Extending the viability of human precision-cut intestinal slice model for drug metabolism studies.

Human Precision-cut intestinal slices (hPCIS) are used to study intestinal physiology, pathophysiology, drug efficacy, toxicology, kinetics, and metabolism. However, the use of this ex vivo model is restricted to approximately a 24 h timeframe because of declining viability of the hPCIS during traditional culture. We hypothesized that we could extend the hPCIS viability by using organoid medium. Therefore, we cultured hPCIS for up to 72 h in organoid media [expansion medium (Emed) and differentiation medium (Dmed)]. After incubation, we assessed culture-induced changes on viability markers, specific cell type markers and we assessed the metabolic activity of enterocytes by measuring midazolam metabolite formation. We show that the adenosine triphosphate (ATP)/protein ratio of Emed-cultured hPCIS and morphology of both Emed- and Dmed-cultured hPCIS was improved compared to WME-cultured hPCIS. Emed-cultured hPCIS showed an increased expression of proliferation and stem cell markers, whereas Dmed-cultured hPCIS showed an increased expression of proliferation and enterocyte markers, along with increased midazolam metabolism. Using the Emed, the viability of hPCIS could be extended for up to 72 h, and proliferating stem cells remained preserved. Using Dmed, hPCS also remained viable for up to 72 h, and specifically rescued the metabolizing enterocytes during culture. In conclusion, by using two different organoid culture media, we could extend the hPCIS viability for up to 72 h of incubation and specifically steer stem cells or enterocytes towards their original function, metabolism, and proliferation, potentially allowing pharmacokinetic and toxicology studies beyond the 24 h timeframe.

Clinical relevant pancreatic fistula after pancreatoduodenectomy: when negative amylase levels tell the truth.

Drain Amylase level are routinely determined to diagnose pancreatic fistula after Pancreatocoduodenectomy. Consensus is lacking regarding the cut-off value of amylase to diagnosis clinically relevant postoperative pancreatic fistulae (POPF). The present study proposes a model based on Amylase Value in the Drain (AVD) measured in the first three postoperative days to predict a POPF. Amylase cut-offs were selected from a previous published systematic review and the accuracy were validated in a multicentre database from 12 centres in 2 countries. The present study defined POPF the 2016 ISGPS criteria (3 times the upper limit of normal serum amylase). A learning machine method was used to correlate AVD with the diagnosis of POPF. Overall, 454 (27%) of 1638 patients developed POPF. Machine learning excluded a clinically relevant postoperative pancreatic fistulae with an AUC of 0.962 (95% CI 0.940-0.984) in the first five postoperative days. An AVD at a cut-off of 270 U/L in 2 days in the first three postoperative days excluded a POPF with an AUC of 0.869 (CI 0.81-0.90, p < 0.0001). A single AVD in the first three postoperative days may not exclude POPF after pancreatoduodenectomy. The levels should be monitored until day 3 and have two negative values before removing the drain. In the group with a positive level, the drain should be kept in and AVD monitored until postoperative day five.

Influence of Promotion on the Growth of Anchored Colloidal Iron Oxide Nanoparticles during Synthesis Gas Conversion.

