Ascending Si diffusion into growing GaN nanowires from the SiC/Si substrate: up to the solubility limit and beyond.

We report a novel mechanism that allows the incorporation of Si into GaN nanowires up to and beyond the solubility limit. This mechanism is documented during the growth on vicinal (misoriented) SiC/Si hybrid substrates having the step bunches. Nanowires that are grown at these locations become heavily Si doped. Such high Si concentrations were verified by secondary-ion mass spectrometry. Photoluminescence data also point to very high carrier concentrations. Moreover, Raman spectroscopy together with quantum chemical modelling shows the build up of Si into Ga sites and indicates even the possibility of the formation of a Ga(Si)N solid solution. The microscopic mechanism responsible for heavy doping and even alloying is diffusion driven by the mechano-chemical effect, which allows for the extremely efficient injection of Si atoms into the nanowires from the step bunches at the vicinal SiC/Si substrates.

Role of hole confinement in the recombination properties of InGaN quantum structures.

We study the isolated contribution of hole localization for well-known charge carrier recombination properties observed in conventional, polar InGaN quantum wells (QWs). This involves the interplay of charge carrier localization and non-radiative transitions, a non-exponential decay of the emission and a specific temperature dependence of the emission, denoted as "s-shape". We investigate two dimensional In0.25Ga0.75N QWs of single monolayer (ML) thickness, stacked in a superlattice with GaN barriers of 6, 12, 25 and 50 MLs. Our results are based on scanning and high-resolution transmission electron microscopy (STEM and HR-TEM), continuous-wave (CW) and time-resolved photoluminescence (TRPL) measurements as well as density functional theory (DFT) calculations. We show that the recombination processes in our structures are not affected by polarization fields and electron localization. Nevertheless, we observe all the aforementioned recombination properties typically found in standard polar InGaN quantum wells. Via decreasing the GaN barrier width to 6 MLs and below, the localization of holes in our QWs is strongly reduced. This enhances the influence of non-radiative recombination, resulting in a decreased lifetime of the emission, a weaker spectral dependence of the decay time and a reduced s-shape of the emission peak. These findings suggest that single exponential decay observed in non-polar QWs might be related to an increasing influence of non-radiative transitions.

Clinical endpoints in peripheral endovascular revascularization trials: a case for standardized definitions.

BACKGROUND: Endovascular therapy is a rapidly expanding option for the treatment of patients with peripheral arterial disease (PAD), leading to a myriad of published studies reporting on various revascularization strategies. However, these reports are often difficult to interpret and compare because they do not utilize uniform clinical endpoint definitions. Moreover, few of these studies describe clinical outcomes from a patients' perspective. METHODS AND RESULTS: The DEFINE Group is a collaborative effort of an ad-hoc multidisciplinary team from various specialties involved in peripheral arterial disease therapy in Europe and the United States. DEFINE's goal was to arrive at a broad based consensus for baseline and endpoint definitions in peripheral endovascular revascularization trials for chronic lower limb ischemia. In this project, which started in 2006, the individual team members reviewed the existing pertinent literature. Following this, a series of telephone conferences and face-to-face meetings were held to agree upon definitions. Input was also obtained from regulatory (United States Food and Drug Administration) and industry (device manufacturers with an interest in peripheral endovascular revascularization) stakeholders, respectively. The efforts resulted in the current document containing proposed baseline and endpoint definitions in chronic lower limb PAD. Although the consensus has inevitably included certain arbitrary choices and compromises, adherence to these proposed standard definitions would provide consistency across future trials, thereby facilitating evaluation of clinical effectiveness and safety of various endovascular revascularization techniques. CONCLUSION: This current document is based on a broad based consensus involving relevant stakeholders from the medical community, industry and regulatory bodies. It is proposed that the consensus document may have value for study design of future clinical trials in chronic lower limb ischemia as well as for regulatory purposes.

[Cardiopulmonary exercise testing before and after blood donation]. / Spiroergometrische Leistungsdiagnostik vor und nach Blutspende.

