Inflow boundary profile prescription for numerical simulation of nasal airflow

Knowledge of how air flows through the nasal passages relies heavily on model studies, as the complexity and relative inaccessibility of the anatomy prevents detailed in vivo measurement. Almost all models to date fail to incorporate the geometry of the external nose, instead employing a truncated inflow. Typically, flow is specified to enter the model domain either directly at the nares (nostrils), or via an artificial pipe inflow tract attached to the nares. This study investigates the effect of the inflow geometry on flow predictions during steady nasal inspiration. Models that fully replicate the internal and external nasal airways of two anatomically distinct subjects are used as a reference to compare the effects of common inflow treatments on physiologically relevant quantities including regional wall shear stress and particle residence time distributions. Inflow geometry truncation is found to affect flow predictions significantly, though slightly less so for the subject displaying more pronounced passage area contraction up to the internal nasal valve. For both subject geometries, a tapered pipe inflow provides a better approximation to the natural inflow than a blunt velocity profile applied to the nares. Computational modelling issues are also briefly outlined, by comparing quantities predicted using different surface tessellations, and by evaluation of domain-splitting techniques.

Practice observed: is speculum examination on admission a necessary procedure in the management of all cases of antepartum haemorrhage?

The objective of the study was to determine the justification or otherwise of admission speculum examination in women presenting with antepartum haemorrhage and the outcome/ benefits of the practice on women with antepartum haemorrhage presenting to the delivery suite of a UK teaching hospital. Factors studied included gestational age at presentation, associated factors with the bleeding, grade of medical/ midwifery staff performing the admission speculum examination, findings on speculum examination and ultrasound scan and the overall pregnancy outcome. Of the 564 (4.9%) women who presented with antepartum haemorrhage; 521 had an admission speculum examination; 94.4% of these were by senior house officers (SHOs). The findings were a normal cervix (69%) and ectopy (21.3%). Of the women, 14.4% had recurrent bleeding and 8.5% went into preterm labour. The complications of the pregnancies, timing of delivery and management were independent of speculum examination. Admission speculum examination did not influence the management of pregnancies and the complications thereafter. These results suggest that such an intrusive procedure may not be justifiable in women presenting with antepartum haemorrhage.

Assessment of subclinical venous catheter-related diseases in horses and associated risk factors

A total of 102 horses that had a catheter introduced intravenously to facilitate treatment had the catheterised jugular vein and contralateral vein examined by ultrasound every 48 hours. Subclinical complications were defined by thrombus formation or thickening of the venous wall, and the data were analysed to establish risk factors for the development of these complications. The horses with a rectal temperature above 38.5 degrees C when the catheter was introduced were four times more likely to develop complications, than the horses with a lower temperature. The administration of a NSAID while the catheter was in place reduced the risk of complications developing.

The cytoplasmic 60 kDa progesterone receptor isoform predominates in the human amniochorion and placenta at term

BACKGROUND

The mechanism that initiates human parturition has been proposed to be 'functional progesterone withdrawal' whereby the 116 kDa B-isoform of the progesterone receptor (PR-B) switches in favour of the 94 kDa A-isoform (PR-A) in reproductive tissues. Recently, other PR isoforms, PR-S, PR-C and PR-M generated from the same gene have been identified and partially characterised.

METHODS AND RESULTS

Using immunohistochemical, western blotting and RT-PCR techniques, evidence is provided that indicates the major PR isoform present in human term fetal membranes (amnion and chorion) and syncytiotrophoblast of the placenta is neither of the classical nuclear PR-B or PR-A isoforms but is the N-terminally truncated 60 kDa PR-C isoform. Evidence is also provided that this 60 kDa isoform resides in the cytoplasm of the expressing cell types. Data are also presented to show that PR-B, PR-A and PR-S isoforms are essentially absent from the amnion and chorion, whereas PR isoforms A, B, C and S are all present in the decidua, with PR-A being the major isoform. The syncytiotrophoblast of the placenta contains the cytoplasmic 60 kDa isoform, but not isoforms PR-A, PR-B or PR-S.

CONCLUSION

The major PR isoform in the amnion, chorion and placenta is a 60 kDa protein that could be PR-C, suggesting that the cytoplasmic isoform has a specific role in extra-embryonic tissues and may be involved in the regulation of human parturition.

