Solidification of undercooled liquids

During rapid solidification processing (RSP) the amount of liquid undercooling is an important factor in determining microstructural development by controlling phase selection during nucleation and morphological evolution during crystal growth. While undercooling is an inherent feature of many techniques of RSP, the deepest undercoolings and most controlled studies have been possible in carefully prepared fine droplet samples. From past work and recent advances in studies of nucleation kinetics it has become clear that the initiation of crystallization during RSP is governed usually by heterogeneous sites located at surfaces. With known nucleant sites, it has been possible to identify specific pathways of metastable phase formation and microstructural development in alloys. These advances have allowed for a clearer assessment of the interplay between undercooling, cooling rate and particle size statistics in structure formation. New approaches to the examination of growth processes have been developed to follow the thermal behavior and morphology in small samples in the period of rapid crystallization and recalescence. Based upon the new experimental information from these studies, useful models can be developed for the overall solidification process to include nucleation behavior, thermodynamic constraints, thermal history, growth kinetics, solute redistribution and resulting structures. From the refinement of knowledge concerning the underlying factors that govern RSP a basis is emerging for an effective alloy design and processing strategy

Retraction Note: An apoptosis-enhancing drug overcomes platinum resistance in a tumour-initiating subpopulation of ovarian cancer.

This Article has been retracted; see accompanying Retraction Note

A Historical Analysis of Southeast Asian Refugee Communities: Post-war Acculturation and Education in the U.S.

This analysis considers the circumstances of Southeast Asian refugee immigration following the Vietnam War as well as the political and social environment in the US upon their arrival, in order to examine the historical factors that link to their subsequent educational trends. Receptive government policies enabled these communities to survive; however, with the exception of first-wave Vietnamese refugees, their limited job skills, English language knowledge, and education upon arrival were exacerbated by overall prejudiced societal reception and the lack of an existing co-ethnic community to buffer their entry into US society. All groups have generally experienced low academic achievement except in the case of Vietnamese Americans, for whom a notable contingent demonstrates higher attainment. Implications for subsequent generations, and for research and practice, are discussed

Quartz crystal microbalance use in biological studies

Design, development, and applications of quartz crystal microbalance are discussed. Two types of crystals are used. One serves as reference and other senses changes in mass. Specific application to study of bacterial spores is described

Poor survival outcomes in HER2 positive breast cancer patients with low grade, node negative tumours

We present a retrospective analysis on a cohort of low-grade, node-negative patients showing that human epidermal growth factor receptor 2 (HER2) status significantly affects the survival in this otherwise very good prognostic group. Our results provide support for the use of adjuvant trastuzumab in patients who are typically classified as having very good prognosis, not routinely offered standard chemotherapy, and who as such do not fit current UK prescribing guidelines for trastuzumab

T1T_1- and T2T_2-spin relaxation time limitations of phosphorous donor electrons near crystalline silicon to silicon dioxide interface defects

A study of donor electron spins and spin--dependent electronic transitions involving phosphorous ($^{31}$P) atoms in proximity of the (111) oriented crystalline silicon (c-Si) to silicon dioxide (SiO$_{2}$) interface is presented for [$^{31}$P] = 10$^{15}$ $\mathrm{cm}^{-3}$ and [$^{31}$P] = 10$^{16}$ $\mathrm{cm}^{-3}$ at about liquid $^4$He temperatures ($T = 5$ $\mathrm{K} - 15$ $\mathrm{K}$). Using pulsed electrically detected magnetic resonance (pEDMR), spin--dependent transitions between the \Phos donor state and two distinguishable interface states are observed, namely (i) \Pb centers which can be identified by their characteristic anisotropy and (ii) a more isotropic center which is attributed to E$^\prime$ defects of the \sio bulk close to the interface. Correlation measurements of the dynamics of spin--dependent recombination confirm that previously proposed transitions between \Phos and the interface defects take place. The influence of these electronic near--interface transitions on the \Phos donor spin coherence time $T_2$ as well as the donor spin--lattice relaxation time $T_1$ is then investigated by comparison of spin Hahn--echo decay measurements obtained from conventional bulk sensitive pulsed electron paramagnetic resonance and surface sensitive pEDMR, as well as surface sensitive electrically detected inversion recovery experiments. The measurements reveal that both $T_2$ and $T_1$ of \Phos donor electrons spins in proximity of energetically lower interface states at $T\leq 13$ K are reduced by several orders of magnitude

