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The global healthcare system has been overwhelmed by the Coronavirus disease-2019 (COVID-19). In order to mitigate the risk of spread of the virus, most elective surgical procedures have been cancelled especially during the lockdown periods. The purpose of this study was to assess the financial impact of the COVID outbreak due to the supposed reduced workload from our neurosurgery department in 2020.Number of neurosurgical procedures (NSP) within the Department of Neurosurgery and their associated estimated income were retrospectively reviewed globally and month wise from administrative records of billing in 2020 and 2019 based on the Diagnosis related group (DRG) and severity of illness (4 levels).Overall, 824 and 818 inpatient surgical procedures were performed in 2019 and 2020 respectively. The total estimate revenue generated from inpatient surgeries was moderately decreased (3%): 9 498 226.41 euros in 2020 versus 9 817 361.65 euros in 2019 without significant difference across DRG (P=0.96) and severity of illness.Our data suggests a moderate negative impact of the COVID-19 pandemic had on neurosurgical and financial activity. However, a more in-depth medico-economic analysis need to be performed to assess the real financial impact.

Summary Background Deep brain stimulation (DBS) has been proposed to treat patients with severe Tourette's syndrome, and open-label trials and two small double-blind trials have tested DBS of the posterior and the anterior internal globus pallidus (aGPi). We aimed to specifically assess the efficacy of aGPi DBS for severe Tourette's syndrome. Methods In this randomised, double-blind, controlled trial, we recruited patients aged 18–60 years with severe and medically refractory Tourette's syndrome from eight hospitals specialised in movement disorders in France. Enrolled patients received surgery to implant bilateral electrodes for aGPi DBS; 3 months later they were randomly assigned (1:1 ratio with a block size of eight; computer-generated pairwise randomisation according to order of enrolment) to receive either active or sham stimulation for the subsequent 3 months in a double-blind fashion. All patients then received open-label active stimulation for the subsequent 6 months. Patients and clinicians assessing outcomes were masked to treatment allocation; an unmasked clinician was responsible for stimulation parameter programming, with intensity set below the side-effect threshold. The primary endpoint was difference in Yale Global Tic Severity Scale (YGTSS) score between the beginning and end of the 3 month double-blind period, as assessed with a Mann-Whitney-Wilcoxon test in all randomly allocated patients who received active or sham stimulation during the double-blind period. We assessed safety in all patients who were enrolled and received surgery for aGPi DBS. This trial is registered with ClinicalTrials.gov, number NCT00478842. Findings Between Dec 6, 2007, and Dec 13, 2012, we enrolled 19 patients. We randomly assigned 17 (89%) patients, with 16 completing blinded assessments (seven [44%] in the active stimulation group and nine [56%] in the sham stimulation group). We noted no significant difference in YGTSS score change between the beginning and the end of the 3 month double-blind period between groups (active group median YGTSS score 68·5 [IQR 34·0 to 83·5] at the beginning and 62·5 [51·5 to 72·0] at the end, median change 1·1% [IQR −23·9 to 38·1]; sham group 73·0 [69·0 to 79·0] and 79·0 [59·0 to 81·5], median change 0·0% [–10·6 to 4·8]; p=0·39). 15 serious adverse events (three in patients who withdrew before stimulation and six each in the active and sham stimulation groups) occurred in 13 patients (three who withdrew before randomisation, four in the active group, and six in the sham group), with infections in DBS hardware in four patients (two who withdrew before randomisation, one in the sham stimulation group, and one in the active stimulation group). Other serious adverse events included one electrode misplacement (active stimulation group), one episode of depressive signs (active stimulation group), and three episodes of increased tic severity and anxiety (two in the sham stimulation group and one in the active stimulation group). Interpretation 3 months of aGPi DBS is insufficient to decrease tic severity for patients with Tourette's syndrome. Future research is needed to investigate the efficacy of aGPi DBS for patients over longer periods with optimal stimulation parameters and to identify potential predictors of the therapeutic response. Funding French Ministry of Health.

