bluuebunny/crossref_metadata_2025 huggingface dataset:
Radon‐222 as a Tracer for Nonaqueous Phase Liquid in the Vadose Zone: Experiments and Analytical Model
Authors: Höhener Patrick , Surbeck Heinz
Published: July 2010

The potential use of the naturally occurring noble gas 222Rn as a tracer for vadose zone contamination by nonaqueous phase liquids (NAPLs) is studied experimentally and theoretically. n‐Dodecane was chosen as the model NAPL. In batch experiments containing unsaturated alluvial sand, a 2.9‐fold decrease of the steady‐state 222Rn activity in soil gas was measured as a consequence of the increase in the volumetric NAPL content from 0 to 0.074. A one‐dimensional analytical reactive transport model was developed that includes 222Rn production, gas‐phase diffusion, partitioning, and radioactive decay. Radon‐222 soil gas profiles were predicted for homogeneous and heterogeneous sandy profiles where NAPL contamination was restricted to selected depth layers. The resulting depth profiles document that the position of the NAPL has great influence on the 222Rn activity depth profile. An outdoor lysimeter experiment was performed using unsaturated alluvial sand contaminated by NAPL at depths from 1 to 1.2 m. In the lysimeter experiment, a spill of 2 L m−2 NAPL did not alter significantly the 222Rn profile, as predicted also by model calculations. We concluded that 222Rn can be used as a NAPL tracer in the vadose zone only at heavily polluted sites with uniform spatial 222Rn production.
Numerical Analysis of Transport of Interacting Solutes in a Three‐Dimensional Unsaturated Heterogeneous Soil
Authors: Russo David , Zaidel Jacob , Laufer Asher
Published: July 2010

The present study focuses on field‐scale flow and transport in three‐dimensional, heterogeneous, variably saturated formations, for the case in which the flow is coupled to the transport through the dependence of the hydraulic conductivity and water retentivity on solute concentrations. Numerical simulations of flow and transport of both tracer and mixed Na–Ca solutes were employed to analyze long‐term effects of the interactions between the soil solution and the soil matrix on water and solute movement, under transient, nonmonotonic flows. The simulated flows were derived from actual irrigation and weather records, along with water uptake by plant roots. Results of this study suggest that enhanced soil solution–soil matrix interactions, induced by soil alkalinity and dilution of the soil solution, may reduce both the mean and the spatial variability of the hydraulic conductivity, and, concurrently, of the velocity. Consequently, enhanced soil solution–soil matrix interactions may slow down the tracer solute movement, decrease the spreading of the tracer solute about its center of mass (particularly in the vertical direction), diminish the skewing of the tracer solute breakthrough, and decrease both the magnitude of the effective retardation factor and the rate at which it approaches its asymptotic value. In addition, our results suggest that under realistic conditions, the three‐dimensionality of the flow domain, the periodicity of the rain or irrigation events, along with the substantial redistribution periods between successive events, and the spatial heterogeneity of the hydraulic properties of the variably saturated formation may compensate in part for the adverse effects of soil alkalinity on flow and transport on the field scale. This last finding has practical implications regarding the use of sewage water for irrigation.
The Effect of Vertically Decreasing Macropore Fractions on Simulations of Non‐Equilibrium Solute Transport
Authors: Haws Nathan W. , Rao P. Suresh C.
Published: July 2010

The effects of a depth‐decreasing macropore fraction and the corresponding decrease in the diffusive mass‐transfer coefficient for solute exchange between soil matrix and macropore regions were simulated for a hypothetical, one‐dimensional, mobile–immobile, transport domain. These effects are illustrated using an expression for a Damkhöler number, and with numerical simulations with a dual‐porosity module within the HYDRUS‐2D code. The depth‐wise change in the macroporosity was represented with an exponentially decreasing macropore fraction, based on a pore‐network model. Five simulations were run, four with various steady infiltration rates (two at water saturation and two at different levels of unsaturation) and one with transient infiltration rates. Deviations between the predicted solute breakthrough curves (BTCs) for simulations using depth‐variable parameters and those using spatially averaged parameters were minor at the lowest infiltration rate, indicating little effect of non‐equilibrium conditions. However, at higher infiltration rates, the BTC peak height and peak timing varied by as much as a factor of two, indicating significant influence of the variability of the macropore fractions with depth. Using depth‐averaged values to represent the variable macropore fraction will closely approximate the BTC of a spatially variable case for both steady‐state and transient infiltration; however, the concentration profile within the transport domain will not be accurately predicted. A sensitivity analysis conducted for the saturated hydraulic conductivity, length of the soil ped, and dispersivity parameters shows that changes in the prediction error between the spatially variable and surface‐valued simulations are most sensitive to these parameters as the soil approaches water saturation.
In Situ Long‐Term Chloride Transport through a Layered, Nonsaturated Subsoil. 2. Effect of Layering on Solute Transport Processes
Authors: Javaux M. , Vanclooster M.
Published: July 2010

