Biomedical subjects

C K Law

Publications and source records attributed to C K Law.

At least 19 recordsLinked to original sources

PubMed2006

Suicidal ideation and suicidal attempts in a population-based study of Chinese people: risk attributable to hopelessness, depression, and social factors.

BACKGROUND: The population attributable fraction of hopelessness, depression and other risk factors for suicidal ideation and suicidal attempts in Asian population is unknown. Social support is often said to be a buffer against the effect of hopelessness and depression. METHODS: Suicidal ideation, suicidal attempts as well as demographic and psychometric data were delineated in a random and representative population sample of 2,219 Chinese people in Hong Kong. The population attributable fraction was used to determine the contribution of hopelessness, depression and other risk factors to suicidal ideation and attempts. RESULTS: Multivariate modelling shows that about 40% of suicidal ideation and attempts was attributable to depression and about 20% was attributable to hopelessness. Drug abuse and marital dissolution were also significant contributors to suicidality. The impact of hopelessness and depression was not affected by social support. LIMITATIONS: Suicidality was self-reported. CONCLUSIONS: Suicidal ideation and suicidal attempts were to a large extent attributable to depression and hopelessness, and, to a lesser extent, drug abuse and marital dissolution. Social support appeared to play little role as a buffer.

Adolescent↗

PubMed2005

Thermochemical and kinetic analyses on oxidation of isobutenyl radical and 2-hydroperoxymethyl-2-propenyl radical.

In recognition of the importance of the isobutene oxidation reaction in the preignition chemistry associated with engine knock, the thermochemistry, chemical reaction pathways, and reaction kinetics of the isobutenyl radical oxidation at low to intermediate temperature range were computationally studied, focusing on both the first and the second O2 addition to the isobutenyl radical. The geometries of reactants, important intermediates, transition states, and products in the isobutenyl radical oxidation system were optimized at the B3LYP/6-311G(d,p) and MP2(full)/6-31G(d) levels, and the thermochemical properties were determined on the basis of ab initio, density functional theory, and statistical mechanics. Enthalpies of formation for several important intermediates were calculated using isodesmic reactions at the DFT and the CBS-QB3 levels. The kinetic analysis of the first O2 addition to the isobutenyl radical was performed using enthalpies at the CBS-QB3 and G3(MP2) levels. The reaction forms a chemically activated isobutenyl peroxy adduct which can be stabilized, dissociate back to reactants, cyclize to cyclic peroxide-alkyl radicals, and isomerize to the 2-hydroperoxymethyl-2-propenyl radical that further undergoes another O2 addition. The reaction channels for isomerization and cyclization and further dissociation on this second O2 addition were analyzed using enthalpies at the DFT level with energy corrections based on similar reaction channels for the first O2 addition. The high-pressure limit rate constants for each reaction channel were determined as functions of temperature by the canonical transition state theory for further kinetic model development.

Journal Article↗

PubMed2005

Social and economic burden of suicides in Hong Kong SAR: a year of life lost perspective.

The paper proposes to use the years-of-life-lost method (YLL) in assessing the social and economic burden of suicides in Hong Kong SAR. The YLL from suicide by age group in 1981-2002 is calculated based on the standard set by World Health Organization (WHO). It shows that the middle age group (25-39) contributed most to the burden of disease in Hong Kong. The proportion of older adults' suicides is about 25% of the total number of suicides but its disease burden is less than 6% in terms of the YLL. Though the group aged 25-39 contributed disproportionately to the total YLL from suicide, the prevention effort for this particular group has been very much neglected and needs to be strengthened. It illustrates that use of YLL could provide a new viewpoint for setting up public health policies.

Adolescent↗

PubMed2005

Incidence and spectrum of non-Hodgkin lymphoma in Chinese migrants to British Columbia.

