Publications by authors named "Kin Wong"

We study kernel-based estimation methods for partially linear varying coefficient additive hazards models, where the effects of one type of covariates can be modified by another. Existing kernel estimation methods for varying coefficient models often use a "local" approach, where only a small local neighborhood of subjects are used for estimating the varying coefficient functions. Such a local approach, however, is generally inefficient as information about some non-varying nuisance parameter from subjects outside the neighborhood is discarded.

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Hot-carrier relaxation above the bandgap results in significant energy losses, making the extraction of hot carriers a critical challenge for efficient hot-carrier photocurrent generation in devices. In this study, we observe long-lived hot carriers in the metal-halide perovskite multiple quantum wells, (BA)(MA)PbI (n = 3), and demonstrate effective hot-hole photocurrent generation using 2D MoS₂ as an extraction layer. A high external quantum efficiency of short-circuit hot-carrier photocurrent of up to 35.

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The logistic regression model for a binary outcome with a continuous covariate can be expressed equivalently as a two-sample density ratio model for the covariate. Utilizing this equivalence, we study a change-point logistic regression model within the corresponding density ratio modeling framework. We investigate estimation and inference methods for the density ratio model and develop maximal score-type tests to detect the presence of a change point.

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Article Synopsis
  • The study focused on congenital anomalies of the kidneys and urinary tracts (CAKUT) and urinary tract infections (UTI) in babies with a single umbilical artery (SUA), analyzing data from 2006 to 2020.
  • A total of 291 babies were examined, revealing a CAKUT prevalence of 7%, with hydronephrosis being the most common anomaly, and many significant conditions identified before birth.
  • The researchers found that congenital heart defects, limb abnormalities, and sacral issues were linked to CAKUT, and 2.1% of the babies developed UTIs, particularly those with CAKUT.
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Key Clinical Message: Lumbar facet fracture-dislocation is rare, often due to hyperflexion with rotational force. Abnormal scoliosis on radiography is a key sign, prompting further imaging. Facetectomy and laminectomy ensure safe reduction, while instrumented fusion is an effective surgical treatment.

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Background: Ventral hernia is a common surgical problem among patients with end-stage kidney disease (ESKD), while the optimal repair technique for small ventral hernias is controversial. This study aimed to compare the outcomes of open suture repair versus biological mesh repair of small ventral hernias with defect size ≤2 cm in ESKD patients.

Method: Data from consecutive ESKD patients who underwent elective ventral hernia repair with defect size ≤2 cm at a single institution from January 2012 to January 2022 were retrospectively reviewed.

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The case-cohort design is a commonly used cost-effective sampling strategy for large cohort studies, where some covariates are expensive to measure or obtain. In this paper, we consider regression analysis under a case-cohort study with interval-censored failure time data, where the failure time is only known to fall within an interval instead of being exactly observed. A common approach to analyzing data from a case-cohort study is the inverse probability weighting approach, where only subjects in the case-cohort sample are used in estimation, and the subjects are weighted based on the probability of inclusion into the case-cohort sample.

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Multivariable Mendelian randomization allows simultaneous estimation of direct causal effects of multiple exposure variables on an outcome. When the exposure variables of interest are quantitative omic features, obtaining complete data can be economically and technically challenging: the measurement cost is high, and the measurement devices may have inherent detection limits. In this paper, we propose a valid and efficient method to handle unmeasured and undetectable values of the exposure variables in a one-sample multivariable Mendelian randomization analysis with individual-level data.

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Background: The COVID-19 global pandemic was caused by a novel coronavirus (SARS-CoV-2), which then became an endemic infection. COVID refers to the World Health Organization's coined acronym for coronavirus disease.

Case Presentation: We have, herein, reported three cases of coronavirus diseases that could have been misdiagnosed as COVID-19.

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Background: This study aims to evaluate the optimal ratio of synthetic bone graft (SBG) material and platelet rich fibrin (PRF) mixed in a metal 3D-printed implant to enhance bone regeneration.

Methods: Specialized titanium hollow implants (5 mm in diameter and 6 mm in height for rabbit; 6 mm in diameter and 5 mm in height for pig) were designed and manufactured using 3D printing technology. The implants were divided into three groups and filled with different bone graft combinations, namely (1) SBG alone; (2) PRF to SBG in 1:1 ratio; (3) PRF to SBG in 2:1 ratio.

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Ultrasound is an acoustic wave which can noninvasively penetrate the skull to deep brain regions, enabling neuromodulation. However, conventional ultrasound's spatial resolution is diffraction-limited and low-precision. Here, we report acoustic nanobubble-mediated ultrasound stimulation capable of localizing ultrasound's effects to only the desired brain region in male mice.

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In cancer studies, it is commonplace that a fraction of patients participating in the study are , such that not all of them will experience a recurrence, or death due to cancer. Also, it is plausible that some covariates, such as the treatment assigned to the patients or demographic characteristics, could affect both the patients' survival rates and cure/incidence rates. A common approach to accommodate these features in survival analysis is to consider a mixture cure survival model with the incidence rate modeled by a logistic regression model and latency part modeled by the Cox proportional hazards model.

