Experimental Deductions Research Articles

Singlet Methylcarbene: Equilibrium Geometry or Transition State?

The isomerization of singlet methylcarbene to ethylene has been studied using ab initio quantum mechanical methods, resulting in high-level theoretical predictions of the transition-state structure and isomerization barrier height. Basis sets as large as triple-[zeta] plus double polarization plus carbon atom f and hydrogen atom d functions [TZ2P(f,d)] have been used with the self-consistent-field (SCF) configuration interaction, including all single and double excitations (CISD), and coupled cluster, including all single and double substitution (CCSD) methods, as well as CCSD with the effects of connected triple excitations added perturbatively [CCSD(T)]. The geometries for ground-state singlet methylcarbene and the transition state are both of C[sub 1] symmetry. The classical barrier is predicted to be 2.0 kcal mol[sup [minus]1], while the activation energy ([Delta]E[sub 0]) is 1.2 kcal mol[sup [minus]1] at the TZ2P(f,d) CCSD(T) level at 0 K; and the free energy barrier is [Delta]G[sup 0] = 1.5 kcal mol[sup [minus]1] at 298 K. The activation energy is 0.3 kcal mol[sup [minus]1] higher for fully deuterated singlet methylcarbene. Therefore singlet methylcarbene appears to be a true intermediate, consistent with some experimental deductions. 18 refs., 1 fig., 5 tabs.

A new method for quantitative investigation of dissipative flux behaviour

In order to study the pinning force F p of type II superconductors in a quantitative way, we first measured the internal friction (IF) during magnetization of Bi 0.8Pb 0.2SrCaCu 2O y superconductor and found that a characteristic IF peak occurs only if the sample is vibrating and the magnetic field is changing in time. The experimental results and theoretical deductions indicate that a non-linear force exists which is proportional to the product of the oscillating force on the magnetic flux (during IF measurement) and ( F d − F p), where F d is the driving force arising from the nonzero gradient of the flux density. Our analysis shows that if one can measure the absolute value of the d.c. magnetization against the external magnetic field, the pinning force for the sample can be determined quantitatively.

Molecular dynamics study of a sodium octanoate micelle in aqueous solution

The structure of a sodium octanoate micelle, consisting of 15 monomers in aqueous solution, has been studied by molecular dynamics calculations. The micelle was found to be stable over the length of the simulation (0.2 ns). The overall size and net charge of the micelle are both in excellent accord with experimental deductions. Micellization yields an increased proportion of trans conformations in the alkyl chains. The results of our simulation of the micelle and solvent appear to offer support for studies based on more simplified models.

Study of electron solvation in liquid ammonia using quantum path integral Monte Carlo calculations

The solvation of an electron in liquid ammonia has been studied using quantum path integral Monte Carlo calculations. In agreement with previous experimental and theoretical deductions the charge distribution of the electron is compact. Various distribution functions characterizing the structure around the solvated electron are presented and the surrounding solvent structure is compared to that around a classical atomic anion. A qualitative discussion is given of the absorption spectrum based upon the form of the complex time dependence of the electron mean squared displacement correlation function.

Low-energy excitonic resonances in metals. I. Experiments on divalent atoms.

We report differential ellipsometric measurement of optical constants for impurities in dilute alloys. For Mg, Zn, and Ca impurities in Li metal an impurity-specific absorption feature occurs in the (2--3)-eV range, superposed on an impurity-induced Drude background. The peaks are the ${\mathrm{ns}}^{2}$\ensuremath{\rightarrow}nsnp excitations of the free divalent atoms, red-shifted by metallic screening. These are identified as low-energy excitonic resonances in which the photoexcited electron and hole linger together in the impurity cell under their mutual interaction. Single-particle approximations to the optical properties cannot reproduce these explicit two-carrier effects. The three species exhibit different behaviors with increasing composition. For Mg impurities, the resonance can be followed across the entire Li-Mg phase diagram, where in pure Mg metal it becomes the ``interband transition.'' We infer that an excitonic resonance enhances the interband process. The following paper explores the explicit consequences of the electron-hole interaction, using a many-electron approach to small clusters, which appears to confirm the experimental deductions.

