Determining the dimension of iterative Hessian transformation

The central mean subspace (CMS) and iterative Hessian transformation (IHT) have been introduced recently for dimension reduction when the conditional mean is of interest. Suppose that X is a vector-valued predictor and Y is a scalar response. The basic problem is to find a lower-dimensional predictor \eta^TX such that E(Y|X)=E(Y|\eta^TX). The CMS defines the inferential object for this problem and IHT provides an estimating procedure. Compared with other methods, IHT requires fewer assumptions and has been shown to perform well when the additional assumptions required by those methods fail. In this paper we give an asymptotic analysis of IHT and provide stepwise asymptotic hypothesis tests to determine the dimension of the CMS, as estimated by IHT. Here, the original IHT method has been modified to be invariant under location and scale transformations. To provide empirical support for our asymptotic results, we will present a series of simulation studies. These agree well with the theory. The method is applied to analyze an ozone data set.Comment: Published at http://dx.doi.org/10.1214/009053604000000661 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Untersuchungen zur Mehrstufen-Laserspektroskopie an gespeicherten H3+ -Molekülionen

Das dreiatomige H3+ -Molekülion hat durch seine regelmäßige dreieckige Struktur eine besondere Bedeutung in der molekularen Quantendynamik. Viele Molekülreaktionen wurden bisher an H3+ untersucht, so auch die dissoziative Rekombination im Speicherring mit einem kalten Elektronenstrahl. Bei diesen stark energieabhängigen Reaktionen ist die Besetzung einzelner Rovibrationsniveaus von großer Bedeutung. Zur Bestimmung solcher Besetzungen der H3+ -Ionen innerhalb eines Speicherrings muss eine extrem empfi ndliche zustandsselektive Nachweismethode verwendet werden. Das angestrebte Verfahren ist die resonant-erhöhte multi-Photonen-Dissoziation (REMPD), bei der in einem resonanten ersten Schritt die Moleküle aus dem tief liegenden Niveau hoch angeregt werden und danach in einem zweiten Schritt aus diesen hochangeregten Zuständen photodissoziiert werden. Um diese Methode anwenden zu können, sind detaillierte Voruntersuchungen nötig. Hier werden Messungen präsentiert, die den Energiebereich der dissoziierbaren hochangeregten Schwingungszustände von heißen H3+ -Molekülionen in einem Experiment mit schnellen Ionenstrahlen bestimmen. Ebenso wird ein Photodissoziationsexperiment an heißen H3+ -Ionen im Speicherring TSR am Max-Planck-Institut für Kernphysik durchgeführt und eine effektive Lebensdauer der dissoziierten H3+ -Zustände gemessen. Schließlich wird die gezielte Photoanregung kalter H3+ -Ionen (erster REMPD-Schritt) in sehr hochangeregte Zustände im Bereich der dissoziierbaren Schwingungsniveaus untersucht

Chemical probing spectroscopy of H3+ above the barrier to linearity

We have performed chemical probing spectroscopy of H3+ ions trapped in a cryogenic 22-pole ion trap. The ions were buffer-gas cooled to 55K by collisions with helium and argon. Excitation to states above the barrier to linearity was achieved by a Ti:Sa laser operated between 11300 and 13300 cm-1. Subsequent collisions of the excited H3+ ions with argon lead to the formation of ArH+ ions that were detected by a quadrupole mass spectrometer with high sensitivity. We report the observation of 17 previously unobserved transitions to states above the barrier to linearity. Comparison to theoretical calculations suggests that the transition strengths of some of these lines are more than five orders of magnitude smaller than those of the fundamental band, which renders them - to the best of our knowledge - the weakest H3+ transitions observed to date.Comment: 22 pages, 5 figures, submitted to JC

A Stimulated Emission Study of the Ground State Bending Levels of BH\u3csub\u3e2\u3c/sub\u3e Through the Barrier to Linearity and \u3cem\u3eAb Initio\u3c/em\u3e Calculations of Near-Spectroscopic Accuracy

The ground state bending levels of 11BH2 have been studied experimentally using a combination of low-resolution emission spectroscopy and high-resolution stimulated emission pumping (SEP) measurements. The data encompass the energy range below, through, and above the calculated position of the barrier to linearity. For the bending levels (0,3,0) and above, the data show substantial K-reordering, with the K a = 1 levels falling well below those with K a = 0. A comparison of the high-resolution rotationally resolved SEP data to our own very high level ab initio calculations of the rovibronic energy levels shows agreement approaching near-spectroscopic accuracy (a few cm−1). The data reported in this work provide very stringent tests for future theoretical treatments of this prototypical seven-electron free radical