Using colloidal iron oxide nanoparticles with organic ligands, anchored in a separate step from the supports, has been shown to be beneficial to obtain homogeneously distributed metal particles with a narrow size distribution. Literature indicates that promoting these particles with sodium and sulfur creates an active Fischer-Tropsch catalyst to produce olefins, while further adding an H-ZSM-5 zeolite is an effective way to obtain aromatics. This research focused on the promotion of iron oxide colloids with sodium and sulfur using an inorganic ligand exchange followed by the attachment to H-ZSM-5 zeolite crystals. The catalyst referred to as FeP/Z, which consists of iron particles with inorganic ligands attached to a H-ZSM-5 catalyst, was compared to an unpromoted Fe/Z catalyst and an Fe/Z-P catalyst, containing the colloidal nanoparticles with organic ligands, promoted after attachment. A low CO conversion was observed on both FeP/Z and Fe/Z-P, originating from an overpromotion effect for both catalysts. However, when both promoted catalysts were washed (FeP/Z-W and Fe/Z-P-W) to remove the excess of promoters, the activity was much higher. Fe/Z-P-W simultaneously achieved low selectivity toward methane as part of the promoters were still present after washing, whereas for FeP/Z-W the majority of promoters was removed upon washing, which increased the methane selectivity. Moreover, due to the addition of Na+S promoters, the iron nanoparticles in the FeP/Z(-W) catalysts had grown considerably during catalysis, while those in Fe/Z-P(-W) and Fe/Z(-W) remained relatively stable. Lastly, as a large broadening of particle sizes for the used FeP/Z-W was found, where particle sizes had both increased and decreased, Ostwald ripening is suggested for particle growth accelerated by the presence of the promoters.

The role of abdominal drainage in pancreatic resection - A multicenter validation study for early drain removal.

BACKGROUND: Abdominal drainage and the timing of drain removal in patients undergoing pancreatic resection are under debate. Early drain removal after pancreatic resection has been reported to be safe with a low risk for clinical relevant postoperative pancreatic fistula (CR-POPF) when drain amylase on POD1 is < 5000U/L. The aim of this study was to validate this algorithm in a large national cohort. METHODS: Patients registered in the Dutch Pancreatic Cancer Audit (2014-2016) who underwent pancreatoduodenectomy, distal pancreatectomy or enucleation were analysed. Data on post-operative drain amylase levels, drain removal, postoperative pancreatic fistulae were collected. Univariate and multivariate analysis using a logistic regression model were performed. The primary outcome measure was grade B/C pancreatic fistula (CR-POPF). RESULTS: Among 1402 included patients, 433 patients with a drain fluid amylase level of <5000U/L on POD1, 7% developed a CR-POPF. For patients with an amylase level >5000U/L the CR-POPF rate was 28%. When using a cut-off point of 2000U/L or 1000U/L during POD1-3, the CR-POPF rates were 6% and 5% respectively. For patients with an amylase level of >2000U/L and >1000UL during POD 1-3 the CR-POPF rates were 26% and 22% respectively (n = 223). Drain removal on POD4 or thereafter was associated with more complications (p = 0.004). Drain amylase level was shown to be the most statistically significant predicting factor for CR-POPF (Wald = 49.7; p < 0.001). CONCLUSION: Our data support early drain removal after pancreatic resection. However, a cut-off of 5000U/L drain amylase on POD1 was associated with a relatively high CR-POPF rate of 7%. A cut-off point of 1000U/L during POD1-3 resulted in 5% CR-POPF and might be a safer alternative.

Attachment of iron oxide nanoparticles to carbon nanofibers studied by in-situ liquid phase transmission electron microscopy.

By using liquid phase transmission electron microscopy (LP-TEM), the dynamics of iron oxide nanoparticle (Fe-NP) attachment to carbon nanofibers (CNFs) and oxygen functionalized CNFs (CNF-Ox) were studied in-situ. The beam effect on the stability of the sample in various liquids was examined, and it was found that toluene provided the highest stability and resolution to image both CNF supports and Fe-NPs. Flowing particles dispersed in toluene through the liquid cell allowed direct monitoring of the attachment process at ambient temperature. Using CNF-Ox as a support led to a large extent and irreversible attachment of iron nanoparticle compared to a lower extent and reversible attachment of Fe-NPs to pristine CNF, indicating the influence of surface functionalization on colloidal particle attachment. The results were confirmed by lab-scale experiments as well as experiments performed with the electron beam switched off, verifying the notion that beam effects did not affect the attachment. This study revealed previously unknown phenomena in colloidal particle - support interactions and demonstrates the power of LP-TEM technique for studying such nanoscale processes.

Assembly and activation of supported cobalt nanocrystal catalysts for the Fischer-Tropsch synthesis.