The use of optogenetics or photobiomodulation in non-human primate (NHP) requires the ability to noninvasively stimulate large and deep cortical brain tissues volumes. In this context, the optical and geometrical parameters of optodes are critical. Methods and general guidelines to optimize these parameters have to be defined.We propose the design of an optode for safe and efficient optical stimulation of a large volume of NHP cortex, down to 3-5 mm depths without inserting fibers into the cortex.Monte Carlo simulations of optical and thermal transport have been carried out using the Geant4 application for tomographic emission (GATE) platform. Parameters such as the fiber diameter, numerical aperture, number of fibers and their geometrical arrangement have been studied. Optimal hardware parameters are proposed to obtain homogeneous fluence above the fluence threshold for opsin activation without detrimental thermal effects.The simulations show that a large fiber diameter and a large numerical aperture are preferable since they allow limiting power concentration and hence the resulting thermal increases at the brain surface. To obtain a volume of 200-500 mmThe present study defines a method to optimize the design of optode and the choice of stimulation parameters for optogenetics and more generally light delivery to deep and large volumes of tissues in NHP brain with a controlled irradiance dosimetry. The general guidelines are the use of silica fibers with a large numerical aperture and a large diameter. The combination of several fibers is required if large volumes need to be stimulated while avoiding thermal effects.

Resume Objectif Une evaluation de la prise en charge des cephalees secondaires aux hemorragies sous-arachnoidiennes (CHSA) a ete realisee en France dans les centres de neurochirurgie. Type d'etude Enquete nationale de pratique par voie postale. Methodes Un questionnaire a ete envoye aux centres hospitalo-universitaires assurant les urgences neurochirurgicales. Il concernait les methodes d'evaluation des CHSA, les antalgiques prescrits et leurs modes d'administration ainsi que l'opinion des centres vis-a-vis de l'efficacite de leurs protocoles antalgiques. Resultats Au total, 24 centres sur 34 ont repondu au questionnaire. Cinquante-quatre pour cent evaluaient l'intensite des cephalees par un interrogatoire non codifie et plus d'un centre sur deux ne faisaient aucune evaluation chez les patients ayant des troubles de la conscience. Le propacetamol et la morphine etaient le plus souvent utilises. La morphine etait administree par voie sous-cutanee par 75 % des centres, mais 25 % utilisaient aussi la titration et l'analgesie controlee par le patient. Trente-sept pour cent des centres etaient reticents a l'utilisation de la morphine et 75 % aux anti-inflammatoires non steroidiens ; 96 % des centres declaraient etre peu ou moyennement efficaces sur les CHSA. Conclusions La majorite des centres de neurochirurgie evaluaient insuffisamment et de facon non codifiee les CHSA, l'usage de certains antalgiques etait limite. Les equipes expliquaient le defaut d'efficacite de leurs prescriptions antalgiques par l'absence de consensus et l'usage restreint de la morphine et des AINS dans les CHSA.

Impairment in energy metabolism is thought to be involved in the aetiology of Huntington's disease. In line with this hypothesis, chronic systemic administration of the mitochondrial toxin 3-nitropropionic acid to rats and monkeys produces selective striatal lesions similar to Huntington's disease. The present study examined whether rats treated with varying regimen of 3-nitropropionic acid could present motor abnormalities reminiscent of Huntington's disease symptomatology, correlated with Huntington's disease specific striatal symptomatology. Subacute 3-nitropropionic acid treatment (15 mg/kg per day intraperitoneally for 10 days) produced dramatic motor symptoms associated with extensive neuronal loss and gliosis in the lateral striatum as well as severe hippocampal degeneration in 50% of the cases. In contrast, chronic 3-nitropropionic acid treatment (10 mg/kg per day subcutaneously for one month) led to more subtle excitotoxic-like lesions, selective for the dorsolateral striatum and more closely resembling Huntington's disease striatal pathology. Animals with these Huntington's disease-like lesions showed spontaneous motor symptoms including mild dystonia, bradykinesia and gait abnormalities, which were barely detectable on visual inspection but could be readily identified and quantified by computerized video analysis. In these chronic animals, the degree of striatal neuronal loss was significantly correlated with the severity of spontaneous motor abnormalities, as is the case in Huntington's disease. The present study demonstrates that chronic low-dose 3-nitropropionic acid treatment in rats results in a valuable model of both the histological features and motor deficits which occur in Huntington's disease. Despite the interanimal variability in terms of response to 3-nitropropionic acid treatment, this rat model may be particularly useful for evaluating the functional benefits of new therapeutic strategies for Huntington's disease, particularly those aiming to reduce the severity of motor symptoms.

