A Convenient,Versatile and Inexpensive Thermostat Jacket for Spectrophotometer Cells.

Abstract

Directory of Biotechnology Companies, John H. Sterling, ed., Mary Ann Liebert, Inc., New York, 1999, xl + 692 pp., $525.00.

2-D Proteome Analysis Protocols, A. J. Link, ed., Humana Press, Totowa, NJ, 1999, 601 pp., $89.50.     

A Low Cost Lock-In Amplifier for Ac Polarography

ABSTRACT

The electronics, construction and use of a low cost lock-in amplifier suitable for AC polarography are described. The device operates from 10 Hz to 10 kHz in 1,2,5 multiples of frequency. Components for the unit cost about $150.     

A New Circuit for Current Reversal Chronopotentiometry

Electrochemical techniques are being used today to measure the kinetics of homogeneous chemical reactions [1, 2]. The value of one of the techniques, current reversal chronopotentiometry (CRC), has been demonstrated with the study of several chemical systems [3, 4]. Recently, a circuit designed for cyclic chronopotentiometry (CC) utilizing tube-type operational amplifiers was published [5]. This circuit of course is also suitable for CRC and in fact has been used to elucidate the mechanism of the loss of water from p-hydroxyaminophenol [6]. The main disadvantage of this circuit is that the experiment is initiated by unshorting the electrochemical cell. Undesirable galvanic reactions are possible at the working electrode when it is shorted to the unpoised auxiliary electrode [7]. This has been circumvented by making the auxiliary electrode a large area reference electrode.

However, this can be inconvenient and, moreover, is disastrous if appreciable reactions can proceed at zero volts vs. the particular reference electrode used.     

An Inexpensive Real-Time Digital Integrator Based on A Sym-1 Microcomputer for Use with High Pressure Liquid Chromatography

ABSTRACT

Details of a data acquisition system controlled by a SYM-1 single-board microcomputer are presented. The total cost of constructing the system was approximately $300. The system's variable gain amplifier coupled with a 10 bit analog-to-digital converter can be used to interface the SYM-1 to many laboratory instruments. In this report the data system is used to digitally integrate sample peaks from a high pressure liquid chromatograph.     

Book Review: Flow Measurement Handbook (Second Edition) Roger C. Baker

A review is given of the Second Edition of Professor Roger C. Baker's Flow Measurement Handbook, published in 2016 by Cambridge University Press.     

Compact pulse forming line using barium titanate ceramic material

Ceramic material has very high relative permittivity, so compact pulse forming line can be made using these materials. Barium titanate (BaTiO(3)) has a relative permittivity of 1200 so it is used for making compact pulse forming line (PFL). Barium titanate also has piezoelectric effects so it cracks during high voltages discharges due to stresses developed in it. Barium titanate is mixed with rubber which absorbs the piezoelectric stresses when the PFL is charged and regain its original shape after the discharge. A composite mixture of barium titanate with the neoprene rubber is prepared. The relative permittivity of the composite mixture is measured to be 85. A coaxial pulse forming line of inner diameter 120 mm, outer diameter 240 mm, and length 350 mm is made and the composite mixture of barium titanate and neoprene rubber is filled between the inner and outer cylinders. The PFL is charged up to 120 kV and discharged into 5 Ω load. The voltage pulse of 70 kV, 21 ns is measured across the load. The conventional PFL is made up of oil or plastics dielectrics with the relative permittivity of 2-10 [D. R. Linde, CRC Handbook of Chemistry and Physics, 90th ed. (CRC, 2009); Xia et al., Rev. Sci. Instrum. 79, 086113 (2008); Yang et al., Rev. Sci. Instrum. 81, 43303 (2010)], which increases the length of PFL. We have reported the compactness in length achieved due to increase in relative permittivity of composite mixture by adding barium titanate in neoprene rubber.     