BACKGROUND: The link between haemoglobin and physical performance was established a long time ago and is the underlying principle of blood doping. Blood loss on the other hand decreases physical capacity. The aim of this study is to evaluate physical performance loss and underlying mechanisms following voluntary blood donation. METHOD AND PATIENTS: Eleven voluntary subjects (four female) completed a symptom-limiting cardio-pulmonary exercise test before and after blood donation (500 mL blood). RESULTS: The haemoglobin value decreased by 1.2 mg/dL (9%, p < 0.001), maximal oxygen uptake by 9% (p = 0.006), maximal work rate by 13% (p = 0.001) and duration of exercise fell from 663 down to 607 seconds (p = 0.005). Anaerobic transition occurred at 81.2% and 71.5% of maximal oxygen uptake before and after blood donation, respectively (p = 0.001). Subjects who practise recreational endurance sports appear to be more effected by endurance loss. The haemoglobin value was the only significant predictor of maximal oxygen uptake in regression analysis (p < 0.001). CONCLUSION: Maximal physical performance is impaired after blood donation. Haemoglobin decline accounts for the decreased oxygen uptake. As a consequence thereof the anaerobic transition occurs earlier. Subjects not engaged in regular sports activity did not experience a decline in their capacity. Inclusion of the haemoglobin value into equations predicting maximal oxygen uptake could improve prediction precision.

Pharmacologic and hemodynamic influences on the rate of isovolumic left ventricular relaxation in the normal conscious dog.

We studied the effects of acute pharmacologic and hemodynamic interventions on isovolumic left ventricular relaxation in 19 conscious dogs using micromanometer tip catheters. Isoproterenol (11 studies) augmented peak rate of rise of left ventricular pressure [(+) dP/dt] by 1,275+/-227 (SE) mm Hg/s (P < 0.001) and dP/dt at an isopressure point of 35 mm Hg during isovolumic relaxation [(-) dP/dt(35)] by 435+/-80 mm Hg/s (P < 0.001). Peak (-) dP/dt decreased by 467+/-89 mm Hg/s (P < 0.002). The time constant, T, derived from the logarithmic fall of pressure during isovolumic relaxation, shortened from 20+/-2.8 to 14.9+/-1.8 ms (P < 0.003). Calcium (11 studies) increased peak (+) dP/dt and (-) dP/dt(35) (both P < 0.0001); peak (-) dP/dt was unchanged. T shortened from 20.4+/-1.8 to 17.3+/-1.5 ms (P < 0.002). Volume (13 studies) did not affect either dP/dt or T. Phenylephrine (13 studies) augmented peak (-) dP/dt, but reduced (-) dP/dt(35) (both P < 0.01); T lengthened from 22.1+/-1.5 to 32.5+/-1.5 ms (P < 0.01). In 15 studies, rapid atrial pacing increased peak (+) dP/dt and (-) dP/dt(35) (both P < 0.01). In the first post-pacing beat, peak (-) dP/dt and (-) dP/dt(35) decreased (both P < 0.01), although peak (+) dP/dt increased further. T paralleled values of (-) dP/dt(35). In five dogs, beta adrenergic blockade had no significant effect on any variable after calcium, volume, or phenylephrine infusion or during or after atrial pacing when the pre-and post-propranolol states were compared. We conclude that positive inotropic interventions augment both left ventricular contraction and relaxation. The changes in isovolumic relaxation are independent of alterations in sympathetic tone produced by beta-adrenergic blockade. Peak (-) dP/dt may not be a valid measure of left ventricular relaxation rate during acute alterations in inotropic state or afterload.

Endovascular stenting of a renal transplant vein.

We describe successful endovascular stenting of a high-grade stenosis of a renal transplant vein in a 53-year old patient. Kidney transplantation had been performed due to IgA nephropathy and the patient had become symptomatic two months after uneventful recovery from operation.

Systolic pressure--diameter relations in the normal conscious dog.