The incidence and spectrum of non-Hodgkin lymphoma (NHL) differ between the Chinese and Caucasian populations. Using population-based registries, we studied the pattern of NHL in Chinese migrants to British Columbia (BC). The records of all NHL cases of Chinese descent diagnosed between 1980 and 1997 were retrieved. Age-standardized incidences were calculated by 5-year intervals in terms of age and calendar years and the relative rates were compared between the migrant, Hong Kong and BC populations. The histological distribution of NHL was compared with 4500 consecutive NHL cases diagnosed in the two populations. A total of 211 cases of migrant NHL were identified, with an age-standardized incidence rate of 7.11 per 100 000 per year, compared with the Hong Kong and BC rates of 7.91 [standardized incidence ratio (SIR) = 0.86, P = 0.01] and 11.88 (SIR = 0.56, P < 0.01). The standardized rates of follicular lymphoma remained low, but the incidence of gastric and nasal natural killer/T lymphomas in migrants were lower than expected. Genetic factors appeared to be stronger than environmental factors in governing the overall incidence of NHL in Chinese. However, certain subtypes of lymphoma may show decreased rates in migrants because of environmental factors.

Adolescent↗

PubMed2004

Analysis and interpretation of high transverse entanglement in optical parametric down conversion.

Quantum entanglement associated with transverse wave vectors of down conversion photons is investigated based on the Schmidt decomposition method. We show that transverse entanglement involves two variables: orbital angular momentum and transverse frequency. We show that in the monochromatic limit high values of entanglement are closely controlled by a single parameter resulting from the competition between (transverse) momentum conservation and longitudinal phase matching. We examine the features of the Schmidt eigenmodes, and indicate how entanglement can be enhanced by suitable mode selection methods.

Journal Article↗

PubMed2004

Clinical role of circulating Epstein-Barr virus DNA as a tumor marker in lymphoepithelioma-like carcinoma of the lung.

Nineteen Chinese patients with lymphoepithelioma-like carcinoma (LELC) of the lung were tested for Epstein-Barr virus (EBV) DNA in their serum samples by a quantitative polymerase chain reaction (PCR) technique. There was prospective serial monitoring of the serum in seven patients with advanced inoperable or relapsing disease. Five other patients at first diagnosis and two patients at relapse had only a single serum sample available. Serum samples were also taken from three other patients who had prior curative surgery and two patients with prolonged disease remission. Measurable levels of EBV DNA were detected in 11 of 12 patients with a pre-therapy serum sample and a clinically evident tumor. A low level of EBV DNA was also detectable in one of the two other patients whose first serum samples were obtained after some chemotherapy. There was no detectable EBV DNA in the five patients without evidence of tumor. The longitudinal serum EBV DNA profile of seven patients showed consistent correlation with response to therapy and clinical outcome. Patients with a pre-therapy serum EBV DNA >10,000 copies/mL had significantly inferior overall survival. This study suggests that circulating serum EBV DNA can be used as a tumor marker in the clinical management of patients with LELC of the lung.

Biomarkers, Tumor↗

PubMed2003

Control of entanglement and the high-entanglement limit.

We examine two-particle entanglement and ways in which it might be coherently controlled. Control is desirable for successful implementation of quantum computing. As one result, we find that reaching very high entanglement may be feasible experimentally.

Journal Article↗

PubMed2003

In-depth evaluation of the AJCC/UICC 1997 staging system of nasopharyngeal carcinoma: prognostic homogeneity and proposed refinements.

