Corrispondenze birazionali e topologia di varietà algebriche

Sunto § 1:Introduzione. — Parte prima:Alcune proprietà di dilatazioni e contrazioni, nonché dei loro prodotti. § 2:Generalità sugli elementi irregolari delle corrispondenze birazionali. § 3:Influenza delle dilatazioni sopra la base per le varietà algebriche contenute in una data. § 4:Alcune proprietà delle transformazioni birazionali fra superficie. § 5:Estensioni alle varietà superiori. — Parte seconda:Topologia di varietà algebriche tagliate, ed applicazioni alle corrispondenze birazionali. § 6:Premesse. § 7:Proprietà omologiche d’immersione di una varietà algebrica in un’ altra. § 8:Alcune applicazioni alle trasformazioni birazionali.     

Ion dynamic correction to the profile of the forbidden 23P-43F transition of He(I)

Dynamic corrections due to ion (and emitter) motion have been calculated for the profile of the forbidden 2³P-4³F transition of He(I) for ion density n_i = 10¹⁵ cm^-3 and plasma temperature T = 10⁴ K. The calculation is based on a “corrected binary collision treatment”; comparison is made with a similar approach published previously by Barnard, Cooper, and Smith.     

钇铝石榴石单晶缺陷的X射线透射形貌术观察

对提拉法生长的YAG单晶首次用X射线透射形貌术观察。揭示了YAG单晶的生长条纹、奇异小面以及垂直于生长条纹的位错线束等生长缺陷,并对这些缺陷作了简要的分析。 关键词：     

Critical dynamics of vesicle stretching transition in elongational flow

We present results on the stretching of single tubular vesicles in an elongation flow toward dumbbell shapes, and on their relaxation. A critical strain rate epsilonc exists; for strain rates epsilon相似文献   

Monitoring degradation in paper: non-invasive analysis by unilateral NMR. Part II

High quality paper samples have been oxidized with a specific oxidant to reproduce one of the possible causes of the aging of paper. All samples have been characterized by 13C CP-MAS NMR spectroscopy. The artificial aging of paper has been monitored using a standard NMR relaxometer and the results have been compared with the corresponding data obtained using an unilateral NMR relaxometer. Experimental values obtained with both techniques are in agreement, demonstrating that unilateral NMR relaxometric measurements constitute a suitable non-invasive method for assessing the degradation process of cellulose-based materials. The sensitivity of the non-invasive NMR method allows the detection of degradation even at a very early stage. Effects due to the sample volume and to the penetration depth have been investigated.     

Structures and NMR Parameters of 1,2-Diphenylcyclobutanes

A new reaction scheme for obtaining cis and trans 1,2-diphenylcyclobutane is described. Using ¹H-NMR at 600 MHz, full spectral assignment was made for both isomers, obtaining all J coupling constants and chemical shifts. NMR results on cis and trans 1,2-diphenylcyclobutane are compared with the vicinal coupling constants obtained by the Barfield–Smith equations from the literature internal and dihedral angles of cyclobutane. In the trans isomer, in agreement with previous results on halo-cyclobutanes, the conformation with the phenyls in the pseudo-di-equatorial position is strongly preferred. On the contrary, the cis isomer fluctuates between the two equivalent conformations: phenyl pseudo-axial and pseudo-equatorial.