Operating stresses on S. S. “Michigan” propeller

The failure at sea of a number of merchantship propeller blodes initiated a research program supported by the Maritime Administration, the American Bureau of Shipping, the American President Lines and the States Steamship Company. Although extensive theoretical work has been carried out in the past (predicting propeller operating stresses), very little full-scale experimental stress measurements have been obtained. Brewer Engineering Laboratories, Inc. was retained by the sponsors to attach and protect fifty strain gages on the test propeller at the locations chosen by Littleton Research and Engineering Corporation. The propeller strain gages were protected from the severe environment by means of synthetic rubber and metallic overlays. The gage wiring was led down each blade and into a specially machined, hollow tailshaft through a waterproof bulkhead. The S.S. “Michigan”, with the test group aboard, sailed from Long Beach, Calif., in April 1970. The ship called at the ports of San Francisco, Yokohama, Naha, Manila, Bogo and Hong Kong during the test period. Throughout the trip across the Pacific, the gaging and instrumentation functioned without degradation or evidence of distress after onemillion propeller shaft turns. At the end of five weeks at sea and two-million turns, all but eight gages exhibited low ground resistance. The S.S. “Michigan” went into dry dock at the Bethlehem Steel Shipyard at Terminal Island, Calif., on June 15, 1970. The propeller was removed and all strain gages checked for continuity and ground resistance. Forty-two of the original 50 strain gages were found to be intact. No sign of deterioration due to cavitation or electrolysis attack existed on the metallic overlays or spot welding. Wire chafing within the fairwater adapter cap accounted for the low ground resistance values observed at the end of the voyage to Hong Kong.     

Measurement of thermal stresses within an experimental nuclear-reactor vessel head

This paper describes certain tests and techniques employed in measuring stresses within an experimental nuclear-reactor head of unusual design. The incorporation of certain desired design features necessitated that the head be extremely thick. Due to the thickness and its complex geometry, it was considered desirable to determine stress distribution within the head under conditions of steady-state pressure combined with rapid heating and cooling transients within the reactor, in order to determine safe limits for the operation of the head. A photoelastic study of a three-dimensional model of the reactor head was completed in 1956; this study permitted prediction of the stress distribution throughout the head as a function of internal pressure, but it was not possible to assimilate the head thermal stresses by photoelastic means. It is the purpose of this paper to describe the technique employed in measuring thermal stresses in the interior of the head, under simulated operating conditions of steady-state pressure and temperature transients.     

A study of the induced magnetism in the Au spacer layer of Co/Au/CoO exchange-bias trilayers and related systems

We report the first observation of the effects of exchange bias on the nuclear spin polarization and induced magnetic moments at a magnetic/non-magnetic interface, applying low temperature nuclear orientation (LTNO) to Co/Au(x)/CoO trilayer systems. This technique allows us to determine simultaneously the average alignment of the nuclear moments for the two radioactive probe isotopes 198Au and 60Co with respect to an external magnetic field axis. The total average Au γ-ray anisotropy measured was found (i) to decrease with increasing Au thickness, indicating that large hyperfine fields are restricted to the interfacial Au layers and (ii) to be canted away from the applied field axis even when the Co layers are magnetically saturated. This canting was found to originate at the CoO/Au interface as could be shown from comparative measurements on CoO/Au/CoO trilayers containing two AFM CoO/Au interfaces and on a Co/Au/Co trilayer with two FM Co/Au interfaces. In the case of CoO/Au/CoO, the observed canting was found to be dependent on the Au layer thickness.     

Evidence for static magnetism in the vortex cores of ortho-II YBa2Cu3O6.50

Evidence for static alternating magnetic fields in the vortex cores of underdoped YBa2Cu3O6+x is reported. Muon spin rotation measurements of the internal magnetic field distribution of the vortex state of YBa2Cu3O6.50 in applied fields of H = 1 T and H = 4 T reveal a feature in the high-field tail of the field distribution which is not present in optimally doped YBa2Cu3O6.95 and which fits well to a model with static magnetic fields in the vortex cores. The magnitude of the fields is estimated to be 18(2) G and decreases above T = 10 K. We discuss possible origins of the additional vortex core magnetism within the context of existing theories.     

