RESUMEN
Seven solid mono-, bi- and tri-metallic oxide matrices where Fe(2+,3+) ions are distributed in different chemical/spatial environments were synthesized and characterized by XRD, N2-adsorption and EDAX methods. After basification with potassium, all matrices were activated by carburization or reduction-carburization under conditions selected based on the TPC/TPR spectra, tailoring the carburization extent of iron. The performances of the activated Fe-based catalysts with respect to CO2 conversion and C5+ selectivity were measured in a fixed-bed reactor under standard conditions in transient and continuous operation modes in units containing one or three reactors in series with water separations between the reactors. The catalysts were characterized by XRD, N2-adsorption, HRTEM-EELS and XPS before and after steady-state operation in the reactors. It was found that the rate of CO2 conversion is not limited by thermodynamic equilibrium but is strongly restricted by water inhibition and it depends on the nature of the Fe-oxide precursor. The ratio between the FTS and RWGS rates, which determines the C5+ hydrocarbons productivity, is strongly affected by the nature of the Fe-oxide matrix. The catalysts derived from the Fe-Al-O spinel and Fe-Ba-hexaaluminate precursors displayed the best balance of the two functions RFTS/RRWGS = 0.77-0.78. They were followed by magnetite, CuFe-delafossite, K-ferrite, Fe-La-hexaaluminate and LaFe-perovskite with a gradual lowering of RFTS/RRWGS from 0.60 to 0.15 and a gradual decrease in the C5+ productivity. The active sites that enhance the RWGS reaction are located on the surface of the Fe-oxide phases, while the FTS and methanation reactions occur on the surface of the Fe-carbide phases.
RESUMEN
The catalytic wet air oxidation of aqueous solution containing 1000 ppm aniline was conducted in a trickle-bed reactor packed with a novel nanocasted Mn-Ce-oxide catalyst (surface area of 300 m2/g) prepared using SBA-15 silica as a hard template. A range of liquid hourly space velocities (5-20 h(-1)) and temperatures (110-140 degrees C) at 10 bar of oxygen were tested. The experiments were conducted to provide the intrinsic performance of the catalysts. Complete aniline conversion, 90% TOC conversion, and 80% nitrogen mineralization were achieved at 140 degrees C and 5 h(-1). Blank experiments yielded relatively low homogeneous aniline (<35%) and negligible TOC conversions. Fast deactivation of the catalysts was experienced due to leaching caused by complexation with aniline. Acidification of the solution with HCI (molar HCI to aniline ratio of 1.2) was necessary to avoid colloidization and leaching of the nanoparticulate catalyst components. The catalyst displayed stable performance for over 200 h on stream.
Asunto(s)
Aire , Compuestos de Anilina/química , Cesio/química , Manganeso/química , Nanoestructuras , Ácidos/química , Catálisis , Estructura Molecular , Nitrógeno/química , Oxidación-Reducción , Dióxido de Silicio/química , Agua/químicaRESUMEN
The chromia-based catalysts have been reported to combine the high activity and resistance to deactivation in oxidative removal of chlorinated VOC. However, their activity is limited by the low amount of chromia that can be deposited on supports maintaining the optimal state of surface species and high surface area. The pure nanostructured chromia was used as a catalytically active support for noble metals and transition-metal oxide oxidation catalysts. High efficiency of Pt-promoted CrOOH aerogel with surface area of 500 m2*g(-1) was demonstrated in full combustion of 1,2-dichloroethane (DCE) and chlorobenzene (CB). At gas hour space velocity (GHSV) of 46 000 h(-1), the total conversion to CO2/H2O/HCl was achieved at 330 degrees C (DCE) and 380 degrees C (CB). The combustion rate constants measured at standard conditions with 0.5% Pt/CrOOH catalyst were 1 or 2 orders of magnitude higher than measured with 15%Cr2O3/Al2O3 or 0.5%Pt/Al2O3, respectively. The effects of Pt, Au, Mn, and Ce additives on the performance of CrOOH aerogel in combustion of chlorinated VOC were analyzed related to the materials structure.
