Increasing the sensitivity of terahertz split ring resonator metamaterials for dielectric sensing by localized substrate etching.

We demonstrate a significant enhancement in the sensitivity of split ring resonator terahertz metamaterial dielectric sensors by the introduction of etched trenches into their inductive-capacitive gap area, both through finite element simulations and in experiments performed using terahertz time-domain spectroscopy. The enhanced sensitivity is demonstrated by observation of an increased frequency shift in response to overlaid dielectric material of thicknesses up to 18 µm deposited on to the sensor surface. We show that sensitivity to the dielectric is enhanced by a factor of up to ∼2.7 times by the incorporation of locally etched trenches with a depth of ∼3.4 µm, for example, and discuss the effect of the etching on the electrical properties of the sensors. Our experimental findings are in good agreement with simulations of the sensors obtained using finite element methods.

Strain Engineering of the Berry Curvature Dipole and Valley Magnetization in Monolayer MoS_{2}.

The Berry curvature dipole is a physical quantity that is expected to allow various quantum geometrical phenomena in a range of solid-state systems. Monolayer transition metal dichalcogenides provide an exceptional platform to modulate and investigate the Berry curvature dipole through strain. Here, we theoretically demonstrate and experimentally verify for monolayer MoS_{2} the generation of valley orbital magnetization as a response to an in-plane electric field due to the Berry curvature dipole. The measured valley orbital magnetization shows excellent agreement with the calculated Berry curvature dipole, which can be controlled by the magnitude and direction of strain. Our results show that the Berry curvature dipole acts as an effective magnetic field in current-carrying systems, providing a novel route to generate magnetization.

Humidity sensing using THz metamaterial with silk protein fibroin.

In this study, we developed hybrid humidity sensing methods by incorporating silk fibroin protein onto metamaterials, operating in the terahertz (THz) frequencies; the resonant frequency shifted but saturated at a specific thickness due to the limited sensing volume of the metamaterial. From the saturated value, we extracted the dielectric constant for the silk films. We also observed additional resonance shifts when we applied humid air to silk-coated metamaterials, due to the increased water molecule numbers on the film. Frequency shifts depend linearly on relative humidity. Also, in situ THz spectroscopy measurements reveal that the time response is instantaneous within our detection limit, especially upon exposure to humid air, whereas the small slowly decaying component appeared when we applied dry air. The time taken by the slow component in the drying process was 10-50 s, depending on film thickness. This could optimize humidity sensors as a fast and efficient detection tool to measure air humidity.

The siRNA cocktail targeting interleukin 10 receptor and transforming growth factor-ß receptor on dendritic cells potentiates tumour antigen-specific CD8(+) T cell immunity.

Dendritic cells (DCs) are promising therapeutic agents in the field of cancer immunotherapy due to their intrinsic immune-priming capacity. The potency of DCs, however, is readily attenuated immediately after their administration in patients as tumours and various immune cells, including DCs, produce various immunosuppressive factors such as interleukin (IL)-10 and transforming growth factor (TGF)-ß that hamper the function of DCs. In this study, we used small interfering RNA (siRNA) to silence the expression of endogenous molecules in DCs, which can sense immunosuppressive factors. Among the siRNAs targeting various immunosuppressive molecules, we observed that DCs transfected with siRNA targeting IL-10 receptor alpha (siIL-10RA) initiated the strongest antigen-specific CD8(+) T cell immune responses. The potency of siIL-10RA was enhanced further by combining it with siRNA targeting TGF-ß receptor (siTGF-ßR), which was the next best option during the screening of this study, or the previously selected immunoadjuvant siRNA targeting phosphatase and tensin homologue deleted on chromosome 10 (PTEN) or Bcl-2-like protein 11 (BIM). In the midst of sorting out the siRNA cocktails, the cocktail of siIL-10RA and siTGF-ßR generated the strongest antigen-specific CD8(+) T cell immunity. Concordantly, the knock-down of both IL-10RA and TGF-ßR in DCs induced the strongest anti-tumour effects in the TC-1 P0 tumour model, a cervical cancer model expressing the human papillomavirus (HPV)-16 E7 antigen, and even in the immune-resistant TC-1 (P3) tumour model that secretes more IL-10 and TGF-ß than the parental tumour cells (TC-1 P0). These results provide the groundwork for future clinical development of the siRNA cocktail-mediated strategy by co-targeting immunosuppressive molecules to enhance the potency of DC-based vaccines.

