Collar Size Research Articles

Implementation of a Bottom-Hole Assembly Program

A state of the art graphical user interface program has been developed to predict and design the bottom-hole assembly (BHA) performance for drilling. The techniques and algorithms developed in the program are based on those developed by Lubinski and Williamson. The BHA program facilitates conducting parametric studies and making field decisions for optimal BHA performance. The input parameters may include formation class, dip angle, hole size, drill collar size, number of stabilizers, and stabilizer spacing. The program takes into consideration bit-formation characteristics and interaction, drilling fluid weight, drill collar sizes, square collars, shock absorbers, measurement while drilling tools, reamer tools, directional tools, rotary steerable systems, etc. The output may consist of hole curvature (buildup or drop rate), hole angle, and weight on bit and is presented in drilling semantics. Additionally, the program can perform mechanical analyses and can solve for the bending moments and reaction forces. Moreover, the program has the capability to predict the wellpath using a drill ahead algorithm. The program consists of a mathematical model that makes assumptions of 2D, static, and constant hole curvature, resulting in a robust computationally efficient tool that produces rapid reliable results.

Does extended wear of a tight necktie cause raised intraocular pressure?

In order to investigate the effect that extended wear of a tight necktie has on the intraocular pressure (IOP), one eye of 18 normal and 19 primary open-angle glaucoma patients was included in this prospective study. The intraocular pressure of each patient’s randomly selected eye was measured with the patient dressed in an open shirt collar, again 3 minutes after their collar was fastened and necktie tightened, again after a further 12 minutes, and finally 3 minutes after the necktie was loosened and collar unfastened. The same examiner performed all measurements in a masked fashion. The mean intraocular pressure in the normal group (n = 18) increased by 0.56 mm Hg (P = .30) and increased significantly (*) in the glaucoma group (n = 19) by 1.58 mm Hg (P = .001*) after tightening the necktie for 3 minutes. The mean IOP then decreased after leaving the necktie on for a further 12 minutes, by 0.89 mm Hg (P = .08) in the normal group and decreased significantly by 0.94 mm Hg (P = .04*) in the glaucoma group. Finally after loosening the necktie for 3 minutes (immediately after 15 minutes of continuous necktie wear), the mean IOP decreased in the normal group by 0.89 mm Hg (P = .02*) but only minimally in the glaucoma group by 0.16 mm Hg (P = .72). The patient’s age or collar size showed no significant correlation with the change in mean IOP following tight necktie wear. A significant increase in IOP after 3 minutes of tight necktie wear occurred only in the glaucoma group, but this increase was followed by a significant decrease in IOP after 15 minutes of tight necktie wear. Avoidance of wearing a tight necktie over an extended period is, therefore, not necessary in patients with glaucoma.—Hans E. Grossniklaus

Does Extended Wear of a Tight Necktie Cause Raised Intraocular Pressure?

To investigate the effect that extended wear of a tight necktie has on the intraocular pressure (IOP), measured by Goldmann applanation tonometry in a normal and aged-matched glaucoma group. One eye of 18 normal and 19 primary open-angle glaucoma patients was included in this prospective study. The intraocular pressure of each patient's randomly selected eye was measured with the patient dressed in an open shirt collar, again 3 minutes after their collar was fastened and necktie tightened, again after a further 12 minutes, and finally 3 minutes after the necktie was loosened and collar unfastened. The same examiner performed all measurements in a masked fashion. The mean intraocular pressure in the normal group (n = 18) increased by 0.56 mm Hg (P = 0.30) and increased significantly (*) in the glaucoma group (n = 19) by 1.58 mm Hg (P = 0.001*) after tightening the necktie for 3 minutes. The mean IOP then decreased after leaving the necktie on for a further 12 minutes, by 0.89 mm Hg (P = 0.08) in the normal group and decreased significantly by 0.94 mm Hg (P = 0.04*) in the glaucoma group. Finally after loosening the necktie for 3 minutes (immediately after 15 minutes of continuous necktie wear) the mean IOP decreased in the normal group by 0.89 mm Hg (P = 0.02*) but only minimally in the glaucoma group by 0.16 mm Hg (P = 0.72). The patient's age or collar size showed no significant correlation with the change in mean IOP following tight necktie wear. A significant increase in IOP after 3 minutes of tight necktie wear occurred only in the glaucoma group, but this increase was followed by a significant decrease in IOP after 15 minutes of tight necktie wear. Avoidance of wearing a tight necktie over an extended period is therefore not necessary in patients with glaucoma.

