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Biomedical subjects

B Zheng

Publications and source records attributed to B Zheng.

At least 19 recordsLinked to original sources
PubMed2006

A laboratory study on anticipatory movement in laparoscopic surgery: a behavioral indicator for team collaboration.

BACKGROUND: To assess team collaboration in the context of laparoscopic surgery, laparoscopic cutting tasks performed by single operators and dyad teams were observed. Our previous work suggested that the anticipatory movement performed by a teammate may lead to a shorter total task time than for a single bimanual operator. This report further explores this phenomenon by quantifying the frequency of anticipatory movements and discussing their significance to team collaboration. METHODS: Subjects were required to reach, grasp, and cut a piece of thread using a laparoscopic grasper and scissors. The task was performed by either 8 individual subjects bimanually or 16 paired subjects unimanually (using their preferred hands). The performances were video recorded. The total task time, the time used for thread grasping and cutting, and the number of anticipatory movements were computed and compared between the single operator and the dyad team group. In this report, anticipatory movement is defined as movements of the scissors before the completion of grasping and holding the thread. RESULTS: Shorter durations of total task time were shown for the dyad than for the bimanual group. Anticipatory movements were counted significantly more often when the scissors were controlled by a teammate on the dyad team (96%) than when they were controlled by the preferred hand of the operator (45%). The number of anticipatory movements increased with practice, but no significant difference was shown among practice phases. CONCLUSION: Higher frequency of anticipatory movement was observed in the dyad team, which led to superior performance for team collaboration, as compared with that of the single operator. Performance of anticipatory movements in the dyad team was explained by a shared mental model, which postulates combined capacity for information processing among team members. Results have implications for surgical education, team training, and error prevention in the performance of laparoscopic surgery.

Adult↗
PubMed2006

Minority games with score-dependent and agent-dependent payoffs.

Score-dependent and agent-dependent payoffs of the strategies are introduced into the standard minority game. The intrinsic periodicity is consequently removed, and the stylized facts arise, such as long-range volatility correlations and "fat tails" in the distribution of the returns. The agent dependence of the payoffs is essential in producing the long-range volatility correlations. The new payoffs lead to a better performance in the dynamic behavior nonlocal in time, and can coexist with the inactive strategy. We also observe that the standard deviation sigma2/N is significantly reduced, thus the efficiency of the system is distinctly improved. Based on this observation, we give a qualitative explanation for the long-range volatility correlations.

Journal Article↗
PubMed2006

Return-volatility correlation in financial dynamics.

We investigate the return-volatility correlation both local and nonlocal in time with daily and minutely data of the German DAX and Chinese indices, and observe a leverage effect for the German DAX, while an antileverage effect for the Chinese indices. In the negative time direction, i.e., for the volatility-return correlation, an antileverage effect nonlocal in time is detected for both the German DAX and Chinese indices, although the duplicate local in time does not exist. A retarded volatility model may describe the asymmetric properties of the financial indices in the positive time direction.

Journal Article↗
PubMed2006

Computer simulations of two-dimensional melting with dipole-dipole interactions.

We perform molecular dynamics and Monte Carlo simulations of two-dimensional melting with dipole-dipole interactions. Both static and dynamic behaviors are examined. In the isotropic liquid phase, the bond orientational correlation length xi 6 and susceptibility chi 6 are measured, and the data are fitted to the theoretical ansatz. An algebraic decay is detected for both spatial and temporal bond orientational correlation functions in an intermediate temperature regime, and it provides an explicit evidence for the existence of the hexatic phase. From the finite-size scaling analysis of the global bond orientational order parameter, the disclination unbinding temperature Ti is estimated. In addition, from dynamic Monte Carlo simulations of the positional order parameter, we extract the critical exponents at the dislocation unbinding temperature Tm. All the results are in agreement with those from experiments and support the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory.

Journal Article↗
PubMed2006

Role of interleukin-6 in lipopolysaccharide-induced brain injury and behavioral dysfunction in neonatal rats.