Gender differences in chewing discomfort in older South Koreans.

AIMS: The purpose of this study was to identify gender differences in chewing discomfort among elderly Koreans. METHODS: This study used data from 56 616 (weighted sample: 5 638 394) subjects aged over 65 years who participated in the 2011 Community Health Survey in Korea. Of them, 23 059 (weighted sample: 2 368 200, 42.0%) were men and 33 357 (weighted sample: 3 270 194, 58.0%) were women. Data were analysed using chi-square tests and hierarchical logistic regression analyses, with SPSS 20.0. Chewing discomfort was set as the dependent variable, and independent variables were divided into socio-economic factors (place of residence, age, education, monthly household income, basic living security stipend, private insurance, economic activity, living arrangements), general health factors (hypertension, diabetes) and oral health factors (tooth defects, denture use, subjective periodontal health status). RESULTS: A greater proportion of women (50.2%) than men (42.6%) exhibited chewing discomfort (P < 0.001). In men, place of residence, monthly household income, private health insurance, tooth defects and periodontal health were associated with chewing discomfort (P < 0.05). In women, age, education level, basic living security stipend and denture use were associated with chewing discomfort (P < 0.05). CONCLUSIONS: Elderly Korean women experience more severe chewing discomfort than their male counterparts. The factors associated with chewing also differ by gender.

Sulphoxythiocarbamates modify cysteine residues in HSP90 causing degradation of client proteins and inhibition of cancer cell proliferation.

BACKGROUND: Heat shock protein 90 (HSP90) has a key role in the maintenance of the cellular proteostasis. However, HSP90 is also involved in stabilisation of oncogenic client proteins and facilitates oncogene addiction and cancer cell survival. The development of HSP90 inhibitors for cancer treatment is an area of growing interest as such agents can affect multiple pathways that are linked to all hallmarks of cancer. This study aimed to test the hypothesis that targeting cysteine residues of HSP90 will lead to degradation of client proteins and inhibition of cancer cell proliferation. METHODS: Combining chemical synthesis, biological evaluation, and structure-activity relationship analysis, we identified a new class of HSP90 inhibitors. Click chemistry and protease-mass spectrometry established the sites of modification of the chaperone. RESULTS: The mildly electrophilic sulphoxythiocarbamate alkyne (STCA) selectively targets cysteine residues of HSP90, forming stable thiocarbamate adducts. Without interfering with the ATP-binding ability of the chaperone, STCA destabilises the client proteins RAF1, HER2, CDK1, CHK1, and mutant p53, and decreases proliferation of breast cancer cells. Addition of a phenyl or a tert-butyl group in tandem with the benzyl substituent at nitrogen increased the potency. A new compound, S-4, was identified as the most robust HSP90 inhibitor within a series of 19 derivatives. CONCLUSION: By virtue of their cysteine reactivity, sulphoxythiocarbamates target HSP90, causing destabilisation of its client oncoproteins and inhibiting cell proliferation.

Sensitive detection of yeast using terahertz slot antennas.

We demonstrated sensitive detection of individual yeast cells and yeast films by using slot antenna arrays operating in the terahertz frequency range. Microorganisms located at the slot area cause a shift in the resonant frequency of the THz transmission. The shift was investigated as a function of the surface number density for a set of devices fabricated on different substrates. In particular, sensors fabricated on a substrate with relatively low permittivity demonstrate higher sensitivity. The frequency shift decreases with increasing slot antenna width for a fixed coverage of yeast film, indicating a field enhancement effect. Furthermore, the vertical range of the effective sensing volume has been studied by varying the thickness of the yeast film. The resonant frequency shift saturates at 3.5 µm for a slot width of 2 µm. In addition, the results of finite-difference time-domain simulations are in good agreement with our experimental data.

Adenovirus-mediated overexpression of Tcfe3 ameliorates hyperglycaemia in a mouse model of diabetes by upregulating glucokinase in the liver.

