Critical Thermalization of a Disordered Dipolar Spin System in Diamond.

Statistical mechanics underlies our understanding of macroscopic quantum systems. It is based on the assumption that out-of-equilibrium systems rapidly approach their equilibrium states, forgetting any information about their microscopic initial conditions. This fundamental paradigm is challenged by disordered systems, in which a slowdown or even absence of thermalization is expected. We report the observation of critical thermalization in a three dimensional ensemble of ∼10^{6} electronic spins coupled via dipolar interactions. By controlling the spin states of nitrogen vacancy color centers in diamond, we observe slow, subexponential relaxation dynamics and identify a regime of power-law decay with disorder-dependent exponents; this behavior is modified at late times owing to many-body interactions. These observations are quantitatively explained by a resonance counting theory that incorporates the effects of both disorder and interactions.

Nanometre-scale thermometry in a living cell.

Sensitive probing of temperature variations on nanometre scales is an outstanding challenge in many areas of modern science and technology. In particular, a thermometer capable of subdegree temperature resolution over a large range of temperatures as well as integration within a living system could provide a powerful new tool in many areas of biological, physical and chemical research. Possibilities range from the temperature-induced control of gene expression and tumour metabolism to the cell-selective treatment of disease and the study of heat dissipation in integrated circuits. By combining local light-induced heat sources with sensitive nanoscale thermometry, it may also be possible to engineer biological processes at the subcellular level. Here we demonstrate a new approach to nanoscale thermometry that uses coherent manipulation of the electronic spin associated with nitrogen-vacancy colour centres in diamond. Our technique makes it possible to detect temperature variations as small as 1.8 mK (a sensitivity of 9 mK Hz(-1/2)) in an ultrapure bulk diamond sample. Using nitrogen-vacancy centres in diamond nanocrystals (nanodiamonds), we directly measure the local thermal environment on length scales as short as 200 nanometres. Finally, by introducing both nanodiamonds and gold nanoparticles into a single human embryonic fibroblast, we demonstrate temperature-gradient control and mapping at the subcellular level, enabling unique potential applications in life sciences.

Room-temperature quantum bit memory exceeding one second.

Stable quantum bits, capable both of storing quantum information for macroscopic time scales and of integration inside small portable devices, are an essential building block for an array of potential applications. We demonstrate high-fidelity control of a solid-state qubit, which preserves its polarization for several minutes and features coherence lifetimes exceeding 1 second at room temperature. The qubit consists of a single (13)C nuclear spin in the vicinity of a nitrogen-vacancy color center within an isotopically purified diamond crystal. The long qubit memory time was achieved via a technique involving dissipative decoupling of the single nuclear spin from its local environment. The versatility, robustness, and potential scalability of this system may allow for new applications in quantum information science.

Scalable architecture for a room temperature solid-state quantum information processor.

The realization of a scalable quantum information processor has emerged over the past decade as one of the central challenges at the interface of fundamental science and engineering. Here we propose and analyse an architecture for a scalable, solid-state quantum information processor capable of operating at room temperature. Our approach is based on recent experimental advances involving nitrogen-vacancy colour centres in diamond. In particular, we demonstrate that the multiple challenges associated with operation at ambient temperature, individual addressing at the nanoscale, strong qubit coupling, robustness against disorder and low decoherence rates can be simultaneously achieved under realistic, experimentally relevant conditions. The architecture uses a novel approach to quantum information transfer and includes a hierarchy of control at successive length scales. Moreover, it alleviates the stringent constraints currently limiting the realization of scalable quantum processors and will provide fundamental insights into the physics of non-equilibrium many-body quantum systems.

The Stent-Supported Percutaneous Angioplasty of the Carotid Artery vs. Endarterectomy Trial.

