Superintegrable Hamiltonian systems with noncompact invariant submanifolds. Kepler system

The Mishchenko-Fomenko theorem on superintegrable Hamiltonian systems is generalized to superintegrable Hamiltonian systems with noncompact invariant submanifolds. It is formulated in the case of globally superintegrable Hamiltonian systems which admit global generalized action-angle coordinates. The well known Kepler system falls into two different globally superintegrable systems with compact and noncompact invariant submanifolds.Comment: 23 page

Geometrical aspects of integrable systems

We review some basic theorems on integrability of Hamiltonian systems, namely the Liouville-Arnold theorem on complete integrability, the Nekhoroshev theorem on partial integrability and the Mishchenko-Fomenko theorem on noncommutative integrability, and for each of them we give a version suitable for the noncompact case. We give a possible global version of the previous local results, under certain topological hypotheses on the base space. It turns out that locally affine structures arise naturally in this setting.Comment: It will appear on International Journal of Geometric Methods in Modern Physics vol.5 n.3 (May 2008) issu

Flux creep in Bi2Sr2CaCu2O8(sub +x) single crystals

The results of a magnetic study on a Bi2Sr2CaCu2O(8+x) single crystal are reported. Low field susceptibility (dc and ac), magnetization cycles and time dependent measurements were performed. With increasing the temperature the irreversible regime of the magnetization cycles is rapidly restricted to low fields, showing that the critical current J(sub c) becomes strongly field dependent well below T(sub c). At 2.4 K the critical current in zero field, determined from the remanent magnetization by using the Bean formula for the critical state, is J(sub c) = 2 10(exp 5) A/sq cm. The temperature dependence of J(sub c) is satisfactorily described by the phenomenological law J(sub c) = J(sub c) (0) (1 - T/T(sub c) (sup n), with n = 8. The time decay of the zero field cooled magnetization and of the remanent magnetization was studied at different temperatures for different magnetic fields. The time decay was found to be logarithmic in both cases, at least at low temperatures. At T = 4.2 K for a field of 10 kOe applied parallel to the c axis, the average pinning energy, determined by using the flux creep model, is U(sub o) = 0.010 eV

Natural compounds as therapeutic agents: The case of human topoisomerase ib

Natural products are widely used as source for drugs development. An interesting example is represented by natural drugs developed against human topoisomerase IB, a ubiquitous enzyme involved in many cellular processes where several topological problems occur due the formation of supercoiled DNA. Human topoisomerase IB, involved in the solution of such problems relaxing the DNA cleaving and religating a single DNA strand, represents an important target in anticancer therapy. Several natural compounds inhibiting or poisoning this enzyme are under investigation as possible new drugs. This review summarizes the natural products that target human topoisomerase IB that may be used as the lead compounds to develop new anticancer drugs. Moreover, the natural compounds and their derivatives that are in clinical trial are also commented on

Early Carotid Endarterectomy after Ischemic Stroke: The Results of a Prospective Multicenter Italian Study

ObjectivesTo evaluate safety of early carotid endarterectomy (CEA) in patients with acute brain ischemia presenting to the emergency department stroke units (EDSU).MethodsThe neurologists, neuroradiologists and vascular surgeons on duty in emergency departments enrolled 96 patients who underwent very early CEA according to a predefined protocol within two years. The protocol included evaluation of neurological status by National Institute of Health Stroke Scale (NIHSS), neuroimaging assessment, ultrasound of the carotid arteries and Transcranial Doppler. Patients with NIHSS>22 or whose neuroimaging showed brain infarct >2/3 of the middle cerebral artery territory were excluded. All eligible patients underwent CEA as soon as possible. Primary end points of the study were mortality, neurological morbidity by NIHSS and postoperative hemorrhagic conversion on neuroimaging. Statistical analysis was performed by univariate analysis.ResultsThe mean time elapsing between the onset of stroke and endarterectomy was 1.5 days (±2 days). The overall 30-day morbidity mortality rate was 7.3% (7/96). No neurological mortality occurred. On hospital discharge, three patients (3%) experienced worsening of the neurological deficit (NIHSS score 1 to 2, 1 to 3 and 9 to 10 respectively). Postoperative CT demonstrated there were no new cerebral infarcts nor hemorrhagic transformation. At hospital discharge 9/96 patients (9%) had no improvement in NHISS scores, 37 were asymptomatic and 45 showed a median decrease of 4.5 NIHSS points (range 1–18). By univariate analysis none of the considered variables influenced the clinical outcome.ConclusionOur protocol selected patients who can safely undergo very early (<1.5 days) surgery after acute brain ischemia. Large randomized multicenter prospective trials are warranted to compare very early CEA versus best medical therapy

