Thermal, magnetic and electronic properties of non-centrosymmetric YbPt2B.

Ternary YbPt2B crystallizes in the non-centrosymmetric hexagonal CePt2B-type structure (space group P6(2)22). Electrical resistivity, specific heat and magnetic measurements reveal a magnetic instability at 5.6 K. Furthermore, a spin-reorientation of presumably a ferromagnetic type occurs around 1.5 K. The behaviour at low temperature is governed by a rather weak Kondo effect, T(K) ⩽ 1 K, in the presence of strong crystalline electric field splitting, with a doublet ground state. Besides, the complex magnetic behaviour presumably results from a Dzyaloshinskii-Moriya interaction triggered by the absence of inversion symmetry in the crystal structure. Scaling according to the de Gennes factor traces back magnetic ordering in YbPt2B to the Rudermann-Kittel-Kasuya-Yoshida (RKKY) interaction and the smooth evolution of the lattice constants and the unit cell volume of REPt2B (RE = rare earths) refers to the 4f(13) electronic configuration of Yb in YbPt2B.

The system uranium-palladium-boron with U(2.5)Pd(20.5)B(6), a new heavy fermion compound.

Phase equilibria in the system U-Pd-B were established at 850 °C by light optical microscopy (LOM) and x-ray powder and single crystal diffraction. Whereas in as-cast alloys only one ternary compound, τ(1)-U(2 + x)Pd(21 - x)B(6), was found to form at x ∼ 0.5, a further compound τ(2) with hitherto unknown structure was observed in alloys annealed at 850 °C. Due to the formation of suitable single crystals, the crystal structures of two binary compounds, UB(12) and UPd(3) have been redetermined from high precision x-ray data. Similarly, the crystal structure of τ(1)-U(2.5)Pd(20.5)B(6) was investigated by single crystal x-ray diffraction (XRD) revealing isotypism with the Cr(23)C(6)-type, (space group [Formula: see text]; a = 1.1687(5) nm; R(F)(2) = Σ|F(0)(2) - F(c)(2)|/ΣF(0)(2) = 0.021). τ(1)-U(2 + x)Pd(21 - x)B(6) is a partially ordered compound where 0.37(1)U + 0.63Pd atoms randomly share the 4a site in (0, 0, 0). Whereas mutual solubility of U-borides and Pd-borides was found at 850 °C to be below 1.0 at.%, a large homogeneity region of fcc-Pd(U, B) extends into the ternary system. U(2.5)Pd(20.5)B(6) has metallic behavior; the ground state properties are determined from a balance of the Kondo effect and the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, revealing long range antiferromagnetic ordering below 6 K. An extraordinarily large Sommerfeld value (γ > 500 mJ mol(-1) K(-2)) groups U(2.5)Pd(20.5)B(6) among heavy fermion materials.

On the physical properties of RPd(8)B(2-x) and R(3)Pd(25-x)B(8-y) (R = La, Ce).

Physical properties (magnetization, electrical resistivity and specific heat in the temperature range from 2 to 270 K (0.3-270 K for the resistivity)) have been determined for polycrystalline samples of the ternary compounds RPd(8)B(2 - x) (CePd(8)B(2 - x) type; space group C 2/c) and R(3)Pd(25 - x)B(8 - y) (La(3)Pd(25 - x)B(8 - y) type; space group P 2(1)/c) with R = La, Ce. Rietveld refinement of x-ray powder intensity data confirmed the crystal structure and single-phase condition. LaPd(8)B(2 - x) is a novel representative of the CePd(8)B(2 - x) type (a = 1.7838(1) nm, b = 1.040 24(4) nm, c = 1.164 60(6) nm, ß = 118.56(1)°). Both cerium compounds behave like Kondo lattices.

[Direct switch from conventional levodopa to stalevo (levodopa/carbidopa/entacapone) improves quality of life in Parkinson's disease: results of an open-label clinical study].

UNLABELLED: The most effective symptomatic treatment for Parkinson's disease (PD) is levodopa/dopa decarboxylase (DDC)-inhibitor or conventional levodopa. However, after a few years of treatment, motor complications may develop, such as <> and dyskinesias. Symptoms of <> can be both motor symptoms, e.g. tremor and bradykinesia, as well as non-motor symptoms (pain, mood changes and anxiety). The development of these complications may affect the patients quality of life (QOL). To investigate the efficacy and safety direct switch from conventional levodopa to stalevo(levodopa/carbidopa/entacapone) in PD patients with fluctuations and dyskinesias. METHODS/PATIENTS: Thirty four patients with PD were recruited in the study. The mean age (+/-SD) of the patients was 64,5+/-8,3 years, the mean duration of PD (+/-SD) was 5,9+/-3,1 years, the mean H&Y was 2,5+/-0,5. All patients experienced fluctuations and six had dyskinesias (one patient had biphasic dyskinesias with painful dystonia). The mean baseline levodopa dose was 785,8+/-150,2 mg per day taking in three to six doses. Assessments were performed before, end of 1, 4 and 12 weeks of treatment period and consisted of Hoen/Yahr stages (H&Y), II and III parts of the Unified Parkinson's Disease Rating Scale (UPDRS), patients diaries with registration <> periods, scale EQ-5D, WOQ-9. While switching from conventional levodopa to stalevo taking single levodopa doses were equivalent or less. Maximum allowed doses of stalevo were four times per day. RESULTS: Direct switch to stalevo results in improvement of motor and non-motor symptoms (pain and anxiety) in fluctuating patients and significant prolongation of <> periods (p<0.01). We observed dramatic improvement biphasic dyskinesias with painful dystonia and reducing severity of dyskinesias in others patients. Improvement was seen in QOL by scale EQ-5D from 10,7+/-1,9 to 8,6+/-2,1 points (p<0,05). Conclusions. Switching from conventional levodopa to stalevo is efficacy and safety and can significantly improve QOL PD patients with fluctuations and dyskinesias.

The formation, structure and physical properties of M(2)Pd(14+x)B(5-y) compounds, with M = La, Ce, Pr, Nd, Sm, Eu, Gd, Lu and Th.

Novel ternary compounds, M(2)Pd(14+x)B(5-y) (M =  La, Ce, Pr, Nd, Sm, Eu, Gd, Lu, Th; x∼0.9, y∼0.1), have been synthesized by arc melting. The crystal structures of Nd(2)Pd(14+x)B(5-y) and Th(2)Pd(14+x)B(5-y) were determined from x-ray single-crystal data and both are closely related to the structure type of Sc(4)Ni(29)B(10). All compounds were characterized by Rietveld analyses and found to be isotypic with the Nd(2)Pd(14+x)B(5-y) type. Measurements of the temperature dependent susceptibility and specific heat as well as the temperature and field dependent resistivity were employed to derive basic information on bulk properties of these compounds. The electrical resistivity of M(2)Pd(14+x)B(5-y), in general, is characterized by small RRR (residual resistance ratio) values originating from defects inherent to the crystal structure. Whereas the compounds based on Ce, Nd, Sm and Gd exhibit magnetic order, those based on Pr and Eu seem to be non-magnetic, at least down to 400 mK. While the non-magnetic ground state of the Pr based compound is a consequence of crystalline electric field effects in the context of the non-Kramers ion Pr, the lack of magnetic order in the case of the Eu based compound results from an intermediate valence state of the Eu ion.