We analyze observed Cl− transport during a large‐scale in situ unsaturated infiltration experiment in terms of the observation scale of the transport process and the physical stratification of the Tertiary sedimentary flow domain. By comparing piston flow and local velocity profiles, we show that velocity variations cannot be explained by water content changes alone. We also demonstrate that by comparing a layered convection–dispersion (CD) model with the observations, the dispersivity profile cannot be explained with the model, which produced unrealistic local dispersivity values. These discrepancies were partially explained by nonrepresentative sampling using porous cup solution samplers (PCS). We hypothesize that fingering flow or convergence phenomena below sand–clay interfaces leads to nonrepresentative artificially high dispersivity values. Velocity and dispersivity values immediately above the clay layers, however, seem more reliable due to convergence and more lateral mixing induced by a larger water content. Following the criteria derived from the Chuoke equation, we show that the subsoil can be subjected to fingering flow. We found that this process likely persisted for some 17 yr. Therefore, we conclude that the fine‐textured clayey layers regulated the flow rate through time, approaching a quasi‐steady‐state flow condition. Overall, solute transport processes in the unsaturated layered subsoil appeared to be very strongly influenced by stratification of the flow domain. An apparent highly variable flow field was induced by the clay layers interbedded in a sandy deposit, while the local PCS sampling devices were likely too small to properly assess the mixing regime at this large scale.
Assessment of Root Zone Nitrogen Leaching as Affected by Irrigation and Nutrient Management Practices
Authors: Nakamura K. , Harter T. , Hirono Y. , Horino H. , Mitsuno T.
Published: July 2010

Multiple or split N fertilizer applications during a single cropping period is a recommended practice for controlling N (specifically NO3–N) leaching into groundwater. Here, we demonstrate the benefit of split fertilizer applications in two typical upland soils of Japan (sand and Andosol) using a combination of a laboratory experiment and modeling. Soil water flow and N transport properties of the soils were measured using standard procedures. Transient N and water transport experiments were conducted in cylindrical soil columns under single (lumped) and split NH4–N applications. The column experiments were successfully simulated using Richards' equation and an advection–dispersion model with equilibrium nonlinear sorption conditions and first‐order transformation for N speciation. Using the model for the two soils, several irrigation and fertilizer management scenarios were then simulated based on 1992 through 2000 meteorological data to investigate the long‐term effects of lumped and split fertilization schedules for a representative set of crop and irrigation conditions. In comparison with lumped applications, split fertilizer applications were found to consistently reduce the amount of N leaching, even though year‐to‐year differences of N leaching reductions between sand and Andosol were significant. For unstressed crops, the actual reduction in N leaching are shown to depend on the timing of precipitation and irrigation events, on soil type, and on plant N uptake behavior. However, across all scenarios, two split applications instead of a single, lumped application reduced the N leaching fraction by approximately one‐third. In the sandy soil, a three‐way split resulted in further leaching reductions compared with the two‐way split. Six‐way split applications did not result in further N leaching improvements in either sand or Andosol. After adjusting N application rates to account for reduced N use efficiency, N leaching rates for unstressed crops under lumped fertilization were found to be several times higher than under split applications.
Subsurface Drip Irrigation in Gravel‐Filled Cavities
Authors: Ben‐Gal Alon , Lazorovitch Naftali , Shani Uri
Published: July 2010

Subsurface drip irrigation (SDI) is regularly used to provide water and nutrients to plants while maintaining a dry soil surface. Problems associated with the practice of SDI are spatially dependent reductions in dripper discharge and possible surfacing of water resulting from positive pressure at the emitter–soil interface. These can be resolved either through prudent care in matching dripper flow rates to soil hydraulic properties or by otherwise providing conditions under which positive pressure cannot arise. We present a method where water is applied to the soil within a gravel‐filled cavity. The necessary volume of gravel is determined by the contact area between the cavity and the soil and is a function of irrigation rates, dripper spacing, and soil hydraulic properties. A theoretical solution for the radius of a gravel‐filled cavity based on the perimeter of the saturated zone from a line source in the soil demonstrates that larger cavities are needed as soil hydraulic conductivity decreases. The method was tested using a numeric simulation model (HYDRUS‐2D) and was used and tested in a vineyard of table grapes (Vitis Vinifera L. cv. Sugraone) in a 7‐yr study with SDI and gravel‐trenched subsurface application of effluent and fertilizers.
Characterizing Unsaturated Diffusion in Porous Tuff Gravel
Authors: Hu Qinhong , Kneafsey Timothy J. , Roberts Jeffery J. , Tomutsa Liviu , Wang Joseph S. Y.
Published: July 2010