Asunto(s)
Cromo/química , Hidrocarburos Clorados/química , Incineración , Compuestos Orgánicos/química , Platino (Metal)/química , Óxido de Aluminio/química , Catálisis , Cerio/química , Clorobencenos/química , Compuestos de Cromo/química , Dicloruros de Etileno/química , Geles , Oro/química , Manganeso/química , Nanoestructuras , Oxidación-Reducción , Óxidos/química , Temperatura , Volatilización , Eliminación de Residuos Líquidos/métodosRESUMEN
The ionic liquid [bmim][PF6] was found to provide extra stability to the air-sensitive chiral catalyst Rh-MeDuPHOS in asymmetric hydrogenation of enamides.
RESUMEN
Ultrasound radiation can be used to synthesize a variety of mesporous materials. The reaction time is considerably shorter than the conventional methods. Ultrasonic waves can be further used for the insertion of amorphous nanosized catalysts into the mesopores. A detailed study demonstrates that the nanoparticles are deposited as a monolayer on the inner mesopores walls without blocking them. When the ultrasonically prepared catalyst/mesoporous-subtrate composite is used in catalysis a high conversion into product is obtained.
Asunto(s)
Angioplastia de Balón , Infarto/terapia , Riñón/irrigación sanguínea , Obstrucción de la Arteria Renal/terapia , Tromboembolia/terapia , Terapia Trombolítica , Adulto , Angiografía , Fibrinolíticos/uso terapéutico , Humanos , Infarto/etiología , Masculino , Obstrucción de la Arteria Renal/complicaciones , Tromboembolia/etiología , Tomografía Computarizada por Rayos XRESUMEN
The dispersion relation for a granular bed with a small amount of fine bubbles is formulated and analyzed. It is assumed that the grain size is much larger than the bubble's radius and that their volume concentration is small. The study is motivated by the problem of acoustic diagnostics of fixed bed chemical reactors operating in multiphase flow regime.
RESUMEN
PURPOSE: To compare the efficacy of radiologic guided placement of percutaneous gastrojejunostomy (PGJ) and percutaneous endoscopic gastrostomy (PEG). MATERIALS AND METHODS: Patients were randomized to PGJ (n = 66) or PEG (n = 69). Indications for gastrostomy were need for prolonged enteral nutrition (97%) or gastrointestinal decompression (3%), with etiologies of neurologic impairment (81%), head and neck neoplasm (12%), bowel obstruction (3%), or other (4%). Mean follow-up was 202 days and 30-day follow-up was obtained for 85% of patients. RESULTS: PEG was successful in 63 of 69 (91%) patients, while PGJ established access in all of 66 attempts (100%) (P = .014). Average procedural time was 53 minutes for PGJ and 24 minutes for PEG (P = .001). At 30-day follow-up, there were 33 and 45 complications in the PGJ and PEG groups, respectively. This difference was due to the greater incidence of pneumonia in the PEG group (P = .013). Long-term tube-related complications occurred with 17 PGJs and four PEGs (P = .007). The PGJ cost more than PEG, but this advantage was offset by the cost of complications. CONCLUSION: PGJ had higher success rate and fewer complications, due to a lower incidence of pneumonia. PEG took less time to perform, cost less, and required less tube maintenance.