The Stent-Supported Percutaneous Angioplasty of the Carotid Artery versus Endarterectomy (SPACE) Trial is investigating if both treatment modalities are equivalent in the treatment of severe symptomatic carotid stenoses. Patients with symptomatic (transient ischaemic attack or minor stroke) stenosis (above 50% following the North American Symptomatic Endarterectomy Trial criteria) eligible for both methods can be recruited into this trial. The primary endpoint is the incidence of an ipsilateral stroke or death between randomisation and day 30 after treatment. Surgeons as well as the interventionalists have to demonstrate their expertise prior to participation in the trial. Funding is mostly by public institutions (Federal Ministry of Education and Research and German Research Foundation). An external monitoring is applied. Thirty-two centres are currently taking part in the SPACE Trial that has been running in Germany, Austria and Switzerland for 3 years, and they have been able to recruit a total of around 670 patients. The definitive results of this study cannot be expected before 3-5 years.

[Evaluation of stent-protected angioplasty for theray of symptomatic stenoses of the carotid artery. SPACE and other randomized trials]. / Evaluation der stentgeschützten Angioplastie zur Therapie von symptomatischen Stenosen der A. carotis. SPACE und andere randomisierte Studien.

During recent years, stent-protected angioplasty of the carotid artery (SPAC) has become an alternative to endartectomy (CEA) in many centers. Despite many case reports, case series, and open records, it has not been proven that these therapeutical regimens are comparable regarding complication rates and long-term outcome. Until now, only three randomized trials were published on this theme, two of them only as abstracts. This is not sufficient for answering the question of whether SPAC is a good alternative to CEA. At present, four major, randomized, multicenter trials are being run (EVA3S in France, CREST in the US, ICSS in Great Britain and several other countries, and SPACE in Germany and Austria). About 7,300 patients will be included in these trials. At present, 24 centers are participating in the SPACE trial, recruiting about 350 patients. It has been prospectively agreed that EVA-3S, ICSS, and SPACE will combine their results after completion of initial randomization and follow-up to conduct a combined European meta-analysis of the data. Three to 5 years are needed until these trials' final results will be published. Until then, stent-protected angioplasty should be done only under the consideration that it has not been scientifically evaluated.

Urgent carotid endarterectomy for stroke in evolution.

BACKGROUND: Carotid endarterectomy (CEA) is well established as the elective treatment for moderate or severe carotid stenoses with a history of neurologic symptoms. In contrast, the merits of carotid revascularisation performed in emergency in patients with acute stroke or fluctuating neurological deficit remain controversial. PATIENTS AND METHODS: A total of 445 CEAs were performed on 424 patients for 212 (48%) asymptomatic and 233 (52%) symptomatic carotid stenoses within a 5 years period between January, 1995, and December, 1999. Of the latter, CEA was performed in emergency on 16 patients (3.8%) within 4 to 24 hours after the onset of symptoms. Patients selected for urgent surgery fulfilled the following criteria: acute onset of fluctuating hemispheric neurological symptoms, significant carotid pathology, absence of cerebral hemorrhage, uncompromised vigilance and stable cardiopulmonary conditions. Selected patients presented with a crescendo-TIA (n = 7) or fluctuating neurological deficits (n = 9) corresponding to a contralateral carotid stenosis. RESULTS: Following CEA, the neurological deficits improved instantaneously to complete recovery in 9 patients. The symptoms of 4 patients improved to non-disabling deficits, remained unchanged in one and worsened in 2 patients from hemihypaesthesia to hemiparesis. 14/16 patients were discharged within 8 days after admission. The neurologic status after discharge did not deteriorate in any of the patients during follow up of 19.3 +/- 13 months, but improved in 4 of the patients. CONCLUSION: Our retrospective study suggests that rescue CEA may be beneficial for selected patients with stroke in evolution and fluctuating neurological deficits. Careful adherence to selection criteria, intraoperative shunting, intensive care post surgery surveillance and an experienced team are recommended.

Harmonization of vascular surgical training in Europe. A task for the European Board of Vascular Surgery (EBVS).