Evaluation of solute diffusion in unsaturated porous gravel is very important for investigations of contaminant transport and remediation, risk assessment, and waste disposal (e.g., the potential high‐level nuclear waste repository at Yucca Mountain, Nevada). For a porous aggregate medium such as granular tuff, the total water content is comprised of surface water and interior water. The surface water component (water film around grains and pendular water between the grain contacts) could serve as a predominant diffusion pathway. To investigate the extent to which surface water films and contact points affect solute diffusion in unsaturated gravel, we examined the configuration of water using X‐ray computed tomography (CT) in partially saturated gravel and made quantitative measurements of diffusion at multiple water contents using two different techniques. In the first, diffusion coefficients of KCl in 2‐ to 4‐mm granular tuff at multiple water contents were calculated from electrical conductivity (EC) measurements using the Nernst–Einstein equation. In the second, we used laser ablation with inductively coupled plasma–mass spectrometry (LA/ICP‐MS) to perform microscale mapping, allowing the measurement of diffusion coefficients for a mixture of chemical tracers for tuff cubes and tetrahedrons having two contact geometries (cube–cube and cube–tetrahedron). The X‐ray computed tomography images show limited contact between grains, and this could hinder the pathways for diffusive transport. Experimental results show the critical role of surface water in controlling transport pathways and hence the magnitude of diffusion. Even with a bulk volumetric water content of 1.5%, the measured solute diffusion coefficient is as low as 1.5 × 10−14 m2 s−1 for tuff gravel. Currently used diffusion models relating diffusion coefficients to total volumetric water content inadequately describe unsaturated diffusion behavior in porous gravel at very low water contents.
Flow in Menisci Corners of Capillary Rivulets
Authors: Dragila Maria Inés , Weisbrod Noam
Published: July 2010

Liquids that flow in unsaturated rock fractures exhibit a range of behavior distinct from flow within the porous matrix. Flow patterns observed in laboratory experiments include aperture‐spanning droplets, snapping and continuous capillary threads or rivulets, islands of local saturation, and fingering. Knowledge of the contact area and flow rate for each mode is necessary to achieve successful modeling of the fracture–matrix solute transfer. A geometric model for a rivulet cross section that includes the shape of the curved meniscus between the two walls of a fracture is used in this paper to calculate (i) the flow rate within the menisci corners, (ii) a critical flow rate that determines whether a rivulet will snap or be continuous, and (iii) the width of the wetted contact against a fracture wall. For low flow rates that are near the critical value between snapping and continuous conditions, the contact area was found to be up to 18 times greater than that predicted using a simpler rectangular geometry for the rivulet cross section. A wider contact area also suggests a slower mean flow and larger time constant for solute transfer.
Comparing van Genuchten and Percolation Theoretical Formulations of the Hydraulic Properties of Unsaturated Media
Authors: Hunt A. G.
Published: July 2010

Recent results from percolation theory as applied to the hydraulic conductivity of unsaturated porous media are compared with the frequently used phenomenological relationship due to van Genuchten. In applications so far percolation theory has proven to be predictive and unifying, while the van Genuchten phenomenology is intended only to be descriptive. To illustrate: the critical volume fraction for percolation is an analog to the residual moisture content, but a phenomenological result exists for the former in terms of the specific surface area, whereas the latter is intended only as a fit parameter. Second, it is recognized not to be possible to predict the hydraulic conductivity as a function of saturation using merely textural data—enough information about the pore space must be available to distinguish between various potential models. When the data are sufficient to confirm a fractal model, however, percolation theory yields a result that has several similarities to the van Genuchten parameterization. The analysis helps lead to a better understanding of the van Genuchten relationship.
Selenium(IV) and (VI) Sorption by Soils Surrounding Fly Ash Management Facilities
Authors: Hyun Seunghun , Burns Perre E. , Murarka Ishwar , Lee Linda S.
Published: July 2010

Leachate derived from unlined coal ash disposal facilities is one of the most significant anthropogenic sources of selenium to the environment. To establish a practical framework for predicting transport of selenium in ash leachate, sorption of Se(IV) and Se(VI) from 1 mM CaSO4 was measured for 18 soils obtained down‐gradient from three ash landfill sites and evaluated with respect to several soil properties. Furthermore, soil attenuation from lab‐generated ash leachate and the effect of Ca2+ and SO42− concentrations as well as pH on both Se(IV) and Se(VI) was quantified for a subset of soils. For both Se(IV) and Se(VI), pH combined with either percentage clay or dithionite‐citrate‐bicarbonate (DCB)‐extractable Fe described >80% of the differences in sorption across all soils, yielding an easy approach for making initial predictions regarding site‐specific selenium transport to sensitive water bodies. Se(IV) consistently exhibited an order of magnitude greater sorption than Se(VI). Selenium sorption was highest at lower pH values, with Se(IV) sorption decreasing at pH values above 6, whereas Se(VI) decreased over the entire pH range (2.5–10). Using these pH adsorption envelopes, the likely effect of ash leachate‐induced changes in soil pore water pH with time on selenium attenuation by down gradient soils can be predicted. Selenium sorption increased with increasing Ca2+ concentrations while SO42− suppressed sorption well above enhancements by Ca2+ Soil attenuation of selenium from ash leachates agreed well with sorption measured from 1 mM CaSO4, indicating that 1 mM CaSO4 is a reasonable synthetic leachate for assessing selenium behavior at ash landfill sites.
Estimating Large‐Scale Fracture Permeability of Unsaturated Rock Using Barometric Pressure Data
Authors: Wu Yu‐Shu , Zhang Keni , Liu Hui‐Hai
Published: July 2010

