Ring size and positional constraints for μ-hydrido-bridging in dimethylcycloalkyl cations (n = 6–9)

The in situ preparation and nmr characterization of a series of selected 1,n-dimethylcycloalkyl cations is reported. Both the 1,5-dimethylcyclononyl and the 1,5-dimethylcyclooctyl cations are assigned a μ-hydrido-bridged structure. However, the corresponding 1,4-dimethyIcyclooctyl, 1,4-dimethylcycloheptyl, and 1,4-dimethylcyclohexyl cations are normal unbridged tertiary cations. The μ-hydrido-bridged cyclononyl cation rearranges in part to the 1-methyl-5-ethylcyclooctyl cation which is also μ-hydrido-bridged and this rearrangement can be followed by noting the disappearance of the δ −5.8 μ-H peak of the former and the appearance of a δ −6.4 μ-H peak for the latter. The 1,5-dimethylcyclooctyl cation is the most thermally stable μ-hydrido-bridged cation yet prepared and possesses a chair – twist boat (TB) conformation which is "frozen-out" in the nmr spectrum at −120 °C. At higher temperatures one gets a [Formula: see text] equilibration, ΔG≠ = 30 kJ mol−1 from nmr line-broadening observations.

Bilateral posterior open-bite. Abbreviated case report

A case of bilateral posterior open-bite is reported since it is unusual to find the mandibular and maxillary molars on both sides in infraclusion.

Allergenic significance of some fungi prevailing in the respiratory tract of allergy patients--A preliminary study

The allergenic significance of some fungi prevailing in the respiratory tract of allergy patients was studied. The percentage of markedly positive intradermal reactions observed was higher in patients to the extracts of homologous fungi found in their respiratory passages as compared to the patients who did not show the same fungi in theri respiratory tact.

A study of the efficacy of typhoid vaccine in inducing humoral and cell-mediated immune responses in human volunteers

The nature of protective immunity against typhoid fever in man is not at present well understood. Work on animal models and earlier studies from this laboratory indicate an important protective role for cellular immunity. The present work attempts to study the efficacy of the conventional typhoid vaccine in inducing specific cellular and humoral immune responses. The study on fifty-eight new army recruits and thirty-one civilian volunteers showed adequate humoral responses after vaccination. However, vaccination failed to induce a significant cellular immune response. In addition, a transient suppression of cellular immunity was observed in the immediate post-vaccination period in ten subjects who possessed natural cellular immunity before vaccination. These findings indicate the need for improving the typhoid vaccine so that it will induce cellular immunity as well as a humoral response. It also points to the necessity for obtaining detailed knowledge of the post-vaccination anergy as it could be important in timing public health programmes.