ESCA study of fractional monolayer quantities of chemisorbed gases on tungsten

X-ray photoelectron spectroscopy (ESCA) has been used in a study of CO and O₂ chemisorbed on a polycrystalline tungsten sample. Working under ultra-high vacuum conditions, the surface was cleaned and then covered with known monolayer and fractional monolayer quantities of adsorbed CO and O₂. The O(ls) and C(ls) spectral features were detected, and the influence of an adsorbed layer on the tungsten spectral features was determined. A chemical shift of 3.4 eV in the O(ls) line from chemisorbed CO is related to the different modes of bonding of CO to tungsten. A model calculation of the photoelectron yields expected from an adsorbed monolayer is in good agreement with the experimental results.     

Comparison of high-performance liquid chromatography electrochemical detectors for the determination of aporphines,catecholamines and melatonin

A Bioanalytical Systems detector showed a greater sensitivity for low-level determinations of apomorphine, norepinephrine, epinephrine, dopamine, and melatonin compared to a Brinkmann Instruments system. Modifications of the Bioanalytical Systems flow cell, which have been developed in our laboratories, increase the sensitivity toward certain catecholic compounds, generally decrease baseline noise, and allow for serial coupling of detectors.²     

Heat transfer to magnetohydrodynamic flow in a flat duct

Zusammenfassung Die Untersuchung befasst sich mit der Wärmeübertragung von den Wänden eines flachwandigen Kanals auf eine elektrisch leitende Flüssigkeit bei erzwungener Laminarströmung und in Gegenwart eines quergerichteten Magnetfeldes. Betrachtet wird der Fall konstanter Wandtemperatur mit variierender innerer Wärmeentwicklung durch viskose und elektrische Energiedissipation. Die massgebende Differentialgleichung wird durch eine Differenzengleichung ersetzt und mit der elektronischen Rechenmaschine gelöst. Als Resultat wird die Nusseltzahl angegeben, für die Prandtlzahl 1, die Hartmannzahlen 0, 4, 10 und die Graetzzahlen von 10 bis 10 000, wobei die Kennzahlen für Zähigkeit und elektrische Feldstärke als Parameter auftreten.     

Results of a joint auger/ESCA round robin sponsored by astm commitree E-42 on surface analysis: Part I. Esca results

We report results of a round robin involving binding-energy (BE) and relative-intensity measurements on high-purity samples of gold and copper by X-rayWe have conducted an extensive round robin involving ESCA or XPS measurements on high-purity samples of Ni, Au, and Cu. The Ni sample was used to estabThis round robin had three principal objectives. First, it was intended to assess the overall accuracy of BE and intensity measurements in XPS measuremSecond, it was intended to establish an empirical intensity calibration of one type of XPS instrument versus another from the reported intensity ratiosThird, it was desired to determine the peak position and peak shape for the carbon 1s photoelectron line originating for “adventitious” carbonaWe have made an extensive analysis of trends in the BE and intensity data. We have computed deviations of individual BE measurements from the median vaThe two types of plots just described based on BE and intensity data can be regarded as “response functions” that describe the performance of indivWe have invoked Occam's Razor to distinguish instruments with response functions which vary monotonically with electron energy from those instruments wThe reported spreads in BE and relative-intensity data reported here indicate that improved calibration and operating procedures are required for XPS m     

Submillimeter-wave heterodyne spectroscopy with a compact solid state radiometer

A compact, solid state submillimeter-wave heterodyne radiometer has been developed and was used to measure spectral characteristics of a water vapor jet in a space simulation chamber. Features of the 557 GHz water vapor line profile were observed in significantly greater detail than in previous experiments through an increased sensitivity and improved frequency resolution (600 kHz). The local oscillator of the radiometer consisted of a frequency multiplication chain which was driven by an InP Gunn oscillator at 92.6 GHz, and which contained a frequency tripler and harmonic mixer in cascade. The front end of the receiver had a noise temperature of 4500 K (DSB) at 555 GHz, consumed 3 W and weighed 3 kg. This advance in technology is particularly relevant to submillimeter-wave radiometry from a space-based platform.     

A correlation between the order parameters of rigid solutes dissolved in two nematic solvents and in a mixture of them

The orientational data of four rigid solutes dissolved in the nematic solvents ZLI1132, EBBA and in a 55wt% ZLI1132 + EBBA mixture have been obtained from proton NMR spectra at different temperatures and used to find a relationship between the solute order in the two nematics and in their mixture. A crossed comparison of the data shows that a simple linear relation, where the normalized weights of the combination are coincident with the molar fractions of ZLI1132 and EBBA in the mixture, gives excellent agreement independently of the solutes and temperatures. Consideration is given to the possibility of a generalization of the results to any mixture of two nematics.     

Mutually describing multisets and integer partitions

To each finite multiset $A$, with underlying set $S\left(A\right)$, we associate a new multiset $d\left(A\right)$, obtained by adjoining to $S\left(A\right)$ the multiplicities of its elements in $A$. We study the orbits of the map $d$ under iteration, and show that if $A$ consists of nonnegative integers, then its orbit under $d$ converges to a cycle. Moreover, we prove that all cycles of $d$ over $\mathbb{Z}$ are of length at most $3$, and we completely determine them. This amounts to finding all systems of mutually describing multisets. In the process, we are led to introduce and study a related discrete dynamical system on the set of integer partitions of $n$ for each $n\ge 1$.     

Ethnic Preferences and Residential Segregation: Theoretical Explorations Beyond Detroit

We are strongly supportive of Fossett's theoretical approach and modeling methodology, which uses computational methods to perform thought experiments that generate compelling insights into the enigma of persistent residential segregation in the U.S. We also agree with his theoretical results, which challenge the prevailing view among demographers that institutional discrimination is the essential cause. However, we think he did not go far enough. Fossett limited his analysis to a narrow region of the parameter space that corresponded to conditions observed in one city at one time. This precludes generalization to other times and places and exploration of theoretically motivated “what if” scenarios that trespass beyond the Detroit city limits. When we extended the parameter space, we noticed two interesting results. First, Fossett's “paradox of weak minority preferences” requires qualification. Disproportionate in-group preferences among minorities are indeed segregation-promoting, not integration-promoting, but they generally have less impact on segregation than the in-group preferences of the majority. Second, not only are exclusionary practices and institutional discrimination not necessary for segregation (as Fossett demonstrates), we show that in certain regions of the parameter space they are not even sufficient.