Modification of porous polyacrylonitrile membrane

The effects of the modification of polyacrylonitrile ultrafiltration membranes with sodium hydroxide are discussed. The NaOH-induced hydrolysis of nitrile groups on the membrane surface results in membranes with decreasing pore diameter. The average pore diameter changes from 2.6 to 0.6 nm in the progress of hydrolysis. The modified membranes are less prone for protein deposition. Fouling causes a pore diameter reduction of 80% for the untreated and 20% for the modified membranes. Modification results also in the creation of the membranes working in the nanofiltration mode. The unmodified membrane does not reject salt while a membrane immersed in the modification bath is capable of rejecting about 50% of calcium carbonate.     

Evaluation of stress during and after sputter deposition of Cu and Ta films

The stress evolution of magnetron sputtered copper and tantalum films is presented for samples prepared at various sputtering pressures and powers. In-situ stress values were calculated using measurements from a Multi-beam Optical Stress Sensor (MOSS) system, while ex-situ stress values were calculated using measurements from a stylus profilometer. Extensive microstructural and surface analysis were performed by several techniques and related to the stress state of the film. The results demonstrate that during deposition, independent of the adatom mobility, the stress curves are initially compressive at low sputtering pressures, while at the highest sputtering pressure (1.4 Pa) the stress trend is always tensile. Meanwhile, the stress curves after deposition show a tensile trend for both materials at all sputtering pressures.     

Use and Mis-Use of Measurement Scales in City Planning

By developing measurement scales the city planner can promote his long-run interest in integrating urban knowledge and his short-run interest in making valid analyses of specific problems. But the construction of measurement scales is not a random process and must be conducted according to logical rules. Inadequacies in current city planning scales are largely attributable to the lack of adherence to these rules. Housing quality scales, the most common measurement device in city planning, reveal some of the difficulties that lead to deficiencies in our measurement. The outlook is far from gloomy. Experience from other fields in index number construction, the use of scalograms, and factor analysis can Open up many promising avenues for city planning measurement.     

An International Marine-Atmospheric 222Rn Measurement Intercomparison in Bermuda Part I: NIST Calibration and Methodology for Standardized Sample Additions

As part of an international ²²²Rn measurement intercomparison conducted at Bermuda in October 1991, NIST provided standardized sample additions of known, but undisclosed (“blind”) ²²²Rn concentrations that could be related to U.S. national standards. The standardized sample additions were obtained with a calibrated ²²⁶Ra source and a specially-designed manifold used to obtain well-known dilution factors from simultaneous flow-rate measurements. The additions were introduced over sampling periods of several hours (typically 4 h) into a common streamline on a sampling tower used by the participating laboratories for their measurements. The standardized ²²²Rn activity concentrations for the intercomparison ranged from approximately 2.5 Bq · m⁻³ to 35 Bq · m⁻³ (of which the lower end of this range approached concentration levels for ambient Bermudian air) and had overall uncertainties, approximating a 3 standard deviation uncertainty interval, of about 6 % to 13 %. This paper describes the calibration and methodology for the standardized sample additions.     

Mechanical Properties of an Fe‐Based SAM2×5‐630 Metallic Glass Matrix Composite with Tungsten Particle Additions

We present the role of tungsten additions on the mechanical properties of a Fe‐based structural amorphous metal (SAM2×5‐630) containing crystalline tungsten. Matrix cracking by microindentation is inhibited by the addition of tungsten and indicates that tungsten improves the fracture toughness. Response surfaces from nanoindentation arrays indicate that the hardness and modulus of the matrix phase are increased by tungsten additions. Bulk composites with 30 vol% tungsten subjected to 4‐point flexure exhibited brittle fracture behavior and the characteristic strength and Weibull modulus were 165 and 8.7 MPa, respectively. The addition of tungsten did not cause devitrification of the matrix phase.