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In this paper, the aspects of gas-operated pressure balances that affect their performance are discussed. These aspects include both the features that make gas-operated pressure balances suitable for use as pressure standards and the factors that must be managed to achieve good performance. As key features, gas-operated pressure balances are pressure generators, have excellent relative short-term stability (~5 × 10−9) and long-term stability (~1 × 10−6), and can be used as primary standards. Factors to manage include harmonic oscillation of the piston in the cylinder, pressure balance temperature and operating height, and geometric imperfections. Three applications are used to illustrate the performance aspects of gas-operated pressure balances: a primary standard, a standard for differential pressure from 1000 Pa and a standard for absolute pressure from

We present a method of analysis for cross-floats between pressure balances. This analysis relates to the residual mass method of treating cross-float data in which the residual mass Me of one pressure balance is an unknown in the analysis, along with the effective area and the elastic distortion coefficient. Me is the effective mass of any unweighed parts of the piston and load and may include an equivalent mass for other forces on the piston such as oil surface tension. Two models for the analysis with the Me method are presented in a form suitable for linear least squares analysis: one for the calibration of a pressure balance and the other for the comparison of two reference pressure balances. This analysis is equivalent to the p-method when Me is known to be zero. Linear generalized least-squares estimation is shown to be convenient for the calculations. A pressure balance calibration is used to illustrate the analysis and the associated uncertainty evaluation.

This paper describes a pressure comparison, covering the range 25 MPa to 260 MPa, carried out between the CSIRO National Measurement Laboratory (NML, Australia) and the Measurement Standards Laboratory of New Zealand (MSL) in 1997 and 1999. A feature of each part of the comparison was the high-resolution Digiquartz pressure transducer used as the transfer standard. This small and relatively inexpensive transducer is easier to transport between countries than a bulky and heavy pressure balance. The measured performance of the transducer demonstrates that it can compare the pressure scales of each laboratory to a standard uncertainty of 2.3 kPa, which is much smaller than the uncertainties specified for each pressure scale. The results of both comparisons show that the two pressure scales agree to within their respective uncertainties, although the 1999 comparison produced a larger difference than the 1997 comparison. This may indicate a change in the pressure balance parameters or that the transducer performance is not yet fully characterized. An analysis is presented to show the relationship between the measured pressure difference and the parameters of each pressure balance.

Histologically, Dupuytren’s disease has been compared to the process of neoplasia because of fibroblast proliferation, recurrence, chromosomal abnormalities and antigenic profiles.However, a comparison of Dupuytren’s tissue with the granulation tissue formed in wound healing could be more valid. Histology reveals similarities in cell types, proliferation, vascularity and collagen morphology. Pharmacologically, both tissues have a similar range of agonist and antagonist responses. Biochemical analysis reveals new collagen synthesis, an increased ratio of type III to type I collagen, and similar changes of the ground substance in both processes.Considering such similarities perhaps it is possible to regard some of the models used for the investigation of wound healing and granulation tissue as the missing experimental “model” for the study of Dupuytren’s disease.Recently great strides have been made in the basic understanding of wound biology, and such a comparison might well provide novel therapeutic options for Dupuytren’s disease.

This paper describes the improvements that have been made to our measurement of the Newtonian gravitational constant (G) since our last published value of G in 1995. As a result of a new measurement of G made with the improved apparatus, we have discovered some second-order corrections that were omitted from the previous measurement. New values for G are presented; both from the latest measurement and a recalculated value from our previous measurement. Our latest values are G = 6.6742(7) × 10-11 m3 kg-1 s-2 for the most recent measurement and G = 6.6746(10) × 10-11 m3 kg-1 s-2 for the recalculated 1995 value. These two values agree to within their uncertainties.

A high resolution gauge is used to determine the change in effective area of a 250 MPa piston–cylinder unit as a function of jacket pressure. These changes are compared with values calculated using a finite element method. The results of the comparison revealed that the jacket pressure seals were applying unexpected forces to the cylinder outer diameter. These forces were modelled in the finite element calculations giving reasonable agreement. Further measurements were made after modifying the jacket seal mounting. The new results showed reasonable agreement at low operating pressures but large disagreement between theory and experiment as the operating pressure approached 250 MPa.

An analytic approach, based on thin-wall theory, to the analysis of simple piston-cylinder systems is presented. The deformation of the cylinder, the pressure profile in the gap between the piston and the cylinder and the flow of oil are determined. The theory is extended further to calculate the effective areas of both the simple and the controlled clearance piston-cylinder systems, taking into account the distortion of the piston. The application of this work to thick-walled systems is discussed.

