bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite‐difference modeling of SH‐wave propagation in nonwelded contact media
Authors: Slawinski Raphael A. , Krebes Edward S.
Published: September 2002

Many geological structures of interest are known to exhibit fracturing. Fracturing directly affects seismic wave propagation because, depending on its scale, fracturing may give rise to scattering and/or anisotropy. A fracture may be described mathematically as an interface in nonwelded contact (i.e., as a displacement discontinuity). This poses a difficulty for finite‐difference modeling of seismic wave propagation in fractured media, because the standard heterogeneous approach assumes welded contact. In the past, this difficulty has been circumvented by incorporating nonwelded contact into the medium parameters using equivalent medium theory. We present an alternate method based on the homogeneous approach to finite differencing, whereby nonwelded contact boundary conditions are imposed explicitly. For simplicity, we develop the method in the SH‐wave case.

In the homogeneous approach, nonwelded contact boundary conditions are discretized by introducing auxiliary, so‐called fictitious, grid points. Wavefield values at fictitious grid points are then used in the discrete equation of motion, so that the time‐evolved wavefield satisfies the correct boundary conditions. Although not as general as the heterogeneous approach, the homogeneous approach has the advantage of being relatively simple and manifestly satisfying nonwelded contact boundary conditions. For fractures aligned with the numerical grid, the homogeneous and heterogeneous approaches yield identical results. In particular, in both approaches nonwelded contact results in a larger maximum stable time step size than in the welded contact case.
An approximation for the Xu‐White velocity model
Authors: Keys Robert G. , Xu Shiyu
Published: September 2002

In 1995, S. Xu and R. E. White described a method for estimating compressional and shear‐wave velocities of shaley sandstones from porosity and shale content. Their model was able to predict the effect of increasing clay content on compressional‐wave velocity observed in laboratory measurements. A key step in the Xu‐White method estimates dry rock bulk and shear moduli for the sand/shale mixture. This step is performed numerically by applying the differential effective medium method to the Kuster‐Toksöz equations for ellipsoidal pores. This step is computationally intensive. Using reasonable assumptions about dry rock elastic properties, this step can be replaced with a set of approximations for dry rock bulk and shear moduli. Numerical experiments show an extremely close match between velocities obtained with these approximations and velocities computed with the differential effective medium method. These approximations simplify the application of the Xu‐White method, and make the method computationally more efficient. They also provide insight into the Xu‐White method. For example, these approximations show how the Xu‐White model is related to the critical porosity model.
Estimation of quality factors from CMP records
Authors: Zhang Changjun , Ulrych Tadeusz J.
Published: September 2002

Estimates of the quality, Q, factor are commonly obtained from vertical seismic data or stacked surface seismic data. This paper describes a method that allows Q‐factor to be estimated directly from common midpoint (CMP) gathers. Absorption of the wavefield is dependent on three parameters: frequency, traveltime in the medium, and medium Q‐factor. Assuming that the amplitude spectrum of the seismic source signature may be modeled by that of a Ricker wavelet, we derive an analytical relation between Q‐factor and seismic data peak frequency variation both along offset and vertical time direction. The Q‐factor is estimated from CMP gathers using a layer‐stripping approach.
Predictability of quasi-geostrophic turbulence
Authors: MERRYFIELD WILLIAM J. , HOLLOWAY GREG
Published: September 2002

A method is developed for statistical prediction of turbulent geophysical flows that
is more efficient than ensemble integrations. We consider the evolution of low-order
moments for inviscid quasi-geostrophic turbulence. Guided by statistical mechanics,
equations are developed for predicting the mean and the variance about the mean
as functions of position and time. These equations are consistent with the exact
moment equations and contain irreversible (entropy producing) fluxes that must be
specified in terms of known moments. Using simple choices for these dependences, the
resulting scheme, involving just two spatial fields, typically outperforms 100-realization
ensembles.
A quasi-steady approach to the instability of
time-dependent flows in pipes
Authors: GHIDAOUI M. S. , KOLYSHKIN A. A.
Published: September 2002

Asymptotic solutions for unsteady one-dimensional axisymmetric laminar flow in a
pipe subject to rapid deceleration and/or acceleration are derived and their stability
investigated using linear and weakly nonlinear analysis. In particular, base flow solutions for unsteady one-dimensional axisymmetric laminar flow in a pipe are derived
by the method of matched asymptotic expansions. The solutions are valid for short
times and can be successfully applied to the case of an arbitrary (but unidirectional)
axisymmetric initial velocity distribution. Excellent agreement between asymptotic and
analytical solutions for the case of an instantaneous pipe blockage is found for small
time intervals. Linear stability of the base flow solutions obtained from the asymptotic
expansions to a three-dimensional perturbation is investigated and the results are used
to re-interpret the experimental results of Das & Arakeri (1998). Comparison of the
neutral stability curves computed with and without the planar channel assumption
shows that this assumption is accurate when the ratio of the unsteady boundary
layer thickness to radius (i.e. δ1/R) is small but becomes unacceptable when this
ratio exceeds 0.3. Both the current analysis and the experiments show that the
flow instability is non-axisymmetric for δ1/R = 0.55 and 0.85. In addition, when
δ1/R = 0.18 and 0.39, the neutral stability curves for n = 0 and n = 1 are found to
be close to one another at all times but the most unstable mode in these two cases
is the axisymmetric mode. The accuracy of the quasi-steady assumption, employed
both in this research and in that of Das & Arakeri (1998), is supported by the fact
that the results obtained under this assumption show satisfactory agreement with the
experimental features such as type of instability and spacing between vortices. In
addition, the computations show that the ratio of the rate of growth of perturbations
to the rate of change of the base flow is much larger than 1 for all cases considered,
providing further support for the quasi-steady assumption. The neutral stability curves
obtained from linear stability analysis suggest that a weakly nonlinear approach can be
used in order to study further development of instability. Weakly nonlinear analysis
shows that the amplitude of the most unstable mode is governed by the complex
Ginzburg–Landau equation which reduces to the Landau equation if the amplitude is
a function of time only. The coefficients of the Landau equation are calculated for two
cases of the experimental data given by Das & Arakeri (1998). It is shown that the
real part of the Landau constant is positive in both cases. Therefore, finite-amplitude
equilibrium is possible. These results are in qualitative agreement with experimental
data of Das & Arakeri (1998).
Oscillatory forcing of flow through porous
media. Part 2. Unsteady flow
Authors: GRAHAM D. R. , HIGDON J. J. L.
Published: September 2002

