Growth and characterization of thorium-doped calcium fluoride single crystals.

We have grown [Formula: see text]Th:CaF[Formula: see text] and [Formula: see text]Th:CaF[Formula: see text] single crystals for investigations on the VUV laser-accessible first nuclear excited state of [Formula: see text]Th, with the aim of building a solid-state nuclear clock. To reach high doping concentrations despite the extreme scarcity (and radioactivity) of [Formula: see text]Th, we have scaled down the crystal volume by a factor 100 compared to established commercial or scientific growth processes. We use the vertical gradient freeze method on 3.2 mm diameter seed single crystals with a 2 mm drilled pocket, filled with a co-precipitated CaF[Formula: see text]:ThF[Formula: see text]:PbF[Formula: see text] powder in order to grow single crystals. Concentrations of [Formula: see text] cm[Formula: see text] have been realized with [Formula: see text]Th with good (> 10%) VUV transmission. However, the intrinsic radioactivity of [Formula: see text]Th drives radio-induced dissociation during growth and radiation damage after solidification. Both lead to a degradation of VUV transmission, currently limiting the [Formula: see text]Th concentration to [Formula: see text] cm[Formula: see text].

Microstructure and Mechanical Properties of Hypereutectic Al-High Si Alloys up to 70 wt.% Si-Content Produced from Pre-Alloyed and Blended Powder via Laser Powder Bed Fusion.

Hypereutectic Al-high Si alloys are of immense interest for applications in the automotive, space or electronic industries, due their low weight, low thermal expansion, and excellent mechanical and tribological properties. Additionally, their production by laser powder bed fusion (LPBF) technology provides high flexibility in geometrical design and alloy composition. Since, most of the alloy properties could be improved by increasing the Si content, there is much interest in discovering the maximum that could be realized in LBPF Al-high Si alloys, without the appearance of any material failure. For this reason, in this work the production of Al-high Si alloys with extremely high silicon content of up to 70 wt.% was fundamentally investigated with respect to microstructure and mechanical properties. Highly dense (99.3%) and crack-free AlSi50 samples (5 × 5 × 5 mm3), with excellent hardness (225 HV5) and compressive strength (742 MPa), were successfully produced. Further, for the first time, AlSi70 LBPF samples of high density (98.8%) without cracks were demonstrated, using moderate scanning velocities. Simultaneously, the hardness and the compressive strength in the AlSi70 alloys were significantly improved to 350 HV5 and 935 MPa, as a result of the formation of a continuous Si network in the microstructure of the alloy. With respect to the powder source, it was found that the application of powder blends resulted in similar alloy properties as if pre-alloyed powders were used, enabling higher flexibility in prospective application-oriented alloy development.

High-Performance n-Type Ge-Free Silicon Thermoelectric Material from Silicon Waste.

Silicon waste (SW), a byproduct from the photovoltaic industry, can be a prospective and environmentally friendly source for silicon in the field of thermoelectric (TE) materials. While thermoelectricity is not as sensitive toward impurities as other semiconductor applications, the impurities within the SW still impede the enhancement of the thermoelectric figure of merit, zT. Besides, the high thermal conductivity of silicon limits its applications as a TE material. In this work, we employ traditionally metallurgical methods in industry reducing the impurities in SW to an extremely low level in an environmentally friendly and economical way, and then the thermal conductivity of purified silicon is greatly reduced due to the implementation of multiscale phonon scattering without degrading the power factor seriously. Benefiting from these strategies, from 323 to 1123 K, for the sample made from purified silicon waste, the average zT, relevant for engineering application, is increased to 0.32, higher than that of the state-of-the-art n-type Ge-free bulk silicon materials made from commercially available silicon, but the total cost of our samples is negligible.

The impact of dislocations on AlGaN/GaN Schottky diodes and on gate failure of high electron mobility transistors.

