Radiation Hardness Study of Single-Photon Avalanche Diode for Space and High Energy Physics Applications.

The radiation hardness of 180 nm complementary metal-oxide-semiconductor (CMOS) and 55 nm bipolar-CMOS-double-diffused MOS single-photon avalanche diodes (SPADs) is studied using 10 MeV and 100 MeV protons up to a displacement damage dose of 1 PeV/g. It is found that the dark count rate (DCR) levels are dependent on the number and the type of defects created. A new stepwise increase in the DCR is presented. Afterpulsing was found to be a significant contributor to the observed DCR increase. A new model for DCR increase prediction is proposed considering afterpulsing. Most of the samples under test retain reasonable DCR levels after irradiation, showing high tolerance to ionizing and displacement damage caused by protons. Following irradiation, self-healing was observed at room temperature. Furthermore, high-temperature annealing shows potential for accelerating recovery. Overall, the results show the suitability of SPADs as optical detectors for long-term space missions or as detectors for high-energy particles.

A Scaling Law for SPAD Pixel Miniaturization.

The growing demands on compact and high-definition single-photon avalanche diode (SPAD) arrays have motivated researchers to explore pixel miniaturization techniques to achieve sub-10 µm pixels. The scaling of the SPAD pixel size has an impact on key performance metrics, and it is, thereby, critical to conduct a systematic analysis of the underlying tradeoffs in miniaturized SPADs. On the basis of the general assumptions and constraints for layout geometry, we performed an analytical formulation of the scaling laws for the key metrics, such as the fill factor (FF), photon detection probability (PDP), dark count rate (DCR), correlated noise, and power consumption. Numerical calculations for various parameter sets indicated that some of the metrics, such as the DCR and power consumption, were improved by pixel miniaturization, whereas other metrics, such as the FF and PDP, were degraded. Comparison of the theoretically estimated scaling trends with previously published experimental results suggests that the scaling law analysis is in good agreement with practical SPAD devices. Our scaling law analysis could provide a useful tool to conduct a detailed performance comparison between various process, device, and layout configurations, which is essential for pushing the limit of SPAD pixel miniaturization toward sub-2 µm-pitch SPADs.

High fill-factor miniaturized SPAD arrays with a guard-ring-sharing technique.

We present a novel guard-ring-sharing technique to push the limit of SPAD pixel miniaturization, and to demonstrate the operation of SPAD arrays with a 2.2 µm-pitch, the smallest ever reported. Device simulation and preliminary tests suggest that the optimized device design ensures the electrical isolation of SPADs with guard-ring sharing. 4×4 SPAD arrays with two parallel selective readout circuits are designed in 180 nm CMOS technology. SPAD characteristics for the pixel pitch of 2.2, 3, and 4 µm are systematically measured as a function of an active diameter, active-to-active distance, and excess bias. For a 4 µm-pitch, the fill factor is 42.4%, the maximum PDP 33.5%, the median DCR 2.5 cps, the timing jitter 88 ps, and the crosstalk probability is 3.57%, while the afterpulsing probability is 0.21%. Finally, we verified the feasibility of the proposed technique towards compact multi-megapixel 3D-stacked SPAD arrays.

An Image Signal Accumulation Multi-Collection-Gate Image Sensor Operating at 25 Mfps with 32 × 32 Pixels and 1220 In-Pixel Frame Memory.

The paper presents an ultra-high-speed image sensor for motion pictures of reproducible events emitting very weak light. The sensor is backside-illuminated. Each pixel is equipped with multiple collection gates (MCG) at the center of the front side. Each collection gate is connected to an in-pixel large memory unit, which can accumulate image signals captured by repetitive imaging. The combination of the backside illumination, image signal accumulation, and slow readout from the in-pixel signal storage after an image capturing operation offers a very high sensitivity. Pipeline signal transfer from the the multiple collection gates (MCG) to the in-pixel memory units enables the sensor to achieve a large frame count and a very high frame rate at the same time. A test sensor was fabricated with a pixel count of 32 × 32 pixels. Each pixel is equipped with four collection gates, each connected to a memory unit with 305 elements; thus, with a total frame count of 1220 (305 × 4) frames. The test camera achieved 25 Mfps, while the sensor was designed to operate at 50 Mfps.