Numerical computations are employed to study the phenomenon of oscillatory forcing
of flow through porous media. The Galerkin finite element method is used to solve the
time-dependent Navier–Stokes equations to determine the unsteady velocity field and
the mean flow rate subject to the combined action of a mean pressure gradient and
an oscillatory body force. With strong forcing in the form of sinusoidal oscillations,
the mean flow rate may be reduced to 40% of its unforced steady-state value. The
effectiveness of the oscillatory forcing is a strong function of the dimensionless forcing
level, which is inversely proportional to the square of the fluid viscosity. For a porous
medium occupied by two fluids with disparate viscosities, oscillatory forcing may be
used to reduce the flow rate of the less viscous fluid, with negligible effect on the
more viscous fluid. The temporal waveform of the oscillatory forcing function has a
significant impact on the effectiveness of this technique. A spike/plateau waveform is
found to be much more efficient than a simple sinusoidal profile. With strong forcing,
the spike waveform can induce a mean axial flow in the absence of a mean pressure
gradient. In the presence of a mean pressure gradient, the spike waveform may be
employed to reverse the direction of flow and drive a fluid against the direction of
the mean pressure gradient. Owing to the viscosity dependence of the dimensionless
forcing level, this mechanism may be employed as an oscillatory filter to separate
two fluids of different viscosities, driving them in opposite directions in the porous
medium. Possible applications of these mechanisms in enhanced oil recovery processes
are discussed.
The transition from steady to weakly turbulent
flow in a close-packed ordered array of spheres
Authors: HILL REGHAN J. , KOCH DONALD L.
Published: September 2002

The sequence of transitions in going from steady to unsteady chaotic flow in a
close-packed face-centred cubic array of spheres is examined using lattice-Boltzmann
simulations. The transition to unsteady flow occurs via a supercritical Hopf bifurcation
in which only the streamwise component of the spatially averaged velocity fluctuates
and certain reflectional symmetries are broken. At larger Reynolds numbers, the
cross-stream components of the spatially averaged velocity fluctuate with frequencies
that are incommensurate with those of the streamwise component. This transition
is accompanied by the breaking of rotational symmetries that persisted through
the Hopf bifurcation. The resulting trajectories in the spatially averaged velocity
phase space are quasi-periodic. At larger Reynolds numbers, the fluctuations are
chaotic, having continuous frequency spectra with no easily identified fundamental
frequencies. Visualizations of the unsteady flows in various dynamic states show that
vortices are produced in which the velocity and vorticity are closely aligned. With
increasing Reynolds number, the geometrical structure of the flow changes from
one that is dominated by extension and shear to one in which the streamlines are
helical. A mechanism for the dynamics is proposed in which energy is transferred
to smaller scales by the dynamic interaction of vortices sustained by the underlying
time-averaged flow.
A population-based estimate of the burden of diarrhoeal illness in the United States: FoodNet, 1996–7
Authors: HERIKSTAD H. , YANG S. , VAN GILDER T. J. , VUGIA D. , HADLER J. , BLAKE P. , DENEEN V. , SHIFERAW B. , ANGULO F. J. , THE FOODNET WORKING GROUP
Published: September 2002

This study was performed to better understand and more precisely quantify the amount and burden of illness caused by acute diarrhoea in the United States today. A telephone-based population survey was conducted between 1 July, 1996, and 31 June, 1997, in sites of the Foodborne Diseases Active Surveillance Network (FoodNet). The overall prevalence of acute diarrhoea in the 4 weeks before interview was 11%, giving a rate of 1.4 episodes of diarrhoea per person per year. The rate of diarrhoeal illness defined as a diarrhoeal episode lasting longer than 1 day or which resulted in significant impairment of daily activities was 0.7 per person per year. It can be concluded that acute diarrhoea is common and represents a significant burden of illness in the United States. Our data on self-reported diarrhoea, when generalized to the entire nation, suggests 375 million episodes of acute diarrhoea each year in the United States. Many of these episodes are mild. However, our data also indicate that there are approximately 200 million episodes of diarrhoeal illness each year in the United States.
Risk factors for pneumonia in infants and young children and the role of solid fuel for cooking: a case-control study
Authors: MAHALANABIS D. , GUPTA S. , PAUL D. , GUPTA A. , LAHIRI M. , KHALED M. A.
Published: September 2002