The object retrieval detour task (ORDT) is a task designed to assess the functional and anatomical integrity of the fronto-striatal pathway in humans and nonhuman primates. This entry describes the ORDT task and its potential to detect a deficit and a restoration of a frontal-type cognitive deficit in primate displaying striatal pathologies.

Pain management in patients having a subarachnoid haemorrhage was assessed in French intensive care unit of neurosurgical centres.Nationwide survey.A standardized postal questionnaire was sent to senior doctor of every neurosurgical centres in France inquiring pain scores assessment, analgesics used and their routes of administration, centre's opinion about efficacy of pain management.Of the 34 centres, 24 returned completed questionnaires. Fifty four per cent of the centres evaluated pain intensity with a non valid pain score. In the case of patients in the comatose, pain was not evaluated in fifty four per cent of the centres. Paracetamol and morphine were the most currently used analgesics drugs. Morphine was administered subcutaneously by 75% of the centres. Six centres used also PCA. Thirty-seven percent of the centres were reluctant to use opioids and 75% to use NSAIDS.The majority of the centres considered pain management in patient suffering from subarachnoid haemorrhage (SAH) was not optimal and stressed the need to establish a well validated pain rating scale dedicated to SAH patients.

Huntington's disease (HD) is a monogenic neurodegenerative disease that affects the efferent neurons of the striatum. The protracted evolution of the pathology over 15 to 20 years, after clinical onset in adulthood, underscores the potential of therapeutic tools that would aim at protecting striatal neurons. Proteins with neuroprotective effects in the adult brain have been identified, among them ciliary neurotrophic factor (CNTF), which protected striatal neurons in animal models of HD. Accordingly, we have carried out a phase I study evaluating the safety of intracerebral administration of this protein in subjects with HD, using a device formed by a semipermeable membrane encapsulating a BHK cell line engineered to synthesize CNTF. Six subjects with stage 1 or 2 HD had one capsule implanted into the right lateral ventricle; the capsule was retrieved and exchanged for a new one every 6 months, over a total period of 2 years. No sign of CNTF-induced toxicity was observed; however, depression occurred in three subjects after removal of the last capsule, which may have correlated with the lack of any future therapeutic option. All retrieved capsules were intact but contained variable numbers of surviving cells, and CNTF release was low in 13 of 24 cases. Improvements in electrophysiological results were observed, and were correlated with capsules releasing the largest amount of CNTF. This phase I study shows the safety, feasibility, and tolerability of this gene therapy procedure. Heterogeneous cell survival, however, stresses the need for improving the technique.

Three cases of bacterial brain abscesses, in immunocompetent patients, are reported. In all these cases, the diffusion-weighted magnetic resonance (MRI) with apparent diffusion coefficient (ADC) map has permitted an early diagnosis and a rapid treatment. This emergency MRI showed in the three cases a low signal on TI-weighted images, a high signal on T2-weighted and echo-planar images, and a decrease of ADC (0.36- 0.49 x 10(-3) mm2/s). So, this new MRI technique provides an available and rapid element in the brain abscess diagnosis which often remains a complex clinical and radiological diagnosis.

