Resisting the Bohr Atom: The Early British Opposition

When Niels Bohr’s theory of atomic structure appeared in the summer and fall of 1913, it quickly attracted attention among British physicists. While some of the attention was supportive, others was critical. I consider the opposition to Bohr’s theory from 1913 to about 1915, including attempts to construct atomic theories on a classical basis as alternatives to Bohr’s. I give particular attention to the astrophysicist John W. Nicholson, who was Bohr’s most formidable and persistent opponent in the early years. Although in the long run Nicholson’s objections were inconsequential, for a short period of time his atomic theory was considered to be a serious rival to Bohr’s. Moreover, Nicholson’s theory is of interest in its own right.     

Pilot study on railway noise attenuation by belts of trees

Sound levels from passing trains were recorded. Both maximum A-weighted sound pressure levels L_{A, max} and equivalent levels L_Aeq over 60 second time periods containing each pass-by were measured. Recordings of 15 pass-bys were made at each of two different sites. At each site attenuation over level, grass-covered ground and through shelter belts was measured 1.5 m above ground. Attenuation differences at each site were due to both minor variations in terrain configuration (track above/below adjacent terrain) and to attenuation in vegetation. The latter cannot be separated. L_Aeq attenuations were smaller than L_A,max attenuations, as should be expected. Noise reduction by shelter belts—i.e., the approximate difference between attenuation over grass-covered ground and thouugh vegetation, respectively—was nearly the same, expressed in L_{A, max} and L_Aeq values. Shelter belts selected for this investigation were carefully maintained. Their overall structure, therefore, was very uniform. Behind a dense, 15 year old shelter belt, 50 m wide, consisting of beeches and various conifers planted between older birches and elms, noise levels were 8 to 9 dB lower than in level grass-covered country. Behind a dense, 10 to 20 year old shelter belt, 25 m wide, consisting of oaks, hornbeams, poplars, silver firs and various sorts of bushes, noise levels were 6 or 7 dB lower than in level grass-covered country. The attenuations measured seemed to be of such an order of magnitude that similar belts of trees and bushes could be a means of practical noise reduction. Further investigations, therefore, seem to be worthwhile.     

Exceptions and counterexamples: Understanding Abel's comment on Cauchy's Theorem

It may seem odd that Abel, a protagonist of Cauchy's new rigor, spoke of “exceptions” when he criticized Cauchy's theorem on the continuity of sums of continuous functions. However, when interpreted contextually, exceptions appear as both valid and viable entities in the early 19th century. First, Abel's use of the term “exception” and the role of the exception in his binomial paper is documented and analyzed. Second, it is suggested how Abel may have acquainted himself with the exception and his use of it in a process denoted critical revision is discussed. Finally, an interpretation of Abel's exception is given that identifies it as a representative example of a more general transition in the understanding of mathematical objects that took place during the period. With this interpretation, exceptions find their place in a fundamental transition during the early 19th century from a formal approach to analysis toward a more conceptual one.     

Ultra-fine particles of TiN

Ultra-fine particles of TiN have been produced by evaporating titanium in an atmosphere of helium and nitrogen. After evaporation titanium is cooled by the helium gas and small particles are formed. These are extremely reactive and react with the nitrogen gas making nitride. The particles were either collected as a powder on a vertical tube cooled by liquid nitrogen, or as a surface coating on some areas of the tungsten crucible. The produced powder was observed to consist of single crystalline particles with sizes ranging from 5 to 20 nm. The only phase observed was the δ-phase (fcc, NaCl-structure), and the dominating particle morphology was cubic with (100)-surfaces. Due to the size of the particles it was not possible to determine the stoichiometry by accurate lattice parameter measurements. However, quantitative electron energy loss spectroscopy (EELS) was applied on single particles and indicated a quite low content of nitrogen (about 33 at%). Some areas of the tungsten evaporation source were covered with a 10 μm thick TiN coating with its typical yellowish colour. The grains had a size of 1–10 μm and a rectangular shape. The grains were heavily stressed and had an amount of nitrogen quite similar to that of the small particles.     

