Improved Characterization Methods Research Articles

Progress in Understanding the Fatigue Behavior of Ti Alloys

Titanium (Ti) alloys are used in critical, fatigue limited applications in aircraft and aircraft engines. Current design practices are, of necessity, conservative in order to minimize risk of unexpected failures. Among the sources of this conservatism are the inherent variations in the number of loading cycles the materials can withstand prior to fatigue crack initiation, the uncertainty in crack propagation lifetime prediction and the need to set safe minimum component life values. While the stochastic nature of fatigue is well-known, improved characterization methods have begun to provide a better understanding of the crack initiation process. This paper describes recent work designed to provide an improved understanding of the relationship between thermomechanical processing history, microstructure, texture and the fatigue behavior of α+β Ti alloys. Due to length limitations, the paper focuses on two important aspects of fatigue life variation: the effects of microstructural discontinuities on fatigue and the role of facet formation during crack initiation and the early stages of fatigue crack growth.

An improved method for characterization of the mutation associated to porcine stress syndrome by PCR amplification followed by restriction analysis

A mutation in the gene coding for the ryanodine receptor 1 (RYR1), also known as halothane (hal) gene or swine stress gene, is associated to the porcine stress syndrome (PSS). Detection of the mutation is normally accomplished by PCR amplification of an 81bp fragment of the hal gene, followed by digestion with the HhaI restriction endonuclease. Wild-type allele (N) is cut in two fragments, whereas the mutant allele (n) is not digested by the restriction enzyme. Electrophoresis of the digested DNA on agarose gel and ethidium bromide staining allows the reading of the result. The correct interpretation is difficult due to the small size of the DNA fragments. In this study we designed a new set of primers for amplification of a 144bp fragment that facilitates the reading of the result. In addition, we optimized the PCR reaction to allow amplification from a single hair bulb, added directly into the PCR mix without previous treatment. This improved method was used to genotype 165 sows and boars used in a breeding program. Forty-nine percent of the animals had the NN genotype, whereas 50% were Nn and only 1% was nn.

Group Type Analysis of Asphalt by Column Liquid Chromatography

An improved analysis method for characterization of asphalt was established. The method is based on column chromatography technique. The asphalts were separated into four groups: saturates, aromatics, resins, and asphaltenes, quantitatively. About 0.1 g of sample was required in each analysis. About 20 mL of n-heptanes was used to separate out saturates first. Then about 35 mL of n-heptanes/dichloromethane (1/2.5, v/v) mixture was used to separate out aromatics. About 30 mL of dichloromethane/tetrahydrofuran (1/3, v/v) mixture was used to separate out resin. The quality of the separation was confirmed by infrared spectra (IR) and 1H NMR analysis. The model compounds, tetracosan for saturates, dibenz(ah)anthracen for aromatics, and acetanilide for resins were used for verification. The IR and 1H NMR analysis of the prepared fractions from the column liquid chromatography were in good agreement that of pure reagents.

Glycoform characterization of erythropoietin combining glycan and intact protein analysis by capillary electrophoresis – electrospray – time‐of‐flight mass spectrometry

Glycosylation of recombinant human erythropoietin (rHuEPO) is a post-translational process that alters biological activity, solubility and lifetime of the glycoprotein in blood, and strongly depends on the type of cell and the cell culture conditions. A fast and simple method providing extensive carbohydrate information about the glycans present in rHuEPO and other glycoproteins is needed in order to improve current methods in drug development or product quality control. Here, an improved method for intact rHuEPO glycoform characterization by CZE-ESI-TOF MS has been developed using a novel capillary coating and compared to a previous study. Both methods allow a fast separation in combination with accurate mass characterization of the single protein isoforms. The novel dynamic coating provides a separation at an EOF close to zero, enabling better separation. This results in an improved mass spectrometric resolution and the detection of minor isoforms. In order to assign an unequivocal carbohydrate composition to every intact glycoform, a CZE-ESI-MS separation method for enzymatically released underivatized N-glycans has been developed. The TOF MS allows the correct identification of the glycans due to its high mass accuracy and resolution. Therefore, glycan modifications such as acetylation, oxidation, sulfation and even the exchange of OH by NH(2) are successfully characterized. Information of the protein-backbone molecular mass has been combined with results from peptide analysis (revealing information about O-glycosylation) and from the glycan analysis, including the detection of as yet undescribed glycans containing four antennae and five sialic acids. This allows an unequivocal assignment of an overall glycosylation composition to the molecular masses obtained for the intact rHuEPO glycoforms.