AIMS/HYPOTHESIS: Transcription factor E3 (TFE3) has been shown to increase insulin sensitivity by activating insulin-signalling pathways. However, the role of TFE3 in glucose homeostasis is not fully understood. Here, we explored the possible therapeutic potential of TFE3 for the control of hyperglycaemia using a streptozotocin-induced mouse model of diabetes. METHODS: We achieved overabundance of TFE3 in streptozotocin mice by administering an adenovirus (Ad) or adeno-associated virus serotype 2 (AAV2). We also performed an oral glucose tolerance test (OGTT) and insulin tolerance test (ITT). To explore molecular mechanisms of blood glucose control by TFE3, transcriptional studies on the regulation of genes involved in hepatic glucose metabolism were performed using quantitative real-time PCR and chromatin immunoprecipitation assay. The binding site of TFE3 in the liver Gck gene promoter was identified using deletion and site-specific mutation studies. RESULTS: Overabundance of TFE3 resulted in reduced hyperglycaemia as shown by the OGTT and ITT in streptozotocin-treated mice. We observed that TFE3 can upregulate Gck in a state of insulin deficiency. However, glucose-6-phosphatase and cytosolic phosphoenolpyruvate carboxykinase mRNA levels were decreased by Ad-mediated overexpression of Tcfe3. Biochemical studies revealed that the anti-hyperglycaemic effect of TFE3 is due to the upregulation of Gck. In primary cultured hepatocytes, TFE3 increased expression of Gck mRNA. Conversely, small interfering RNA-mediated knockdown of TFE3 resulted in a decrease in Gck mRNA. CONCLUSIONS/INTERPRETATION: This study demonstrates that TFE3 counteracts hyperglycaemia in streptozotocin-treated mice. This effect could be due to the upregulation of Gck by binding of TFE3 to its cognitive promoter region.

Terahertz conductivity of reduced graphene oxide films.

We performed time-domain terahertz (THz) spectroscopy on reduced graphene oxide (rGO) network films coated on quartz substrates from dispersion solutions by spraying method. The rGO network films demonstrate high conductivity of about 900 S/cm in the THz frequency range after a high temperature reduction process. The frequency-dependent conductivities and the refractive indexes of the rGO films have been obtained and analyzed with respect to the Drude free-electron model, which is characterized by large scattering rate. Finally, we demonstrate that the THz conductivities can be manipulated by controlling the reduction process, which correlates well with the DC conductivity above the percolation limit.

Factors affecting unmet healthcare needs of older people in Korea.

BACKGROUND: Despite the fact that the National Health Insurance programmes have ensured universal coverage for Koreans, disparities in access to health care and unmet healthcare needs still exist in Korea. AIM: The purpose of this study was to analyse factors affecting unmet healthcare needs of older people in Korea. METHODS: This study had a cross-sectional, descriptive design using secondary data taken from the Korean National Health and Nutrition Survey conducted in 2007-2009. A complex sampling design was used, and the participants included a nationally representative sample of 3943 people older than 64 years. Socio-demographic variables, subjective health, existence of chronic diseases, quality of life and unmet healthcare needs were included in the study instruments. Logistic regression analyses were performed in order to examine the relationship between unmet healthcare needs and independent variables. RESULTS: According to the results, 29.4% of older women and 14.0% of older men had not visited clinics or hospitals when they needed to obtain healthcare services (unmet healthcare needs) during the past 12 months. Older women [odds ratio (OR) = 1.831, 95% confidence interval (CI) = 1.428-2.347] and those with poor subjective health (OR = 1.708, 95% CI = 1.371-2.126) and arthritis (OR = 1.278, 95% CI = 1.029-1.586) were more likely to have unmet healthcare needs than their counterparts. CONCLUSIONS: Efforts to decrease unmet healthcare needs, targeting high-risk groups (especially for older women), are needed in order to prevent disability, decrease mortality and promote the quality of life of older people.

Mechanical Control of Polaritonic States in Lead Halide Perovskite Phonons Strongly Coupled in THz Microcavity.

We demonstrate the generation and control of polaritonic states in perovskite phonon polaritons, which are strongly coupled in the middle of a flexible Fabry-Perot cavity. We fabricated flexible perovskite films on a microporous substrate coated with graphene oxide, which led to a virtually free-standing film incorporated into the microcavity. Rabi splitting was observed when the cavity resonance was in tune with that of the phonons. The Rabi splitting energy increased as the film thickness increased, reaching 1.9 meV, which is 2.4-fold higher than the criterion for the strong coupling regime. We obtained dispersion curves for various perovskite film thicknesses exhibiting two polariton branches; clear beats between the two polaritonic branches were observed in the time domain. Flexible cavity devices with perovskite phonons enable macroscopic control over the polaritonic energy states through bending processes, which add an additional degree of freedom in the manipulation of polaritonic devices.

