The influence of climate on peatland extent in Western Siberia since the Last Glacial Maximum

Boreal and subarctic peatlands are an important dynamical component of the earth system. They are sensitive to climate change, and could either continue to serve as a carbon sink or become a carbon source. Climatic thresholds for switching peatlands from sink to source are not well defined, and therefore, incorporating peatlands into Earth system models is a challenging task. Here we introduce a climatic index, warm precipitation excess, to delineate the potential geographic distribution of boreal peatlands for a given climate and landscape morphology. This allows us to explain the present-day distribution of peatlands in Western Siberia, their absence during the Last Glacial Maximum, their expansion during the mid-Holocene, and to form a working hypothesis about the trend to peatland degradation in the southern taiga belt of Western Siberia under an RCP 8.5 scenario for the projected climate in year 2100.

Obesity is a risk factor for recurrence after incisional hernia repair

BACKGROUND

Any individualisation of incisional hernia repair requires a profound knowledge of risk factors for recurrence.

METHODS

A series of 160 patients underwent incisional hernia repair and were prospectively followed up at 3, 6, 12, and 24 months after surgery. We analysed the importance of various variables to predict recurrence.

RESULTS

An overall recurrence rate of 11% ( n=17) was observed. The risk for recurrence was not significantly affected by any of the clinical variables except for obesity ( P=0.03). Even when controlling for the influence of age, gender, hernia size, and surgical technique, obesity remained a significant predictor with a rate ratio of 1.10 per unit BMI (95%-CI: 1.02-1.18; P=0.01).

CONCLUSION

This and other studies found hernia recurrence to be more likely in obese patients. Probably, such patients, therefore, should receive mesh rather than suture repair.

[In vitro validation of intravascular ultrasound, computerized and magnetic resonance tomography in diagnosis of atherosclerotic vascular segments in comparison with direct magnification radiography]

The depiction of atherosclerotic vessel abnormalities is a prerequisite for percutaneous interventional therapy and long-term observations of peripheral artery disease. The aim of this in-vitro study was to determine the potentials and limitations of 12.5 and 20 MHz intravascular ultrasound, computed tomography and magnetic resonance (MR) imaging in comparison to direct magnification radiography for the localization and quantification of peripheral vessel wall calcifications. Forty-three postmortem, human iliac segments were examined by intravascular ultrasound (12.5 and 20 MHz), computed tomography and magnetic resonance tomography (gradient echo-and spin echo-technique). For comparative analysis, each segment was divided into eight sectors of 45 degrees each; using all five methods, the presence of calcified wall areas was examined in each sector, and luminal area (42 segments) and plaque area (32 isolated plaques) were quantitatively estimated. In the sonograms, the circumferential extension of the boundary between intima and media was measured. 122 of 344 sectors showed regional vessel wall calcifications. Sensitivity of 20 MHz intravascular ultrasound was 73% versus 59% with the 12.5 probe, specificity was 97% with 20 MHz, 96% with 12.5 MHz. Sensitivity of both 12.5 and 20 MHz intravascular ultrasound was higher with increased thickness of the calcified structures. 20 MHz ultrasound identified the intima-media boundary averaging 146.8 degrees of the vessel circumference; the corresponding value of 131.8 degree with 12.5 MHz did not differ significantly. Computed tomography detected calcifications with a sensitivity of 88%, specificity was 88%. With MR imaging, sensitivity of the gradient echo-technique was 94% versus a sensitivity of 86% with spin echo-technique. Quantification of luminal and plaque areas showed that luminal area was precisely estimated only by 20 MHz ultrasound (no significant difference to direct magnification radiography), whereas all other techniques showed significant overestimation. Plaque areas were markedly overestimated by computed tomography and MR imaging, too. In an in vitro set-up, intravascular ultrasound, MR tomography and computed tomography do not allow an authentic depiction of peripheral vessel wall architecture. Limited resolution, subintimal shadowing and and distortion are the main limitations of these new techniques so that details of regional vessel wall calcifications cannot be presented thoroughly. Relevant over-estimation of luminal and plaque areas must be considered.

[Significance of intravascular ultrasound in arteriosclerotic calcified intima plaques: in vitro comparison of 20 and 12.5 MHz transducers]

The aim of this in vitro study was to analyze the diagnostic performance of intravascular ultrasound (IVUS) in vessel wall calcifications and to compare the accuracy of mechanical 12.5 and 20 MHz transducers. Fourty-three sections of 10 vessels with signs of arteriosclerotic disease on pathologic examination were examined. Slices 500 microns thick were obtained and examined radiographically at 9 fold magnification. In each section, identical segments were defined, amounting to a total of 344 segments. The IVUS sections were analyzed by 3 experienced readers. For statistical evaluation ROC analysis was performed using magnification radiography as a reference. An area under the curve (AUC) of 0.79 was obtained for the 12.5 transducer and of 0.83 for the 20 MHz transducer. Additionally, sensitivity, specificity, and accuracy were determined. Sensitivity depended on the morphology, size, and density of the calcified lesions. We therefore conclude that the sensitivity of intravascular ultrasound concerning calcified arteriosclerotic plaques is limited and that there is no significant (p < 0.01) difference between mechanical 20 and 12.5 MHz transducers in examining iliac arteries.

In vitro correlation of intravascular ultrasound and direct magnification radiography for calcified arterial lesions

RATIONALE AND OBJECTIVES

Intravascular ultrasound (IVUS) is an adjunct to contrast angiography that gives additional information concerning the morphology of the vascular wall. The authors examined the accuracy of intravascular ultrasound (IVUS) in the evaluation of calcified lesions within the abdominal aorta and the iliac artery.

METHODS

Forty-nine human specimens (iliac artery, 26; abdominal aorta, 23) were examined using a 20-MHz 6.0-F ultrasound catheter, followed by magnification radiography of the same specimens using a newly developed microfocus x-ray tube. Magnification radiographs and ultrasound images were divided into identical sectors to analyze the morphology of calcified arteriosclerotic lesions.

RESULTS

A total of 644 sectors was analyzed. Sensitivity of intravascular sonography was 70%, specificity 53%. Sensitivity strongly depended on the morphology of the calcified lesions.

CONCLUSION

The detection of calcified arteriosclerotic lesions by means of IVUS revealed a sensitivity of 70% in an in vitro study using human specimens. However, the specificity of IVUS was only 53%, which is basically a random chance occurrence.