A pilot study to assess the possible methods of determining the burden of obstructive sleep apnoea syndrome in primary care

A significant minority of otherwise healthy adults may suffer from disordered breathing during sleep. The commonest problem, known as Obstructive Sleep Apnoea Syndrome (OSAS), results in poor quality sleep, daytime hypersomnolence and excess risk of road traffic crashes. It is also associated with occupational injuries. OSAS can be successfully treated, reducing costs of hospitalisation. There is a gap in the literature regarding the burden of patients with OSAS in primary care, particularly because there is no agreed method for screening. This pilot study was designed to determine the feasibility of screening for OSAS in a UK inner-city multi-ethnic primary care population, to investigate ways in which it might be detected, and to gain an awareness of the potential size of the burden of OSAS METHODS: We tested two methods of screening: firstly, postal questionnaires to a random sample of 240 patients from a subset of the population at highest risk of OSAS (men aged 35-65 years); and secondly, the same questionnaire plus two screening tools for detecting hypersomnolence, given to patients attending the practice for pre-registration health checks. Despite reminders, only 40% of postal questionnaires were returned and there were only 67 (28%) usable responses. The prevalence of snoring was 55%. Almost half of those patients who responded (46%) had a Body Mass Index (BMI) associated with a high risk of OSAS. This was not a positive responder bias because there were no significant differences in BMI between responders and non-responders. 12% had a collar size of greater than 17.5, whilst 34% reported daytime sleepiness, and 24% reported witnessed apnoea. Screening during pre-registration health checks proved both feasible and productive with 38 patients of differing linguistic abilities completing the assessment. Screening for OSAS in primary care by means of a postal questionnaire produced a low response. Whilst there was no evidence of a responder bias in terms of BMI, the numbers reporting large collar size, daytime sleepiness and witnessed apnoea suggest that a sizeable proportion of the population is at risk of OSAS. Questionnaires used in this study provide a means of identifying patients with symptoms suggestive of OSAS, although the sensitivity, specificity and positive predictive value of a self-administered instrument needs to be confirmed by a larger study incorporating ventilatory monitoring during sleep. The addition of screening to pre-registration health checks is feasible, but it would take a long time to screen all those at risk for OSAS by this route.

Initial stability of cemented femoral stems as a function of surface finish, collar, and stem size.

The optimum surface roughness of cemented femoral stems used for total hip replacement is a subject of controversy. While rougher surfaces provide stronger cement adhesion, it has been hypothesized that polished, tapered, noncollared stems settle into the cement mantle, providing improved stability. However, the effects of surface finish on the stability of straight, cemented stems tapered only in the coronal plane are not known. Using composite model femora, we assessed the initial stability of a straight, cemented femoral stem as a function of surface roughness, the presence or absence of a collar, stem size, and the resultant cement thickness under simulated walking and stair-climbing loads. Otherwise identical stems were manufactured with polished or rough surfaces, with or without a collar, in two different sizes. We isolated these three variables and compared their relative contributions to the motion at the stem-cement interface throughout cyclic loading. We defined three indicators of stability: per-cycle motion, rate of migration, and final migration. Surface roughness had a greater influence on per-cycle motions than did the presence or absence of a collar or cement thickness. Specifically, in the medial-lateral direction, per-cycle motion of polished stems was 43 micro m greater than that of rough stems (p < 0.01). None of the per-cycle motions decreased over the 77,000 load cycles. In contrast, with all stems, the rate of migration decreased over the course of cyclic loading, but the rate of migration of the polished stems was greater than that of the rough stems. Final migrations of the stems over the course of loading were generally distal, medial, and into retroversion. Compared with rough stems, polished stems had 8 to 18 micro m more axial migration (p < 0.001), 48 micro m more anterior-posterior migration (p < 0.001), and 0.4 degrees more rotational migration (p = 0.01). and The results indicated that, for cemented, straight femoral stems tapered only in the coronal plane, a rough surface offers the advantage of less per-cycle motion. These results may apply to widely used cemented stem designs based on the profile of the original Charnley femoral component, which has approximately parallel anterior and posterior aspects.