Pressure--diameter loops were generated in normal, conscious dogs during left ventricular contraction by means of endocardial ultrasonic gauges and micromanometers. Studies were made in the control state, during volume and pressure loading, and during enhancement of contractility. The diameter at the end of ejection was linearly related to systolic pressure, and the pressure--diameter relation at end-ejection was not affected by changes in preload. However, this relation was substantially displaced by changes in inotropic state, suggesting that the instantaneous pressure--length plane produced by pressure loading is unique to a given level of contractility.

Changes in phasic femoral artery flow induced by various stimuli: a study with percutaneous pulsed Doppler ultrasound.

Transcutaneous blood flow measurements were performed by means of pulsed Doppler ultrasound flowmeter in the femoral artery of healthy subjects. The pulsatile flow pattern was changed characteristically from resting state by postocclusive reactive hyperaemia, by the application of amyl nitrite, xanthinol nicotinate, and angiotensin amide. During reactive hyperaemia systolic flow was increased, diastolic reverse flow was abolished, and the forward flow continued throughout diastole. Amyl nitrite augmented thenegative flow phase and reduced mean flow, while xanthinol nicotinate decreased the negative component and augmented mean flow. Angiotensin amide produced enhancement of the average flow by elevating systolic and diastolic flow equally over the base line. In each of these interventions the changes in flow were determined mainly by variations during the diastolic flow phase.

17 beta-estradiol inhibits proliferation and migration of human vascular smooth muscle cells: similar effects in cells from postmenopausal females and in males.

OBJECTIVES: Cardiovascular disease is rare in premenopausal women, but increases after the menopause when hormone replacement therapy reduces coronary events. Vascular smooth muscle cell (SMC) proliferation and migration occur in atherosclerosis, restenosis and venous graft disease. We studied the effects of 17 beta-estradiol on SMC proliferation and migration. METHODS: SMC were cultured from saphenous veins of postmenopausal women and age-matched men. Cell growth was determined by 3H-thymidine incorporation and cell counting. Migration of SMC was assessed in 4-well chambers. SMC were seeded in one corner and PDGF-BB in filter paper glued onto the opposite wall. RESULTS: PDGF-BB (5 ng/ml for 24 h) similarly stimulated 3H-thymidine incorporation in female (511 +/- 57%; n = 8) and male (528 +/- 62%; n = 12) SMC. This was reduced by 17 beta-estradiol (10(-8)-10(-6) M; female 313 +/- 52%; male 337 +/- 54%; P < 0.05). PDGF-BB increased the number of SMC (P < 0.0001 at 10 days) obtained from females (153 +/- 3%; n = 5) and males (150 +/- 4%; n = 5), which was inhibited by 17 beta-estradiol (10(-6) M; female 134 +/- 7%; male 128 +/- 5%; P < 0.05). Similar results were obtained with basic fibroblast growth factor. In contrast to 17 beta-estradiol, another steroid (dexamethasone) had no effects on 3H-thymidine incorporation in these cells stimulated with PDGF-BB, PDGF-BB (0.01-1 ng) stimulated SMC migration (P < 0.05) which was inhibited by 17 beta-estradiol (10(-10)-10(-6) M; n = 5; P < 0.005). CONCLUSION: 17 beta-Estradiol inhibits growth-factor-induced SMC proliferation and migration regardless of gender. These effects of 17 beta-estradiol may contribute to its cardiovascular protective properties in postmenopausal women during replacement therapy.

Double-blind, randomized comparison of systemic continuous infusion of 0.25 versus 0.50 mg/kg/24 h of alteplase over 3 to 7 days for treatment of deep venous thrombosis in heparinized patients: results of the European Thrombolysis with rt-PA in Venous Thrombosis (ETTT) trial.

