Evidence for a kaon-bound state K(-)pp produced in K(-) absorption reactions at rest

We have searched for a deeply bound kaonic state by using the FINUDA spectrometer installed at the e(+)e(-) collider DAPhiNE. Almost monochromatic K(-)'s produced through the decay of phi(1020) mesons are used to observe K(-) absorption reactions stopped on very thin nuclear targets. Taking this unique advantage, we have succeeded to detect a kaon-bound state K(-)pp through its two-body decay into a Lambda hyperon and a proton. The binding energy and the decay width are determined from the invariant-mass distribution as 115(+6)(-5)(stat)(+3)(-4)(syst) MeV and 67(+14)(-11)(stat)(+2)(-3)(syst) MeV, respectively.

Detection of landmines by using 14MeV neutron tagged beams

A large-area scanning system using 14 MeV tagged neutrons has been built. The associated (4)He particles emitted in the D+T reaction are detected in an array of Parallel Plate Avalanche Counters that defines a scanning plane having about 10 x 100 cm(2) area. Coincident gamma-rays are detected by 10 BaF(2) scintillators. The capability of the system to determine the presence and the position of samples and to perform an on-line background subtraction is demonstrated. Test with landmines are also reported. This technique allows a significant improvement of the signal-to-noise ratio searching for hidden threat materials. The use with portable sealed-tube generators is foreseen.

Development of a thermal neutron sensor for Humanitarian Demining

A thermal neutron sensor prototype for Humanitarian Demining has been developed, trying to minimize cost and complexity of the system as required in such application. A (252)Cf source or a sealed-tube neutron generator is employed to produce primary fast neutrons that are thermalized in a moderator designed to optimize the neutron capture reaction yield in buried samples. A description of the sensor, including the performances of the acquisition system based on a Flash ADC card and final tests with explosive simulants are reported. A comparison of the sensor performance when using a radioactive source to that when employing a sealed-tube neutron generator is presented. Limitations and possible applications of this technique are discussed.

Three-dimensional annihilation imaging of trapped antiprotons

We demonstrate three-dimensional imaging of antiprotons in a Penning trap, by reconstructing annihilation vertices from the trajectories of the charged annihilation products. The unique capability of antiparticle imaging has allowed, for the first time, the observation of the spatial distribution of the particle loss in a Penning trap. The radial loss of antiprotons on the trap wall is localized to small spots, strongly breaking the azimuthal symmetry expected for an ideal trap. Our observations have important implications for detection of antihydrogen annihilations.

Positron plasma diagnostics and temperature control for antihydrogen production

Production of antihydrogen atoms by mixing antiprotons with a cold, confined, positron plasma depends critically on parameters such as the plasma density and temperature. We discuss nondestructive measurements, based on a novel, real-time analysis of excited, low-order plasma modes, that provide comprehensive characterization of the positron plasma in the ATHENA antihydrogen apparatus. The plasma length, radius, density, and total particle number are obtained. Measurement and control of plasma temperature variations, and the application to antihydrogen production experiments are discussed.

Production and detection of cold antihydrogen atoms

A theoretical underpinning of the standard model of fundamental particles and interactions is CPT invariance, which requires that the laws of physics be invariant under the combined discrete operations of charge conjugation, parity and time reversal. Antimatter, the existence of which was predicted by Dirac, can be used to test the CPT theorem-experimental investigations involving comparisons of particles with antiparticles are numerous. Cold atoms and anti-atoms, such as hydrogen and antihydrogen, could form the basis of a new precise test, as CPT invariance implies that they must have the same spectrum. Observations of antihydrogen in small quantities and at high energies have been reported at the European Organization for Nuclear Research (CERN) and at Fermilab, but these experiments were not suited to precision comparison measurements. Here we demonstrate the production of antihydrogen atoms at very low energy by mixing trapped antiprotons and positrons in a cryogenic environment. The neutral anti-atoms have been detected directly when they escape the trap and annihilate, producing a characteristic signature in an imaging particle detector.