Carotenoid status signaling in captive and wild red-collared widowbirds: independent effects of badge size and color

Carotenoid-based plumage ornaments are typically considered to be sexually selected traits, functioning as honest condition-dependent signals of phenotypic quality, but few studies have addressed the function of carotenoid color variation in male contest competition. Using two experiments, we investigated the status signaling function of the variable (ranging from yellow to red) carotenoid throat patch (collar) in the polygynous, sexually dimorphic red-collared widowbird (Euplectes ardens). First, we tested if the red collar functions as a dominance signal by painting spectrometrically controlled collar patches onto the brown plumage of nonbreeding males and staging dyadic male contests over food resources. Red-collared males dominated orange males, which in turn dominated the control brown and novel blue collars. Red dominance persisted when the collar manipulations were reversed within dyads and also when tested against testosterone implanted males. In the second experiment the collar size and color of breeding males were manipulated in the field before and after territories were established. All males with enlarged red and most with enlarged orange or reduced red collars obtained territories, whereas most males with reduced orange and all with blackened (removed) collars failed to establish or retain territories. In addition, among the territorial males, those with reduced signals defended smaller territories, received more intrusions, and spent more time in aggressive interactions. Redness and, to a lesser extent, size of the carotenoid ornament both seem to independently indicate male dominance status or fighting ability in male contest competition. Copyright 2002.

Agonistic carotenoid signalling in male red-collared widowbirds: aggression related to the colour signal of both the territory owner and model intruder

Carotenoid colour displays are widely assumed to be honest indicators of individual health or quality, primarily in mate attraction. Here we show that sexually dimorphic carotenoid ornamentation functions as an agonistic signal in male red-collared widowbirds, Euplectes ardens. Mounted male models differing (within natural limits) in the intensity of carotenoid signalling were presented to wild resident males as simulated intruders, perched or made to ‘fly’ across the territory with the elongated tail folded or keeled. Perched mounts were generally ignored, and stronger aggression towards ‘flying’ models with a keeled tail (i.e. as in courtship display) than a folded tail suggests the tail display is used to assess the intention of intruding males. Territory owners were less aggressive towards models with intense collar display, suggesting that carotenoid coloration functions as a badge of status in this species. The level of aggressive response was also related to the resident's own badge in that males with larger, redder collars responded more aggressively to the models. In addition, males with a larger collar signal defended larger territories and spent less time in territory defence. Apart from the collar size and ‘redness’, no other morphological variable predicted the aggressive response of territorial males. Given the previously demonstrated insignificance of the collar in female mate choice, we suggest that the nuptial carotenoid coloration is an honest signal of dominance or fighting ability, sexually selected through male contest competition over territories.

Systematic analysis of snoring in women.

Nineteen percent of women are habitual snorers, yet most snoring studies report only on male snorers. The aim of this study was to identify the factors responsible for habitual snoring in women. Twenty-four snorers and 16 controls were studied prospectively in a special snoring clinic. Snorers were shorter (p = .005) and heavier (p = .001), and with greater body mass index (BMI: p < .001), collar size (p = .002), and submental skinfold thickness (p = .001) than controls. The area of the posterior pharyngeal wall visible on oral examination was smaller in snorers (p = .005). Acoustic rhinometry areas and volumes were similar in the two groups. Nasal flow-volume loops showed reduced expiratory (p = .01) and inspiratory (p = .07) flow in snorers. Inspiratory flow correlated inversely with nasal symptoms (p < .05). The factors that best predict habitual snoring in women are a high BMI, a high nasal symptom score, and heavy weight. Of these, BMI is the most powerful.

Sleepiness and driving: the experience of heavy goods vehicle drivers in the UK.

An interview survey of 996 heavy goods vehicle (HGV) drivers was undertaken. It was designed to investigate the relationship between HGV drivers' accidents, daytime sleepiness (measured using the Epworth Sleepiness Scale) and other relevant physical characteristics. The drivers were sampled randomly at motorway service areas. The average age was 41.4 y (SD 10.5), they drove an average of 69700 miles annually (SD 36120), and their average score on the Epworth daytime sleepiness scale was 5.65 (SD 3.31). They reported an average accident liability of 0.26 accidents in a 3-y recall period. Drivers who reported snoring regularly whilst sleeping at night or who were obese or who had a noticeably large collar size had higher accident liabilities than those not exhibiting these characteristics. Accident liability increased with increasing scores on the Epworth daytime sleepiness scale. These findings suggest that further investigation of the mechanisms behind the higher accident rates of some categories of HGV drivers would be justified in the interests of road safety.

