PubMed Health⌕ Search

Biomedical subjects

M F Appel

Publications and source records attributed to M F Appel.

At least 19 recordsLinked to original sources
PubMed2001

Selective ultra-trace detection of NO and NO2 in complex gas mixtures using broad-bandwidth REMPI mass spectrometry.

In this paper we demonstrate the feasibility of ultra-trace resonance enhanced multiphoton ionization (REMPI) detection employing a small broad-bandwidth solid state laser system. The results reported here are compared with measurements carried out with a conventional excimer pumped dye laser combination. Mass selected broad-bandwidth REMPI spectra for the environmentally relevant nitrogen oxides NO and NO2 are presented. Tunable broad-bandwidth laser radiation with a spectral resolution of > 10 cm(-1) in the wavelength range 560-400 nm was employed for the detection of NO2. For NO detection, the range 230-224 nm was covered. Laser radiation was generated using an optical parametric oscillator pumped by an unseeded Nd:YAG laser. A mobile time-of-flight mass spectrometer equipped with an atmospheric pressure laser ionization source allowed for mass selective parent ion detection at m/z 30 for NO and m/z 46 for NO2. The limit of detection was 10 pptV for NO and 20 pptV for NO2. A selectivity of > 2000 for both compounds with respect to N2O5, organic nitrates and NO2 in the case of NO is reported. An improved laser system currently under construction is expected to provide detection limits below pptv mixing ratios for both nitrogen oxides in a 20 s integration interval.

Environmental Pollutants↗
PubMed2000

A REMPI method for the ultrasensitive detection of NO and NO2 using atmospheric pressure laser ionization mass spectrometry.

We report on the development of a quasi-simultaneous highly selective method for NO and NO2 detection at the ultratrace level. Atmospheric pressure laser ionization (APLI), recently introduced by our group, is used to detect both compounds at low parts per trillion by volume (pptv) mixing ratios. APLI is based on resonance-enhanced multiphoton ionization mass spectrometry. Two-color pump-probe experiments employing a single excimer pumped dye laser combination allow for the ultrasensitive measurement of NO and NO2 within a narrow range of maximum pumping efficiency of the laser dye Coumarin 120. NO is detected via excitation of the long-lived A 2sigma+ (nu' = 1) level at 215.36 nm and subsequently ionized with 308-nm radiation provided by the excimer pump laser. NO2 is ionized after double resonant excitation of the A2B1 and 3psigma manifolds in a (1 + 1' + 1(')) process using 431.65 + 308 nm. The selectivity of the NO measurement exceeds 2,000 with respect to NO2 and N2O5. For NO2, a selectivity of >3,000 with respect to N2O5 and organic nitrates is observed. The current APLI detection limit of NO and NO2 is 0.5 and 5 pptv, respectively, with a 20-s integration time.

Journal Article↗
PubMed1990

Percutaneous cholecystolithotomy. A minimally invasive alternative to cholecystectomy and to shock wave lithotripsy.

Recently introduced treatment alternatives for gallstones include peroral pharmacological chemolysis plus shock wave lithotripsy and percutaneous cholecystolithotomy. Herein we report on the treatment preferences of 23 patients with symptomatic gallstones and our initial experience with percutaneous cholecystolithotomy in 6 of these patients. All patients were rendered stone free after one procedure. Percutaneous cholecystolithotomy, which is applicable to all types of gallstones, is a safe, practical, low-morbidity alternative to cholecystectomy in selected patients.

Adult↗
PubMed1979

Epithelial polyps of the large bowel: a pathological and colonoscopic study.

Ninety patients who had epithelial polyps or carcinoma of the large bowel and underwent at least 2 colonscopic examinations were studied. The cases were divided into three groups: patients who ;ad only one polyp; those in whom more than one epithelial polyp were found and those who had adenocarcinoma of the large bowel and underwent follow-up colonoscopic examinations. The distribution of the polpys was plotted as to type and distribution in the colon. There seemed to be a trend for the polyp found in follow-up examinations to be located proximal to the splenic flexure. In this regard it was noted that the subsequently found polyps in group II were smaller than those removed on the initial colonoscopic examination. No relationship could be found between any histologic type of epithelial polyp and the presence of carcinoma.

Adenocarcinoma↗
PubMed1979

The small carcinoma of the large bowel.

Four small carcinomas (3, 6, 10, and 15 mm) of the large intestine have been examined for residual epithelial polyp; none was found. It is felt that these carcinomas arose from colonic mucosa without a preexisting visible epithelial precursor lesion; however, occasional glands having adenomatous change were seen near the edges of the carcinomas.