The effect of oxidative treatments on the depostion of cobalt nanocrystals (Co-NC) onto a support and subsequent ligand removal was investigated. Deposition of ε-cobalt NC led to extensive clustering of NC and low Fischer-Tropsch synthesis activity. Low-temperature oxidation of ε-cobalt NC resulted in a very uniform CoO-NC distribution and high activity whereas high-temperature oxidation to Co3O4 led to less uniform NC distributions and lower activity.

Influence of precursor porosity on sodium and sulfur promoted iron/carbon Fischer-Tropsch catalysts derived from metal-organic frameworks.

Iron-based metal-organic frameworks (MOFs) with varying porosity are converted by pyrolysis into iron/carbon catalysts with predetermined composition and tailored pore structural features for the Fischer-Tropsch synthesis of lower C2-C4 olefins. Significantly higher activity arises for catalysts with higher porosity and decreased iron particle size derived from hierarchical MOF xerogel/aerogel precursors as compared to a purely microporous MOF. Post-synthetic functionalization using sodium and sulfur promoters further enhances the catalytic properties.

Short-Course Radiotherapy Followed by Neoadjuvant Bevacizumab, Capecitabine, and Oxaliplatin and Subsequent Radical Treatment in Primary Stage IV Rectal Cancer: Long-Term Results of a Phase II Study.

BACKGROUND: In a Dutch phase II trial conducted between 2006 and 2010, short-course radiotherapy followed by systemic therapy with capecitabine, oxaliplatin, and bevacizumab as neoadjuvant treatment and subsequent radical surgical treatment of primary tumor and metastatic sites was evaluated. In this study, we report the long-term results after a minimum follow-up of 6 years. METHODS: Patients with histologically confirmed rectal adenocarcinoma with potentially resectable or ablatable metastases in liver or lungs were eligible. Follow-up data were collected for all patients enrolled in the trial. Overall and recurrence-free survival were calculated using the Kaplan-Meier method. RESULTS: Follow-up data were available for all 50 patients. After a median follow-up time of 8.1 years (range 6.0-9.8), 16 patients (32.0%) were still alive and 14 (28%) were disease-free. The median overall survival was 3.8 years (range 0.5-9.4). From the 36 patients who received radical treatment, two (5.6%) had a local recurrence and 29 (80.6%) had a distant recurrence. CONCLUSIONS: Long-term survival can be achieved in patients with primary metastatic rectal cancer after neoadjuvant radio- and chemotherapy. Despite a high number of recurrences, 32% of patients were alive after a median follow-up time of 8.1 years.

[Liver transplantation in paediatric patients in the Netherlands; evolution over the past two decades]. / Levertransplantaties bij kinderen in Nederland.

OBJECTIVE: To evaluate the results of the national paediatric liver transplantation programme in the University Medical Centre (UMC) Groningen in the Netherlands during the past two decades. DESIGN: Retrospective cohort study. METHOD: We analysed data from paediatric patients who underwent liver transplantation at UMC Groningen in the period 1995-2016. We compared outcomes from children who had undergone a liver transplantation in the period 1995-2005 (cohort A; n = 126) and in the period 2006-2016 (cohort B; n = 169). We performed a subanalysis in cohort B between liver transplantations with deceased donor livers (n = 132) and living donor liver transplantations (LDLT; n = 37). RESULTS: In cohort A, almost all livers came from deceased donors (99%), whereas in cohort B, 37 LDLTs (22%) were performed. The median age of recipients was significantly higher in cohort A (4.4 vs. 2.5 years; p = 0.015). Postoperative complications were comparable for both cohorts. Re-transplantations within a year after transplantation were more often performed in cohort A than in cohort B (25% vs. 12%; p = 0.004). Following LDLT, there was 2 times (5.4%) an indication for re-transplantation. In cohort B the 5-year survival rate was better than in cohort A (83 vs. 71%; p = 0.014). In cohort B, 5-year survival was higher after LDLT than after transplantation with a deceased donor liver (95 vs. 81%; p = 0.025). CONCLUSION: Outcomes after paediatric liver transplantation in the Netherlands have further improved during the past two decades. With an actuarial 5-year survival of 83% in the most recent cohort, and as high as 95% following LDLT, we can say that the UMC Groningen has a successful national paediatric liver transplant programme.