Thirty-two patients with acute, proximal-vein thrombosis were treated with heparin and alteplase (0.25 versus 0.5 mg/kg/24 h during 3-7 days) in a randomized, double-blind, multicenter, European (ETTT) trial. The treatment resulted in a decrease of the venographic Marder's score from 18 (6-25) to 13 (2-24) units (median, range) in Group I (0.25 mg/kg/24 h, n = 15, median decrease 3.0, p = 0.32) and from 17.5 (3-33) to 15.5 (0-27) in Group II (0.5 mg/kg/24 h, n = 16, median decrease 4.0, p = 0.23). Comparison of the sequential venograms could be performed in 14 cases of Group I and in 15 cases in Group II. A minority of patients showed substantial partial recanalization of the initially obstructed veins on the control venogram (one in each treatment group) and most of the control venograms showed either thrombus size reductions (5 in Group I, 7 in Group II) or no change or even deterioration (8 in Group I, 7 in Group II). Major bleedings were observed in 7 patients (7/32, 22%), 5 of them occurring in Group II (5/17, 29%). Thus, the results of the ETTT trial show that the used low dosages of alteplase administered intravenously over 3-7 days in heparinized patients cannot be recommended as a treatment for patients with deep venous thrombosis of lower limbs and/or pelvis. Further studies are needed to define a more suitable dosage regimen of alteplase in this indication.

Effects of changes in preload, afterload and inotropic state on ejection and isovolumic phase measures of contractility in the conscious dog.

Despite much investigation, the usefulness of various indexes employed clinically for detecting alterations in ventricular contractility in the intact circulation remains controversial. The effects of acute preload, afterload and contractility changes on both ejection and isovolumic phase measures of left ventricular function were analyzed in normal, trained conscious dogs instrumented with micromanometers and endocardial ultrasonic diameter gauges. Rapid volume overload increased the excursion of the left ventricular diameter (delta LVD) by 7 percent above the control level, but mean velocity of circumferential shortening (VCF) did not change significantly; peak rate of left ventricular pressure rise (dP/dt) increased by 11 percent and (dP/dt)/DP40 (DP = developed pressure) was augmented by 10 percent, but maximal [(dP/dt)/LVP], or "Vpm," decreased by 20 percent. Pressure overload by phenylephrine infusion decreased delta LVD by 15 percent and mean VCF fell by 26 percent; peak dP/dt and (dP/dt)/DP40 remained unaltered, but VPM was reduced by 37 percent. Isoproterenol augmented peak dP/dt by 55 percent, and (dP/dt)/DP40, Vpm and mean VCF were increased comparably. Propranolol decreased these measures equally by about 16 percent. Therefore, in the conscious animal in the steady state, isovolumic phase indexes were mildly influenced by acute volume loading, wheras ejection phase indexes were not. Acute increases in aortic pressure markedly reduced ejection phase measures, whereas the isovolumic indexes were unaffected. All of the indexes studied were comparably sensitive to acute alterations in contractility, but we conclude that no single measure can always be used for defining an acute contractility change in the intact circulation.

Renal artery stenosis and evaluation of the effect of endoluminal dilatation. Comparison of dynamic CT scanning and I-131-OIHA renogram.

Percutaneous transluminal dilatation was performed in 16 patients with hypertension and renal artery stenoses. Dynamic CT scanning and an I-131-OIHA renogram was performed before and after dilatation. After the procedure (follow-up greater than or equal to 3 months) the hypertension was assessed clinically as normalized in six, improved in five, and unimproved in five patients. The attenuation difference at dynamic CT scanning between both kidneys at the time of peak enhancement following intravenous bolus injection of contrast material diminished significantly from 16 +/- 4 HU before to 7 +/- 6 HU (P = 0.015) after dilatation in the patient group with cured hypertension, whereas the relative opacification of the poststenotic kidneys increased from 43.6 +/- 2.4% to 47.4 +/- 1.7% (P = 0.014). The results of the Isotope renogram showed a similar increase of the relative function of the poststenotic kidneys from 33 +/- 5% to 38 +/- 7% (P = 0.227) and significant improvement of the clearance from 112 +/- 34 to 175 +/- 48 ml/min/1.73m2 (P = 0.040). The results of both techniques did not significantly change in the group of patients with only moderate improvement of hypertension. Deterioration of the results occurred in those patients in which the hypertension remained unchanged.

