High-Throughput Generation, Manipulation, and Degradation of Magnetic Nanoparticleladen Alginate Core-shell Beads for Single Bacteria Culturing Analysis

Microbes could be found almost everywhere around us and have significant impacts on our human society. The treatment of microorganisms has long been seen as a complex problem. Till now, most of the genetic and phenotypic information regarding rare species is buried in the bulk microbial colony due to a lack of efficient tools to screen live bacteria. Droplet microfluidics offers a powerful approach to address this problem. However, the interactions among bacteria and their living environment are entirely restricted by the water/oil interfaces in conventional water/oil single emulsion-based microfluidic systems. Here, we demonstrate an oil-mediated all-aqueous microfluidic workflow that can overcome this drawback. In contrast to the previous works, our all-aqueous culturing environment allows cell-cell and cell-environment interactions, thus facilitating the growth of bacteria. Fe₃O₄ magnetic nanoparticles added into the alginate beads enables on-chip manipulation of the microcapsules. The core-shell structure separately encapsulates bacteria and magnetic particles in the core and shell to avoid contamination. We demonstrate the feasibility of this approach by single bacterium culturing in droplet-templated alginate beads. Finally, a new approach is proposed to degrade the alginate beads for post-treatment. This novel microfluidic workflow can create new opportunities for microbial applications, such as bacteria culturing and screening.

Substance abuse effects on urinary tract: methamphetamine and ketamine

INTRODUCTION

Ketamine is known to cause urinary tract dysfunction. Recently, methamphetamine (MA) abuse has become a growing problem in Asia. We investigated the symptomatology and voiding function in patients who abused MA and ketamine and compared their urinary tract toxicity profiles.

METHODS

In the period of 23 months from 1 October 2016, all consecutive new cases of patients presenting with MA- or ketamine-related urological disorder were recruited into a prospective cohort. Polysubstance abuse patients were excluded. Data were analysed by comparison between patients with ketamine abuse and MA abuse. Basic demographic data and initial symptomatology were recorded, and questionnaires on urinary symptoms and the Montreal Cognitive Assessment (MoCA) were used as assessment tools.

RESULTS

Thirty-eight patients were included for analysis. There was a statistically significant difference in mean age between patients with MA and ketamine abuse (27.2 ± 7.2 years and 31.6 ± 4.8 years, respectively, P=0.011). Urinary frequency was the most common urological symptom in our cohort of patients. There was a significant difference in the prevalence of dysuria (ketamine 43.5%, MA 6.7%, P=0.026) and a significant trend in the difference in hesitancy (ketamine 4.3%, MA 26.7%, P=0.069). Overall, questionnaires assessing urinary storage symptoms and voiding symptoms did not find a statistically significant difference between the two groups. The MoCA revealed that both groups had cognitive impairment (ketamine 24.8 ± 2.5, MA 23.6 ± 2.9, P=0.298). CONCLUCSIONS. Abuse of MA caused urinary tract dysfunction, predominantly storage symptoms. Compared with ketamine abuse, MA abuse was not commonly associated with dysuria or pelvic pain.

Management of complications of ketamine abuse: 10 years' experience in Hong Kong

Ketamine is an N-methyl-d-aspartate receptor antagonist, a dissociative anaesthetic agent and a treatment option for major depression, treatment-resistant depression, and bipolar disorder. Its strong psychostimulant properties and easy absorption make it a favourable candidate for substance abuse. Ketamine entered Hong Kong as a club drug in 2000 and the first local report of ketamine-associated urinary cystitis was published in 2007. Ketamine-associated lower-urinary tract symptoms include frequency, urgency, nocturia, dysuria, urge incontinence, and occasionally painful haematuria. The exact prevalence of ketamine-associated urinary cystitis is difficult to assess because the abuse itself and many of the associated symptoms often go unnoticed until a very late stage. Additionally, upper-urinary tract pathology, such as hydronephrosis, and other complications involving neuropsychiatric, hepatobiliary, and gastrointestinal systems have also been reported. Gradual improvement can be expected after abstinence from ketamine use. Sustained abstinence is the key to recovery, as relapse usually leads to recurrence of symptoms. Both medical and surgical management can be used. The Youth Urological Treatment Centre at the Prince of Wales Hospital, Hong Kong, has developed a four-tier treatment protocol with initial non-invasive investigation and management for these patients. Multidisciplinary care is essential given the complex and diverse psychological factors and sociological background that underlie ketamine abuse and abstinence status.