Outcomes after resection and/or radiofrequency ablation for recurrence after treatment of colorectal liver metastases.

BACKGROUND: Repeat liver resection for colorectal liver metastases (CRLMs) is possible in a limited number of patients, with radiofrequency ablation (RFA) as an alternative for unresectable CRLMs. The aim of this study was to analyse survival rates with these interventions. METHODS: This was a database analysis of patients who underwent first and repeat interventions for synchronous and metachronous CRLMs between 2000 and 2013. Descriptive and survival statistics were calculated. RESULTS: Among 431 patients who underwent resection or RFA for CRLMs, 305 patients developed recurrences for which 160 repeat interventions (resection and/or RFA or ablative radiotherapy) were performed. In total, after 707 first or repeat interventions, 516 recurrences (73·0 per cent) developed, of which 276 were retreated curatively. At the time of first intervention, independent risk factors for death were lymph node-positive primary tumour (hazard ratio (HR) 1·40; P = 0·030), more than one CRLM (HR 1·53; P = 0·007), carcinoembryonic antigen level exceeding 200 ng/ml (HR 1·89; P = 0·020) and size of largest CRLM greater than 5 cm (HR 1·54; P = 0·014). The 5-year overall survival rates for liver resection and percutaneous RFA as first intervention were 51·9 and 53 per cent, with a median overall survival of 65·0 (95 per cent c.i. 47·3 to 82·6) and 62·1 (52·2 to 72·1) months, respectively. CONCLUSION: RFA had good oncological outcomes in patients with unresectable CRLMs. Radiofrequency ablation is progressively more applied with each additional intervention.

Resection of liver metastases in patients with gastrointestinal stromal tumors in the imatinib era: A nationwide retrospective study.

INTRODUCTION: Liver metastases are common in patients with gastrointestinal stromal tumors (GIST). In the absence of randomized controlled clinical trials, the effectiveness of surgery as a treatment modality is unclear. This study identifies safety and outcome in a nationwide study of all patients who underwent resection of liver metastases from GIST. METHODS: Patients were included using the national registry of histo- and cytopathology (PALGA) of the Netherlands from 1999. Kaplan Meier survival analysis was used for calculating survival outcome. Univariate and multivariate regression analyses were carried out for the assessment of potential prognostic factors. RESULTS: A total of 48 patients (29 male, 19 female) with a median age of 58 (range 28-81) years were identified. Preoperative and postoperative tyrosine kinase inhibitor therapy was given to 30 (63%) and 36 (75%) patients, respectively. A minor liver resection was performed in 32 patients, 16 patients underwent major liver resection. Median follow-up was 27 (range 1-146) months. Median progression-free survival (PFS) was 28 (range 1-121) months. One-, three-, and five-year PFS was 93%, 67%, and 59% respectively. Median overall survival (OS) was 90 (range 1-146) months from surgery. The one-, three-, and five-year OS was 93%, 80%, and 76% respectively. R0 resection was the only independent significant prognostic factor for DFS and OS at multivariate analysis. CONCLUSION: Resection of liver metastases in GIST patients combined with imatinib may be associated with prolonged overall survival when a complete resection is achieved.

Hepatocellular carcinoma: Dutch guideline for surveillance, diagnosis and therapy.

