The orbit rigidity matrix of a symmetric framework

A number of recent papers have studied when symmetry causes frameworks on a graph to become infinitesimally flexible, or stressed, and when it has no impact. A number of other recent papers have studied special classes of frameworks on generically rigid graphs which are finite mechanisms. Here we introduce a new tool, the orbit matrix, which connects these two areas and provides a matrix representation for fully symmetric infinitesimal flexes, and fully symmetric stresses of symmetric frameworks. The orbit matrix is a true analog of the standard rigidity matrix for general frameworks, and its analysis gives important insights into questions about the flexibility and rigidity of classes of symmetric frameworks, in all dimensions. With this narrower focus on fully symmetric infinitesimal motions, comes the power to predict symmetry-preserving finite mechanisms - giving a simplified analysis which covers a wide range of the known mechanisms, and generalizes the classes of known mechanisms. This initial exploration of the properties of the orbit matrix also opens up a number of new questions and possible extensions of the previous results, including transfer of symmetry based results from Euclidean space to spherical, hyperbolic, and some other metrics with shared symmetry groups and underlying projective geometry.Comment: 41 pages, 12 figure

A 3 month, follow-up, randomized, placebo-controlles study of repetitive transcranial magnetic stimulation in depression.

Background/Objective: There is evidence for an antidepressant effect of repetitive transcranial magnetic stimulation (rTMS), but little is known about posttreatment course. Therefore, we conducted a placebo-controlled, double-blind study in depressed patients in order to investigate the effect of rTMS on depression over 12 weeks after completion of the 2-week stimulation period. Method. 55 patients with a moderate or severe DSM-IV major depressive episode were randomly assigned to rTMS or sham treatment. rTMS was given daily for 10 days over the left dorsolateral prefrontal cortex with the following treatment parameters: 20 Hz, 20 trains of 2 seconds, 30 seconds between trains, and 80% motor threshold. The effect of rTMS on depression was rated repeatedly with the 17-item Hamilton Rating Scale for Depression (HAM-D) during the 2-week period of stimulation and the 12-week follow-up period conducted from 1997 to 2001. Results: We found a modest, clinically nonrelevant decrease in HAM-D scores in both rTMS and sham patients over 2 weeks of treatment. However, over the subsequent 12-week follow-up, the rTMS group continued to improve significantly compared with the placebo group. Conclusion: Decrease of depressive symptoms may continue after the cessation of rTMS stimulation

EEG evidence for shunt requirement during carotid endarterectomy: optimal EEG derivations with respect to frequency bands and anesthetic regimen.

Item does not contain fulltextCurrently there is no consensus on the derivations that should be used for EEG monitoring during carotid endarterectomy (CEA). The aim of this study was to determine which derivations distinguish the best between patients requiring a shunt and patients who do not need a shunt. Four predefined frequency bands and two regimens for general anesthesia (isoflurane versus propofol) were used. EEG data (16 channels) were obtained from 152 EEGs recorded during carotid endarterectomy. Analog EEG signals of preclamp and clamp periods of 100 seconds were digitized to compute power spectra. Changes in power during clamping were calculated for all possible derivations in four predefined frequency bands and were expressed as Z-scores. For each derivation, the area under the receiver operating characteristics curve was calculated. Derivations with the greatest area under the receiver operating characteristics curve were considered to distinguish the best between the shunt and the nonshunt groups formed in retrospect on the basis of consensus between three independent and experienced board-certified electroencephalographers. The two different anesthetic regimens resulted in different patterns of EEG changes because of clamping. The optimal derivations to differentiate between the shunt and the nonshunt groups also differed for the two anesthetic regimens, although for both conditions, anterior head regions were especially preferred. The optimal derivations are given for each anesthetic regimen

Transcranial Doppler blood flow assessment in patients with mild heart failure: Correlates with neuroimaging and cognitive performance

Item does not contain fulltextCardiac output and cerebral perfusion are reduced in patients with advanced stages of heart failure. Our aim was to determine whether cerebral blood flow velocity measured by transcranial Doppler ultrasonography was reduced in outpatients with mild heart failure in comparison to controls and, if so, whether this reduction was related to cognitive performance and abnormalities of the brain diagnosed by magnetic resonance imaging.5 p

Instruments for oral disease-intervention strategies : recombinant Lactobacillus casei expressing tetanus toxin fragment C for vaccination or myelin proteins for oral tolerance induction in multiple sclerosis

Lactobacillus strains possess properties that make them attractive candidates as vehicles for oral administration of therapeutics. In this report we describe the construction and analysis of recombinant Lactobacillus casei applicable in oral vaccination against an infectious disease (tetanus) and in oral tolerance induction for intervention in an autoimmune disease, multiple sclerosis. Recombinant L. casei which express surface-anchored tetanus toxin fragment C (TTFC) were generated. Quantitative analysis by flow cytometry demonstrated a high level of cell wall-bound expression of TTFC and immunogenicity was demonstrated by parenteral immunization with whole cell extracts of the recombinants. A series of expression vectors was constructed to secrete human myelin basic protein (hMBP) or hMBP as a fusion protein with β-glucuronidase from Escherichia coli. These heterologous products produced by L. casei were detected in the growth medium and parenteral immunization with this medium evoked antibodies against hMBP, confirming that secretion indeed had occurred. Based on the different localization of the heterologous proteins, lactobacilli expressing surface-anchored TTFC are ideally suited for the induction of antibody responses, whereas lactobacilli that secrete myelin proteins can be used for the induction of peripheral T-cell tolerance. In conclusion, the specific technology described here allows the construction of a wide array of safe live recombinant lactobacilli which may prove to be useful in oral intervention strategies for the prevention of infectious diseases or treatment of autoimmune diseases