Styrofoam Block Research Articles

Impact of diaphragm flexibility on dynamic properties and seismic design parameters of irregular buildings in plan

One of the established conditions of structural regularity in modern Mexican seismic codes is that a rigid and strong diaphragm has to be provided at each story. However, this condition is one of the least rigorously reviewed in the design of buildings in Mexico. During the past 15–20 years, a modern version of flatslab floor systems are being dominantly used in new building construction in Mexico City. However, their ability to transmit and carry adequately important seismic loads has not been demonstrated. In this paper, the authors present a study where two buildings irregular in plan using a cast-in-place flatslab system lightened with large Styrofoam (EPS) blocks were designed according to Mexican codes as done by most engineers: assuming a rigid and strong diaphragm. Then, the diaphragm flexibility was evaluated using detailed finite element models, as well as equivalent solid slabs with orthotropic modeling and struts models to account for the diaphragm flexibility. It was found that when modeling the diaphragm flexibility, lateral displacements increased from 2.1 to 3.4 times those of the rigid diaphragm assumption. When modeling the diaphragm flexibility, the natural periods of vibration increased, due to the decrement of the effective lateral stiffness for the buildings. It was found that the effective lateral stiffness for the buildings decreased by 54.3% for a subject 8-story confined masonry building and by 66.7% for a subject 15-story RC moment frame building. Switching of dominant mode shapes between the rigid and the flexible diaphragm assumption was also observed.

A Virtual Skin-Model-Building Activity Educates Campers With Chronic Skin Disorders and Their Families

A Virtual Skin-Model-Building Activity Educates Campers With Chronic Skin Disorders and Their Families

A pilot study for intraocular pressure measurements based on vibroacoustic parameters

The present study aimed to identify vibroacoustic properties associated with intraocular pressure (IOP) changes and to suggest a new way to measure the IOP based on these properties. Ten ex vivo porcine eyeballs were used in this study. Each eyeball was fixated in a central hole of a Styrofoam block, and vibration applied to the Styrofoam block was transmitted to the eyeball. An accelerometer directly attached to the eyeball measured the vibration response. Excitations and measurements were performed for 1 s, and the excitation magnitude was varied for the same signal in repeat measurements. A 30-gauge needle was inserted into the anterior chamber of the eyeball to inject a balanced salt solution, and the height of the bottle was adjusted to adjust the IOP. A tonometer was used under identical conditions to measure the IOP five times, and the mean value was determined for further analyses. The measurements showed that the parameters resonance frequency and change in the magnitude of the vibration response (CMVR) increased with rising IOP values. The CMVR was highly correlated with the IOP (p-value < 0.0001). A linear mixed effects model (LMM) was used as a statistical analysis method. We confirmed that vibroacoustic properties of the eyeball are correlated with IOP changes. It is expected that the CMVR will serve as a new parameter for IOP measurements. Thus, in the future, continuous IOP measurements would be easily performed using the CMVR.