Adenocarcinoma↗
PubMed1978

Recurrent hemolytic anemia secondary to acessory spleens.

A patient with recurrent hereditary spherocytosis due to a hypertrophied accessory spleen is presented. In patients in whom splenectomy is performed for hematologic disease, accessory spleens must be sought and removed. Recurrence of the inital disease should prompt a search for accessory spleens.

Adult↗
PubMed1977

Nature and significance of colonic polyps.

The concept of inevitable premalignancy in all adenomatous polyps of the colon was challenged as early as 1958, and since that time much debate has centered about the malignant potential of adenomatous polyps of the colon. Current thinking indicates that the majority of colonic polyps fall into one of four categories: hyperplastic, villous adenoma, adenomatous, and villoglandular. Analysis of the present series of 387 colonic polyps removed endoscopically indicates that the villoglandular group has a notable malignant potential, and that the pure adenomatous polyp probably carries a minimal malignant threat. The present series does not challenge the accepted concept that hyperplastic polyps are of no malignant potential, and that villous adenomas are quite frequently malignant at the time of diagnosis.

Colonic Neoplasms↗
PubMed1976

Endoscopic removal of bleeding brunner gland adenoma.

A 36-year-old man had a major hematemesis because of a Brunner gland adenoma in the postbulbar portion of the duodenum. Three months later, the adenoma was successfully removed electively via endoscopic polypectomy. This is the first patient reported, to our knowledge, to have this technique for a bleeding Brunner gland adenoma. Endoscopic surgery is a relatively new development, and the technique of polypectomy has been used primarily in the colon. Surgery via upper gastrointestinal endoscopy promises to be as useful, although a somewhat different set of precautions applies.

Adenoma↗
PubMed1976

Arteriomesenteric duodenal compression syndrome: comparison of methods of treatment.

A group of 80 patients with arteriomesenteric duodenal compression syndrome was reviewed, 48 from the general population and 32 from the Hines, Illinois, VA Hospital. Differences in the patient populations are pointed out, as are differences in the therapeutic results. An additional series is reported. Duodenojejunostomy is a safe and effective operation for the majority of patients who require surgery for this condition, and patients are less likely to require further medical or surgical care than those who have section of the ligament of Treitz.

Adolescent↗
PubMed1976

Endoscopic removal of gastric and duodenal polyps.

As endoscopic surgery comes into its own, the applications of this modality are increasing. This is well illustrated by the use of endoscopic polypectomy in the colon, and more recently by endoscopic polypectomy in the stomach and duodenum. We can anticipate increased applicability of these technics as the experience widens and the margins of safety increase. The present series of six polypectomies from the stomach and duodenum confirms the applicability of endoscopic polypectomy for this portion of the gastrointestinal tract, attests to its safety, and indicates that these procedures can contribute materially to the care of patients with gastric or duodenal polyps. The real and potential problems are discussed.

Adenoma↗
PubMed1976

Pelvic lipomatosis.

A case report of pelvic lipomatosis in a woman is presented. This condition is a benign, apparently self-limited disease in which mature adipose tissue is deposited in the pelvis. The clinical presentation is discussed.

Adult↗
PubMed1976

The surgical and hematologic significance of accessory spleens.

The approximately 10 per cent incidence of accessory spleens in the general population is well documented, and accessory spleens often are not clinically significant. Trauma, torsion and, especially, hematologic diseases can affect an accessory spleen. A careful search should be made for accessory spleens, and they should be removed at the time of primary splenectomy so as to avoid a second operation later in life.

Adult↗
PubMed1975

Prosthetic fitting immediately after below-knee amputation.

Frequently surgical amputation of a lower extremity is required when gangrene develops as a result of peripheral vascular disease. This is particularly true in geriatric patients. A below-knee amputation, with refinements in the surgical procedure, and immediate rigid-cast prosthetic fitting are strongly advocated by our group. The progress of two patients treated in this manner is described. Preservation of the knee joint improves the amputee's prognosis for ambulation with a below-knee prosthesis. The rigid-cast dressing on the below-knee amputation reduces edema and postoperative pain, is of psychologic value to the patient, and permits him to stand at from one to two days postoperatively.

Aged↗
PubMed1975

Colonoscopy: Its principles and applications.

Fiberoptic colonoscopy has seen its early development in the past five years and in the last two to three years a rapidly expanding experience has developed. The use of this instrument has been documented abundantly both as a diagnostic tool and as a therapeutic tool, and its effectiveness in both areas is well established. The chief therapeutic use of the colonoscope is in the removal of polyps, and in this area the experience has been most gratifying in regard to the ability to remove most polyps and the low incidencs of complications.

Colon↗