GaN epitaxially grown on Si is a material for power electronics that intrinsically shows a high density of dislocations. We show by Conductive Atomic Force Microscopy (C-AFM) and Defect Selective Etching that even for materials with similar total dislocation densities substantially different subsets of dislocations with screw component act as current leakage paths within the AlGaN barrier under forward bias. Potential reasons are discussed and it will be directly shown by an innovative experiment that current voltage forward characteristics of AlGaN/GaN Schottky diodes shift to lower absolute voltages when such dislocations are present within the device. A local lowering of the Schottky barrier height around conductive dislocations is identified and impurity segregation is assumed as responsible root cause. While dislocation related leakage current under low reverse bias could not be resolved, breakdown of AlGaN/GaN Schottky diodes under high reverse bias correlates well with observed conductive dislocations as measured by C-AFM. If such dislocations are located near the drain side of the gate edge, failure of the gate in terms of breakdown or formation of percolation paths is observed for AlGaN/GaN high electron mobility transistors.

Management of pain in individuals with spinal cord injury: Guideline of the German-Speaking Medical Society for Spinal Cord Injury.

Introduction: Pain is a prominent complication in spinal cord injury (SCI). It can either occur as a direct or as an indirect consequence of SCI and it often heavily influences the quality of life of affected individuals. In SCI, nociceptive and neuropathic pain can equally emerge at the same time above or below the level of injury. Thus, classification and grading of pain is frequently difficult. Effective treatment of SCI-related pain in general and of neuropathic pain in particular is challenging. Current treatment options are sparse and their evidence is considered to be limited. Considering these aspects, a clinical practice guideline was developed as basis for an optimized, comprehensive and standardized pain management in SCI-related pain. Methods: The German-Speaking Medical Society for Spinal Cord Injury (Deutschsprachige Medizinische Gesellschaft für Paraplegiologie - DMGP) developed a clinical practice guideline that received consensus from seven further German-speaking medical societies and one patient organization. The evidence base from clinical trials and meta-analyses was summarized and subjected to a structured consensus-process in accordance with the regulations of the Association of Scientific Medical Societies in Germany (AWMF) and the methodological requirements of the "German instrument for methodological guideline appraisal". Results: This consensus-based guideline (S2k classification according to the AWMF guidance manual and rules) resulted in seven on-topic statements and 17 specific recommendations relevant to the classification, assessment and therapy of pain directly or indirectly caused by SCI. Recommended therapeutic approaches comprise pharmacological (e.g. nonsteroidal anti-inflammatory drugs or anticonvulsants) and non-pharmacological (e.g. physical activity or psychotherapeutic techniques) strategies for both nociceptive and neuropathic pain. Discussion: Assessment of SCI-related pain is standardized and respective methods in terms of examination, classification and grading of pain are already in use and validated in German language. In contrast, valid, evidence-based and efficient therapeutic options are limited and ask for further clinical studies, ideally randomized controlled trials and meta-analyses.

Redox-enhanced hemilability of a tris(tert-butoxy)siloxy ligand at cerium.

The stabilizing effect of a tris(tert-butoxy)siloxy ligand on cerium(iv) is revealed by electrochemical and computation methods as well as by targeted redox chemistry. Ceric homoleptic complex Ce[OSi(OtBu)3]4 was obtained by the reaction of [Et4N]2[CeCl6] with NaOSi(OtBu)3 at ambient temperature in acetonitrile, while cerous ion-separated complex [Ce{OSi(OtBu)3}4][K(2.2.2-crypt)] was readily synthesized from [Ce{OSi(OtBu)3}4K] and cryptand. The solid-state structures of monocerium complexes Ce[OSi(OtBu)3]4 and Ce[OSi(OtBu)3]4(THF) show 5- and 6-coordinate CeIV centers (one κ2-bonded siloxy ligand), while complex [Ce{OSi(OtBu)3}4][K(2.2.2-crypt)] exhibits a 4-coordinate CeIII center (all-terminal siloxy coordination). A comparative electrochemical study of Ce[OSi(OtBu)3]4 and [Ce{OSi(OtBu)3}4][K(2.2.2-crypt)] suggests a redox-modulated molecular rearrangement process, featuring oxidation-state dependent formation and release of a CeOtBu coordination. While the overall stabilization of CeIV by the siloxy ligand is evident, significant extra stabilization is gained if the siloxy ligand coordinates in a chelating fashion, which is further supported by DFT calculations. Natural bond orbital (NBO) analysis indicates an enhanced donation of the siloxy ligand electron density into the unfilled CeIV 6s, 4f, and 5d orbitals. CeIV to CeIII reduction readily occurs when homoleptic complex Ce[OSi(OtBu)3]4 is treated with cobaltocene, affording the separated ion pair [Ce{OSi(OtBu)3}4][CoCp2], featuring exclusive terminal siloxy bonding in the solid-state, similar to that detected for [Ce{OSi(OtBu)3}4][K(2.2.2-crypt)].

