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Half-Heusler compounds have been in focus as potential materials for thermoelectric energy conversion in the mid-temperature range, e.g., as in automotive or industrial waste heat recovery, for more than ten years now. Because of their mechanical and thermal stability, these compounds are advantageous for common thermoelectric materials such as Bi 2 Te 3 , SiGe, clathrates or filled skutterudites. A further advantage lies in the tunability of Heusler compounds, allowing one to avoid expensive and toxic elements. Half-Heusler compounds usually exhibit a high electrical conductivity σ , resulting in high power factors. The main drawback of half-Heusler compounds is their high lattice thermal conductivity. Here, we present a detailed study of the phase separation in an n-type Heusler materials system, showing that the Ti x Zr y Hf z NiSn system is not a solid solution. We also show that this phase separation is key to the thermoelectric high efficiency of n-type Heusler materials. These results strongly underline the importance of phase separation as a powerful tool for designing highly efficient materials for thermoelectric applications that fulfill the industrial demands of a thermoelectric converter.

Half-Heusler compounds have been in focus as potential materials for thermoelectric energy conversion in the mid-temperature range, e.g., as in automotive or industrial waste heat recovery, for more than ten years now. Because of their mechanical and thermal stability, these compounds are advantageous for common thermoelectric materials such as Bi2Te3, SiGe, clathrates or filled skutterudites. A further advantage lies in the tunability of Heusler compounds, allowing one to avoid expensive and toxic elements. Half-Heusler compounds usually exhibit a high electrical conductivity σ, resulting in high power factors. The main drawback of half-Heusler compounds is their high lattice thermal conductivity. Here, we present a detailed study of the phase separation in an n-type Heusler materials system, showing that the TixZryHfzNiSn system is not a solid solution. We also show that this phase separation is key to the thermoelectric high efficiency of n-type Heusler materials. These results strongly underline the importance of phase separation as a powerful tool for designing highly efficient materials for thermoelectric applications that fulfill the industrial demands of a thermoelectric converter.

The structure and elementary physical properties of a new intermetallic compound, β - HfCuGe , are reported. β - HfCuGe has a tetragonal structure (space group I4/mmm) with lattice constants of a=3.7634(11)A and c=13.499(4) A. The structure, which consists of double layers of Hf stacked with edge-sharing CuGe4 squares, is not typical for intermetallic compounds and appears to be a new structure type. The compound is a weak paramagnet and a normal metal down to 0.4 K.

This work elucidates the possible reasons for the outstanding, but never reproduced thermoelectric properties of the doped Ti(0.5)Zr(0.25)Hf(0.25)NiSn Heusler compounds. The structural investigations done via synchrotron X-ray diffraction measurements and scanning electron microscope measurements, which clearly show that the microstructure consists of three temperature stable C1(b) phases with possible semi-coherent interfaces, are presented. The exceptional thermoelectric properties are due to this intrinsic phase separation. It is possible to reproduce the high Figure of Merit values with ZT = 1.2 at 830 K. Furthermore, the influence of doping different elements on the Sn position in this Heusler material system is investigated.

The MNiSn (M = Ti, Zr, Hf) half-Heusler semiconducting compounds are widely investigated due to their good potential for thermoelectric (TE) power generation applications. In the current work, the evolution of the transport and structural properties of the Ti0.3Zr0.35Hf0.35NiSn compound upon various thermal treatments was studied. The nominal composition was arc melted, ball milled, and spark plasma sintered (SPS). Following SPS, large Hf-rich domains were found by scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Subsequently, the samples were subjected to homogenization treatments at 1163 K for 480 h and 610 h under argon atmosphere. Following these thermal treatments, the relative amount of the Hf-rich domains was reduced and they became smaller in size, with increasing thermal treatment duration. Nevertheless, no uniphased structure was reached. The dissolution of the Hf-rich domains in the half-Heusler matrix resulted in increase of both the Seebeck coefficient and electrical resistivity values and a decrease of the carrier concentration, attributed to elimination of these metallic domains. Resulting from the high atomic disorder caused by substitution at the M site, low thermal conductivity values of ~3.8 W m−1 K−1 were obtained leading to high ZT values of up to 0.82 following SPS.