Pseudoaneurysm of femoral artery after catheterisation: treatment by a mechanical compression device guided by colour Doppler ultrasound.

BACKGROUND: Femoral artery pseudoaneurysm is a significant complication in patients undergoing diagnostic or therapeutic catheterisation. First choice treatment for pseudoaneurysm is freehand ultrasound guided compression repair, which is time consuming and uncomfortable for the patient and operator. AIM: To explore a mechanical compression device (FemoStop) as an alternative treatment for iatrogenic femoral artery pseudoaneurysm. METHODS: Fourteen patients with pseudoaneurysm were considered for treatment with FemoStop after a brief freehand ultrasound guided compression repair to confirm the compressibility of the lesion. The FemoStop compression was applied for 20 minutes. The result was controlled with colour Doppler ultrasound, and a second cycle of 20 minutes followed if necessary. RESULTS: FemoStop compression was successful in 13 of the 14 patients. The mean compression time was 33 minutes (range, 20-60). The mean number of compression periods was 1.6 (range 1-3). FemoStop compression was successful in all 11 patients not taking anticoagulants and in two of three patients receiving anticoagulants. The mean compression time in patients given oral or intravenous anticoagulants was longer (50 v 27 minutes). Colour Doppler ultrasound 12 hours after the procedure indicated no recurrence of pseudoaneurysm in the 13 patients with initial success. CONCLUSIONS: FemoStop compression for iatrogenic pseudoaneurysm is feasible, and as safe and effective as freehand ultrasound guided compression repair. It is more comfortable for the patient and operator, and probably more economical than freehand compression.

Unusual pseudoaneurysms after catheterization: successful treatment by ultrasound-guided compression.

Postcatheterization pseudoaneurysms occur mostly in the femoral artery. Two patients (both women, aged 67 and 59 years) undergoing percutaneous transluminal angioplasty (PTA) at our institution presented pseudoaneurysms in unusual locations, one in the brachial and one in the popliteal artery. Because of good experiences with ultrasound-guided compression repair (UGCR) in the femoral artery, we also successfully performed this noninvasive treatment on the two patients. Follow-up at 28 and 12 months, respectively, after the procedure, showed no instances of recurrence. As with the excellent results of UGCR in the femoral artery, we believe that this new modality is also the treatment of choice in iatrogenic pseudoaneurysms of the arm and popliteal arteries.

Ultrasonic-pathologic comparison of postangioplasty myointimal hyperplasia and primary atheroma of the superficial femoral artery.

The purpose of this study was to characterize postangioplasty myointimal hyperplasia as compared to primary atheroma of superficial femoral arteries using color-coded duplex sonography (CCD), and to correlate sonographic findings with the histopathology of samples obtained from these lesions by catheter atherectomy (Redha-cut device). Preinterventionally, homogeneity, echogeneity, and the surface of plaques were described using CCD in nine cases with secondary stenoses after percutaneous transluminal angioplasty and in seven cases with primary atheroma. Myointimal hyperplasia of femoral restenoses showed a homogeneous (7 of 9 vs. 1 of 7) and hypoechogenic (7 of 9 vs. 0 of 7) wall thickening compared to primary atheromas (p < 0.05). Primary atherosclerotic plaques showed a rather heterogeneous, hypo- and hyperechogenic ultrasonic appearance with or without echo shadowing in six of seven cases. The surface of restenoses was more often regular than that of primary atherosclerotic lesions, but this finding did not reach statistical significance (6 of 9 vs. 2 of 7, p = 0.14). Thrombotic material appeared homogeneous and hypoechogenic in three of five cases and could not be discriminated from intimal hyperplasia. In summary, postangioplasty intimal hyperplasia is characterised by a hypoechogenic, homogeneous, rather regularly confined vessel wall thickening and can be differentiated from primary atheroma at CCD.

