Acceptable Low Level Research Articles

Process Modeling of ICU Patient Flow: Effect of Daily Load Leveling of Elective Surgeries on ICU Diversion

Despite the considerable number of publications on ICU patient flow and analysis of its variability, a basic and practically important question remained unanswered: what maximum number of elective surgeries per day should be scheduled (along with the competing demand from emergency surgeries) in order to reduce diversion in an ICU with fixed bed capacity to an acceptable low level, or prevent it at all? The goal of this work was to develop a methodology to answer this question. An ICU patient flow simulation model was developed to establish a quantitative link between the daily load leveling of elective surgeries (elective schedule smoothing) and ICU diversion. It was demonstrated that by scheduling not more than four elective surgeries per day ICU diversion due to 'no ICU beds' would be practically eliminated. However this would require bumping 'extra' daily surgeries to the block time day of another week which could be up to 2 months apart. Because not all patients could wait that long for their elective surgery, another more practical scenario was tested that would also result in a very low ICU diversion: bumping 'extra' daily elective surgeries within less than 2 weeks apart, scheduling not more than five elective surgeries per day, and strict adherence to the ICU admission/ discharge criteria.

The Advancement of Pure Local Anesthesia for Penile Surgeries: Can an Outpatient Basis Be Sustainable?

Although topical anesthetic blockage for penile surgeries has been substantially reported in the medical literature, its methodology, reliability, and reproducibility have not been consistent. We report on several methods of topical blocks for local anesthesia in patients with indications for penile surgeries. From March 1993 to March 2003, a total of 1131 men, ages 19 to 87, underwent penile surgeries in which 165, 203, 708, 45, and 10 patients received penile implantation, modified Nesbit procedure, venous surgery, venous patches, and arterial revascularization respectively, under pure local anesthesia on an outpatient basis. They were categorized into the implant, Nesbit, venous, patch, and arterial groups respectively. Proximal dorsal nerve blockage, peripenile infiltration, and topical injection, although challenging, were sufficient local anesthesia for patients in the last 4 patient groups. A new method of crural blockade, however, was also required for optimal anesthesia of the cavernous nerve for implantation purposes. The anesthetic effects and postoperative results were satisfactory. Common immediate side effects included puncture of the corpus spongiosum or the deep dorsal vein as well as the innominate vessel, subcutaneous ecchymosis, transient palpitations, and acceptable low level of pain. There were no significant late complications. In the implant group, however, 6.1% of patients (10/165) had experienced pain over the perineum for 1 to 2 weeks postoperatively. Overall there were statistical differences in scoring between the 5 groups in which the implant group stood out when a visual analog scale of 100 mm was used. Topical nerve blockades proved to be reliable, simple, and safe, with minimal complications. They offer the advantages of less morbidity, reduced effects of anesthesia, protection of privacy, and a rapid return to preoperative daily activity.

SU‐EE‐A1‐04: Integrated Complementary IMRT Combined with Image‐Guided HDR Brachytherapy for Cancers of the Uterine Cervix