PURPOSE: To critically evaluate the American Joint Commission on Cancer (AJCC)/International Union Against Cancer (UICC) 1997 staging system and look back on its achievements by comparing it with the AJCC/UICC 1992 and Ho 1978 staging systems. To identify areas for additional refinement, we analyzed the prognostic heterogeneity within each stage in depth, which provided important clues for the addition or better categorization of the different defining criteria. METHODS AND MATERIALS: We performed a retrospective review of the data from 1294 consecutive biopsy-proven nonmetastatic nasopharyngeal carcinoma patients and staged the extent of disease according to the defining criteria of the three staging systems. All patients had undergone detailed pretreatment assessment by fiberoptic endoscopy and CT. Radical-intent radiotherapy was given using the Ho technique according to our standard protocol. RESULTS: The AJCC/UICC 1997 staging system was superior to the other two staging systems, because it assigned patients to more uniform-size stage groupings and correlated better with prognosis. Parapharyngeal space involvement was not an independent predictor for survival, local control, or metastasis. On the other hand, carotid space involvement correlated with a greater likelihood of metastasis. Prognostic heterogeneity was found. Those with orbit, cranial nerve, or intracranial involvement fared worse within Stage T4; those with a maximal lymph node size >3 cm fared worse within Stage N2; and those with bilateral lymph node metastasis fared worse within Stage N3. CONCLUSION: The prognostic accuracy of the AJCC/UICC 1997 staging system can be improved further by recategorization of the T, N, and group stage criteria.

Adolescent↗

PubMed2003

Healthy life expectancy in Hong Kong Special Administrative Region of China.

Sullivan's method and a regression model were used to calculate healthy life expectancy (HALE) for men and women in Hong Kong Special Administrative Region (Hong Kong SAR) of China. These methods need estimates of the prevalence and information on disability distributions of 109 diseases and HALE for 191 countries by age, sex and region of the world from the WHO's health assessment of 2000. The population of Hong Kong SAR has one of the highest healthy life expectancies in the world. Sullivan's method gives higher estimates than the classic linear regression method. Although Sullivan's method accurately calculates the influence of disease prevalence within small areas and regions, the regression method can approximate HALE for all economies for which information on life expectancy is available. This paper identifies some problems of the two methods and discusses the accuracy of estimates of HALE that rely on data from the WHO assessment.

Adolescent↗

PubMed2003

Treatment of trichlorophenol by catalytic oxidation process.

The oxidation of 2,4,6-trichlorophenol (TCP) by ferrous-catalyzed hydrogen peroxide was quantified and modeled in the study. TCP was effectively degraded by hydroxyl radicals that were generated by Fe(II)/H(2)O(2) in the oxidation process. The oxidation capacity (OC) of the process depends on the concentrations of oxidant (hydrogen peroxide) and oxidative catalyst (ferrous ion). Up to 99.6% of TCP removal can be achieved in the process, provided the doses of Fe(II) and H(2)O(2) are selected correctly. The OC of the process was successfully predicted through a kinetic approach in a two-stage model with some simple and measurable parameters, which makes the model useful for predicting, controlling and optimizing the catalyzed oxidation process in the degradation of TCP.

Catalysis↗

PubMed2003

Suicide in Hong Kong: epidemiological profile and burden analysis, 1981 to 2001.

OBJECTIVE: To describe changes of the epidemiological profile of suicides in Hong Kong, and the burden of suicides in terms of years of life lost between 1981 and 2001. DESIGN: Retrospective study. SETTING: Hong Kong. PARTICIPANTS: Data on registered deaths of the Hong Kong population from 1981 to 2001 were retrieved from records of the Census and Statistics Department of the Government of the Hong Kong Special Administrative Region. MAIN OUTCOME MEASURES: Crude, standardised, age- and sex-standardised suicide rates; years of life lost; suicide method used; and rank among leading causes of death. RESULTS: Suicide ranked sixth in the leading cause of deaths and represented about 3% of all deaths each year. The suicide rate has increased from 9.6 per 100000 to 15 per 100000 between 1981 and 2001. The total years of life lost due to suicide increased by 96.0%, from about 9900 years in 1981 to 19 400 years in 2001, whereas the figure for all causes of death decreased by 14.0%, from 274600 years to 236700 years. The total share of years of life lost attributable to suicide deaths has increased from 3.6% to 8.1% and is still increasing, especially among the middle age-groups (30-59 years). The use of charcoal burning as a suicide method has increased from 6.0% before 1998 to more than 28.0% in 2001. CONCLUSION: The burden on the years of life lost due to suicide is underestimated and overlooked. The increase of suicides in recent years has had a significant impact on the years of life lost and can be used as a useful indicator of performance in Hong Kong.