This paper describes the design and testing of a method to measure the Newtonian gravitational constant G. The method uses a torsion balance in which a small cylindrical mass is suspended from a slender fibre. Two large cylindrical masses produce a gravitationally induced torque on the small mass. This induced torque is balanced by the electrostatic torque produced by an electrometer. A servo-control system adjusts the electrostatically induced torque so that the fibre does not twist during the measurement. The torque produced by the electrometer is calibrated by an acceleration method that uses torques much larger than those produced by the gravitational attraction of the large masses. Other features of the method include a reduction in sensitivity of the measurement to density variations in the suspended mass, a measurement strategy which reduces the effect of drift in the measurement and computer control of the measurement. Preliminary measurements of the terms used to calculate G showing an uncertainty of 2,5 parts in 104 can currently be achieved. The limiting factor at present is the variation in the gravitational potential seen as the apparatus accelerates. Indications are that further modifications and measurements will provide a value of G with an uncertainty of about 1 part in 104.

The design and construction of a small compact autocollimator based on the laser head of a compact disc player is described. The instrument provides a cheap and simple means of measuring angles over a total angular range of 1200 mu rad ( approximately 200 arcsec) with a resolution of better than +or-0.006 mu rad. The 100 mu rad central region of the measurement range is linear to better than 2%. The autocollimator head is compact and can operate over long distances and with high ambient lighting. The unit described can, with a single measurement head, be used to simultaneously measure angles in two orthogonal directions.

An analytic approach, based on thin-wall theory, to analysis of the "controlled clearance" method of restricting the gap between a shaft and a surrounding cylinder is presented. A modified form of thin-wall theory allows this analysis to be extended to seals with outside to inside diameter ratios up to 2.3. The effects of (a) the supply pressure, the jacket pressure, the pressure dependence of the viscosity of the oil and the geometry of the system on (b) the deformation of the cylinder, the pressure profile in the gap between the shaft and the cylinder and the flow of oil are illustrated. A path using this information is given for the design of a controlled clearance seal. It is shown that when the jacket pressure and the supply pressure are equal (reentrant cylinder condition) the supply pressure needed to close the gap is infinite. The difference between this result and that for a cylinder with a built-in end, for which the supply pressure for closure is finite, is discussed. Experimental tests are described and the results are shown to agree with computed figures based on the theory. This work is of particular relevance to hydraulically actuated standards of pressure and force, where "simple" piston-cylinder assemblies suffer excessive deformations at pressures beyond 50 MPa.

This Letter presents the results of a series of measurements of the Newtonian gravitational constant $G$ using the compensated torsion balance developed at the Measurement Standards Laboratory. Since our last published result using the torsion balance in the compensated mode of operation [Meas. Sci. Technol. 10, 439 (1999)], several improvements have been made to reduce the uncertainty in the final result. The new measurements have used both stainless steel and copper large masses. The values of $G$ for the two sets of masses are in good agreement. After combining all of the measurements we get a value of $G=6.673\text{ }87(0.000\text{ }27)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\text{ }\text{ }{\mathrm{m}}^{3}\text{ }{\mathrm{k}\mathrm{g}}^{\ensuremath{-}1}\text{ }{\mathrm{s}}^{\ensuremath{-}2}$. This new value is 5 parts in ${10}^{5}$ smaller than our previous published values.

We determine whether urinary diary values are stable over time among women without lower urinary tract symptoms.Women without lower urinary tract symptoms completed a 24-hour log of fluid intake and volumes voided during June/July 2001 and again during February/March 2002. Initial and repeat diaries were compared using Wilcoxin signed rank tests, considered significant at the 5% level.A total of 137 subjects completed both diaries. Subjects voided a median of 8 times per 24 hours during the first and 7 per 24 hours during the second diary with 95% of subjects recording fewer than 13 voids per 24 hours during both diaries. Nighttime voids were recorded by 59 (43%) subjects during the first and 54 (39%) during the second diary. Urinary frequency and total urine volume were significantly greater during the first than second diary (Z = 2.1, p = 0.03 and Z = 3.3, p = 0.001, respectively). No significant differences in mean voided volume, maximum voided volume, voids per liter intake, total intake, or daytime or nighttime diuresis rates were found when the groups were compared. However, there were large individual differences in all diary variables.While there is large individual variation in diary values, pooled data from 24-hour urinary diaries concerning voids per liter intake, and mean and maximum voided volumes remain stable. Pooled data concerning raw urinary frequency and urine volumes may vary significantly without any treatment. When urinary frequency is of interest, the number of voids per liter intake may represent the most stable measure.

