Accelerated convergence method for fast Fourier transform simulation of coupled cavities.

Fast Fourier transform (FFT) simulation was used to calculate the power and spatial distribution of resonant fields in optical cavities. This is an important tool when characterizing the effect of imperfect geometry and mirror aberrations. This method is, however, intrinsically slow when the cavities are of relatively high finesse. When this is the case, an accelerated convergence scheme may be used to calculate the steady-state cavity field with a speed that is orders of magnitude faster. The rate of convergence of this method, however, is unpredictable, as many different factors may detrimentally affect its performance. In addition, its use in multiple cavity configurations is not well understood. An in-depth study of the limitations and optimization of this method is presented, together with a formulation of its use in multiple cavity configurations. This work has not only resulted in consistent improvement in performance and stability of the accelerated convergence method but also allows the simulation of optical configurations, which would not previously have been possible.

On the use of computed radiography plates for quality assurance of intensity modulated radiation therapy dose distributions.

PURPOSE: As traditional film is phased out in most radiotherapy centers, computed radiography (CR) systems are increasingly being purchased as a replacement. CR plates can be used for patient imaging, but may also be used for a variety of quality assurance (QA) purposes and can be calibrated in terms of dose. This study looks at their suitability for verification of intensity modulated radiation therapy (IMRT) dose distributions. METHODS: A CR plate was calibrated in terms of the relative dose and the stability of response over 1 year was studied. The effect of exposing the CR plate to ambient light and of using different time delays before scanning was quantified. The CR plate was used to verify the relative dose distributions for ten IMRT patients and the results were compared to those obtained using a two dimensional (2D) diode array. RESULTS: Exposing the CR plate to 10 s of ambient light between irradiation (174 cGy) and scanning erased approximately 80% of the signal. Changes in delay time between irradiation and scanning also affected the measurement results. The signal on the plate was found to decay at a rate of approximately 3.6 cGy/min in the first 10 min after irradiation. The use of a CR plate for IMRT patient-specific QA resulted in a significantly lower distance to agreement (DTA) and gamma pass rate than when using a 2D diode array for the measurement. This was primarily due to the over-response of the CR phosphor to low energy scattered radiation. For the IMRT QA using the CR plate, the average gamma pass rate was 97.3%. For the same IMRT QA using a diode array, the average gamma pass rate was 99.7%. The gamma criteria used were 4% dose difference and 4 mm DTA for head and neck treatments and 3% dose difference and 3 mm DTA for prostate treatments. The gamma index tolerance was 1. The lowest 10% of the dose distribution was excluded from all gamma and DTA analyses. CONCLUSIONS: Although the authors showed that CR plates can be used for patient specific IMRT QA, the practical problems such as the over-response to low energy scatter and signal fading with light exposure and time mean that alternative detectors such as radiochromic film or diode arrays will be a more sensible choice for most radiotherapy departments.

Detecting protein-protein interactions in the intact cell of Bacillus subtilis (ATCC 6633).

The salt bridge, paired group-specific reagent cyanogen (ethanedinitrile; C(2)N(2)) converts naturally occurring pairs of functional groups into covalently linked products. Cyanogen readily permeates cell walls and membranes. When the paired groups are shared between associated proteins, isolation of the covalently linked proteins allows their identity to be assigned. Examination of organisms of known genome sequence permits identification of the linked proteins by mass spectrometric techniques applied to peptides derived from them. The cyanogen-linked proteins were isolated by polyacrylamide gel electrophoresis. Digestion of the isolated proteins with proteases of known specificity afforded sets of peptides that could be analyzed by mass spectrometry. These data were compared with those derived theoretically from the Swiss Protein Database by computer-based comparisons (Protein Prospector; http://prospector.ucsf.edu). Identification of associated proteins in the ribosome of Bacillus subtilis strain ATCC 6633 showed that there is an association homology with the association patterns of the ribosomal proteins of Haloarcula marismortui and Thermus thermophilus. In addition, other proteins involved in protein biosynthesis were shown to be associated with ribosomal proteins.