Assessing techniques for disinfecting sites for inserting intravenous catheters into the jugular veins of horses

The sites of insertion of catheters into the jugular veins of six horses were investigated to determine common isolates and to assess the effectiveness of two disinfection protocols with the hair coat left long, clipped or shaved. Skin commensals (Staphylococcus, Streptococcus and Micrococcus species) and environmental contaminants (Bacillus, Enterobacteriaceae, Aspergillus and Mucor species) were the microorganisms most frequently isolated. Chlorhexidine gluconate and povidone-iodine-based skin disinfection protocols resulted in significant reductions in the number of bacterial isolates from clipped sites. With chlorhexidine, there were no significant differences between the reductions observed at sites with the hair coat left long, clipped or shaved.

Use of antibiotics for the treatment of preterm parturition and prevention of neonatal morbidity: a metaanalysis

OBJECTIVE

We conducted a metaanalysis to determine whether antibiotics prolong pregnancy and reduce neonatal morbidity in preterm premature rupture of membranes (PPROM) and preterm labor (PTL) at 34 weeks or less.

STUDY DESIGN

Randomized trials comparing antibiotic therapy with placebo in PPROM or PTL at a gestation of 34 weeks or less were retrieved. The primary outcome was time to delivery (latency). Infant outcomes included mortality, infection, neurological abnormality, respiratory disease, and neonatal stay.

RESULTS

Antibiotics were associated with prolongation of pregnancy in PPROM (P < .01) but not PTL. Clinically diagnosed neonatal infections were reduced in both groups; there was a trend toward reduced culture-positive sepsis in PPROM. Intraventricular hemorrhage (all grades) was reduced in PPROM. Other neonatal outcomes were unaffected by antenatal antibiotics.

CONCLUSION

Antibiotics prolong pregnancy and reduce neonatal morbidity in women with PPROM at a gestation of 34 weeks or less. In PTL at a gestation of 34 weeks or less, there is little evidence of benefit from administration of antibiotics.

Childhood outcomes after prescription of antibiotics to pregnant women with preterm rupture of the membranes: 7-year follow-up of the ORACLE I trial

BACKGROUND

The ORACLE I trial compared the use of erythromycin and/or amoxicillin-clavulanate (co-amoxiclav) with that of placebo for women with preterm rupture of the membranes without overt signs of clinical infection, by use of a factorial randomised design. The aim of the present study--the ORACLE Children Study I--was to determine the long-term effects on children of these interventions.

METHODS

We assessed children at age 7 years born to the 4148 women who had completed the ORACLE I trial and who were eligible for follow-up with a structured parental questionnaire to assess the child's health status. Functional impairment was defined as the presence of any level of functional impairment (severe, moderate, or mild) derived from the mark III Multi-Attribute Health Status classification system. Educational outcomes were assessed with national curriculum test results for children resident in England.

FINDINGS

Outcome was determined for 3298 (75%) eligible children. There was no difference in the proportion of children with any functional impairment after prescription of erythromycin, with or without co-amoxiclav, compared with those born to mothers who received no erythromycin (594 [38.3%] of 1551 children vs 655 [40.4%] of 1620; odds ratio 0.91, 95% CI 0.79-1.05) or after prescription of co-amoxiclav, with or without erythromycin, compared with those born to mothers who received no co-amoxiclav (645 [40.6%] of 1587 vs 604 [38.1%] of 1584; 1.11, 0.96-1.28). Neither antibiotic had a significant effect on the overall level of behavioural difficulties experienced, on specific medical conditions, or on the proportions of children achieving each level in reading, writing, or mathematics at key stage one.

INTERPRETATION

The prescription of antibiotics for women with preterm rupture of the membranes seems to have little effect on the health of children at 7 years of age.

FUNDING

UK Medical Research Council.

Childhood outcomes after prescription of antibiotics to pregnant women with spontaneous preterm labour: 7-year follow-up of the ORACLE II trial

BACKGROUND

The ORACLE II trial compared the use of erythromycin and/or amoxicillin-clavulanate (co-amoxiclav) with that of placebo for women in spontaneous preterm labour and intact membranes, without overt signs of clinical infection, by use of a factorial randomised design. The aim of the present study--the ORACLE Children Study II--was to determine the long-term effects on children after exposure to antibiotics in this clinical situation.

METHODS

We assessed children at age 7 years born to the 4221 women who had completed the ORACLE II study and who were eligible for follow-up with a structured parental questionnaire to assess the child's health status. Functional impairment was defined as the presence of any level of functional impairment (severe, moderate, or mild) derived from the mark III Multi-Attribute Health Status classification system. Educational outcomes were assessed with national curriculum test results for children resident in England.