Neuronal plasticity of interrelated cerebellar and cortical networks

The comprehension of the cerebellar physiology is rapidly changing in particular because of the demonstration of the cerebellar importance on cognition. In the present paper, recent data on cerebro cerebellar interactions is reviewed, particularly focusing on cerebellar influences over the neurophysiology of primary motor and primary sensory cortices. The cerebellar role in implicit learning and in sensory data processing is analysed and discussed. It is proposed that the cerebellum could control cortical plastic changes by modulating cortical excitability in a discrete topographic manner and that this mechanism could induce the coupling between significant sensory inputs and definite motor outputs considered as the neurobiological substrate for implicit learning.

The Apolipoprotein E genotype in patients affected by syndromes with focal cortical atrophy

The role of the Apolipoprotein E (APOE) alleles in syndromes associated with focal cerebral atrophy (fronto-temporal dementia, primary progressive aphasia, corticobasal degeneration) is still controversial. We studied the APOE allele distribution in 39 patients with clinically diagnosed syndromes associated with focal cerebral atrophy (FCA), in 50 patients with early-onset probable Alzheimer's disease (EOAD), and in 60 patients with late-onset probable AD (LOAD). The APOE genotype was determined from a blood sample, using polymerase chain reaction and restriction enzyme digestion. The APOE epsilon4 allele frequency was significantly higher in the EOAD (21.0%) and LOAD (33.3%) groups, but not in the FCA group (5.1%), as compared with controls. In our population, the epsilon2 allele frequency was significantly higher in patients with FCA (12.8%) than in controls (4.8%). These results show that the APOE epsilon4 allele is not a risk factor for syndromes associated with FCA. The potential role of the epsilon2 allele in these syndromes needs further investigation.

Functional changes of the primary somatosensory cortex in patients with unilateral cerebellar lesions

Although cerebellar lesions do not cause evident sensory deficits, it has been suggested recently that the cerebellum might play a role in sensory acquisition and discrimination. To determine whether the cerebellum influences the early phases of cortical somatosensory processing, we recorded cortical somatosensory evoked potentials after median nerve stimulation in five patients with unilateral cerebellar damage. We also performed a dipolar source analysis of traces by means of brain electrical source analysis. In all patients, the amplitude of the frontal N24 and parietal P24 components, as well as the strength of the corresponding dipolar sources, were significantly smaller after stimulation of the symptomatic side. These neurophysiological findings indicate that the primary somatosensory cortical processing is altered after contralateral cerebellar damage. They represent the first indication of a possible substrate for the reduction in cerebral blood flow observed in the parietal cortex after cerebellar lesion. Furthermore, the present data allow characterization of the functional influence of the cerebellar input to the primary somatosensory cortex as specifically acting over the inhibitory components of somatosensory processing.

One year follow up of spinal cord injury patients using a reciprocating gait orthosis: preliminary report

OBJECTIVE

To examine the influence of social, physical and psychological factors in determining the usage/non usage of reciprocating gait orthosis (RGO) in spinal cord injury (SCI) patients.

DESIGN

Prospective clinical trial.

SETTING

A large rehabilitation hospital in Rome, Italy.

PARTICIPANTS

Twenty four SCI patients of traumatic aetiology (all fulfilling the criteria to prescribe the device).

METHODS

Social, physical and neurological examination according to ASIA standards; psychological enquiry by means of the Eysenck Personality Questionnaire (EPQ) and the scale for self rating anxiety and depression of the Cognitive Behavioural Assessment.

RESULTS

After 1 year follow up 11 (46%) of our patients no longer used the RGO. There was no statistically significant difference between patients who used the RGO and those who rejected the orthosis with regard to social and physical data. There was a significant difference (P=0.005 at the end of training and P=0.003 at 1 year follow up) with regard to functional ambulation level. With regard to psychological enquiry RGO-non users showed a higher frequency of values over the mean in the E scale (extroversion) of the EPQ than RGO-users (P=0.05).