We evaluated the risk factors for childhood pneumonia with particular reference to indoor air-pollution associated with solid fuel use for cooking (e.g. coal, wood, dung), using a case-control study in a children's hospital in Calcutta. Cases were 127 children aged 2–35 months of either sex admitted with pneumonia and controls were 135 children attending their immunization clinic. Solid fuel use (odds ratio = 3.97, CI = 2.00–7.88), history of asthma in the child (OR = 5.49, CI = 2.37–12.74), poor economic status indicator (OR = 4.95, CI = 2.38 to 10.28), keeping large animals (OR = 6.03, CI = 1.13–32.27) were associated with high risk of pneumonia after adjusting for confounding (logistic regression analysis). Nearly 80% of people in India use such smoke producing fuel and the population attributable risk would be very high. This finding has important health policy implications. Furthermore, history of asthma is a useful prognostic indicator for early action for prevention of severe pneumonia.
Detection of four Borrelia burgdorferi genospecies and first report of human granulocytic ehrlichiosis agent in Ixodes ricinus ticks collected in central Italy
Authors: SANTINO I. , DEL PIANO M. , SESSA R. , FAVIA G. , IORI A.
Published: September 2002

The presence of Borrelia burgdorferi s.l. and of Ehrlichia phagocytophila group was sought by PCR in Ixodes ricinus collected in a protected area of central Italy. Nymphs (n = 1475, gathered in 295 pools of 5 nymphs each) and adult ticks (n = 28) were examined. B. burgdorferi s.l. was detected in 13.8% of the nymph pools; of these, 63.4% were infected by B. valaisiana, 26.8% by B. afzelii, 7.3% by B. garinii, and 2.5% by B. burgdorferi s.s. Only a single adult male tick proved to host B. afzelii. The agent of human granulocytic ehrlichiosis (HGE) was detected in 2.7% of the nymph pools. Two HGE agent-positive nymph pools were also found to be positive for B. garinii and for B. afzelii, respectively. This is the first report from central Italy of the finding of the HGE agent in ticks.
Escherichia coli O157[ratio ]H7 infection in cows and calves in a beef cattle herd in Alberta, Canada
Authors: GANNON V. P. J. , GRAHAM T. A. , KING R. , MICHEL P. , READ S. , ZIEBELL K. , JOHNSON R. P.
Published: September 2002

Escherichia coli O157[ratio ]H7 infection of cows and calves in a naturally-infected beef cattle herd in Alberta, Canada, was investigated over 2 years, encompassing two calf production cycles. In both years of the study, E. coli O157[ratio ]H7 was isolated from the faeces of cows shortly after but not before parturition in late winter: 6/38 (16%) in 1996 and 13/50 (26%) in 1997. At <1 week post-partum, 13/52 (25%) calves born in 1997 were shedding the organism. Faecal shedding of E. coli O157[ratio ]H7 by cows and calves continued over the 7 weeks that they were in the calving pens, with the organism being isolated from the faeces of 2–18% of cows and 23–26% of calves during this period. Five weeks after they were moved onto a native grass pasture, all the calves and all but one cow in 1997 had ceased shedding the organism. When the calves were weaned in the fall, E. coli O157[ratio ]H7 was isolated from the faeces of 0–1.5% of the calves 1 week prior to weaning and from 6–14% of the calves within 2 weeks after weaning. Parturition, calving pens and weaning appear to be important factors in maintaining E. coli O157[ratio ]H7 infections in this beef cattle herd. Isolates from cows and calves during the immediate post-partum period were mostly of the same pulsed-field gel electrophoresis (PFGE) type of E. coli O157[ratio ]H7. Similarly, at weaning a common PFGE type of E. coli O157[ratio ]H7, which differed slightly from the post-partum PFGE type, was isolated from the calves. These typing data suggest a common source of infection for the animals as well as demonstrate clonal turnover of resident populations of this pathogen.
Combinations of putative virulence markers in typical and variant enteroaggregative Escherichia coli strains from children with and without diarrhoea
Authors: ELIAS W. P. , UBER A. P. , TOMITA S. K. , TRABULSI L. R. , GOMES T. A. T.
Published: September 2002

Enteroaggregative Escherichia coli (EAEC) is defined by the ability to produce aggregative adherence (AA) to cultured cells. We analysed 128 EAEC strains, isolated from children with and without diarrhoea, regarding the presence of 11 EAEC virulence genes. Seventy strains carried and 58 lacked the EAEC probe sequence; 17 probe positive and 31 probe negative strains showed variations in the AA pattern. All EAEC probe positive strains carried at least one EAEC marker; aspU (94.3%), irp2 (91.4%), and aggR (74.3%) were the most prevalent. Conversely, among the EAEC probe negative strains, 41.4% were devoid of any marker and astA predominated (44.8%). No significant statistical difference in the prevalence of any marker between cases and controls in both EAEC probe groups or AA variants was found. We suggest that the EAEC probe positive strains may have a higher pathogenic potential or alternatively, EAEC probe negative strains may harbour virulence factors as yet undescribed.
A large hotel outbreak of Norwalk-like virus gastroenteritis among three groups of guests and hotel employees in Virginia
Authors: LOVE S. S. , JIANG X. , BARRETT E. , FARKAS T. , KELLY S.
Published: September 2002