The competence of vascular surgeons defined as the level of skill, knowledge and experience necessary to safely perform vascular surgical procedures is determined to a high degree by the quality of the preceding training. In Europe, quality assurance of vascular surgical training, unlike in the USA, is not uniform and is not the responsibility of a centralized European authority, but is a matter in which the different countries have autonomous regulations. Consequently, different targets for duration, contents and general principles for training in vascular surgery have been set. Although in the past this may not have been a problem, the unification of countries in the European Community (EC), at present known as the European Union (EU), has changed this perspective because there is increasing impetus towards a mutual recognition of trade and education between member states. In 1975, EC directive 75/362 was adopted, which insured 'freedom of migration' for medical doctors along with many other professional trades (Publications of the European Communities no. L167, 30-6-1975, p. 1). This directive implicated that certificates, diplomas and other documents issued by the national competent authorities proving medical qualification allowed physicians to practice in any EU country. In order to make this law practical it seems essential that specialist training programmes throughout the EU should conform to certain agreed basic standards. The objective of this article is to present an overview on the current pattern of vascular surgical training in Europe. In addition, the structures that were established during the recent years to promote uniformly high standards of training in vascular surgery throughout the EU will be discussed.

[Surgical and interventional therapeutic possibilities in aneurysms of the subclavian artery]. / Chirurgische und interventionelle Therapiemöglichkeiten von Aneurysmen der Arteria subclavia.

Aneurysms of the subclavian artery are extremely rare and most commonly caused by arteriosclerosis, trauma or thoracic outlet syndrome. Less frequently seen causes also include syphilis, cystic media necrosis or tuberculosis or congenital anomalies. The presence of a subclavian aneurysm can give rise to various symptoms such as a pulsating supraclavicular mass, peripheral embolism or brachial plexus compression. Generally, surgical intervention is undertaken involving ligation and extirpation of the aneurysm followed by interposition of either a saphenous vein- or synthetic vascular graft. Recent diversifications in potential therapeutic strategies include the clinical application of transluminally positioned stents for the treatment of vascular lesions. In the literature review we found more than 260 published cases of surgically treated subclavian aneurysms and additional 17 subclavian aneurysms treated by endoluminal stent application. From 1992-1997 5 subclavian aneurysms were resected in our hospital. In four cases a vein graft of the vena saphena magna and in one case a PTFE graft were used. The sensory ischaemic deficit regressed in the further follow up in four of the five cases. Patency was checked postoperatively by ultrasound sonography, angiography or MR-angiography.

[Surgical aortic fenestration in acute thoracoabdominal aortic dissection with abdominal malperfusion and end organ ischemia]. / Die Aortenfensterungsoperation bei akuter thoracoabdominaler Aortendissektion mit abdominaler Malperfusion und Endorganischämie.

Intestinal, renal, spinal or peripheral arterial ischemia or failure of branch artery recanalization following initial prosthetic repair of thoracoabdominal aortic dissection is still a problem, with high morbidity and mortality. Five consecutive patients with acute thoracoabdominal aortic dissection (two type A dissections, three type B dissections) suffering from concomitant intestinal, renal, spinal and acute peripheral arterial ischemia are reported. Considering the anatomical and pathophysiological basis of thoracoabdominal aortic dissection and concomitant organ ischemia, the aortic fenestration procedure as a primary or secondary operative approach succeeded in restoring blood flow in all cases without complications. Assessment of the long-term results after 3 years revealed that all patients are doing well without any residual complaints. We conclude that in the case of persistent or secondary onset of aortic branch artery ischemia following initial prosthetic repair of either type A or type B dissection, aortic fenestration can be recommended immediately as a staged operative approach. Primary abdominal aortic fenestration is justified in acute type B dissection when end-organ ischemia becomes the focus of clinical deterioration.

Semi-closed femoropopliteal thromboendarterectomy: a prospective study.

OBJECTIVE: to study the primary patency rates of angioscopically controlled thromboendarterectomies of the superficial femoral artery. DESIGN: prospective open study. METHODS: between 1990 and 1995, femoropopliteal thromboendarterectomies were performed in 63 patients (41 male, 22 female). Postoperative follow up was performed at 3- to 6-month intervals using non-invasive pressure measurements plus IVDSA at 1 year. RESULTS: eight patients were not evaluable, leaving 55 patients eligible for follow-up analysis. Postoperative complications (arteriovenous fistulas, false aneurysms) were observed in 5.4% of patients. Immediate perioperative occlusions occurred in 7.3%, early occlusions in 21.8% and late occlusions in 16.4% of all cases. The mean follow-up was approximately 57 months. The mean primary patency rate at 5 years was 44.5% (28 patients with the superficial femoral artery still open). Six patients died during the follow-up period. CONCLUSIONS: in contrast to the very positive reports found in recent literature, this prospective study shows a lower five-year patency rate for semi-closed femoropopliteal thromboendarterectomy than for bypass grafting. Thromboendarterectomy cannot be considered as a standard procedure in revascularisation of the femoropopliteal region.

