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.

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]

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.

[Surgical and interventional therapeutic possibilities in aneurysms of the subclavian artery]

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.

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.

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.

[Surgical aortic fenestration in acute thoracoabdominal aortic dissection with abdominal malperfusion and end organ ischemia]

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.

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.

Angioscope-guided neodymium yttrium-aluminium-garnet laser valvulotomy for in situ vein bypass

Valvulotomy for in situ vein bypass is commonly performed with a valvulotome. Although the procedure can be controlled through an angioscope, the dangers of intimal damage and valve remnants remain. An experimental study was designed to evaluate angioscopic laser valvulotomy compared with standard mechanical valvulotomy (n = 16). Two different laser probes, a bare 400-microns fibre (n = 20) and a 2-mm hot-tip (n = 26) were tested. Results were investigated by histology and scanning electron microscopy. Hot-tip laser valvulotomy achieved significantly better results than the 400-microns fibre. The Insitucat valvulotome yielded the worst results, with valve remnants in all cases and an 88 per cent rate of intimal damage. It is concluded that laser valvulotomy can be performed simply and safely with a very low incidence of valve remnants and intimal damage.

Coagulation in aortofemoral bifurcation bypass grafting

Few data are available on the pathophysiology of the coagulation system during aortic surgery. Cross-clamping of the aorta, intestinal eventeration and circulatory shock in ruptured aortic aneurysms are thought to cause coagulation disturbances and hyperfibrinolysis. A prospective study of several parameters of the clotting system, i.e. standard clotting tests, platelet count, indicators of fibrinolysis, inhibitors of the clotting cascade and proteases were measured perioperatively in aortobifemoral bypass grafts. Ten patients undergoing elective procedures and two emergency cases with ruptured aortic aneurysms were included. The standard clotting tests reflected the use of heparin. A similar course of ATIII, C1-inhibitor, alpha 2-antiplasmin, plasminogen and fibrinogen with a decrease during the operation and a return to almost normal values postoperatively, were due to intra-operative blood loss, haemodilution and a slight activation of the clotting cascade, as well as, hyperfibrinolysis. This observation was supported by the increased levels of euglobulin lysis and PMN-elastase and the resultant increase in some fibrinogen degradation products, indicating non-specific proteolysis. These changes were more pronounced in the two emergency cases, except for the heparin induced changes in PTT and thrombin time. It is concluded that non-specific proteolysis may be an important factor in the pathogenesis of clotting disorders in surgery of the aorta. Further research is needed to discover the pathways of non-specific proteolysis and its prevention by protease inhibitors.

[Functional results following complicated injuries of the extremities--how can they be improved?]

This study evaluates the critical points in the management of 48 patients with injured arteries of the lower limb between 1980 and 1986. 77% of the traumas were resultant from blunt vehicular traffic mishaps. 13 patients were treated within 6 h, 8 patients later than 6 h, 21 patients later than 24 h post injury. Delays in diagnosis occurred due to lack of or no indication for vascular trauma. Careful physical examination and aggressive use of angiography is essential in improving limb salvage rates, while doppler investigation may lead to improper diagnosis. Overall limb salvage was 69%, however, no reconstruction was possible in 6 cases (13%). 38 of the 42 arterial reconstructions required interposition of venous bypass grafts, four end to end anastomoses. Eleven patients had associated venous injuries, which in nine cases were repaired. Venous ligation in three cases was attributed with increased complication. In three cases ischemia time was shortened by the use of temporary javid shunts for rapid restoration of arterial flow. 50% of the patients were found to require fasciotomy, either pre- or postvascular repair. Early fasciotomy, however was found to be most beneficial. Fractures were treated in 15 cases with the external fixator, in 21 cases with internal fixation. Delayed revascularization after 24 h combined with aggressive debriding of muscle necrosis and the employment of vascularized muscular and skin flaps resulted in a decline in amputation rates and improved functional results.

Extended femoro-distal bypasses for limb salvage: are they worthwhile?

In this report on 93 patients with limb-threatening leg ischemia the surgical procedures applied were malleolar bypasses (14), sequential bypasses (12) and femoro-distal bypasses with adjunct AV fistulas (67). The first two methods resulted in favourable limb-salvage and patency rates. However the results of such reconstructions essentially depend on the quality of primary and secondary foot arcades. In peripheral calf and foot arterial occlusions we have applied a distal arteriovenous fistula as an adjunct measure to maintain bypass patency in the crural region. 67 patients were operated on according to this method: 30 females and 37 males with an average age of 70.3 years. 29% had rest-pain and 71% had gangrene. The majority had already been operated on at least once. 7 patients had been amputated contralaterally.

RESULTS

79% of the patients had a patent graft after one month. The incidence of limb salvage was 77%. At two years 47% of all grafts are still patent and the incidence of limb-salvage is 52%. However, this operation should be exclusively designed for limb-salvage and for cases with extremely poor run-off.

