Phase Transformations in Iron Fischer–Tropsch Catalysts during Temperature-Programmed Reduction

The effect of Cu on the reduction behavior and surface properties of supported and unsupported Fe-based Fischer–Tropsch synthesis (FTS) catalysts was investigated using in situ X-ray photoelectron spectroscopy (XPS) and in situ X-ray absorption spectroscopy (XAS) in combination with ex situ bulk characterization. During exposure to 0.4 mbar CO–H2 above 180 °C, the reduction of CuO to Cu0 marked the onset of the reduction of Fe3O4 to α-Fe. The promotion effects of Cu are explained by a combination of spillover of H2 and/or CO molecules from metallic Cu0 nuclei to closely associated iron oxide species and textural promotion. XAS showed that in the supported catalyst, Cu+ and Fe2+ species were stabilized by SiO2 and, as a result, Fe species were not reduced significantly beyond Fe3O4 and Fe2+, even after treatment at 350 °C. After the reduction treatment, XPS showed that the concentration of oxygen and carbon surface species was higher in the presence of Cu. Furthermore, it was observed that the unsupported, Cu-containing catalyst showed higher CO2 concentration in the product gas stream during and after reduction and Fe surface species were slightly oxidized after prolonged exposure to CO–H2. These observations suggest that, in addition to facilitating the reduction of the iron oxide phase, Cu also plays a direct role in altering the surface chemistry of Fe-based FTS catalysts.

/pdf/the-role-of-cu-on-the-reduction-behavior-and-surface-ghm35yi2lj.pdf

The role of Cu on the reduction behavior and surface properties of Fe-based Fischer–Tropsch catalysts

Brain arteriovenous malformations (AVMs) cause intracranial hemorrhage (ICH), especially in young adults. Molecular characterization of lesional tissue provides evidence for involvement of both angiogenic and inflammatory pathways, but the pathogenesis remains obscure and medical therapy is lacking. Abnormal expression patterns have been observed for proteins related to angiogenesis (e.g., vascular endothelial growth factor, angiopoietin-2, matrix metalloproteinase-9), and inflammation (e.g., interleukin-6 [IL-6] and myeloperoxidase). Macrophage and neutrophil invasion have also been observed in the absence of prior ICH. Candidate gene association studies have identified a number of germline variants associated with clinical ICH course and AVM susceptibility. A single nucleotide polymorphism (SNP) in activin receptor-like kinase-1 (ALK-1) is associated with AVM susceptibility, and SNPs in IL-6, tumor necrosis factor-a (TNF-a), and apolipoprotein-E (APOE) are associated with AVM rupture. These observations suggest that even without a complete understanding of the determinants of AVM development, the recent discoveries of downstream derangements in vascular function and integrity may offer potential targets for therapy development. Further, biomarkers can now be established for assessing ICH risk. These data will generate hypotheses that can be tested mechanistically in model systems, including surrogate phenotypes, such as vascular dys-plasia and/or models recapitulating the clinical syndrome of recurrent spontaneous ICH.

Genetic considerations relevant to intracranial hemorrhage and brain arteriovenous malformations.

A noble-metal free FeCu based bimetallic catalyst system prepared by facile co-impregnation method was found to be highly admirable for vapour phase selective hydrogenation of furfural to furfuryl alcohol at ambient pressure. Monometallic Cu/γ-Al2O3, Fe/γ-Al2O3 and bimetallic FeCu/γ-Al2O3 catalysts with different Fe loadings were prepared. Structural and morphological features of the catalysts were thoroughly investigated by several physico-chemical characterization techniques. The influence of various reaction parameters, such as Fe loading, reaction temperature and flow of reactants was examined with respect to furfural conversion and furfuryl alcohol yield. The results clearly showed that an optimum amount of Fe is necessary to enhance the catalytic activity of monometallic Cu/γ-Al2O3 for the selective hydrogenation of furfural. The catalyst FC-10 with 10 wt% Fe exhibited excellent activity which led to high furfural conversion (>93%) and furfuryl alcohol selectivity (>98%) under mild reaction conditions. The higher activity of bimetallic FeCu/γ-Al2O3 compared to monometallic Cu/γ-Al2O3 is ascribed to the formation of FeCu bimetallic particles and the existence of oxygen vacancies in the Fe oxide system. The superior activity after Fe loading on the Cu-based catalyst was attributed to the synergy between Cu and Fe. A plausible mechanism is proposed to explain the promoting effect of Fe, which involves synergism between Fe sites with strong oxophilic nature and Cu sites with a high ability for hydrogen activation. Based on the activity results, prolonged catalytic activity and spent catalyst analysis, the developed FeCu/γ-Al2O3 catalyst is inexpensive, eco-benign and robust, which makes it a promising candidate for the efficient conversion of biomass-derived substrates to fine chemicals and drop-in biofuels.