Morphology of Surface Integrity as Effect of Cold Forging of Aluminum Alloy

Aluminum and its alloys represent a common raw material for components released through a cold machining routine (i.e., forging, cold heading, and rolling processes). They offer easy manufacturing and high plastic strength, together with light weight, long life span, and easy recycling and are heavily used in the transport industry (P. M. G. P. Moreira, et al. (1 Moreira, P. M. G. P., de Jesus, A. M. P., Ribeiro, A. S., and de Castro, P. M. S. T. (2008), “Fatigue Crack Growth in Friction Stir Welds of 6082-T6 and 6061-T6 Aluminium Alloys: A Comparison,” Theoretical and Applied Fracture Mechanics, 50, pp 81–91.[Crossref], [Web of Science ®] , [Google Scholar]), Theoretical and Applied Fracture Mechanics, 50, pp 81–91, 2008; H. Yoshimura and K. Tanaka (2 Yoshimura, H., and Tanaka, K. (2000), “Precision Forging of Aluminum and Steel,” Journal of Materials Processing Technology, 98, pp 196–204.[Crossref], [Web of Science ®] , [Google Scholar]), Journal of Materials Processing Technology, 98, pp 196–204, 2000). However, during processing, the sample–tool interfaces can generate sticking mechanisms that result in an increase in friction values and high wear rates, leading to irreversible damage to the workpiece surface. The surface morphology provides characteristics that allow detection of the damage amplitude. The hard contact between asperities causes nucleation and the formation of adhesive wear. The normal load and lubrication conditions may further affect the quantity of wear elements (A. Hase and H. Mishina (3 Hase, A., and Mishina, H. (2009), “Wear Elements Generated in the Elementary Process of Wear,” Tribology International, 42, pp 1684–1690.[Crossref], [Web of Science ®] , [Google Scholar]), Tribology International, 42, pp 1684–1690, 2009). Optical nondestructive observations permit the detection of the quantity of wear elements as per material transfer from one side (specimen surface) to the other side (contactor surface).

This article presents the mechanisms of the adhesive layer and material transfer that are directly proportional to the new roughness stature. A robust finite element method analysis was embedded to establish a relationship between time, plastic deformation, friction coefficients, and surface defects.     

Tribological Property of Selective Laser Melting–Processed 316L Stainless Steel against Filled PEEK under Water Lubrication

Abstract

As a 3D printing technology, selective laser melting has remarkable advantages such as high processing flexibility, high material utilization, and short production cycle. The applications of selective laser melting technology in industry have become quite extensive. There are many tribological studies on selective laser melting materials, but few based on water lubrication (Zhu, et al., Journal of Zhejiang University-Science A, 19(2), pp 95–110). In this article, the tribological properties of 316L stainless steel processed by selective laser melting and traditional methods have been studied under water lubrication. Polyether ether ketone (PEEK) filled with carbon fiber (CF)/polytetrafluoroethylene (PTFE)/graphite was selected as the counterpart. 316L stainless steel and PEEK are a tribopair commonly used in water hydraulics. This study is of great significance to the application of selective laser melting material of tribopairs in water hydraulics. Friction and wear tests were carried out on a pin-on-disc contact test apparatus under different operating conditions. The friction coefficient, specific wear coefficient, scanning electron microscopy (SEM) of the worn surface, and energy-dispersive spectroscopy (EDS) of the surface adhesions of the three tribopairs were measured and compared. The results revealed that the friction coefficient of the selective laser melting (SLM) 316L stainless steel was significantly higher than that of traditionally processed (TP) 316L stainless steel, which might be caused by the pores on the surface of SLM 316L stainless steel. Adhesion and cutting on the surface of SLM 316L stainless steel were also more serious, resulting in a higher specific wear coefficient of its counterpart PEEK composite compared to PEEK composite against TP 316L stainless steel.     