Bleeding Puppets: Transmediating Genre in Pili Puppetry

Bleeding Puppets: Transmediating Genre in Pili Puppetry

On the Whiteness of Kara Walker's Marvelous Sugar Baby

On the Whiteness of Kara Walker's Marvelous Sugar Baby Glenda R. Carpio (bio) kara walker's A Subtlety, or the Marvelous Sugar Baby (2014) was nothing if not spectacular. Housed in a storage shed "five stories high and more than a football field long," it featured a great white sphinx measuring "75 feet from paws to rump," rising to the rafters of the building.1 It was the "largest single piece of public art ever erected in New York City."2 Almost lost in all that grandeur, fifteen human-sized statues of brown children stood at intervals across the vast space. Yet the decay and eventual destruction of nearly all the sculptures was built into their design. The sphinx's core was comprised of enormous blocks of foam that, after the work was dismantled, were cut up, cleaned, and taken away for recycling by their manufacturer, the novelistic-sounding Insulation Corporation of America. The outer surface of the installation (its "skin") was coated in about forty tons of sugar, which after months of exposure to a leaking roof and the breath of thousands of visitors could not be recycled or eaten.3 (It was carried off to the dump by Action Carting.) The child sculptures were all in different stages of deterioration by the show's final weeks. Twelve were cast in resin but coated in molasses and [End Page 551] sugar, which partly melted away over the course of the show. The other three were cast in sugar and had collapsed and mostly melted away by the close of the exhibition; their demise was also part of the plan. The demolition of the space itself—the Domino Sugar Refinery in Williamsburg, Brooklyn—was the occasion for the work; it began soon after the installation was dismantled. Click for larger view View full resolution Figure 1. Kara Walker, A Subtlety, or the Marvelous Sugar Baby (2014), polystyrene foam, sugar, approx. 426 x 312 x 906 in. (1,082 x 792.5 x 2,301.2 cm). Artwork © Kara Walker, courtesy of Sikkema Jenkins & Co., New York. The installation's mixture of grandeur and ephemerality was closely tied to the oppositions it made manifest. Drawing on stereotype and caricature, Walker gave the sphinx a Mammy head kerchief and exaggerated the nose and lips. Yet she also made her glowingly, blindingly white. As a Mammy figure, the sphinx indexed Black femininity defined by servility and asexual maternal comfort. Yet Walker also endowed her with buxom breasts, sensual curves, a positively giant rear end, and a ten-foot vulva. And while she rested on her paws, assuming a posture of docility, the sphinx's chin and jaw jutted straight out above her viewers; in her left paw, the thumb was tucked [End Page 552] between her index and middle fingers in the figa sign, an obscene gesture that is also a symbol of fertility. Subtle she was not. In this series of contradictions, several realities crystalized. Invoking the grand, mythical power of racialized sexual stereotype through the sphinx's scale and figurative details, Walker made explicit the forms of desire and pleasure that the stereotype surreptitiously, but palpably, affords. At the same time, she materialized the ostentatious architecture of racial arrogance, using not only scale but also color (the sphinx's whiteness) while exposing the flimsiness of its core (Styrofoam blocks). As she has done throughout her career, Walker deployed aesthetic form to expose the myths that shore up ideology and to draw out otherwise obscured relations of power. The sphinx put on grand display the connection between the leisure and pleasure taken at the expense of the labor of others (indexed through the history and consumption of sugar) and the sexual degradation and objectification of enslaved people, especially women, whose labor have produced and maintained the wealth of empires. The site specificity of the installation was key in this process of crystallization. The Domino Sugar Refinery, as Walker succinctly put it, was, like others in the history of sugar, "a factory for the production of death and destruction."4 When Creative Time commissioned her to create a public work to mark the demolition of the refinery, she faced a great challenge...

SU‐G‐JeP3‐11: Use of an Easily‐Modified Simple Phantom to Perform the Daily and Monthly Localization QA Tasks for a Video‐Based Surface Imaging System

Purpose:To describe a simple, easily fabricated, Styrofoam phantom used in conjunction with a commonly available OBI phantom, to QA a video‐surface imaging system according to TG147, using minimal effort.Methods:Styrofoam, a common packaging material, reflects the speckled AlignRT light very well. A Styrofoam block was used as a partial cap to attach onto a standard Varian Marker Match phantom. The cap was engraved with two sets crosshairs on each surface, one at the ‘zero’(center) and the other an ‘off‐centered’ position, 2 cm in all three orthogonal directions. A reference image is obtained at ‘zero’ position. For the daily test, static localization check is performed by aligning the phantom with room lasers at ‘off‐centered’ position and then the couch is shifted to match the ‘zero’ with the lasers. For the monthly test, plate calibration is recommended to define a relationship between an image point on the camera and that of the isocenter in the treatment room. Static localization accuracy is checked using a hidden‐target test, which is an extension of daily static localization procedure. The phantom positioned at ‘off‐centered’ is shifted to make the readings 0.0 cm for all orientations. The location of the hidden target is then verified by taking orthogonal kV images or CBCT.Results:The AlignRT tests required by TG147 are quite similar to those performed on on‐board imaging (OBI). Overall alignment of the system is maintained with RMS &lt; 1 mm and any potential problems were identified. The system's static location is maintained within ± 1 mm. The same accuracy can be obtained for a monthly hidden target test which is integrated with an OBI QA.Conclusion:A customized phantom is tested and a routine QA program for surface‐imaging system is introduced. By dealing with a single phantom, the procedure can achieve similar goals efficiently.

