Mechanisms of molecular motion of Mo(CO)6 in zeolites NaY and HY from 13C-NMR lineshapes

The potential of C-13-NMR spectroscopy of stationary samples for the study of mechanisms of anisotropic molecular motion of Mo(CO)(6) adsorbed in zeolites has been examined. Free diffusional rotation or jump processes about the various symmetry axes of the octahedral complex cause motional averaging of C-13 chemical shift anisotropy, allowing for the characterization of the different motional mechanisms. At 110 K a large portion of the Mo(CO)(6) molecules is firmly fixed in zeolites NaY and HY as indicated by a broad (ca. 410 ppm) chemical shift powder pattern. A narrow C-13-NMR component is observed in both zeolites for molecules undergoing isotropic motion or rotation about a three-fold axis. An additional line, which is inverted in shape and reduced in width by a factor of -1/2 compared to the rigid case, is only observed for NaY. This line is assigned to molecules undergoing free rotation about the four-fold axis, but it may also be due to Mo(CO)(6) jumping about a two-fold axis. The changes in the distribution of molecules in different motional states was explored between 1 10 K and ambient temperature. Molecules undergoing rotations or jumps about the four-or two-fold axes only exist in NaY at lower temperatures when stationary Mo(CO)(6) molecules are also present. At 180 K and higher temperatures, rotation about the three-fold axis or isotropic motion are the sole types of molecular motion. (C) 1997 Elsevier Science B.

Diagnosis and Treatment of Sciatica in the Netherlands:A Survey among Neurologists and Anesthesiologists

Background: This study aimed to assess how Dutch neurologists and anesthesiologists diagnose and treat people with sciatica in secondary care and to evaluate their adherence to the newest guidelines. Methods: We conducted a cross-sectional survey. Respondents were asked about their current clinical practice related to sciatica. Three authors rated the respondents' adherence to the guidelines on a three-point Likert scale. Results: Eighty neurologists and 44 anesthesiologists completed the questionnaire. Neurologists diagnose their sciatica patients primarily using a magnetic resonance imaging (89%). Selective diagnostic nerve blocks are considered useful by 81% of the neurologists. Neurologists primarily treat patients with pain medication, and 40% of them think epidural steroid injections are effective in 40-60% of injected patients. Twenty-nine percent of neurologists refer patients to a neurosurgeon after 4 months. Anesthesiologists consider a selective diagnostic nerve root block to have a higher diagnostic value than mapping. The most reported side effect of epidural injections is exacerbation of pain (82%). Pulse radiofrequency is applied in 9-11% of acute cases. The results also indicate that Dutch neurologists and anesthesiologists follow an evidence-based approach that is strictly or broadly in line with the guideline. Conclusions: Neurologists treat sciatica patients initially with pain medication and physiotherapy, followed by epidural steroid injections and referral for surgery. Anesthesiologists treat sciatica patients with one or more steroid injections or may perform a selective nerve root block. Imaging, selective nerve root blocks, medication, physiotherapy, and pulse radiofrequency are topics of further research

MRI/linac integration

\u3cp\u3ePURPOSE/OBJECTIVES: In radiotherapy the healthy tissue involvement still poses serious dose limitations. This results in sub-optimal tumour dose and complications. Daily image guided radiotherapy (IGRT) is the key development in radiation oncology to solve this problem. MRI yields superb soft-tissue visualization and provides several imaging modalities for identification of movements, function and physiology. Integrating MRI functionality with an accelerator can make these capacities available for high precision, real time IGRT.\u3c/p\u3e\u3cp\u3eDESIGN AND RESULTS: The system being built at the University Medical Center Utrecht is a 1.5T MRI scanner, with diagnostic imaging functionality and quality, integrated with a 6MV radiotherapy accelerator. The realization of a prototype of this hybrid system is a joint effort between the Radiotherapy Department of the University of Utrecht, the Netherlands, Elekta, Crawley, U.K., and Philips Research, Hamburg, Germany. Basically, the design is a 1.5 T Philips Achieva MRI scanner with a Magnex closed bore magnet surrounded by a single energy (6 MV) Elekta accelerator. Monte Carlo simulations are used to investigate the radiation beam properties of the hybrid system, dosimetry equipment and for the construction of patient specific dose deposition kernels in the presence of a magnetic field. The latter are used to evaluate the IMRT capability of the integrated MRI linac.\u3c/p\u3e\u3cp\u3eCONCLUSIONS: A prototype hybrid MRI/linac for on-line MRI guidance of radiotherapy (MRIgRT) is under construction. The aim of the system is to deliver the radiation dose with mm precision based on diagnostic quality MR images.\u3c/p\u3