FINDINGS

Outcome was determined for 3196 (71%) eligible children. Overall, a greater proportion of children whose mothers had been prescribed erythromycin, with or without co-amoxiclav, had any functional impairment than did those whose mothers had received no erythromycin (658 [42.3%] of 1554 children vs 574 [38.3%] of 1498; odds ratio 1.18, 95% CI 1.02-1.37). Co-amoxiclav (with or without erythromycin) had no effect on the proportion of children with any functional impairment, compared with receipt of no co-amoxiclav (624 [40.7%] of 1523 vs 608 [40.0%] of 1520; 1.03, 0.89-1.19). No effects were seen with either antibiotic on the number of deaths, other medical conditions, behavioural patterns, or educational attainment. However, more children whose mothers had received erythromycin or co-amoxiclav developed cerebral palsy than did those born to mothers who received no erythromycin or no co-amoxiclav, respectively (erythromycin: 53 [3.3%] of 1611 vs 27 [1.7%] of 1562, 1.93, 1.21-3.09; co-amoxiclav: 50 [3.2%] of 1587 vs 30 [1.9%] of 1586, 1.69, 1.07-2.67). The number needed to harm with erythromycin was 64 (95% CI 37-209) and with co-amoxiclav 79 (42-591).

INTERPRETATION

The prescription of erythromycin for women in spontaneous preterm labour with intact membranes was associated with an increase in functional impairment among their children at 7 years of age. The risk of cerebral palsy was increased by either antibiotic, although the overall risk of this condition was low.

FUNDING

UK Medical Research Council.

Expression of the endocannabinoid system in human first trimester placenta and its role in trophoblast proliferation

The endocannabinoid, anandamide, which binds to two major receptor proteins, the cannabinoid receptors (CBs) 1 and 2 (CB1 and CB2), has been shown to play a role in first trimester miscarriage possibly through impairment of the developing trophoblast. Although the precise molecular mechanisms underlying this are unknown, plasma anandamide levels are known to be regulated by the progesterone-induced enzyme, fatty acid amide hydrolase (FAAH). Here, we tested the hypothesis that temporal-spatial expression of FAAH, CB1, and CB2 is regulated during early pregnancy and that anandamide detrimentally alters trophoblast proliferation. Transcripts for CB1, CB2, and FAAH were demonstrated in first trimester trophoblast extracts with only the CB1 transcript being significantly regulated. The significant 4.7-fold increase in expression at wk 10 gestation was reduced to 8.9% of the peak value by wk 12. Transcripts for CB2 showed a similar pattern of expression but were not significantly induced. By contrast, FAAH transcript levels appeared to increase toward the end of the first trimester, but again did not reach significance. These observations were supported by immunohistochemical studies that demonstrated a similar pattern of expression at the protein level, with cellular localization for all three proteins concentrated within the syncytiotrophoblast layer. Anandamide also prevented BeWo trophoblast cell proliferation in a dose-dependent manner, with a 50-60% significant inhibition of cell proliferation with concentrations in excess of 3 mum. This effect was mediated through CB2. Together, these data provide insights into how elevated plasma anandamide levels increase the risk of first trimester miscarriage.

Factors associated with cross-contamination of hides of Scottish cattle by Escherichia coli O157

The putative source of hide contamination for 236 cattle in Scotland followed from the farm through to slaughter was determined using phage and verocytotoxin type data. The majority of cattle (84%) were found to have subtypes of Escherichia coli O157 on their hide that had not been found previously in any animal from the farm of origin, strongly suggesting that contamination occurred once animals had left the farm of origin. Using logistic regression analysis, several variables and factors were found to be strongly associated (P < 0.01) with cross-contamination of cattle hides at the univariate level; commercial transport to slaughter, transport with other animals, use of a crush, line automation, and increasing slaughterhouse throughput were all risk factors, while feeding hay in lairage, processing an animal earlier in a slaughter cohort, and cleaning the landing area poststunning were protective. In the multivariable model, with the slaughterhouse and the farm group included as random effects, factors associated with the cross-contamination of cattle hides were identified. Transport to the slaughterhouse by a commercial hauler had a borderline-significant association with increased odds of an animal having a cross-contaminated hide (odds ratio [OR] [95% confidence interval (CI)] = 5.7 [0.99, 33.0]; P = 0.05). At the slaughterhouse, providing hay to cattle waiting in lairage (OR [95% CI] = 0.04 [<0.01, 1.04]; P = 0.05) and cleaning the landing area (OR [95% CI] = 0.03 [<0.01, 1.15,]; P = 0.06) also had a borderline-significant association with decreased odds of an animal having a cross-contaminated hide. Although the prevalence of carcass contamination remains very low, targeted intervention at the preslaughter stage may have the potential to reduce further the risk to public health.

