Removal Of C1 Research Articles

Adsorption Thermodynamics and Kinetics of Light Hydrocarbons on Microporous Activated Carbon at Low Temperatures

The removal of light hydrocarbons from exhaust air and process gas is important for a variety of applications, e.g., in natural-gas treatment. However, particularly at lower concentrations, the removal of C1 and C2 hydrocarbons is either very expensive or unfeasible with standard technology. Adsorption processes at temperatures below 0 °C may provide a technical solution, but until today, no systematic study on the dynamics of trace adsorption at low temperatures is available. Therefore, in this work, we present breakthrough curve experiments of ethane, propane, and n-butane over a temperature range from +20 to −80 °C and a concentration range from 5 to 1000 Pa on microporous activated carbon. Equilibrium loadings are calculated and modeled with the temperature-dependent Toth equation. From dynamic simulations of the experimental breakthrough curves, kinetic parameters are determined. The lowering of temperature results in the slowdown of kinetics, which, however, is overcompensated by a simultaneous capa...

Phytosphingosine degradation pathway includes fatty acid α-oxidation reactions in the endoplasmic reticulum

Although normal fatty acids (FAs) are degraded via β-oxidation, unusual FAs such as 2-hydroxy (2-OH) FAs and 3-methyl-branched FAs are degraded via α-oxidation. Phytosphingosine (PHS) is one of the long-chain bases (the sphingolipid components) and exists in specific tissues, including the epidermis and small intestine in mammals. In the degradation pathway, PHS is converted to 2-OH palmitic acid and then to pentadecanoic acid (C15:0-COOH) via FA α-oxidation. However, the detailed reactions and genes involved in the α-oxidation reactions of the PHS degradation pathway have yet to be determined. In the present study, we reveal the entire PHS degradation pathway: PHS is converted to C15:0-COOH via six reactions [phosphorylation, cleavage, oxidation, CoA addition, cleavage (C1 removal), and oxidation], in which the last three reactions correspond to the α-oxidation. The aldehyde dehydrogenase ALDH3A2 catalyzes both the first and second oxidation reactions (fatty aldehydes to FAs). In Aldh3a2-deficient cells, the unmetabolized fatty aldehydes are reduced to fatty alcohols and are incorporated into ether-linked glycerolipids. We also identify HACL2 (2-hydroxyacyl-CoA lyase 2) [previous name, ILVBL; ilvB (bacterial acetolactate synthase)-like] as the major 2-OH acyl-CoA lyase involved in the cleavage (C1 removal) reaction in the FA α-oxidation of the PHS degradation pathway. HACL2 is localized in the endoplasmic reticulum. Thus, in addition to the already-known FA α-oxidation in the peroxisomes, we have revealed the existence of FA α-oxidation in the endoplasmic reticulum in mammals.

The suboccipital midline approach to foramen magnum meningiomas: safety and efficacy in a series of 23 consecutive patients over a 5-year period

Dear Editor, We appreciated the Editorial BThe suboccipital midline approach to foramen magnum meningiomas; feasible, but is it optimal?^ by Dr. Dehdashti [1] about the paper we recently published on Acta [2]. We would like to take this opportunity to reply to the author, providing readers with required additional clinical data. We are obviously unable to answer the question asked by Dr. Dehdashti because a specifically designed study to address this issue is not currently available in the literature. As encouraged by the author, we revised the outcome of 23 consecutive patients undergoing resection of a FM meningioma via a midline suboccipital (MSO) approach over the last 5 years at our department. Overall morbidity and mortality rates were 8.7 % and 0 %, respectively. At 3 months after surgery, eighteen (78.2 %) patients improved, four (17.3 %) were stable, and one (4.3 %) worsened. Four (17.3 %) patients presented a transient postoperative deficit of IX–X cranial nerves. No patient presented a postoperative XII cranial nerve deficit. One patient (4.3 %) presented a postoperative CSF fistula that spontaneously resolved over 2 months. The tumor size ranged between 19 and 34mm. GTR (Simpson grade I and II) was achieved in 100% of cases. The mean hospital stay was 16 days (range, 9–37 days). Published literature on MSO approach for FM meningiomas reports similar data [4, 5]; these series are all about meningioma of small to medium size. In this sense, we suppose that it could be misleading to state that the MSO approach is more adequate for larger FM meningiomas. In an interesting review on the far lateral (FL) approach for FM meningiomas, Flores et al. [3] recently reported an overall morbidity and mortality rate of 30 % and 0–3 %, respectively. Post-operative IX–X and XII deficit rate was 44 and 33 %, improving over time in 66 % of cases. CSF fistula was reported in 16–20 %. With regard to preoperative status, 80.6 % improved, 6.7 % was stable, and 9.1 % worsened. GTR (Simpson grade I and II) was reported in 70–96 % of cases. Some intraoperative considerations are needed to compare MSO and FL approaches in this specific setting. Meningiomas located in the region Banterior^ to the brainstem, in the region of the foramen magnum, are only rarely strictly anterior (two cases in our series); the large majority of tumors pointed laterally on one side of the midline, and the brainstem was displaced posterolaterally rather than posteriorly. This aspect has already been described by other authors [4]. The dural attachment is usually just medially located to the site of vertebral artery (VA) entry. Thus, when approaching an FMmeningioma via anMSO approach, the tumor devascularization is easy and safe to perform. The brainstem, cranial nerves, vertebral artery, and tumor are exposed in the same field, and the dissection can be performed with visualization of all structures. The exposure is wide and not deep and it can easily be improved (when needed) from a lateral perspective by the use of an appropriate angulation of the microscope (as shown in our paper). The vertebral artery is exposed easily in the region of the arch of atlas at the site of its entry into the dura by a midline approach. However, the suggested two-step (before and after dural opening) removal of C1 allows a tailored bone resection and a safer VA exposure and control. Dural and wound closure with an MSO approach is easy and safe, and it avoids the possible difficulties described in the lateral and anterior approaches. The brainstem manipulation, when needed approaching smaller and more anterior FM meningiomas, as in the * Alessandro Della Puppa alessandro.dellapuppa@sanita.padova.it

Rapidly progressing monoparesis caused by Chiari malformation type I without syringomyelia

Background:Patients with Chiari malformation type I (CM-I) can manifest neurological symptoms, such as headache, neck pain, dysesthesia, swallowing disturbance, and paresis, which are usually stable or slowly progressive even if syringomyelia is coexistent. In some instances, however, acute onset of neurological symptoms has been reported but the pathogenetic mechanism and subsequent clinical course have not been explained. In those cases, it was reported that urgent treatment of foramen magnum decompression (FMD) was very effective. This work reports that an 11-year-old girl with CM-I subacutely developed unique symptoms and that urgent treatment of FMD was very effective.Case Description:We present here an 11-year-old girl with CM-I who subacutely developed dysphagia, left upper extremity monoparesis and sensory dysesthesia, with the limb assuming a peculiar posture at rest, with the wrist in extension and the elbow joint in flexion. Although her symptoms were assumed to be due to previously diagnosed CM-I without syringomyelia, no differences on magnetic resonance imaging (MRI) could be found except for slight change in the shape of tonsils compared with the previous ones. FMD and C1 removal with duraplasty was performed and resulted in an excellent neurological recovery.Conclusion:This case is a reminder that the presence of a new neurological deficit referable to nuclei within, or tracts that traverse, the cerebromedullary junction is a firm surgical indication for FMD in a patient with CM-I. MRI was nearly identical during the asymptomatic and symptomatic periods in this case, and did not explain the timing of symptom onset.