Individualised prediction model of seizure recurrence and long-term outcomes after withdrawal of antiepileptic drugs in seizure-free patients: a systematic review and individual participant data meta-analysis

BACKGROUND: People with epilepsy who became seizure-free while taking antiepileptic drugs might consider discontinuing their medication, with the possibility of increased quality of life because of the elimination of adverse events. The risk with this action, however, is seizure recurrence. The objectives of our study were to identify predictors of seizure recurrence and long-term seizure outcomes and to produce nomograms for estimation of individualised outcomes. METHODS: We did a systematic review and meta-analysis, and identified eligible articles and candidate predictors, using PubMed and Embase databases with a last update on Nov 6, 2014. Eligible articles had to report on cohorts of patients with epilepsy who were seizure-free and had started withdrawal of antiepileptic drugs; articles also had to contain information regarding seizure recurrences during and after withdrawal. We excluded surgical cohorts, reports with fewer than 30 patients, and reports on acute symptomatic seizures because these topics were beyond the scope of our objective. Risk of bias was assessed using the Quality in Prognosis Studies system. Data analysis was based on individual participant data. Survival curves and proportional hazards were computed. The strongest predictors were selected with backward selection. Models were converted to nomograms and a web-based tool to determine individual risks. FINDINGS: We identified 45 studies with 7082 patients; ten studies (22%) with 1769 patients (25%) were included in the meta-analysis. Median follow-up was 5·3 years (IQR 3·0-10·0, maximum 23 years). Prospective and retrospective studies and randomised controlled trials were included, covering non-selected and selected populations of both children and adults. Relapse occurred in 812 (46%) of 1769 patients; 136 (9%) of 1455 for whom data were available had seizures in their last year of follow-up, suggesting enduring seizure control was not regained by this timepoint. Independent predictors of seizure recurrence were epilepsy duration before remission, seizure-free interval before antiepileptic drug withdrawal, age at onset of epilepsy, history of febrile seizures, number of seizures before remission, absence of a self-limiting epilepsy syndrome, developmental delay, and epileptiform abnormality on electroencephalogram (EEG) before withdrawal. Independent predictors of seizures in the last year of follow-up were epilepsy duration before remission, seizure-free interval before antiepileptic drug withdrawal, number of antiepileptic drugs before withdrawal, female sex, family history of epilepsy, number of seizures before remission, focal seizures, and epileptiform abnormality on EEG before withdrawal. Adjusted concordance statistics were 0·65 (95% CI 0·65-0·66) for predicting seizure recurrence and 0·71 (0·70-0·71) for predicting long-term seizure freedom. Validation was stable across the individual study populations. INTERPRETATION: We present evidence-based nomograms with robust performance across populations of children and adults. The nomograms facilitate prediction of outcomes following drug withdrawal for the individual patient, including both the risk of relapse and the chance of long-term freedom from seizures. The main limitations were the absence of a control group continuing antiepileptic drug treatment and a consistent definition of long-term seizure freedom. FUNDING: Epilepsiefonds

Prednisone 10 days on/10 days off in patients with Duchenne muscular dystrophy.

Contains fulltext : 81898.pdf (publisher's version ) (Closed access)Corticosteroids are effective in improving motor function in Duchenne muscular dystrophy (DMD) patients within 6 months-2 years of treatment initiation, but there is as yet no consensus on which treatment scheme is the best. We retrospectively analyzed data of 35 DMD patients who were treated with prednisone 0.75 mg/kg per day intermittently 10 days on/10 days off. Prednisone was started during the ambulant phase at age 3.5-9.7 years (median 6.5 years). The median period of treatment was 27 months (range 3-123 months). The median age at which ambulation was lost was 10.8 years (mean 10.9 years; 95% confidence interval 10.0-11.8 years). Nine patients (26%) had excessive weight gain. Eight boys (21%) had a bone fracture, which was when four of these eight children lost the ability to walk. Treatment was stopped in two obese patients, two hyperactive boys and one patient following a fracture. Our data suggest that prednisone 10 on/10 off has relatively few side effects and extends the ambulant phase by 1 year compared to historical controls