To explore the in vivo characteristics of donor fascia used in urogynaecological procedures, in a canine model.Two experiments were conducted. In the first, donor fascia grafts were obtained from 12 dogs, the grafts freeze-dried and half were irradiated. The grafts were used for sacrocolpopexy and suburethral slings in each of five dogs. The dogs were killed at 2, 6 and 12 weeks after graft implantation, the grafts retrieved and assessed using tensilometry. In the second experiment, unirradiated sacrocolpopexy grafts were implanted in eight dogs; four grafts were placed under no tension and four under moderate tension. At 8 weeks, the grafts were retrieved and assessed by tensilometry. Measures of strength in both experiments included the ultimate tensile strength, ultimate strain and stiffness. All measures were compared using Kruskal-Wallis nonparametric tests in both studies.In the first experiment, a significant minority (23%) of grafts had complete loss of strength. Measures of graft strength did not vary when analysed according to donor dog, host dog, history of graft irradiation, duration of implantation or location of graft. In the second experiment, grafts placed under no tension tended to have lower tensile strength (chi2(1) = 3.125, P = 0.077), lower stiffness (chi2(1) = 3.125, P = 0.077) and lower ultimate strain (chi 2(1) = 3.182, P = 0.074).Graft irradiation as an isolated variable did not predispose grafts to failure in vivo. Biomechanical factors at the implantation site are likely to play a critical role in determining ultimate graft strength.

Transient postoperative urinary retention after stress incontinence surgery is common, and there is no widely accepted method of hastening the return to normal voiding. The etiology of this retention is poorly understood. Failure of the relaxation of the striated external urethral sphincter has been proposed as an etiologic agent, but has not been documented. Ten patients about to undergo a Burch colposuspension or sub-urethral sling, who demonstrated normal preoperative voiding, were recruited to a study of postoperative retention. Hook-wire electromyographic (EMG)probes were placed into the external urethral sphincter while the patients were under anesthesia, and a suprapubic catheter was placed. We performed instrumented voiding trials 1 or 2 days after surgery while continuously recording urethral EMG and intravesical pressure. Two patients demonstrated normal voiding. Two patients were able to void but demonstrated no EMG silencing. Six patients were unable to void and demonstrated persistent EMG activity. Four of these demonstrated no detrusor contraction, whereas two demonstrated detrusor contractions. All patients resumed normal voiding by clinical parameters within 14 days of surgery. Our study supports other research that suggests that failure of relaxation of the striated urethral sphincter contributes to postoperative urinary retention.

The aim of this study was to document the relative proportions of two isoforms of myosin heavy chain in detrusor smooth muscle of women with detrusor overactivity and in asymptomatic controls. Women aged 35-65 with documented detrusor overactivity and without a history of neurologic disease, prior incontinence surgery, elevated post-void residual urine volume, or indwelling urinary catheter were eligible for the study. Full-thickness biopsies of extraperitoneal bladder dome were obtained at the time of laparotomy in six patients with documented detrusor overactivity and in a control group of eight continent patients. Biopsies were frozen in liquid nitrogen, crushed with a frozen mortar and pestle at -80 degrees C, and homogenized in buffer, and the extracts were electrophoresed on 6% polyacrylamide sodium dodecyl sulfate gels and stained with Coomassie blue. The gels were de-stained and then the protein bands were scanned with a densitometer. The mean patient age was 48 years (range, 36-59). Seven patients were Caucasian and seven patients were African American. Detrusor smooth muscle contains a mean of 34% (range, 27-43%) SM1 and 66% (range, 57-73%) SM2 isoforms. There was no difference in isoform composition when patients were compared according to urogynecologic diagnosis or according to race. In detrusor biopsies from women, approximately 34% of myosin is of the SM1 isoform and approximately 66% is of the SM2 isoform. This ratio is relatively constant in the two races studied and unchanged in women with detrusor overactivity. Animal models utilizing outlet obstruction of the bladder to provoke detrusor instability and detrusor hypertrophy are known to alter myosin isoform distribution and may not be appropriate models of detrusor instability in human females.

The use of bone anchors as a superior fixation for suburethral slings is becoming popular. We present a case report of pubic osteomyelitis and granuloma after bone anchor placement. A 71-year-old woman underwent placement of a vaginal wall sling using pubic bone anchors placed through a suprapubic incision. Recurrent swelling of the mons pubis required re-exploration and removal of the anchors from an infected pubic bone. When symptoms persisted over the following 10 months, the patient underwent repeat surgery and excision of a pubic bone granuloma. The use of bone anchors in suburethral sling surgery is associated with possible increase in patient morbidity, and no benefit to the patient has been shown.