CONCLUSIONS

None of the identified parameters were useful to predict the use/rejection of the orthosis. Although they need to be confirmed, our psychological data suggest that extensive psychological testing could be useful to sharpen the ability to predict.

Verbal short-term store-rehearsal system and the cerebellum. Evidence from a patient with a right cerebellar lesion

We describe an 18-year-old patient who underwent surgical removal of the right cerebellar hemisphere for the presence of a neoplastic lesion. After surgery, the patient's neuropsychological examination was normal except for a transient selective verbal short-term memory (STM) impairment characterized by reduced verbal digit span and rapid forgetting of verbal material. An extensive examination of the patient's deficit was performed in order to identify which of the two components of STM (phonological short-term store and/or rehearsal system) was impaired. The functional locus of the deficit was identified at the level of the phonological output buffer, a component of the rehearsal system, as suggested by the pattern of results obtained, namely: the improvement of the digit span seen with pointing compared with the verbal response; the advantage of auditory over visual presentation of digits; and the lack of a phonological-similarity effect with visual presentation of letters. On the other hand, the functioning of the phonological store was demonstrated by the normal amplitude of the recency effect in free recall of words and by the phonological-similarity effect with auditory presentation of letters. Our finding is consistent with previous functional (PET) studies showing the involvement of the right cerebellum during tasks requiring silent recirculation of verbal information. We conclude that the cerebellum takes part in the planning of speech production at a level that does not require an overt articulation.

Oxidative stress and overexpression of manganese superoxide dismutase in patients with Alzheimer's disease

Substantial evidence supports the hypothesis that oxygen free radicals are involved in various neurodegenerative disorders. To assess the presence of oxidative stress in Alzheimer's disease (AD) we examined the activity of the enzyme copper-zinc superoxide dismutase (CuZnSOD) in red blood cells, the levels of the mitochondrial inducible enzyme manganese superoxide dismutase (MnSOD) mRNA in lymphocytes, and the total radical-trapping antioxidant capacity (TRAP) in plasma of AD patients and in a group of age-matched non-demented controls. We found that CuZnSOD activity (P < 0.01 vs. controls) was significantly increased as well as the MnSOD mRNA levels while the total antioxidant status (P < 0.001 vs. controls) was decreased in AD patients. These findings support the role of oxidative alterations in the pathogenetic mechanism underlying AD neurodegeneration.

Apolipoprotein E genotype in sporadic early- and late-onset Alzheimer's disease

The 84 isoform of apolipoprotein E (ApoE) has been proposed as a risk factor for Alzheimer's disease (AD), while the possible role of the epsilon2 allele in AD is controversial. We have studied the ApoE genotype in 38 patients with early-onset AD (EOAD) and in 43 patients with late-onset AD (LOAD). In the EOAD group we observed a significant increase of epsilon4 allele frequency as compared with normal controls, while there was a more than 3-fold decrease of epsilon2 allele frequency that did not reach statistical significance. In the LOAD group we found a highly significant increase of epsilon4 allele frequency as compared with normal controls, while there was a significant decrease of epsilon2 allele frequency. In both the EOAD and LOAD groups, no significant difference was observed between epsilon4 carriers and epsilon4 noncarriers as for age at disease onset, disease duration, and Mini-Mental State score at observation. However, in both EOAD and LOAD groups a statistical trend towards a longer disease duration was observed in epsilon4 carriers. In both the EOAD and LOAD groups, disease severity was compared in epsilon4 carriers versus epsilon4 noncarriers by means of analyses of covariance, with disease duration as covariate. No significant difference between epsilon4 carriers and epsilon4 noncarriers was observed in both EOAD and LOAD. The results of the present study confirm that epsilon4 allele seems to be associated with an increased risk for sporadic AD, while the significant decrease of epsilon2 allele frequency in the LOAD group supports the hypothesis of a possible protective role of epsilon2 allele in AD.