Asunto(s)
Nutrición Enteral/métodos , Gastroscopía , Gastrostomía , Yeyunostomía , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Costos y Análisis de Costo , Nutrición Enteral/efectos adversos , Nutrición Enteral/economía , Femenino , Estudios de Seguimiento , Gastroscopía/efectos adversos , Gastroscopía/economía , Gastroscopía/métodos , Gastrostomía/efectos adversos , Gastrostomía/economía , Gastrostomía/métodos , Humanos , Incidencia , Intubación Gastrointestinal/efectos adversos , Intubación Gastrointestinal/economía , Intubación Gastrointestinal/métodos , Yeyunostomía/efectos adversos , Yeyunostomía/economía , Yeyunostomía/métodos , Masculino , Persona de Mediana Edad , Neumonía/etiología , Estudios Prospectivos , Radiografía Intervencional , Factores de Tiempo , Resultado del TratamientoRESUMEN
PURPOSE: To evaluate percutaneous transluminal angioplasty (PTA) alone versus PTA and flexible self-expanding stent placement for the management of hemodialysis access graft stenoses. MATERIALS AND METHODS: Thirty-seven grafts in 34 patients were evaluated for abnormal intradialytic parameters (n = 27) or occlusion (n = 10). Angiography identified stenoses (mean, 69%; range, 50%-95%) at or within 3 cm of the vein-graft junction (70%) or in the peripheral outflow vein (30%) that had recurred within a 6-month period after previous PTA. They were randomized to PTA alone (n = 20) or PTA with Wallstent (n = 17). Additional lesions were treated by PTA alone, and a mean of 1.4 (range, 1-3) lesions were treated per patient. Significant differences existed in the mean number of previous accesses (1.8 and 0.8 in the PTA and stent groups, respectively) and in the mean number of previous interventions in the current access (1.8 and 2.9, respectively). End points were subsequent radiologic or surgical intervention, transplantation, and death. RESULTS: Technical success was 100% (mean residual stenosis, 12%; range, 0%-30%). The primary patency of 128 days and secondary patency of 431 days were similar for both groups. Secondary patency required a mean of 1.8 and 1.6 additional interventions for the PTA and stent groups, respectively. The adjunctive stent placement increased the cost of the procedure by 90%. CONCLUSION: Despite significant added costs, there was no advantage to stent placement for recurrent peripheral hemodialysis graft stenoses that were already adequately dilated with balloon angioplasty.
Asunto(s)
Angioplastia de Balón/métodos , Derivación Arteriovenosa Quirúrgica/efectos adversos , Enfermedades Renales/terapia , Diálisis Renal/instrumentación , Stents , Grado de Desobstrucción Vascular , Adulto , Anciano , Anciano de 80 o más Años , Catéteres de Permanencia , Distribución de Chi-Cuadrado , Constricción Patológica/terapia , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Distribución Aleatoria , Resultado del Tratamiento , Venas/patologíaRESUMEN
PURPOSE: To evaluate the natural history of untreated arterial injuries identified at arteriography. MATERIALS AND METHODS: The medical charts and radiographs were reviewed for all patients with arterial injuries identified during arteriography who were managed by means of nonoperative observation and underwent follow-up arteriography. RESULTS: Eighty-six nonrandomized patients with 105 arterial injuries were identified. These included 33 narrowed segments, two dilated segments, 23 intimal defects, 13 occlusions, 12 false aneurysms, 13 arteriovenous fistulas (AVFs), and five extravasations. Four vessels initially considered normal were subsequently found to have injuries. The average duration of observation was 23.5 days (range, 1-1,900 days). Forty-two arterial abnormalities healed spontaneously without other intervention. Thirty-eight "minimal" injuries improved or healed, whereas 25 worsened. Thirteen transmural injuries improved, whereas 12 progressed. There was no significant morbidity or mortality due to the delay involved with sequential studies. CONCLUSIONS: The natural history of these abnormalities was variable and unpredictable. Nonocclusive "minimal" injuries rarely cause ischemic or hemorrhagic complications. Although symptomatic AVFs have a low probability of spontaneous resolution, asymptomatic lesions may close and the risks associated with a few months of observation are minimal. Close follow-up is essential if a nonoperative approach is undertaken.