Identification of two penicillin-binding multienzyme complexes in Haemophilus influenzae.

Dansyl-labeled penicillin, reversed-phase chromatography, and peptide mapping have been used to detect, separate, and study penicillin-binding proteins (PBPs) and PBP multienzyme complexes of H. influenzae. The cross-linking of proteins in the multienzyme complex was accomplished with the aid of cyanogen, a salt-bridge specific cross-linking agent. The chromatographic profile of the PBPs clearly showed a dramatic change in the number and identity of peaks after treatment of the bacterial cells with cyanogen. The disappearance of all seven peaks corresponding to the PBPs was accompanied by the emergence of two new peaks with molecular weights between 400 kDa and 600 kDa. The results hint at the existence of two penicillin-binding multienzyme complexes, each containing subunits that interact via salt-bridges. Chromatographic active site peptide mapping of PBPs and PBP complexes was used to determine the identity of PBPs involved in each complex. It is postulated that one multienzyme complex containing PBP 2 may be involved in cell elongation while the other complex containing PBP 3 may be responsible for cell division.

Foramen magnum decompression for cervicomedullary encroachment in craniometaphyseal dysplasia: case report.

OBJECTIVE AND IMPORTANCE: Foramen magnum encroachment has been cited as a potential cause for the premature demise of patients afflicted with craniometaphyseal dysplasia (CMD). To our knowledge, the association of Chiari malformation and syringomyelia with CMD has not been previously reported. We describe our evaluation and surgical treatment of a patient presenting with CMD, foramen magnum stenosis, Chiari I malformation, and syringomyelia. CLINICAL PRESENTATION: A 15-year-old female patient with CMD presented with severe headaches and progressive myelopathy. Evaluation by computed tomography and magnetic resonance imaging revealed mild ventriculomegaly, cervicomedullary compression secondary to Chiari I malformation and foramen magnum stenosis, and C3-T10 syringomyelia. INTERVENTION: Foramen magnum decompression was performed via suboccipital craniectomy, C1-C2 laminectomy, and dural augmentation. Dysplastic bone was revealed to be extremely thick and mineralized. Removal required lengthy and extensive drilling. The postoperative course was complicated by prolonged intubation secondary to airway obstruction and a perforated duodenal ulcer. Airway obstruction was attributed to severe nasopharyngeal bony dysplasia and soft tissue edema. The use of steroids in the treatment of airway edema and delayed enteral feeding was thought to contribute to ulcer development. Nevertheless, neurological symptoms improved dramatically. CONCLUSION: Foramen magnum decompression can be used to treat life-threatening cervicomedullary compression in patients with CMD. However, caution should be used because surgical intervention may be associated with a higher incidence of complications because of lengthy procedures and the spectrum of craniofacial impairments in patients with CMD.

Lack of specificity in electrophysiological identification of lower sacral roots during selective dorsal rhizotomy.

The authors investigated the efficacy of anal sphincter electromyography (EMG) in identifying the lower sacral roots during selective dorsal rhizotomy. In nine children undergoing selective dorsal rhizotomy for cerebral palsy (CP) spasticity, direct electrical stimulation of the L1-S5 dorsal and ventral roots was performed while monitoring EMG responses from the anal sphincter and lower-extremity muscles. Anal sphincter activation was seen with stimulation of lumbosacral roots at many levels. Stimulation of dorsal and ventral roots gave anal sphincter EMG responses in 100% of the dorsal and ventral roots from L-4 and caudally. Only at the L-1 level did a minority of nerve roots have anal sphincter response to stimulation. Patterns of extremity muscle and sphincter activation specific to the S3-5 roots, namely anal sphincter activation without activation of other muscle groups, were found in only five (22%) of 23 roots stimulated. The pattern of stimulation responses in the majority of S3-5 roots indicated that the pathophysiology of lower-extremity spasticity in CP may involve the anal sphincter and does not spare the lower sacral roots. Thus, this study indicates that electrophysiological mapping alone, without anatomical identification, cannot be used to identify the lower sacral roots during selective dorsal rhizotomy for CP spasticity, and it proposes a model for investigation of associated bowel and bladder symptoms.