SU-E-I-55: The Contribution to Skin Dose Due to Scatter From the Patient Table and the Head Holder During Fluoroscopy

Purpose: To determine contributions to skin dose due to scatter from the table and head holder used during fluoroscopy, and also to explore alternative design material to reduce the scatter dose. Methods: Measurements were made of the primary and scatter components of the xray beam exiting the patient table and a cylindrical head holder used on a Toshiba Infinix c-arm unit as a function of kVp for the various beam filters on the machine and for various field sizes. The primary component of the beam was measured in air with the object placed close to the x-ray tube with an air gap between it and a 6 cc parallel-plate ionization chamber and with the beam collimated to a size just larger than the chamber. The primary plus scatter radiation components were measured with the object moved to a position in the beam next to the chamber for larger field sizes. Both sets of measurements were preformed while keeping the source-to-chamber distance fixed. The scatter fraction was estimated by taking the ratio of the difference between the two measurements and the reading that included both primary and scatter. Similar measurements were also made for a 2.3 cm thick Styrofoam block which could substitute for the patient support. Results: The measured scatter fractions indicate that the patient table as well as the head holder contributes an additional 10–16% to the patient entrance dose depending on field size. Forward scatter was reduced with the Styrofoam block so that the scatter fraction was about 4–5%. Conclusion: The results of this investigation demonstrated that scatter from the table and head holder used in clinical fluoroscopy contribute substantially to the skin dose. The lower contribution of scatter from Styrofoam suggests that there is an opportunity to redesign patient support accessories to reduce the skin dose. Partial support from NIH grant R01EB002873 and Toshiba Medical Systems Corporation Equipment Grant

SU‐E‐E‐05: Improving Contouring Precision and Consistency for Physicians‐In‐Training with Simple Lab Experiments

Purpose:Target contouring for high‐dose treatments such as radiosurgery of brain metastases is highly critical in eliminating marginal failure and reducing complications as shown by recent clinical studies. In order to improve contouring accuracy and practice consistency for the procedure, we introduced a self‐assessed physics lab practice for the physicians‐in‐training.Methods:A set of commercially acquired high‐precision PMMA plastic spheres were randomly embedded in a Styrofoam block and then scanned with the CT/MR via the clinical procedural imaging protocol. A group of first‐year physicians‐in‐training (n=6) from either neurosurgery or radiation oncology department were asked to contour the scanned objects (diameter ranged from 0.4 cm to 3.8 cm). These user‐defined contours were then compared with the ideal contour sets of object shape for self assessments to determine the maximum areas of the observed discrepancies and method of improvements.Results:The largest discrepancies from initial practice were consistently found to be located near the extreme longitudinal portions of the target for all the residents. Discrepancy was especially prominent when contouring small objects &lt; 1.0 cm in diameters. For example, the mean volumes rendered from the initial contour data set differed from the ideal data set by 7.7%±6.6% for the participants (p&gt; 0.23 suggesting agreement cannot be established). However, when incorporating a secondary imaging scan such as reconstructed coronal or sagittal images in a repeat practice, the agreement was dramatically improved yielding p&lt;0.02 in agreement with the reference data set for all the participants.Conclusion:A simple physics lab revealed a common pitfall in contouring small metastatic brain tumors for radiosurgical procedures and provided a systematic tool for physicians‐in‐training in improving their clinical contouring skills.Dr Ma is current a board member of international stereotactic radiosurgical society

Abstract P1-15-18: Evaluation of separation techniques and dosimetry of the inframammary fold during whole breast radiation therapy