Promotional effect of Fe on the performance of supported Cu catalyst for ambient pressure hydrogenation of furfural

A long-held dogma in neurosurgery is that parenchymal arteriovenous malformations (AVMs) are congenital. However, there is no strong evidence supporting this theory. An increasing number of documented cases of de novo formation of parenchymal AVMs cast doubt on their congenital nature and suggest that indeed the majority of these lesions may form after birth. Further evidence suggesting the postnatal development of parenchymal AVMs comes from the exceedingly rare diagnosis of these lesions in utero despite the widespread availability of high-resolution imaging modalities such as ultrasound and fetal MRI. The exact mechanism of AVM formation has yet to be elucidated, but most likely involves genetic susceptibility and environmental triggering factors. In this review, the authors report 2 cases of de novo AVM formation and analyze the evidence suggesting that they represent an acquired condition.

/pdf/are-parenchymal-avms-congenital-lesions-pnxq6glvq9.pdf

Are parenchymal AVMs congenital lesions

Background: Brain arteriovenous malformations (BAVMs) are thought to be sporadic developmental vascular 
lesions, but familial occurrence has been described. We 
compared characteristics of patients with familial BAVMs 
with those of patients with sporadic BAVMs.
 Methods: We systematically reviewed the literature on patients with familial BAVMs. Three families that were 
found in our centre were added. Age, sex distribution 
and clinical presentation of the identified patients 
were compared with those in population-based series of 
patients with sporadic BAVMs. Furthermore, we calculated 
the difference in mean age at diagnosis of parents and 
children to study possible anticipation.
 Results: We identified 53 patients in 25 families with BAVMs. Mean age at diagnosis of patients with familial 
BAVMs was 27 years (range 9 months-58 years), which was 
younger than in the reference population (difference 
between means 8 years, 95% confidence interval (CI) 3-13 
years). Patients with familial BAVMs did not differ from 
the reference populations with respect to sex and mode 
of presentation. In families with BAVMs in successive 
generations, the age of the child at diagnosis was 
younger than the age of the parent (difference between 
means 22 years, 95% CI 13-30 years), which suggests 
clinical anticipation.
 Conclusions: Few patients with familial BAVMs have 
been described. These patients were diagnosed at younger 
age than sporadic BAVMs whereas their mode of 
presentation was similar. Although there are indications 
of anticipation, it remains as yet unclear whether the 
described families represent accidental aggregation or 
indicate true familial occurrence of BAVMs.

/pdf/familial-occurrence-of-brain-arteriovenous-malformations-a-20cirrm2xs.pdf

Familial occurrence of brain arteriovenous malformations: a systematic review

On the properties of silica-supported bimetallic Fe$z.sbnd;Cu catalysts Part I. Preparation and characterization

Dear Sirs,

A 62-year-old man experienced sudden shaking and dysesthesia of the right arm that lasted about 5 min. Several hours later, he developed dysesthesia in the right hand that rapidly spread to his shoulder and right side of his face and tongue. After 10 min, these symptoms disappeared completely. Four more similar events occurred in the following 2 weeks. A few months earlier, he had experienced three episodes with visual disturbances in his right hemifield that lasted 10 min and were followed by headache. His past medical history revealed myocardial infarction, renal insufficiency due to longstanding hypertension, hyperlipidemia, and polycythemia that was untreated for several years.