The abdominal aortic fenestration procedure in acute thoraco-abdominal aortic dissection with aortic branch artery ischemia.

OBJECTIVE: Diagnostic work-up and treatment strategies have improved the prognosis of acute thoraco-abdominal aortic dissection. Little attention to aortic branch artery ischemia or even failed restoration following prosthetic repair of thoraco-abdominal dissection still merit a problem with high morbidity and mortality. SETTING: Department of Vascular Surgery, Technische Universität München, Germany. PURPOSE: Reflecting on visceral and neurological ischemic complications in acute thoraco-abdominal aortic dissection indications and limitations of the abdominal-aortic-fenestration procedure are discussed with a review on our own clinical experience and the results reported in the literature. CONCLUSIONS: The abdominal-aortic-fenestration procedure is accomplished with minimal deterioration of the critically ill patient. In new onset or relief of aortic branch ischemia, following initial prosthetic repair of either type A or B dissection aortic fenestration is found to be an effective and secure adjunctive procedure to restore the blood flow of compromised organs. Primary abdominal aortic fenestration is recommended instead of prosthetic repair in cases of acute type B dissection. It is the treatment of choice because of branch artery ischemia becoming the focal point of deterioration.

Topographic analysis of proliferative activity in carotid endarterectomy specimens by immunocytochemical detection of the cell cycle-related antigen Ki-67.

BACKGROUND: On the basis of contradictory results found in animal experiments and coronary atherectomy tissue, there is an ongoing debate about the significance of cellular proliferation in human atherosclerosis. In the present prospective study, the cell cycle-related antigen Ki-67 was detected for topographic determination of cell turnover in distinct regions of human carotid endarterectomy specimens harvested en bloc by surgical biopsy. METHODS AND RESULTS: After en bloc resection, serial sections of 26 consecutive carotid lesions were analyzed by histomorphological examination and immunohistochemistry. Thereby, 319 high-power fields were attributed to separate plaque regions defined as follows: distal boundary of the lesion with normal intima, plaque shoulder, core region, and diffuse intimal thickening. Endothelial cells, smooth muscle cells, T cells, and macrophages were identified by immunostaining of factor VIII-related protein, alpha-actin, CD68, and CD45R0. An overall proliferation index of 0.49+/-1.05% was yielded by positive anti-Ki-67 immunolabeling, predominantly in macrophage-rich areas characterized by high cell density (>1000 cells/mm2) as well as in reparative sites in the perimeter of atheroma, intramural thrombosis, plaque hemorrhage, and neovascularization (P<.01). Few or no signs of proliferation activity were found in normal intima, in areas of dense alpha-actin positivity, or adjacent media. As shown by double immunostaining, macrophages and unspecified mesenchymal cells represented the prevailing proliferating cell type. CONCLUSIONS: Our results suggest that proliferation in advanced human carotid lesions is confined to the intima and focally concentrated in central plaque regions negative for alpha-actin. Furthermore, it apparently occurs primarily as part of inflammatory processes and structural repair predominantly involving macrophages, as well as unspecific mesenchymal cells.

Migration behavior of human smooth muscle cells cultivated from restenotic and primary lesions.

Subintimal smooth muscle cell (SMC) migration is considered an essential determinant of arteriosclerosis and neointimal formation. In this study, a cell culture model was established to characterize migration activity of SMCs originating from restenotic and primary lesions. Plaques from symptomatic stenoses of 32 patients (19 men, 13 women; 4 carotid, 17 peripheral, 11 coronary lesions) were removed by percutaneous atherectomy or direct operative approach. Ten patients suffered from recurrent stenosis. Cell cultures were established by explantation of tissue samples. By indirect immunofluorescence microscopy, SMCs were shown to be the predominant cell type of all advanced lesions irrespective of their origin. The spontaneous cellular motility of SMCs was analyzed in vitro by means of a computer-assisted observation system. Cells of all groups exhibited random motility. SMC migratory velocity was found to be significantly (P < 0.001) greater in cells from restenotic lesions than in those from primary plaques. In conclusion, migration behavior of human SMCs originating from arteriosclerotic lesions may be quantified in vitro as a functional determinant characterizing restenotic versus primary lesions.