Comparison of atomic force acoustic microscopy and dynamic nanoindentation methods for compliant polymer systems

Nanomechanical characterization of soft materials such as polymers and polymer composites represents a unique and challenging research topic of current interest. In this presentation, two characterization methods are compared directly using a set of model PDMS polymer systems. Experiments were conducted using both nanoindentation and atomic force acoustic microscopy (AFAM) to determine the dynamic mechanical properties. The experiments were conducted to determine reduced elastic modulus E* via AFAM measurement and storage modulus E via nanoindentation. The AFAM analysis was done using both a Hertzian contact model and a flat punch model. While the two methods showed marginal agreement, the resulting AFAM moduli were dependent on the model used in the analysis. Further investigation is needed to improve the accuracy of these measurements. In addition, further modeling is needed to improve the understanding of the tip‐sample interaction in such systems. The results are anticipated to lead to the development of improved characterization methods for compliant materials. [Work supported by ARL.]

Improved characterization methods for unipolar directly bonded semiconductor junctions

Improved methods for electrical characterization of unipolar semiconductor junctions with interface states and interfacial-barrier punctures at the junction plane are described. Compared to the previous description of the methods, two regular procedures for making allowance for the leakage current through punctures are reported. With these procedures, measurements of the quasi-static current–voltage characteristic of a junction, together with its high-frequency (h.f.) capacitance and conductance, permit determination of the fraction of the total direct current that flows through punctures, the spreading resistance of the system of punctures, the doping profile in the vicinity of the interface, and the energy distribution of interface states on the areal part of the junction with the potential barrier. Results yielded by the methods in their full formulation for real p-Si/p-Si directly bonded structures are reported.

Demonstration of Symmetry Control of Infrared Heated Deuterium Layers in Hohlraums

Infrared smoothed deuterium ice layers inside capsules have been successfully demonstrated for capsules inside cylindrical hohlraums. Improved characterization methods and infrared illumination enables low mode control in both the axial and azimuthal directions. We demonstrate control of the first two axial modes and first azimuthal mode using IR pointing. We demonstrate ice layers with axial P1 amplitude less than 1 μm, and a reduction in P2 amplitude from 20% to 8% of the ice thickness. Results of these experiments will be used to derive accuracy requirements for an infrared heating system for ice layers in hohlraums on NIF.

Distribution of Interface States in MOS Systems Extracted by the Subthreshold Current in MOSFETs under Optical Illumination

In this paper, we propose a novel subthreshold current method using the optical current-voltage (I-V) curve for interface-state extraction. The new method is simpler and more accurate than the conventional interface-state extraction methods in MOSFETs. Based on the photonic highfrequency capacitance-voltage response of MOS capacitors and the conventional subthreshold current method, an improved characterization method is reported for the analysis of interface-states in MOS systems. An optical source with a photonic energy Eph = 0.943 eV (wavelength = 1314.5 nm) is employed for optical subthreshold current characterization of interface-states distributed in the photo-responsive energy-band. By using the optical subthreshold current and dark subthreshold current, we obtained a U-shaped distribution for the interface-trap density (Dit) in N-type and P-type MOSFETs.