Experiments on the Magnetism of Sc Implanted into Metals

The study of dilute Sc impurities in either heavier d-transition metals or in alkali metal hosts is difficult due to their limited solubility; however, the large host-impurity mismatch in these systems makes them particularly interesting in terms of local electronic structure. One way to overcome the solubility problem is implantation into the desired host; in particular, using recoil implantation following heavy-ion nuclear reactions, deep implantation into practically any host can be achieved. Here, we compare the implantation of ⁴³Sc into Cs, studied in situ by the in-beam TDPAD method [1], with the implantation of ^44m Sc into Fe, studied by low-temperature nuclear orientation (LTNO) and related techniques (NMRON, thermal cycling) [2].     

Characterization of single- and double-stranded DNA on gold surfaces

Single- and double-stranded deoxy ribonucleic acid (DNA) molecules attached to self-assembled monolayers (SAMs) on gold surfaces were characterized by a number of optical and electronic spectroscopic techniques. The DNA-modified gold surfaces were prepared through the self-assembly of 6-mercapto-1-hexanol and 5'-C(6)H(12)SH -modified single-stranded DNA (ssDNA). Upon hybridization of the surface-bound probe ssDNA with its complimentary target, formation of double-stranded DNA (dsDNA) on the gold surface is observed and in a competing process, probe ssDNA is desorbed from the gold surface. The competition between hybridization of ssDNA with its complimentary target and ssDNA probe desorption from the gold surface has been investigated in this paper using X-ray photoelectron spectroscopy, chronocoulometry, fluorescence, and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS). The formation of dsDNA on the surface was identified by PM-IRRAS by a dsDNA IR signature at approximately 1678 cm(-)(1) that was confirmed by density functional theory calculations of the nucleotides and the nucleotides' base pairs. The presence of dsDNA through the specific DNA hybridization was additionally confirmed by atomic force microscopy through colloidal gold nanoparticle labeling of the target ssDNA. Using these methods, strand loss was observed even for DNA hybridization performed at 25 degrees C for the DNA monolayers studied here consisting of attachment to the gold surfaces by single Au-S bonds. This finding has significant consequence for the application of SAM technology in the detection of oligonucleotide hybridization on gold surfaces.     

Covalent attachment of a nickel nitrilotriacetic acid group to a germanium attenuated total reflectance element

The surface of a germanium internal reflectance element (IRE) was modified to bind 6X-histidine (his)-tagged biomolecules. The step-by-step surface modification was monitored via single-pass attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FT-IR). Initially an adlayer of 7-octenyltrimethoxysilane (7-OTMS) was formed on the Ge crystal through the surface hydroxyl groups, which were produced via ozonolysis of the Ge surface. The vinyl moiety of 7-OTMS was oxidized to a carboxylic acid, which was activated by 1,1'-carbonydiimidazole (CDI) to produce a labile imidazole. The labile imidazole that resulted from the CDI coupling was then displaced by the primary amine of nitrilotriacetic acid (NTA). Nickel sulfate was added to the system, and it coordinated with the three carbonyl groups and the nitrogen on NTA, thus leaving the ability of Ni to coordinate with two adjacent histidine residues. Binding of his-tagged biotin to nickel nitrilotriacetic acid (Ni-NTA) was observed by ATR-FT-IR spectroscopy. The surface modification method presented in this paper had minimal nonspecific binding, the Ni-NTA surface was reusable if stored properly, and complete removal of the organic surface was achievable.     

The BIOREMA project—part 3: International interlaboratory comparison for bio-ethanol test methods

The main objective of the reference materials for biofuel specifications (BIOREMA) project is the development of two test materials (one bio-ethanol material and one biodiesel material) with well-established reference values. Of a series of three papers, this part describes the material preparation, homogeneity study, stability study, and characterisation of the bio-ethanol material. The test material thus obtained was used in an interlaboratory comparison (ILC) to assess current practices and comparability amongst laboratories providing bio-ethanol testing services. Only 13 participants provided data, resulting in a small dataset for evaluation. Further, it appeared that for a number of laboratories, there was not sufficient material for the determination of all requested parameters. In most cases, as far as the data permit, it can be concluded that the consensus values (based on participant’s results) are in good agreement with the reference or the BIOREMA values (obtained by NMIs participating in the project). For three parameters, namely ethanol content, water content, and density, there is good agreement between the reference and consensus values. For these parameters, the reproducibility standard deviation is close to, or even smaller than, the expanded uncertainty associated with the reference value. A number of parameters show very poor reproducibility, for example, pH_e, electrolytic conductivity, and acidity. The same applies to sodium and copper content, which are very low and therefore challenging parameters to measure accurately. The results of the ILC underpin the need for certified reference materials and demonstrate the requirement for more robust quality control to improve the precision and trueness of the results from testing laboratories.     

