Isotope shift in the electron affinity of chlorine

The specific mass shift in the electron affinity between ^{35}Cl and ^{37}Cl has been determined by tunable laser photodetachment spectroscopy to be -0.51(14) GHz. The isotope shift was observed as a difference in the onset of the photodetachment process for the two isotopes. In addition, the electron affinity of Cl was found to be 29138.59(22) cm^{-1}, giving a factor of 2 improvement in the accuracy over earlier measurements. Many-body calculations including lowest-order correlation effects demonstrates the sensitivity of the specific mass shift and show that the inclusion of higher-order correlation effects would be necessary for a quantitative description.Comment: 16 pages, 6 figures, LaTeX2e, amsmat

Inhibitory Receptors Alter Natural Killer Cell Interactions with Target Cells Yet Allow Simultaneous Killing of Susceptible Targets

Inhibitory receptors expressed on natural killer (NK) cells abrogate positive signals upon binding corresponding major histocompatibility complex (MHC) class I molecules on various target cells. By directly micromanipulating the effector–target cell encounter using an optical tweezers system which allowed temporal and spatial control, we demonstrate that Ly49–MHC class I interactions prevent characteristic cellular responses in NK cells upon binding to target cells. Furthermore, using this system, we directly demonstrate that an NK cell already bound to a resistant target cell may simultaneously bind and kill a susceptible target cell. Thus, although Ly49-mediated inhibitory signals can prevent many types of effector responses, they do not globally inhibit cellular function, but rather the inhibitory signal is spatially restricted towards resistant targets

Improved theory of laser-enhanced ionization in flames: comparison with experiment

An improved theory for laser enhanced ionization in flames has been developed for one‐ and two‐step laser excitations. The model gives an analytical expression for the sensitivity of the method for a given transition of any element. The theoretical expression is compared with experimentally measured signals for a number of elements and the agreement is found to be generally good

Laser frequency stabilization based on a universal sub-Doppler NICE-OHMS instrumentation for the potential application in atmospheric lidar

Lidar is an effective tool for high-altitude atmospheric measurement in which a weak absorption line for the target gas is selected to ensure a large optical depth. The laser frequency stabilization to the line center is required, and a sub-Doppler (sD) spectroscopy of the target line is preferred as a frequency reference. In this paper, a novel universal sD noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) instrumentation based on a fiber-coupled optical single-sideband electro-optic modulator (f-SSM) for the potential application in atmospheric lidar for different target gases with different types of lasers is reported. The f-SSM can replace all frequency actuators in the system, so as to eliminate the individual design of feedback servos that often are tailored for each laser. The universality of the instrumentation was demonstrated by the alternative use of either an Er-doped fiber laser or a whispering-gallery-mode laser. Then the instruments based on both lasers were used to produce the sD signals of acetylene, which worked as a frequency reference to stabilize the laser. By performing the lockings, relative frequency stabilizations of 8.3×10-13 and 7.5×10-13 at an integration time of 240&thinsp;s were demonstrated.</p

Simulating Time Harmonic Flows with the Lattice Boltzmann Method

We simulate time harmonic flows by the lattice Boltzmann method. We propose a general scheme to choose simulation parameters, under the constraints of fixed Reynolds and Womersley numbers, and with a specified simulation error. Under these constraints parameters are chosen to minimize the execution time. Numerical stability is studied in a range of Reynolds and Womersley numbers. As an example of time harmonic flow simulations, results of blood flow in a human abdominal aorta are presented.Published versio

Monotricat® hull, first displacement naval hull navigating at speeds of planing hulls, on spray self-produced, at high hydrodynamic efficiency and energy recovery

From the '50s, with the introduction of the first semi-planing hull of Nelson, which allowed to navigate with a certain tranquility at speeds higher than those of traditional hulls, and with the subsequent availability of more powerful engines, have been reached a speed equal to Fn greater than 0.6, which defines planing hulls. It was created so a clear distinction between displacement and planing hulls, in relation to the performances. The need to have naval units displacing faster has pushed the ship design to achieve increasingly high performance hulls, also focusing on the use of lightweight materials such as aluminum and more powerful engines, etc., but without substantially changing the traditional forms of hull. The patented hull Monotricat high hydrodynamic efficiency and energy saving represents the overcoming of this distinction between displacement and planing hulls, because, unlike previous solutions, is configured as the first hull that combines the characteristics of displacement and planning hull, since it presents an innovative architecture that could be defined as a hybrid between a monohull and catamaran, navigating on spray self-produced. This presentation will show how the hull Monotricat is the first displacement hull that can navigate at both displacement and planning speeds, with a resistance curve almost straight, maintaining the characteristics of a displacement hull. For these reasons the Monotricat hull is able to ensure: safety, comfort navigation, best seakeeping and maneuverability in restricted waters, stability, reduction of resistance to motion, cost management, regularity on the routes even in adverse weather-sea. These characteristics of the hull have been studied, tested and validated by leading research institutes and universities with more ameliorative results in each subsequent experimentation, reported in the present work, which demonstrated a greater hydrodynamic efficiency compared to conventional hulls tending to 20%.</p

The use of autoionizing states for efficient detection of Sr in Resonance Ionization Mass-Spectrometry

An efficient excitation scheme for RIMS of Sr has been investigated. Two - colour excitation has been used for excitation of the atoms to an autoionization level with both transitions in the visible region. The first step excitation was at 460.733 nm (5s2 1S0 --> 5s5p 1P1) and the second step leading to ionization was at 405.32 nm which connects the first excited state with a 1D2 autoionizing state at 46380 cm-1. This type of RIMS excitation scheme ensures selectivity in both steps as well as an efficient degree of ionization. The choice of the visible wavelengths helps also to minimize the influence of spectral interferences as well as wing excitations of matrix species