Comparison of coherence times in three dc SQUID phase qubits

We report measurements of spectroscopic linewidth and Rabi oscillations in three thin-film dc SQUID phase qubits. One device had a single-turn Al loop, the second had a 6-turn Nb loop, and the third was a first order gradiometer formed from 6-turn wound and counter-wound Nb coils to provide isolation from spatially uniform flux noise. In the 6 - 7.2 GHz range, the spectroscopic coherence times for the gradiometer varied from 4 ns to 8 ns, about the same as for the other devices (4 to 10 ns). The time constant for decay of Rabi oscillations was significantly longer in the single-turn Al device (20 to 30 ns) than either of the Nb devices (10 to 15 ns). These results imply that spatially uniform flux noise is not the main source of decoherence or inhomogenous broadening in these devices.Comment: 4 pages, 5 figures, accepted for publication in IEEE Trans. Appl. Supercon

Strong-field effects in the Rabi oscillations of the superconducting phase qubit

Rabi oscillations have been observed in many superconducting devices, and represent prototypical logic operations for quantum bits (qubits) in a quantum computer. We use a three-level multiphoton analysis to understand the behavior of the superconducting phase qubit (current-biased Josephson junction) at high microwave drive power. Analytical and numerical results for the ac Stark shift, single-photon Rabi frequency, and two-photon Rabi frequency are compared to measurements made on a dc SQUID phase qubit with Nb/AlOx/Nb tunnel junctions. Good agreement is found between theory and experiment.Comment: 4 pages, 4 figures, accepted for publication in IEEE Trans. Appl. Supercon

Matching-Adjusted Indirect Comparison (MAIC) of Tepotinib with Other MET Inhibitors for the Treatment of Advanced NSCLC with MET Exon 14 Skipping Mutations

Introduction MET exon 14 skipping in patients with advanced non-small cell lung cancer (aNSCLC), can be targeted with MET inhibitors including tepotinib, capmatinib, savolitinib, and crizotinib. Matching-adjusted indirect comparison (MAIC) methodology was used to compare outcomes data between agents and to address bias from differences in baseline characteristics. Methods Patient-level data from the VISION study (tepotinib) were weighted for comparison with aggregate data from the GEOMETRY mono-1 (capmatinib), NCT02897479 (savolitinib) and PROFILE 1001 (crizotinib) studies in patients with aNSCLC, using baseline characteristics prognostic for overall survival (OS) in VISION. Overall response rate (ORR), OS, progression-free survival (PFS), and duration of response (DOR) were compared. Patients were stratified by line of therapy: overall (all lines), previously treated, and treatment-naive. Results Improvements in ORR and all time-to-event endpoints were predicted for tepotinib compared with crizotinib and savolitinib in the different populations, although comparisons with savolitinib were hindered by considerable differences in baseline patient populations. Tepotinib appeared to be associated with prolonged PFS and OS compared with capmatinib in previously treated patients (PFS HR 0.54; 95% CI 0.36-0.83; OS HR 0.66; 95% CI 0.42-1.06) and the overall populations (PFS HR 0.60; 95% CI 0.43-0.86; OS HR 0.72; 95% CI 0.49-1.05), with smaller improvements in DOR. The ORR comparisons between tepotinib and capmatinib identified a swing of up to +/- 6 percentage points in the weighted tepotinib ORR depending on the population studied (treatment-naive vs. previously treated patients). Conclusions The MAIC identified potential differences in efficacy endpoints with the different MET inhibitors, and predicted prolonged PFS and OS with tepotinib compared with capmatinib and crizotinib. Although MAIC cannot balance for unobserved factors, it remains an informative method to contextualize single-arm studies, where head-to-head trials are unlikely to be feasible