Ruthenium(II)-polyazine light absorbers bridged to reactive cis-dichlororhodium(III) centers in a bimetallic molecular architecture

Bimetallic complexes of the form [(bpy)(2)Ru(BL)RhCl(2)(phen)](PF(6))(3), where bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, and BL = 2,3-bis(2-pyridyl)pyrazine (dpp) or 2,2'-bipyrimidine (bpm), were synthesized, characterized, and compared to the [{(bpy)(2)Ru(BL)}(2)RhCl(2)](PF(6))(5) trimetallic analogues. The new complexes were synthesized via the building block method, exploiting the known coordination chemistry of Rh(III) polyazine complexes. In contrast to [{(bpy)(2)Ru(dpp)}(2)RhCl(2)](PF(6))(5) and [{(bpy)(2)Ru(bpm)}(2)RhCl(2)](PF(6))(5), [(bpy)(2)Ru(dpp)RhCl(2)(phen)](PF(6))(3) and [(bpy)(2)Ru(bpm)RhCl(2)(phen)](PF(6))(3) have a single visible light absorber subunit coupled to the cis-Rh(III)Cl(2) moiety, an unexplored molecular architecture. The electrochemistry of [(bpy)(2)Ru(dpp)RhCl(2)(phen)](PF(6))(3) showed a reversible oxidation at 1.61 V (vs Ag/AgCl) (Ru(III/II)), quasi-reversible reductions at -0.39 V, -0.74, and -0.98 V. The first two reductive couples corresponded to two electrons, consistent with Rh reduction. The electrochemistry of [(bpy)(2)Ru(bpm)RhCl(2)(phen)](PF(6))(3) exhibited a reversible oxidation at 1.76 V (Ru(III/II)). A reversible reduction at -0.14 V (bpm(0/-)), and quasi-reversible reductions at -0.77 and -0.91 V each corresponded to a one electron process, bpm(0/-), Rh(III/II), and Rh(II/I). The dpp bridged bimetallic and trimetallic display Ru(dpi)-->dpp(pi*) metal-to-ligand charge transfer (MLCT) transitions at 509 nm (14,700 M(-1) cm(-1)) and 518 nm (26,100 M(-1) cm(-1)), respectively. The bpm bridged bimetallic and trimetallic display Ru(dpi)-->bpm(pi*) charge transfer (CT) transitions at 581 nm (4,000 M(-1) cm(-1)) and 594 nm (9,900 M(-1) cm(-1)), respectively. The heteronuclear complexes [(bpy)(2)Ru(dpp)RhCl(2)(phen)](PF(6))(3) and [{(bpy)(2)Ru(dpp)}(2)RhCl(2)](PF(6))(5) had (3)MLCT emissions that are Ru(dpi)-->dpp(pi*) CT in nature but were red-shifted and lower intensity than [(bpy)(2)Ru(dpp)Ru(bpy)(2)](PF(6))(4). The lifetimes of the (3)MLCT state of [(bpy)(2)Ru(dpp)RhCl(2)(phen)](PF(6))(3) at room temperature (30 ns) was shorter than [(bpy)(2)Ru(dpp)Ru(bpy)(2)](PF(6))(4), consistent with favorable electron transfer to Rh(III) to generate a metal-to-metal charge-transfer ((3)MMCT) state. The reported synthetic methods provide means to a new molecular architecture coupling a single Ru light absorber to the Rh(III) center while retaining the interesting cis-Rh(III)Cl(2) moiety.     

Photoinitiated electron collection at a metal in a rhodium-centered mixed-metal supramolecular complex

A mixed-metal supramolecular complex [{(bpy)2Ru(dpp)}2RhCl2]5+ has been studied and shown to undergo photoinitiated electron collection at the metal center. Reported herein is an analysis of the photochemical properties of this complex, illustrating the ability of this complex to photoreduce by two electrons by converting Rh(III) to Rh(I) and with the trimetallic assembly remaining intact. Emission-quenching experiments demonstrate efficient quenching of the Ru --> dpp charge-transfer state by the Rh center and the electron-donor dimethylaniline.