To report our experience of using freeze-dried irradiated fascia lata allografts for suburethral sling procedures.Between December 1996 and September 1998, 35 patients (mean age 60.25 years, range 37-79) underwent suburethral sling placement with fascia allograft. These patients were reviewed, with the findings at the time of any surgical re-exploration. Eleven (31%) had undergone prior surgery for genuine stress incontinence and 32 (91%) had a preoperative diagnosis of intrinsic sphincter deficiency.On re-operation for persistent or recurrent stress incontinence, the allograft was present but grossly degenerated in two (6%) patients and completely absent in five (14%) patients. Histology of a retrieved graft fragment showed both fibroblast proliferation and degeneration within the graft.The use of freeze-dried, irradiated fascia lata for suburethral sling procedures was associated with a material failure rate of/=20%. We caution against its use in this setting.

This study sought to determine whether a normal platelet count is a reliable predictor of the absence of other coagulation abnormalities in patients with a hypertensive disorder of pregnancy. A retrospective review of laboratory data obtained from 80 patients with hypertensive disorders of pregnancy was carried out. Results of complete blood cell count, prothrombin time (PT), partial thromboplastin time (PTT), D-dimer, fibrin split products, and fibrinogen, bilirubin, and liver enzyme levels were reviewed. Minor abnormalities of PT, PTT, and fibrinogen level were frequent, even in the presence of a normal platelet count. These were found mostly in patients with severe pre-eclampsia. A baseline complete blood cell count including platelet count is probably sufficient in patients with a hypertensive disorder of pregnancy. Fibrinogen level and PT and PTT determinations are recommended in patients who have severe preeclampsia and for whom operative delivery or regional anesthesia is planned. This will detect minor abnormalities in a few patients despite a normal platelet count. This information may help prevent bleeding complications.

The potential for the widespread use of cultured keratinocytes for burns treatment is handicapped by practical problems such as fragility, poor take and, often, unsatisfactory cosmesis. Although dermal equivalents reduce these problems there remains a lack of consensus on what is the best structure of such equivalents. At present the commonest support is type I collagen. This histological study, however, using Herovici's stain, clearly shows that in human skin from a variety of anatomical sites the epidermis is not in direct contact with type I collagen but rather with a distinct layer of type III collagen. We suggest that dermal equivalents may have to be constructed so as to include a layer of type III collagen at the interface between the keratinocytes and a type I collagen neo-dermis, so mimicking normal skin structure more closely.

Renal tract neoplasms account for only 15% of all cases of hematuria and are rare before the age of 40. Few cases of bladder carcinoma diagnosed during pregnancy have been reported.Adenocarcinoma of the dome of the bladder caused hematuria beginning at 20 weeks' gestation but was not diagnosed until the postpartum period.Hematuria during pregnancy is usually associated with infection. However, neoplasms must be included in the differential diagnosis.

At the beginning of the seventeenth century, some surgeons were as interested in the classification, prognosis and treatment of burns as their successors are at the close of the twentieth century. We present extracts from our translation of the visionary treatise on Burns by Fabricius Hildanus (Wilhelm Fabry), the "Father of German surgery", and show how some of the present day approaches to burns have their origins almost 400 years ago.

Although the histology of Dupuytren’s tissue is well-documented, conventional stains do not distinguish between the different types of collagen which biochemistry and immunochemistry suggest are present. Dupuytren’s specimens [nodules ( n = 26), cords ( n = 15) and dermofasciectomies ( n = 6)] were stained with haematoxylin and eosin, Van Gieson’s, Mallory’s, Masson’s, and Herovici’s picropolychrome stain, and examined for both cellularity and collagen staining characteristics. All stains illustrated the marked cellularity of the nodules, contrasting with a paucity of cells within the cords. The first four stains demonstrated uniformity of the collagen staining within the tissues. Herovici’s picropolychrome, however, showed distinct staining patterns for the dermis, nodules and cords, with both purple/red and blue areas. Other studies suggest that those fibres stained purple/red and blue are types I and III collagens respectively. These findings may shed further light on the tissue of origin of Dupuytren’s disease.