A thermodynamically stable phase separation of Co2Dy0.5Mn0.5Sn into the Heusler compound Co2MnSn and Co8Dy3Sn4 is induced by rapid cooling from the liquid phase. The phase separation forms an ordered flower-like structure on the microscale. The increased scattering of phonons at the phase boundaries reduces the thermal conductivity and thus improves thermoelectric and spincaloric properties.

Due to their exceptional thermoelectric properties Half-Heusler alloys like MNiSn (M = Ti,Zr,Hf) have moved into focus. The growth of single crystalline thin film TiNiSn and Zr 0.5 Hf 0.5 NiSn by dc magnetron sputtering is reported. Seebeck and resistivity measurements were performed and their dependence on epitaxial quality is shown. Seebeck coefficient, specific resistivity and power factor for Zr 0.5 Hf 0.5 NiSn at room temperature were measured to be 63 μV K − 1 , 14.1 μΩ m and 0.28 mW K − 2 m − 1 , respectively. Multilayers of TiNiSn and Zr 0.5 Hf 0.5 NiSn are promising candidates to increase the thermoelectric figure-of-merit by decreasing thermal conductivity perpendicular to the interfaces. The epitaxial growth of multilayers containing TiNiSn and Zr 0.5 Hf 0.5 NiSn is demonstrated by measuring satellite peaks in the X-ray diffraction pattern originating from the additional symmetry perpendicular to the film surface.

In this report an alternative approach for optimization of the thermoelectric properties of half-Heusler compounds is presented. The common approaches are partial substitution of elements by elements of nearby groups and substitution with homologs. In this approach we substitute one element by one neighboring element with fewer valence electrons and by one with more electrons. The amounts of the substitutions are chosen such that the amount of deficiency and excess electrons are compensated. In the solid solution $$\hbox{TiCo}_{x}(\hbox{Ni}_{0.5}\hbox{Fe}_{0.5})_{1-x}\hbox{Sb}$$ , Co was substituted equally by Fe and Ni. The aim of the substitution was to improve the figure of merit by a reduction of the thermal conductivity accompanied by an unchanged high Seebeck coefficient. The solid solution $$\hbox{TiCo}_{x}(\hbox{Ni}_{0.5}\hbox{Fe}_{0.5})_{1-x}\hbox{Sb}$$ was synthesized by arc-melting. The structure of the as-cast samples was analyzed by x-ray diffraction. Rietveld refinements yielded the $$C1_b$$ structure type with a small amount of antisite disorder between Co and Sb. The thermoelectric properties of the solid solution were investigated in the temperature range from 2 K to 400 K. A Seebeck coefficient of $$-260\,\mu\hbox{V\,K}^{-1}$$ at 400 K and a reduction of the thermal conductivity to $$3\,\hbox{Wm}^{-1}\,\hbox{K}^{-1}$$ were measured. The figure of merit was enhanced by a factor of about seven to a value of 0.04 at 400 K for $$\hbox{TiCo}_{0.8}(\hbox{Ni}_{0.1}\hbox{Fe}_{0.1})\hbox{Sb}$$ .

Turbo equalization is a promising approach to deal with the inter-symbol interference when transmitting over frequency selective radio channels. The iterative exchange of soft information between the equalizer and the decoder improves the decision reliability and hence reduces the bit error probability compared to conventional receivers. However, the processing of real-valued soft information with floating point precision causes high memory consumption and complex arithmetic logic units. In this paper, the effects of a fixed-point implementation of linear minimum mean square error (MMSE) based turbo equalizers with soft cancellation (SC) are studied. The applied soft-input soft-output (SISO) algorithms are analyzed concerning the value range and efficient fixed-point representations are derived. Results show, that even for small word lengths of 8 bit, the performance loss is negligible.