INFLUENCE OF MACHINING ON FRICTION AND WEAR OF LUBRICATED CERAMICS IN SLIP-ROLLING CONTACTS

Abstract

The slip-rolling friction and wear tests were performed in a twin disc tribometer of the Amsler-type at a Hertzian pressure of 3 GPa over 2 million revolutions. Paraffinic oil with no additives was used as lubricant. The ceramics were machined with different processes, resulting in different surface roughness (i.e., rough and fine honed, rough and fine ground, rough and fine lapped, and rough and fine polished). Ceramic materials like HIP-Si₃N₄, S-SiC, HIP-ZrO₂, and GPS-Si₃N₄-TiN were investigated as self-mated couples. This paper summarizes the results. Si₃N₄, Si₃N₄-TiN, and ZrO₂ generally exhibit a small wear coefficient in the range of 10^?9 mm³/Nm in paraffinic oil and their wear coefficients correlate with the initial surface roughness and the material removal rate. The lowest wear coefficients were exhibited by ZrO₂- With a reduction of the Hertzian pressure to 1.5 GPa, S-SiC exhibits the same tribological behavior as the other ceramics.     

A Low-Shear Titration Viscometer Suitable for Investigation of DNA and Other Polymers

SUMMARY

The viscosity of linear high-molecular-weight substances should be measured at sufficiently low shear gradients, e.g., with the aid of the ingenious Zimm-Crothers rotating-cylinder viscometer [1]. To investigate properties of nucleic acids or other polymers and their interaction with substances such as certain ions, dyes, etc., it proves useful to follow changes in polymer viscosity with increasing concentrations of the added interacting substance.     

A Modified Microcomputer-Controlled Proportioning Valve Instrument for Programmable Dilution of Gases

Abstract

A commercial VG-400 gas dilution apparatus from Microsensor Systems, Inc. was modified with an updated microcomputer, revised software, electronic mass flow controllers, and a needle valve pressure restrictor in order to enhance its performance. The instrument's maximum linear dilution factor has been extended to 330,000 from the previous practical limit of 100,000 while its dilution accuracy, precision, resolution, and stability have been increased. The modification also decreased the fluctuations in the instrument's output concentrations to ≤ 1.5%.     

The expressional level of tankyrase-1 gene and its regulation in colorectal cancer in a Saudi population

Tankyrase1 plays an essential role in cancer progression by regulating telomere length. The study aimed to determine expression of TNKS1 and its regulation in colorectal cancer (CRC) in 20 samples from Saudi patients. mRNA expression of TNKS1 in CRC and paired normal tissues was measured by qRT-PCR. Epigenetic modification of TNKS1 promoter was determined by methylation-specific PCR while somatic mutation was analyzed by Sanger sequencing in exon 10 of the gene. All cancerous and normal tissues expressed TNKS1, but level of expression in CRC tissues was significantly associated with tumor stage though no other parameters; age, gender, and tumor location, showed any correlation. Expression of TNKS1 was markedly higher in earlier (I, II) than later (III, IV) stages of CRC development. Both cancerous and healthy tissues had unmethylated promoter. Sanger sequencing of exon 10 masked any somatic mutation in the samples. Our findings suggest that up-regulation of TNKS1 was inversely correlated with cancer progression in CRC, indicating that TNKS1 participates in the initiation of CRC by stabilizing telomere length in the first phase of cancer progression. Mechanisms other than TNKS1 might play a role in malignant tumor progression and telomere maintenance in the late stages of CRC.     

Numerical Study of the Effect of Tribofilm Kinetics and Its Hardness on the Roughness Evolution of the Substrate in Boundary Lubrication Regime

Abstract

A tribochemical modeling framework that considers the growth of a tribofilm on the contacting surfaces has been used in this work. The model couples a fast contact mechanics model with the thermodynamics of interfaces and captures the growth of the tribofilm on the asperities. The model was shown to be able to capture the dynamics of a tribosystem and the evolution of surface topography. The model considers the effect of plastic deformation and wear in modifying the surface geometries. In a recent work by the authors (Ghanbarzadeh et al., Wear, 362–363, 2016), the same numerical model was validated against experiments in a micropitting rig (MPR) and the wear, topography, and tribofilm thickness results were compared. In this work, validation of the model is presented and the effect of tribofilm kinetics and its hardness have been numerically studied to assess the evolution of surface roughness in a rolling sliding contact. Results suggest that the kinetics of the tribofilm growth significantly influence the roughness evolution with higher kinetics resulting in a rougher interface. Similarly, the tribofilm hardness affects the roughness evolution and is more influential in the later stages of roughness evolution.     