We present a three‐dimensional modeling study of gas flow in the unsaturated fractured rock of Yucca Mountain. Our objective was to estimate large‐scale fracture permeability, using the changes in subsurface pneumatic pressure in response to barometric pressure changes at the land surface. We incorporate the field‐measured pneumatic data into a multiphase flow model for describing the coupled processes of liquid and gas flow under ambient geothermal conditions. Comparison of field‐measured pneumatic data with model‐predicted gas pressures is found to be a powerful technique for estimating the fracture permeability of the unsaturated fractured rock, which is otherwise extremely difficult to determine in field studies with large scales of interest. In addition, this study demonstrates that the multidimensional flow effect on estimated permeability values is significant and should be included when determining fracture permeability in heterogeneous fractured media.
Legal-Expenses Insurance and Settlement
Authors: Qiao Yue
Published: July 2010

In this paper we consider the effects of legal-expenses insurance on settlement. Using a one-shot asymmetric information model of litigation, we scrutinize the litigants' interactions under the situations that the plaintiff is before-the-event insured, after-the-event insured or self-funded. We investigate the effects of insurance on settlement probabilities, settlement amounts, care levels and the plaintiff's welfare. We also show how the model can be amended to include a "recoverable" element of the insurance. Our results exhibit that insurance increases the plaintiff's expectation on settlement amount but its effects on settlement probabilities and care levels depend on the distribution of the accident loss. This is partly because asymmetric information distorts the litigants' negotiation power. Insurance can either increase or decrease welfare.
Patients' adherence to treatment of diabetes mellitus
Authors: Petek Davorina , Rotar-Pavlič Danica , Kersnik Janko , Švab Igor
Published: July 2010

Patients' adherence to treatment of diabetes mellitus

Objectives: Diabetes is a chronic disease where patient's ability for self management is very important. Patients are every day taking decisions how to integrate treatment recommendations into their lives without impacting the quality of life. The aim of this study was to explore participants' perceived barriers to adherence to treatment.

Methods: A qualitative study with five focus groups of patients with Type 2 diabetes and one group of experts on diabetes mellitus was performed in the central area of Slovenia. The transcribed text was independently analysed by principles of grounded theory with codes merging into themes and categories.

Results: Time changes patients' attitudes toward disease. Good education about the disease and their own experience with the disease help patients to adapt to different life situations and to regain control in their life. Family and friends are not always supportive to diabetes treatment. Some patients deny having disease in social encounters because they feel stigmatised. Diabetes also challenges patient's working ability and financial welfare. Patients also emphasise that mutual trust with physician and his true interest in patients' problems is very important for good results of medical care. They refuse universal advice and expect that the doctor helps them to develop self-management skills and coping with the disease. Additional prerequisites for good self management are also adequate organisation of life and adequate personal characteristics of the patients.

Discussion: This study offers additional insights into patients' views of the barriers to adherence. Patients feel empowered for occasional departure from recommended treatment in some social and life situations. Better medical care could be the result of good balance between social expectations of the patients, treatment and working demands on one side and individualised support of the physician with patients' own capacity to rearrange life on the other side.
The prevalence of secondary dentinal lesions in cheek teeth from horses with clinical signs of pulpitis compared to controls
Authors: CASEY M. B. , TREMAINE W. H.
Published: July 2010

Reasons for performing study: With the advent of detailed oral examination in horses using dental mirrors and rigid endoscopy, secondary dentinal lesions are observed more frequently. More information regarding the association of secondary dentinal defects with apical dental disease would improve the sensitivity of oral examination as a diagnostic aid for pulpitis.

Objectives: To assess prevalence and severity of secondary dentinal defects observed on examination of occlusal surfaces of cheek teeth (CT) from horses showing clinical signs of pulpitis compared to asymptomatic controls.

Methods: Records from all cases of equine CT exodontia at the University of Bristol over a 4 year period were examined. Case selection criteria included the presence of clinical signs of pulpitis, an intact extracted tooth and availability of a complete history and follow up. Cases where coronal fracture or periodontal pocketing featured were excluded. CT from cadavers with no history of dental disease served as normal controls. Triadan positions and eruption ages of control teeth were matched with those of teeth extracted from cases. CT from selected cases and control teeth were examined occlusally. Secondary dentinal defects were identified and graded. Prevalence of occlusal lesions in CT with pulpitis and controls was compared.

Results: From the records of 120 horses where exodontia was performed, 40 cases matched selection criteria. Twenty‐three mandibular and 21 maxillary CT were extracted from cases. The controls consisted of 60 mandibular and 60 maxillary CT from 7 cadaver skulls. Secondary dentinal defects were significantly over‐represented in CT extracted from cases of pulpitis (P<0.001). Of diseased mandibular CT, 56.5% had defects compared to none of the controls. Of diseased maxillary CT, 57% had defects compared with 1.6% of controls. Multiple defective secondary dentinal areas and severe lesions were more prevalent in diseased mandibular CT compared with diseased maxillary CT.