Waist and Neck Enlargement after Quadriplegia

Changes in waist and neck size in quadriplegic patients after paralysis, noted clinically, were assessed systematically. Twenty quadriplegic men, aged 60 +/- 13 years (mean +/- 1 SD) and 20 neurologically intact men, aged 63 +/- 17 years, selected by absence of weight gain, were questioned about changes in their waist and shirt collar sizes since the onset of paralysis (20 +/- 13 years) or during the previous 20 years for control subjects. Waist size expanded 7.0 +/- 0.3 inches for quadriplegic and 1.7 +/- 1.7 inches for control subjects (p < 0.001). Changes in neck size of 0.7 +/- 1.1 inches for quadriplegic and 0 +/- 0.7 inches for control subjects were found (p < 0.02). We conclude that quadriplegia is often followed by increased waist and neck size. These changes may relate to the impaired breathing mechanisms in quadriplegia.

Vertical Banded Gastroplasty with Adjustable Silicone Band: Preliminary Experience.

A series of ten patients operated on with vertical banded gastroplasty (VBG) with an adjustable silicone band at the outlet is presented. The loss of body weight and complication rate is evaluated. Preoperative mean excess overweight of the patients was 94% and mean BMI was 42.6. The loss of body weight at one year's follow-up was 38 kg or 59% of excess weight. Complications were one case of infection at the subcutaneous injection port and one case of a nonfatal pulmonary embolus. The results so far are thus comparable with VBG with a conventional fixed band, but the adjustable band actually simplifies the operative procedure since no exact calibration of the collar size is necessary at the time of surgery and should diminish the need for reoperations due to misalignment of collar size. The possibility of better weight control in the long-term perspective remains to be proven.

Use of cyclodextrins in isotachophoresis : IV. The influence of cyclodextrins on the chiral resolution of ephedrine alkaloid enantiomers

Using β-cyclodextrin and heptakis(2,6-di-O-methyl)-β-cyclodextrin as additives to the leading electrolyte in isotachophoresis, the complete chiral resolution of pseudoephedrine antipodes was achieved, but ephedrine enantiomers were not separated. Comparative measurements with β-cyclodextrin, its dimethyl and trimethyl derivatives, demonstrated that the changes in size and hydrophobicity of the cavity collar, caused by methoxylation, substantially alter the efficiency of chiral resolution. Optimization of the isotachophoretic conditions confirmed the significant influence of the cyclodextrin concentration and pH on the separation efficiency.

Predicting Bottomhole Assembly Performance

Summary A computer program for prediction of bottomhole assembly (BHA) performance has been developed. Input parameters include formation dip angle, hole and collar size, and stabilizer spacing. The predictions are in drilling terms: hole curvature, hole angle, weight on bit (WOB), etc. Results of extensive parametric studies and field use are presented.

