Three-dimensional ultrasonographic assessment of compression effect on urethra following tension-free vaginal tape and transobturator tape procedures.

OBJECTIVE: To compare the anatomical difference using three-dimensional (3D) ultrasound between the urethra at rest and during straining, in women who have undergone a tension-free vaginal tape (TVT) or TVT-obturator tape (TVT-O) procedure for stress urinary incontinence (SUI). METHODS: We reviewed retrospectively 48 women with SUI who had undergone either a TVT (n = 24) or a TVT-O (n = 24) procedure. All women underwent urinalysis, pelvic examination, pad test, 3D perineal ultrasonography and personal interview about urinary symptoms within 1 year after surgery. RESULTS: After both TVT and TVT-O procedures, the area and longest and shortest diameters of the hypoechoic core of the mid-urethra were significantly smaller during straining than during resting (P < 0.01). The distance between tape and urethra was similarly smaller during straining in both groups. Analysis of ultrasound measurements in women reporting success (n = 40) and those reporting failure (n = 8) of the procedure showed the area and longest and shortest diameters of the hypoechoic core of the mid-urethra to be significantly smaller during straining than during resting in both groups (P < 0.01). However, the shortest diameter of the proximal and distal urethra during straining were significantly smaller only in the successful group (P < 0.01). CONCLUSION: There are differences in urethral morphology during straining compared with during resting in women with TVT and those with TVT-O, regardless of tape procedure. A urethral compression effect of slings may have an important role in the continence mechanism.

Radial artery anomaly and its influence on transradial coronary procedural outcome.

BACKGROUND: The transradial approach for percutaneous coronary procedures has the advantage of reduced access site complications but is associated with specific technical challenges in comparison with the transfemoral approach. Transradial procedure failures can sometimes be due to variation in radial artery anatomy. However, data describing such variations are limited. OBJECTIVE: To evaluate the incidence and impact of radial artery anomalies in patients undergoing transradial coronary procedures. METHODS: Retrograde radial arteriography was performed in all patients presenting for a first-time radial procedure. Patient characteristics, radial artery anatomy and procedural outcome were assessed. RESULTS: 1540 consecutive patients were studied, 70.6% male, mean (SD) age 63.6 (11.1) years. The overall incidence of radial artery anomaly was 13.8% (n = 212). 108 (7.0%) patients had a high-bifurcating radial origin, 35 (2.3%) had a full radial loop, 30 (2.0%) had extreme radial artery tortuosity and 39 (2.5%) had miscellaneous anomalies such as radial atherosclerosis and accessory branches. Overall transradial procedural success was 96.8%. Procedural failure was more common in patients with anomalous anatomy than in patients with normal anatomy (14.2% vs 0.9%, p<0.001). Procedural failure in patients with high radial bifurcation, radial loop, severe radial tortuosity and other anomalies was 4.6%, 37.1%, 23.3% and 12.9%, respectively. 15 (1%) vascular complications occurred, all of which were treated conservatively without ischaemic sequelae. CONCLUSION: Anomalous radial artery anatomy is relatively common and is a significant cause of procedural failure. Within each specific anomalous pattern there is a differential procedural failure rate. This has implications for clinical practice and suggests a need for imaging of the radial artery after sheath insertion.

Refined similarity hypotheses in shell models of homogeneous turbulence and turbulent convection.

A major challenge in turbulence research is to understand from first principles the origin of the anomalous scaling of velocity fluctuations in high-Reynolds-number turbulent flows. One important idea was proposed by Kolmogorov [J. Fluid Mech. 13, 82 (1962)], which attributes the anomaly to variations of the locally averaged energy dissipation rate. Kraichnan later pointed out [J. Fluid Mech. 62, 305 (1973)] that the locally averaged energy dissipation rate is not an inertial-range quantity and a proper inertial-range quantity would be the local energy transfer rate. As a result, Kraichnan's idea attributes the anomaly to variations of the local energy transfer rate. These ideas, generally known as refined similarity hypotheses, can also be extended to study the anomalous scaling of fluctuations of an active scalar, such as the temperature in turbulent convection. We examine the validity of these refined similarity hypotheses and their extensions to an active scalar in shell models of homogeneous turbulence and turbulent convection. We find that Kraichnan's refined similarity hypothesis and its extension are valid.

Turbulent drag reduction by flexible and rodlike polymers: Crossover effects at small concentrations.

Drag reduction by polymers is bounded between two universal asymptotes, the von Kármán log law of the law and the maximum drag reduction (MDR) asymptote. It is theoretically understood why the MDR asymptote is universal, independent of whether the polymers are flexible or rodlike. The crossover behavior from the Newtonian von Kármán log law to the MDR is, however, not universal, showing different characteristics for flexible and rodlike polymers. In this paper we provide a theory for this crossover phenomenology.