Synthesis and derivatisation of ceric tris(tert-butoxy)siloxides.

Metathesis reactions involving cerium(iv) complexes are generally hampered by a high tendency for reduction to the favoured trivalent state and a preference for ligand redistribution. Heteroleptic ceric Ce[OSi(OtBu)3]3Cl(thf) is easily obtained from the oxidation of Ce[OSi(OtBu)3]3(thf)2 with trityl chloride, while the absence of thf triggers formation of homoleptic Ce[OSi(OtBu)3]4. Ce[OSi(OtBu)3]3Cl(thf) engages in salt metathesis reactions with the alkali metal alkoxides KOCH3 and KOtBu, forming Ce[OSi(OtBu)3]3(OR)(thf)x, but experiences an extensive reductive ligand redistribution with the methylating agent ZnMe2.

A Practical Example of GaN-LED Failure Cause Analysis by Application of Combined Electron Microscopy Techniques.

In this paper, we report a failure case of blue LEDs returned from a field application, and propose a practical way to identify the physical and structural reasons for the observed malfunction by a combination of different electron microscope techniques. Cathodoluminescence imaging and electron beam induced current (EBIC) imaging are employed in order to visualize conductive paths through the device in conjunction with subsequent energy dispersive x-ray analysis (EDS), revealing a metal deposition along cracks in the semiconductor layer which short-circuit the device. We demonstrate that the electron beam induced current imaging, in conjunction with other microscopic and analytical techniques at µm scale, is a powerful combination for clearly resolving and visualizing the cause of failure in the GaN LED chip. However, this represents a case study of a real application, which may not have been generally observed in laboratory testing environment.

Cerium(IV) Neopentoxide Complexes.

Treatment of ceric ammonium nitrate (CAN) with varying amounts of sodium neopentoxide led to the isolation of crystalline cerium(IV) complexes [Ce(OCH2tBu)2(NO3)2(HOCH2tBu)2], [Ce(OCH2tBu)3(NO3)-(NCCH3)]2, [Ce2(OCH2tBu)7(NO3)]2, and [Ce2(OCH2tBu)9Na-(THF)] featuring CeIV/(OR) ratios of 1:2, 1:3, 1:3.5, and 1:4.5, respectively. The complexes are light-sensitive and prone to ligand redistribution as evidenced by multicomponent NMR spectra as well as the formation of [{Ce(OCH2tBu)4}2(THF)] and the mixed-valent complex [Ce3(OCH2tBu)9(NO3)2]. The CAN protocol also gave access to the isopropoxide derivative [Ce(OiPr)3(NO3)(THF)]2. The reaction of [Et4N]2[CeCl6] (CAC, ceric organoammonium chloride) with different equivalents of Na(OCH2tBu) was also impaired by ligand reorganization and ate complexation as detected for the tetravalent cerium complex [Ce2(OCH2tBu)7Cl2][Et4N]. Protonolysis of [Ce{N(SiHMe2)2}4] with 4 equiv of HOCH2tBu afforded donor-free homoleptic [Ce(OCH2tBu)4]3 in quantitative yield. All complexes were characterized by NMR, DRIFT, and UV-vis spectroscopy, as well as paramagnetic susceptibility measurements, X-ray structure analysis, and elemental analysis.

Tracking the Magnetron Motion in FT-ICR Mass Spectrometry.

