Laser mass spectrometer

Development of time of flight mass spectrometer using laser powered vaporization source is discussed. Operation of equipment to measure thermal velocities of individual mass species is described. Illustration of test equipment installation and detailed line drawing of ion producing equipment are provided

Techniques for avoiding discrimination errors in the dynamic sampling of condensable vapors

In the mass spectrometric sampling of dynamic systems, measurements of the relative concentrations of condensable and noncondensable vapors can be significantly distorted if some subtle, but important, instrumental factors are overlooked. Even with in situ measurements, the condensables are readily lost to the container walls, and the noncondensables can persist within the vacuum chamber and yield a disproportionately high output signal. Where single pulses of vapor are sampled this source of error is avoided by gating either the mass spectrometer ""on'' or the data acquisition instrumentation ""on'' only during the very brief time-window when the initial vapor cloud emanating directly from the vapor source passes through the ionizer. Instrumentation for these techniques is detailed and its effectiveness is demonstrated by comparing gated and nongated spectra obtained from the pulsed-laser vaporization of several materials

Data acquisition techniques for exploiting the uniqueness of the time-of-flight mass spectrometer: Application to sampling pulsed gas systems

Mass spectra are produced in most mass spectrometers by sweeping some parameter within the instrument as the sampled gases flow into the ion source. It is evident that any fluctuation in the gas during the sweep (mass scan) of the instrument causes the output spectrum to be skewed in its mass peak intensities. The time of flight mass spectrometer (TOFMS) with its fast, repetitive mode of operation produces spectra without skewing or varying instrument parameters and because all ion species are ejected from the ion source simultaneously, the spectra are inherently not skewed despite rapidly changing gas pressure or composition in the source. Methods of exploiting this feature by utilizing fast digital data acquisition systems, such as transient recorders and signal averagers which are commercially available are described. Applications of this technique are presented including TOFMS sampling of vapors produced by both pulsed and continuous laser heating of materials

Deborah's law:The effects of naming and shaming on sex offenders n Australia

Arts, Education & Law Group, School of Criminology and Criminal JusticeNo Full Tex

Risk and resilience:Crime and violence prevention in Aboriginal communities

Developmental prevention involves the manipulation of multiple risk and protective factors early in developmental pathways that lead to offending, often at transition points between life phases. The emphasis is not just on individuals but also their social contexts. Risk and protective factors for crime and violence in Aboriginal communities include such standard factors as child abuse, school failure and supportive family environments, but additional factors arise from unique aspects of Aboriginal history, culture and social structure. This paper draws on existing literature, interviews with urban Aboriginal community workers, and data from the Sibling Study to delineate those interrelated risk factors (forced removals, dependence, institutionalised racism, cultural features and substance use) and the equally interrelated protective factors (cultural resilience, personal controls and family control measures). These are 'meta factors' that provide a lens through which the standard lists can be interpreted, and are a starting point for the understanding of indigenous developmental pathways.Arts, Education & Law Group, School of Criminology and Criminal JusticeFull Tex

Strong Phases in the Decays B to pi pi

Two sources of strong phases in the decays $B$ to $\pi\pi$ are identified: (1) "quasi-elastic scattering" corresponding to intermediate states like $\pi\pi$ and $\rho\rho$, (2) ``$c\bar{c}$'' corresponding to intermediate states like $D\bar{D}$ and $D^{*}\bar{D}^{*}$. Possibilities of using data to identify these two sources are discussed and illustrated. Present data suggests both sources may be significant.Comment: 6 pages, 1 figure

Vortex macroscopic superpositions in ultracold bosons in a double-well potential

We study macroscopic superpositions in the orbital rather than the spatial degrees of freedom, in a three-dimensional double-well system. We show that the ensuing dynamics of $N$ interacting excited ultracold bosons, which in general requires at least eight single-particle modes and ${N+7 \choose N}$ Fock vectors, is described by a surprisingly small set of many-body states. An initial state with half the atoms in each well, and purposely excited in one of them, gives rise to the tunneling of axisymmetric and transverse vortex structures. We show that transverse vortices tunnel orders of magnitude faster than axisymmetric ones and are therefore more experimentally accessible. The tunneling process generates macroscopic superpositions only distinguishable by their orbital properties and within experimentally realistic times.Comment: 9 pages, 6 figure