Applications to metal K pre-edges of transition metal dimers illustrate the approximate origin independence for the intensities in the length representation

ABSTRACT

X-ray absorption spectroscopy (XAS) in the metal K pre-edge is a standard probe of electronic and geometric structure of transition metal complexes. Simulating the K pre-edge spectra requires contributions beyond the electric dipole, but if that term is non-zero, the second-order terms, e.g. electric quadrupoles, are no longer origin-independent. In the velocity representation, complete origin independence can be achieved by including all terms to the same order in the oscillator strength. Here, we implement that approach in the length representation and use it for restricted active space (RAS) simulations of metal K pre-edges of iron monomers and dimers. Complete origin independence is not achieved and the size of the remaining errors depends on the electric dipole oscillator strength and its ratio in length and velocity representations. The error in the origin independence is in the ANO basis sets two orders of magnitude smaller than the value of the individual contributions. For systems with strong electric dipole contributions, the errors are not significant within 3 Å from a metal centre, far enough to handle many multi-metal systems. Furthermore, we discuss the convergence of the multipole expansion, the possibility to assign spectral contributions, and the origin of negative absorption intensities.     

Z?llner’s Universe

The idea that space is not Euclidean by necessity, and that there are other kinds of “curved” spaces, diffused slowly to the physical and astronomical sciences. Until Einstein’s general theory of relativity, only a handful of astronomers contemplated a connection between non-Euclidean geometry and real space. One of them, the German astrophysicist Johann Carl Friedrich Z?llner (1834–1882), suggested in 1872 a remarkable cosmological model describing a finite universe in closed space. I examine Z?llner’s little-known contribution to cosmology and also his even more unorthodox speculations of a four-dimensional space including both physical and spiritual phenomena. I provide an overview of Z?llner’s scientific work, of his status in the German scientific community, and of the controversies caused by his polemical style of science. Z?llner’s cosmology was effectively forgotten, but there is no reason why it should remain an unwritten chapter in the history of science.     

Mannanase Transfer into Hexane and Xylene by Liquid–Liquid Extraction

The formation of noncovalent complexes between glycosidase, endo-1,4-β-d-mannanase, and ionic surfactant di(2-ethylhexyl) sodium sulfosuccinate (AOT) was shown to promote protein transfer into organic solvents such as xylene and hexane. It was found that mannanase can be solubilized in hexane and in xylene with concentration at least 2.5 and 2.0 mg/ml, respectively. The catalytic activity of the enzyme in hexane spontaneously increases with the concentration of AOT and is about 10% of the activity in aqueous system. In xylene, a catalytic activity higher than that in bulk aqueous conditions was found for the samples containing 0.1–0.3 mg/ml of mannanase, while for the samples with a higher concentration of enzyme, the activity was hardly detected.     

The Effect of the Molecular Weight of Polyvinylpyrrolidone and the Model Drug on Laser-Induced In Situ Amorphization

Laser radiation has been shown to be a promising approach for in situ amorphization, i.e., drug amorphization inside the final dosage form. Upon exposure to laser radiation, elevated temperatures in the compacts are obtained. At temperatures above the glass transition temperature (T_g) of the polymer, the drug dissolves into the mobile polymer. Hence, the dissolution kinetics are dependent on the viscosity of the polymer, indirectly determined by the molecular weight (M_w) of the polymer, the solubility of the drug in the polymer, the particle size of the drug and the molecular size of the drug. Using compacts containing 30 wt% of the drug celecoxib (CCX), 69.25 wt% of three different M_w of polyvinylpyrrolidone (PVP: PVP12, PVP17 or PVP25), 0.25 wt% plasmonic nanoaggregates (PNs) and 0.5 wt% lubricant, the effect of the polymer M_w on the dissolution kinetics upon exposure to laser radiation was investigated. Furthermore, the effect of the model drug on the dissolution kinetics was investigated using compacts containing 30 wt% of three different drugs (CCX, indomethacin (IND) and naproxen (NAP)), 69.25 wt% PVP12, 0.25 wt% PN and 0.5 wt% lubricant. In perfect correlation to the Noyes–Whitney equation, this study showed that the use of PVP with the lowest viscosity, i.e., the lowest M_w (here PVP12), led to the fastest rate of amorphization compared to PVP17 and PVP25. Furthermore, NAP showed the fastest rate of amorphization, followed by IND and CCX in PVP12 due to its high solubility and small molecular size.