Adjuvant chemotherapy of breast cancer: hope--reality--hazard?

According to a NIH Consensus-Development Statement, adjuvant polychemotherapy following mastectomy is considered beneficial to premenopausal patients with positive axillary nodes. Nevertheless, the role of adjuvant chemotherapy in relation to menopausal status, axillary lymph node status, estrogen receptor status, choice and dose of agents, and long-term survival is not defined. Based on experimental background information and theoretical deductions, the clinical results have fallen short of expectations. The data of Bonadonna's CMF study reveal that the overall 5-year survival is increased by 4%; premenopausal patients benefit by 12% whereas treated postmenopausal patients have a 5% less chance of survival. Only those patients benefit who can tolerate a "full or nearly full dose"; these are only 17%. At this time it is not clear whether the small survival differences from adjuvant chemotherapy represent a real step forward in the fight against breast cancer. In the majority of patients (75 to 85%), at the time of adjuvant chemotherapy, systemically disseminated cancer cells are at mitotic rest or their proliferation is minimal. At this stage, adjuvant chemotherapy has no or little effect. Therefore, only a small proportion of patients (15 to 25%) has subclinical systemic cancer growth at the time of primary therapy or thereafter; only these patients have a chance to respond to chemotherapy. In view of this tumor kinetic problem and the hazards of chemotherapy, it seems advantageous (a) to focus on definition of patient subgroups at high risk for early recurrence post primary therapy to serve as participants in trials of adjuvant chemotherapy and/or (b) to concentrate on early diagnosis of recurrent disease for immediate institution of endocrine- and/or polychemotherapy.

Connection between dynamics and initial conditions of unstable systems

A connection is proposed between the total hamiltonian and the initial state vector for unstable systems. This connection makes it possible to reconcile experimental results and theoretical deductions for the decay law at all times.

Evolution and the Genetics of Populations. Vol. 3 Experimental Results and Evolutionry Deductions.

Evolution and the Genetics of Populations. Vol. 3 Experimental Results and Evolutionry Deductions.

The temperature dependence of the 8920 Å band of NO2 and the location of the 000–000 band of the transition

The absorption spectrum of NO2 cooled to −30 °C has been photographed at high dispersion in the wavelength region 8200–9100 Å. Comparison with the room temperature spectrum shows that weak absorption from the ground state of the molecule underlies slightly stronger 'hot' band absorption at 8920 Å. Franck–Condon calculations based on the relative intensities of absorption bands from the 000 and 010 vibrational levels of the molecule indicate that the 000–000 band of the [Formula: see text] electronic transition lies near 10250 Å (1.21 eV) with a possible uncertainty of one quantum of ν2′ (0.09 eV). This result is in good agreement with the multiconfiguration SCF calculations of Gillispie and Khan (which are at variance with previous experimental deductions on the location of the 000–000 band).Some new assignments have been made in the rotational structure of the 8360 Å band.

Determination of the mass-anisotropy exciton splitting in silicon

Splitting ▵ and oscillator strength ration η of the fundamental exciton in Si, which is spectroscopically unresolved, are determined by application of weak [001] deformations, bringing the components separately into light, and subsequent extrapolation to the zero-stress limit. The observed behavior matches a theoretical analysis of the stress dependence and leads to ▵ = 0.29 ± 0.05 meV and η = 5.5 ± 0.5. Comparison with theory and with previous indirect experimental deductions is made.

Evolution and the Genetics of Populations. Volume 3. Experimental Results and Evolutionary Deductions.

Evolution and the Genetics of Populations. Volume 3. Experimental Results and Evolutionary Deductions.