Development of a Discrimination Set-Up

Abstract

In the present work, a discrimination set-up was developed to obtain a pure photopeak. To evaluate the experimental performance of the set-up, the spectrometer system was tested on the photopeak of ¹³⁷Cs. The discrimination of the photopeak from the superimposed non-photopeak radiations, such as Compton effect, background, scattering, backscattering, etc., was achieved adequately.     

An Application of a Timing Measurement: Separation of a Photo Peak

Abstract

A discrimination set‐up was developed to obtain a neat photo peak. To evaluate the experimental performance of the set‐up, the spectrometer system was tested on the photo peak of ¹³⁷Cs. The separation of the photo peak from the non‐photo peak radiations such as Compton effect, annihilation, background, scattering, etc., was achieved adequately.     

A Digital Integrator with a Memory

ABSTRACT

An inexpensive (～ $120), versatile, easily constructed digital integrator is described. Linearity is better than 1% for voltages of 0.1 to 15 V inputs. Input uncertainties are ≤ ～ 200 μ V. Input impedance is ～ 0.5 M. Integrals spanning at least a 1000:1 range can be read with 1% or better accuracy without varying the gain. Sensitivity is 5 count/V-sec, but higher or lower sensitivities are available by changing component values. A memory permits the integral at a particular instant to be locked into the display without any effect on the continuing integration. The reset, store, and track controls are transistor transistor logic compatible and may be operated by external circuitry for added versatility.     

Optimization of Pocket Geometry for Friction Reduction in Piston–Liner Contacts

It has recently been shown that rectangular surface pockets are effective in reducing friction in a piston–liner type contact, providing that they are oriented with their long axis transverse to the sliding direction so that entrained features fit completely within the contact area (Vl?descu, et al., Tribology International, 82, 28–42, 2015; Vl?descu, et al., Tribology International, 115, 140–153, 2017). The aim of the current study was to identify the optimal geometric parameters of theses rectangular features. To do this, a friction rig that simulated a piston–liner contact under highly controlled conditions was used to test a series of textured specimens with pockets of different depth, breadth and density. Each of these geometric parameters was varied and tested independently, while keeping the other two constant. Experimental conditions were set in order to place the contact in different lubrication regimes.

Results were analyzed to determine a set of criteria for the optimum pocket geometry; however, this was shown to change depending on the test conditions and should therefore be adjusted depending on the position along the stroke. Specifically, at low speed when the contact is operating under boundary lubrication, pockets should be deep, wide, and densely spaced. This confirms recent findings, which suggested that, in this regime, pocket volume is often a more critical parameter than depth, width, or spacing individually. Conversely, under mixed lubrication toward the transition to the full film regime, pockets should be narrow and sparsely spaced. These results also explain the difficulties encountered in several previous studies that attempted to define a single optimum pocket geometry.

Finally, the impact of pocket position relative to reversal was assessed for various lubrication conditions. This revealed how pockets should be placed close to, but not directly at, top and bottom dead center to provide a beneficial squeeze film, which is present at reversal.     

Automatic Control of the Arc Gap in DC Arc-Emission Spectrographic Analysis

SUMMARY

In emission spectrograpliy the result of a determination is read from the “analytical curve,” i.e., the working curve, which shows the ratio of the intensity of the analytical line chosen for the element to that of an internal standard line as a function of the concentration of the element. It is a well-known fact [1] that in actual practice such an analytical curve may shift; i.e., when the intensity ratios necessary for drawing the curve are redetermined after a certain period, their values deviate more from the original data than can be expected from the repeatability of the method.