A large outbreak of acute gastroenteritis occurred among three different groups of guests and the employees of a Virginia hotel within a 2-week period in November 2000. At least 76 of the hotel's guests and 40 hotel employees had acute gastroenteritis during this period. All tested ill persons were infected with the same strain of Norwalk-like virus, as shown by cloning and sequencing of virus detected in stool specimens from the three guest groups and the employees. Epidemiologic investigation suggested food as the probable source for the guests. Most of the employees, including those sick, did not eat in the hotel, suggesting that environmental contamination and person-to-person transmission could have contributed to the outbreak. The disease continued to spread in the hotel, passing from one guest group to another, by food, environmental contamination, and/or by person-to-person transmission through infected employees and guests. The study describes procedures implemented to control the outbreak and makes recommendations for future outbreak control.
Isolation and characterization of enterohaemorrhagic Escherichia coli O157[ratio ]H7 from cattle in Belgium and Poland
Authors: TUTENEL A. V. , PIERARD D. , URADZINSKI J. , JOZWIK E. , PASTUSZCZAK M. , VAN HENDE J. , UYTTENDAELE M. , DEBEVERE J. , CHEASTY T. , VAN HOOF J. , DE ZUTTER L.
Published: September 2002

EHEC O157 were isolated from faeces of Belgian and Polish beef slaughter cattle. In Belgium, 1281 faecal samples were analysed by immunomagnetic separation [IMS] after enrichment in buffered peptone water from June 1998 till July 1999. Eighty-one samples (6.3%) were positive for E. coli O157. Phage type 8 was most frequently found. Bulls between 1 and 2 years old, slaughtered in September and October were most frequently found positive. Atypical biochemical features were observed in some isolates: 22 (27%) isolates were urease positive and 1 (1.2%) isolate was unable to ferment lactose. In Poland, 551 faecal samples, taken from January 1999 till December 1999, were examined using exactly the same techniques. Four faecal samples (0.7%) were positive for O157 EHEC, yielding seven phage type 8 isolates. All positive samples were from cattle younger than 2 years. Positive samples occurred in August, September and October.
A prolonged outbreak of Norwalk-like calicivirus (NLV) gastroenteritis in a rehabilitation centre due to environmental contamination
Authors: KUUSI M. , NUORTI J. P. , MAUNULA L. , TRAN MINH N. N. , RATIA M. , KARLSSON J. , VON BONSDORFF C.-H.
Published: September 2002

An outbreak of Norwalk-like calicivirus (NLV) gastroenteritis occurred in a rehabilitation centre in southern Finland between December 1999 and February 2000. An epidemiological investigation was conducted to determine the source and extent of the outbreak. More than 300 guests and staff members became ill during the outbreak. No food or activity in the centre could be linked epidemiologically to illness. NLV genogroup II was detected by RT–PCR in stool samples of symptomatic guests and employees. All strains reacted similarly with the microplate hybridization probe panel and showed the same nucleotide sequence, indicating that they represented the same NLV strain. Food and water samples were negative for NLV, whereas NLV was detected in three environmental specimens. The strains from patients and environment were identical based on microplate hybridization probes, suggesting that environmental contamination may have been important for the spread of calicivirus and the protracted course of the outbreak.
A long-term study on the prevalence of shiga toxin-producing Escherichia coli (STEC) on four German cattle farms
Authors: GEUE L. , SEGURA-ALVAREZ M. , CONRATHS F. J. , KUCZIUS T. , BOCKEMÜHL J. , KARCH H. , GALLIEN P.
Published: September 2002

The occurrence of Shiga toxin-producing Escherichia coli (STEC) was studied on four cattle farms. STEC were detected in 29–82% of the cattle. STEC with additional EHEC markers were detected on all farms. The occurrence of the complete virulence marker pattern (stx1 and/or stx2, eae, EHEChlyA, katP, espP) was correlated with the presence of known STEC serotypes. STEC O26[ratio ]H11 and O165[ratio ]H25 with the complete pattern of virulence markers were the most prevalent. STEC O157 (H7/H-) STEC O103[ratio ]H2 and STEC O145[ratio ]H- were found sporadically. Five clonal subgroups of the STEC O26[ratio ]H11 isolates were identified by pulsed-field gel electrophoresis. STEC O26[ratio ]H11 were present in three groups of cattle. This serotype was detected in a single group over the entire fattening period. Most STEC O26[ratio ]H11 with the complete pattern of potential virulence markers were found in clinically healthy cattle. These animals may represent a risk factor for farmers and consumers.
Microvascular Dysfunction in Sepsis
Authors: Lush Cameron W. , Kvietys Peter R.
Published: September 2002

The microvascular dysfunction which occurs in sepsis involves all three elements of the microcirculation: arterioles, capillaries, and venules. In sepsis, the arterioles are hyporesponsive to vasoconstrictors and vasodilators. Sepsis also reduces the number of perfused capillaries, thereby impacting on oxygen diffusion to mitochondria. In the venules of some tissues (e.g., mesentery) there is an inflammatory response characterized by neutrophil infiltration and protein leakage. In addition, PMN‐endothelial adhesive interactions occur in precapillary microvessels and capillaries in organs, such as, the lung and heart. Thus, all these elements of the microcirculation are involved in the sepsis‐induced inflammation. In this review we address emerging views on the mechanisms involved in the microvascular dysfunction induced by sepsis within the framework of these three basic elements of the microcirculatory unit.
Activation of Adenosine A2a Receptors Inhibits Mast Cell Degranulation and Mast Cell‐Dependent Vasoconstriction
Authors: Fenster M.S. , Shepherd R.K. , Linden J. , Duling B.R.
Published: September 2002