Applied Quantum Chemistry: Spectroscopic Detection and Characterization of the F\u3csub\u3e2\u3c/sub\u3eBS and Cl\u3csub\u3e2\u3c/sub\u3eBS Free Radicals in the Gas Phase

In this and previous work [D. J. Clouthier, J. Chem. Phys. 141, 244309 (2014)], the spectroscopic signatures of the X2BY (X = H, halogen, Y = O, S) free radicals have been predicted using high level ab initio theory. The theoretical results have been used to calculate the electronic absorption and single vibronic level (SVL) emission spectra of the radicals under typical jet-cooled conditions. Using these diagnostic predictions, the previously unknown F2BS and Cl2BS free radicals have been identified and characterized. The radicals were prepared in a free jet expansion by subjecting precursor mixtures of BF3 or BCl3 and CS2 vapor to an electric discharge at the exit of a pulsed molecular beam valve. The B̃2A1-X̃2B2 laser-induced fluorescence spectra were found within 150 cm-1 of their theoretically predicted positions with vibronic structure consistent with our Franck-Condon simulations. The B̃2A1 state emits down to the ground state and to the low-lying Ã2B1 excited state and the correspondence between the observed and theoretically derived SVL emission Franck-Condon profiles was used to positively identify the radicals and make assignments. Excited state Coriolis coupling effects complicate the emission spectra of both radicals. In addition, a forbidden component of the electronically allowed B̃-X̃ band system of Cl2BS is evident, as signaled by the activity in the b2 modes in the spectrum. Symmetry arguments indicate that this component gains intensity due to a vibronic interaction of the B̃2A1 state with a nearby electronic state of 2B2 symmetry

Nanoscale surface element identification and dopant homogeneity in the high-TcT_{c} superconductor PrxCa1−xFe2As2Pr_xCa_{1−x}Fe_2As_2

We use scanning tunneling microscopy to determine the surface structure and dopant distribution in $Pr_xCa_{1−x}Fe_2As_2$, the highest-Tc member of the 122 family of iron-based superconductors. We identify the cleaved surface termination by mapping the local tunneling barrier height, related to the work function. We image the individual Pr dopants responsible for superconductivity, and show that they do not cluster, but in fact repel each other at short length scales. We therefore suggest that the low volume fraction high-Tc superconducting phase is unlikely to originate from Pr inhomogeneity.Physic

Test of Time Dilation Using Stored Li+ Ions as Clocks at Relativistic Speed

We present the concluding result from an Ives-Stilwell-type time dilation experiment using 7Li+ ions confined at a velocity of beta = v/c = 0.338 in the storage ring ESR at Darmstadt. A Lambda-type three-level system within the hyperfine structure of the 7Li+ triplet S1-P2 line is driven by two laser beams aligned parallel and antiparallel relative to the ion beam. The lasers' Doppler shifted frequencies required for resonance are measured with an accuracy of < 4 ppb using optical-optical double resonance spectroscopy. This allows us to verify the Special Relativity relation between the time dilation factor gamma and the velocity beta to within 2.3 ppb at this velocity. The result, which is singled out by a high boost velocity beta, is also interpreted within Lorentz Invariance violating test theories

Inhibition of chemotherapy resistant breast cancer stem cells by a ROR1 specific antibody.

Breast cancers enduring treatment with chemotherapy may be enriched for cancer stem cells or tumor-initiating cells, which have an enhanced capacity for self-renewal, tumor initiation, and/or metastasis. Breast cancer cells that express the type I tyrosine kinaselike orphan receptor ROR1 also may have such features. Here we find that the expression of ROR1 increased in breast cancer cells following treatment with chemotherapy, which also enhanced expression of genes induced by the activation of Rho-GTPases, Hippo-YAP/TAZ, or B lymphoma Mo-MLV insertion region 1 homolog (BMI1). Expression of ROR1 also enhanced the capacity of breast cancer cells to invade Matrigel, form spheroids, engraft in Rag2-/-[Formula: see text] mice, or survive treatment with paclitaxel. Treatment of mice bearing breast cancer patient-derived xenografts (PDXs) with the humanized anti-ROR1 monoclonal antibody cirmtuzumab repressed expression of genes associated with breast cancer stemness, reduced activation of Rho-GTPases, Hippo-YAP/TAZ, or BMI1, and impaired the capacity of breast cancer PDXs to metastasize or reengraft Rag2-/-[Formula: see text] mice. Finally, treatment of PDX-bearing mice with cirmtuzumab and paclitaxel was more effective than treatment with either alone in eradicating breast cancer PDXs. These results indicate that targeting ROR1 may improve the response to chemotherapy of patients with breast cancer