Splanchnic vessels

Splanchnic vessels

Improved determination of matrix compostion of Hg1−xCdxTe by SIMS

Results are presented to show an improved method for composition characterization of HgCdTe heterostructure using secondary ion mass spectroscopy. This method utilizes the molecular ions CsM+ rather than M± ions. The advantage is that the molecular CsM+ ion yield, unlike the atomic M± ions, is quite insensitive to the matrix material from which they are emitted. Composition of multilayer HgCdTe structure can be determined with excellent accuracy and depth resolution. Layer thickness of HgCdTe heterostructure can also be calibrated.

A fusion protein library: an improved method for rapid screening and characterization of DNA binding or interacting proteins

A rapid method for screening and characterization of DNA binding or protein-interacting molecules is described. The method relies on a fusion protein library in which randomized DNA fragments are inserted into pGEX-3X and its derivatives to generate collections of GST-fusion proteins. After inducing the expression of the fusion proteins by addition of IPTG, the colonies can be screened either with radioactively labeled DNA/RNA fragment for specific clones encoding DNA/RNA binding proteins or with an antibody for clones encoding proteins of interest. They can also be screened with a radioactively labeled protein for cloning of interacting molecules. The fusion proteins encoded by the isolated clones can be readily purified by conducting the lysis of the cells and an affinity column in the presence of an alkyl anionic detergent, N-laurylsarcosine (sarkosyl), and can be further characterized.

An improved characterization method for petroleum fractions

AbstractAn improved characterization of naphtha can be obtained by assuming representative chemical components for each cut and utilizing an empirical model to predict the physical and thermodynamic properties such as critical properties, molar mass, refractive index, enthalpy of vaporization, viscosity, etc. The improved model for feed characterization utilizes a multivariable constraint optimization technique in order to arrive at the properties of the blend. It was found that this model does improve the accuracy of prediction.An application is presented for a naphtha blending system and a naphtha debutanizer. The sensitivity of the column simulation to the developed feed characterization method has been investigated by digital simulation. With the boiling point model, large deviations from the actual column performance data have been observed while a farily good match has been obtained with the improved model.

An improved method for mRNA isolation and characterization of in vitro translation products by Western blotting

A method is described for isolation of messenger RNA (mRNA) from a rather intractable tissue source, calf stomach. The use of additional RNase inhibitors, vanadyl ribonucleoside complexes and proteinase K, which are used in conjunction with the guanidine thiocyanate/CsCl ultracentrifugation procedure traditionally employed for isolation of mRNA, is described. These modifications make the procedure universally applicable to a wide variety of tissues and cell types. The validity of the procedure is demonstrated by isolation of biologically active full-length preprochymosin mRNA. The integrity of the mRNA is measured by in vitro translation, Northern blot analysis, Southern blot analysis of preprochymosin cDNA using synthetic oligodeoxynucleotide probes and immunospecific identification of in vitro translation products using a modification of the Western blot which is described in this report.

An improved method for characterization of citrate production by conidia ofAspergillus niger

A modification of a method is presented, which enables the characterization of a given conidial material ofAspergillus niger with respect to its capacity to produce citric acid in submerged culture. The procedure can be applied to selection experiments as well as to counteract degeneration during strain maintenance.

An improved method for electrophoretic characterization of globin chains from hemolyzates, purified hemoglobins, and fractions selected from chromatographic separations of chains

Two procedures for separation of globin chains from hemoglobin by starch gel electrophoresis in 6 M urea in EDTA-borate-Tris buffer systems are described. The utility of the systems is demonstrated with comparisons to other approaches for analyzing hemoglobin chains ( a) by characterizing the variant chain for several human hemoglobins using both hemolyzates and purified hemoglobins, ( b) in determining the basis of the failure of canine chains to be resolved by the systems, ( c) by deteeting probable nonheme proteins on CMC chromatograms of human globin chains, and ( d) in characterizing certain “shadow” fractions as being generated from the major globin chains due to oxidation and/or carbamylation.