The caudate nucleus and putamen form part of a complex but topographically connected circuitry that links the cortex, the basal ganglia and the thalamus. Within this complex system lie a series of functionally and anatomically segregated loops that allow the concurrent processing of a wide range of cognitive and motor information (Alexander et al., 1986; Alexander and Crutcher, 1990). As a constituent of these loops it has been shown that the striatum is involved in movement initiation, response selection and attentional processes (Robbins and Brown, 1990; Alexander, 1994; Lawrence et al., 1998). Although it is the medium spiny GABAergic projection neurones that are primarily lost in HD, it is not sufficient merely to replace the GABA. Instead it is crucial for striatal tissue transplants to integrate with the host tissue in such a way that the cortico-striatal-thalamic circuitry is restored and is functional. Rodent studies have progressed a long way in establishing the principle that striatal grafts can, at least partially, restore function and integrate appropriately with the host (Dunnett and Svendsen, 1993; Björklund et al., 1994; Sanberg et al., 1998) but the limited behavioural repertoire and the undifferentiated striatum meant that it was inevitable that studies should progress into primate models. Anatomical tracing studies have demonstrated that motor, premotor and somatosensory cortical areas send corticostriatal projections primarily to the putamen region in primates, whereas the head and body of the caudate nucleus mostly receive efferent input from associative cortical areas (Kemp and Powell, 1970; Kunzle, 1975, 1977, 1978; Selemon and Goldman-Rakic, 1985). Based on such anatomical, and functional, studies Alexander and colleagues have proposed the existence of at least five cortico-striatal-thalamic loops including a motor, a dorsolateral-prefrontal and an orbito-frontal loop (Alexander et al., 1986). The concentration of motor inputs to the putamen region suggests a particular involvement of this structure in the motor loop. Indeed, unilateral lesions of the putamen disrupt motor performance in the marmoset and generate apomorphine-induced dyskinesias in larger primates (Burns et al., 1995; Kendall et al., 2000). The implantation of striatal grafts into marmosets that had previously received unilateral putamen lesions ameliorated some of the motor impairments, which suggested at least partial restoration of the motor loop. In support of this we found direct evidence of host-graft cortico-striatal connectivity using an anterograde tracer injected in the primary motor cortical region (Kendall et al., 1998a). In larger primates, with lesions of the caudate and putamen, striatal [figure: see text] allografts and xenografts have been shown to reduce apomorphine-induced dyskinesias (Isacson et al., 1989; Hantraye et al., 1992; Palfi et al., 1998). The mechanism by which dyskinesias are elicited is not fully understood but alterations in firing patterns within both segments of the globus pallidus have been identified during dyskinetic movements (Matsumura et al., 1995). It seems likely that it would actually require re-establishment of afferent connections between the implanted putamen and the globus pallidus as well as of functioning dopamine receptors within the graft for the reduction in the dyskinetic profile to be observed. Certainly there is evidence, from rodent studies and the marmoset study described here, that close proximity of the graft to the globus pallidus yields better functional recovery (Isacson et al., 1986). In addition, anatomical tracing studies in rats have demonstrated connections between the implanted tissue and the host globus pallidus (Wictorin et al., 1989b, 1990) However, the relationship between graft placement and functional recovery remains to be fully substantiated.

The neuroprotective properties of cyclosporin A (CsA) are mediated by its ability to prevent mitochondrial permeability transition during exposure to high levels of calcium or oxidative stress. By using the mitochondrial toxin 3-nitropropionic acid (3NP), the present study assessed whether CsA could protect striatal neurons in vitro and in vivo. In vitro, 3NP produced a 20-30% reduction of striatal glutamic acid decarboxylase-immunoreactive (GAD-ir) neurons. A single treatment with CsA protected GAD-ir neurons from 3NP toxicity at lower (0.2 or 1.0 microM), but not at higher (5.0 microM) doses. Similar findings were seen when the cultures were treated twice with cyclosporin. In vivo experiments used the Lewis rat model of Huntington's disease (HD) in which a low 3NP dose was delivered subcutaneously through an osmotic minipump. Rats received unilateral or bilateral intrastriatal saline injections to disrupt the blood-brain barrier (BBB) and facilitate CsA reaching vulnerable neurons. In the first experiment, CsA treated 3NP-lesioned rats displayed significantly more dopamine-and adenosine-3;, 5;-monophosphate-regulated phosphoprotein (DARPP32-ir) neurons ipsilateral to BBB disruption compared to the contralateral intact striatum, indicating that disruption of the BBB maybe necessary for CsA's neuroprotective effects. In the second experiment, stereological counts of DARPP32-ir neurons revealed that CsA protected striatal neurons in a dose-dependent manner following bilateral disruption of the striatal BBB. Rats treated with the higher (15 or 20 mg/kg) but not lower (5 mg/kg) doses of CsA displayed greater numbers of DARRP32-ir striatal neurons relative to vehicle-treated 3NP-lesioned rats. Thus, under conditions in which CsA can gain access to striatal neurons, significant protection from 3NP toxicity is observed. Therefore, CsA or more lipophilic analogues of this compound, may be of potential therapeutic benefit by protecting vulnerable neurons from the primary pathological event observed in HD.