Abstract Purpose/Objectives: The majority of patients receiving radiation therapy will experience some form of skin reaction, ranging from localized erythema to moist desquamation. Radiation dermatitis of the inframammary fold (IMF), the most common acute side effect of supine whole breast radiation therapy (WBRT), can be mitigated by separating the breast from the chest wall. The purpose of this analysis was an objective evaluation and comparison of practical and inexpensive separation techniques. Materials/Methods: A breast phantom was created on a human torso phantom using tissue-equivalent bolus material. Four separation techniques were evaluated: 1) taping the inferior aspect of the breast to the shoulder or placing 2) 6" x 2" rolled bubble wrap, 3) a 6" x 1" x 1" styrofoam block, or a 4) 50 mL 2" diameter plastic conical tube in the IMF. For the control setup, the breast was not taped and nothing was placed in the IMF. Written and pictorial simulation instructions recorded by one radiation therapist were independently used by additional therapists to reproduce each setup, with medial and inferior measurements taken for comparison. Dosimetry of identical tangent 100 cGy WBRT fields was evaluated with thermoluminescent dosimeters (TLDs) placed at each of four locations: the ipsilateral IMF, the ipsilateral chest wall 5 cm inferior to the IMF, and 5 cm superior to the nipple of both the ipsilateral and contralateral breasts at the 12:00 position. Measurements and TLD data are reported as mean ± standard error of the mean of 3 separate TLD readings. One-way ANOVA and posthoc analyses were used to determine significance between groups with α for significance set at p ≤0.05. Results: Compared to simulation, the average differences measured medially and inferiorly among the conical tube (10 ± 6 mm medial; 0.6 ± 0.2 mm inferior), styrofoam block (13 ± 8 mm medial; 1.2 ± 0.2 mm inferior), and bubble wrap (18 ± 4 mm medial; 0.6 ± 0.1 mm inferior) setups were not significant. The taping technique (0.2 ± 0.1 mm) was more reproducible inferiorly than the styrofoam block setup (p &amp;lt;0.01), but no different from the conical tube and bubble wrap setups. TLD readings demonstrated that the IMF received less of the prescribed dose with the taping (108 cGy ± 1.4%), styrofoam block (109 cGy ± 0.9%), or bubble wrap (110 cGy ± 0.9%) techniques compared to either the control (120 cGy ± 1.1%) or conical tube (121 cGy ± 0.4%) setups (each p &amp;lt;0.01). TLD readings from the three other locations were not significantly different between any of the setups. Conclusions: The taping, styrofoam block, and bubble wrap setups were most effective in sparing dose to the IMF. The only difference in reproducibility was between the inferior aspects of the taping and styrofoam block setups, but taping had the disadvantage of being more invasive than the other setups. While this unique analysis did not reveal a single superior solution, the taping, styrofoam block, and bubble wrap separation techniques should be considered by radiation oncologists seeking practical, inexpensive, and easily-implemented solutions to mitigate IMF dermatitis in WBRT patients. Citation Format: Guy Jones, Peter Guion, Jason Cheng, Aparna H Kesarwala. Evaluation of separation techniques and dosimetry of the inframammary fold during whole breast radiation therapy [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-15-18.

Lipoprotein inflammatory properties and serum amyloid A levels but not cholesterol levels predict lesion area in cholesterol-fed rabbits

Rabbits on a 1% cholesterol diet received injections of vehicle with or without D-4F or L-4F. After 1 month, the percent of aorta with atherosclerotic lesions was 24 +/- 15% (vehicle), 10 +/- 6% (D-4F) (P < 0.01 vs. vehicle), and 13 +/- 9% (L-4F) (P < 0.05 vs. vehicle). Inflammatory indexes for HDL and LDL were determined by measuring monocyte chemotactic activity after adding rabbit lipoproteins to human endothelial cells. HDL-inflammatory index (HII) and LDL-inflammatory index (LII), respectively, were 1.39 +/- 0.24; 1.35 +/- 0.29 (vehicle), 0.67 +/- 0.26; 0.63 +/- 0.38 (D-4F) (P < 0.001 vs. vehicle), and 0.67 +/- 0.2; 0.68 +/- 0.32 (L-4F) (P < 0.01 vs. vehicle). Serum amyloid A (SAA) levels were 95 +/- 39, 8 +/- 22, and 7 +/- 19 mug/ml, respectively, for vehicle, D-4F, and L-4F (P < 0.001 vs. vehicle). There was no correlation between lesion area and total plasma or HDL-cholesterol levels. In contrast, there was a positive correlation with HII, LII, and SAA (P = 0.002, P = 0.0026, P = 0.0079, respectively). HII correlated closely with SAA levels (r = 0.6616; r(2) = 0.4377, P < 0.0001). Thus, HII, LII, and SAA are better predictors of lesion area than are total plasma or HDL-cholesterol levels in cholesterol-fed rabbits.