Drill Collar Length is a Major Factor in Vibration Control

Dareing, Don W., SPE Summary Drill collar length directly affects the overall vibration response of drillstrings. Drill collar length is partly responsible for severe vibrations in hard rock drilling but can also be the solution to vibration control. This paper gives a new interpretation to the cause and control of drillstring vibrations and presents the results in terms of formulas that can be directly applied by the drilling engineer. Introduction It is standard practice to design the length of drill collars or bottomhole assemblies (BHA's) so that the neutral point is located in the collars. The neutral point is the point where compressive stress is equal to local hydrostatic pressure. The calculation is based on static forces only, including buoyant weight of the collars and static bit weight. One formula commonly used to calculate drill collar length is ...........................(1) According to this formula, the distance to the neutral point is 85 % of the total drill collar length, allowing for a margin of bit weight overload. Higher bit weights require longer BHA's. Natural frequencies and inertia loading in BHA's are not considered in this calculation. As a result, the present practice of calculating drill collar length often leads to natural tuning of the collars with bit displacement frequencies. This means that many drill collars are unintentionally designed to vibrate, and collar length selection, based on statics alone, may account for rough running. Drill collars can vibrate in three modes:axial or longitudinal,torsional, andtransverse or lateral. Because the collars are confined by the wellbore, lateral vibrations are not usually a major source of stress and are not covered in this paper. Drill collars are free to move axially and torsionally, and these two modes of vibration can become severe. Kelly bounce and whipping of the draw works cables indicate axial vibrations in drillstrings. Torsional vibrations are normally not seen from the rig floor because the rotary table drive tends to "fix" the vibrational angular motion at the surface. Nonetheless, large dynamic torque can be generated at the rotary table. As in any mechanical system, severe vibrations in drillstrings are the result of resonance or frequency tuning. Resonance exists when the frequency of the applied force is equal to a natural free vibration frequency. The drill collar section, however, controls the overall vibration response because its cross-sectional area is several times the cross-sectional area of drillpipe. The collars act as receivers and amplifiers of vibration energy from the drill bit. In one sense the drill collar section is the dog wagging the tail, which in this case is the drillpipe section. This observation, supported by calculations and field data, is explained further in the paper. Assumptions made in the analysis are as follows.1. The BHA is a constant-OD and -ID drill collar2. The drill bit is a roller cone rock bit.3. The formation is medium to hard.4. The natural frequency of damped free vibration of the BHA is not significantly different from its natural frequency of undamped free vibration.5. Axial and torsional stiffness of stabilizers do not significantly alter the natural modes and vibration.6. Hole inclination and curvature do not affect natural frequency of BHA's. One goal of the paper is to give alternative vibration control techniques for alleviating rough running. Shock absorbers are proved alternatives. Rough, running can also be alleviated by adjustments in BHA design. A third alternative is rotary speed selection, based on techniques given in the paper. Natural Frequency of Drill Collar Assembly BHA's are often made up of different sizes of drill collars, stabilizers, and downhole tools. In general, critical rotary speed should be based on the natural frequency of the composite BHA. For simplicity, the following discussion assumes the drill collar section has a uniform cross section from the bit to the collar/drillpipe interface and contains no downhole tools. It can be shown that the natural frequencies of BHA's made up of different collar sizes can be reasonably approximated by assuming uniform drill collars. An exception to this simplification is heavy drillpipe in tandem with drill collars. The natural frequencies of nonuniform BHA'S, however, can be calculated from classical vibration equations. In calculating natural frequencies for both axial and torsional modes, the drill collars are assumed fixed at the drillbit and free at the collar/drillpipe interface. The free constraint at the top of the collar section is based on relatively low dynamic force (or torque) applied to the top of the collars by drillpipe. JPT P. 637^

ANALYSIS AND DESIGN FOR LONGITUDINAL SHEAR IN COMPOSITE T-BEAMS.

Keywords WARWICK UNIVERSITY, UNIVERSITY COLLEGE CORK ANALYSIS, DESIGN, LONGITUDINAL, SHEAR, COMPOSITE, T BEAMS, RESEARCH, PUSH, TESTS, STUDS, BEAMS, MODES, FAILURES, SHANK, STUDIES, PARAMETRIC, LOADS, PREDICTION, METHODS, SPLITTING, STRENGTH, REINFORCED, CONCRETE, SLABS, STATIC, CONNECTORS, WELDS, COLLARS, STEEL, BEHAVIOUR, CONNECTIONS, PARTIAL, INTERACTION, FATIGUE, LIFE, FATIGUE LIFE, FRACTURE, EMBEDDED, PULL OUT, STIFFNESS, SPECIMENS, ASYMMETRICAL, REGRESSION, ULTIMATE, COMPUTERS, PROGRAMS, TENSILE, VOIDS, AXIAL, FORCES, TENSION, BASES, CALIBRATION, CUBES, UNIFORM, FLOW, DISTRIBUTION, TRIANGULAR, TRA... Show All

