Quench Factor Research Articles

Cutting the Chain of Command: Specific Inhibitors of Transcription

Cell growth and differentiation are regulated (at least in part) by changes in gene transcription. The cloning and characterization of transcription factors has revealed that these factors coordinately regulate the transcription of specific genetic programs; for example, a number of phorbol ester-induced genes are activated by binding of the transcription factors Fos and Jun to specific DNA sequences. Clearly, inhibition of either the production or function of specific transcription factors would alter complete genetic programs, changing the expression of a great number of genes (analogous to cutting the chain of military command and affecting an entire brigade or division). Our laboratory and others have employed genetic methods to specifically inhibit transcription by two distinct methods: (1) antisense inhibition of the production of transcription factors; and (2) introduction of target DNA sequences to "soak up"or quench transcription factors. In this report, we present data showing that serum-stimulated induction of the c-fos gene may be reduced more than 90% by introduction of target DNA sequences containing the serum response element (SRE); identical amounts of mutant SRE sequences have no effect on gene induction. These studies demonstrate that specific inhibitors of transcription can have significant effects on cellular gene expression. The challenge is to modulate transcriptional programs without deleterious effects on normal cells.

Cooling curve analysis of synthetic quenchants—A historical perspective

Methods for characterizing and interpreting cooling curves are reviewed. Procedures discussed include visual inspection; the calculation of various critical cooling rates, times and temperatures; the integration of areas under the cooling curve or cooling rate curve; the use of the Grossman quench severity factor; and, more recently, the use of quench factor analysis to relate cooling curve behavior to the physical properties of quenched pieces. The objective of this paper is to provide a general review of the approaches to cooling curve analysis published to date. Both strengths and shortcomings of techniques are discussed.

Predicting properties and minimizing residual stress in quenched steel parts

Quenching refers to the process of rapidly cooling metal parts from the austenitizing or solution treating temperature, typically in the range of 845 to 870°C (1550 to 1600°F) for carbon and low alloy steels, for the purpose of forming martensite. Several factors determine whether a particular part can be successfully hardened, including the type, molecular weight, and thermal characteristics of the quenchant, the quenchant use conditions (such as velocity, temperature, and polymer concentration, etc.), section thickness of the part, and the transformation characteristics of the specific alloy being quenched. Successful hardening usually means achieving the required hardness, strength, or toughness while minimizing residual stress, distortion, and the possibility of cracking. Heat removal from parts during quenching can be described in terms of the effective interface heat transfer coefficient. A quenchant must impart a sufficiently high interface heat transfer coefficient to produce a cooling rate that will minimize transformation of austenite to ferrite or pearlite and yield the desired amount of martensite. A quench factorQ has been devised that interrelates quenching variables and transformation kinetics of steel to provide a single number indicating the extent to which a part can be hardened at various locations within the part. The quenchant and the quenchant operating conditions should be selected to provide the proper quench factor while minimizing thermal gradients that can cause distortion or cracking. Cooling curves, interface heat transfer coefficients, quench factors, and thermal gradients produced by a variety of quenchants are presented.

Quench factor analysis of aluminium alloys

Quench factor analysis of aluminium alloys

Quench factor analysis of aluminium alloys

AbstractA model was developed almost 20 years ago which described how precipitation during the quench affected the development of properties of aluminium alloys during subsequent aging treatment. This model was the basis for an analytical process, known as quench factor analysis, that was used to predict the effects of quench path on corrosion characteristics and strength. The purpose of this paper is to provide a theoretical basis for the model and to review how quench factor analysis has been used in solving industrial problems. Several investigators have confirmed that quench factor analysis is an effective predictive method for all quenching conditions save one. The exception is when material has been quenched below the knee of the C-curve and subsequently reheated above the knee before the quench is complete. Applications include the design of quench systems, the development of quench practices which optimize combinations of high strength and low residual stress and distortion, and predictions of the...

Zur Quantitativen Bestimmung von Stickoxiden im Zigarettenrauch mit Hilfe der Chemilumineszenzmethode

A measuring method with a chemiluminescence-analyzer is developed for determining the content of nitrogen oxide in cigarette smoke. This method is suitable for puff/puff analysis. It could be demonstrated that a determination of fresh smoke is necessary as nitrogen oxides react very quickly with other constituents of the vapor phase. Measured values have to be corrected for a quench factor in analogy to the CO2 concentration, as carbon dioxide shows an influence on the measuring sensitivity of the chemiluminescence-analyzer.