SU-FF-T-290: Measurement of Surface Dose Increase Through Styrofoam And/or Memory Foam Patient Support Systems

Purpose: To investigate the increase of surface dose due to partial loss of build up after the radiation beam passes through Styrofoam and/or Tempur-Med® memory foam mattress. Methods: Depth dose measurements were performed in water in the build-up region a) under Styrofoam blocks of varying thicknesses placed on the surface, b) under regions of different densities of the mattress with varying gaps between the surface and the mattress with 6 and 16 MV beams. Surface dose measurements with 6 MV beams were performed with GafChromics film strips and TLDs in a solid water body phantom imitating a prone breast setup, and on 20 consented patients undergoing prone breast treatments. Results: The depth dose measurements under Styrofoam showed that the build-up region of the depth dose curve was shifted towards the surface by 0.03*thickness of the Styrofoam in cm, where 0.03 represents the density of Styrofoam. The phantom measurements, imitating the treatment conditions showed about a twofold increase of the surface dose when a beam traversed through the mattress and/or the Styrofoam relative to that of air. The superficial depth dose under the mattress showed strong field size dependence, and the buildup loss was almost complete with zero gap, and still significant even with a 5 cm gap. The 16 MV beam, still showed relevant, although diminished surface sparing, and the depth of the maximum dose moved closer to the surface. Conclusion: Dosimetric analyses (both clinical and phantom measurements) showed an approximately twofold increase when using Styrofoam or Tempur-Med platform. Despite their low density, the long path through the mattress and/or Styrofoam can be equivalent to 0.6 to 1.2 cm of water. The use of 16 MV, however, can provide the necessary skin sparing, and the approximate superficial dose of the 6 MV beam.

Ion Specificity and Ionic Strength Dependence of the Osmoregulatory ABC Transporter OpuA

The ATPase subunit of the osmoregulatory ATP-binding cassette transporter OpuA from Lactococcus lactis has a C-terminal extension, the tandem cystathionine beta-synthase (CBS) domain, which constitutes the sensor that allows the transporter to sense and respond to osmotic stress (Biemans-Oldehinkel, E., Mahmood, N. A. B. N., and Poolman, B. (2006) Proc. Natl. Acad. Sci. U. S. A. 103, 10624-10629). C-terminal of the tandem CBS domain is an 18-residue anionic tail (DIPDEDEVEEIEKEEENK). To investigate the ion specificity of the full transporter, we probed the activity of inside-out reconstituted wild-type OpuA and the anionic tail deletion mutant OpuADelta12; these molecules have the tandem CBS domains facing the external medium. At a mole fraction of 40% of anionic lipids in the membrane, the threshold ionic strength for activation of OpuA was approximately 0.15, irrespective of the electrolyte composition of the medium. At equivalent concentrations, bivalent cations (Mg(2+) and Ba(2+)) were more effective in activating OpuA than NH(4)(+), K(+), Na(+), or Li(+), consistent with an ionic strength-based sensing mechanism. Surprisingly, Rb(+) and Cs(+) were potent inhibitors of wild-type OpuA, and 0.1 mM RbCl was sufficient to completely inhibit the transporter even in the presence of 0.2 M KCl. Rb(+) and Cs(+) were no longer inhibitory in OpuADelta12, indicating that the anionic C-terminal tail participates in the formation of a binding site for large alkali metal ions. Compared with OpuADelta12, wild-type OpuA required substantially less potassium ions (the dominant ion under physiological conditions) for activation. Our data lend new support for the contention that the CBS module in OpuA constitutes the ionic strength sensor whose activity is modulated by the C-terminal anionic tail.