[High-degree bilateral carotid stenoses]. / Hochgradige bilaterale Karotis-Stenosen.

The indication for carotid endarterectomy in patients with unilateral stenotic lesions as well as the operative risk in patients with bilateral disease is still controversial among experts. We performed a retrospective analysis in our patients with bilateral carotid endarterectomy. 578 patients underwent carotid endarterectomy at our institution from 1986-1992: 54 patients (9.3%) had bilateral carotid disease. 30% of these patients were asymptomatic and 16% had symptoms from both sides. Surgical results concerning the optimal restoration of blood supply (75%) and the occurrence of recurrent stenosis (8%) were comparable for patients with unilateral and bilateral carotid endarterectomy. On the contrary, in patients with bilateral carotid disease, both the operative morbidity (2.8%) and mortality (1.8%) were increased as compared to the total study population (1.9% and 0.45% resp.). Carotid endarterectomy is very effective in preventing stroke especially in patients with multiple vessel disease as compared to the natural history of these lesions.

[Ablation of venous valves with Nd-Yag laser--an alternative to conventional valvulotomy?]. / Venenklappenablatio mit Nd-Yag Laser--eine Alternative zur konventionellen Valvulotomie?

The careful removal of venous valves during in situ venous bypass procedures is a problem that has not been completely solved. In this experimental study, valve ablation with the Nd-Yag laser was compared with conventional valvulotomy. The investigation was performed in vitro using human vein segments with a length of 20 cm. Conventional valvulotomy was performed 16 times, 20 valves were removed with a 400 mu-fibre and 26 with the hot tip. The results were evaluated by endoscopy, light and electron microscopy. There were no vein perforations with the valvulotome and the hot tip. Endothelial damage was documented in 85% with the valvulotome and was reduced significantly to 58% with the 400 mu-fibre. With the hot tip endothelial lesions were seen in only 30%. Valve remnants were always present with the valvulotome and in no more than 15% with the hot tip. Electron microscopy supported these results in general. There was no endothelial damage in 69%.

[Orthotopic arteriovenous fistula in dialysis patients: a special application of fluid dynamic processes]. / Die orthotopen arteriovenösen Fisteln beim Dialysepatienten: eine Sonderstellung fluiddynamischer Problematik.

Our experiments describe the flow patterns in translucent models of AV fistulas. The elasticity of the models is similar to human vessels walls. Dying of particular flow threads with methylene blue visualizes the flow and its disturbances in 4 classical models. The flow dynamics were investigated with parallel inflow. The volume flow was constant at 200 and 400 ml/min, with a volume flow ratio of 80:20. The flow pattern in side to side fistulas and in end to side fistulas with a narrow angle show regions of separation. This may lead to microthrombus formation and early failure. High shear stress causes endothelial lesions and thus induces stenosing intimal reactions. A favourable flow pattern was seen in end to side fistulas with a broad angle, as well as in end to end fistulas.

Severe bilateral carotid stenosis.

An analysis of the relevant data from the Veterans Affairs Cooperative Study Group in asymptomatic patients, showed that 26 of the 32 ipsilateral strokes occurred during the first two years of clinical follow-up. Furthermore, as observed in the medical group, half the neurologic outcome events were strokes and were not preceded by transient ischemic attacks. In the North American Symptomatic Carotid Endarterectomy Trial over a 2-year period, 45 percent of those with occlusion had a stroke compared to 15 percent in the surgical group. These data dispel the traditionally held view that patients with severe contralateral disease should not be subjected to surgery. However, the referral of patients to centers capable of low rates of surgical complications is essential in a plan that includes carotid endarterectomy with optimal medical management.