Conclusions and practical significance: Careful examination of occlusal secondary dentine is an essential component in investigation of suspected pulpitis in equine CT.
Successful treatment of persistent dorsal displacement of the soft palate and evaluation of laryngohyoid position in 15 racehorses
Authors: ORTVED K. F. , CHEETHAM J. , MITCHELL L. M. , DUCHARME N. G.
Published: July 2010

Reasons for performing study:Caudal descent of the larynx has been proposed to be associated with intermittent dorsal displacement of the soft palate (DDSP) as it leads to a loss of the seal between the epiglottis and soft palate but further investigation of this theory is required.

Objectives:To evaluate laryngohyoid position of horses with persistent DDSP in comparison to horses with intermittent DDSP and evaluate the outcome of treatment.

Hypotheses:Horses with persistent DDSP have a different laryngohyoid position compared to those with intermittent DDSP. Horses with persistent DDSP can be returned successfully to racing with a laryngeal tie‐forward procedure.

Methods:Medical records of 15 racehorses presented for persistent DDSP between 2002 and 2007 were reviewed. Age, sex and breed matched horses diagnosed with intermittent DDSP were used as a comparison group. Treatment of all horses was performed by laryngeal tie‐forward, 8/15 horses with persistent DDSP had a subsequent laser staphylectomy. Preoperative laryngohyoid position was compared between the 2 groups using a radiographic reference system. Surgical effect on position was assessed by comparing pre‐ and post operative radiographic measurements. Outcome was assessed by return to racing and comparison of pre‐ and post operative race earnings ($).

Results:Thirteen of 15 horses with persistent DDSP returned to racing. Seven of 15 horses were treated with laryngeal tie‐forward alone while 8/15 horses were also treated with a laser staphylectomy. Horses with persistent DDSP had a more caudal larynx (ossification of the thyroid cartilage) (13 mm, P = 0.014), a more caudal (10 mm, P = 0.044) and dorsal (7 mm, P = 0.01) basihyoid bone, and a more dorsal thyrohyoid‐thyroid articulation (10 mm, P = 0.002) than horses with intermittent DDSP.

Conclusions and potential relevance:Racehorses with persistent DDSP can be treated successfully by laryngeal tie‐forward or by laryngeal tie‐forward followed by laser staphylectomy. Horses with persistent DDSP have a more caudal larynx and more caudal and dorsal basihyoid bone than horses with intermittent DDSP.
Standing magnetic resonance imaging detection of bone marrow oedema‐type signal pattern associated with subcarpal pain in 8 racehorses: A prospective study
Authors: POWELL S. E. , RAMZAN P. H. L. , HEAD M. J. , SHEPHERD M. C. , BALDWIN G. I. , STEVEN W. N.
Published: July 2010

Reason for performing study:The proximal metacarpal region is a common site of origin of lameness in the performance horse. A number of disease entities are recognised as causes of proximal metacarpal lameness but a definitive diagnosis is often elusive. Magnetic resonance imaging (MRI) is hypothesised to offer advantages over traditional imaging modalities in the investigation of proximal metacarpal pain.

Objective:To describe clinical and imaging features of cases of lameness in racehorses arising from the proximal metacarpal region in which standing MRI identified ‘bone marrow oedema‐type’ (BMO‐type) signal patterns.

Methods:Records for all horses undergoing standing MRI of the proximal metacarpus/distal carpus from September 2006 to December 2008 were reviewed. Cases underwent a standardised protocol for diagnostic analgesia, radiography and ultrasonography of the proximal metacarpus and distal carpus. Cases with proximal metacarpal lameness displaying a characteristic BMO‐type signal pattern on MRI were identified and outcomes analysed.

Results:Eight cases were identified with characteristic MRI findings of extensive hyperintensity on T2* gradient echo and short tau inversion fast spin echo sequences and corresponding hypointensity on T1 gradient echo images within the palmaroproximal aspect of the third metacarpal bone. Follow‐up information was available for all cases; at the time of writing 7/8 had returned to full work and were free from lameness.

Conclusions:The BMO‐type signal patterns visible on MR images in these cases may signal the existence of a previously under‐diagnosed pathological process associated with proximal metacarpal lameness in racehorses. This finding is postulated to be associated with a stress reaction and possible prodromal stress fracture of the palmaroproximal metacarpus not appreciable radiographically or ultrasonographically.

Potential relevance:MRI of the proximal metacarpal region permits detection of pathological processes, which may elude conventional imaging and, therefore, has important therapeutic and prognostic implications in these cases.
Anatomical studies of maxillary cheek teeth infundibula in clinically normal horses
Authors: FITZGIBBON C. M. , DU TOIT N. , DIXON P. M.
Published: July 2010

Reasons for performing study: Although clinical disorders of equine maxillary cheek teeth (CT) infundibula are common, anatomical knowledge of these structures is poor.

Hypothesis: Anatomical examinations of sectioned CT infundibula will better define their shapes and sizes and allow identification of infundibular cemental variations and changes.

Material and methods: Cheek teeth were extracted post mortem from 33 horses, aged 3–30 years, without a clinical history of dental disease. The CT were sectioned longitudinally in the bucco‐palatal plane through the widest aspects of both infundibula. The infundibular surfaces were then assessed morphologically, including by measurements of areas of cemental variations and changes. Specimens from selected teeth were examined histologically.