The endoscopic approach of the tumors of the third ventricle interests mainly the colloid cysts but also offers the possibilities of biopsies. Twenty two patients (16 men and 6 women, average age 41 years) presenting with hydrocephalus related to a tumor of the pineal area were treated by a ventriculostomy with attempt at biopsy : they are outside of the limits of this report. Twenty two other patients (15 men, 7 women, average age 39 years) were operated on from 1994 to 1999 for a colloid cyst, and 2 of them were admitted in emergency in sudden coma. The CT scan showed a colloid cyst (hyperdense in 16 patients) associated with an hydrocephalus, except for a patient previously shunted. The diameter of the cyst varied from 4 to 50 mm (average of 20 mm). All the patients were operated on using a rigid endoscope. Among the 20 patients presenting a tumor of the pineal area, a biopsy was possible only in 4 cases (20%). There were no hemorrhage nor neurological disorders. In all the cases, the size and the number of the specimens were sufficient to allow the histological diagnosis. For the patients presenting with colloid cyst, the average follow-up is 2 years. All the preoperative symptoms disappeared except for the memory disorders which were improved. The post-operative Evans index decreased significantly. No residual cyst was observed on the post-operative MRI in 14 patients (63%). Among these patients, an asymptomatic recurrence was observed and remained stable after 44 months of follow-up. A residual cyst was observed in 8 patients (36%), with a diameter from 5 to 25 mm (average 9 mm). No patient required a shunt procedure, and no patient presented hemorrhagic complication. Endoscopy is especially useful in the first line treatment of the colloid cysts of the third ventricle.

According to the development of neurosurgical endoscopy (and especially for third ventriculostomy), the endoscopic anatomy in hydrocephalus should be well known and utilized for orientation. The endoscopic pictures are obtained with a 30; telescope, acquired by a digitalized camera and visualized on a video monitor. The pictures are then numerized on a DKR system. Endoscopic anatomy of the third ventricle is described with a particular focus on the anatomical landmarks and their variations around the foramen of Monro, the anterior and posterior walls of the third ventricle. The knowledge of this anatomy is essential for the safety and the reliability of intraventricular endoscopic procedures.

Delayed abnormal movements can be observed in patients with acute neurologic insult after a prolonged period of apparent neurologic stability. To reproduce such a secondary neurologic manifestation in primates, the present experiment investigated whether systemic administration of subacute 3-nitropropionic acid (3NP), a mitochondrial toxin, could induce abnormal movements that were delayed and progressive over time. Four Cebus apella monkeys received systemic 3NP injections until acute neurologic signs manifested. The monkeys were regularly video-recorded and rated for abnormal movements for up to 15 weeks after the cessation of 3NP treatment. Five to 6 weeks after the 3NP treatment, monkeys displayed a significant increase in dyskinesias compared with pretreatment conditions. Over time the chorea attenuated, whereas the dystonic movements increased in intensity and severity which was characterized by a delayed decrease of peak tangential velocity. The intensity of abnormal movements and extent of affected body regions observed in each monkey were consistent with the size of basal ganglia hypersignal as documented by T2 sequence on magnetic resonance imaging. Thus, more severe motor impairments were associated with large magnetic resonance image abnormalities. This novel primate model may be particularly useful for studying the structural changes underlying delayed and progressive manifestations of abnormal movements with the ultimate goal of facilitating the evaluation of novel therapeutic strategies.

