A. Rayner

Laser cooling of a solid from ambient temperature

Abstract A 250 μm diameter fibre of ytterbium-doped ZBLAN was cooled by 13 K from room temperature. The cooling was performed in vacuum to limit the thermal load on the fibre. 0.85 W of laser light at 1015 nm was coupled into the fibre. The ytterbium ions absorbed this light, and the excited atoms thermalized phononically and on average emitted light at a wavelength of 996 nm. Since the quantum efficiency of the transition was high, this resulted in a net loss of energy from the glass, producing net bulk cooling.

Condensed-phase optical refrigeration

We review progress on laser cooling of solids. The general process that enables cooling to occur is based on anti-Stokes fluorescence. Candidate materials for laser cooling are discussed, including gases, dyes, crystals, semiconductors, and ionically doped glasses. Cooling processes and necessary conditions for cooling are outlined, and general thermodynamic limitations are discussed. This is followed by a more detailed discussion of one specific material, ytterbium-doped ZBLAN, with consideration given to optimization of the laser cooling process and applications.

What does a physics undergraduate education give you? A perspective from Australian physics

In a study to assess how effectively undergraduate physics studies have prepared students for the workplace, we attempted to locate and interview traditional 3-year or 4-year physics students who had graduated in the past five years (2000 to 2004), and the employers of these graduates. The study was limited to recent graduates who have majored in physics and not obtained further or concurrent degrees. Overseas studies of the destinations of physics graduates referred to in this paper have not isolated the group we interviewed as a distinct group. A major finding was that the number of these graduates was unexpectedly low. Indeed, most physics graduates have two degrees. Interviews with graduates and employers suggest that physics graduates have particular strengths in problem solving and are good at applying their skills at the workplace.

Distributed laser refrigeration

A 250-mum-diameter fiber of ytterbium-doped ZBLAN (fluorine combined with Zr, Ba, La, Al, and Na) has been cooled from room temperature. We coupled 1.0 W of laser light from a 1013-nm diode laser into the fiber. We measured the temperature of the fiber by using both fluorescence techniques and a microthermocouple. These microthermocouple measurements show that the cooled fiber can be used to refrigerate materials brought into contact with it. This, in conjunction with the use of a diode laser as the light source, demonstrates that practical solid-state laser coolers can be realized.

The analgesic effect of interferential therapy on clinical and experimentally induced pain

Abstract Background: Interferential therapy (IFT) is one of the most popular modalities used by physiotherapists for the management and control of pain. Despite its widespread use, there remains debate surrounding its effectiveness. Objectives: The aim of this systematic review was to evaluate the published literature on the effectiveness of IFT in reducing pain. Method: A literature search of Cochrane Central Register of Controlled Trials, Medical Literature Analysis and Retrieval System Online (MEDLINE), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Excerpta Medica Database (EMBASE), and Physiotherapy Evidence Based (PEDro) was performed. This review adhered only to randomised controlled trials (RCTs) that investigated IFT in the presence of a control group. PEDro scale was used to assess the methodological quality of the included studies. Results: Nine RCTs met the inclusion criteria of this review. One study evaluated the effect of IFT on clinical pain while remaining studies examined induced pain including thermal (cold and hot), ischemic, mechanical, and delayed onset of muscle soreness. No clear conclusion was withdrawn regarding the effectiveness of IFT on pain management due to the high variability in study design and deficiencies in methodological quality. The data were limited and contradicting and therefore, of equivocal support to the pain reduction effect of IFT. Conclusion: There is inadequate evidence to support the effectiveness of IFT in pain management. Clearly, there is a need for RCTs with high methodological quality to establish IFT efficacy.