Results: Infundibular length and infundibular surface area, and infundibular length as a proportion of dental crown length progressively decreased with age, e.g. infundibular length was up to 89 mm after eruption to 2 mm in one older horse. Triadan 06 and 09 positions had significantly shorter CT and therefore infundibula, than the other 4 Triadan positions. Only 11.7% of infundibula were filled completely with normal appearing cementum, 8.2% of infundibula (especially the 09 position) had complete cemental caries; 22.6% of infundibula had areas with cemental hypoplasia and the remaining 57.5% of infundibulae had a variety of other cemental appearances, including the presence of central defects, localised occlusal caries and cemental discolourations. Histology showed the presence of an apical blood supply to infundibular cement in younger horses.

Conclusions: Anatomical variations of CT infundibular cement are very common and some changes, such as areas of localised cemental hypoplasia, may predispose to the development of infundibular caries.

Potential relevance: This more complete description and quantification of CT infundibular anatomy should allow more rational assessment and treatment of equine CT infundibular disorders.
Arterial blood gas parameters of normal foals born at 1500 metres elevation
Authors: HACKETT E. S. , TRAUB‐DARGATZ J. L. , KNOWLES Jr. J. E. , TARR S. F. , DARGATZ D. A.
Published: July 2010

Reasons for performing study: Arterial blood gas analysis is widely accepted as a diagnostic tool to assess respiratory function in neonates. To the authors' knowledge, there are no published reports of arterial blood gas parameters in normal neonatal foals at altitude.

Objective: To provide information on arterial blood gas parameters of normal foals born at 1500 m elevation (Fort Collins, Colorado) in the first 48 h post partum.

Hypothesis: Foals born at 1500 m will have lower PaO2 and PaCO2 than foals born at sea level due to low inspired oxygen and compensatory hyperventilation occurring at altitude.

Methods: Sixteen foals were studied. Arterial blood gas analysis was performed within 1 h of foaling and subsequent samples were evaluated at 3, 6, 12, 24 and 48 h post partum. Data were compared to those previously reported in healthy foals born near sea level.

Results: Mean PaO2 was 53.0 mmHg (7.06 kPa) within 1 h of foaling, rising to 67.5 mmHg (9.00 kPa) at 48 h post partum. PaCO2 was 44.1 mmHg (5.88 kPa) within one hour of foaling, falling to 38.3 mmHg (5.11 kPa) at 48 h. Both PaO2 and PaCO2 were significantly lower in foals born at 1500 m elevation than those near sea level at several time points during the first 48 h.

Conclusions and potential relevance: Foals at 1500 m elevation undergo hypobaric hypoxia and compensatory hyperventilation in the first 48 h. Altitude specific normal arterial blood values are an important reference for veterinarians providing critical care to equine neonates.
Equine laminitis: Induced by 48 h hyperinsulinaemia in Standardbred horses
Authors: De LAAT M. A. , McGOWAN C. M. , SILLENCE M. N. , POLLITT C. C.
Published: July 2010

Reasons for performing study: Hyperinsulinaemia is known to induce laminitis experimentally in healthy ponies with no history of the condition. Horses are more insulin sensitive than ponies and whether prolonged hyperinsulinaemia and euglycaemia would have a similar laminitogenic effect requires study.

Objectives: To determine if laminitis results when the prolonged euglycaemic hyperinsulinaemic clamp technique (p‐EHC) is applied to clinically normal Standardbred horses, and to monitor hoof wall temperature seeking an association between vascular activity and laminitis development.

Methods: Eight young, clinically normal Standardbred horses were assigned into 4 pairs and within each pair, one was assigned randomly to either treatment (n = 4) or control (n = 4) groups. Treated horses received continuous infusions of insulin and glucose until clinical signs of laminitis developed, at which point the horses were subjected to euthanasia. Control horses received an equivalent volume of a balanced electrolyte infusion for the same period. Hoof wall surface temperature (HWST) was monitored continuously throughout the experimental period.

Results: All horses in the treatment group were calculated to have normal insulin sensitivity. All treated horses, and none in the control group, developed laminitis (P = 0.01). Pronounced digital pulses were a feature of the treatment group, while insignificant digital pulses occurred in control horses. HWST was higher and less variable in treated horses once hyperinsulinaemia was established.

Conclusions: Healthy Standardbred horses subjected to prolonged hyperinsulinaemia develop laminitis within 48 h, demonstrating that laminitis in horses can be triggered by insulin.

Potential relevance: Insulin resistance and the associated hyperinsulinaemia place horses and ponies at risk of developing laminitis. This study demonstrates a need for prompt management of the persistent hyperinsulinaemia seen in some endocrinopathies.
Occlusal fissures of the equine cheek tooth: Prevalence, location and association with disease in 91 horses referred for dental investigation
Authors: RAMZAN P. H. L. , PALMER L.
Published: July 2010

Reason for performing study: Fissures of the occlusal surface of the equine cheek tooth are poorly understood and their association with dental disease is unknown.

Objective: To describe the prevalence and location of occlusal fissures in the cheek teeth (CT) of a group of horses referred for dental investigation/treatment, and determine association with intercurrent dental disease.