There are increasing data in support of the hypothesis that inflammatory cytokines are involved in neonatal white matter damage. Despite extensive study of the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-1beta, the role of interleukin-6 in the development of white matter damage is largely unknown. In the present study, the role(s) of interleukin-6 in mediating lipopolysaccharide-induced brain injury and behavioral changes was investigated by the intracerebral injection of lipopolysaccharide with interleukin-6 neutralizing antibody in the 5-day-old rat brain. Brain injury was examined in brain sections at postnatal day 8 and postnatal day 21. Behavioral tests including righting reflex, wire hanging maneuver, cliff avoidance, locomotor activity, gait analysis, responses in the elevated plus-maze and passive avoidance were performed from postnatal day 3 to postnatal day 21. Changes in astroglia, microglia and oligodendrocytes were studied using immunohistochemistry in the postnatal day 21 rat brain. Our results show that interleukin-6 antibody attenuated lipopolysaccharide-induced brain lateral ventricle dilation and improved neurobehavioral performance. Interleukin-6 antibody also suppressed lipopolysaccharide-induced astrogliosis and microglial activation, and increased the number of oligodendrocytes in white matter. However, no changes of tumor necrosis factor-alpha and interleukin-1beta were detected. In contrast, no histopathological changes and glial activation were observed in rats injected with only interleukin-6. The present study indicates that the contribution to brain injury by interleukin-6 depends on its interaction with other lipopolysaccharide-induced agents and not on interleukin-6 alone.

Age Factors↗
PubMed2005

Dynamic Monte Carlo simulations of the three-dimensional random-bond Potts model.

The effect of random bonds on the phase transitions of the three-dimensional three-state Potts model is investigated with extensive dynamic Monte Carlo simulations. In the weakly disordered regime, the phase diagram is obtained with a recently suggested nonequilibrium reweighting method. The tricritical point separating the first- and second-order transitions is determined, and the critical exponents of the continuous phase transition induced by quenched randomness are estimated.

Journal Article↗
PubMed2005

Video analysis of endoscopic cutting task performed by one versus two operators.

BACKGROUND: In the performance of complex laparoscopic tasks, one question is whether the task should be distributed between two operators or accomplished bimanually by one operator. The authors hypothesized that superior task performance results when two operators work collaboratively in a dyad team as opposed to one operator performing the task bimanually. Furthermore, in a visually misaligned condition, the performance of a team will be more robust than that of a single operator working alone. METHODS: The suture-cutting task was performed by 24 right-handed subjects in a mock surgical setup using a laparoscopic grasper and a pair of laparoscopic scissors. The cutting task was performed by 8 subjects bimanually (using both limbs) and 16 paired subjects unimanually (using their preferred limbs). The image of the work plane was displayed either vertically or superimposed over the work plane. In half of the conditions, the camera was rotated 45 degrees, causing misalignment between the actual and displayed work planes. Movements were videotaped. Important movement events were identified and used to subdivide the task into subtasks. Durations of the subtasks and attempts for grasping and cutting were analyzed using a mixed-design multivariate analysis of variance (MANOVA). RESULTS: For a number of subtasks, the dyad group showed shorter durations than the bimanual group. The 45 degrees rotation of the camera degraded both bimanual and dyad performance, resulting in prolonged movement times for all subtasks. The learning process was facilitated by the superimposed display in that grasper and scissor reaching times improved over trials, as compared with the vertical display. CONCLUSION: The results indicate the superior role of team collaboration, as compared with the single operator, in a complex remote manipulation such as a laparoscopic cutting task. This enhanced task performance is achieved because of the larger capacity for information processing. These results may have some relevance for optimizing performance of endoscopic surgery.

Adult↗
PubMed2005

Dynamic isomer shift in charge-ordering manganite Y(0.5)Ca(0.5)MnO(3): Mössbauer spectroscopy study.

We report the Mössbauer spectroscopy study on Fe-doped charge-ordering manganite Y(0.5)Ca(0.5)MnO(3). The dynamic isomer shift is observed for charge-ordering manganite, and its origin may be due to strong Jahn-Teller distortions in Y(0.5)Ca(0.5)MnO(3), causing electron-phonon coupling. The evolution of Mössbauer spectroscopy as a function of temperature shows two different phases with significantly different quadrupole splitting values below the charge-ordering transition temperature. This confirms that there exist two different Mn sites (i.e., Mn(3+) and Mn(4+) ions), which can be identified by the microscopic method of Mössbauer spectroscopy.

Letter↗
PubMed2005

Age-associated deficiency in activation-induced up-regulation of telomerase activity in CD4+ T cells.

