The v10=1 Level of Propyne, H3CCCH, and Its Interactions with v9=1 and v10=2

Almost 300 new rotational transitions within the fundamental vibrational level v₁₀=1 of propyne have been measured in selected regions between 495 and 925 GHz spanning the quantum numbers 28≤J≤54 and 0≤K≤16. The accuracies are mostly between 10 and 20 kHz. In addition, the J″=4 and 5 transitions near 85 and 103 GHz have been remeasured. Simultaneous analyses with refined rovibrational data have been performed, showing that even this lowest and seemingly isolated vibrational level needs a global treatment when high K transitions are involved. The global model with the v₁₀=1 level coupled to the next higher cluster of levels, v₁₀=2/v₉=1, by Fermi and Coriolis resonances is necessary for a quantitative reproduction of both the rovibrational and rotational data within their experimental uncertainties. Included are also improved ground state spectroscopic parameters from a fit of previous pure rotational data and Δk=3 ground state combination loops as well as additional data obtained in course of the present study.     

Rovibrational and Rotational Spectroscopy of Levels of Propyne around 1000 cm(-1)

Four vibrational levels in the energy region around 1000 cm(-1) were studied. These were the v(5)=1 and v(8)=1 fundamental levels, both components of the v(9)=v(10)=1 combination level (l(9)=l(10)=+/-1 and l(9)=-l(10)=+/-1), and both components of the v(10)=3 overtone level (l(10)=+/-1 and +/-3). New FTIR spectra with a synchrotron radiation source were recorded in the region of the "superhot" v(10)=3<--2 bands, which made possible the first assignment of levels of the v(10)=3(+/-1) sublevel. More than 330 new rotational transitions in the combination and overtone levels were measured by millimeter-wave spectroscopy betwen 50 and 360 GHz. The new data were analyzed simultaneously together with the previously assigned rovibrational data for the fundamental and combination levels and rotational data for the fundamental levels using a global model with all anharmonic, Coriolis, l-type, and alpha-resonances. Significant improvement of data reproduction and very good consistency with the Hamiltonian parameters of the lower vibrational levels v(9)=1 and v(10)=1, 2 were achieved. A strong dependence of the A(v) constant on the l(10) quantum number is found for propyne: this is shown to be characteristic of skeleton C-C identical withC or C-C identical withN bending modes in H(3)CCCH, H(3)CCN, and their fully deuterated species. Copyright 2001 Academic Press.     

Random replicators with high-order interactions

We use tools of the equilibrium statistical mechanics of disordered systems to study analytically the statistical properties of an ecosystem composed of N species interacting via random mutual interactions, as well as via deterministic self-interactions of order p>/=2. We show that the main effect of increasing the order of the interactions among the species is to make the system less competitive, in the sense that the fraction of extinct species is greatly reduced. In addition, we find that for p>2 there is a threshold value which gives a lower bound to the concentration of the surviving species, preventing then the existence of rare species and, consequently, increasing the robustness of the ecosystem to external perturbations.     

Analysis of the ν1 band of CH3I

The rotational structure of the infrared band ν₁ of CH₃I has been studied at a resolution of 0.04 cm^?1 using a grating spectrometer. In the analysis including 470 lines a resonance, explained to be caused by ν₂ + 2ν₆^±2, has been taken into account. The molecular constants derived include, e.g., α₁^A = 0.051129(14) cm^?1 and α₁^B = 0.0983(9) × 10^?3 cm^?1.     

The high-resolution infrared spectrum of Si2H6: rotation–torsion analysis of the ν5 and ν7 fundamentals,and torsional splittings in the degenerate vibrational states

The infrared active ν₇ and ν₅ fundamentals of disilane, coupled by an x,y Coriolis interaction, have been analysed on a Fourier transform spectrum between 2120 and 2225?cm^?1, at the Doppler limited spectral resolution. A Fermi resonance with 2ν ₂?+?ν₉ affects the Δ K?=?1 side of ν₇, and both ν₇ and ν₅ show the effects of several additional localized perturbations. Line splittings in the ν₅ transitions are not observed, showing that the torsional splitting in the ν₅ excited state and in the vibrational ground state are almost equal. The intrinsic torsional splitting of ν₇ is found to be smaller than in the ground vibrational state by 0.0085?cm^?1. This splitting value and those found for the other two infrared active degenerate fundamentals, ν₈ and ν₉, follow the trend expected from our theoretical predictions. Exploratory numerical calculations show that the decrease of the torsional splittings, observed in the fundamental degenerate vibrational states of disilane, can actually be accounted for by the head–tail and torsional Coriolis coupling of all the degenerate vibrational fundamentals, in several torsional states.     