Adenosine and inosine accumulate in tissue during periods of ischemia and both molecules have been shown to degranulate mast cells in the hamster cheek pouch via activation of an A3 receptor. An A2‐mediated inhibitory action of adenosine on mast cell degranulation has also been reported (16), and the objective of this research was to investigate the role of adenosine A2 receptors in modulating inosine‐induced mast cell degranulation and subsequent vasoconstriction of microvessels. Methods: Cheek pouches of the Golden hamster were prepared for in vivo microscopy. Adenosine, inosine, and other agents were applied either globally in the superfusion solution or to selected regions of the tissue by pipette. Results: Micropipette application of 10−4 M inosine to periarteriolar mast cells caused a vasoconstriction and an associated mast cell degranulation in 71% of the arterioles tested. The average diameter reduction was 29 ± 5%. To establish a modulatory role for the A2 receptor, low doses of adenosine (100 nM and 10 nM) were applied globally via the superfusion prior to inosine stimulation. This adenosine pretreatment resulted in a decrease in the incidence of the inosineinduced vasoconstriction (17% and 31%), as well as smaller constrictions (0.5 ± 1% and 7 ± 3%). Mast cell degranulation was also reduced by pretreatment with adenosine, as evidenced by a decreased number of mast cells exhibiting ruthenium red dye uptake. The inhibitory effect of adenosine could be eliminated by pretreatment with the nonselective A1/A2 antagonist 8‐(p‐sulfophenyl) theophylline, which restored the inosine‐induced responses to control values. To demonstrate that the effect was A2α‐mediated, vessels were pretreated with the selective A2α agonist 2‐[4‐(2‐carboxyethyl) phenethylamino]‐5′‐N‐ethylcarboxamidoadenosine (CGS21680). Following this treatment, constriction in response to microapplication of inosine (10−4 M) occurred in only 11% of the vessels tested; the average constriction was reduced to 2 ± 2% and no mast cell degranulation was observed. Conclusions: We conclude that mast cell degranulation can be inhibited via activation of an adenosine A2α receptor; which activation occurs at a lower concentration of adenosine than stimulatory A3 receptor activation. This finding may have implications for the pathology of ischemia.
Pressure pain thresholds asymmetry in left‐ and right‐handers: Associations with behavioural measures of cerebral laterality
Authors: Pauli Paul , Wiedemann Georg , Nickola Matthias
Published: September 2002

Pressure pain threshold (PPT) asymmetry of the left and right third digits was assessed in 12 right‐handed and 12 left‐handed subjects using an automatised pressure algometer. A clear PPT asymmetry was found in right‐handed participants, while left‐handed participants revealed no PPT asymmetry. The PPT asymmetry of right‐handed participants was due to a reduced PPT or increased pain sensitivity at the left hand. Behavioural laterality tests revealed a right ear or left hemisphere advantage for the processing of verbal material (consonant‐vocal syllables) and a left visual field or right hemisphere advantage for the processing of emotional faces in all participants. PPT asymmetry was not associated with cerebral laterality assessed with these tests. We conclude that PPT asymmetry is associated with handedness, but neither PPT asymmetry nor handedness are closely associated with measures of cerebral laterality.
Capillary blood sampling: the pain of single‐use lancing devices
Authors: Fruhstorfer Heinrich
Published: September 2002

Six disposable automatic lancing devices were examined in 50 healthy adult volunteers with regard to pain intensity, blood volume and user safety. Devices with a trigger‐linked lancet movement were significantly more painful than those with a preset lancet speed. Residual pain was more frequent after the use of devices with a blade compared to devices with a needle. Only half of the devices reliably produced sufficient blood volumes (>50 μ l). Two of the devices could accidentally be re‐used and constitute a hazard for patient and personnel. It is concluded that some of the disposable automatic lancing devices are safe and reliable but none of them causes minimal pain.
Do epidemiological results replicate? The prevalence and health‐economic consequences of neck and back pain in the general population
Authors: Linton Steven J. , Ryberg Marianne
Published: September 2002

Current estimates of the prevalence and consequences of neck and back pain vary greatly between studies. It is not known whether this variance is due to differences in methodology, or if it depends on the dynamics of the problem over time. The aim of this study was consequently an attempt to replicate and extend the findings of a previous epidemiological study using the same methodology on a new population. A survey of 3000 35–45 year olds, selected at randon, was conducted to determine the prevalence, site, frequency and intensity of the pain as well as any work loss or health‐care utilization. The response rate was 69% and an analysis of non‐responders showed that they were very similar to responders, but had a slightly lower prevalence. The results replicated the original study: 73% reported back pain during the past year and the consequences included considerable suffering and functional impairment. Moreover, 17% of those reporting pain had utilized sick leave during the past year for the problem, while an additional 14% had been off work but had not used sick leave. Sufferers averaged 3.5 health‐care visits during the past year. However, the consumption of resources was highly skewed and about 6% of the sufferers accounted for over 50% of the costs. It was concluded that when the same selection criteria and assessment techniques are employed, the results found are quite similar. This implies that much of the huge variation in reported prevalence rates and consequences of back pain may be due to methodological differences. This underscores the need for standardized methods.
Secondary heat, but not mechanical, hyperalgesia induced by subcutaneous injection of bee venom in the conscious rat: effect of systemic MK‐801, a non‐competitive NMDA receptor antagonist
Authors: Chen Hui‐Sheng , Chen Jun
Published: September 2002

