A new sputtering apparatus

The writer, in sputtering a large number of mirrors, has found that the apparatus and methods to be described have several advantages, particularly where very large and perfect mirrors are desired. The accompanying diagram will be self explanatory, and the dimensions given have been found convenient for mirrors up to 10 cm diameter

Note on the Spectra of the Disubstituted Acetylenes and of the Mustard Oils

It has been observed that in the Raman spectra of many disubstituted acetylenes the line corresponding to the so-called C≡C frequency is split into two components of not greatly different intensity (1), though this is not the case in the monosubstituted compounds. In the mustard oils the C≡N Raman line is double (2), and in allyl mustard oil (3), the one substance which appears to have been studied with sufficient dispersion, the corresponding infrared band shows definite indications of splitting into two components. This doubling is not observed in the organic thiocyanates. These facts have caused some speculation so far appear never to have received a satisfactory explanation. The presence of two fundamentals in the 2200 cm^-1 region appears quite impossible for most of the molecules showing the doubling, and on the other hand the coexistence of two forms of molecule with slightly different frequencies appears unlikely, especially in the case of the acetylenes. Consequently the author proposes an explanation involving a Fermi resonance interaction between the C≡C or C≡N fundamental, as the case may be, and the overtone of a certain other vibration of approximately one-half or one-third the frequency

On set systems with restricted intersections modulo p and p-ary t-designs

We consider bounds on the size of families ℱ of subsets of a v-set subject to restrictions modulo a prime p on the cardinalities of the pairwise intersections. We improve the known bound when ℱ is allowed to contain sets of different sizes, but only in a special case. We show that if the bound for uniform families ℱ holds with equality, then ℱ is the set of blocks of what we call a p-ary t-design for certain values of t. This motivates us to make a few observations about p-ary t-designs for their own sake

The Relation Between the Energy of a Hydrogen Bond and the Frequencies of the O[Single Bond]H Bands

It has previously been pointed out (1) that there appears to be a relation between the energy of a hydrogen bond and the shift of the frequency of the O-H bands which accompanies the formation of the bond. Recently additional data have been obtained in this laboratory (2,3) which confirm the existence of this useful relation and it seems worth while to discuss them in this connection. The data here presented all relate to linkages in which a hydroxyl hydrogen is concerned, though the atom to which it is weakly bound may be oxygen, chlorine, or carbon in an aromatic ring. It is surprising that the same connection between energy and frequency shift should be found in these various cases but such appears to be the fact. For other types of bond, for example those involving the hydrogen of an amino group, a slightly different relation may well be expected

Safe domain and elementary geometry

A classical problem of mechanics involves a projectile fired from a given point with a given velocity whose direction is varied. This results in a family of trajectories whose envelope defines the border of a 'safe' domain. In the simple cases of a constant force, harmonic potential and Kepler or Coulomb motion, the trajectories are conic curves whose envelope in a plane is another conic section which can be derived either by simple calculus or by geometrical considerations. The case of harmonic forces reveals a subtle property of the maximal sum of distances within an ellipse.Comment: Also available from http://democrite.in2p3.fr/democrite-0002317

Are Cost Conscious Community Colleges Sacrificing Quality?

Compared to their four-year public counterparts, community colleges have been more successful in holding down the costs of educating students but current research, albeit limited, suggests that this may have come at the expense of quality or at least outcomes. This essay addresses the questions surrounding this issue, including the behavior of costs at public two-year colleges and what the research says about quality and outcomes issues. It is based on my study of community colleges over the past twenty-five years