The structure and elementary physical properties of a new intermetallic compound, β - HfCuGe , are reported. β - HfCuGe has a tetragonal structure (space group I4/mmm) with lattice constants of a=3.7634(11)A and c=13.499(4) A. The structure, which consists of double layers of Hf stacked with edge-sharing CuGe4 squares, is not typical for intermetallic compounds and appears to be a new structure type. The compound is a weak paramagnet and a normal metal down to 0.4 K.

The present work reports on the new soft ferromagnetic Heusler phases Fe${}_{2}$NiGe, Fe${}_{2}$CuGa, and Fe${}_{2}$CuAl, which in previous theoretical studies have been predicted to exist in a tetragonal Heusler structure. Together with the known phases Fe${}_{2}$CoGe and Fe${}_{2}$NiGa these materials have been synthesized and characterized by powder x-ray diffraction, ${}^{57}$Fe M\"ossbauer spectroscopy, superconducting quantum interference device, and energy-dispersive x-ray measurements. In particular M\"ossbauer spectroscopy was used to monitor the degree of local atomic order/disorder and to estimate magnetic moments at the Fe sites from the hyperfine fields. It is shown that in contrast to the previous predictions all the materials except Fe${}_{2}$NiGa basically adopt the inverse cubic Heusler ($X$) structure with differing degrees of disorder. The experimental data are compared with results from ab initio electronic structure calculations on local-density approximation level incorporating the effects of atomic disorder by using the coherent potential approximation. A good agreement between calculated and experimental magnetic moments is found for the cubic inverse Heusler phases. Model calculations on various atomic configurations demonstrate that antisite disorder tends to enhance the stability of the $X$ structure.

The root system of maize consists of the primary root and a variable number of lateral seminal-, crown- and brace roots. Except for the primary root and some minor roots forming at the mesocotyl, all other roots grow out of nodal regions, namely, the embryogenic scutellar node and the underground—as well as the lower above-ground stem nodes. Besides their role in water and nutrient uptake, some of these roots (crown- and brace roots) are essential for the lodging resistance of the plants. This property of the crown roots has now been successfully used for screening a segregating F2 population of a cross between a flint inbred line and an En transposon line. Two allelic root-deficient mutants have been isolated and have been designated rtcs-1 and rtcs-2 for their complete lack of formation of crown- and lateral seminal roots. They survive by the ability of the primary root to support the growth of the developing plant. The monogenic and recessive mutants appear to be affected in an early root-forming function since no primordia are formed either in the case of embryo-borne lateral seminal or stem-derived crown roots. The Rtcs locus could be mapped to the short arm of chromosome 1 with the help of a co-segregating RAPD marker. The effect of the mutation seems to be highly specific since no pleiotropic effects on other parts of the plants have been observed. The formation of adventitious roots can, however, still be induced in the mesocotyl region of the mutant.

The Heusler compound CoTiSb was synthesized and investigated theoretically and experimentally with respect to electronic structure and optical, mechanical, and vibrational properties. The optical properties were investigated in a wide spectral range from 10 meV to 6.5 eV and compared with ab initio calculations. The optical spectra confirm the semiconducting nature of CoTiSb, with a strong exciton absorption at 1.83 eV. The calculated phonon dispersion as well as elastic constants verify the mechanical stability of CoTiSb in the cubic $C{1}_{b}$ system. Furthermore, solid solution series of CoTi${}_{1\ensuremath{-}x}$${M}_{x}$Sb ($M=\text{Sc}$, V and $0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.2$) were synthesized and investigated. The transport properties were calculated by all-electron ab initio methods and compared to the measurements. The thermoelectric properties were investigated by measuring the temperature dependence of electrical resistivity, Seebeck coefficient, and thermal conductivity. The thermal conductivity of the substituted compounds was significantly reduced. Sc substitution resulted in a $p$-type behavior with a high Seebeck coefficient of +177.8 $\ensuremath{\mu}$V/K (350 K) at 5$%$ Sc substitution. This value is in good agreement with the calculations. Fully relativistic Korringa--Kohn--Rostoker calculations in combination with the coherent potential approximation clarify the different contribution of states in the (001) plane of the Fermi surface for Sc- or V-substituted compounds CoTi${}_{0.95}$${M}_{x}$Sb ($M=\text{Sc}$, V).