[Angioplasty in risk patients. Possibilities in advanced chronic arterial obstructive diseases (author's transl)]

In vascular diseases in which standardized methods cannot be applied in spite of clear indication, operative treatment is problematic. In the meantime, "extra-anatomic bypasses" have proved useful, being implantable also in patients with high operative risk. The surgical mortality in these patients is about 4% after implantation of an axillo-femoral bypass. The preoperative condition is improved by the extraanatomical bypass, a threatened extremity being retained in about 80%. The late results show a patency rate of 38% and are therefore far below those of the standardized procedure. The results of the femoro-femoral cross-over bypass are better here. The late results in this case with a patency rate of ca. 80% are only slightly worse than with the standard methods. The results of the "extrathoracal bypasses" with a patency rate after 5 years of 92% and a mortality of 0% is more favorable. This is the method of choice.

[Extracranial carotid stenosis and its sonographic diagnosis]

The direct Doppler examination of the carotid arteries as a method to detect and distinguish stenoses and occlusions of the common, internal, and external carotid arteries allows to decide on operability and indication for surgical treatment. The exact observation of the acoustical flow signals permits to a high degree an identification of even small stenoses and arteriosclerotic plaques. In 125 angiographical controls 95% of the sonographic diagnoses, in stenoses larger than 50% correct diagnosis could be established even up to about 99%. There were no false positive sonographic findings. Because of our good results we did not consider it necessary in recent time to perform an angiography before surgery in 25 patients. These patients had a high angiographic risk and there was a clear cut Doppler finding of an extreme stenosis in the internal carotid artery.

[Experiences with replantation of large limbs]

From November 1975 to August 1978 26 limb replantations were performed. All 5 lower extremities had to be reamputated. Of the 21 replanted arms 15 healed without major complications, 9 have regained sufficient function up to now; 3 others show signs of reinnervation.

[Experience with transvenous xeroarteriography in vascular surgery (author's transl)]

The edge contrast pattern in Xeroradiography allows blood vessels to be delineated with highly reduced concentration of radiopaque fluid. The contrast material is injected rapidly into a cubital vein. The brachial arteries are opacified 3--8 sec. and the femoral arteries about 7--15 sec. after the injection is finished. The arteriograms are of good quality which equals direct conventional angiography, if the vessels are not overlayed by bone structures. Thus the popliteal artery can be judged best in lateral view. The indications for transvenous Xeroarteriography are preoperative diagnosis especially in high risk patients, angiographic diagnosis of soft tissue tumors and postoperative control and documentation of vascular reconstruction in the extremities. Transvenous Xeroarteriography is a really noninvasive, painless and easy to handle method whiich allows visualization of peripheral vascular lesions and can be reproduced at short intervals without any risk.

[Surgical treatment of cerebral ischemia. Indications for surgery in carotid artery stenosis (author's transl)]

Reconstruction of carotid arteries should preferably be a prophylactic measure and only in exceptional cases a therapeutic procedure. The best results are seen in stage I (asymptomatic) or in stage II (transient ischemic attacks). Surgical intervention in acute cerebral vascular insufficiency is indicated only with a conscious patient with a negative brain scan and without progressing symptoms (stage III a). In stage IIIb (progressive stroke) and stage IVa (acute completed stroke) operative treatment is contraindicated because of a high mortality rate. In accidents with persisting neurologic symptoms (completed stroke more than 2 weeks old) necessary reconstruction of the contralateral vessel is indicated.

[Diagnosis and first dressings of vascular injuries in emergency calls (author's transl)]

With vascular injuries, both the first measures at the site of the accident and also rapid transport (helicopter) to a central specialized hospital with possibilities for vascular surgical care are of decisive importance for the maintenance of life and limb of the patient. From our experience in 169 patients with vascular injuries which were treated between 1967 and 1975, observation of the diagnostic and therapeutic measures described is of the greatest importance for the prognosis of vascular trauma.

[The fatal ski accident]

This investigation analyzes 18 fatal skiing accidents which happened from 1959 to 1975. Deadly accidents caused by avalanches were not taken into consideration. The results of the authors were compared with reports of altogether sixty similar injuries due to skiing accidents. 46% of the fatal accidents were caused by crashing against hindrances. Half of the accidents happened during high-speed-skiing or downhill-competition. More than two-thirds of the wounded skiers died of head injuries. Therefore it is highly recommended to wear a suitable headprotection while skiing downhill.

[Vascular injuries during skiing]

Traumatic lesions of blood vessels occur only rarely in skiing, they are, however, mostly very dramatic events which may lead to the loss of an extremity. Relatively simple measures of diagnosis and therapy may save the skier's threatened life and extremity. Some of these are: Realization that a vascular trauma has occurred, tight pressure bandage, bringing the patient into shock-position, immediate transport by helicopter to a medical center with surgeons trained in vascular surgery.