Purpose: Conventional HDR (CHDR) brachytherapy for cervical cancers often fails to cover the entire gross tumor volume (GTV). CT/MRI‐based 3‐D planning allows optimization of dwell times for improved target coverage, but often at the cost of substantially higher doses to organs at risk (OARs). In the present study, we integrate image‐guided HDR brachytherapy with concomitant complementary IMRT to boost target coverage and maintain low doses to OARs. Method and Materials: Treatment planning CT and MRI images of 6 patients were acquired with CT/MRI‐compatible carbon‐fiber applicator. HDR plans were obtained by modifying CHDR plans to keep bladder and rectum dose below 80%. Based on these HDR plans, IMRT plans were subsequently optimized to complement the dose coverage of GTV with 3‐mm margin (GTV+) and the uterus. To prevent anatomical deformation, IMRT plans were to be delivered immediately following image‐guided HDR treatment with applicator in place. V95% (Target volume receiving 95% prescription dose) and D2 (minimum dose in 2.0‐cm3 OAR volume receiving the highest dose) were used to compare IMRT‐HDR technique with CHDR and HDR optimized for target coverage (OHDR). Results: The MRT‐HDR technique substantially improved target coverage while maintaining bladder and rectum doses at acceptable low level. For the six patients, V95% for GTV+ and the uterus improved from the average of 56.8% and 51.4% in CHDR to 92.5% and 95.3% in IMRT‐HDR, respectively. Average D2 doses to bladder and rectum were 88.7% and 65.2% for CHDR and 72.4% and 71.4% for IMRT‐HDR. In contrast, OHDR improved target coverage, but D2 doses to bladder (>119%) and rectum (87.3% to > 200%) were unacceptably high. Conclusion: Integrated complementary IMRT combined with image‐guide HDR significantly improves dose coverage to the targets while maintaining low doses to OARs. It is dosimetrically and logistically feasible to clinically implement this technique for potentially improved outcome.

DEDICATED INSTRUMENTATION FOR HIGH SENSITIVITY, LOW FREQUENCY NOISE MEASUREMENT SYSTEMS

Low Frequency Noise Measurements (LFNM) can be used as very sensitive tool for the characterization of the quality and the reliability of electron devices. However, especially in those cases in which the frequency range of interest extends below 1 Hz, instrumentation with an acceptable low level of background noise is not easily found on the market. In fact, at very low frequencies, the flicker noise introduced by the electronic components which make up the instrumentation becomes predominant and several interesting phenomena which could be detected by means of LFNM may result completely hidden in the background noise. This consideration is not limited to the case of input preamplifiers but does extend to any piece of instrumentation that contributes to the LFNM systems, and in particular to the power supplies used for biasing the Device Under Test. During the last few years, our research groups have been strongly involved in the design of very low noise instrumentation for application in the field of LFNM. In this work we report the main results which we have obtained together with a discussion of the design guidelines that have allowed us, in a few cases, to reach noise levels not to be equalled by any instrumentation available on the market.

A methodology for risk-based inspection of pressurized systems

This paper describes a methodology for risk-based inspection and focuses on the planning of inspection activities. Brunei Shell Petroleum (BSP) operates a large number of ageing production and evacuation facilities in the South China Sea, and is facing the challenge to identify the optimal inspection effort in a period of time when more production is required and operating costs have to be minimized. Since 1989 major investments (annual costs about 15 million US$) were made to perform base line inspections which resulted in corrective work and a large repository of equipment integrity data. These data require analysis and updating, as defined in this methodology. The challenge is for BSP to implement risk-based inspection of static equipment, which so far has been very successful. The methodology is based on the determination of risk by evaluating the consequences and the likelihood of equipment failure. Likelihood of failure is assessed, by means of extrapolation, at the future planned maintenance campaign to identify the necessary corrective work. The extrapolation is based on historical inspection and maintenance data as well as on anticipated future operating conditions. Such an analysis requires in-depth knowledge of the equipment regarding functions, operating conditions, materials, imposed potential failure modes and causes, and their controlling parameters (integrity parameters). The novelty of the method is that equipment integrity is expressed in terms of integrity parameters, which can be measured and trended. Consequently, based on defined limits for the integrity parameters (i.e. anomaly classifications), actions for managing risk to an acceptable low level can be identified. The transparent linkage between monitoring activities (e.g. inspection) and integrity parameters offers an effective framework to manage and to demonstrate integrity against clear quantifiable acceptance limits. By pursuing the above methodology for all equipment, a list of inspection activities, prioritized on equipment condition and the risk of failure, can be derived. Within BSP this has resulted in a demonstrated increased efficiency of the inspection effort, a focused strategy for repairs executed on a campaign basis, and an improved quantification of BSP's facilities integrity. The approach has been proven in the company to be practical and it can be implemented relatively quickly.

