Improving the identification of hydrologically sensitive areas using LiDAR DEMs for the delineation and mitigation of critical source areas of diffuse pollution

Identifying critical source areas (CSAs) of diffuse pollution in agricultural catchments requires the accurate identification of hydrologically sensitive areas (HSAs) at highest propensity for generating surface runoff and transporting pollutants. A new GIS-based HSA Index is presented that improves the identification of HSAs at the sub-field scale by accounting for microtopographic controls. The Index is based on high resolution LiDAR data and a soil topographic index (STI) and also considers the hydrological disconnection of overland flow via topographic impediment from flow sinks. The HSA Index was applied to four intensive agricultural catchments (~7.5-12km(2)) with contrasting topography and soil types, and validated using rainfall-quickflow measurements during saturated winter storm events in 2009-2014. Total flow sink volume capacities ranged from 8298 to 59,584m(3) and caused 8.5-24.2% of overland-flow-generating-areas and 16.8-33.4% of catchment areas to become hydrologically disconnected from the open drainage channel network. HSA maps identified 'breakthrough points' and 'delivery points' along surface runoff pathways as vulnerable points where diffuse pollutants could be transported between fields or delivered to the open drainage network, respectively. Using these as proposed locations for targeting mitigation measures such as riparian buffer strips reduced potential costs compared to blanket implementation within an example agri-environment scheme by 66% and 91% over 1 and 5years respectively, which included LiDAR DEM acquisition costs. The HSA Index can be used as a hydrologically realistic transport component within a fully evolved sub-field scale CSA model, and can also be used to guide the implementation of 'treatment-train' mitigation strategies concurrent with sustainable agricultural intensification.

Injury to the axillary artery, a complication of fixation using a locking plate

The proximal humerus internal locking system is an internal fixation device consisting of a low-profile plate and locking screws, which is used for the fixation of three- and four-part fractures of the proximal humerus. We describe a case in which the screws cut out of the humeral head causing injury to the axillary artery necessitating urgent removal of the implant.

The foot-and-mouth disease epidemic in Dumfries and Galloway, 2001. 2: Serosurveillance, and efficiency and effectiveness of control procedures after the national ban on animal movements

After the foot-and-mouth disease (FMD) epidemic in Dumfries and Galloway in south-west Scotland in 2001, serosurveillance of sheep remaining in the 3 km radius Protection Zones around Infected Premises (IPS), and within a 10 km radius of IPS, revealed no evidence of infection. The epidemic was brought under control by a range of traditional techniques: slaughter of all animals on IPS and of veterinary-assessed Dangerous Contacts (DCS), movement restrictions, biosecurity, tracing of potential sources and spread of virus, and surveillance of At-Risk premises. Novel pre-emptive slaughter of FMD-susceptible animals on premises contiguous to IPS, and small ruminants and pigs on premises within 3 km of IPSs, commenced after the epidemic had peaked. Most of the traditional control procedures were undertaken quickly and with appropriate priority. Animals on IPS were usually slaughtered within one day of confirmation, and veterinary-assessed DCS within two days of confirmation of relevant IPS (a median of two days). The pre-emptive contiguous and 3 km culls took somewhat longer (medians of five and 17 days, respectively). IPS were most commonly identified as a result of reporting by farmers or their veterinarians (72 per cent of IPS); veterinary clinical patrols identified 16 per cent, while veterinary assessment of DCS and tracing each identified 5 per cent. No evidence of infection was found on any pre-emptively contiguously culled premises, and IPS were declared only on three 3 km cull premises. The time from estimated first lesion to end of slaughter on an IP was found, by regression analysis, to be a key component in effective control, manifested by a reduction in the estimated dissemination rate (EDR); there was little evidence that the intensity of contiguous culling affected the EDR. Patrols and serological surveillance of residual animals within 10 km of IPS, supported by more extensive evidence from elsewhere in the UK, suggested that cryptic infection in sheep was not widespread. Ultimately, there was insufficient evidence to support the effectiveness of 3 km pre-emptive culling as a control procedure.