Asunto(s)
Angiografía , Arterias/lesiones , Enfermedades Vasculares Periféricas/diagnóstico por imagen , Adolescente , Adulto , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Morbilidad , Enfermedades Vasculares Periféricas/epidemiología , Enfermedades Vasculares Periféricas/etiología , Estudios Prospectivos , Tasa de SupervivenciaRESUMEN
OBJECTIVES: The aims of this study were to determine if angiographic findings can be used to predict successful nonoperative therapy of splenic injury and to determine if coil embolization of the proximal splenic artery provides effective hemostasis. METHODS: Splenic injuries detected by diagnostic imaging between 1981 and 1993 at a level I trauma center were prospectively collected and retrospectively reviewed after management by protocol that used diagnostic peritoneal lavage, computed tomography (CT), angiography, transcatheter embolization, and laparotomy. Computed tomography was performed initially or after positive diagnostic peritoneal lavage. Angiography was performed urgently in stabilized patients with CT-diagnosed splenic injuries. Patients without angiographic extravasation were treated by bed rest alone; those with angiographic extravasation underwent coil embolization of the proximal splenic artery followed by bed rest. RESULTS: Patients (172) with blunt splenic injury are the subject of this study. Twenty-two patients were initially managed operatively because of associated injuries or disease (11 patients) or because the surgeon was unwilling to attempt nonoperative therapy (11 patients) and underwent splenectomy (17 patients) or splenorrhaphy (5 patients). One hundred fifty of 172 consecutive patients (87%) with CT-diagnosed splenic injury were stable enough to be considered for nonoperative management. Eighty-seven of the 90 patients managed by bed rest alone, and 56 of 60 patients treated by splenic artery occlusion and bed rest had a successful outcome. Overall splenic salvage was 88%. It was 97% among those managed nonoperatively, including 61 grade III and grade IV splenic injuries. Sixty percent of patients received no blood transfusions. Three of 150 patients treated nonoperatively underwent delayed splenectomy for infarction (one patient) or splenic infection (two patients). CONCLUSIONS: (1) Hemodynamically stable patients with splenic injuries of all grades and no other indications for laparotomy can often be managed nonoperatively, especially when the injury is further characterized by arteriography. (2) The absence of contrast extravasation on splenic arteriography seems to be a reliable predictor of successful nonoperative management. We suggest its use to triage CT-diagnosed splenic injuries to bed rest or intervention. (3) Coil embolization of the proximal splenic artery is an effective method of hemostasis in stabilized patients with splenic injury. It expands the number of patients who can be managed nonoperatively.
Asunto(s)
Bazo/lesiones , Heridas no Penetrantes/terapia , Adolescente , Adulto , Anciano , Algoritmos , Angiografía , Niño , Preescolar , Embolización Terapéutica/métodos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Lavado Peritoneal , Estudios Prospectivos , Estudios Retrospectivos , Bazo/irrigación sanguínea , Bazo/diagnóstico por imagen , Arteria Esplénica , Tomografía Computarizada por Rayos X , Triaje , Heridas no Penetrantes/clasificación , Heridas no Penetrantes/cirugíaRESUMEN
PURPOSE: To review the indications for and techniques and results of interventional radiology in the management of internal carotid artery gunshot wounds. PATIENTS AND METHODS: The demographics, clinical presentations, angiographic findings, methods of treatment, and outcomes were reviewed in 20 patients who underwent 21 interventional procedures. RESULTS: Seventeen coil embolizations were successful in controlling hemorrhage. One intimal flap was compressed with balloon angioplasty, with subsequent nonoperative healing. Temporary balloon occlusions were used as a method of preoperative assessment of intracranial collateral circulation or of preoperative vascular control in three patients. There were no complications. The mortality rate was 20%. CONCLUSION: Penetration of the internal carotid artery is a very severe injury with a high mortality rate due to neurologic sequelae. Interventional radiology plays an important role in the management of these wounds, and it often obviates surgical exploration.
