Graphene catalyzes the reversible formation of a C-C bond between two molecules.

Carbon deposits are well-known inhibitors of transition metal catalysts. In contrast to this undesirable behavior, here we show that epitaxial graphene grown on Ru(0001) promotes the reversible formation of a C-C bond between -CH2CN and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ). The catalytic role of graphene is multifaceted: First, it allows for an efficient charge transfer between the surface and the reactants, thus favoring changes in carbon hybridization; second, it holds the reactants in place and makes them reactive. The reaction is fully reversible by injecting electrons with an STM tip on the empty molecular orbitals of the product. The making and breaking of the C-C bond is accompanied by the switching off and on of a Kondo resonance, so that the system can be viewed as a reversible magnetic switch controlled by a chemical reaction.

Acute typhlitis in inmunocompromised patient: an eight year experience.

INTRODUCTION: Acute typhlitis is usually associated with severe immunosuppressive conditions. Initially described as closely associated with infantile myeloid leukaemia, its incidence increased along the last decade. DESIGN: retrospective review. PATIENTS: 12 immunodepressed patients affected of acute typhilis in our hospital between 1994 and 2001. Suspected diagnosis was established by clinical symptoms and abdominal CT findings, and was confirmed with pathological finding in the surgical specimen. Clinical and radiological diagnosis, treatment, complications and survival of patients are discussed. RESULTS: 3 patients with a previous diagnosis af acute myeloid leukemia, 2 patients with non-Hodgkin lymphoma, 2 patients with aplastic anaemia, one patient with AIDS, and 4 patients with kidney transplantation were included in our study. Prednisone, cyclosporine, Ara-C and vincristine were the most frequently involved drugs. Most frequent clinical findings included abdominal pain, fever, nausea-vomiting and abdominal distension. CT diagnosis revealed caecum and colic involvement with rarefaction of pericaecal fat. Medical treatment was successful in only 33% of all patients, the other patients requiring a surgical procedure including right hemicolectomy with or without intestinal anastomosis. Mortality reached 58.3 per cent, representing multiorganic sepsis the main cause of death. CONCLUSIONS: although early diagnosis of acute typhlitis bears a better prognosis, mortality rates are up 50 % in spite of an established treatment.

Transumbilical single port surgery with conventional laparoscopic instruments in horseshoe kidney.

INTRODUCTION: Laparoscopic surgery is following a natural course as it decreases surgical aggression on the abdominal wall without undermining the curative and functional results. Although it is still being developed, single port surgery has meant an advance in this sense. MATERIAL AND METHODS: We present the first single port laparoscopic pyelolithectomy surgery in horseshoe kidney, using conventional rigid instruments. The case of an 18-year old patient with BMI of 19 in whom the imaging tests (urogram and computed tomography) showed a horseshoe kidney with left coralliform lithiasis and discrete calyceal ectasia is presented. The lithiasis was extracted using umbilical access with single port device and conventional rigid instruments. RESULTS: The surgery was performed without complications. Surgery time was 110 minutes and bleeding 50 cc. On incision of the urinary system, there was purulent urine extravasation that conditioned fever of 38 °C in the post-operatory period. During the intervention, a double J stent was placed via percutaneous approach. The patient was discharged on the third day of hospitalization. CONCLUSION: Single port laparoscopic access for pyelolithectomy surgery in horseshoe kidney is a reasonable alterative. The use of conventional rigid instruments facilitates the performance of this surgery with good triangulation, without conflict regarding hands and safety for the patient.