For lymphocytes, the ability to undergo clonal expansion is crucial for effective immune function. Telomerase activity compensates for telomere erosion during cell division and contributes to the capability of lymphocytes to maintain cellular proliferation. In addition, telomerase activity may have a fundamental role in cell growth and survival. To determine whether age-related immune dysfunction is associated with an abnormality in telomerase activity, we investigated telomerase activity in T cell populations from young adult and aged mice. Our data show that the ability of T cells from aged mice to up-regulate telomerase activity after activation was significantly diminished. This age-related deficiency in telomerase induction is restricted to CD4(+) T cells, as CD8(+) T cells retain the capability to up-regulate telomerase activity. These findings reinforce the notion that age-related immune dysfunction results mainly from impairment of helper T cells, and may have important implications for designing novel means to improve immune responses in aged individuals by enhancing CD8(+) T cell functions, which are crucial in both viral and tumour immunity.

Aging↗
PubMed2004

Critical behavior of the two-dimensional random-bond Potts model: a short-time dynamic approach.

The short-time critical dynamics of the two-dimensional eight-state random-bond Potts model is investigated with large-scale Monte Carlo simulations. Dynamic relaxation starting from a disordered and an ordered state is carefully analyzed. The continuous phase transition induced by disorder is studied, and both the dynamic and static critical exponents are estimated. The static exponent beta/nu shows little dependence on the disorder amplitude r, while the dynamic exponent z and static exponent 1/nu vary with the strength of disorder.

Journal Article↗
PubMed2004

Analysis of transcripts that are differentially expressed in three sectors of the rice root system under water deficit.

Short periods of water deprivation can stimulate the growth of seminal and lateral roots in rice, and inhibit the emergence of adventitious roots. Identification of genes in the different tissues that respond to a water deficit may help us to understand the mechanism underlying root growth under conditions when water is scarce. cDNA-amplified fragment length polymorphism (AFLP) analysis was used to profile gene expression upon imposition of water deficit in three types of root tissue from the upland rice variety Azucena: seminal root tips, lateral root zones and adventitious root primordial zones. In all, 121 unique transcript-derived fragments (TDFs) were cloned, and Northern analysis was carried out for 30 TDFs to confirm their expression patterns. Sixty-six TDFs were differentially expressed in all three root samples. Four (AC2, D6, L22 and T23) were up-regulated by water deficit in seminal root tips and lateral root zones, and down-regulated in adventitious root primordial zones, an expression pattern which reflects the phenotypic changes observed in the different root sectors. In contrast, T17 and T37 showed the opposite expression pattern in Azucena: up-regulation in adventitious roots and repression in the other two zones. Functions could be assigned to five of these six TDFs on the basis of homology: they encode an expansin (T37), a fruit-ripening protein similar to ASR (T23), submergence-induced protein 2A (T17), a dehydrin (D6) and a 9- cis -epoxycarotenoid dioxygenase1 (L22), respectively. AC2 did not show a significant match to any known gene. Northern analysis showed that these six clones exhibited expression patterns that differed between the two cultivars tested (Azucena and the lowland variety IR1552) with respect to regulation by water limitation. Furthermore, T17, T37, D6 and T23 mapped within intervals known to contain QTLs (quantitative trait loci) for root growth in rice under water deficit. These genes may regulate or co-regulate the growth and development of the three root zones in a tissue-specific manner, and may play a role in the processes that underlie the early changes in root architecture under conditions of water deprivation.

Blotting, Northern↗
PubMed2004

Two-phase phenomena, minority games, and herding models.

The recently discovered two-phase phenomenon in financial markets [Nature 421, 130 (2003)] is examined with the German financial index DAX, minority games, and dynamic herding models. It is observed that the two-phase phenomenon is an important characteristic of financial dynamics, independent of volatility clustering. An interacting herding model correctly produces the two-phase phenomenon.

Journal Article↗
PubMed2004

Molecular epidemiology of the novel coronavirus that causes severe acute respiratory syndrome.