In Fourier transform ion cyclotron resonance spectrometry (FT-ICR MS) the ion magnetron motion is not usually directly measured, yet its contribution to the performance of the FT-ICR cell is important. Its presence is manifested primarily by the appearance of even-numbered harmonics in the spectra. In this work, the relationship between the ion magnetron motion in the ICR cell and the intensities of the second harmonic signal and its sideband peak in the FT-ICR spectrum is studied. Ion motion simulations show that during a cyclotron motion excitation of ions which are offset to the cell axis, a position-dependent radial drift of the cyclotron center takes place. This radial drift can be directed outwards if the ion is initially offset towards one of the detection electrodes, or it can be directed inwards if the ion is initially offset towards one of the excitation electrodes. Consequently, a magnetron orbit diameter can increase or decrease during a resonant cyclotron excitation. A method has been developed to study this behavior of the magnetron motion by acquiring a series of FT-ICR spectra using varied post-capture delay (PCD) time intervals. PCD is the delay time after the capture of the ions in the cell before the cyclotron excitation of the ion is started. Plotting the relative intensity of the second harmonic sideband peak versus the PCD in each mass spectrum leads to an oscillating "PCD curve". The position and height of minima and maxima of this curve can be used to interpret the size and the position of the magnetron orbit. Ion motion simulations show that an off-axis magnetron orbit generates even-numbered harmonic peaks with sidebands at a distance of one magnetron frequency and multiples of it. This magnetron offset is due to a radial offset of the electric field axis versus the geometric cell axis. In this work, we also show how this offset of the radial electric field center can be corrected by applying appropriate DC correction voltages to the mantle electrodes of the ICR cell while observing the signals of the second harmonic peak group. The field correction leads to a definite performance increase in terms of resolving power and mass accuracy, and the mass spectrum contains intensity-minimized even-numbered harmonics. This is very important in the case of high performance cells, particularly the dynamically harmonized cell, since the magnetron motion can severely impair the averaging effect for dynamic harmonization and can therefore reduce the resolving power.

Correlation of patient-related factors and dose-volume histogram parameters with the onset of radiation pneumonitis in patients with small cell lung cancer.

PURPOSE: To analyze the association of patient- and treatment-related factors with the onset of radiation pneumonitis in a homogeneously treated cohort of patients suffering from small cell lung cancer (SCLC). PATIENTS AND METHODS: 242 patients with SCLC staged as limited disease, who had been treated with chemotherapy and three-dimensional conformal radiotherapy, were retrospectively analyzed. Pneumonitis was defined by typical symptoms and radiographic findings and judged clinically relevant, if drug administration and hospitalization were necessary. Patient- (age, gender, smoking history, performance status, tumor localization, benign lung disease) and treatment-related parameters (V(10)-V(40), mean lung dose [MLD]) were analyzed using χ(2)-tests for categorical parameters and logistic regression for continuous variables. RESULTS: 33 patients (13.6%) developed a clinically relevant pneumonitis, of whom three patients died. All cases of pneumonitis developed within 120 days. None of the patient-related parameters correlated significantly with the onset of pneumonitis. Considering treatment-related parameters, a significant correlation of V(30) in regard to total lung and V(40) in regard to ipsilateral, contralateral and total lung to the risk of pneumonitis was found. So, the estimated risk of a clinically relevant pneumonitis increased from 10% given a V(30) of 13% to 30% given a V(30) of 35%. In contrast, no significant correlation was found for V(10) and V(20) and only a trend for MLD. CONCLUSION: In this series, high-dose radiation volume parameters, i.e., V(30) and especially V(40), were identified as the most important factors for the development of radiation pneumonitis. Low-dose radiation volume parameters and clinical parameters played an inferior role in predicting the pneumonitis risk.

Photoelectron spectroscopy of isolated multiply negatively charged oligonucleotides.

Ultraviolet photoelectron spectroscopy in an ion beam was used to investigate the electronic properties of isolated DNA oligonucleotides [dA(5)-4H](4-) and [dT(5)-4H](4-), carrying four excess negative charges. We find the fourth adiabatic electron affinity to be slightly negative for [dA(5)-4H](4-), while it is positive for [dT(5)-4H](4-). This implies a significant influence of the base composition on energetics, which is in turn relevant for analytic applications and also for charge transport properties.