Popliteal artery entrapment associated with cannabis arteritis.

OBJECTIVE: To report popliteal artery entrapment in a patient with distal necrosis and cannabis-related arteritis, two rare or exceptional disorders never described in association. To conduct a targeted review and especially to seek information on the clinical presentation with characteristics specific to each disorder so as to hasten the diagnosis and choose appropriate management. MATERIAL AND METHODS: A 19-year-old man who presented with plantar claudication associated with necrosis in a toe underwent diagnostic arteriography and surgery for popliteal artery entrapment type III. RESULTS: Surgical clearance resolved the popliteal artery entrapment but left the clinical symptoms unchanged. Closer questioning disclosed a history of cannabis consumption and intravenous vasodilatory therapy was started. After the 21-day course of vasodilator agents the pain disappeared and the toe necrosis regressed. The patient stopped taking cannabis and had no signs of recurrence. CONCLUSION: Whereas a popliteal artery entrapment, albeit a rare event, is well described and responds to standardized treatment, popliteal artery entrapment associated with cannabis-induced arteritis is an exceptional event that could confuse management. Because young people-the age group mainly at risk for popliteal artery entrapment-increasingly use cannabis, cannabis arteritis could become a more frequent event associated with other arterial disorders that may confuse the diagnosis and complicate management. Our experience in a young patient suggests that coexisting popliteal artery entrapment and distal necrosis in a young patient should raise a strong suspicion of an associated vascular disorder possibly related to cannabis consumption. Intravenous vasodilatation treatment is successful provided that cannabis use is discontinued

Global action-angle coordinates for completely integrable systems with noncompact invariant submanifolds

The obstruction to the existence of global action-angle coordinates of Abelian and noncommutative (non-Abelian) completely integrable systems with compact invariant submanifolds has been studied. We extend this analysis to the case of noncompact invariant submanifolds.Comment: 13 pages, to be published in J. Math. Phys. (2007

Topoisomerase IB: a relaxing enzyme for stressed DNA

DNA topoisomerase I enzymes relieve the torsional strain in DNA; they are essential for fundamental molecular processes such as DNA replication, transcription, recombination, and chromosome condensation; and act by cleaving and then religating DNA strands. Over the past few decades, scientists have focused on the DNA topoisomerases biological functions and established a unique role of Type I DNA topoisomerases in regulating gene expression and DNA chromosome condensation. Moreover, the human enzyme is being investigated as a target for cancer chemotherapy. The active site tyrosine is responsible for initiating two transesterification reactions to cleave and then religate the DNA backbone, allowing the release of superhelical tension. The different steps of the catalytic mechanism are affected by various inhibitors; some of them prevent the interaction between the enzyme and the DNA while others act as poisons, leading to TopI-D NA lesions, breakage of DNA, and eventually cellular death. In this review, our goal is to provide an overview of mechanism of human topoisomerase IB action together with the different types of inhibitors and their effect on the enzyme functionality

Aneurysm of the pancreaticoduodenal arteries with a celiac trunk lesion: Current management