BACKGROUND: Severe acute respiratory syndrome (SARS) is a newly emerged disease caused by a novel coronavirus (SARS-CoV), which spread globally in early 2003, affecting over 30 countries. We have used molecular epidemiology to define the patterns of spread of the virus in Hong Kong and beyond. METHODS: The case definition of SARS was based on that recommended by WHO. We genetically sequenced the gene for the S1 unit of the viral spike protein of viruses from patients with SARS in Hong Kong (138) and Guangdong (three) in February to April, 2003. We undertook phylogenetic comparisons with 27 other sequences available from public databases (Genbank). FINDINGS: Most of the Hong Kong viruses (139/142), including those from a large outbreak in an apartment block, clustered closely together with the isolate from a single index case (HKU-33) who came from Guangdong to Hong Kong in late February. Three other isolates were genetically distinct from HKU-33 in Hong Kong during February, but none of these contributed substantially to the subsequent local outbreak. Viruses identified in Guangdong and Beijing were genetically more diverse. INTERPRETATION: The molecular epidemiological evidence suggests that most SARS-CoV from the outbreak in Hong Kong, as well as the viruses from Canada, Vietnam, and Singapore, are genetically closely linked. Three viruses found in Hong Kong in February were phylogenetically distinct from the major cluster, which suggests that several introductions of the virus had occurred, but that only one was associated with the subsequent outbreak in Hong Kong, which in turn spread globally.

Canada↗
PubMed2003

Corrections to scaling in two-dimensional dynamic XY and fully frustrated XY models.

With large-scale Monte Carlo simulations, we investigate the two-dimensional dynamic XY and fully frustrated XY models. Dynamic relaxation starting from a disordered or an ordered state is carefully analyzed. It is confirmed that there is a logarithmic correction to scaling for a disordered start, but a power-law correction for an ordered start. Rather accurate values of the static exponent eta and the dynamic exponent z are estimated.

Journal Article↗
PubMed2003

Reaction times and the decision-making process in endoscopic surgery.

BACKGROUND: There are times during endoscopic procedures when the displayed surgical field does not align with the actual field due to rotation of the camera. The surgeon's performance may deteriorate under this situation. However, the effects of misalignment on the decision-making processes during endoscopic procedures have not been fully explored. The present study addresses this problem and suggests a technique that may be used to alleviate it. METHODS: Two experiments were completed in a mock endoscopic surgical setup where the image of the work plane inside the training box was either projected on a vertical monitor placed at eye level or superimposed over the training box by means of a half-silvered mirror. The work plane consisted of a start plate and four target plates. The experimenter varied the number of choices of target location among one, two, and four target choices. Rotating the camera about its longitudinal axis misaligned the displayed and the actual work plane. There were two experiments that differed in task difficulty. The task in experiment 1 was to touch the target plate, whereas the task in experiment 2 was to reach, grasp, and transport the object from the target to the start plate. RESULTS: Experiment 1 showed that reaction time increased with the number of the choices for a touch task, in accordance with the Hick-Hyman law. Using a grasp-and-transport task, experiment 2 replicated experiment 1 and extended the results to show that the use of a superimposed image display facilitated the decision-making process, leading to shorter reaction times compared to the vertical image display. DISCUSSION: During endoscopic procedures, the surgeon needs to translate indirect perceptions to instrument-mediated actions by "mapping" them through sensorimotor integration. The superimposed image alleviates the mental load of spatial transformations by reducing the difficulty of the required sensorimotor mapping. These findings have important implications for the design of high-quality superimposed display technologies.

Adult↗
PubMed2003

Generic features of fluctuations in critical systems.

The probability distribution function of magnetization of critical magnetic systems is investigated with Monte Carlo simulations. Its generic features beyond the standard universality are revealed. A mean field ansatz explains the phenomena partly.

Journal Article↗
PubMed2003

The complete genome sequence of severe acute respiratory syndrome coronavirus strain HKU-39849 (HK-39).

The complete genomic nucleotide sequence (29.7kb) of a Hong Kong severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) strain HK-39 is determined. Phylogenetic analysis of the genomic sequence reveals it to be a distinct member of the Coronaviridae family. 5' RACE assay confirms the presence of at least six subgenomic transcripts all containing the predicted intergenic sequences. Five open reading frames (ORFs), namely ORF1a, 1b, S, M, and N, are found to be homologues to other CoV members, and three more unknown ORFs (X1, X2, and X3) are unparalleled in all other known CoV species. Optimal alignment and computer analysis of the homologous ORFs has predicted the characteristic structural and functional domains on the putative genes. The overall nucleotides conservation of the homologous ORFs is low (<5%) compared with other known CoVs, implying that HK-39 is a newly emergent SARS-CoV phylogenetically distant from other known members. SimPlot analysis supports this finding, and also suggests that this novel virus is not a product of a recent recombinant from any of the known characterized CoVs. Together, these results confirm that HK-39 is a novel and distinct member of the Coronaviridae family, with unknown origin. The completion of the genomic sequence of the virus will assist in tracing its origin.

3' Untranslated Regions↗