UNLABELLED: Hepatocellular carcinoma (HCC) is rare in the Netherlands, even though the incidence has increased quite sharply in recent years. Standard treatment options consist of surgery, orthotopic liver transplantation, radiofrequency ablation, transarterial chemoembolisation (TACE) and systemic therapy with sorafenib. The consensus-based Dutch HCC guideline, established in 2013, serves to guide surveillance, diagnosis and treatment options: Surveillance should be performed by ultrasound at six-month intervals in well-defined cirrhotic patients and in selected high-risk hepatitis B carriers; A nodule > 1 cm in cirrhotic patients with arterial hypervascularity and venous or delayed phase washout at four-phase CT or MRI scan establishes the diagnosis of HCC; In patients with HCC without underlying cirrhosis, resection should be considered regardless of tumour size; In cirrhotic HCC patients, tumour stage, severity of underlying cirrhosis, and performance status determine treatment options. The algorithm of the Barcelona Clinic Liver Cancer (BCLC) staging system should be followed; Patients with Child-Pugh A-B cirrhosis (CP < 8 points) and performance status 0-2 are candidates for any active treatment other than transplantation; In early stage HCC (BCLC stage 0 or A, compensated cirrhosis without portal hypertension) surgical resection, liver transplantation, or radiofrequency ablation should be considered; In intermediate stage HCC (BCLC stage B) TACE and÷ or radiofrequency ablation should be considered; In advanced stage HCC (BCLC stage C) sorafenib should be considered. CONCLUSION: The Dutch HCC guideline offers advice for surveillance, diagnosis and treatment of HCC.

Staging laparoscopy in patients scheduled for pancreaticoduodenectomy minimizes hospitalization in the remaining life time when metastatic carcinoma is found.

OBJECTIVE: To compare the burden of total hospitalization as a ratio of survival of staging laparoscopy versus prophylactic bypass surgery in patients with unresectable periampullary adenocarcinoma. BACKGROUND: Periampullary adenocarcinoma is an aggressive cancer with up to 35% of the patients at surgery found to be unresectable. Palliative prophylactic surgical bypass versus endoscopic stenting has been addressed by randomized controlled trials, but none reported on the burden of hospitalization. METHODS: From a prospective database all patients with periampullary adenocarcinomas with a preoperative patent biliary stent and absent gastric outlet obstruction, but found unresectable during surgery, were analysed. They underwent a staging laparoscopy only versus prophylactic palliative bypass surgery. In-hospital days of the initial admission as well as all consecutive admission days during the remaining life span were compared both in absolute numbers and as relative impact. RESULTS: The inclusion criteria were met by 205 patients. Of these 131 patients underwent a staging laparoscopy detecting metastases in 21 patients. In 184 laparotomies 54 patients underwent prophylactic palliative bypass surgery for unresectable disease. Median total in-hospital-stay in the Laparoscopy Group was 3 days versus 11 days in the Palliative Bypass Group (p = 0.0003). Patients with metastatic disease found during laparoscopy stayed 3.5% of the remaining life time in hospital vs. 10.0% (p = 0.029) in patients with metastatic disease who underwent bypass surgery. CONCLUSIONS: Staging laparoscopy and early discharge in patients with metastatic peri-ampullary carcinoma resulted in reduced hospitalization, both in absolute number of days and as a rate of survival time.

Evaluation of short-course radiotherapy followed by neoadjuvant bevacizumab, capecitabine, and oxaliplatin and subsequent radical surgical treatment in primary stage IV rectal cancer.

BACKGROUND: To evaluate the efficacy and tolerability of preoperative short-course radiotherapy followed by capecitabine and oxaliplatin treatment in combination with bevacizumab and subsequent radical surgical treatment of all tumor sites in patients with stage IV rectal cancer. PATIENTS AND METHODS: Adults with primary metastasized rectal cancer were enrolled. They received radiotherapy (5 × 5 Gy) followed by bevacizumab (7.5 mg/kg, day 1) and oxaliplatin (130 mg/m(2), day 1) intravenously and capecitabine (1000 mg/m(2) twice daily orally, days 1-14) for up to six cycles. Surgery was carried out 6-8 weeks after the last bevacizumab dose. The percentage of radical surgical treatment, 2-year survival and recurrence rates, and treatment-related toxicity was evaluated. RESULTS: Of 50 included patients, 42 (84%) had liver metastases, 5 (10%) lung metastases, and 3 (6%) both liver and lung metastases. Radical surgical treatment was possible in 36 (72%) patients. The 2-year overall survival rate was 80% [95% confidence interval (CI) 66.3%-90.0%]. The 2-year recurrence rate was 64% (95% CI 49.8%-84.5%). Toxic effects were tolerable. No treatment-related deaths occurred. CONCLUSIONS: Radical surgical treatment of all tumor sites carried out after short-course radiotherapy, and bevacizumab-capecitabine-oxaliplatin combination therapy is a feasible and potentially curative approach in primary metastasized rectal cancer.

