganic systems in such processes as aggregation, cluster formation, and dendritic growth. In biology, fractal geometry was previously applied to describe, for instance, the branching system in the lung airways and the backbone structure of proteins as well as their surface irregularity. This investigation applies the fractal concept to the growth patterns of two microbial species, Streptomyces griseus and Ashbya gossypii. It is a first example showing fractal aggregates in biological systems, with a cell as the smallest aggregating unit and the colony as an aggregate. We find that the global structure of sufficiently branched mycelia can be described by a fractal dimension, D, which increases during growth up to 1.5. D is therefore a new growth parameter. Two different box-counting methods (one applied to the whole mass of the mycelium and the other applied to the surface of the system) enable us to evaluate fractal dimensions for the aggregates in this analysis in the region of D = 1.3 to 2. Comparison of both box-counting methods shows that the mycelial structure changes during growth from a mass fractal to a surface fractal.

Fungi↗
PubMed1981

Steroid profiles of healthy individuals.

Urine steroid profiles of healthy individuals can be divided into two groups according to greatly different excretion rates of dehydroepiandrosterone (DHEA). About 80% of the population show an excretion of DHEA in urine of just above the detection limit or less of the main androgens androsterone (A) and etiocholanolone (E). This excretion is only enhanced in psychological stress situations. The remaining 20% excrete DHEA in roughly equal amounts as A and E. While the relation of excreted steroids is rather constant, the absolute amounts may vary greatly. In contrast to the behaviour of all other steroids DHEA excretion is not in relation to other steroids. The group of "high DHEA" producing individuals in particular shows drastic changes in the excretion during a day: the DHEA excretion rapidly rises from morning until afternoon and then drops to rather low values in the resting period during the night. A recognizable DHEA production seems to be closely related to the waking period.

Adult↗
PubMed1980

[Contamination by use of Extrelut columns (author's transl)].

Extrelut columns commonly used to isolate metabolites from biological fluids often contain fatty acids, phthalates, alcohols and especially resin acids which occassionally cause great analytical problems. Therefore purification before use of Extrelut columns is strongly recommended.

Acids↗
PubMedDate not supplied

[Femoral anteversion: significance of clinical methods and imaging techniques in the diagnosis in children and adolescents].

In order to investigate the correlation between different methods of AV-determination and to assess their reliability, we compared the results of clinical and sonographic examination with computed tomography and magnetic resonance imaging in 21 children (41 hips) preoperatively. The mean anteversion angles obtained by computed tomography (34.0 degrees +/- 13.7 degrees) appeared larger than the clinical (27.7 degrees +/- 8.5 degrees), sonographic (25.6 degrees +/- 8.0 degrees) and MRI-values (23.2 degrees +/- 12.8 degrees), which can be explained by the different measurement techniques. The inter-rater as well as intra-rater reliability was high in MRI (Pearson's correlation coefficient r = 0.97 and r = 0.97) and CT (r = 0.99 and r = 0.96) but slightly less in sonography (r = 0.88 and r = 0.88) and clinical investigation (r = 0.47 and r = 0.77). For routine use in screening of femoral anteversion clinical and sonographic methods are sufficiently accurate. But in determining the exact amount of torsion preoperatively and in planning of rotation osteotomies in children MRI and CT determination are superior. As magnetic resonance imaging requires no radiation dosage, shows non-ossified cartilaginous structures and proved its high reliability, it could replace other techniques in the future for that purpose.

Adolescent↗