As part of a safety and tolerability study, a 65-year-old man with Parkinson's disease (PD) received monthly intracerebroventricular injections of glial-derived neurotrophic factor (GDNF). His parkinsonism continued to worsen following intracerebroventricular GDNF treatment. Side effects included nausea, loss of appetite, tingling, L'hermitte's sign, intermittent hallucinations, depression, and inappropriate sexual conduct. There was no evidence of significant regeneration of nigrostriatal neurons or intraparenchymal diffusion of the intracerebroventricular GDNF to relevant brain regions. Alternative GDNF delivery systems should be explored.

The results of a series of 65 consecutive patients operated on to relieve hemifacial spasm (HFS) at Pierre Wertheimer Hospital in Lyon and at the Henri Mondor Hospital in Creteil using the same microvascular decompression (MVD) method are reported.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces clinical, biochemical and neuropathologic changes reminiscent of those which occur in idiopathic Parkinson's disease. 7-Nitroindazole (7-NI) is a relatively selective inhibitor of the neuronal isoform of nitric oxide synthase (NOS) that blocks MPTP neurotoxicity in mice. We now show that 7-NI protects against profound striatal dopamine depletions and loss of tyrosine hydroxylase-positive neurons in the substantia nigra in MPTP-treated baboons. Furthermore, 7-NI protected against MPTP-induced motor and frontal-type cognitive deficits. These results strongly implicate a role of nitric oxide in MPTP neurotoxicity and suggest that inhibitors of neuronal NOS might be useful in treating Parkinson's disease.

The results of a series of 65 consecutive patients operated on to relieve hemifacial spasm (HFS) at Pierre Wertheimer Hospital in Lyon and at Henri Mondor Hospital in Creteil, using the same microvascular decompression (MVD) method, are reported. MDV was performed through a retromastoid keyhole approach. A neurovascular conflict (NVC) was found in 62 cases (i.e., 95.5%). The conflicting vessel was the posterior inferior cerebellar artery (PICA) in 23 cases (35.4%), the anterior inferior cerebellar artery (AICA) in 22 cases (33.8%), the vertebro-basilar artery (VBA) with PICA and/or AICA in 13 cases (20%), and VBA alone in 4 cases (3.1%). The conflicting artery was maintained apart from the REZ of VII nerve by interposing a ball made of Teflon fibers and/or a plaque of Dacron. Forty-five patients (69.2%) were totally cured, 16 patients (24.6%) had only a partial (more than 50%) improvement, and in 4 patients (6.2%) surgery failed. Follow-up ranged from 1 month to 13 years (mean: 4 years and 8 months). Important was that in 9 patients, total relief of spasm occurred only secondarily with a delay sometimes as long as one year. Post-operative complications were dominated by: 1) facial nerve deficits in 16 cases (24.6%), of which 14 were transient and 2 were permanent; 2) hearing decrease in 10 cases (15.4%), of which 5 were transient and 5 were permanent. These complications were encountered at the start of the experience and at a time when monitoring of intraoperative brainstem auditory evoked potentials (BAEP) was not routinely done. Our data proved to be consistent with those published in the literature.

Botulinum toxin produces a transient presynaptic focal block at the neuromuscular junction. Thus it induces muscle weakness which has a significant beneficial effect on hemifacial spasm. Fifty-four patients were treated and received at least 2 and at the most 22 consecutive injections over a 5-year period. Injections were repeated every 9 weeks on average. The interval between injections corresponded to the time elapsed between the last injection and the re-emergence of spasms. Nineteen patients abandoned the treatment for various reasons. The most frequent side-effect was a ptosis which was observed in 1 out of 6 injections. Ptosis is due to diffusion of the botulinum toxin over a territory larger than expected. The results obtained in 42 patients were analyzed: there was no effect in 7 patients (17%); 11 patients improved by less than 50%; 13 by 50 to 70% and 11 more than 75%.