Drillstring Dynamics During Jar Operation

An analytical model, based on plane wave propagation through a distributed mass representation of the drillstring, has been developed to investigate jarring. Overpull, jar stroke, jar placement, and collar and pipe dimensions are related to predict impact time, speed, and force, along with stress history at the stuck point and impulse delivered to the stuck point. Introduction A drillstring stuck in a borehole can lead to an expensive recovery or sidetracking operation. If the string is stuck because of caving, plastic extrusion of the formation wall into the borehole, junk in the hole, or differential sticking, a drilling jar in the collar string can be activated in an attempt to free the drillstring by jarring. A modern drilling jar can be run routinely in the drillstring, so it is immediately available to jar the string free. Normally the jarring process is done several times. It may require 10 to 50 process is done several times. It may require 10 to 50 or more cycles to free the fish. About 10 to 15% of the time, the jar is unable to free the fish even after repeated jarring. In this case it is necessary to sidetrack. The location of the jar in the string usually is determined to maximize the life of the tool. In this study we show how different jar placements affect the stress history at the stuck point. Jarring provides a method for dynamically transferring strain energy from the drillstring above the jar to the stuck point of the collars below the jar.The jar contains a mechanism for internally releasing. and then re-engaging the tensile strained drillstring. Sufficient force is applied at the surface to bring the tension at the jar to the triggering value called "overpull." The amount of overpull must be below the maximum tensile force the drillpipe can withstand. After triggering, the released ends (called the hammer and anvil) are free to move toward each other. When their combined displacements are equal to the stroke of the jar, the hammer strikes the anvil. In the period between release and re-engagement, the collars above the jar are accelerated by converting strain energy from the drillpipe to kinetic energy of the upper collars. On re-engagement, some of this energy is transmitted to the stuck collars. The resultant force at the stuck point is a tensile force exceeding the initial overpull. If this force is great enough, the stuck string will slide during the period of the impulse and can be freed after a sufficient number of jar cycles.There are a number of parameters that influence the force and energy transmitted to the region of sticking. Some of these, such as collar size, pipe size, and maximum safe overpull are generally determined by the drillstring program and by material limitations. The collar string length and the position of the jar in the collar string are more flexible and offer a method to affect the jarring process. Also, jar stroke length can be evaluated to determine optimum values for new or improved jar designs. Although jars are widely employed, there appear to be no published studies that attempt to relate these or other published studies that attempt to relate these or other parameters to jarring effectiveness. Prior work in the parameters to jarring effectiveness. Prior work in the U.S. on jars has been concerned with the internal mechanics of the jar itself. Some analytical work has been done in Russia by Fershter. Of course the success of a jarring operation is dependent upon the nature of the sticking forces, which are largely unknown. JPT P. 1381

Neuroradiologic study of hamartomas of the tuber cinereum and hypothalamus.

Five cases, four histologically proven, of hamartoma of the tuber cinereum and hypothalamus in children are reported. The ages of the patients range from 2 to 12 years. Three cases had pubertas praecox, and in all of these the hamartoma was located in the basal cistern between the chiasm and pons and had a collar button shape and size typical of hamartoma of the tuber cinereum. In the third case, a huge calcified mass in the suprasellar region was initially thought to be craniopharyngioma. The fourth case had a hamartoma within the substance of the hypothalamus and presented with hyponatremia and temporal lobe seizures.

Technical Note—The Shirt Allocation Problem

A shirt manufacturer is given a total order by a multistore retailer and an allocation of shirts among stores. His problem is to determine how to distribute shirts to each store according to collar and sleeve size. The problem is formulated as an absolute value programming problem and practical methods for making allocations are presented.

New design for anterior unit-built porcelain prostheses

The disadvantages of breakage, gingival impingement, and poor esthetic contour associated with a unit-built porcelain prosthesis have been eliminated by employing a new design of the substructure frame. The substructure frame has been strengthened by the addition of a high lingual shoulder to prevent flexing of the metal and subsequent porcelain fracture. The solder joints have been relocated incisally, thus maintaining proximal space for greater gingival health. Also, the incisal location of the solder joint makes it possible to taper the proximal surfaces of the porcelain jackets toward the gingivae. This eliminates the proximal bulk which, previously, was necessary to hide the gingival solder joint and facilitates the fabrication of a porcelain unit-built restoration that not only encourages gingival health but is esthetic and lifelike as well. A new full-coverage preparation and a technique that facilitates two thirds reduction in the size of the labial gold collar have been suggested. The new substructure coping design also can be employed when a complete porcelain-fused-to-metal prosthesis is desired.

DETERMINATION OF TOTAL BODY FAT

Mammalian body represents the sum of 2 major components: the body fat which varies widely from individual to individual, and fat-free lean mass (FFLM), which is of relatively constant weight in a healthy individual and is of relatively constant composition. Since adipose tissues are metabolically active, knowledge of total body fat could add significance to studies in fat metabolism. Measuring body fat can provide a means of studying the water content of fat-free lean mass (FFLM), under conditions of abnormal hydration or nutrition, and the changes that may occur with age. Lesser and co-workers¹report on the use of cyclopropane, a relatively safe anesthetic gas and at the same time highly fat-soluble, for the determination of total body fat in an experiment in a closed circuit. The method of study was as follows: A circular rubber diaphragm with a central aperture somewhat less than collar size was slipped over