Neurological examination was normal. Laboratory investigations showed an increased hemoglobin (11.6 mmol/l, reference values 8.6–10.7 mmol/l), increased hematocrit (0.56, reference values 0.41–0.50), and heterozygosity for Factor V Leiden (FVL). EEG revealed no signs of epilepsy. Subarachnoid hemorrhage was seen on CT (Fig. 1b). DSA showed a DAVF (Fig. 1c) with cortical reflux (Cognard grade 2b; Borden type II) [1, 3] and thrombosis of the superior sagittal sinus. Venesections were initiated resulting in normal hemoglobin (10.2 mmol/l) and hematocrit (0.50). No more attacks occurred afterwards.



Fig. 1

T1-enhanced MR image shows multiple dilated intracranial and extracranial vessels (a). Non-enhanced CT scan shows subarachnoid hemorrhage especially in the right hemisphere (b). Diagnostic DSA shows a DAVF with arterial supply from medial meningeal and ...



Peroperative embolization using a burr hole directly above the fistula point was planned because tortuous feeders hampered a femoral approach and this combined approach was considered less invasive than neurosurgical occlusion. During the localizing DSA, the DAVF was found occluded with partial recanalization of the sinus (Fig. 1d–e). Follow-up MRI after 1 year showed no signs of recurrence of the fistula, a patent superior sagittal sinus, and obvious reduction of the dilated vessels (Fig. ​(Fig.11f).

DAVFs are one or more direct arteriovenous connections without intervening capillary bed. They are associated with trauma, cerebral venous sinus thrombosis (CVST), and thrombophilia [4, 8, 14]. Clinical outcome correlates with angiographic features. The retrograde flow into cortical veins in our patient is associated with a hemorrhage risk of 10% according to the Cognard classification [3]. Borden type II en III fistulas are associated with either progressive neurological deficits or hemorrhage [1].

Our case demonstrates that spontaneous obliteration of a DAVF can occur after treatment of polycythemia by venesections. The combination of polycythemia and heterozygosity for FVL had resulted in a prothrombotic state that probably caused gradual development of CVST and subsequent DAVF formation.

CVST commonly occurs in patients with a DAVF [14]. One hypothesis proposes opening of physiological arterial-venous shunts between meningeal arteries and venous sinuses due to increased venous pressure [7, 14]. A rat-model suggests that venous hypertension may decrease cerebral perfusion which induces angiogenesis with subsequent development of a DAVF [9, 14]. In our patient venous pressure probably decreased after normalization of the blood viscosity. Finally, organization of a thrombus in a dural sinus may lead to “growth” of dural arteries that are normally present in sinus walls, which may result in a direct communication between artery and sinus [2].

FVL is a risk factor for CVST [12], but is also implicated in the pathogenesis of DAVFs [4, 8, 15]. Moreover, polycythemia is a risk factor for CVST [12], and these patients are prone to ischemic events probably because increased blood viscosity leads to decreased cerebral blood flow [5, 11]. Venesections may increase flow in patients with polycythemia [6, 13].

Spontaneous obliteration of DAVFs has been described [4, 10]. Possible mechanisms include recanalization of CVST, intracranial bleeding (with mass effect or vasospasm leading to obliteration), or intrinsic compression of the DAVF in the sinus wall [10]. Based on the observation in our patient, we suggest that in patients with polycythemia and DAVFs that have a relatively low risk of hemorrhage, polycythemia should be treated before interventional treatment, because venesections may lead to spontaneous closure of the DAVF.

/pdf/spontaneous-obliteration-of-a-dural-arteriovenous-fistula-5gbu9ifdg0.pdf

Spontaneous obliteration of a dural arteriovenous fistula after treatment of polycythemia in a patient with factor V Leiden mutation: case report.

On the Properties of Silica-Supported Bimetallic Fe-Cu Catalysts. Part 1. Preparation and Characterization.

The current policy concerning methicillin-resistant Staphylococcus aureus (MRSA) in hospitals needs to be altered because there is no reliable proof that the isolation policy that is currently in force actually leads to any reduction in the prevalence of MRSA. Conversely, it has been proved that these isolation measures lead to poorer patient care, sometimes resulting in death.

The current MRSA policy in the Netherlands is doing more harm than good

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