Causes of anomalous solid formation in the exhaust systems of low-pressure chemical vapor deposition and plasma enhanced chemical vapor deposition semiconductor processes

The waste gases in low-pressure chemical vapor deposition and plasma enhanced chemical vapor deposition semiconductor processes react strongly with residual air in the exhaust of the vacuum pump to form solid deposits. It is common practice to purge the exhaust line with pure nitrogen to reduce the concentration of ambient air between the pump and the scrubber to an acceptable low level. However, the unexpected high quantities of exhaust deposits found in some systems cannot be explained by air leaks, impurities in the nitrogen, or diffusion. The problem of anomalous exhaust deposit formation was examined experimentally. A 40 mm pipe, up to 5 m in length and initially filled with nitrogen, was connected to an 80 m3/h dry vacuum pump exhausting to air at atmospheric pressure. The composition of the atmosphere in the pipe was analyzed with a mass spectrometer. Under static conditions, the gas density distribution was ultimately limited, as expected, by simple interdiffusion. When the pump was running, however, there was a dramatic enhancement of the oxygen concentration throughout the pipe. The experimental observations were interpreted in terms of Richardson’s annular effect. It is shown that the pressure fluctuations typical of vacuum pumps are responsible for the enhanced counterflow of air. The effect can be reduced by applying nitrogen purge but, even with a moderate 20 ℓ/min flow rate, deposits can form due to air transported back from the scrubber or exhaust duct.

Potato germ plasm enhancement with disomic tetraploid Solanum acaule. II. Assessment of breeding value of tetraploid F1 hybrids between tetrasomic tetraploid S. tuberosum and S. acaule

The breeding value of tetraploid F1 hybrids between tetrasomic tetraploid S. tuberosum and the disomic tetraploid wild species S. acaule was examined. The F1 hybrids showed a tuber yield and appearance comparable to those of their cultivated parent, indicating a potential as acceptable breeding stocks despite the 50% contribution to their pedigree from wild S. acaule. The cytological behavior of the tetraploid F1 hybrids was examined to determine the probability of recombination for the introgression of S. acaule genes. The majority of the meiotic configurations at metaphase I was bivalents and univalents with mean frequencies of 17.6 and 9.9, respectively. Further, a low frequency of trivalents and quadrivalents was observed. An acceptable low level of meiotic irregularities were observed at the later stages of microsporogenesis, and a reasonable level of pollen stainability was obtained. Therefore, these hybrids could likely be employed for further introgression. From the cytological observations, the following speculations were drawn: (1) some genomic differentiation exists between the S. acaule genomes, (2) at least one of the S. acaule genomes may be homoeologous to the S. tuberosum genomes, (3) intergenomic recombination would likely occur due to the nature of the genomic constitution of the hybrids, and (4) the nature of sesquiploidy of the hybrids may facilitate efficient introgression and establishment of unique aneuploid and euploid recombinant genetic stocks.

The effect of discrete scatterers on a low sidelobe antenna

The effect of randomly distributed scatterers placed in the far field of an antenna is explored. A technique for predicting the effects of specular scatterers on antenna performance has been developed. Laboratory testing of a low sidelobe antenna indicated an acceptable low sidelobe level. However, when the antenna was field tested, it exhibited average radiated power levels off the main beam that were significantly greater than those anticipated. In an effort to determine the cause of this increase, a computer model of an antenna in a field site has been developed, which includes the calculation of the total scattered power of the antenna main beam and sidelobes from specular reflectors distributed over the far field of the antenna.

Follow-on stress analysis at components of nuclear power plants

Abstract This paper describes a dynamic measuring data logger with delay storage. With its help the causes for cracks in a feedwater-tank of a Pressurized Water Reactor (of a 1200 MW power station) were recognized during service. After constructional modification and change of the pressure vessel's mode of operation, new measurements showed a reduction of strain to only 20% of the original values. This know-how was brought to a second feedwater-tank which still was under construction. Then similar measurements were performed during the time where the Boiling Water Reactor was put into service. The same phenomena were found but the maximum strains were then at an acceptable low level.