Comparison of the measurement properties of the Functional Independence and Difficulty Scale with the Barthel Index in community-dwelling elderly people in Japan.

BACKGROUND: The new Functional Independence and Difficulty Scale (FIDS) is a tool for assessing the performance of basic activities of daily living (BADL). Because many BADL measures already exist, it is important to know whether FIDS can offer added benefit over the existing measures. AIMS: This study compared measurement properties between the FIDS and a representative BADL assessment tool, the Barthel Index (BI). METHODS: Recruitment of the participants was done on the basis of convenience sampling. Participants were community-dwelling elderly Japanese subjects (n = 314; age ≥65 years) divided into a healthy elderly group [n = 225; subjects not using long-term care insurance (LTCI) services] and frail elderly group (n = 89; subjects using LTCI services). For each group, ceiling effect (percent participation with the maximum score) was calculated, and it was compared between the two scales. Associations between the FIDS, BI and Medical Outcomes Study Short Form 8 Health Survey (SF-8) were evaluated by Spearman correlation coefficient and partial correlations. Partial correlations coefficients to SF-8 were compared between the two scales. RESULTS: FIDS showed a relatively small ceiling effect compared to the BI. Compared to the BI, FIDS showed a significant positive partial correlation with the broader aspect of the SF-8 subscales, but the strength of correlation between FIDS and SF-8 was weak to negligible. CONCLUSIONS: The FIDS might be less affected by ceiling effect than the BI. Additional studies using a sufficient number of probability samples are needed to clarify whether FIDS has any benefit over BI in terms of correlations with the SF-8.

Effect of Physiological Changes in the Skin on Systemic Absorption of Tacrolimus Following Topical Application in Rats.

Tacrolimus (TL) ointment is a topical treatment for atopic dermatitis, a disease that exhibits various skin conditions. The effect of skin pathologies on the systemic absorption of TL and related side effects remains unknown. This study aimed to investigate factors affecting the cutaneous absorption of TL. We prepared various skin models in hairless rats by tape stripping, injection of prophlogistic material solution (PMS), and continuous subcutaneous adrenaline (Adr) infusion. In vivo absorption studies were conducted, with measurements of transepidermal water loss (TEWL) and skin blood flow as physiological parameters. Very little TL absorption was observed through intact skin. Greater TL absorption was noted in skins with high TEWL values and fully stripped skin with PMS injections. In contrast, Adr infusion, which reduced skin blood flow, resulted in decreased TL absorption through fully stripped skin. Combined use of TL and Adr on skin with PMS injections resulted in suppression of TL absorption. Our results revealed that TL absorption following topical application is affected by alterations in the skin barrier, blood flow, and vascular permeability. We propose an administration plan for TL in a flowchart as a means of preventing systemic side effects.

A stem-less probe using spontaneous pairing between Cy3 and quencher for RNA detection.

We herein report a stem-less probe for the detection of RNA that depends on pairing between Cy3 and nitro methyl red. In our design, two Cy3 residues and two nitro methyl red residues were introduced into an oligonucleotide. In the absence of the target, these dyes formed a complex, and emission of Cy3 was efficiently quenched. Hybridization with the target RNA disrupted this interaction and resulted in Cy3 emission. Under optimized conditions, the signal to background ratio was as high as 180. We demonstrated specific detection of target RNA in cells using a wash-free FISH protocol.

Molecular design of Cy3 derivative for highly sensitive in-stem molecular beacon and its application to the wash-free FISH.