Methods: Digital video recordings of oral endoscopic examinations for all horses referred to the Rossdales Equine Hospital for dental investigation from November 2006 to June 2009 were reviewed. Location of occlusal fissures in relation to both Triadan tooth position and pulpar secondary dentine was recorded; direction of fissure and concurrent involvement of enamel was also documented. The CT location considered at the time of examination to be the primary site/s of disease was correlated with presence of fissures on these teeth.

Results: 91 cases meeting the inclusion criteria were identified. Occlusal fissures were documented in 58.2% (53/91) cases, with a total of 227 CT being affected. Fissures were most prevalent mid‐arcade. The majority (92.1%) of fissures in maxillary CT were associated with the caudal palatal pulp horn. Fissures in mandibular CT were predominantly associated with the buccal pulp horns (95.7%). There was no significant difference in the median number of CT with fissures in relation to gender. There was no correlation between age (r2= 0.01) of horse and number of CT with fissures. A significantly greater number of CT with multiple occlusal fissures was found in mandibular compared to maxillary arcades. No correlation was found between presence of fissures and location of individual CT considered to be primarily responsible for presentation.

Conclusions: Occlusal fissures in this group of animals were common and not correlated to primary site of dental disease.

Potential relevance: In horses subjected to dental investigation, occlusal fissures of the cheek teeth should not be considered an indicator of tooth compromise. Location and direction of fissure propagation in most cases is inconsistent with occlusal fissures being causally implicated in slab fractures of cheek teeth, although site predilection may indicate a possible association with masticatory forces.
Clinical and imaging features of suspected prodromal fracture of the proximal phalanx in three Thoroughbred racehorses
Authors: RAMZAN P. H. L. , POWELL S. E.
Published: July 2010

Sagittal fracture of the proximal phalanx (P1) is an important musculoskeletal injury of the performance horse. Although widely considered to be monotonic in nature, there is emerging evidence that some P1 fractures may have stress‐injury aetiology. Three cases are described in which imaging features found were suggestive of prodromal bone injury. All cases returned to full performance use after a period of rest. The authors conclude that it is possible that some P1 fractures in the Thoroughbred racehorse may develop through stress/fatigue injury pathways. It is proposed that intervention prior to overt fracture may be possible in some cases.
Return to work following unilateral enucleation in 34 horses (2000–2008)
Authors: UTTER M. E. , WOTMAN K. L. , COVERT K. R.
Published: July 2010

Reasons for study:The effect of unilateral enucleation on vision and potential loss of performance in horses has received little study.

Objective:To evaluate the likelihood of return to prior discipline following unilateral enucleation in horses, assessing the role of age at enucleation, equine discipline, reason for enucleation, time to vision loss and eye enucleated.

Hypothesis:Unilateral enucleation has no significant effect on likelihood of return to work in horses, for both right and left eyes, across age and discipline.

Method:A retrospective review of medical records identified 92 horses that underwent unilateral enucleation at the University of Pennsylvania New Bolton Center from April 2000–April 2008. Case variables determined from the medical record included breed and sex of horse, age at enucleation, which eye was enucleated, reason for enucleation and onset of vision loss. Pre‐ and post operative occupations were determined by telephone interview with the owner or trainer of each horse.

Results:Based on hospital surgery logs, 92 enucleations were performed over the 8 year period and 77 records were available for review, with follow‐up information available for 34 horses. Of these, 29/34 (85%) horses returned to work in pleasure or trail riding (11/13), flat racing (7/10), hunter/jumpers (4/4), dressage (3/3), group lessons (1/1), eventing (1/1), steeplechase (1/1) and as a broodmare (1/1). Four of 5 horses (4/34, or 12% sample) that did not return to work (2 pleasure and 2 racing) were retired due to anticipated or perceived decrease in performance or behaviour change following unilateral enucleation, with the remaining horse retired from racing for lameness issues unrelated to enucleation. Twenty‐two of 25 horses (88%) with acute vision loss and 7/9 horses (78%) with gradual vision loss returned to their previous discipline.

Conclusions:Horses are able to return to a variety of occupations after unilateral enucleation.
Relationship of horse owner assessed respiratory signs index to characteristics of recurrent airway obstruction in two Warmblood families
Authors: LAUMEN E. , DOHERR M. G. , GERBER V.
Published: July 2010

Reasons for performing study: The horse owner assessed respiratory signs index (HOARSI‐1–4, healthy, mildly, moderately and severely affected, respectively) is based on owner‐reported clinical history and has been used for the investigation of recurrent airway obstruction (RAO) genetics utilising large sample sizes. Reliable phenotype identification is of paramount importance in genetic studies. Owner reports of respiratory signs have shown good repeatability, but the agreement of HOARSI with an in‐depth examination of the lower respiratory tract has not been investigated.

Objectives: To determine the correlation of HOARSI grades 3/4 with the characteristics of RAO and of HOARSI‐2 with the characteristics of inflammatory airway disease. Further, to test whether there are phenotypic differences in the manifestation of lung disease between families.

