Measurement of pressure and assessment of cavitation for a 22.5-kHz intra-arterial angioplasty device

This study was performed to understand better the mechanisms of action of an (22.5 kHz) ultrasonic wire catheter device used to remove atheromatous plaque in diseased blood vessels (ultrasonic angioplasty). During a clinical procedure, the wire acts as an acoustic waveguide to transfer acoustic energy from a generator outside the body to the ball tip of the wire, which is inserted in the blood vessel. The acoustic field radiated by the vibrating ball tip (1.5- to 3.0-mm diameter), was mapped in a relatively large (600 L) water tank and compared to the field from a well-characterized simple source. A dipolelike radiation pattern due to the translating ball tip was observed. At low power settings, standing wave effects in a smaller cylindrical volume (200-mm diameter, 350-mm height), which was used to simulate anthropometric dimensions, increase relative to the larger tank measurements. The standing wave ratio is dependent upon the pc characteristics of the medium and the dimensions of the volume, rather than on the absorption at this frequency. At high power-settings of the device, cavitation at the tip of the wire was measured using a 20-MHz passive cavitation detection scheme

Combating corruption through employment law and whistleblower protection.

This article examines the extent to which employment law has the potential to fight corruption by imposing rights and duties on employers and workers and analyses the extent to which the UN Convention on Corruption 2003 (UNCAC) protects those who speak out about malpractices within an organisation. Section 2 focuses on UNCAC while Section 3 focuses on the extent to which employment law imposes obligations on those within the workplace to report corrupt activities and the circumstances in which those who speak out about corruption are protected under UK employment law. It is argued that because of the inadequacies of the existing legislation and the threat posed by disclosures via the Internet, organisations have much to gain from devising effective policies on both internal and external reporting that do not inhibit the exposure of corruption or unnecessarily curtail freedom of speech. The authors conclude by welcoming the draft recommendations from the Council of Europe’s Parliamentary Assembly to draw up a set of guidelines for the protection of whistleblowers and consider drafting a framework convention

Growth of primordial black holes in a universe containing a massless scalar field

The evolution of primordial black holes in a flat Friedmann universe with a massless scalar field is investigated in fully general relativistic numerical relativity. A primordial black hole is expected to form with a scale comparable to the cosmological apparent horizon, in which case it may go through an initial phase with significant accretion. However, if it is very close to the cosmological apparent horizon size, the accretion is suppressed due to general relativistic effects. In any case, it soon gets smaller than the cosmological horizon and thereafter it can be approximated as an isolated vacuum solution with decaying mass accretion. In this situation the dynamical and inhomogeneous scalar field is typically equivalent to a perfect fluid with a stiff equation of state $p=\rho$. The black hole mass never increases by more than a factor of two, despite recent claims that primordial black holes might grow substantially through accreting quintessence. It is found that the gravitational memory scenario, proposed for primordial black holes in Brans-Dicke and scalar-tensor theories of gravity, is highly unphysical.Comment: 24 pages, accepted for publication in Physical Review

Handheld computers: Do they support or constrain nursing students at the point -of -care?

Technology has made a significant impact within the healthcare system over recent years. As technology continues to evolve and becomes a major driving force within the healthcare system, so will the need for preparing technologically competent healthcare professionals. Also within the healthcare system, changes such as a decrease in the length of hospital stay, the aging population, and the multi-disease processes of the aging population, presents a challenge to nursing faculty to adequately prepare tomorrows\u27 nurse. One of the most promising technological devices being used by healthcare professionals is the handheld computer or personal digital assistant (PDA). Although the current literature supports the use of the PDA by practicing nurses and nursing students, little is known how to incorporate these devices to support and develop life-long learners; A mixed-method design directed this study. Biemiller & Meichenbaum\u27s Think-Aloud was conducted at the onset and conclusion of the study. A grounded theory approach was utilized to gather data pertaining to PDAs and nursing students. Upon observing the participant accessing the PDA, a semi-structured interview occurred. The last component of data collection was obtained via a tracking system on a nursing focused PDA software program; The results demonstrate that the PDA supports self-regulated/self-directed learning in nursing students. Biemiller & Meichenbaum\u27s Think-Aloud demonstrated that all participants increased in their ability to be self-directed learners at the conclusion of the study. Furthermore, the results demonstrated that students are accessing the PDA in the clinical site, in the classroom, in studying for test/exams, and when completing assignments. Although the age varied for the participants, the method preferred for learning was from the screen; Pintrich\u27s self-regulated learning model was used as a method of determining the extent and progression of identifying self-regulated learners. Again, the results displayed that the PDA supported the participant in becoming self-regulated learners by providing them with a tool that offers precise, current, accurate, and current time information. With the ease of accessing information any time and from anywhere, nursing students have the potential to control what and how learning occurs

Accretion with back reaction

We calculate analytically a back reaction of the stationary spherical accretion flow near the event horizon and near the inner Cauchy horizon of the charged black hole. It is shown that corresponding back-reaction corrections to the black hole metric depend only on the fluid accretion rate and diverge in the case of an extremely charged black hole. In result, the test fluid approximation for stationary accretion is violated for extreme black holes. This behavior of the accreting black hole is in accordance with the third law of black hole thermodynamics, forbidding the practical attainability of the extreme state.Comment: 5 pages, 2 figures; new figure and references adde

Spontaneous soliton formation and modulational instability in Bose-Einstein condensates

The dynamics of an elongated attractive Bose-Einstein condensate in an axisymmetric harmonic trap is studied. It is shown that density fringes caused by self-interference of the condensate order parameter seed modulational instability. The latter has novel features in contradistinction to the usual homogeneous case known from nonlinear fiber optics. Several open questions in the interpretation of the recent creation of the first matter-wave bright soliton train [Strecker {\it et al.} Nature {\bf 417} 150 (2002)] are addressed. It is shown that primary transverse collapse, followed by secondary collapse induced by soliton--soliton interactions, produce bursts of hot atoms at different time scales.Comment: 4 pages, 3 figures. Phys. Rev. Lett. in pres