Ligand-Induced 5-HT3 Receptor Internalization in Enteric Neurons in Rat Ileum

Release of 5-hydroxytryptamine (5-HT) from mucosal enterochromaffin cells and activation of 5-HT(3) receptors (5-HT(3)Rs) on neurons in the gut wall is important in the response of the gut to the luminal environment. Intestinal inflammation is associated with increased levels of mucosal 5-HT. The aims of the study were to determine the following: (1) if 5-HT(3)R undergoes ligand-induced internalization in myenteric neurons, and (2) the effect of long-term increase of mucosal 5-HT on 5-HT(3)Rs. Acute effects of exogenous 5-HT or endogenous release of 5-HT by luminal glucose on cellular localization of 5-HT(3)Rs was determined by immunohistochemistry and confocal microscopy. Treatment with the serotonin re-uptake inhibitor, fluoxetine, for 6 days (20 mg/kg daily orally) was used to increase mucosal 5-HT chronically in rats. Net ileal fluid movement was measured in anesthetized rats by the weight change of a 2.5% agarose cylinder. Acute increases in 5-HT induced by exogenous or endogenous 5-HT decreased 5-HT(3)R immunoreactivity at the neuronal cell membrane by 70% and 60%, respectively. Chronic fluoxetine treatment increased mucosal levels of 5-HT and decreased membrane 5-HT(3)R immunoreactivity by 27%. Net fluid absorption was decreased by a 5-HT(3)R agonist or by luminal glucose; this was attenuated 88% and 99%, respectively, by fluoxetine treatment. Long-term increase in 5-HT in the intestinal mucosa results in increased 5-HT(3)R internalization in myenteric neurons. Chronic changes in mucosal 5-HT may alter gastrointestinal secretory and motor function via ongoing loss of receptor from neuronal membrane, causing a mismatch between luminal content and absorption.

SU‐FF‐T‐36: MammoSite Dosimetry Under Condition of Insufficient Buildup and the Proximity of the Balloon to the Lung

Purpose: Brachytherapy dose planning for MammoSite assumes full scatter buildup. Clinically, MammoSite dosimetry is affected by the buildup condition between the balloon and the skin and the reduced backscatter contribution from the lung. We attempted to answer the following questions: what is the effect of insufficient buildup? What is the dose to the lung? Method and Materials: A breast phantom consisting of polystyrene slabs and Styrofoam blocks is constructed. The thickness of slabs may vary to simulate the varying tissues thickness between the balloon surface and skin. Kodak EDR2 films are mounted parallel to the MammoSite catheter between the polystyrene slabs and the Styrofoam blocks. For each thickness of polystyrene slab above the base, the films are irradiated with the same dose. The films are scanned and analyzed by the RIT software. Results: The insufficient dose buildup and the lack of backscatter contribution may lead to underdosage at the prescription depth. With only 1 cm tissue above the balloon surface, the minimum dose at the prescription depth is only 75% of the dose under full scatter buildup. Even with 3.5 cm tissue, the dose at 10 mm is only 85%. The lung dose, on the other hand, exhibits a buildup behavior, which varies with the thickness of tissue. As much as 180% of the prescribed dose may be delivered to the lung in the vicinity to the balloon surface. Conclusion: The insufficient dose buildup and the presence of lung lead to undersage at the prescription distance which is not revealed in all existing planning system since full scatter buildup without heterogeneity correction is assumed. For correct MammoSite dosimetry, the above issues should be addressed properly. The excessive lung dose even under insufficient dose buildup is may be avoided in some cases by careful placement of the balloon.

Fecundity of Naturally Blood-FedOchlerotatus japonicus

Ochlerotatus japonicus (Theobald) collected in gravid traps were held individually in modified BioQuip breeders in a darkened room under ambient conditions and readily oviposited on Styrofoam blocks. Counts were made of eggs laid on Styrofoam blocks, container sides, and water surface, and dissections allowed for counts of retained eggs to determine the fecundity of this species. In total, 32,970 eggs were oviposited by 289 females with a range of 3-249 eggs per female. The mean +/- SD number of eggs oviposited per female, 114.08 +/- 51.08, was significantly less than the mean number of eggs produced per female, 125.85 +/- 47.89. Wing lengths ranged from 2.8 to 4.7 mm with a mean of 3.81 +/- 0.38 mm. Wing length was positively correlated with total eggs formed (r2 = 0.3481); wing = 3.22054 + 0.0047 total eggs formed. There was no monthly size difference although females collected during October produced significantly fewer eggs than females collected from June to September. A low egg viability of 40% was attributed to improper storage of the Styrofoam blocks on which eggs were oviposited.