Methods: Seventy‐one direct offspring of 2 RAO‐affected Warmblood stallions (33 from the first family, 38 from the second) were graded as HOARSI‐1–4 and underwent a clinical examination of the respiratory system, arterial blood gas analysis, endoscopic mucus scoring, cytology of tracheobronchial secretion (TBS) and bronchoalveolar lavage fluid (BALF), and clinical assessment of airway reactivity to methacholine chloride.

Results: HOARSI‐3/4 animals in clinical exacerbation showed signs consistent with RAO: coughing, nasal discharge, abnormal lung sounds and breathing pattern as well as increased numbers of neutrophils in TBS and BALF, excessive mucus accumulation and airway hyper‐responsiveness to methacholine. HOARSI‐3/4 horses in remission only had increased amounts of tracheal mucus and TBS neutrophil percentages. Clinical phenotypes were not significantly different between the 2 families.

Conclusions and clinical relevance: HOARSI reliably identifies RAO‐affected horses in our population.
Dysautonomia in a six‐year‐old mule in the United States
Authors: WRIGHT A. , BEARD L. , BAWA B. , BRAS J.
Published: July 2010

Equine dysautonomia, also known as equine grass sickness (EGS), is a well documented disease in several countries. To the authors’ knowledge, EGS has not been reported previously in North America. This report describes EGS in a 6‐year‐old female mule in the USA. Failure initially to consider EGS resulted in a delayed diagnosis. EGS should be considered as a differential diagnosis and appropriate diagnostic tests performed in similar cases in North America.
Morphological study of tracheal shape in donkeys with and without tracheal obstruction
Authors: POWELL R. J. , Du TOIT N. , BURDEN F. A. , DIXON P. M.
Published: July 2010

Reason for performing study:There is limited information on the gross tracheal morphology of donkeys with or without tracheal abnormalities.

Objectives:To: 1) examine the morphology of tracheas of donkeys with and without clinical and/orpost mortemevidence of tracheal obstruction; 2) record the cross‐sectional dimensions and shapes of tracheal rings at fixed sites; and 3) document prevalence, sites and characteristics of detected tracheal abnormalities.

Methods:The tracheas of 75, predominantly aged (median age 30 years, range 7–48 years) donkeys that died or were subjected to euthanasia on humane grounds were examined. Five had severe dyspnoea due to tracheal obstruction (with intercurrent lung disease in 3), while 7 hadpost mortemevidence of severe tracheal airway obstruction. Every 5th tracheal ring was dissected free and the inner and outer vertical and transverse dimensions and cross sectional areas were measured. Each dissected ring was photographed and the shape of the trachea was classified as normal or, in one of 6 abnormal grades, according to the type and degree of structural abnormality present.

Results:The tracheas had a mean of 43 (range 34–50) tracheal rings that tended to be more oval in shape in the distal cervical region. Only 31.2% of rings examined had a circular to oval shape. Dorso‐ventral flattening was present in 0.9% of tracheal rings, dorsal ligament separation in 24.4%, slight cartilage deformity in 26.0%, moderate cartilage deformity in 10.4%, marked cartilage deformity in 1.9% and miscellaneous other abnormalities in 4.9% of tracheal rings. The 12 donkeys withanteorpost mortemevidence of tracheal obstruction had significantly increased tracheal abnormality grade in comparison to the remaining donkeys.

Conclusions and potential relevance:Structural tracheal abnormalities are present in most old donkeys, but generally do not cause clinical problems in these sedentary animals unless intercurrent pulmonary disease is present.
Cerebral aneurysm clips in the 3-tesla magnetic field
Authors: Kakizawa Yukinari , Seguchi Tatsuya , Horiuchi Tetsuyoshi , Hongo Kazuhiro
Published: July 2010

Object

The aim of this study was to evaluate cerebral aneurysm clips, and to know in more detail the characteristics of currently available clips in the 3-T magnetic field.

Methods

According to the protocol recommended by the American Society for Testing and Materials (ASTM), the authors conducted quantitative evaluation for displacement force and qualitative evaluation for torque in 52 aneurysm clips and 48 samples of raw materials in the 3-T environment.

Results

The largest displacement force occurred near the bore opening, and the force was directed to the isocenter. Deflection angles of all objects in this study were within 45°. The translational force in the peripheral position in the bore was larger than that in the center, and the translational force in the magnetic field was proportional to the weight of the objects. The proportion coefficients varied depending on the metallic materials. In the titanium alloy, the deflection angle was also detected to be approximately 2°, although no response was observed in titanium in a previous report. This behavior was similar to that of the Elgiloy and Phynox materials in the 1.5-T environment. No difference was observed among the groups of shapes (straight, bent, and fenestrated). The amount of torque that occurred was dependent on the clip's or material's loop and bent shape. The torque on the titanium was perpendicular to the torque on the other materials (which was perpendicular to the magnetic field).

Conclusions

Care must be taken with patients near the bore opening while moving them to the center of the magnet's bore on the MR imaging table. Although all the clips examined in this study met the ASTM requirements, the titanium alloy clips are preferable in the 3-T environment for safety's sake. Suitably sized clips should be selected for the aneurysm size, because the translational force increases proportionally to the object's weight.