Band-filling effects on electron-phonon properties of normal and superconducting state

We address the effect of band filling on the effective electron mass $m^*$ and the superconducting critical temperature $T_c$ in a electron-phonon system. We compare the vertex corrected theory with the non-crossing approximation of the Holstein model within a local approximation. We identify two regions of the electron density where $m^*$ and $T_c$ are enhanced or decreased by the inclusion of the vertex diagrams. We show that the crossover between the enhancement at low density and the decrease towards half filling is almost independent of the microscopic electron-phonon parameters. These different behaviors are explained in terms of the net sign of the vertex diagrams which is positive at low densities and negative close to half filling. Predictions of the present theory for doped MgB$_2$, which is argued to be in the low density regime, are discussed.Comment: 13 revtex pages, figures eps include

Caratterizzazione antigenica dell'emoagglutinina e della neuraminidasi dei ceppi di virus influenzale di tipo B isolati in Italia nel 1962, 1967 e 1971.

The hemagglutinin and neuraminidase antigens of 3 influenza type B viruses isolated in Italy during the epidemics of 1962, 1967 and 1971 were characterized. As reference strains, the prototypes B/Lee/40, B/Bon/43, B/Johannesburg/58, B/Taiwan/62 and B/Hong Kong/8/73 were chosen. The data obtained with specific chicken antisera show that the hemagglutinins of the Italian strains have an immunological relation between themselves and with the hemagglutinating antigen of the B/Johannesburg and B/Taiwan viruses. Only in the case of B/Hong Kong/8/73 strain no cross reactivity with the earlier viruses was found. However the B/Hong Kong immune serum inhibited at low titer hemagglutinin of B/Taiwan virus. The neuraminidases of the Italian strains appear very similar and highly correlated with the enzymes of the B/Johannesburg and B/Taiwan viruses. Also the neuraminidase of B/Hong Kong is strictly related to that of previously prevalent viruses with the exception of the B/Lee and B/Bon. The behaviour of homologous and heterologous hemagglutination and neuraminidase inhibition antibody in the sera of patients (age over 10 years) involved in the three epidemics was studied. At the hemagglutination inhibition and neuraminidase inhibition tests the majority of the patient sera reacted also with the heterologous strains. It is concluded that the B influenza viruses belong to the same antigenic spectrum

Stato dell'immunit\ue0 della popolazione milanese verso il nuovo ceppo di tipo B, B/Hong Kong/8/73 e studio del potere immunizzante del vaccino di vecchia composizione. Immunity status of the Milanese population towards B-Hong Kong-8-73, the new B type strain and study of the immunizing activity of the old composition vaccine

In view of the possibility that the new B Hong Kong strains which have a completely new hemoagglutinin would spread during the epidemic season, a serological survey was carried out on 180 serum samples collected between November and December 1972 in Milan from people aged 4 to over 60 yr. Because of limited data indicating that the neuraminidase of the new strains is antigenically related to that of earlier B strains, both hemagglutination inhibiting antibodies (HIA) and antineuraminidase antibodies (ANab) against the B/Hong Kong/8/773 strain were titrated. To gain information on the possibility that, lacking adequate aliquots of the new vaccine, some degree of protection could be conferred also by current vaccine preparations, both types of antibody were titrated in sera of children given a polyvalent vaccine including the strain B/Roma/67. The results indicated that HIA are almost absent in the Italian population since it was found only at low titers (1:10 - 1:20) in 12% of the sera, while ANab were present in 28 out of 57 sera examined and their level was over 1:20 in 25%. Judging from the behavior of the HIA, the response to the vaccine including the B Roma/67 strain was very poor. None of the 32 children developed antibody at titer >1:20. On the contrary ANab were found in 22 of the children (out of 25 examined) after a single dose of vaccine and all but one had ANab at titer >1:20 after the second dose. It is concluded that a certain degree of protection against the new B viruses could be afforded also by current vaccines

Controllo clinico, studio dell'escrezione virale e valutazione della risposta in anticorpi circolanti e locali dopo somministrazione di vaccino influenzale vivente ed attenuato contenente il ceppo "Alice"

Thirty four young adults were inoculated intranasally by nose drops, with two doses, two weeks apart, of inhibitor resistant 'Alice' vaccine strain of A/England/42/72 (H3N2). By the rate of volunteers with clinical reactions, always mild and short lasting, the vaccine showed a low degree of reactogenicity. Viral shedding was evidenced only the day after the first dose and was limited to two vaccines. Two weeks after the first dose homologous serum h.i.a. appeared in all the 15 volunteers lacking prevaccination antibody and significant titer rises occurred in a substantial number of vaccine recipients with low titers. The incidence of subjects with h.i.a. at titers considered to be protective ( 651:40), which was 26% before vaccination, rose to 93% in fully vaccinated volunteers. Very likely because of the presence of n.i.a. in the prevaccinal serum of all the volunteers, the n.i.a. response was less satisfactory. The vaccine induced h.i.a. to A/Port Chalmers/73 e A/Scotland/74 (H3N2) variants, although in a lower number of subjects and at a lower titer than to the homologous strain. Serum h.i. and n.i. antibody response appeared not to be significantly increased by a second dose. H.i.a., never present in the first sample, were found in the nasal washings taken two weeks after the second dose from 9 out of 16 vaccinees examined. Antibody was detected more frequently in the specimens with relatively high levels of protein and IgA. Secretory n.i.a., already demonstrable in 7 volunteers before vaccination, were acquired by all but one at the end of the experience