Cause of Death↗

PubMed2002

Localized single-photon wave functions in free space.

We solve the joint open problems of photon localization and single-photon wave functions in the context of spontaneous emission from an excited atom in free space. Our wave functions are well-defined members of a discrete orthonormal function set. Both the degree and shape of the localization are controlled by entanglement mapping onto the atom wave function, even though the atom is remote from the photon.

Journal Article↗

PubMed2002

Combination gemcitabine and cisplatin chemotherapy for metastatic or recurrent nasopharyngeal carcinoma: report of a phase II study.

BACKGROUND: To evaluate the efficacy and toxicity of combination gemcitabine plus cisplatin (GC) chemotherapy in metastatic or recurrent nasopharyngeal carcinoma (NPC). PATIENTS AND METHODS: Forty-four patients of Chinese ethnicity with metastatic or recurrent NPC received ambulatory GC chemotherapy every 28 days (gemcitabine 1000 mg/m(2) days 1, 8 and 15; cisplatin 50 mg/m(2) days 1 and 8). There were 40 male and four female patients with a mean age of 47.4 years. More than half (54.5%) of the patients had received either prior platinum-based chemotherapy and/or radiotherapy to target lesions. RESULTS: There were nine complete responses and 23 partial responses in the 44 patients, achieving an overall response rate of 73% (78% for the 41 assessable patients). The mean duration of response was 5.3 months. Improved subjective symptom-control scores were found in 78% of patients with pre-existing symptoms, while 64% of patients experienced improved general well-being scores. Toxicity was mainly hematological: grade III/IV anemia, granulocytopenia and thrombocytopenia were found in 11, 37 and 16% of cycles, respectively. With a median follow-up of 17.2 months, 62% survived 1 year while 36% were alive and progression free. CONCLUSIONS: Gemcitabine plus cisplatin chemotherapy offers a satisfactory overall response rate, subjective patient improvement and safety profile for metastatic and recurrent NPC.

Adenocarcinoma↗

PubMed2002

Viability of the health protection account in Hong Kong.

OBJECTIVE: To evaluate the viability of the Health Protection Account proposed by the Hong Kong Special Administrative Region Government. DESIGN: Retrospective study. SETTING: The Hospital Authority of Hong Kong. MATERIALS AND METHODS: Data were obtained from hospital and specialist out-patient clinic admissions. The expected health cost for each patient from the age of 65 years to the average age of life expectancy (83 years) was estimated, as was the contribution to these health costs from the Health Protection Account. RESULTS: If individuals contribute 1% of their salary to the Health Protection Account from age 40 to 65 years, the Account can only cover 4% of the actual health costs. CONCLUSION: The Health Protection Account, as proposed, does not ease the financial burden of increasing health care costs in the elderly. Increasing the contribution rate or reducing the age at which contributions to the scheme are started are possible viable options for making the scheme sustainable. However, the current economic situation is such that the public would not favour either of these alternatives. It is envisaged that the Government will need to continue to finance the health care of its citizens by taxation. A gradual increase in user charges might be the only future option for controlling government health expenditure.

Adult↗

PubMed2002

Acute care service utilisation and the possible impacts of a user-fee policy in Hong Kong.

OBJECTIVES: To examine the utilisation pattern of accident and emergency services and to study the possible impact of a user-fee policy on non-emergency attendances in Hong Kong. DESIGN: Retrospective study. METHODS: Four different scenarios are postulated to examine the impact on the number of accident and emergency attendances of a user-fee policy from 2000 to 2029. Patient volume data of accident and emergency attendances for 2000 were made available by the Hospital Authority of Hong Kong. RESULTS: Non-emergency use of the accident and emergency services is the main cause of over-utilisation and contributes to more than 70.0% of its use. Only 22.0% of patients attending accident and emergency departments were admitted to a ward for further treatment. By 2029, the number of accident and emergency attendances would increase by more than 47.0% if the present utilisation pattern prevails. However, if patients at triage levels 3, 4, and 5 were discouraged from using the accident and emergency services, the number of attendances would decrease by 76.4%. CONCLUSION: The proposed user-fee policy would act as a deterrent by preventing unnecessary use of accident and emergency services. However, the use of out-patient services may be increased as a result and attendance should be carefully monitored. Community health education and civic education relating to abuse of accident and emergency services would be effective in reducing over-utilisation of these services.