OBJECTIVE: We report a ruptured aneurysm of the pancreaticoduodenal arteries without acute or chronic pancreatitis but associated with a median arcuate ligament division that compressed the celiac trunk, an exceptional event, thus far described in only 11 patients. We also conducted a targeted review to seek information about clinical presentation, to hasten diagnosis and assist in therapeutic management. METHODS: A 54-year-old man with retroperitoneal hemorrhage associated with an arcuate ligament division, documented on computed tomographic scans, underwent diagnostic arteriography and embolization to treat the bleeding aneurysm. In a second elective operation the causative arcuate ligament was sectioned to decompress the celiac artery, to prevent aneurysm recurrence. RESULTS: Embolization stopped the aneurysmal bleeding, and arteriograms showed that surgical sectioning resolved the celiac trunk stenosis. At 1-year follow-up the patient had no signs of complications or recurrence of disease. CONCLUSION: Ruptured aneurysm of the pancreaticoduodenal arteries associated with stenosis of the celiac trunk is a surgical emergency. Although a literature review disclosed no significant difference between outcomes after open surgery and radiologic arterial embolization, our experience in this case suggests immediate embolization during arteriography as the most effective treatment. Later, to prevent recurrence, the arcuate ligament should be surgically sectioned and the celiac artery stenosis treated

Aneurysm of the Pancreaticoduodenal Arteries Associated with a Cœliac Artery Lesion

IntroductionA ruptured aneurysm of the pancreaticoduodenalarteries without acute or chronic pancreatitis butassociated with a median arcuate ligament divisionis an exceptional event described in only 11 cases. Thecase of a ruptured pancreaticoduodenal artery aneur-ysm, associated with a cœliac artery lesion which wedescribe, illustrates the difficulty in diagnosing theserare events promptly and in instituting urgent treat-ment to arrest the bleeding followed by an electiveprocedure to prevent recurrence.Case ReportA 54-year-old man with no history of vascular diseasewas admitted to a district hospital for investigation ofvague abdominal pain mainly affecting the rightabdomen, hypotension corrected by infusion ofcrystalloid and no fever. Laboratory blood chemicalfindings including a normal hemoglobin, raisedleukocyte count and high C-reactive protein concen-tration. This presentation raised the suspicion of a gallbladder infection and the patient was kept under closeobservation overnight. The next day, hypotensiondeveloped and the patient complained of pain in theright iliac quadrant. An abdominal ultrasound scanshowed a large iliac fluid collection, but no lesionsinvolving the gall bladder or liver. Appendicitis wasdiagnosed and the patient underwent a McBurneyoperation. During surgery blood was found in theabdomen. An exploratory laparotomy revealed a largeretroperitoneal hematoma. The patient was trans-ferred to our vascular surgery unit. A CT scan aftercontrast injection revealed an intact retroperitonealhematoma (16 £ 9 £ 15 cm), with no bleeding from theaorta or the visceral arteries, and a median arcuateligament division that compressed the origin of thecœliac trunk. Because these findings suggested aruptured pancreaticoduodenal artery aneurysm arter-iography was planned to confirm the diagnosis andtreat the aneurysm by embolization. The patient, whowas by now haemodynamically stable, was kept underobservation in the ITU and transferred to the vascularsurgical unit. On day 1, a CT scan showed that thehematoma had enlarged. The patient was kept undersurveillance in the vascular unit and arteriographywas planned for the following day. During the night,the patient collapsed but responded to more IVcrystalloid and was immediately transferred to theradiological unit. While the patient was being pre-pared for arteriography, a new CT scan showed thehematoma had now increased in size and had spreadto the intraperitoneal space, filling the peri-hepaticand peri-splenic areas as well as the pelvis.The patient underwent selective arteriography tovisualize the stenosis caused by compression of thecœliac axis, to localize the bleeding pancreaticoduo-denal artery aneurysm and to proceed to treatment byembolization. Under local anesthesia, a 5-F introduce