We herein describe a novel in-stem molecular beacon (ISMB) containing multiple Cy3-quencher pairs on d-threoninol scaffolds in the stem region. The designed Cy3 derivative was not significantly quenched by the adjacent nucleobases, self-quenching of the fluorophore was minimal, and the fluorophore did not severely destabilize the duplex. Using newly designed Cy3, we synthesized ISMBs containing two Cy3 moieties. The signal to background ratio of the ISMB containing two Cy3 moieties was above 100, whereas that with one Cy3 was 30. A Cy3-derivative containing ISMB used in a fluorescence in situ hybridization (FISH) detected endogenous ß-actin mRNA in fixed cells without need for washing procedures.

Involvement of intestinal permeability in the oral absorption of clarithromycin and telithromycin.

The involvement of intestinal permeability in the oral absorption of clarithromycin (CAM), a macrolide antibiotic, and telithromycin (TEL), a ketolide antibiotic, in the presence of efflux transporters was examined. In order independently to examine the intestinal and hepatic availability, CAM and TEL (10 mg/kg) were administered orally, intraportally and intravenously to rats. The intestinal and hepatic availability was calculated from the area under the plasma concentration-time curve (AUC) after administration of CAM and TEL via different routes. The intestinal availabilities of CAM and TEL were lower than their hepatic availabilities. The intestinal availability after oral administration of CAM and TEL increased by 1.3- and 1.6-fold, respectively, after concomitant oral administration of verapamil as a P-glycoprotein (P-gp) inhibitor. Further, an in vitro transport experiment was performed using Caco-2 cell monolayers as a model of intestinal epithelial cells. The apical-to-basolateral transport of CAM and TEL through the Caco-2 cell monolayers was lower than their basolateral-to-apical transport. Verapamil and bromosulfophthalein as a multidrug resistance-associated proteins (MRPs) inhibitor significantly increased the apical-to-basolateral transport of CAM and TEL. Thus, the results suggest that oral absorption of CAM and TEL is dependent on intestinal permeability that may be limited by P-gp and MRPs on the intestinal epithelial cells.

Subcellular distribution of azithromycin and clarithromycin in rat alveolar macrophages (NR8383) in vitro.

Azithromycin (AZM), a 15-membered ring macrolide antimicrobial agent, has an antibacterial spectrum that includes intracellular parasitic pathogens that survive or intracellularly multiply in alveolar macrophages (AMs). The subcellular distribution of AZM in AMs was evaluated in vitro in comparison with clarithromycin (CAM). AZM and CAM (50 µM) were applied to the NR8383 cells, used as an in vitro model of AMs, followed by incubation at 37°C or 4°C. The total amount of AZM in cells and subcellular distribution (cell fractionation) was determined after incubation. High level of AZM accumulation was observed in the NR8383 cells at 37°C, and the equilibrium intracellular to extracellular concentration ratio (I/E ratio) was approximately 680, which was remarkably higher than that of CAM (equilibrium I/E ratio=28). The intracellular accumulation of AZM and CAM was temperature dependent. In addition, AZM distributed to the granules fraction including organelles and soluble fraction including cytosol in the NR8383 cells, whereas CAM mainly distributed in soluble fraction. The amount of AZM in the granules fraction was markedly reduced in the presence of ammonium chloride for increase in intracellular pH. These results indicate that AZM is distributed in acidic compartment in AMs. This study suggests that high AZM accumulation in the NR8383 cells is due to the trapping and/or binding in acidic organelles, such as lysosomes.

Myoepithelial carcinoma of the breast with focal rhabdoid features.