Magnetic resonance angiography of abdominal vessels: early experience using the three-dimensional phase-contrast technique.

Based on three-dimensional acquisition of three sequences sensitive to one flow-direction, abdominal magnetic resonance phase-contrast angiography (MRA) was performed in 13 volunteers and 20 patients. The subjects received no antiperistaltic medication and were allowed to breath normally during the three acquisition periods of 11 minutes. The frequency of demonstration of the normal aorta, superior mesenteric and right and left renal arteries was 100%/100%/91%/100%, and of the inferior vena cava, splenic, superior mesenteric and portal veins was 92%/67%/92%/100%, respectively, whereas other abdominal vessels were seen less constantly. In renal artery stenosis or occlusion, MRA detected eight out of nine pathological arteries, missed only a minimal stenosis and was never false positive. In all 10 cases of portal hypertension, MRA demonstrated the venous collaterals detected by conventional angiography and in six cases showed more collaterals, particularly paravertebral vessels. A Budd-Chiari syndrome was investigated as well. If the accuracy of MRA can be proved in larger studies, it may become an important diagnostic tool in evaluating abdominal vascular pathology, such as renal artery stenosis or portal hypertension.

Combination of short- and long-term catheter thrombolysis for peripheral arterial occlusion.

To save time and expenses we developed a combined program of local short-term catheter thrombolysis (CTL) in the angiographic laboratory followed by a long-term CTL on the ward if necessary to achieve patency. Out of 66 patients with arterial occlusion in the femoro-popliteal region the occluded segment was re-opened by short-term CTL alone in 22 patients (36%), and in 24 out of the remaining 44 patients by long-term CTL, giving a total primary success rate of 71%. Angiographic analysis showed that primary clinical success depended on the patency of run-off vessels in the calf after CTL. Complications occurred in five patients, necessitating surgical revision in only one. Two years after intervention 64% of the primarily recanalized arteries were still patent as shown by non-invasive examination.

Angioplasty of the terminal aorta: follow-up of 20 patients treated by PTA or PTA with stents.

Twenty patients with distal aortic stenosis were treated by PTA for intermittent claudication and, in 3, 'blue toe' syndrome. Additionally, a self-expandable endoprosthesis (stent) was inserted into the aorta in three of the patients. The overall primary success rate (including those with a stent) was 100% with all patients becoming free of symptoms. Mean arm-ankle pressure difference decreased from 48 mmHg to 9 mmHg (P less than 0.01). During a median follow-up period of 15 months no patient had recurrence of claudication, embolism, or deterioration of the non-invasive parameters. Thus, PTA seems suitable for treating stenoses of the abdominal aorta, even in the presence of distal microembolization. Balloon dilatation, with the addition of stents in resistant cases, offers a valuable alternative to surgery in distal aortic stenosis.

[Vascular endoprosthesis of femoro-popliteal occlusive disease]. / Die vaskuläre Endoprothese bei femoro-poplitealer Verschlusskrankheit.

A self-expanding vascular endoprosthesis (wall stent) was implanted in 26 patients with femoropopliteal occlusive disease following recurrent stenosis or occlusion after percutaneous angioplasty. Implantation was successful in all cases and there were no complications. Five of the 26 patients developed a thrombosis in the first nine days; in four of these, thrombolysis was successful. Patency rate after one month was 96%, after three months 95%, after six months 85% and after nine months 87%. In order to prevent thrombosis after implantation, anticoagulant therapy is indicated. Poor distal flow encourages intimal hyperplasia and therefore recurrences.

Improvement of Raynaud's phenomenon after liver transplantation for end-stage primary biliary cirrhosis.

Successful orthotopic liver transplantation may reverse extrahepatic manifestations of the primary chronic liver disease. A well documented improvement of Raynaud's phenomenon, following successful liver transplantation realized for end-stage primary biliary cirrhosis, using repetitive angiological examination and capillary microscopy is presented.