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T S Lo

Publications and source records attributed to T S Lo.

At least 19 recordsLinked to original sources
PubMed2006

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.

Journal Article↗
PubMed2006

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.

Journal Article↗
PubMed2005

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.

Journal Article↗
PubMed2005

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.

Competitive Behavior↗
PubMed2005

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.

Community-Acquired Infections↗
PubMed2004

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.

Adaptation, Physiological↗
PubMed2004

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.

Journal Article↗
PubMed2004

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.

Aged↗
PubMed2001

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.

Journal Article↗
PubMed2001

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.

Adult↗
PubMed1999

Complex regional pain syndrome type-1: a rare complication of arteriovenous graft placement.

Complex regional pain syndrome (CRPS) type-1 (previously termed reflex sympathetic dystrophy syndrome) may be manifested as sympathetically mediated pain and swelling in an extremity. Among the numerous causes of reflex sympathetic dystrophy, the most common is trauma. We describe a 71-year-old diabetic man with endstage renal disease who presented with CRPS type-1 of the left hand one month after construction of a PTFE (polytetrafluroethylene) arteriovenous graft. The symptoms of CRPS improved greatly with stellate ganglion blocks and physical therapy.

Aged↗
PubMed1998

Evaluation of the hepatoprotective and antioxidant activity of Boehmeria nivea var. nivea and B. nivea var. tenacissima.

In this study, the relationship between liver protective effects and antioxidant activity of Boehmeria nivea var. nivea (= B. nivea) and B. nivea var. tenacissima (= B. frutescens) was investigated. The water extracts of both plants exhibited a hepatoprotective activity against CCl4-induced liver injury. B. nivea var. nivea and B. nivea var. tenacissima, also showed anti-oxidant effects in FeCl2-ascorbate induced lipid peroxidation in rat liver homogenate. Moreover, the active oxygen species scavenging potencies were evaluated by an electron spin resonance (ESR) spin-trapping technique. B. nivea var. tenacissima displayed better superoxide radical scavenging activity than B. nivea. Based on these findings, we suggest that in the liver protective and antioxidative effects of B. nivea var. nivea and B. nivea var. tenacissima, possibly involve mechanisms related to free radical scavenging effects.

Animals↗
PubMed1998

Successful management of chylous ascites after laparoscopic presacral neurectomy.

Laparoscopic presacral neurectomy is a safe, effective, and well-established surgical procedure to relieve intractable dysmenorrhea and chronic pelvic pain. In one woman, substantial lymphatic leakage occurred due to damaged lymphatic vessels. Adequate exposure and coagulation of the presacral lymphatic zone through the laparoscope resolved the problem, and a substantial amount of chylous ascites was removed. The patient fully recovered after the intervention.

Adult↗
PubMed1998

Management of chylous ascites following laparoscopic presacral neurectomy.

Chylous ascites is an extremely rare complication of laparoscopic presacral neurectomy (LPSN), and treatment is still controversial. Four patients undergoing LPSN for dysmenorrhoea or chronic pelvic pain were complicated with chylous ascites. Two were successfully treated with bipolar cauterization and one, after the failure of initial treatment by bipolar cauterization, was then effectively managed by compression with Gelform and closure of the peritoneum of the presacral area by suture through laparoscopy. The fourth patient had persistent chyle leakage from the drainage tube after electrocauterization and was finally cured by conservative management including removal of the drainage tube and a low-fat diet for 3 weeks. Chylous ascites has not been reported in laparoscopic presacral neurectomy. Management that is quick, effective and subjects the patients to the least amount of suffering is still unresolved. Repeated laparoscopy can be considered to identify the possibility of injury to lymphatic vessels, to relieve abdominal distention due to chyle accumulation, and to apply electrocauterization or compression with Gelform and closure of the peritoneum. Conservative treatment with a low-fat diet may need a longer time. The use of a drainage tube may provide negative pressure allowing a continuous leakage of chyle. However, more controlled study is required to identify the most proper and effective management.

Adult↗
PubMed1998

Tension-free vaginal tape. A minimally invasive solution to stress urinary incontinence in women.

OBJECTIVE: To determine the efficacy and safety of a new continence procedure, tension-free vaginal tape (TVT) placement for surgical treatment of stress urinary incontinence in women. STUDY DESIGN: Eighty-three women with demonstrable stress urinary incontinence underwent a nonrandomized, prospective study using the TVT procedure. The procedure was previously described by Ulmsten et al. In the present study, instead of local anesthesia, epidural blockade with 20 mL of 2% xylocaine was used. Preoperatively the patients were evaluated with a one-hour pad test, full urodynamic testing using either a double-lumen catheter or microtip transducer catheter and were instructed to maintain an one-week baseline urinary diary one week before and two months after the operation. Another one-hour pad test and complete urodynamic evaluation using microtip transducer catheters were offered to 20 patients postoperatively. The period of follow-up ranged from 3 to 18 months. RESULTS: Thirteen women were excluded for various reasons; thus, 70 subjects were enrolled in the study. The urodynamic diagnosis of the 83 women revealed that 71 had genuine stress incontinence, 11 had mixed incontinence and 1 was normal. Mean operation time was 29 minutes (range, 20-51) and mean hospital stay 3 days (range, 2-8). Three bladder perforations occurred intraoperatively. No patients had intraoperative bleeding > 300 mL, but 11 (16%) had blood loss > 200 mL, necessitating an indwelling catheter and vaginal tamponade. No evidence of defect healing or rejection of the tape occurred. Urine leakage observed on the pad test was significantly reduced from a mean of 63 g (range, 10-213) before to a mean of 5 g (range, 0-42) after surgery. The objective cure rate was 83%, and the subjective rate was 87%. CONCLUSION: Although the follow-up period was short, the TVT procedure seemed to be a safe and effective method for the treatment of stress urinary incontinence.

Female↗
PubMed1997

Advanced actinomycosis involving urogenital organs simulating malignancy: a case report.

A long-standing and widely used intrauterine contraceptive device has been associated with actinomycotic pelvic inflammation. The stealthy and chronic nature of the disease progresses and occasionally infiltrates adjacent organs. The non-specific symptoms of the disease, solid invasive mass and lack of marked leukocytosis, often suggest a malignancy. We present a case of advanced pelvic actinomycosis involving urogenital organs which has not been reported before. The behaviors of the disease, which mimic malignancy and urogenital manifestation, pose difficulties in diagnosis and management.

Actinomycosis↗