Myoepithelial carcinoma of the breast is extremely rare and only 33 cases have been reported in the English literature. Herein, we report a case of myoepithelial carcinoma of the breast with focal rhabdoid features. The patient was a 67-year-old woman, who presented with a lump of the left breast that rapidly grew to 3 cm in diameter within 3 months. Lumpectomy revealed a solid and whitish colored tumor, which was composed mainly of elongated spindle-shaped cells with mild atypia, focal necrosis, and infiltrative margin. In a small area of the lesion, ovoid tumor cells exhibited eccentric nuclei with centrally located nucleoli and plump cytoplasm including round eosinophilic inclusions, resembling a rhabdoid tumor. Immunohistochemically, both types of tumor cells exhibited a myoepithelial phenotype. MIB-1 index was 30%. The cytoplasmic inclusion of the ovoid cells exhibited immunopositivity for both vimentin and cytokeratin. From these findings, this tumor was diagnosed as a myoepithelial carcinoma with focal rhabdoid features. Although rhabdoid features have been reported in some types of malignant and benign tumors, this is the first report of such features in myoepithelial carcinoma of the breast.

Aerosol-based efficient delivery of azithromycin to alveolar macrophages for treatment of respiratory infections.

The efficacy of aerosol-based delivery of azithromycin (AZM) for the treatment of respiratory infections caused by pathogenic microorganisms infected in alveolar macrophages (AMs) was evaluated by comparison with oral administration. The aerosol formulation of AZM (0.2 mg/kg) was administered to rat lungs using a Liquid MicroSprayer(®). The oral formulation of AZM (50 mg/kg) was used for comparison. Time-courses of concentrations of AZM in AMs following administration were obtained, and then the therapeutic availability (TA) was calculated. In addition, the area under the concentrations of AZM in AMs - time curve/minimum inhibitory concentration at which 90% of isolates ratio (AUC/MIC90) were calculated to estimate the antibacterial effects in AMs. The TA of AZM in AMs following administration of aerosol formulation was markedly greater than that following administration of oral formulation. In addition, the AUC/MIC90 of AZM in AMs was markedly higher than the effective values. This indicates that the aerosol formulation could be useful for the treatment of respiratory infections caused by pathogenic microorganisms infected in AMs. This study suggests that aerosolized AZM is an effective pulmonary drug delivery system for the treatment of respiratory infections.

Distribution characteristics of clarithromycin and azithromycin, macrolide antimicrobial agents used for treatment of respiratory infections, in lung epithelial lining fluid and alveolar macrophages.

The distribution characteristics of clarithromycin (CAM) and azithromycin (AZM), macrolide antimicrobial agents, in lung epithelial lining fluid (ELF) and alveolar macrophages (AMs) were evaluated. In the in vivo animal experiments, the time-courses of the concentrations of CAM and AZM in ELF and AMs following oral administration (50 mg/kg) to rats were markedly higher than those in plasma, and the area under the drug concentration-time curve (AUC) ratios of ELF/plasma of CAM and AZM were 12 and 2.2, and the AUC ratios of AMs/ELF were 37 and 291, respectively. In the in vitro transport experiments, the basolateral-to-apical transport of CAM and AZM through model lung epithelial cell (Calu-3) monolayers were greater than the apical-to-basolateral transport. MDR1 substrates reduced the basolateral-to-apical transport of CAM and AZM. In the in vitro uptake experiments, the intracellular concentrations of CAM and AZM in cultured AMs (NR8383) were greater than the extracellular concentrations. The uptake of CAM and AZM by NR8383 was inhibited by ATP depletors. These data suggest that the high distribution of CAM and AZM to AMs is due to the sustained distribution to ELF via MDR1 as well as the high uptake by the AMs themselves via active transport mechanisms.

Efficient drug delivery to lung epithelial lining fluid by aerosolization of ciprofloxacin incorporated into PEGylated liposomes for treatment of respiratory infections.