Terahertz thermal curve analysis for label-free identification of pathogens.

In this study, we perform a thermal curve analysis with terahertz (THz) metamaterials to develop a label-free identification tool for pathogens such as bacteria and yeasts. The resonant frequency of the metasensor coated with a bacterial layer changes as a function of temperature; this provides a unique fingerprint specific to the individual microbial species without the use of fluorescent dyes and antibodies. Differential thermal curves obtained from the temperature-dependent resonance exhibit the peaks consistent with bacterial phases, such as growth, thermal inactivation, DNA denaturation, and cell wall destruction. In addition, we can distinguish gram-negative bacteria from gram-positive bacteria which show strong peaks in the temperature range of cell wall destruction. Finally, we perform THz melting curve analysis on the mixture of bacterial species in which the pathogenic bacteria are successfully distinguished from each other, which is essential for practical clinical and environmental applications such as in blood culture.

Blocking the immunosuppressive axis with small interfering RNA targeting interleukin (IL)-10 receptor enhances dendritic cell-based vaccine potency.

Improving dendritic cell (DC) functions is highly promising for therapeutic intervention of diverse diseases, including cancer. Immunosuppressive cytokines such as interleukin (IL)-10 produced by DCs themselves (autocrine) and other regulatory immune cells (paracrine) down-regulate functional profiles of DCs through specific cell surface receptors such as IL-10R. Here, we tried to improve DC functions using small interfering RNA (siRNA) technology to block an IL-10R-mediated immunosuppressive axis. DCs modified with siRNA targeting against IL-10R or IL-10 (DC/siIL-10R or DC/siIL-10) led to up-regulation of major histocompatibility complex (MHC) class II, CD40 co-stimulatory molecule, and IL-12 proinflammatory cytokine after lipopolysacharide (LPS) stimulation compared to DC/siGFP. Notably, the LPS-induced functional profiles of DC/siIL-10R were strongly resistant to the addition of recombinant IL-10, which mimicked paracrine IL-10. In contrast, those of DC/siIL-10 were reversed by adding exogenous IL-10. Consistently, DC/siIL-10R generated more human papilloma virus (HPV) E7-specific CD8(+) T cells and stronger anti-tumour effects against E7-expressing TC-1 tumour cells in vaccinated mice than DC/siGFP, as well as DC/siIL-10. Taken together, these results provide the groundwork for future clinical translation of siRNA-mediated strategy targeting IL-10R to enhance DC-based vaccine potency.

Anomalous band formation in arrays of terahertz nanoresonators.

We investigate band formation in one-dimensional periodic arrays of rectangular holes which have a nanoscale width but a length of 100 µm. These holes are tailored to work as resonators in the terahertz frequency regime. We study the evolution of the electromagnetic response with the period of the array, showing that this dependence is not monotonic due to both the oscillating behavior of the coupling between holes and its long-range character.

Light intensity dependence of organic solar cell operation and dominance switching between Shockley-Read-Hall and bimolecular recombination losses.

We investigated the variation of current density-voltage (J-V) characteristics of an organic solar cell (OSC) in the dark and at 9 different light intensities ranging from 0.01 to 1 sun of the AM1.5G spectrum. All three conventional parameters, short-circuit currents (Jsc), open-circuit voltage (Voc), and Fill factor (FF), representing OSC performance evolved systematically in response to light intensity increase. Unlike Jsc that showed quasi-linear monotonic increase, Voc and FF showed distinctive non-monotonic variations. To elucidate the origin of such variations, we performed extensive simulation studies including Shockley-Read-Hall (SRH) recombination losses. Simulation results were sensitive to defect densities, and simultaneous agreement to 10 measured J-V curves was possible only with the defect density of [Formula: see text]. Based on analyses of simulation results, we were able to separate current losses into SRH- and bimolecular-recombination components and, moreover, identify that the competition between SRH- and bimolecular-loss currents were responsible for the aforementioned variations in Jsc, Voc, and FF. In particular, we verified that apparent demarcation in Voc, and FF variations, which seemed to appear at different light intensities, originated from the same mechanism of dominance switching between recombination losses.