Asunto(s)
Traumatismos de las Arterias Carótidas , Radiografía Intervencional , Heridas por Arma de Fuego/terapia , Adolescente , Adulto , Angiografía , Angioplastia de Balón , Arteria Carótida Interna/diagnóstico por imagen , Arteria Carótida Interna/cirugía , Cateterismo , Circulación Colateral , Embolización Terapéutica/instrumentación , Femenino , Hemorragia/terapia , Humanos , Masculino , Persona de Mediana Edad , Cuidados Preoperatorios , Estudios Retrospectivos , Tasa de Supervivencia , Resultado del Tratamiento , Túnica Íntima/lesiones , Heridas por Arma de Fuego/diagnóstico por imagen , Heridas por Arma de Fuego/cirugíaRESUMEN
In children the use of internal ureteral stents has the added morbidity of requiring general anesthesia for stent retrieval. Magnetically tipped ureteral stents were developed to allow easy retrieval without the need for anesthesia or cystoscopy. For pyeloplasty we generally do not use a stent or nephrostomy tube but we treated 7 children 2 1/2 months to 11 years old in whom we believed there was an indication for stenting and in whom we used a magnetically tipped stent. The catheters were removed with a magnetically tipped catheter retriever without the need for anesthesia in 6 of the 7 cases and cystoscopy was not required in any case. Our initial impression is that when stenting is advised the magnetically tipped ureteral stent appears to be a good alternative, especially in children, since it avoids the need for anesthesia and cystoscopic retrieval.
Asunto(s)
Stents , Uréter , Niño , Preescolar , Femenino , Humanos , Lactante , Pelvis Renal/cirugía , Masculino , Cateterismo UrinarioRESUMEN
We report five pediatric cases that illustrate the methodologic pitfalls and limitations of diuretic renography in suspected ureteropelvic junction obstruction. False-positive studies may be related to such avoidable flaws in methodology as premature diuretic administration, inadequate diuretic dose, and bladder distension, or to recent pyeloplasty. False-negative results may occur despite optimum technique, necessitating a follow-up study for confirmation.
Asunto(s)
Diuréticos , Renografía por Radioisótopo , Preescolar , Diuréticos/administración & dosificación , Reacciones Falso Negativas , Reacciones Falso Positivas , Femenino , Humanos , Lactante , Masculino , Valor Predictivo de las Pruebas , Obstrucción Ureteral/diagnóstico por imagenRESUMEN
Large visceral aneurysms in polyarteritis nodosa are relatively uncommon. We present a patient with polyarteritis nodosa who ruptured a large intrahepatic aneurysm which was treated by percutaneous transhepatic coil embolization.
Asunto(s)
Aneurisma Roto/terapia , Embolización Terapéutica , Arteria Hepática , Poliarteritis Nudosa/complicaciones , Adulto , Aneurisma Roto/diagnóstico por imagen , Aneurisma Roto/etiología , Angiografía , Arteria Hepática/diagnóstico por imagen , Humanos , Masculino , Tomografía Computarizada por Rayos XRESUMEN
We present the case of a patient who sustained a gunshot wound in very close proximity to the left external carotid artery. The bullet was located exactly over the typical location of the internal carotid artery. Total agenesis of the internal carotid artery, a rare anomaly, was differentiated from thrombosis of the internal carotid artery.
Asunto(s)
Arteria Carótida Interna/anomalías , Traumatismos del Cuello , Heridas por Arma de Fuego , Adulto , Trombosis de las Arterias Carótidas/diagnóstico por imagen , Diagnóstico Diferencial , Humanos , Masculino , Cuello/diagnóstico por imagen , Tomografía Computarizada por Rayos X , Heridas por Arma de Fuego/diagnóstico por imagenRESUMEN
Acute dissection of the abdominal aorta or common iliac arteries after blunt trauma is a very rare injury. We present an unusual case of acute traumatic dissection of the common iliac arteries. To our knowledge, this is the first reported case of acute traumatic dissection of the iliac arteries with ultimate spontaneous healing.