Surfactant-aided size-exclusion chromatography for the purification of immunoglobulin G

In the production of monoclonal antibodies, separate chains of the antibody are often present in the product mixture as well as other contaminating proteins. These fragments should be removed from the whole antibodies. This paper shows the purification of monoclonal immunoglobulin G (IgG) from its heavy chain contaminant. The heavy chain fragment is simulated experimentally using bovine serum albumin (BSA), which has approximately the same molecular weight. The purification is performed using traditional size-exclusion chromatography (SEC) and using surfactant-aided SEC (SASEC), testing two different surfactants (C(12)E(23) and Tween20) and two different gels (Sephacryl S200HR and Sephacryl S300 HR). Pulse experiments show that with SASEC both BSA and IgG are more distributed towards the solid phase than compared to using SEC. This effect is larger on IgG, the largest component than on BSA. As a consequence, azeotropes will be formed at a specific surfactant concentration. Above this concentration the selectivity is reversed and increased to values higher than obtained with conventional SEC. At 7.5% (w/w) of C(12)E(23), BSA actually elutes before IgG. These experiments further show that when using SASEC larger productivity, higher yields and lower solvent consumption can be achieved without loss of purity of IgG when compared to conventional SEC. Mathematical simulation of the separation of BSA and IgG using simulated moving bed (SMB) chromatography indicates a large increase in productivity when applying a surfactant gradient in SASEC SMB compared to conventional isocratic SEC-SMB. Furthermore, solvent consumption reductions with a factor 15 prove possible as well as concentrating the IgG by a factor 2.     

Micellar gradients in size-exclusion simulated moving bed chromatography

The selectivity of size-exclusion chromatography (SEC) can be modified by adding non-ionic micelles to the mobile phase. Surfactant-aided size-exclusion chromatography (SASEC) can therefore very well be performed in a gradient mode on an SMB, as is reported in this paper. A method has been developed for correctly positioning a micellar gradient over an SMB. The method is applied for size-exclusion chromatography with the non-ionic surfactant C12E23 as gradient forming solute, and demonstrated by applying it to a relevant chromatographic protein separation problem.     

High-Resolution Far-Infrared Torsional Spectrum of CH3SiD3 Using a Synchrotron Source

The far-infrared torsional spectrum of CH₃SiD₃ has been measured in a continuing effort to quantify the coupling between the small amplitude vibrations and the large amplitude internal rotation of the methyl group in symmetric tops. It is hoped that this will help in understanding the role of torsional motion in intramolecular vibrational relaxation. The spectrum was recorded with the Bruker IFS120 HR interferometer that is coupled to the MAX-I synchrotron radiation source in Lund, Sweden. High-resolution (0.002 cm⁻¹) spectra of the very weak torsional overtone 2ν₆ and hot band 3ν₆−ν₆ were recorded between 230 and 350 cm⁻¹. A total of 1413 frequencies in these two bands were assigned. In a separate experiment, a high-resolution (0.00125 cm⁻¹) spectrum of the lowest-lying degenerate fundamental band ν₁₂ was measured between 360 and 480 cm⁻¹, and 3263 frequencies belonging to this band were assigned. This spectrum was recorded with the Bruker IFS120 HR interferometer located at the University of Oulu, Finland. The frequencies from the aforementioned three bands and the data from the recent molecular beam measurements reported by Ozier and Meerts (J. Chem. Phys.109, 4823 (1998)) were analyzed using a model which considered three interacting torsional stacks: one for the ground vibrational state and two for v₁₂=1. A fit to within the experimental error was obtained by varying 36 molecular parameters. Several interstack coupling constants have been determined. A comparison of the leading parameters between CH₃SiD₃ and CH₃SiH₃ is presented.     

Vibration-rotation bands of CO2 and OCS in the region 540–890 cm−1

The regions of the ν₂ band of CO₂ and the ν₁ band of OCS have been simultaneously measured by the Fourier transform spectrometer (1, 2). The resolution achieved was now about 0.0045 cm^?1. A total of eight “hot” bands of ¹²C¹⁶O₂ and ¹⁶O¹²C³²S and the fundamental bands ν₂ of ¹³C¹⁶O₂ and ν₁ of ¹⁶O¹²C³⁴S have been reported.