PURPOSE: The efficacy of aerosolization of ciprofloxacin (CPFX) incorporated into PEGylated liposomes (PEGylated CPFX-liposomes) for the treatment of respiratory infections was evaluated. METHOD: PEGylated CPFX-liposomes with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-n-[methoxy(polyethylene glycol)-2000] (particle size: 100 nm) were prepared, and the drug distribution characteristics in lung epithelial lining fluid (ELF) following aerosolization of PEGylated CPFX-liposomes were examined in rats. Furthermore, the antibacterial effects of PEGylated CPFX-liposomes in ELF were evaluated by pharmacokinetic/pharmacodynamic analysis. RESULTS: The elimination rate of CPFX from ELF following aerosolization of PEGylated CPFX-liposomes was significantly slower than that of CPFX incorporated into unmodified liposomes (unmodified CPFX-liposomes; particle size: 100 nm). According to pharmacokinetic/pharmacodynamic analysis, the PEGylated CPFX-liposomes exhibited potent antibacterial effects against pathogenic microorganisms in ELF. CONCLUSION: This study shows that PEGylated CPFX-liposomes are a useful aerosol-based pulmonary drug delivery system for the treatment of respiratory infections.

[Effects of sperminated pullulans on the pulmonary absorption of insulin].

Sperminated pullulans (SP) having different molecular weights (MWs) were prepared, and the enhancing effect on the pulmonary absorption of insulin in rats was examined. SP acted as enhancers of insulin absorption when a 0.1% solution was applied with insulin simultaneously and their enhancing effects depended on the MW of the SP; the same solutions exhibited low toxicity in the in vivo LDH leaching test. In the in vitro experiments using Calu-3 cells, tight junction-opening effects and a toxic effect of SP in the MTT assay were observed at lower concentrations compared with the in vivo experiments. A mucus layer might interfere with the interaction between SP and the cell surface and might suppress both these effects and toxicity. SP having a high MW will be useful for preparing safe and efficient formulations of peptide and protein drugs. The change in the localization of the tight junction proteins may be related to the permeation-enhancing mechanism of SP.

Aerosol-based efficient delivery of telithromycin, a ketolide antimicrobial agent, to lung epithelial lining fluid and alveolar macrophages for treatment of respiratory infections.

PURPOSE: The efficacy of aerosol-based delivery of telithromycin (TEL), as a model antimicrobial agent, for the treatment of respiratory infections was evaluated by comparison with oral administration. METHOD: The aerosol formulation (0.2 mg/kg) was administered to rat lungs using a Liquid MicroSprayer. RESULTS AND DISCUSSION: The time courses of the concentration of TEL in lung epithelial lining fluid (ELF) and alveolar macrophages (AMs) following administration of an aerosol formulation to rat lungs were markedly higher than that following the administration of an oral formulation (50 mg/kg). The time course of the concentrations of TEL in plasma following administration of the aerosol formulation was markedly lower than that in ELF and AMs. These results indicate that the aerosol formulation is more effective in delivering TEL to ELF and AMs, compared to the oral formulation, despite a low dose and it avoids distribution of TEL to the blood. In addition, the antibacterial effects of TEL in ELF and AMs following administration of the aerosol formulation were estimated by pharmacokinetics/pharmacodynamics analysis. The concentrations of TEL in ELF and the AMs time curve/minimum inhibitory concentration of TEL ratio were markedly higher than the effective values. CONCLUSION: This study indicates that an antibiotic aerosol formulation may be an effective pulmonary drug delivery system for the treatment of respiratory infections.

Effect of surface-mannose modification on aerosolized liposomal delivery to alveolar macrophages.

PURPOSE: The effect of surface-mannose modification on aerosolized liposomal delivery to alveolar macrophages (AMs) was evaluated in vitro and in vivo. METHOD: 4-Aminophenyl-α-D-mannopyranoside (Man) was used for surface-mannose modification, and mannosylated liposomes with various mannosylation rates (particle size: 1000 nm) were prepared. RESULTS: In the in vitro uptake experiments, the uptake of mannosylated liposomes by AMs was increased with the increase in the mannosylation rate over the range 2.4-9.1 mol% Man and became constant at over 9.1%. Thus, the most efficient mannosylation rate was 9.1 mol% Man. Furthermore, free mannose inhibited the uptake of mannosylated liposomes by AMs. This indicates that the uptake mechanism of mannosylated liposomes by AMs is mannose receptor-mediated endocytosis. In the in vivo animal experiments, the mannosylated liposomes (mannosylation rate, 9.1 mol% Man) were more efficiently delivered to AMs after pulmonary aerosolization to rats than nonmodified liposomes and did not harm lung tissues. CONCLUSION: These results indicate that surface-mannose modification is useful for efficient aerosolized liposomal delivery to AMs.