Electrochemical characteristics of amorphous silicon carbide film as a lithium-ion battery anode

The electrochemical reactions of SiC film with Li⁺ have been investigated by electrochemical characterization and X-ray photoelectron spectroscopy.

Population-based survey of the prevalence of lower urinary tract symptoms in adolescents with and without psychotropic substance abuse

OBJECTIVE

To investigate the prevalence of lower urinary tract symptoms in adolescents and the effects of psychotropic substance use.

METHODS

This was a population-based cross-sectional survey using a validated questionnaire in students from 45 secondary schools in Hong Kong randomly selected over the period of January 2012 to January 2014. A total of 11 938 secondary school students (response rate, 74.6%) completed and returned a questionnaire that was eligible for analysis. Individual lower urinary tract symptoms and history of psychotropic substance abuse were documented.

RESULTS

In this study, 11 617 non-substance abusers were regarded as control subjects and 321 (2.7%) were psychotropic substance users. Among the control subjects, 2106 (18.5%) had experienced at least one lower urinary tract symptom with urinary frequency being the most prevalent symptom (10.2%). Females had more daytime urinary incontinence (P<0.001) and males had more voiding symptoms (P=0.01). Prevalence of lower urinary tract symptoms increased with age from 13.9% to 25.8% towards young adulthood and age of ≥18 years (P<0.001). Among the substance users, ketamine was most commonly abused. Substance users had significantly more lower urinary tract symptoms than control subjects (P<0.001). In multivariate analysis, increasing age and psychotropic substance abuse increased the odds for lower urinary tract symptoms. Non-ketamine substance users and ketamine users were respectively 2.8-fold (95% confidence interval, 2.0-3.9) and 6.2-fold (4.1-9.1) more likely than control subjects to develop lower urinary tract symptoms. Females (odds ratio=9.9; 95% confidence interval, 5.4-18.2) were more likely to develop lower urinary tract symptoms than males (4.2; 2.5-7.1) when ketamine was abused.

CONCLUSIONS

Lower urinary tract symptoms are prevalent in the general adolescent population. It is important to obtain an accurate history regarding psychotropic substance use when treating teenagers with lower urinary tract symptoms.

Evaluation of InGaN/GaN light-emitting diodes of circular geometry

Blue GaN light emitting diodes (LEDs) in the shape of cuboids and circular disks have been fabricated by laser micromachining. The proposed circular geometry serves to enhance overall light extraction on a macro-scale and to improve uniformity of the emission pattern due to the rotational symmetry of the chip. Analysis of the chip shaping effect is carried out by ray-tracing simulations and further supported with mathematical modeling using ideal LED models, and subsequently verified with fabricated devices. In comparison, a 10% improvement in overall emission was observed for circular LEDs over the regular cuboids, consistent with simulations and calculations. The measured emission pattern from the circular LED confirms the axial symmetry of the emission beam.

Design of vertically-stacked polychromatic light-emitting diodes

A new design for a polychromatic light-emitting diode (LED) is proposed and demonstrated. LED chips of the primary colors are physically stacked on top of each other. Light emitted from each layer of the stack passes through each other, and thus is mixed naturally without additional optics. As a color-tunable device, a wide range of colors can be generated, making it suitable for display purposes. As a phosphor-free white light LED, luminous efficacy of 30 lm/watt was achieved.

Identifying rodent olfactory bulb structures with micro-DTI

Olfactory bulb (OB) is one of the most developed systems in rodent models with complex neuronal organization and anatomical structures. MR diffusion tensor imaging (DTI) is a non-invasive technique to probe tissue microstructures by examining the diffusion characteristics of water molecules. This paper presents how different OB layers can be identified and quantitatively characterized by micro-DTI using a specially constructed micro-imaging radio frequency (RF) coil. High spatial resolution and high signal to noise ratio (SNR) DTI images of ex vivo rat OBs were obtained. Distinct contrasts were observed between various olfactory bulb layers in trace map, fractional anisotropy (FA) map and FA color map, all in consistency with the known OB neuroanatomy. These experimental results demonstrate the utility of micro-DTI in investigation of complex OB organization.