Subdental synchondrosis fracture in children: the value of 3-dimensional computerized tomography.

A case is presented illustrating the usefulness of computerized tomography (CT) with 3-dimensional (3-D) reconstruction for evaluation of a subdental synchondrosis fracture in a child. Odontoid fractures in children less than 7 years of age occur at the subdental synchondrosis and are typically diagnosed with plain x-rays. However, a delay in diagnosis is common as these injuries may not be appreciated on initial roentgenographic evaluation. The authors present a case of a 2-year-old boy with a subdental synchondrosis fracture secondary to trauma. In this patient, plain x-ray and conventional axial CT failed to definitively elucidate the child's injuries; however, the use of CT with 3-D reconstruction fully delineated the injury. The use of CT with 3-D reconstruction in evaluating children with subdental synchondrosis fractures is a valuable tool for diagnosis. The treatment of synchondrosis fractures of the odontoid process in children is immobilization of the cervical spine.

Students' evolving beliefs about nursing: from entry to graduation in a four-year baccalaureate programme.

Students become socialised into nursing during an educational programme through interaction with faculty members, classes and seminars, and by the experience of practicing nursing. In this paper, some results from a qualitative study that examined the socialisation of nursing students from one four-year baccalaureate programme are described. The changes in the students' attitudes and values are presented. Davis' (1975) theory of doctrinal conversion is used to examine progress in the process of socialisation. There is evidence that students moved from a lay to a professional image of nursing over the course of their four-year programme. While they tended to remain idealistic, elements of realism were evident in the final year as they looked toward their role as a registered nurse and recognised the constraints inherent in the hospital system.

Fruitlax: management of constipation in children with disabilities.

Seven children, with a variety of disabilities, who had experienced chronic constipation, participated in a study of the use of Fruitlax, a natural laxative. Using an AB single-subject design, data were collected for each child for a baseline period A (2 weeks) and for an intervention period B (minimum of 3 weeks), which included the addition of Fruitlax to the subjects' diets. Whereas each child experienced some change in bowel pattern (consistency, effort required to have a bowel movement, color, amount, frequency, and number of bowel movements per day), the particular change was different for each child. Fruitlax does appear to be a useful natural laxative for some children; however, additional research with a larger sample is required. The Glenrose Stool Consistency Tool was developed for use in this study. Further work is needed in the use of the tool by clients, their families, and health care workers.

A bifunctional monocyclic beta-lactam cross-links across the active site of beta-lactamase.

A 4-alkoxy-2-azetidinone behaves as a bifunctional active site-directed inhibitor of the class A beta-lactamase from Bacillus cereus 569/H. It cross-links SER 70 and LYS 234 as it binds in a approximately 1:1 ratio. The cross-linked enzyme is irreversibly inhibited while the secondary structure is partially stabilized under conditions when the native enzyme is otherwise converted to a form with no detectable secondary structure by circular dichroism.

Learning to nurse in the clinical setting.

The findings reported in this paper are part of a larger study examining student socialization into nursing. In analysing the data, it became evident that two major factors influenced the students' learning in the clinical setting: the first was the clinical instructor, the second peer support. Instructors who were organized, encouraging, outgoing, and who had good relationships with students, patients and nursing staff were seen as 'good' role models. When instructors were unable to establish rapport on a unit, negative feedback from nursing staff could be detrimental to student learning. Peer support encompassed three dimensions: facilitating learning, providing emotional support, and assisting with physical tasks. There was evidence that practising faculty had a stronger influence in shaping students' attitudes towards nursing than classroom teachers.

Peripheral intravenous line survival and phlebitis prevention in patients receiving intravenous antibiotics: heparin/hydrocortisone versus in-line filters.