Accidents↗

PubMed2001

Endovascular treatment of radiation-induced petrous internal carotid artery aneurysm presenting with acute haemorrhage. A report of two cases.

Haemorrhage from rupture of petrous ICA aneurysm can be life threatening and emergency treatment is required. We report 2 cases of radiation-induced petrous internal carotid artery (ICA) aneurysm presenting with acute haemorrhage (epistaxis and otorrhagia) after radiotherapy (RT) for nasopharyngeal carcinoma (NPC). Both patients had a history of RT treatment for NPC. The first patient, a 54-year-old man, presented with sudden severe epistaxis and haemorrhagic shock. The second patient, a 35-year-old man, presented with episodes of severe otorrhagia. The first patient was immediately resuscitated. Obliteration of the aneurysm was performed by endovascular occlusion of the ICA with Guglielmi detachable coils and fibered platinum coils. For the second patient, the aneurysm was treated by deploying a self-expandable stent across the aneurysm neck. In an emergency situation, ruptured petrous ICA aneurysm can be treated with endovascular occlusion of the ICA with microcoils if there is a good collateral blood flow. Alternatively, the aneurysm can be treated by deployment of a stent, which can induce stasis and eventual thrombosis of the aneurysm.

Acute Disease↗

PubMed2001

Acute hemorrhage in late radiation necrosis of the temporal lobe: report of five cases and review of the literature.

Hemorrhage in late cerebral radiation necrosis is a rare complication after radiotherapy for intracranial and extracranial neoplasms. We report 5 cases of acute hemorrhage in late radiation necrosis of the temporal lobe following radiation therapy for nasopharyngeal carcinoma. In a review of the literature, the authors identified a total of 27 such cases. The interval period between the onset of hemorrhage and cranial irradiation is long (mean = 7.8 years). The most prominent histological feature was the proliferation of large, dilated and thin-walled new blood vessels in a background of gliosis and fibrinoid necrosis of vessels. Rupture of these thin-walled new blood vessels is the proposed mechanism of hemorrhage in this condition.

Adult↗

PubMed2000

Brain abscess formation in radiation necrosis of the temporal lobe following radiation therapy for nasopharyngeal carcinoma.

BACKGROUND: Radiation necrosis is a known complication following radiation therapy for extracranial as well as intracranial tumours. However, brain abscess formation in radiation necrosis has not been reported in the literature. We report the clinical data of 6 patients suffering from this condition. METHOD: Twenty-eight patients with radiation necrosis of the temporal lobe following radiotherapy for nasopharyngeal carcinoma were treated surgically at the Department of Neurosurgery, Queen Elizabeth Hospital, Hong Kong between January 1992 and July 1999. Of these, 6 cases were complicated by brain abscess formation. The clinical data of these 6 patients are retrospectively reviewed. FINDINGS: The patients were 5 males and 1 female, ranging in age from 41 to 67 years. Three patients had previous treatment with steroids for the symptomatic radiation necrosis. A history of nasal infection or otitis media was recognised in all 6 patients. All patients were treated surgically by temporal lobectomy and excision of the necrotic tissue together with the abscess cavity. Intra-operatively, a bony defect was observed between the middle cranial fossa and the sphenoid sinus in 3 patients and the bony defect was repaired with a temporalis muscle flap. The species of organisms could only be identified in 3 patients. In 3 patients, the pus smear was positive but the culture was negative. Subsequently, 4 patients recovered and 2 patients died. INTERPRETATION: Cerebral radiation necrosis is a predisposing cause of brain abscess formation. Surgical excision is recommended as the treatment of choice in this group of patients.

Adult↗