Drag reduction by compressible bubbles.

Drag reduction by bubbles in stationary turbulent flows is sensitive to the compressibility of the bubbles. Without this dynamical effect the bubbles only renormalize the fluid density and viscosity, an effect that by itself can only lead to a small percentage of drag reduction. We show in this paper that the dynamics of bubbles and their effect on the compressibility of the mixture can lead to a much higher drag reduction.

Theory of enhanced performance emerging in a sparsely connected competitive population.

We provide an analytic theory to explain Anghel et al's recent numerical finding whereby a maximum in the global performance emerges for a sparsely connected competitive population [Phys. Rev. Lett. 92, 058701 (2004)]. We show that the effect originates in the highly correlated dynamics of strategy choice, and can be significantly enhanced using a simple modification to the model.

Additive equivalence in turbulent drag reduction by flexible and rodlike polymers.

We address the additive equivalence discovered by Virk and co-workers: drag reduction affected by flexible and rigid rodlike polymers added to turbulent wall-bounded flows is limited from above by a very similar maximum drag reduction (MDR) asymptote. Considering the equations of motion of rodlike polymers in wall-bounded turbulent ensembles, we show that although the microscopic mechanism of attaining the MDR is very different, the macroscopic theory is isomorphic, rationalizing the interesting experimental observations.

Estimating the proportion of community-associated methicillin-resistant Staphylococcus aureus: two definitions used in the USA yield dramatically different estimates.

The objective of this retrospective study was to compare the prevalence of community-associated methicillin-resistant Staphylococcus aureus (CAMRSA) and healthcare-associated MRSA (HAMRSA) using healthcare risk factor exposure criteria with that obtained using Centers for Disease Control and Prevention (CDC) criteria. Cases were defined as CAMRSA or HAMRSA based on the general CDC guidelines for nosocomial infections, and then re-assessed with healthcare risk factor exposure criteria using a medical chart review. One hundred MRSA cases occurred at a mid-Western veterans affairs medical centre from November 2001 to November 2003. The proportion of these cases classified as CAMRSA differed dramatically when classified by healthcare risk factor exposure criteria (5%) compared with CDC nosocomial infection criteria (49%). Estimating the role of healthcare-related exposures and developing strategies to control MRSA can be markedly affected by the criteria used to determine CAMRSA and HAMRSA.

Theory of networked minority games based on strategy pattern dynamics.

We formulate a theory of agent-based models in which agents compete to be in a winning group. The agents may be part of a network or not, and the winning group may be a minority group or not. An important feature of the present formalism is its focus on the dynamical pattern of strategy rankings, and its careful treatment of the strategy ties which arise during the system's temporal evolution. We apply it to the minority game with connected populations. Expressions for the mean success rate among the agents and for the mean success rate for agents with k neighbors are derived. We also use the theory to estimate the value of connectivity p above which the binary-agent-resource system with high resource levels makes the transition into the high-connectivity state.

Avoiding laboratory pitfalls in infectious diseases.

In today's medical care environment, clinicians are challenged to order clinically relevant, cost effective laboratory tests and antibiotic therapy. Together, physicians and laboratories must have guidelines and strategies that can provide quality patient care, while minimising costs and preventing further emergence of antimicrobial drug resistance. Five clinical vignettes that demonstrate these principles are presented.

Enhanced winning in a competing population by random participation.

We study a version of the minority game in which one agent is allowed to join the game in a random fashion. It is shown that in the crowded regime, i.e., for small values of the memory size m of the agents in the population, the agent performs significantly well if she decides to participate the game randomly with a probability q and she records the performance of her strategies only in the turns that she participates. The information, characterized by a quantity called the inefficiency, embedded in the agent's strategies performance turns out to be very different from that of the other agents. Detailed numerical studies reveal a relationship between the success rate of the agent and the inefficiency. The relationship can be understood analytically in terms of the dynamics in which the various possible histories are being visited as the game proceeds. For a finite fraction of randomly participating agents up to 60% of the population, it is found that the winning edge of these agents persists.

Early experience with a helical coronary thrombectomy device in patients with acute coronary thrombosis.