OBJECTIVE: To compare the use of in-line filtration with the addition of heparin/hydrocortisone (hep/hc) to the infusate for both phlebitis prevention and intravenous (i.v.) line survival in peripheral i.v. catheters. This study was specific for a patient group receiving prolonged courses of i.v. antibiotics. Analysis of the two endpoints for conventional short i.v. catheters (short lines) versus long (30 cm) i.v. catheters (long lines) was also performed. METHODS: Patients with cystic fibrosis receiving intermittent i.v. antibiotics were randomly allocated to receive their drugs either through an in-line filter using a drug-free infusate or with no filter and an infusate containing heparin 500 units and hydrocortisone 10 mg/L. Infusion sites were assessed daily. RESULTS: Both the hep/hc and filter groups were similar in terms of phlebitis incidence and i.v. line survival when analyzed separately for both short and long lines. Long lines displayed markedly prolonged survival times and reduced phlebitis compared with short lines. CONCLUSIONS: The effectiveness of i.v. filters in excluding the large particle load introduced by i.v. antibiotics and hence in reducing the subsequent phlebitis makes them a useful alternative to the use of hep/hc. The use of filters in this patient group may offer advantages in terms of ease of use and a possible decrease in hep/hc-related problems. Long lines offer practical advantages over short lines for patients requiring longer term i.v. access.

Innovation through collaboration.

In light of the Canadian Nurses Association's position that the baccalaureate degree would be the requirement for entry to practice by the year 2000, plus evidence of a rapidly changing health care system, changing client characteristics, and on-going economic constraints, administrators of nursing programs in Edmonton recognized the need for a more process-oriented curriculum to prepare nurses to be more capable of facing future challenges. Not surprisingly, limited funds and differing human and material resources meant they could not complete a major curriculum change individually. Collaboration proved to be the key that increased access to baccalaureate nursing education in Alberta.

Cyanogen as a selective probe for carbonic anhydrase hydrolase activity.

The salt bridge probe cyanogen (ethanedinitrile, C2N2; N identical to C-C identical to N) inhibits the bovine carbonic anhydrase (EC 4.2.1.1.) hydrolase activity toward various types of esters without significant effect on its hydrolyase activity. Two sets of pyridine derivatives that were isosteric substrates for the two activities were differentially affected. Acetazolamide and salamide are reversible inhibitors of the enzyme; only salamide affords protection of the hydrolase activity against the action of C2N2. Since each is known to bind in different positions within the active site, the selective effect of salamide may arise from its position covering one CO2 site as well as a site important for hydrolase activity. The C2N2 concentration dependence of the time course of hydrolase inhibition is consistent with the existence of a high C2N2 affinity site with slow covalent change and a second site with lower C2N2 affinity, but higher rate of covalent modification of the enzyme.

Effectiveness of a handwashing program.

A pilot study to develop and evaluate a program to teach 13 Grade 1 children with disabilities about handwashing was conducted at Glenrose School, which is located within Glenrose Rehabilitation Hospital. Children aged 6 to 8 years were taught how and when to wash their hands. Handwashing skills were evaluated before the teaching began, immediately following the teaching program, and at 1, 3, and 5 months postteaching. The children's handwashing skills did improve, with the girls generally scoring higher than the boys on both washing techniques and times of washing on all the testing occasions. Although the children had fewer visits to the doctor, took fewer prescribed antibiotics, and had fewer infectious illnesses than they did for the same time period the previous year, other variables, in addition to the teaching program, may have contributed to the outcome. A revised handwashing program is now included in the Grade 1 curriculum.

Identification of the sites of modification on bovine carbonic anhydrase II (BCA II) by the salt-bridge reagent cyanogen, C2N2.

The hydrolase activities of bovine carbonic anhydrase B (BCA II carbonate hydrolyase, EC 4.2.1.1) were modified by cyanogen (C2N2, N identical to C-C identical to N, ethanedinitrile) with decreases in Vmax of as much as 99%. This was not accompanied by a reduction in hydrolyase activity. These changes were not reversed at lower pH values but the enzymatic activity was restored by incubation at pH 10. 14C-labeled glycine ethyl ester ([14C]GEE) specifically and covalently bound to the cyanogen-treated BCA II, as verified by HPLC and 14C monitoring. It was shown that sites of cyanogen-introduced modifications in BCA II could be effectively labeled and identified by incubation with the nucleophile [14C]GEE. Three radiolabeled tryptic peptides from BCA II arising from a labeling process designed to study cyanogen-induced modifications leading to nucleophile labile covalent bonds have been isolated. The residues identified by [14C]GEE labeling were Asp-34, Glu-117 and Asp-152. Three moieties attached to the omega-carboxyls by C2N2 were tentatively identified by molecular modeling; they were Arg-111, His-107 and/or His-119 and Ser-216, respectively. The use of C2N2 afforded a means to compare the salt bridges in two species and showed that two of three were not conserved.