Homologation of n-pentane and cyclopentane results in formation of benzene on Ru, Os, Re and Ir/SiO2 catalysts. Formation of benzene can be explained by the insertion of carbene into terminal vinilic carbon followed by C6-dehydrocyclization.

Heats of adsorption of methane, ethane, propane, ethylene, propylene, acetylene, methylacetylene, allene, and cyclopropane were measured at room temperature in an adsorption calorimeter on platinum films deposited in the 10 −9 Torr region. Adsorption of methane produced a relatively low heat at a very low rate, and only a very limited adsorbed amount was achieved. The heat fell strongly as the surface coverage increased. Dehydrogenation of the methane molecule to CH 2 and CH 3 surface species was proposed to explain this behavior. Initial heats of adsorption of ethane and propane were relatively high, pointing to both cracking and partial dehydrogenation of these alkanes. A strong decrease of the heats with increasing coverage and a rather low extent of adsorption suggested that some specific surface sites were required. Acetylene and methylacetylene gave virtually the same heat which was initially lower than that of ethane and propane, but higher than that of alkenes. The heat did not exhibit any clear-cut dependence on the coverage in the major part of the investigated range. Adsorption of alkynes took place on a higher proportion of the surface compared to alkanes and alkenes. Nondissociative adsorption with the formation of perpendicularly attached surface species CCH 2 and CCHCH 3 , respectively, appears to be compatible with the experimental results. Heats of adsorption of monoalkenes were lower than the heats of alkanes and also of alkynes, and mildly decreased with the increasing surface coverage. Partial dehydrogenation of the hydrocarbons and adsorption of the mobile split-off hydrogen atoms on the energetically most favorable sites were suggested to account for the observed behavior. Adsorption of allene produced an essentially coverage-independent heat which was higher than the heat of monoalkenes. A tentative interpretation involves formation of the same adsorbed structure as in the case of the isomeric methylacetylene. The initial heat of adsorption of cyclopropane was higher than that of alkenes, but slightly lower than that of propane. Partial dehydrogenation and limited, if any, fragmentation of the molecule are likely.

The effects of pre-irradiation with γ-rays of heat treatment in vacuum on the surface acidity and basicity of TiO 2 , Fe 2 O 3 , V 2 O 5 and Cr 2 O 3 and on the radiocatalytic decomposition of 2-propanol have been studied. Since pre-irradiation and heat treatment have very different effects, the radiocatalytic effects cannot be accounted for by local, radiation-induced, temperature increase. The radiocatalytic effects are attributed to transfer of absorbed radiation energy from the catalysts. This conclusion is supported by comparing the yields of the gas- and of the liquid phase radiolysis with the radiocatalytic transformation of 2-propanol.

70 kGy of γ-irradiation enhances the catalytic transformation of 2-propanol into acetone and propylene on transition metal oxides. Fragment products are formed and for TiO2, V2O5 and Fe2O3 the selectivity of 2-propanol decomposition is shifted towards dehydration by the irradiation. Both catalytic and radiocatalytic transformation of 2-propanol correlate with the adsorption capacity of metal oxides, which suggests, that irradiation acts mainly on the adsorbed 2-propanol. Possible changes in the catalyst's chemical properties due to the irradiation are discussed.

Hydrogen–deuterium exchange in methane, ethane and propane, hydrogenolysis of ethane, n-butane and isobutane and chemisorption of methane and ethane have been studied on rhenium powder catalysts.The kinetic isotope effect and the rate sequences of the exchange reactions mentioned above show that the rate limiting step is C—H bond dissociation.Ethane hydrogenolysis overlaps ethane exchange at 523 K. The hydrogenolysis reaction order with respect to hydrogen is slightly positive for ethane and greater than unity for butane. Methane is the main product of butane hydrogenolysis. Hydrogen assisted thermal desorption of methane produced from chemisorbed ethane evolves a peak with a maximum at 560–570 K, similar to the thermal desorption peak of methane. Therefore a strong, multiple metal–carbon bond is involved in rhenium–saturated hydrocarbon interaction, C—C bond breaking takes place easily but desorption of the reaction products is hindered.