Subcutaneous (s.c.) administration of bee venom into the plantar surface of one hind paw in rats has been found to produce an immediate single phase of persistent spontaneous nociceptive responses (continuously flinching, licking or lifting the injected paw) for 1–2 h accompanied by a 72–96 hour period of primary heat and mechanical hyperalgesia in the injection site and a spread of heat, but not mechanical, hyperalgesia in the non‐injected hind paw (Chen et al., 1999b). To gain insight into the underlying mechanisms of the bee venom‐induced hyperalgesia in particular, we further identified a heat, but not mechanical, hyperalgesia in an area (paw pad) distant from the injection site induced by s.c. injection of bee venom into the posterior leg 0.8–1.2 cm proximal to the heel measured by paw withdrawal reflex to radiant heat or von Frey monofilament stimuli in conscious rats. In the bee venom‐treated hind limb, however, significant reduction in both thermal latency and mechanical threshold of withdrawal reflex was identified for a period of more than 96 h in the heel with a similar characteristic to the primary heat and mechanical hyperalgesia identified in the injection site previously. The time course of the heat hyperalgesia identified in the paw pad of the bee venom‐treated side was shorter and lasted for less than 48 h, which was in parallel with the reduction in thermal latency of the withdrawal reflex identified in the non‐injected hind paw. Moreover, pre‐ or post‐treatment with a single dose of MK‐801 (0.01 mg/kg, i.p.), a non‐competitive N‐methyl‐D‐aspartate (NMDA) receptor antagonist, completely blocked the occurrence, and reversed the established process of the heat hyperalgesia identified in either the bee venom‐treated or non‐treated paw pads, while the same treatments with the drug did not produce any influence upon the development and maintaining of the heat and mechanical hyperalgesia identified in the heel of the injected hind limb. Taken together with our previous results following s.c. intraplantar bee venom injection, we conclude that: (1) in addition to the well‐identified primary heat and mechanical hyperalgesia in the injection site and its adjacent area, s.c. bee venom is also able to produce a secondary heat hyperalgesia in a region distant from the injection site which has a similar characteristic to the contralateral heat hyperalgesia; (2) NMDA receptors are involved in either development or maintenance of the secondary and the contralateral heat hyperalgesia, but without any role in those processes of the primary heat and mechanical hyperalgesia; (3) the secondary heat hyperalgesia seen in the injected hind limb is likely to share the same neural mechanisms with that identified in the non‐injected side via co‐activation of NMDA receptors.
Leg edema from intrathecal opiate infusions
Authors: Aldrete J. Antonio , da Silva Couto J. M.
Published: September 2002

Despite the increasing popularity of intrathecal infusions to treat patients with long‐term non‐cancer‐related pain, this therapy is not without serious side‐effects. Five out of 23 patients who had intrathecal infusions of opiates for longer than 24 months developed leg and feet edema. As predisposing factors, cardiovascular disease, deep venous thrombosis, peripheral vascular disease, and venous stasis of the lower extremities were considered. Every patient who developed pedal and leg edema after the implantation of an infusion pump was also found to have leg edema and venous stasis prior to the time when the pump was inserted. This complication was severe enough to limit their physical activity, and to produce lymphedema, ulcerations and hyperpigmentation of the skin. Reduction of the edema occurred when the dose of the opiate was decreased, and in two cases in which the infusion was discontinued, there was almost complete resolution of the syndrome. It appears that the pre‐existence of pedal edema and of venous stasis is a relative contraindication to the long‐term intrathecal infusion of opiates in patients with chronic non‐cancer pain.
Influence of expectations and actual pain experiences on satisfaction with postoperative pain management
Authors: Svensson Ingrid , Sjöström Björn , Haljamäe Hengo
Published: September 2002

Experience of moderate or even severe postoperative pain has remained a clinical problem despite major progress in pain assessment and management. The aim of the present study was to assess any association between different pre‐ as well as postoperative factors, actual pain experiences in the postoperative period, and the overall patient satisfaction with the pain management. A random sample of surgical patients (n =191) responded to pre‐ and postoperative questionnaires detailing presence of preoperative baseline pain, expected and actually experienced postoperative pain levels and perceived adequacy of the pain relief provided. Patient satisfaction was assessed and factors of importance for satisfaction/dissatisfaction were analysed. It was found that 88% of the patients had previously undergone surgical procedures and that 53% of these patients claimed to have experienced moderate or severe pain at that time. Current pain prior to the present surgical procedure was reported by 61% of the patients. Most patients (91%) expected pain of moderate to severe intensity and 76% reported to have experienced such pain levels. In spite of this 81% of the patients claimed to be satisfied with the pain management while only 8% were dissatisfied. Sex, age, pre‐operative expectation and actual experience of pain relief, and the overall pain experience were found to be factors associated with the probability of being satisfied/dissatisfied. Main characteristics of the dissatisfied patient were a younger age and female sex. It is concluded that patients commonly expect moderate to severe pain in the postoperative period and that the actual pain experience is mainly in accordance with the pre‐operative expectations. Therefore, the validity of patient satisfaction as an optimal outcome variable in quality assurance processes of postoperative pain management may be questioned.
The morphological effects of a radio frequency lesion adjacent to the dorsal root ganglion (RF‐DRG)—an experimental study in the goat
Authors: De Louw Anton J.A. , Vles Hans S.H. , Freling Gerard , Herpers Marcel J.H.M. , Arends Jan W. , Van Kleef Maarten
Published: September 2002