Electron beam induced current measurements on single-walled carbon nanotube devices.

We report on electron beam induced current (EBIC) from individual carbon nanotubes (CNTs) which are in contact with metal electrodes. The EBIC signals originate from the diffusion of excess carriers induced by the electron beam bombardment. The EBIC image enables us to locate the individual CNTs efficiently. From the polarity of the EBIC signals we can identify the electrical contacts to the metal electrodes. More importantly, we demonstrate that the EBIC can be used to characterize the local electrical properties of CNT-based devices, such as asymmetry in metal contacts and the presence of defects. EBIC is also observed regardless of the presence of insulating surfaces, indicating that the EBIC is a result of the direct interaction between the CNTs and the electron beams.

Vertical growth and resonator properties of hexagonally shaped zinc oxide nanonails.

We synthesized vertically aligned nail-shaped ZnO nanocrystal arrays on silicon substrates via a combination of a carbothermal reduction method and textured ZnO seeding layers that were precoated on silicon substrates by thermally decomposing zinc acetate, and studied their optical properties using cathodoluminescence (CL) and photoluminescence techniques. The ZnO nanonails show a sharp band-gap edge UV emission and a defect-related broad green emission. Monochromatic CL images of an individual ZnO nanonail show variations in spatial distributions of respective CL bands that had different origins. We attribute the spatial variation of CL images to an uneven distribution of luminescent defects and/or a structure-related light out-coupling from hexagonal ZnO nanostructures. The most distinct CL feature from the hexagonal head of an individual ZnO nanonail was the occurrence of a series of distinct resonant peaks within the visible wavelength range. It appeared that the head of a nanonail played the role of a hexagonal cavity so that polarization-dependent whispering gallery modes were stimulated by electron beam excitation.

Imaging of photocurrent generation and collection in single-layer graphene.

Unlike in linear nanostructures, photocurrent generated in single-layer graphene (SLG) is expected to display two-dimensional characteristics. This allows the investigation of carrier dynamics, in relation to several spatially varying factors (such as the location of photocurrent generation and collection) and the overall electron band configuration of the SLG. In this letter, we use scanning photocurrent microscopy to investigate the spatial mapping of photocurrent generation and collection in SLG in a multielectrode geometry. A strong electric field near metal-graphene contacts leads to efficient photocurrent generation, resulting in >30% efficiency for electron-hole separation. The polarity and magnitude of contact photocurrent are used to study the band alignment and graphene electrical potential near contacts, from which it is shown that there exist large-scale spatial variations in graphene electric potential. Our measurements with a multielectrode device configuration reveal that photocurrent is distributed with a clear directional dependence among different collector electrodes. In the same measurement scheme, we also determine the majority carrier in graphene under different gate conditions by imaging the thermocurrent generated by laser-induced heating of electrodes.

Author Correction: Light Intensity-dependent Variation in Defect Contributions to Charge Transport and Recombination in a Planar MAPbI3 Perovskite Solar Cell.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Identifying different types of microorganisms with terahertz spectroscopy.

Most microbial detection techniques require pretreatment, such as fluorescent labeling and cultivation processes. Here, we propose novel tools for classifying and identifying microorganisms such as molds, yeasts, and bacteria based on their intrinsic dielectric constants in the THz frequency range. We first measured the dielectric constant of films that consisted of a wide range of microbial species, and extracted the values for the individual microbes using the effective medium theory. The dielectric constant of the molds was 1.24-1.85, which was lower than that of bacteria ranging from 2.75-4.11. The yeasts exhibited particularly high dielectric constants reaching 5.63-5.97, which were even higher than that of water. These values were consistent with the results of low-density measurements in an aqueous environment using microfluidic metamaterials. In particular, a blue shift in the metamaterial resonance occurred for molds and bacteria, whereas the molds have higher contrast relative to bacteria in the aqueous environment. By contrast, the deposition of the yeasts induced a red shift because their dielectric constant was higher than that of water. Finally, we measured the dielectric constants of peptidoglycan and polysaccharides such as chitin, α-glucan, and ß-glucans (with short and long branches), and confirmed that cell wall composition was the main cause of the observed differences in dielectric constants for different types of microorganisms.