Risk factors for central bile duct injury complicating partial liver resection.

BACKGROUND: Bile duct injury is a serious complication following liver resection. Few studies have differentiated between leakage from small peripheral bile ducts and central bile duct injury (CBDI), defined as an injury leading to leakage or stenosis of the common bile duct, common hepatic duct, right or left hepatic duct. This study analysed the incidence, risk factors and consequences of CBDI in liver resection. METHODS: Patients undergoing liver resection between 1990 and 2007 were included in this study. Those having resection for bile duct-related pathology or trauma, or after liver transplantation were excluded. Characteristics and outcome variables were collected prospectively and analysed retrospectively. RESULTS: There were 19 instances of CBDI in 462 liver resections (4·1 per cent). One-third of patients with CBDI required surgical reintervention and construction of a hepaticojejunostomy. Resection type (P < 0·001), previous liver resection (P = 0·039) and intraoperative blood loss (P = 0·002) were associated with an increased risk of CBDI. Of all resection types, extended left hemihepatectomy was associated with the highest incidence of CBDI (2 of 9 procedures). CONCLUSION: Patients undergoing extended left hemihepatectomy or repeat hepatectomy were at increased risk of CBDI.

Long-term global quality of life in patients treated for colorectal liver metastases.

BACKGROUND: Surgical treatment of colorectal liver metastases has become increasingly aggressive. The influence of this more active surgical approach on patients' health-related quality of life (HRQoL) has hardly been evaluated. This study investigated the impact of surgical and systemic treatment on HRQoL in patients undergoing hepatic resection for colorectal metastases. METHODS: A total of 145 patients with colorectal liver metastases were entered prospectively into the study. Based on HRQoL values derived from the EuroQol-5D, health summary measures were calculated to express the overall impact on four distinct clinical states. The HRQoL instrument was used at baseline, 3 and 6 weeks after surgery, and every 3 months thereafter for up to 3 years. RESULTS: Patients showed a clear deterioration in HRQoL in the first weeks after surgery, followed by a recovery to baseline levels at 3 months after potentially curative surgery. In contrast, a sustained decline was noted when initial surgery for colorectal liver metastases was considered futile and palliative chemotherapy was started immediately. Three years after initial surgery, there were distinct differences in HRQoL between patients with or without recurrence. The latter group still had HRQoL scores at baseline levels, whereas patients with tumour recurrence showed a significant deterioration in HRQoL. Remarkably, there was no decline in HRQoL in patients with recurrent disease who could be treated by secondary surgical intervention. CONCLUSION: Superior overall HRQoL in the first 3 years after initial successful surgical intervention merits an aggressive surgical approach and intensive follow-up to detect recurrence early.

What is new in liver surgery? Focus on thermoablation and the relevance of the inflammatory response.

Partial liver resection is a well established treatment for patients with liver tumors. It is associated with significant morbidity and some mortality, even in high volume centers. Less invasive modalities are currently available and deserve a place in the armamentarium of liver surgeons. This review discusses the role of thermoablation as a treatment modality for liver tumors. The minimal invasive possibility of percutaneous ablation is a great advantage. The limitation of ablation is the high incidence of ablation site recurrences. The inflammatory response is associated with the initiation of cancer at sites of chronic inflammation. There is also accumulating evidence that progression of tumors is also enhanced by an ongoing inflammatory response. The common denominator probably is angiogenesis. The paper supplies data about the interrelationship between inflammation, angiogenesis and tumor growth. Ablation of liver tumors is associated with a low inflammatory response, especially if it is performed percutaneous and thus deserves to be considered in patients with liver tumors.