The Chapter on Weirs in the Codex of Juanelo Turriano: A Question of Authorship

In paying posthumous homage to Ladislao Reti, Bern Dibner made reference to the articles Reti published in this journal concerning the remarkable manuscript ofJuanelo Turriano preserved in the Madrid National Library.1 This manuscript, the Turriano Codex, owes its vital importance to the fact that it is the earliest known treatise on hydraulic engineering. It is, furthermore, of a high technical standard, to the extent that its author may be fairly described as a rationalist. He bases his arguments, wherever possible, on his own experimental deductions, instead of on tradition; he thus applies to technology that philosophy of science which was born during the Renaissance.

Hydrogen transfer steps in the catalytic hydrogenolysis of cyclohexane

The rate of the isotopic exchange reaction: cyclo- ∗C 6H 12(g) + C 6(g) → cyclo-C 6H 12(g) + ∗C 6(g) (1) was studied over metal and metal oxide catalysts. C 6 included: n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, and 2,3-dimethylbutane. The catalysts tested were: Pt supported on acidified and nonacidified Al 2O 3, Cr 2O 3, Re-Cr 2O 3, Cr 2O 3-Al 2O 3 and Re-Al 2O 3,. The temperature range was 230 to 427 °C. The rate of reaction (1) was studied as a function of the ratio p c 6 p CHA in the range 3 × 10 −2 to 1 × 10 2. Since the reaction steps underlying reaction (1) include hydrogen transfer and rearrangement of the molecular structure, the experimental results have been analyzed in terms of these steps and information on their rate and thermodynamic and stoichiometric characteristics has been derived. The analysis suggested a mechanism for the transfer step that is influenced by catalyst acidity and hydro-carbon structure. Models for the reactive surface layer in metal and metal oxide catalysts are put forward and employed to indicate possibilities for the active sites at the surface. The models are also useful to interpret the observed phenomena of inversion in surface reactivity as a function of gas-phase composition. Finally, the experimental results and theoretical deductions are viewed in the framework of present information on the hydrogenolysis of cycloalkanes and isomerization of C 6 paraffins. The advantages of reaction (1) for fundamental studies on the hydroconversion of cycloalkanes are pointed out.

Theoretical study of a 1 : 1 complex between quinone and hydroquinone

AbstractThe Variable Electronegativity Pariser–Parr–Pople method has been successfully applied to calculate the potential energy curve for the formation of a 1: 1 complex between quinone and hydroquinone. A consistent evaluation of core and electronic repulsion integrals is important to obtain a meaningful curve. A computationally simple procedure has been suggested for separating interactions due to electron exchange between the components from other intermolecular interactions. In agreement with experimental deductions the preferred configuration for the quinone‐hydroquinone complex is found to be one in which the molecules are in parallel planes with their C—O bonds parallel. The equilibrium separation between the molecular planes is found to be 2.3 Å and the stabilization energy in this position is 1.2 eV. In this equilibrium position forces due to electron exchange constitute the major contributing factor to the stability of the complex.

Cylindrical Pressure Vessels: Stress Systems in Plain Cylindrical Shells and in Plain and Pierced Drumheads

This paper is limited in its scope to three specific aspects of pressure vessel stressing:— (1) The presentation of experimental evidence that stresses arising from out-of-circularity in shells may be calculated by the method of Haigh Welding Research Committee (1936)‡, and deductions from this fact. (2) The presentation of the results of plain drumhead stress range calculations carried out by the ‘beam-on-elastic-foundation’ method of Wells (1950); experimental corroboration and deductions therefrom. (3) Some notes on manhole drumhead stressing and reinforcement. The first of these aspects has reached a fairly acceptable degree of finality. The second has been carried a stage forward but it calls for discussion and the pooling of further data. The work on manhole drumhead stressing and reinforcement is continuing, and the present paper must be regarded as an interim statement in that respect.

Constitution of Alkali Halide-Borate Glasses

Majumdar, Banerjee and Banerjee claim to have demonstrated1 that sodium chloride dissolved in borax glass was present in the form of crystallites, and also that sodium chloride–boric oxide glasses gave the X-ray diffraction pattern of sodium chloride (together with some unidentified lines). The experimental work and deductions there from demand some comment and criticism.

