Search for evidence of nuclear involvement in the fatal explosion of a “cold fusion” experiment

Forensic analyses of debris from the fatal explosion of an electrochemical cold fusion cell at SRI International were conducted at LLNL at the request of Cal-OSHA. One investigation focused on the possibility of conventional nuclear reaction mechanisms contributing to the total energy inventory of the incident. Selected metal components of the electrolysis apparatus were subjected to nondestructive -ray spectrometry with high-sensitivity, low-background Ge detector systems. The anticipated analytes in these studies were radioactivation products potentially induced in the explosion residue by either fast or thermal neutrons. The results of this investigation were negative within the temporal constraints of the incident and the analytical sensitivities of the instrumentation.     

Inter-DNA attraction mediated by divalent counterions

Can nonspecifically bound divalent counterions induce attraction between DNA strands? Here, we present experimental evidence demonstrating attraction between short DNA strands mediated by Mg2+ ions. Solution small angle x-ray scattering data collected as a function of DNA concentration enable model independent extraction of the second virial coefficient. As the [Mg2+] increases, this coefficient turns from positive to negative reflecting the transition from repulsive to attractive inter-DNA interaction. This surprising observation is corroborated by independent light scattering experiments. The dependence of the observed attraction on experimental parameters including DNA length provides valuable clues to its origin.     

Strain tensor for large three-dimensional surface deformation of sheet metal from an object grating

Grating techniques are used to determine the three-dimensional deformation and the tangential strain of sheet metal. A grating is fixed on the surface and taken by stereo CCD cameras in different deformation states. By suitable line-following software, the grating coordinates in the images are determined with subpixel accuracy. Using photogrammetric methods, the three-dimensional coordinates are calculated from the image coordinates. The strain usually is determined by means of a deformation gradient, which is calculated from every deformed triangle. In this paper, the gradient is determined in the center of four neighboring meshes using a polynomial approximation of the displacement function in a reference position. The influence of the nontangential deformation is considered. By simulation, a flat sheet metal is deformed to a rotational symmetric surface. The difference of the known exact strain is compared with the numerically derived strain with respect to different grating pitches. The proposed method yields good results even in the case of large spatial deformation. It is applied to the deformation of a hatlike test specimen.     

Insulating state in open quantum dots and quantum dot arrays

We describe the observation of novel localization in mesoscopic quantum dots and quantum dot arrays, which are realized in high mobility GaAs/AlGaAs heterojunctions using the split‐gate technique. With a sufficient gate voltage applied to form the devices, their resistance diverges as the temperature is lowered below a degree Kelvin, behavior which we attribute to localization. Evidence for the localization is found over the entire range of gate voltage for which the dots are defined, persisting to conductances higher than 50e²/h.     

New roles for mathematics in multi-disciplinary, upper secondary school projects

A new concept, compulsory multi-disciplinary courses, was introduced in upper secondary school curriculum as a central part of a recent reform. This paper reports from a case study of such a triple/four-disciplinary project in mathematics, physics, chemistry and ‘general study preparation’ performed under the reform by a team of experienced teachers. The aim of the case study was to inquire how the teachers met the demands of the introduction of this new concept and, to look for signs of new relations established by the students between mathematics and other subjects, as a result of the multi-disciplinary teaching. The study revealed examples of good practice in planning and teaching. In addition, it served to illuminate interesting aspects of how students perceived the school subject mathematics and its relations to other subjects and to common sense.     

Preparation and characterization of MgB2 superconductor

The MgB₂ superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties. The upper critical field, irreversibility line and critical current density have been determined using magnetization data. The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition. The surface analysis using X-ray photoelectron spectroscopy shows that MgB₂ is sensitive to atmospheric degradation.     

New algorithms and complexity status of the reducibility problem of sequences in open shop scheduling minimizing the makespan

We consider the problem of minimizing the makespan in open shop scheduling. The decision problem whether a given sequence in open shop scheduling is irreducible has already been considered, however, has not been solved yet. A sequence is an acyclic orientation of the Hamming graph K _n ×K _m . Irreducible sequences in open shop are the local optimal elements. We present two variants of algorithms based on the specific properties of the H-comparability graph. The first is polynomial whereas the second is exponential. The irreducibility is co-NP. The stated properties argue whether it belongs to P. The complexity status of the considered decision problem is updated.     

A comparison of gas-phase,plasma, sputtering and beam-foil excitations

A comparison of relative populations of ZnI and ZnII levels excited in equilibrium plasma, sputtering, gas-phase single collision, and beam foil sources is presented, and includes data on the first reported excitation studies under single collision conditions for a (transition metal atom)-(transition metal ion) interaction. A search for continuum emission from atomic chromium, like that seen during sputtering of chromium metal, produced a negative result.     

On certain subgraphs of a complete transitively directed graph

Let G_n be a complete transitively directed graph with n + 1 vertices v₀, v₁, …, v_n. Let ψ(n) be the number of subgraphs H of G_n where each vertex in H lies along a directed path from v₀ to v_n in H. ψ(n) and some related quantities are calculated.     

Studies of miscibility,transesterification and crystallization in blends of poly(ethylene terephthalate) and Poly(ethylene-2,6-naphthalene dicarboxylate)

Blends of poly(ethylene terephthalate) (PET) and poly(ethylene-2,6-naphthalene dicarboxylate) (PEN) were obtained by coprecipitation from solution followed by melt-pressing for different timest _mand quenching in iced water. When the melt-pressing time was 0.2 and 0.5 min, two glass transition temperaturesT _gwere observed by means of dynamic mechanical analysis (DMA), indicating that there are two phases present, a PEN-rich phase and a PET-rich phase. The differential scanning calorimetry (DSC) curves show two crystallization peaks and two melting peaks which, according to wide-angle x-ray scattering (WAXS) measurements, can be attributed to PET and PEN, respectively. In the case oft _m=2 min or longer, a single value ofT _gand thus a single phase is found to exist. Fort _m=10 min and 45 min no crystallization and melting at all is observed during heating with 10°C/min, indicating that a copolyester of PET and PEN has been formed by transesterfication during melt-pressing.Time-resolved WAXS measurements during isothermal crystallization show that, in the blend, the half-time of crystallization of PET is different from that of PEN, and not the same as that which is found in the pure polymer.Dedicated with best wishes to Prof. Dr. E.W. Fischer on the occasion of his 65th birthday