A field ionizer for photodetachment studies of negative ions.

In this paper, we present an apparatus for studies into the photodetachment process of atomic negative ions. State-selective detection of the residual atom following the initial photodetachment step is achieved by combining resonant laser excitation of the photo-detached atom with electric field ionization. The resonance ionization technique in combination with a co-linear ion-laser beam geometry gives an experimental apparatus that has both high selectivity and sensitivity. In addition to measurements of a single selected partial photodetachment channel, the apparatus also can be used to study a manifold of photodetachment channels in which the residual atom is left in a high-lying Rydberg state and for investigation of the double electron-detachment process. Ion-optical simulations in SIMION are used to illustrate the operation of the apparatus for studying such processes. Successful performance of the apparatus against the simulation is demonstrated by a high resolution study of the photodetachment of cesium, where the sharp s-wave threshold of the photodetachment processes leaving the residual atom in the excited 6p state was investigated.

Threshold photodetachment in a repulsive potential.

We report on the first experimental observation of a new threshold behavior observed in the 5(2)G partial channel in photodetachment of K(-). It arises from the repulsive polarization interaction between the detached electron and the residual K(5(2)G) atom, which has a large negative dipole polarizability. In order to account for the observation in the K(5(2)G) channel, we have developed a semiclassical model that predicts an exponential energy dependence for the cross section. The measurements were made with collinear laser-ion beams and a resonance ionization detection scheme.

A national survey of instrument sharpening guidelines.

Most orthopaedic procedures involve high-speed tools, which can cause thermal necrosis of bone. Blunt instruments are likely to generate more heat, thereby increasing the chances of thermal necrosis. This could greatly compromise the outcome of even the best prosthesis in good surgical hands. In today's age a lot of emphasis is laid on high performance and longevity of the implant. Therefore, it is worthwhile that we consider the relevance and importance of instrument sharpening. We carried out a survey across hospitals in UK to find out whether they follow any guidelines or protocol with regards to instrument sharpening. Upto 75% of hospitals did not follow any guideline or policy, while 20% of hospitals carried out some sort of quality checks on instruments. This implies that there could be a significant risk of suboptimal outcome due to unnecessary osteonecrosis that can affect most operative orthopaedic interventions, particularly joint arthroplasties. Blunt instruments are too common in orthopaedic theatres and this problem needs to be addressed. Our study brings to light the fact that there seems to be no consensus on this issue and there is theoretically a significant risk of suboptimal outcome because of unnecessary osteonecrosis. This potentially may affect the long and short-term results even in good hands and with excellent prosthesis (cemented or uncemented).

The risk of cross-infection when marking surgical patients prior to surgery - review of two types of marking pens.

INTRODUCTION: Two types of marker pens were compared to find whether they produced different risks of infection transmission over different time intervals. PATIENTS AND METHODS: Twenty-four patients were marked according to the type of surgery: each had a set of new dry white-board marker (DWM) and a permanent marker (PM) pen. Once used, their tips were used to inoculate blood agar plates at different time intervals. RESULTS: At 0 min, 96% of the DWM pens and 29% of the PM pens were positive of growth. At 3 and 10 min, all of the DWM pens remained positive. The rate dropped to 16.67% in 3 min down to none at 10 min for the PM pens. CONCLUSIONS: DWM pens carry a significant risk of transmitting infection between patients. It is recommended that they are not used in marking. PM pens should not be used between patients in less than a 10-min interval.

Radiative lifetime of a bound excited state of Te-.

We report on the first experimental study of the lifetime of a bound excited state of a negative ion. A new experimental technique was developed and used to measure the radiative lifetime of the 5p(5) (2)P(1/2) level of Te-. The experiment was performed in a magnetic storage ring, where a laser beam was applied along one of the straight sections. In the experiment the population of the excited J=1/2 level was probed each time the Te- ions passed through the laser field. A decay curve was built up by sampling the population of the excited level of the Te- ions as a function of time after injection into the ring. A multiconfiguration Dirac-Hartree-Fock calculation was performed in conjunction with the experiment. The calculation yielded a radiative lifetime of 0.45 s, in excellent agreement with the measured value of 0.42(5) s.

Spectrum of doubly excited states in the K- ion.

The energies and widths of doubly excited states of the K- ion in the vicinity of the K(5 2D,7 2S,5 2F) thresholds have been measured in high resolution using a sensitive collinear laser-ion beam apparatus. These transient states appeared as resonances in the partial cross section for photodetachment via the K(5 2S)+e(-)(epsilon(p)) channel. Series of two states below the 5 2D threshold and four states below the 5 2F threshold have been found. The relative widths of members of the series below the 5 2F threshold exhibit anomalous behavior, as predicted by a semiclassical model.

Gastrointestinal obstruction associated with Chlamydia trachomatis.

A patient is reported in whom adhesive obstruction of the small bowel was due to generalised peritonitis caused by Chlamydia trachomatis. It is concluded that any sexually active female with unexplained peritonitis or adhesive obstruction of the small bowel should be screened for chlamydial infection.