XXXIV. Research on combined stress and anisotropy

Abstract This paper discusses the effect of departure from isotropism in the specimen on the yield point under various stress combinations, and analyses the experimental results and deductions drawn there from given in papers by Prof. Mason, Dr. Becker, and Prof. G. Cook. For ascertaining the effects of the simple forms of anisotropy which manufacture tends to leave in the product, it is assumed that the primary factor in elastic failure is the maximum shearing stress. The application of these deductions to the researches referred to show that, for close correlation, an effect due to volumetric stress must be included, and that the various unexplained difficulties encountered in these researches are then completely clarified and all the results are shown to be in close agreement with the Guest criterion of elastic failure. The completeness of the explanations of difficulties so diverse is good evidence that it and the assumption are correct, and the effects are shown to be such as to merit careful examina...

Absorption of Cosmic Rays

THE Klein-Nishina formula, which is based on the scattering and absorption of X- and -radiation by extra-nuclear electrons, has been widely used in the calculation of the absorption coefficients of high-frequency quanta. But recent experimental work and theoretical deductions have shown that this formula is not applicable to the absorption of -radiation of energy greater than 1.0 × 106 e.v., since for higher energies there is additional absorption due, in the main, to interactions between the radiation and atomic nuclei, these interactions giving rise to electron pairs. This nuclear absorption, which becomes of greater importance as the energy of the quanta increases, and is probably the predominant type of absorption which would occur with any ultra -radiation arising from actions such as the condensation or annihilation of protons and electrons in space, is not accounted for by the Klein-Nishina formula. The latter cannot, therefore, be directly applied to the cosmic ray problem as has been previously assumed, and the wave-lengths of supposed photon components calculated by means of this formula must be inaccurate, since the formula does not take into account the nuclear absorption.

Physiological Stimulus and Response

IN sequence to his books on response in the living and non-living (1902) and plant response (1906), Prof. Chunder Bose has published a third volume on comparative electro-physiology. Prof. Bose has great ingenuity in device of experimental apparatus, fertility in initiating new lines of observation, and a clear style of setting forth his experimental results and theoretical deductions; nevertheless, we feel far from satisfied with his performance. He strives constantly to group every result he obtains under “some property of matter common and persistent in the living and non-living substance,” and to explain by this assumed common underlying property the diverse phenomena of response which occur in metal wires, plant and animal tissues, on mechanical, thermal, or electrical excitation. Comparative Electro-physiology. A Physico-physiological Study. By Prof. J. C. Bose. Pp. xliii + 760. (London: Longmans, Green and Co., 1907.) Price 15s. net.

A Search Into The Nitrate And Nitrite Content Of Witte's "Peptone," With Special Reference To Its Influence On The Demonstration Of The Indol And Cholera Red Reactions

In a previous publication1 I concluded, by rather rough experimental methods and deductions, that the cholera spirillum is not a nitrifying organism and that the successful demonstration of the cholera red reaction in a culture grown in a solution of Witte's peptone depends upon the reduction of a trace of nitrates. I was unaware at the time my experiments were performed that Petri2 and Bleisch3 had already performed quite extensive and conclusive experiments upon this point. The latter worker also pointed out that the presence of an excess of nitrates or nitrites in the medium interfered with the reaction, and that the nitrate content of ordinary broth is so inconstant as to make it valueless for diagnostic purposes. Some peculiar results in testing for indol, during the study of some bacteria from a case of irregular fever, emphasized for me the urgent necessity of adopting methods of preparing and testing media which would indicate the presence or absence of certain chemical constituents influencing such a biochemical test. This led to an investigation into the manner in which nitrates and nitrites may gain an entrance to media, and the influence of such variations on the demonstration of the indol and cholera red reactions. It does not seem to me that the distinct difference between