OBJECTIVE: To report our experience with a new thrombectomy device (X-SIZER(TM)) in patients with angiographically visible thrombus or total coronary occlusion in the setting of acute coronary syndromes. DESIGN: A safety and feasibility study in the use of the X-SIZER during intervention in patients with acute coronary syndromes. PATIENTS: 35 patients, age range 31 to 83 years (mean 60). SETTING: University Hospitals of Coventry and Warwickshire NHS Trust (tertiary referral centre). INTERVENTIONS: The indication for intervention was primary or salvage percutaneous coronary intervention for acute myocardial infarction in 17 of the 35 patients; unstable angina or non-ST-elevation myocardial infarction in 10; and unstable postinfarct angina in eight. Abciximab was given in 11 patients. MAIN OUTCOME MEASURES: Device success (successful deployment of the device at the site of the lesion with resultant improvement in TIMI flow); clinical success (no residual stenosis at the end of the procedure with no in-hospital major adverse coronary events). RESULTS: Successful use of the device was achieved in 26 of the 35 cases. It failed to cross the lesion in five and failed to improve TIMI flow despite crossing the lesion in four. Clinical success was achieved in 30 of the 35 cases. Device related complications occurred in two cases (vessel perforation) and there was one intraprocedural death (acute myocardial infarction with cardiogenic shock). CONCLUSIONS: Thrombectomy with the X-SIZER catheter system appears promising in percutaneous coronary intervention where thrombus extraction is considered necessary before stent implantation.

Phase-field modeling of microstructural pattern formation during directional solidification of peritectic alloys without morphological instability.

During the directional solidification of peritectic alloys, two stable solid phases (parent and peritectic) grow competitively into a metastable liquid phase of larger impurity content than either solid phase. When the parent or both solid phases are morphologically unstable, i.e., for a small temperature gradient/growth rate ratio (G/v(p)), one solid phase usually outgrows and covers the other phase, leading to a cellular-dendritic array structure closely analogous to the one formed during monophase solidification of a dilute binary alloy. In contrast, when G/v(p) is large enough for both phases to be morphologically stable, the formation of the microstructure becomes controlled by a subtle interplay between the nucleation and growth of the two solid phases. The structures that have been observed in this regime (in small samples where convection effects are suppressed) include alternate layers (bands) of the parent and peritectic phases perpendicular to the growth direction, which are formed by alternate nucleation and lateral spreading of one phase onto the other as proposed in a recent model [R. Trivedi, Metall. Mater. Trans. A 26, 1 (1995)], as well as partially filled bands (islands), where the peritectic phase does not fully cover the parent phase which grows continuously. We develop a phase-field model of peritectic solidification that incorporates nucleation processes in order to explore the formation of these structures. Simulations of this model shed light on the morphology transition from islands to bands, the dynamics of spreading of the peritectic phase on the parent phase following nucleation, which turns out to be characterized by a remarkably constant acceleration, and the types of growth morphology that one might expect to observe in large samples under purely diffusive growth conditions.

Ultrasonographic and urodynamic evaluation after tension free vagina tape procedure (TVT).

BACKGROUND: This study was carried out to evaluate the urodynamic and ultrasonographic findings after tension-free vagina tape (TVT) procedure on stress urinary incontinent women. METHODS: Ninety women suffering from genuine stress incontinence without pelvic relaxation syndrome underwent surgery. Urodynamic measurement, one-hour pad test and introital ultrasonographic evaluation were performed preoperatively and one year after surgery. Additional ultrasonographic surveillance of the urethra was performed immediately after the operation. The position and mobility of the bladder neck was compared pre- and post-operatively in relation to the inferior edge of the pubic symphysis. RESULT: Eight women were excluded for various reasons. Among the 82 women who completed the study, 76 (93%) were cured, four were improved and two failed. No major intra- or post-operative complications occurred. The position and mobility of the bladder neck showed no significant difference before and after surgery. A urethral knee angle was noted ultrasonographically on cured and improved patients during maximum straining. Nine patients with immediate postoperative voiding difficulty were found to have a pronounced mid-urethra angulation. The symptom and sign were resolved by time after urethra depressing. Urodynamic assessment of the urethral pressure profile and other parameter showed no significant difference before and after the surgery except that a positive pressure transmission in the middle portion of the urethra was noted among 70 (87.5%) of cured and improved subjects. CONCLUSION: Tension-free vagina tape operation is an effective surgical procedure for the treatment of female urinary stress incontinence. The procedure seems neither to change hypermobility nor to elevate the position of bladder neck. Urinary continence after surgery is most probably achieved by creating a dynamic mid-urethral knee angulation by which the urethra is closed i.e. kinked at stress. Lifting of the mid-urethra resulted in postoperative voiding difficulty. It is the important that the tape is placed tension free under the urethra. Introital ultrasonographic surveillance is a suitable technique to visualize the result of the operation.