A new interventional technique for percutaneous treatment of drainage-resistant liver abscess.

The objective of this case report is to describe a device that can be used as a minimally invasive alternative for the treatment of drainage-resistant liver abscess. The device uses pulse lavage to fragment and evacuate the semi-solid contents of a liver abscess. The treatment of liver abscesses consists of percutaneous drainage, antibiotics and treatment of the underlying cause. This approach can be ineffective if the contents of the abscess cavity are not liquid, and in those cases open surgery is often needed. Here, we describe for the first time a new minimally invasive technique for treating persistent liver abscesses. A patient developed a liver abscess after a hepatico-jejunostomy performed as a palliative treatment for an unresectable pancreatic head carcinoma. Simple drainage by a percutaneously placed pig-tail catheter was insufficient because of inadequate removal of the contents of the abscess cavity. After dilatation of the drain tract the persistent semi-solid necrotic contents were fragmented by a pulsed lavage device, after which the abscess healed uneventfully. The application of pulsed lavage for debridement of drainage-resistant liver abscesses proved to be an effective and minimally invasive alternative to open surgery.

A UV-Vis micro-spectroscopic study to rationalize the influence of Cl(-)(aq) on the formation of different Pd macro-distributions on gamma-Al(2)O(3) catalyst bodies.

The influence of the Cl(-)(aq) concentration, solution pH and equilibration time on the PdCl(4)(2-)(aq) dynamics and molecular structure after impregnation of gamma-Al(2)O(3) catalyst bodies has been studied using UV-Vis micro-spectroscopy. To do so, 0.2 wt% Pd catalysts have been prepared from acidic solutions (pH 1 and 5) of the Na(2)PdCl(4) precursor salt with different amounts of NaCl. It was found that egg-shell catalysts are obtained when a less acidic pH (pH 5) is combined with [Cl(-)(aq)] < 0.6 M and less than 24 h of equilibration time are implemented, while to achieve egg-white catalysts the solution pH should be 1. Moreover, by increasing the equilibration time up to 96 h, the egg-shell profiles vanish to provide a uniform Pd distribution, while the egg-white distribution becomes egg-yolk. Additionally, Pd complexes appeared with different molecular structures depending on the solution pH, equilibration time and macro-distribution achieved. The protocol developed to create different Pd macro-distributions has been applied to prepare two 1 wt% Pd/gamma-Al(2)O(3) egg-shell and egg-white catalysts. The Pd dynamics and molecular structure have been followed after impregnation, drying and calcination, demonstrating that the profiles created after impregnation are retained.

On the origin of the cobalt particle size effects in Fischer-Tropsch catalysis.

The effects of metal particle size in catalysis are of prime scientific and industrial importance and call for a better understanding. In this paper the origin of the cobalt particle size effects in Fischer-Tropsch (FT) catalysis was studied. Steady-State Isotopic Transient Kinetic Analysis (SSITKA) was applied to provide surface residence times and coverages of reaction intermediates as a function of Co particle size (2.6-16 nm). For carbon nanofiber supported cobalt catalysts at 210 degrees C and H(2)/CO = 10 v/v, it appeared that the surface residence times of reversibly bonded CH(x) and OH(x) intermediates increased, whereas that of CO decreased for small (<6 nm) Co particles. A higher coverage of irreversibly bonded CO was found for small Co particles that was ascribed to a larger fraction of low-coordinated surface sites. The coverages and residence times obtained from SSITKA were used to describe the surface-specific activity (TOF) quantitatively and the CH(4) selectivity qualitatively as a function of Co particle size for the FT reaction (220 degrees C, H(2)/CO = 2). The lower TOF of Co particles <6 nm is caused by both blocking of edge/corner sites and a lower intrinsic activity at the small terraces. The higher methane selectivity of small Co particles is mainly brought about by their higher hydrogen coverages.