Fluorescence lifetime imaging with a megapixel SPAD camera and neural network lifetime estimation.

Fluorescence lifetime imaging microscopy (FLIM) is a key technology that provides direct insight into cell metabolism, cell dynamics and protein activity. However, determining the lifetimes of different fluorescent proteins requires the detection of a relatively large number of photons, hence slowing down total acquisition times. Moreover, there are many cases, for example in studies of cell collectives, where wide-field imaging is desired. We report scan-less wide-field FLIM based on a 0.5 MP resolution, time-gated Single Photon Avalanche Diode (SPAD) camera, with acquisition rates up to 1 Hz. Fluorescence lifetime estimation is performed via a pre-trained artificial neural network with 1000-fold improvement in processing times compared to standard least squares fitting techniques. We utilised our system to image HT1080-human fibrosarcoma cell line as well as Convallaria. The results show promise for real-time FLIM and a viable route towards multi-megapixel fluorescence lifetime images, with a proof-of-principle mosaic image shown with 3.6 MP.

Angular momentum transfer from photon polarization to an electron spin in a gate-defined quantum dot.

Gate-defined quantum dots (QDs) are such a highly-tunable quantum system in which single spins can be electrically coupled, manipulated, and measured. However, the spins in gate-defined QDs are lacking its interface to free-space photons. Here, we verify that a circularly-polarized single photon can excite a single electron spin via the transfer of angular momentum, measured using Pauli spin blockade (PSB) in a double QD. We monitor the inter-dot charge tunneling which only occur when the photo-electron spin in one QD is anti-parallel to the electron spin in the other. This allows us to detect single photo-electrons in the spin-up/down basis using PSB. The photon polarization dependence of the excited spin state was finally confirmed for the heavy-hole exciton excitation. The angular momentum transfer observed here is a fundamental step providing a route to instant injection of spins, distributing single spin information, and possibly towards extending quantum communication.

Enhancement of the dissolution rate and gastrointestinal absorption of pranlukast as a model poorly water-soluble drug by grinding with gelatin.

The effect of grinding with gelatin on the dissolution behavior and gastrointestinal absorption of a poorly water-soluble drug was evaluated using the antiasthmatic agent, pranlukast, as a model poorly water-soluble drug. A ground pranlukast-gelatin mixture was prepared by grinding equal quantities of pranlukast and gelatin. In the dissolution testing, the dissolution rate of pranlukast in the suspension of the ground pranlukast-gelatin mixture under conditions of pH 3.0, 5.0 and 7.0 was markedly faster than that in the suspension of pranlukast. According to powder X-ray diffractometry (PXRD) and differential scanning calorimetry (DSC) analysis, the enhanced dissolution rate of pranlukast produced by grinding with gelatin was caused by changing the crystalline state of pranlukast into an amorphous state. In an animal experiment, the bioavailability of pranlukast following oral administration of the ground pranlukast-gelatin mixture to rats was threefold greater than that following administration of pranlukast. In the in vitro permeation experiment, the amount of permeated pranlukast through Caco-2 cell monolayers after application of the ground pranlukast-gelatin mixture was greater than that after application of pranlukast. These results suggest that the enhancement of the gastrointestinal absorption of pranlukast by grinding with gelatin is due to enhancement of the dissolution rate. Grinding a poorly water-soluble drug with gelatin is a useful method of enhancing its gastrointestinal absorption.