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Mendelian randomization has been widely used to assess the causal effect of a heritable exposure variable on an outcome of interest, using genetic variants as instrumental variables. In practice, data on the exposure variable can be incomplete due to high cost of measurement and technical limits of detection. In this paper, we propose a valid and efficient method to handle both unmeasured and undetectable values of the exposure variable in one-sample Mendelian randomization analysis with individual-level data.

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The active site of [NiFe]-hydrogenases contains a strictly-conserved pendant arginine, the guanidine head group of which is suspended immediately above the Ni and Fe atoms. Replacement of this arginine (R479) in hydrogenase-2 from results in an enzyme that is isolated with a very tightly-bound diatomic ligand attached end-on to the Ni and stabilised by hydrogen bonding to the Nζ atom of the pendant lysine and one of the three additional water molecules located in the active site of the variant. The diatomic ligand is bound under oxidising conditions and is removed only after a prolonged period of reduction with H and reduced methyl viologen.

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Contemporary works in change-point survival models mainly focus on an unknown universal change-point shared by the whole study population. However, in some situations, the change-point is plausibly individual-specific, such as when it corresponds to the telomere length or menopausal age. Also, maximum-likelihood-based inference for the fixed change-point parameter is notoriously complicated.

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Ultrasound stimulation is increasingly used to investigate brain function and treat brain diseases due to its high level of safety and precise spatiotemporal resolution. Therefore, it is crucial to understand the underlying mechanisms involved in ultrasound brain stimulation. In this study, we investigate the role of NMDA receptors in mediating the effects of ultrasound on primary hippocampal neurons in mice.

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Article Synopsis
  • Acute locked knee is frequently linked to meniscal tears or intra-articular injuries, but popliteus tendon tears, a less common cause, are often missed as a diagnosis.
  • A case study of a 29-year-old male after a sports injury revealed an intrasubstance tear in the popliteus tendon and a complete tear of the anterior cruciate ligament (ACL), although the menisci were intact.
  • Due to the extension lag from the popliteus tendon tear, ACL reconstruction was delayed, and after six weeks of physiotherapy, the patient regained full knee extension before further surgery for the ligament injury.
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Noninvasive control of neuronal activity in the deep brain can be illuminating for probing brain function and treating dysfunctions. Here, we present a sonogenetic approach for controlling distinct mouse behavior with circuit specificity and subsecond temporal resolution. Targeted neurons in subcortical regions were made to express a mutant large conductance mechanosensitive ion channel (MscL-G22S), enabling ultrasound to trigger activity in MscL-expressing neurons in the dorsal striatum and increase locomotion in freely moving mice.

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Recent technological advances have made it possible to measure multiple types of many features in biomedical studies. However, some data types or features may not be measured for all study subjects because of cost or other constraints. We use a latent variable model to characterize the relationships across and within data types and to infer missing values from observed data.

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Transcranial low-intensity ultrasound is a promising neuromodulation modality, with the advantages of noninvasiveness, deep penetration, and high spatiotemporal accuracy. However, the underlying biological mechanism of ultrasonic neuromodulation remains unclear, hindering the development of efficacious treatments. Here, the well-known Piezo1 was studied through a conditional knockout mouse model as a major mediator for ultrasound neuromodulation ex vivo and in vivo.

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Microglia are the brain's resident immune cells, performing surveillance to promote homeostasis and healthy functioning. While microglial chemical signaling is well-studied, mechanical cues regulating their function are less well-understood. Here, we investigate the role of the mechanosensitive ion channel Piezo1 in microglia migration, pro-inflammatory cytokine production, and stiffness sensing.

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The Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric exchange interaction that stabilizes spin chirality. One scientific and technological challenge is understanding and controlling the interaction between spin chirality and electric field. In this study, we investigate an unconventional electric field effect on interfacial DMI, skyrmion helicity, and skyrmion dynamics in a system with broken inversion symmetry.

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In the first wave of the COVID-19 pandemic, the rapid transmission of a novel virus and the unprecedented disease-mitigation measures have elicited considerable stress in many countries worldwide. Coping with pandemic stress may be differentially related to psychological symptoms across countries characterised by distinct cultural values. This study aimed to: (a) synthesise the literature by investigating the associations between some major types of coping style and psychological symptoms, and (b) investigate the moderating effects of culture on these associations.

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Article Synopsis
  • The Cape Cobra's venom is highly neurotoxic and can lead to fatal paralysis, but its venom composition hasn't been thoroughly researched, and antivenom supply is limited.
  • This study identified the venom's primary components, revealing that about 75.6% are cytotoxins/cardiotoxins and 7.4% are alpha-neurotoxins, while phospholipase A was not detected, indicating a unique venom profile among African cobras.
  • The VINS African Polyvalent Antivenom (VAPAV) showed moderate effectiveness in neutralizing the venom in mice, preventing 75% of deaths from envenoming, although more research is needed to confirm its full efficacy in reversing neuro
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Clustered data frequently arise in biomedical studies, where observations, or subunits, measured within a cluster are associated. The cluster size is said to be informative, if the outcome variable is associated with the number of subunits in a cluster. In most existing work, the informative cluster size issue is handled by marginal approaches based on within-cluster resampling, or cluster-weighted generalized estimating equations.

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