Posterior cricoarytenoid activity in normal adults during involuntary and voluntary hyperventilation.

The effect of isocapnic hypoxia and hyperoxic hypercapnia on the electrical activity of the posterior cricoarytenoid (PCA) muscle was determined in eight normal adult humans by use of standard rebreathing techniques and was compared with PCA activity during voluntary hyperventilation performed under isocapnic and hypocapnic conditions. PCA activity was recorded with intramuscular hooked-wire electrodes implanted through a fiberoptic nasopharyngoscope. During quiet breathing in all subjects, the PCA was phasically active on inspiration and tonically active throughout the respiratory cycle. At comparable increments in respiratory output, hypercapnia, hypoxia, and voluntary hyperventilation appeared to be associated with similar increases in phasic or tonic PCA activity. During quiet breathing, the onset of phasic PCA activity usually occurred before inspiratory airflow and extended beyond the start of expiratory airflow. The duration of phasic PCA preactivation and postinspiratory phasic PCA activity remained unchanged during progressive hypercapnia and progressive hypoxia. The results, in combination with recent findings for vocal cord adductors, suggest that vocal cord position throughout the respiratory cycle during hyperpnea is actively controlled by simultaneously acting and antagonistic intrinsic laryngeal muscles.

Creatinine, lactam and cyclic peptide formation by the action of C2N2 on creatine, omega-amino acids and peptides.

Cyanogen, C2N2, affords a means to drive intramolecular conversion of ammonium salts to amides. Unlike other carboxyl activating agents, such as carbodiimides, used in peptide syntheses expressly to drive intermolecular condensations to form amide (peptide) bonds, C2N2 appears restricted to driving only intramolecular condensations. Rates decreased as a function of solvent composition as follows: organic much greater than 70%-80% aqueous organic much greater than 50% aqueous organic greater than H2O. Temperature dependence was also a function of solvent composition. Rates did not strongly reflect steric constraints with beta-lactams and epsilon-lactams forming at comparable rates to rates for gamma- and delta-lactam formation; likewise L-Leu-L-Leu cyclized at about the same rate as L-Leu-D-Leu. Pro-Pro is well documented as having a salt-bridged structure in a variety of solvents where it cyclized extremely rapidly. The reaction is proposed to be dependent on reaction of C2N2 with salt-bridges on the basis of 1) its preponderant if not exclusively intramolecular nature, 2) its solvent dependence, 3) its temperature dependence and 4) the conversion of known salt-bridged structures to amides. This reaction is a model for the observed rapid reaction of salt bridges in proteins.

Effect of concurrent visual feedback on acquisition of a weightlifting skill.

Practice in front of a mirror is a common procedure for activities such as dance, gymnastics, and other sports. The purpose of this study was to examine the effect that performing with concurrent visual feedback from a mirror had on the acquisition of the power clean movement. 18 college-age males who had no prior experience with the power clean movement served as subjects who were assigned to one of two groups. One group had use of a mirror during the practice trials and the other practiced without the mirror. All subjects viewed an instructional videotape and had practice trials. All subjects were evaluated for proper technique on a pretest, a posttest without the mirror, and a posttest with the mirror. Analysis showed a significant difference between pre- and posttest performances for both groups and a significant difference between groups on the posttest performances with the mirror. Evidently the videotaped instruction was sufficient to allow both groups to improve in performance of the power clean. Differences in posttest performances with the mirror reflected the type of feedback (with or without the mirror) available during training.