Polychromatic light-emitting diodes with a fluorescent nanosphere opal coating

A hexagonally close-packed array consisting of fluorescent nanospheres was coated onto short-wavelength GaN light-emitting diodes to demonstrate polychromatic white light emission. The spherical particles self-assemble into ordered three-dimensional opal structures, performing the role of color conversion to generate a polychromatic spectrum with smooth and uniform emission patterns. Different ratios of green and orange-red fluorescent nanospheres were mixed and coated onto high-extraction-efficiency micro-LEDs. Four devices with different shades of white emission were demonstrated. Device A, with a high content of orange-red nanospheres, offers the highest CRI value of 80, whereas device C with a well-balanced ratio of green and orange-red nanospheres exhibits color characteristics closest to ideal white with CIE coordinate at (0.34, 0.34). At 20 mA driving current, the luminous efficacy of the devices A, B, C, and D are 40.5 lm W(-1), 57.7 lm W(-1), 63.1 lm W(-1), and 67.2 lm W(-1) respectively, while the correlated color temperatures (CCTs) of the corresponding devices are 3587, 4778, 5271, and 13 000 K.

Photonic crystal light-emitting diodes fabricated by microsphere lithography

Instead of using conventional electron lithography, a two-dimensional photonic crystal consisting of a hexagonal array of triangular air-holes was created on the surface of a GaN LED substrate using microsphere lithography. The microspheres self-assemble into a single-layered hexagonal-close-packed array acting as an etch mask. A significant enhancement in photoluminescence intensity was recorded from the PhC LED structure. A twofold increase in electroluminescence was observed from the PhC LED compared to an as-grown LED with identical geometry. Besides geometrical factors due to surface roughening, the dispersive nature of PhCs and diffractive properties of the PhC as a grating contribute to the enhancement of light extraction from the LED.

Spectral conversion with fluorescent microspheres for light emitting diodes

An innovative spectral conversion scheme for light emitting diodes using fluorescent microspheres has been demonstrated. An optimally mixed proportion of green and red fluorescent microspheres were coated onto a high-extraction-efficiency GaN micro-LED with emission centred at 470 nm. The microspheres self-assemble into ordered hexagonally arrays, forming regular and uniform coating layers. Devices with cool and warm white emission were achieved. The bluish-white LED has a luminous efficacy of 27.3 lm/W (at 20 mA) with CIE coordinates of (0.26, 0.28) and 8500K CCT, while the yellowish-white LED has a luminous efficacy of 26.67 lm/W (at 20 mA) with CIE coordinates of (0.36, 0.43) and 13000K CCT.

Method for measurement of the density of thin films of small organic molecules

An accurate and sensitive method is reported to measure the thin-film density of vacuum-deposited, small-molecular organic semiconductor materials. A spectrophotometer and surface profiler had been used to determine the mass and thickness of organic thin film, respectively. The calculated density of tris-(8-hydroxyquinolato) aluminum (Alq(3)) thin film was 1.31+/-0.01 gcm(3). Vacuum pressures and thin-film growth rates are found to have less impact on the thin-film density of organic material. However, the thin-film density of organic material strongly depends on its chemical structure and molecular weight. Specifically, the chemical structure determines the density of organic material that affects the molecular volume and intermolecular stacking.

High-efficiency red electrophosphorescence based on neutral bis(pyrrole)-diimine platinum(ii) complex

Efficient red electroluminescence from the excimer or oligomer of neutral phosphorescent bis(pyrrole)-diimine Pt(II) complex has been achieved with maximum external quantum efficiency, luminous efficiency, power efficiency and brightness of 6.5%, 9.0 cd A(-1), 4.0 lm W(-1) and 11 100 cd m(-2), respectively.