Radiofrequency (RF) lesions adjacent to the dorsal root ganglion (DRG) are increasingly used in the treatment of intractable chronic pain of spinal origin. Opinions differ on which nerve fibres are affected by these lesions. Morphological studies have been carried out to assess the effects of radiofrequency lesions on nervous tissue. Interpretation has been difficult, since most studies have been performed under circumstances which are not comparable to the clinical situation. This study was undertaken to investigate morphological effects of RF lesions as they develop in the normal clinical situation. In two goats 22 G 100 mm SMK electrodes with a 5 mm active tip (Radionics) were positioned posterior to the lumber dorsal root ganglia (DRG). Sixty‐second 67C lesions were made on one side. The contralateral side was used as sham operation. The goats were sacrificed 2 weeks after the procedure. The lesions were studied for size as well as for effects on proliferation and regeneration using Ki‐67 (MIB‐1). Lesions made inside the DRG (23) were 1.8–2.0 mm in size. In these lesions there was a total loss of myelinated fibres. In lesions made adjacent to the DRG there was a significantly higher MIB‐1 labelling on the treated side as compared to the sham‐treated side. An RF lesion inside the DRG destroys myelinated fibres. A lesion adjacent to the DRG increases MIB‐1 activity, indicating proliferation and regeneration after 2 weeks, despite the fact that the lesion was made outside the ganglion.
Interindividual differences in the analgesic response to ketamine in chronic orofacial pain
Authors: Rabben Toril , Øye Ivar
Published: September 2002

The analgesic effect of the N‐methyl‐D‐aspartate (NMDA) receptor blocker ketamine in 17 patients (13 females and four males, age 32–88 years) who had suffered neuropathic orofacial pain for time periods ranging from 6 months to 28 years was examined. The patients were given an i.m. test‐dose of 0.4 mg/kg ketamine combined with 0.05 mg/kg midazolam. Four patients did not experience any analgesic effect of the i.m. test dose. The remaining 13 patients experienced an analgesic effect which lasted for less than 1 h (transient effect) in seven and for several hours (long‐term effect) in six. One week later they were given 4 mg/kg ketamine to be taken orally in combination with a hypnotic drug for three consecutive nights. All patients who reported a long‐term analgesic effect after i.m. ketamine also reported reduced pain intensity on days after taking ketamine at night. The findings of this open study are in accord with the results from a previous double‐blind randomized investigation. In order to evaluate the role of age and pain duration for the analgesic effect of ketamine, we pooled the data from the two studies and performed a correlation analysis of 43 patients. We found a positive correlation between a long pain‐history and lack of analgesic effect and also between a short pain‐history and a long‐term analgesic effect of low‐dose ketamine. The apparent relationship between patient age and ketamine response was, however, not statistically significant. Further, patients with pain following a nerve lesion and patients without a known lesion of peripheral nerves were equally distributed between the three response groups. These results indicate that pain mechanisms are subject to alterations with time and that these alterations involve transition from NMDA to non‐NMDA receptor mediated transmission in central pain pathways.
Prevalence and characteristics of headache in Dutch schoolchildren
Authors: Bandell‐Hoekstra Inez E.N.G. , Abu‐Saad Huda Huijer , Passchier Jan , Frederiks Carla M.A. , Feron Frans J.M. , Knipschild Paul
Published: September 2002

The aim of this study was to determine whether there has been an increase in headache prevalence in Dutch children and to compare headache characteristics of children with low, medium and high headache severity.

A sample of 2358 schoolchildren between the ages of 10 and 17 years filled out Waters'; Headache Questionnaire and the Paediatric Pain Assessment Tool. Results showed that 21% of the boys and 26% of the girls at elementary school, and 14% of the boys and 28% of the girls at high school reported weekly headaches. When compared to figures from a previous study in the Netherlands published in 1985, the prevalence of weekly headaches in 10–17‐year‐olds has increased by 6%. In boys at elementary school, the prevalence of headaches with a frequency of a few times a week has doubled.