Nasal architecture: form and flow

Current approaches to model nasal airflow are reviewed in this study, and new findings presented. These new results make use of improvements to computational and experimental techniques and resources, which now allow key dynamical features to be investigated, and offer rational procedures to relate variations in anatomical form. Specifically, both replica and simplified airways of a single subject were investigated and compared with the replica airways of two other individuals with overtly differing geometries. Procedures to characterize and compare complex nasal airway geometry are first outlined. It is then shown that coupled computational and experimental studies, capable of obtaining highly resolved data, reveal internal flow structures in both intrinsically steady and unsteady situations. The results presented demonstrate that the intimate relation between nasal form and flow can be explored in greater detail than hitherto possible. By outlining means to compare complex airway geometries and demonstrating the effects of rational geometric simplification on the flow structure, this work offers a fresh approach to studies of how natural conduits guide and control flow. The concepts and tools address issues that are thus generic to flow studies in other physiological systems.

Mechanics of airflow in the human nasal airways

The mechanics of airflow in the human nasal airways is reviewed, drawing on the findings of experimental and computational model studies. Modelling inevitably requires simplifications and assumptions, particularly given the complexity of the nasal airways. The processes entailed in modelling the nasal airways (from defining the model, to its production and, finally, validating the results) is critically examined, both for physical models and for computational simulations. Uncertainty still surrounds the appropriateness of the various assumptions made in modelling, particularly with regard to the nature of flow. New results are presented in which high-speed particle image velocimetry (PIV) and direct numerical simulation are applied to investigate the development of flow instability in the nasal cavity. These illustrate some of the improved capabilities afforded by technological developments for future model studies. The need for further improvements in characterising airway geometry and flow together with promising new methods are briefly discussed.

Experimental investigation of nasal airflow

The airway geometry of the nasal cavity is manifestly complex, and the manner in which it controls the airflow to accomplish its various physiological functions is not fully understood. Since the complex morphology and inaccessibility of the nasal passageways precludes detailed in-vivo measurements, either computational simulation or in-vitro experiments are needed to determine how anatomical form and function are related. The fabrication of a replica model of the nasal cavity, of a high optical clarity and derived from in-vivo scan data is described here, together with characteristics of the flow field investigated using particle image velocimetry (PIV) and flow visualization. Flow visualization is shown to be a capable and convenient technique for identifying key phenomena. Specifically the emergence of the jet from the internal nasal valve into the main cavity, how it impacts on the middle turbinate, and the large enhancement of dispersion that accompanies the initial appearance of flow instability are revealed as particularly significant features. The findings from the visualization experiments are complemented by PIV imaging, which provides quantitative detail on the variations in velocity in different regions of the nasal cavity. These results demonstrate the effectiveness of the cavity geometry in partitioning the flow into high shear zones, which facilitate rapid heat transfer and humidification from the nasal mucosa, and slower zones affording greater residence times to facilitate olfactory sensing. The experimental results not only provide a basis for comparison with other computational modelling but also demonstrate an alternative and flexible means to investigate complex flows, relevant to studies in different parts of the respiratory or cardiovascular systems.

Risk factors for hide contamination of Scottish cattle at slaughter with Escherichia coli O157

In the slaughter processing of cattle, contaminated hides have been identified as one of the major sources of Escherichia coli O157 carcase contamination. Logistic regression analysis was applied to data collected in a large scale study in Scotland involving 222 cattle forming 34 groups sent for slaughter from 30 farms to 10 slaughterhouses. Aspects of individual animal characteristics, farm management practices and slaughterhouse features were examined to identify potential risk factors for hide contamination at harvest. Two models were developed, the first in which slaughterhouse was modelled as a fixed effect, and a second model where slaughterhouse and farm groups were modelled as random effects. In the first model, there was a significantly increased risk of a carcase testing positive for E. coli O157 on the hide if either the hide of the carcase immediately before or after it on the line was contaminated (OR 3.6; 95% CI: 1.4-9.9). If both adjacent carcases had contaminated hides, the odds ratio for the study carcase having a contaminated hide rose to 11.5 (95% CI: 4.4-32.5). If animals were held in lairage, receiving hay as feed appeared to have a protective effect on hide contamination. Transportation to the slaughterhouse by haulier, as opposed to transport by the farmer, was associated with a 5.4 increase in the odds of E. coli O157 contamination. The use of a crush in the lairage, often employed when reading ear tags, was also found to significantly increase the odds of hide contamination with E. coli O157. In the second model, the inclusion of slaughterhouse and farm group as random effects resulted in two of the previously identified factors being associated with hide contamination. If at least one of the adjacent carcases on the line had a contaminated hide, the associated odds ratio was 6.6 (95% CI: 2.8-15.9), which rose to 22.7 (95% CI: 9.3-55.5) if both adjacent hides were contaminated. Receiving hay in lairage was found to be important to the model, although not significant in itself (OR 0.005; 95% CI: 1.2e(-6)-20.7). These results suggest that modifiable risk factors for hide contamination exist. However, in order best to reduce the prevalence of hide contamination at slaughter, individual slaughterhouse risk assessment and intervention strategies are appropriate.