Fecundity of Naturally Blood-Fed &lt;I&gt;Ochlerotatus japonicus&lt;/I&gt;

Ochlerotatus japonicus (Theobald) collected in gravid traps were held individually in modified BioQuip breeders in a darkened room under ambient conditions and readily oviposited on Styrofoam blocks. Counts were made of eggs laid on Styrofoam blocks, container sides, and water surface, and dissections allowed for counts of retained eggs to determine the fecundity of this species. In total, 32,970 eggs were oviposited by 289 females with a range of 3-249 eggs per female. The mean +/- SD number of eggs oviposited per female, 114.08 +/- 51.08, was significantly less than the mean number of eggs produced per female, 125.85 +/- 47.89. Wing lengths ranged from 2.8 to 4.7 mm with a mean of 3.81 +/- 0.38 mm. Wing length was positively correlated with total eggs formed (r2 = 0.3481); wing = 3.22054 + 0.0047 total eggs formed. There was no monthly size difference although females collected during October produced significantly fewer eggs than females collected from June to September. A low egg viability of 40% was attributed to improper storage of the Styrofoam blocks on which eggs were oviposited.

Procedure for accurate fabrication of tissue compensators with high-density material

An accurate method for producing compensating filters using high-density material (Cerrobend) is described. The procedure consists of two cutting steps in a Styrofoam block: (i) levelling a surface of the block to a reference level; (ii) depth-modulated milling of the levelled block in accordance with pre-calculated thickness profiles of the compensator. The calculated thickness (generated by a dose planning system) can be reproduced within acceptable accuracy. The desired compensator thickness manufactured according to this procedure is reproduced to within 0.1 mm, corresponding to a 0.5% change in dose at a beam quality of 6 MV. The results of our quality control checks performed with the technique of stylus profiling measurements show an accuracy of 0.04 mm in the milling process over an arbitrary profile along the milled-out Styrofoam block.

Importance of the needle bevel during spinal and epidural anesthesia.

The needle bevel has an important effect on the path that the needle takes as it traverses tissue. Many anesthesiologists, especially trainees, are unaware of the magnitude of this effect. There is a need for a model, constructed from readily available materials, that can be used to demonstrate the bevel effect and to assess various strategies for accurately advancing the needle. Styrofoam blocks were prepared. The following needles were studied: 25-gauge Quincke, 22-gauge Quincke, 18-gauge Quincke, 24-gauge Sprotte, 25-gauge Whitacre, 22-gauge Tuohy, and 17-gauge Tuohy. The effect of bevel orientation on deflection from midline was measured. Representative results were photographed. The bevel has a significant effect on the path of Quincke and Tuohy needles. The deflection is more pronounced for thinner needles. Pencil-point needles show much less deflection than Quincke needles. Styrofoam blocks provide a model for teaching the basics of spinal and epidural anesthesia. By utilizing styrofoam the trainee can master needle control and gauge the effect of bevel orientation.

Cleaning of Ophthalmic Diamond Scalpels

To ensure optimal performance, it is imperative to properly maintain the condition of ophthalmic diamond scalpels. Refractive surgeons are often confronted with conflicting cleaning recommendations from manufacturers. The problem encountered is to maximize cleaning while minimizing trauma to the diamond to maintain its longevity. The author describes a flexible graded approach to cleaning and maintaining diamond scalpels. The principle of this approach was the development of four successive levels of cleaning based on an increasing risk of trauma to the diamond: Level I--irrigation with distilled water, Level II--hydrogen peroxide or enzyme cleaning, Level III--ultrasonic and detergent cleaning, and Level IV--mechanical styrofoam block cleaning. The protocol was performed prospectively on 50 consecutive radial keratotomy cases, inspecting the blade microscopically after each cleaning step, and determining the level at which cleanliness of the blade was achieved. The effectiveness (clean/dirty) of each cleaning level was evaluated by the author and an experienced surgical assistant. The difficulty in accurately measuring the amount of debris and the force necessary to remove it, limited the judgments made to subjective observation. Only 2 of 50 blades were cleaned at Level I, while 41 of 48 at Level III, and 7 of 7 at Level IV. A multi-leveled systematic process for cleaning maintenance appears most effective for maximal performance and longevity of diamond scalpels used for refractive keratotomy surgery.