The foot-and-mouth disease epidemic in Dumfries and Galloway, 2001. 1: Characteristics and control

The foot-and-mouth disease epidemic in Dumfries and Galloway in south-west Scotland comprised 177 infected premises (IPS) in 24 geographical clusters, and ran from March 1 until May 23, 2001. Initial seeding of infection was by livestock (predominantly sheep) that had passed through Longtown Market in adjacent Cumbria. Thereafter, spread within existing, and to new, clusters was associated with the movement of personnel and vehicles, with further transmission by Longtown Market contacts and across common boundaries. Sheep and cattle premises were equally affected. After the peak of the epidemic at the beginning of the third week of March, the upper possible limit of attack rates for premises contiguous to IPS, and premises within 3 km, remained around 10 per cent, with new clusters emerging more distantly. Control procedures included traditional methods of slaughter of all animals on IPS and, elsewhere, of animals considered by veterinary assessment to be Dangerous Contacts; movement restrictions; enhanced biosecurity; tracing of potential sources and spread of virus; and surveillance of premises subsequently considered at risk. These methods were supplemented by the novel pre-emptive slaughter, without veterinary assessment, of all susceptible livestock on all premises contiguous to IPS, and of small ruminants and pigs within a 3 km radius (known as the Protection Zone) around IPS. In total, approximately 80,000 cattle, 564,000 sheep, 2600 pigs and 500 goats were slaughtered, the novel methods accounting for 29 per cent of all cattle and 75 per cent of all sheep killed. Limitations of existing national databases necessitated the development of local databases to administer control procedures.

Combined surgical and radiological procedures

Background

The aim was to audit the effect of provision of an interventional theatre on the management of vascular disease in a tertiary centre.

Methods

All patients undergoing joint vascular surgical and radiological procedures during 20 months were reviewed. Data are presented with respect to type of procedure, initial success and length of hospital stay.

Results

Between October 1997 and July 1999, 100 combined procedures were performed in an endovascular operating theatre. Sixty of these were for stent-graft repair of abdominal aortic aneurysm and are excluded from further analysis. Forty patients (23 men and 17 women, of median age 65 (range 37–80) years) underwent combined procedures for claudication (nine), rest pain (13), tissue necrosis (five), acute ischaemia (seven), iliac aneurysm (three), amaurosis fugax (one), arteriovenous malformation (one) and subclavian vein occlusion (one).

Combined intervention was successful initially in 35 patients. Of the five failures, three were technical (not possible to cross an occluded vessel) and two were due to absence of run-off vessels. There was no perioperative death. Median hospital stay was 9 (range 1–116) days.

Conclusion

These data confirm that patients requiring both radiological and surgical intervention can be treated successfully within the confines of an interventional operating suite. Cooperation and coordination between surgeon and radiologist allows the tailoring of procedures to the individual patient's needs.

Percutaneous ablation of an internal iliac aneurysm using tissue adhesive

We report the percutaneous injection of tissue adhesive (Tisseal, Immuno, Vienna, Austria) to ablate a 12-cm internal iliac aneurysm. The complex history of this lesion included previous surgery for a ruptured aortic aneurysm, attempted repair of the internal iliac aneurysm, and several embolization procedures. These factors precluded further open repair or transcatheter techniques and dictated the choice of a more direct approach.

Merkel cell carcinoma of the abdominal wall

Merkel cell carcinoma is a rare highly malignant tumour. There have been previous descriptions of the CT appearances of this tumour, but to our knowledge this is the first MRI description. MRI may be a more sensitive method of initial evaluation of the local extension of the primary tumour.

Work-load generated by the establishment of a non-heart beating kidney transplant programme

The work-load generated by a non-heart-beating donor (NHBD) kidney transplant programme over a 3-year period is reported. A total of 73 referrals were made, 64 from the Accident department and 9 from the wards. Organ procurement was performed in 24 cases (33%) and resulted in the retrieval of 44 kidneys. Reasons for failure to achieve organ procurement were; refused consent (n = 13; 18%), relatives unavailable to ask for consent (n = 9; 12%), technical problems with catheter insertion or perfusion (n = 10; 14%), transplant staff unavailable (n = 1; 1%), long asystolic period (n = 8; 11%) and donor unsuitable for other reasons (n = 8; 11%). Of the 44 kidneys retrieved, 30 were transplanted locally, 8 were transplanted at other United Kingdom centres and 6 were discarded. Locally transplanted NHBD kidneys represented 21% of the total transplant programme during the time period under study. We conclude that NHBD kidneys are a good source of additional organs for transplantation, but only one-third of referrals result in a successful procurement procedure. Moreover, the setting up of a successful programme is labour-intensive and requires a highly committed staff.

The effect of a surveillance programme on the patency of synthetic infrainguinal bypass grafts

OBJECTIVES

Vein graft surveillance is widely acknowledged to be of benefit in improving graft patency at least in the first year after arterial bypass surgery. The aim of this study was to examine the effect of a surveillance programme on the patency of synthetic infrainguinal bypass grafts.

DESIGN

A prospective study of 69 consecutive prosthetic bypass grafts was undertaken over a 3 year period.

METHODS

Patients were seen at 3 monthly intervals after surgery and underwent measurement of ankle brachial pressure indices and a colour Duplex scan of the graft.