Progression of acetabular periprosthetic osteolytic lesions measured with computed tomography

BACKGROUND

A better understanding of the factors associated with the size and/or progression of osteolytic lesions has been hampered by a lack of sensitivity of radiographic measurement techniques.

METHODS

We retrospectively analyzed quantitative computed tomography scans that had been made with use of a high-resolution multi-slice scanner with a metal artifact-suppression protocol. The scans had been made to determine the volume of osteolytic lesions around thirty-five cementless Harris-Galante acetabular components that had been in situ for at least ten years. Repeat scans of thirty hips allowed for the measurement of progression in the size of osteolytic lesions over a one-year period. Associations between the volume of osteolytic lesions, progression in the size of the lesions, polyethylene wear since the time of implantation, change in component position, and patient-related variables (age, gender, body mass index, activity level, walking limitations, joint pain, and function) were determined.

RESULTS

In sixteen of the thirty hips that had repeat computed tomography scans, the lesions progressed in size during the study period. The median size of the lesions in these sixteen hips was 10.3 cm(3) at the time of the initial scan, compared with 13.3 cm(3) at a median of fifteen months later (p = 0.001). Osteolytic lesions measuring >10 cm(3) in volume on the initial scan were 2.5 times (95% confidence interval 1.3 to 4.8 times) more likely to progress in size over one year than smaller lesions were. Patients with greater polyethylene wear rates, higher activity levels, no walking limitations, and larger prosthetic femoral head dimensions (26 or 28 mm) had significantly larger osteolytic lesions (p < 0.0001, p = 0.009, p = 0.006, and p = 0.028, respectively). Progression in the size of the osteolytic lesions over one year was significantly associated with larger initial osteolytic lesions (p = 0.002), greater polyethylene wear rates (p = 0.009), and larger (26 or 28-mm) prosthetic femoral head dimensions (p = 0.019).

CONCLUSIONS

There is considerable variation in the rates of progression of the size of osteolytic lesions around stable acetabular components. Lesion size and the progression of lesion size are generally related to polyethylene wear rates, higher patient activity levels, and larger-diameter femoral heads. Osteolytic lesions measuring >10 cm(3) in volume are associated with a high rate of progression.

Solvent Influences on Metastable Polymorph Lifetimes: Real-Time Interconversions Using Energy Dispersive X-Ray Diffractometry**We dedicate this paper to Professor David Grant. Not only a talented scientist, he was a man who gave freely of his time and ideas to support and encourage others, including ourselves

Solvent influences on the crystallization of polymorph and hydrate forms of the nootropic drug piracetam (2-oxo-pyrrolidineacetamide) were investigated from water, methanol, 2-propanol, isobutanol, and nitromethane. Crystal growth profiles of piracetam polymorphs were constructed using time-resolved diffraction snapshots collected for each solvent system. Measurements were performed by in situ energy dispersive X-ray diffraction recorded in Station 16.4 at the synchrotron radiation source (SRS) at Daresbury Laboratory, CCLRC UK. Crystallizations from methanol, 2-propanol, isobutanol, and nitromethane progressed in a similar fashion with the initial formation of form I which then converted relatively quickly to form II with form III being generated upon further cooling. However, considerable differences were observed for the polymorphs lifetime and both the rate and temperature of conversion using the different solvents. The thermodynamically unstable form I was kinetically favored in isobutanol and nitromethane where traces of this polymorph were observed below 10 degrees C. In contrast, the transformation of form II and subsequent growth of form III were inhibited in 2-propanol and nitromethane solutions. Aqueous solutions produced hydrate forms of piracetam which are different from the reported monohydrate; this crystallization evolved through successive generation of transient structures which transformed upon exchange of intramolecular water between the liquid and crystalline phases.