Egg Production of Pseudosuccinea columella and Fossaria cubensis (Lymnaeidae) in Laboratory Culture

The lymnaeid snails Pseudosuccinea columella (=Lymnaea columella) and Fossaria cubensis (=Lymnaea cubensis) serve as intermediate hosts for Fasciola hepatica in Florida and Puerto Rico (Batte et al., 1951, Journal of the American Veterinary Medical Association 68: 139-141; De Leon et al., 1972, Journal of Agriculture of University of Puerto Rico 56: 88-92). Isseroff and Smith (1978, Journal of Parasitology 64: 11341135) described a culture technique for F. cubensis in which conditioned water was maintained at a pH of 7.6 and snails were fed a commercial diet. De Leon (1970, Journal of Agriculture of University of Puerto Rico 54: 297305) presented an elaborate system for rearing P. columella in tanks with a soil substrate in which snails fed on algae and boiled leaves of Hibiscus sp. The present report describes production of eggs in mature snails of F. cubensis and P. columella using a modified culture technique which provided a simple, economical method for rearing large numbers of snails. Up to 20 snails may be reared in each container, although only 1 snail per container was used in the egg production study described below. Snails 4-6 mm long were collected from a stream adjacent to the Animal Research Facility (University of Florida) in Gainesville, Alachua County, Florida. Individual F. cubensis usually were found on sparsely vegetated mud banks in shallow water (less than 5 cm) whereas individual P. columella frequently were found in deeper water (up to 10 cm) attached to aquatic vegetation. For egg production studies, individual snails were placed in covered plastic containers (31 x 26 x 10 cm) containing 3 L of water obtained from the same stream and filtered through a #200 U.S. Standard Testing Sieve. Water depth was approximately 3.5 cm. The water was changed every 2 wk, and no attempt was made to adjust the pH, which ranged from 6.5 to 8.0 depending on the time of collection. The containers were kept at ambient room temperature (22-30 C). Each snail was fed fresh lettuce every 3 days after unconsumed lettuce was removed. Three styrofoam blocks (5 cm square) were placed in each container, since the snails preferentially laid eggs on the bottoms of these blocks rather than on the sides of the tank. During a 6-wk period, egg production was monitored on a daily basis for individuals of both species. Styrofoam blocks were removed and the undersurface examined at 10 x for eggs with a stereoscopic microscope. A total of 152 and 173 egg masses was examined from snails of F. cubensis (n = 12 snails) and P. columella (n = 8 snails), respectively. Mean weekly egg mass production per snail in P. columella (6.02) was twice that seen in F. cubensis (3.01), and total weekly egg production per snail was almost 7 times higher in P. columella (123.4) than F. cubensis (18.2). The mean number of eggs per mass was 20.5 for P. columella and 6.1 for F. cubensis. The former value agreed closely with De Leon (1970, loc. cit.) who reported a mean of 19 eggs per mass for P. columella. Isseroff and Smith (1978, loc. cit.) did not report egg production in F. cubensis. Individual P. columella produced many more eggs than F. cubensis, possibly because culture conditions more closely resembled their natural environment (deeper water) than that of F. cubensis (shallow mudbanks). Eggs of both species hatched in 5-7 days and snails began producing egg masses within 3-5 wk. Laboratory reared individuals of both F. cubensis and P. columella proved to be suitable intermediate hosts of F. hepatica with cercarial shedding beginning less than 7 wk after exposure to miracidia. We have maintained colonies of snails for over 1 yr under these conditions and have reared large numbers of snails with a minimum expenditure of time and effort. Published as Florida Agricultural Experiment Station Journal Series No. 6464.