The fidelity of DNA synthesis by an exonuclease-proficient DNA polymerase results from the selectivity of the polymerization reaction and from exonucleolytic proofreading. We have examined the contribution of these two steps to the fidelity of DNA synthesis catalyzed by the large Klenow fragment of Escherichia coli DNA polymerase I, using enzymes engineered by site-directed mutagenesis to inactivate the proofreading exonuclease. Measurements with two mutant Klenow polymerases lacking exonuclease activity but retaining normal polymerase activity and protein structure demonstrate that the base substitution fidelity of polymerization averages one error for each 10,000 to 40,000 bases polymerized, and can vary more than 30-fold depending on the mispair and its position. Steady-state enzyme kinetic measurements of selectivity at the initial insertion step by the exonuclease-deficient polymerase demonstrate differences in both the Km and the Vmax for incorrect versus correct nucleotides. Exonucleolytic proofreading by the wild-type enzyme improves the average base substitution fidelity by 4- to 7-fold, reflecting efficient proofreading of some mispairs and less efficient proofreading of others. The wild-type polymerase is highly accurate for -1 base frameshift errors, with an error rate of less than or equal to 10(-6). The exonuclease-deficient polymerase is less accurate, suggesting that proofreading also enhances frameshift fidelity. Even without a proofreading exonuclease, Klenow polymerase has high frameshift fidelity relative to several other DNA polymerases, including eucaryotic DNA polymerase-alpha, an exonuclease-deficient, 4-subunit complex whose catalytic subunit is almost three times larger. The Klenow polymerase has a large (46 kDa) domain containing the polymerase active site and a smaller (22 kDa) domain containing the active site for the 3'----5' exonuclease. Upon removal of the small domain, the large polymerase domain has altered base substitution error specificity when compared to the two-domain but exonuclease-deficient enzyme. It is also less accurate for -1 base errors at reiterated template nucleotides and for a 276-nucleotide deletion error. Thus, removal of a protein domain of a DNA polymerase can affect its fidelity.

We are investigating the mechanisms by which mutations are produced or avoided during DNA synthesis. Using in vitro fidelity assays, we have defined the error frequency and mutational specificity of the replicative animal cell DNA polymerases (alpha and delta). With DNA polymerase alpha or the four-subunit DNA polymerase alpha-DNA primase complex, neither of which contains detectable associated exonuclease activity, the fidelity of the polymerization step is low relative to spontaneous mutation rates in vivo. DNA polymerase delta is much more accurate, partly due to proofreading by the 3'----5' exonuclease activity associated with this polymerase. These fidelity studies have been extended to the replication apparatus present in extracts of human HeLa cells. The replication complex is highly accurate, suggesting that additional fidelity components are operating in the extract during bidirectional, semiconservative replication of double-stranded DNA. Nevertheless, in highly sensitive reversion assays, base substitution errors can be readily detected at frequencies greater than the estimated rate of spontaneous mutation in vivo. This suggests that fidelity components may be missing and/or that human cells depend heavily on postreplicative repair processes to correct replication errors.

While present data suggest that the Mutatox assay is not effective for carcinogen screening, it does appear to detect many agents with diverse mechanisms of mutagenic activity with reasonable sensitivity as well as some known human teratogens. For general screening, more detailed studies need to be performed using coded agents with various mutagenic mechanisms as well as with toxicants of various classes including teratogens. With additional validation, the Mutatox assay, with its sensitivity to diverse chemical classes, may be valuable as a rapid, short-term, cost-effective assay.

A key comparison of low differential pressure standards, organized under the auspices of the Consultative Committee for Mass and Related Quantities (CCM), was carried out at four national metrology institutes (NMIs) between July 1998 and May 1999 in order to determine the degrees of equivalence of the standards at pressures in the range 1 Pa to 1000 Pa. The differential pressures were superimposed on a line pressure of nominally 100 kPa. The primary standards, which represent two principal measurement methods, included three liquid-column manometers and one double pressure balance. The transfer standard package consisted of four high-precision pressure transducers: two capacitance diaphragm gauges to provide high resolution at low differential pressures, and two resonant silicon gauges to provide the required calibration stability. Two nominally identical transfer packages were used to reduce the time required for the measurements, with Package A being circulated among laboratories in the European region (Istituto di Metrologia G. Colonnetti, Italy; National Physical Laboratory, UK) and Package B in the Asia-Pacific region (Measurement Standards Laboratory of New Zealand). The results obtained were normalized using data obtained from simultaneous calibrations of the two packages at the pilot laboratory (National Institute of Standards and Technology, USA). The degrees of equivalence of the measurement standards were determined in two ways: deviations from key comparison reference values and pairwise differences between these deviations. The differential pressure standards of the participants were generally found to be equivalent and the results revealed no significant relative bias between the two principal methods tested.

Studies of the rotation curve of our Galaxy at galactocentric radii, R, greater than the solar distance, Ro, from the center require the use of conventional optical techniques since the distances to as well as the radial velocities of Population I objects are needed.