Children with low, medium and high headache severity differed with respect to all headache characteristics, i.e. pain quality, accompanying symptoms, warning signals, location, onset, impact of headache, family occurrence, perceived cause, medical consultation, and school absence.
Systemic adenosine infusion reduces the area of tactile allodynia in neuropathic pain following peripheral nerve injury: a multi‐centre, placebo‐controlled study
Authors: Sjölund Karl‐Fredrik , Belfrage Måns , Karlsten Rolf , Segerdahl Märta , Arnér Staffan , Gordh Torsten , Solevi Alf
Published: September 2002

Systemic adenosine has been shown in earlier case reports and a small placebo‐controlled study to reducepathological sensory dysfunction such as tactile allodynia in neuropathic pain. To evaluate this further, the effects of systemic adenosine infusion (50 μg/kg/min for 60 min) on tactile sensory dysfunction and pain was evaluated in 26 patients suffering peripheral neuropathic pain characterized by dynamic tactile allodynia. A randomized, cross‐over, double‐blind, placebo‐controlled technique was used in this multi‐centre study. Psychophysical methods were used to evaluate sensory dysfunction and spontaneous pain. The area of dynamic tactile allodynia was significantly reduced by adenosine compared with placebo (p=0.043), but spon‐taneous pain and tactile pain threshold were not significantly improved compared with the effects of placebo treatment. As a secondary outcome, a higher incidence of positive subjective effects on the clinical pain condi‐tion, in a few cases with long duration (several months), following adenosine treatment was found when theglobal effect of respective treatment was assessed (p=0.028). The results demonstrate involvement of adenosine receptor‐sensitive pain mechanisms in some aspects of the sensory dysfunction often found in neuropathic pain.
Nalbuphine by PCA‐pump for analgesia following hysterectomy: bolus application versus continuous infusion with bolus application
Authors: Krenn Herbert , Oczenski Wolfgang , Jellinek Helmuth , Krumpl‐Ströher Martha , Schweitzer Ekkehard , Fitzgerald Robert D.
Published: September 2002

The analgesic properties of the partial agonist–antagonist nalbuphine in the postoperative period are well known. When used for patient‐controlled analgesia (PCA) the effectiveness of this substance is comparable to that of morphine or tramadol. However, the optimal programme for administration of nalbuphine in PCA‐pumps has not been investigated. In particular, the combination of bolus administration vs bolus administration plus continuous basal administration is disputable.

We hypothesized that the administration of an extra basal rate of nalbuphine in addition to the patient‐ triggered bolus administration and supplemental doses of diclofenac when required, would lead to a significant improvement in analgesia, without affecting the differences in vital signs and side effects.

After approvement by the institutional ethics committee, 50 female patients (ASA I or II) scheduled for elective hysterectomy were included in a prospective, single‐blinded study and randomized either into bolus‐continous (BC‐)group (3 mg base rate/h, 1 mg bolus, 20 min lock out) or bolus (B‐)group (no base rate, 1 mg bolus, 10 min lock out). During the observation period (up to 24 h postoperative) vital parameters, extent of analgesia (10‐step VAS), and vigilance (5‐step scale) were registered. Groups were compared by using unpaired Student t‐test. Ap <0.05 was considered to be significant.

No differences were found in demographic data or vital parameters (MAP, PaO2, PaCO2, respiratory rate, heart rate, peripheral SaO2) during the observation period. Vital parameters showed no pathological changes in any group. With an identical rate of requirement for diclofenac (32 and 36%), analgesia in BC‐group showed a decrease in VAS from 4.28±2.11 to 2.04±1.21 and from 3.64±2.20 to 2.08±0.96 in B‐group. Vigilance was only marginally diminished in both groups. No serious side effects were found in either group. The consumption of nalbuphine (mg) was significantly higher in BC‐group (70.28±13.85 vs. 47.44±22.99;p =0.0002) when compared to B‐group. Subjective rating of effectiveness by the patients was similar in both groups.

The two administration settings of nalbuphine by PCA pump have shown to be equally effective in the treatment of postoperative pain following hysterectomy. However, as the total amount of nalbuphine was significantly lower in B‐group, the use of this administration schedule should be encouraged. Copyright 2001 European Federation of Chapters of the International Association for the Study of Pain
The Level of Expressed Need—a measure of help‐seeking behaviour for chronic pain in the community
Authors: Smith Blair H. , Penny Kay I. , Elliott Alison M. , Chambers W.Alastair , Smith W.Cairns
Published: September 2002

Chronic pain is a common and disabling condition, with a high impact on health and the health services in the community. The extent of help‐seeking behaviour and factors that influence this are complex, but poorly understood. A simple, valid measure of help‐seeking behaviour would be useful for community‐based research, with a view to developing and evaluating interventions.

The aims of the study were to test a hierarchical scale designed to measure help‐seeking behaviour in chronic pain in postal surveys of the community, and to explore factors associated with responses.

As part of a community survey of chronic pain, we developed the Level of Expressed Need (LEN) scale, based on questions about the use of treatment and professional advice for chronic pain. We compared this scale with two measures of chronic pain severity—the Chronic Pain Grade (CPG), and the Glasgow Pain Questionnaire (GPQ)—and analyzed associations with the SF36 general health questionnaire and demographic variables.

Of 3605 respondents (corrected response rate 82%), 1817 reported chronic pain. Of these, 17% were at the mildest and 28% at the severest LEN. There were strong correlations with both the CPG (r=0.48) and the GPQ (r=0.55). There were, however, many important disparities in responses to these measures. Several other factors were independently associated with a high LEN in chronic pain: female gender, lower educational level, and physical, mental, pain and general health dimensions of the SF36 questionnaire.

The LEN is a useful tool for measuring the help‐seeking response to chronic pain in the general population. The findings confirm that this response is influenced by clinical and demographic factors in addition to the severity of the pain. Further development work will strengthen the instrument to explore these.