RESULTS

The surveillance programme was able to detect treatable lesions in five grafts and in the run-off vessels of two other grafts prior to occlusion. However 14 grafts failed after the first 30 days, 12 of which were not predicted by the surveillance programme.

CONCLUSIONS

Surveillance appears to be of limited benefit in the maintenance of patency of synthetic infrainguinal bypass grafts.

The development of an in vitro flow model of human saphenous vein graft intimal hyperplasia

OBJECTIVE

Although the role of blood flow has been investigated in animal models of intimal hyperplasia, there have been no detailed studies in intact human vein owing to the difficulties in designing a suitable laboratory model. The aim of this study was to develop a flow model of human vein graft intimal hyperplasia.

METHODS

Organ cultures of human saphenous vein were exposed to laminar flow by culturing in a closed circulatory system under predetermined conditions of venous and arterial shear stress for 14 days. Following fixation and processing, paraffin sections were immunostained and neointimal thicknesses measured.

RESULTS

It was found that arterial flow completely inhibited neointima formation, but venous flow only partly suppressed the response when compared with vein cultured under static conditions. These results are in agreement with previous in vivo studies in a primate graft model, where increased shear stress inhibited intimal proliferation.

CONCLUSION

The endothelial cell is believed to be the key mediator of haemodynamic effects which influence smooth muscle cell proliferation, and the flow rig developed in this study offers the potential to study inter-cellular interactions within the intact vessel. Furthermore, this method provides the facility to study the effects of different flow conditions on segments of vein from the same patient. This model has scope for further development and sophistication which may ultimately lead to increasing our understanding of the aetiology of vein graft stenoses, and hence formulation of preventative strategies.

The long-term outcome of infrainguinal vein graft surveillance

OBJECTIVES

Vein graft surveillance is of proven benefit in improving graft patency at least in the first year after arterial bypass surgery. The aim of this study was to look at the longer term outcome of a vein graft surveillance programme on graft patency.

METHODS

One hundred and twelve consecutive vein grafts in 106 patients were prospectively entered into a vein graft surveillance programme. The median (range) follow up was 34 (1-76) months.

RESULTS

There were 23 (21%) early (less than 1 month) failures and a further 15 grafts occluded during follow up. The primary, primary assisted and secondary patencies at 4 years were 27%, 59% and 67% respectively. Thirty-eight grafts (34%) developed at least one stenosis at a median interval of 5 months after the operation. Eight (21%) of these stenoses occurred more than 12 months after surgery and would have been missed had surveillance been curtailed after 1 year.

CONCLUSIONS

The benefits of graft surveillance extend beyond one year and surveillance should therefore continue indefinitely.

Reversible ophthalmoplegia in CPEO

PURPOSE

To present a case of improvement of ocular motility in a patient with chronic progressive external ophthalmoplegia (CPEO) with Coenzyme Q10.

METHODS

Coenzyme Q10 300 mg daily was given for three years with a three-day trial period of 200 mg daily after one year. Ocular ductions were measured by synoptophore.

RESULTS

Ocular ductions improved with treatment with Coenzyme Q10.

CONCLUSION

Coenzyme Q10, is effective in limiting the severity of ophthalmoplegia in this case.

Percutaneous transluminal angioplasty of infrainguinal vein graft stenosis: long-term outcome

The aim of this prospective study was to examine the long-term outcome of infrainguinal vein graft stenosis managed by percutaneous transluminal angioplasty (PTA) as first-line treatment. Thirty-three infrainguinal vein graft stenoses detected by graft surveillance during a 44-month period were treated initially by PTA. The median (range) follow-up after angioplasty was 39 (18-56) months. Although 19 stenoses were successfully treated by a single PTA, 14 stenoses recurred at a median (range) interval of 8.5 (1-39) months. Restenosis occurred more frequently in the distal third of a graft (P = 0.002) compared with that in the proximal or mid-grafts, and restenosis was more common in in situ than reversed vein grafts (P = 0.03). It is concluded that infrainguinal vein graft stenoses were successfully treated by single PTA. There was, however, a high restenosis rate after angioplasty of stenosis in the distal third of a vein graft and, while approximately one third of such stenoses can be treated by a single PTA, the optimal management of recurrent stenosis requires further investigation.