Waveform development is an important topic of the Software Defined Radio (SDR) technology. To achieve the objectives of SDR, waveforms have to be efficient and portable to various platforms.

This work reports on the structural and physical properties of the Heusler alloy (Zr0.5Hf0.5)1−xNbxNiSn with varying Nb concentrations. The structure of the (Zr0.5Hf0.5)1−xNbxNiSn solid solution was investigated by means of X-ray diffraction. It is found that the alloys exhibit the C1b structure for all Nb concentrations. The physical properties were studied using the physical properties measurement system from low temperature to room temperature. It was shown that the thermoelectric properties like the dimensionless Figure of Merit are increased five times by substituting (Zr0.5Hf0.5) with Nb to 0.09 at 300 K and the Powerfactor is increased 10 times to 1.8 mW/K2 m at 300 K.

The effect of Ti substitution by Sc on the thermoelectric properties of the Heusler compounds NiTi0.3−xScxZr0.35Hf0.35Sn (where 0

Ninety-eight different malignant adnexal tumors were analyzed for the presence of epidermal growth factor (EGF)-specific binding sites and binding parameters were calculated by Scatchard plot analysis [G. Scatchard, Ann. N.Y. Acad. Sci. 51 , 660–672 (1949)]. Thirty-four biopsies were EGF receptor (EGF-R) positive with dissociation constants ( K D ) of 0.5–12 × 10 −9 M and binding capacities ( B max ) of 2–250 fmol/mg. One tumor had a K D of 60 × 10 −9 M and a B max of 1660 fmol/mg. The correlation of EGF-R status with clinical parameters showed no significant differences in primary, metastatic, or recurrent tumors, histological subtype, tumor differentiation, and tumor residual after primary surgery. As an inverse correlation, EGF-R-positive tumors are 39% and EGF-R-negative tumors 60% progesterone receptor positive. A response to chemotherapy was noticed in 50% of EGF-R-positive ovarian carcinomas with a mean survival time of patients of 28 months. The response rate of EGF-R negative ovarian carcinomas was 12% with a mean survival time of 16 months. Regarding the treatment schedule the major differences were noticed in the cis -platinum plus cyclophosphamide treatment group. These results suggest that the biology of ovarian carcinomas is influenced by growth factors and their receptors, which can be used as prognostic factors.

Low temperature pulses have two effects on the circadian rhythm exhibited by stem extension rate of green Chenopodium rubrum plants. First, low temperature pulses have the same effect on the phasing of the rhythm as a dark period interrupting continuous light. Second, low temperature pulses stimulate stem extension rate during the 10 hours immediately following the end of the pulse. A difference in temperature between soil and air increases this effect. In any case, it is the change in temperature which is essential and not a specific temperature. Effects of light and temperature on phasing and amplitude of the rhythm explain why the maximal stem growth is observed under normal photo-thermoperiodic conditions, i.e. a high temperature during the photoperiod and a low temperature during the dark period.

Protoplasts, isolated from 10-day-old maize kernels and from a maize embryogenic suspension culture (BMS), were transiently transformed by electroporation with expression plasmids. These plasmids consisted of the CAT gene under the direction of the promoter from a 19-kDa zein gene from maize and of the 35S promoter from Cauliflower Mosaic Virus. Measurement of CAT activity in the transformed protoplasts showed that the zein promoter is only active in protoplasts derived from kernels, while the 35S promoter functions in protoplasts from both kernels and cell culture.