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Biomedical subjects

Y N Huang

Publications and source records attributed to Y N Huang.

12 recordsLinked to original sources
PubMed2001

Modeling dynamically heterogeneous coupled relaxations.

A model describing dynamically heterogeneous relaxation in complex coupled systems is presented. The model predicts the splitting of a high-temperature single Debye relaxation to a low-temperature bimodal relaxation. The bimodal process shows a crossover from a Debye-type relaxation to an approximately stretched-exponential relaxation. Some general features of relaxation in complex systems emerge from the predictions of the model, and a comparison of the model with experiments is reported.

Journal Article↗
PubMed2001

Reynolds stress under a change of frame of reference.

In this paper, we study the characteristics of the Reynolds stress under a change of frame, as defined by the Euclidean group of transformation. We show that being subject to the dynamical processes induced from the mean Navier-Stokes equations, the invariance group of the fluctuating velocity and the Reynolds stress is no longer the Euclidean group of transformation, which is merely a kinematical aspect, but reduces to the extended Galilean group of transformation. As a consequence, in contrast to developing the constitutive equations for the Cauchy stress in continuum mechanics, wherein the principle of material frame-indifference is a guiding principle, the frame-dependent kinematical quantities, e.g., the mean spin tensor, may be allowed to play an effective role as the constitutive variable in turbulence modeling.

Journal Article↗
PubMed2001

Cerebrovascular disease among Chinese populations--recent epidemiological and neuroimaging studies.

Stroke mortality in individuals of Chinese descent has declined during the past decades, although the absolute number of patients with first-ever stroke is escalating. This review summarises recent epidemiological and imaging studies conducted among Chinese populations. Data indicating differences between Chinese and Caucasian ethnic groups in the pathophysiological mechanisms of stroke are highlighted, and the potential implications of these findings for prevention and management of stroke are discussed.

Cerebral Hemorrhage↗
PubMed1998

Intracranial stenosis in Chinese patients with acute stroke.

We studied 100 consecutive acute stroke patients in a Chinese population with transcranial Doppler and CT. Twenty patients had intracerebral hemorrhage and 14 patients did not have adequate temporal windows for transcranial Doppler examination. Among the remaining 66 patients, 22 patients (33%) had intracranial occlusive diseases and 3 (6%) had extracranial carotid stenosis. Our data showed that intracranial occlusive disease is the most commonly found vascular lesion in our acute stroke patients.

Adult↗
PubMed1997

Vascular lesions in Chinese patients with transient ischemic attacks.

We studied 96 Chinese patients with TIAs using transcranial Doppler and duplex ultrasonography. We found intracranial stenosis or occlusion in 51% of cases and extracranial disease in 19% of cases. The most common intracranial lesion was stenosis of the terminal internal carotid artery or proximal middle cerebral artery, whereas the most common extracranial lesion was stenosis of the carotid bifurcation.

Adolescent↗
PubMed1996

Variability of magnetic resonance angiography and computed tomography angiography in grading middle cerebral artery stenosis.

BACKGROUND AND PURPOSE: Magnetic resonance angiography and computed tomography angiography are new, noninvasive methods to provide images of the cerebral vasculature. The reliability of magnetic resonance angiography and computed tomography angiography when used to grade middle cerebral artery stenosis remains to be established. We sought to study the interobserver and intraobserver variabilities of magnetic resonance angiography and computed tomography angiography in grading middle cerebral artery stenosis. METHODS: A total of 50 middle cerebral arteries in 25 patients were studied with magnetic resonance angiography and computed tomography angiography. All patients had a history of ischemic stroke. The films were read independently by two observers on separate occasions. Films were shown again to the same observer 4 weeks after the first reading. The degree of middle cerebral artery stenosis was categorized into four grades: normal/mild, moderate, severe, and occluded. The interobserver and intraobserver variabilities were calculated by the kappa statistic method. RESULTS: Interobserver variability for grading middle cerebral artery stenosis was good (kappa = 0.78) for magnetic resonance angiography and moderate (kappa = 0.51) for computed tomography angiography. There was perfect agreement between two observers in 86% of the vessels shown in magnetic resonance angiography and in 76% of the vessels shown in computed tomography angiography. Intraobserver variability for both imaging methods was good, with the kappa value in the range of 0.70 to 0.76. CONCLUSIONS: Our results suggest that according to our protocol, magnetic resonance angiography is more reliable than computed tomography angiography in grading middle cerebral artery stenosis.

Adult↗
PubMed1995

Spiral computed tomography angiography in the assessment of middle cerebral artery occlusive disease.

There has been no report on the use of spiral computed tomography angiography (CTA) in the investigation of intracranial cerebral artery stenosis. A prospective pilot study was conducted to investigate the feasibility of CTA in the diagnosis of intracranial occlusive disease and its correlation with transcranial Doppler. With transcranial Doppler, 10 patients with acute ischaemic stroke with middle cerebral artery stenosis or occlusion were identified. There were seven middle cerebral artery stenoses and five middle cerebral artery occlusions. The CTA confirmed all diagnoses by transcranial Doppler except in one patient with middle cerebral artery occlusion in whom the embolus had probably propagated. The results showed that CTA is feasible and potentially useful in the diagnosis of middle cerebral artery occlusive disease. Further studies are required to assess its validity, sensitivity, and specificity in the diagnosis of middle cerebral artery occlusive disease.

Arterial Occlusive Diseases↗
PubMed1989

On the dynamics of a toxicant-individual system.

The dynamics of a toxicant-individual model where the individual is represented by von Bertalanffy dynamics and the uptake model component is one developed by Barber, Suarez & Lassiter is discussed. A sufficient condition for the death of an individual subjected to chemical stress is found. Another possible behavior of the system is an oscillatory mode of individual size and internal chemical concentration determined by a limit cycle. These fluctuations are a consequence of formulations of growth, maintenance, and the dose-response functions in the model system.

Animals↗
PubMed1989

A study of event-related potential P300 in cerebral infarction.

N1, P2 and P300 potentials were studied in 20 cases of cerebral infarction and 47 healthy controls with the standard technique of auditory event-related potentials. Healthy controls of both sexes, different ages, education levels and cognitive capacity did not show apparent differences in the latency of P300 (P greater than 0.05, respectively). The patient group, however, revealed a significant (P less than 0.001) prolongation of latency of P300 (means = 409.6 +/- 50 ms) as compared with 28 well matched healthy subjects (means = 337.7 +/- 24 ms). Although there was a slightly lower amplitude of P300 in the patient group, the difference between control and patient groups was not significant (P greater than 0.05). There was a significant difference in the Cognitive Capacity Screening Examination findings between control and patient groups (P less than 0.01), but it seems that evaluation of the cognition-related latency of P300 may be more objective and sensitive in distinguishing between organic and cognitive distress (P less than 0.001).

Adult↗