The fate of infrainguinal PTFE grafts and an analysis of factors affecting outcome

Ninety-five infrainguinal polytetrafluoroethylene (PTFE) bypass grafts were performed in 90 patients. Indications for surgery were severe claudication in 23 limbs (24%) and rest pain or tissue necrosis in 72 limbs (76%). Sixty-seven grafts (71%) were to the above knee popliteal artery and 28 (29%) to the infragenicular vessels. The primary, primary assisted and secondary graft patencies at 2 years in limbs with rest pain or tissue necrosis were 37, 42 and 46% respectively with a limb salvage rate of 65%. A univariate analysis was performed to identify preoperative risk factors which affected graft patency. Smoking, an ankle systolic pressure of less than 50 mmHg, presentation with rest pain or tissue necrosis and single vessel run-off all had a significant adverse effect on graft patency. However, multivariate analysis revealed that smoking was the only significant adverse variable. These findings support the view that PTFE grafts for limb salvage are worthwhile even if the distal anastomosis is below the knee and run-off is via a single vessel provided that the patient stops smoking.

Stereoscopic evoked responses to crossed and uncrossed disparity accompanying simulated refractive error

Evoked potentials were recorded to the occurrence of a disparate stimulus in dynamic random dot stereograms. Seven adult males, all of whom had vision which was normal or corrected to normal, participated in the experiment. Subjects viewed 100 ms duration stimuli which embodied 30 arc min of either crossed or uncrossed disparity under four conditions of spherical overcorrection: -0.25, +1.0, +2.0, +3.0 dioptres. The first condition, essentially normal refraction, yielded reliable behavioural reports of the stimulus and clear evoked potentials to both crossed and uncrossed disparity. With increasing overcorrection the behavioural reports became less reliable, and the evoked potentials were degraded for both conditions of disparity. The responses to the crossed disparity condition, however, showed significantly less degradation in both behavioural and electrophysiological measures. The implications of this finding may be that there are separate cortical subsystems for the processing of crossed and uncrossed disparity and that the former is more robust under non-ideal viewing conditions.

Evoked responses to distinct and nebulous stereoscopic stimuli

When geometric or contoured shapes are generated as disparity regions in dynamic random-dot stereograms, the question of whether the subject's response is evoked largely by boundaries and corners of the disparate region arises. To examine this question a disparate square was shifted randomly within a focal region at one millisecond intervals, resulting in a nebulous stimulus which "welled up" in the centre of the field of view. The technique may be regarded as an analogue of the defocusing technique used to resolve similar questions about evoked potentials to patterned stimuli. Average visual evoked potentials (VEP) were recorded from homolateral pairs of occipital and posterior temporal electrodes referred to a common midline prefrontal site. The latencies and amplitudes of VEP to distinct and nebulous stimuli were compared in a group of young normal adults, of whom 14 succeeded in perceiving and 14 failed to perceive the presented stimuli. Latencies of maximal response to distinct and nebulous stimuli were closely similar in the two groups (range N242-N252). Mean amplitudes of the peak response differed between perceivers and non-perceivers. The responses to nebulous stimuli were smaller than those to distinct stimuli in site-for-site comparisons in both groups. Even in short averaging runs a substantial VEP (about 3 microvolt) was recorded to nebulous stimuli in the perceiver group. It is suggested that both disparity and boundary features contribute to the VEP when this particular display system is used.

Measurement of dynamic stereoacuity and global stereopsis

Quantification of global stereopsis in addition to stereoacuity has been achieved by using dynamic random dot test patterns generated by inexpensive computer controlled integrated electronics. A pilot study revealed marked differences between the responses of a variety of clinically defective and normal subjects.

Infant strabismus: a 25-year review of 750 cases

The review demonstrates that there is no justification for delay in treating babies who present with strabismus. A survey of 750 infants aged from 0 to 36 months among 5497 cases seen by an individual orthoptist over 25 years shows a decreasing use of surgery and an increasing proportion of fully functional results over this time. It emphasizes that no infant is too young for assessment and treatment.

Methylamine and ammonia transport in Saccharomyces cerevisiae

Methylamine (methylammonium ion) entered Saccharomyces cerevisiae X2180-A by means of a specific active transport system. Methylamine uptake was pH dependent (maximum rate between pH 6.0 and 6.5) and temperature dependent (increasing up to 35 C) and required the presence of a fermentable or oxidizable energy source in the growth medium. At 23 C the vmax for methylamine transport was similar 17 nmol/min per mg of cells (dry weight) and the apparent Km was 220 muM. The transport system exhibited maximal activity in ammonia-grown cells and was repressed 60 to 70 percent when glutamine or asparagine was added to the growth medium. There was no significant derepression of the transport system during nitrogen starvation. Ammonia (ammonium ion) was a strong competitive inhibitor of methylamine uptake, whereas other amines inhibited to a much lesser extent. Mutants selected on the basis of their reduced ability to transport methylamine (Mea-R) simultaneously exhibited a decreased ability to transport ammonia.