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Femtosecond laser-textured black silicon (fs-bSi) is known to suffer from heavy minority carrier recombination resulted from laser irradiation. In this paper, we demonstrate that the thermal annealing step, generally used to recover the crystal damage, could improve the minority carrier lifetime of the fs-bSi wafers only from 8 μs to 12 μs, even when using as high temperature as 800 °C. However, with an optimized wet chemical etching process, we obtain a high minority carrier lifetime of 2 ms without sacrificing the optical properties of the samples, i.e., the absorptance remains above 90% in the studied wavelength range (250–1100 nm). Increasing the etching time further leads to a total recovery of the lifetime up to 10.5 ms, which proves that the damage originating from the fs-laser texturing extends only to the near-surface layer (a few μm) of silicon.

Lataa julkaisu, kun saatavilla. In semiconductor manufacturing, black silicon (bSi) has traditionally been considered as a sign of unsuccessful etching. However, after more careful consideration, many of its properties have turned out to be so superior that its integration into devices has become increasingly attractive. In devices where bSi covers the whole wafer surface, such as solar cells, the integration is already rather mature and different bSi fabrication technologies have been studied extensively. Regarding the integration into devices where bSi should cover only small selected areas, existing research focuses on device properties with one specific bSi fabrication method. Here, we fabricate bSi patterns with varying dimensions ranging from millimeters to micrometers using three common bSi fabrication techniques, i.e., plasma etching, metal-assisted chemical etching (MACE) and femtosecond-laser etching, and study the corresponding fabrication characteristics and resulting material properties. Our results show that plasma etching is the most suitable method in the case of µm-scale devices, while MACE reached surprisingly almost the same performance. Femtosecond-laser has potential due to its maskless nature and capability for hyperdoping, however, in this study its moderate accuracy, large silicon consumption and spreading of the etching damage outside the bSi region left room for improvement.

Metal-assisted chemical etching (MACE) is a widely applied process for fabricating Si nanostructures. As an electroless process, it does not require a counter electrode, and it is usually considered that only holes in the Si valence band contribute to the process. In this work, a charge carrier collecting p-n junction structure coated with silver nanoparticles is used to demonstrate that also electrons in the conduction band play a fundamental role in MACE, and enable an electroless chemical energy conversion process that was not previously reported. The studied structures generate electricity at a power density of 0.43 mW/cm2 during MACE. This necessitates reformulating the microscopic electrochemical description of the Si-metal-oxidant nanosystems to separately account for electron and hole injections into the conduction and valence band of Si. Our work provides new insight into the fundamentals of MACE and demonstrates a radically new route to chemical energy conversion by solar cell-inspired devices.

Metal-assisted chemical etched (MACE; also known as MacEtch or MCCE) nanostructures are utilized widely in the solar cell industry due to their excellent optical properties combined with a simple and cost-efficient fabrication process. The photodetection community, on the other hand, has not shown much interest toward MACE due to its drawbacks, including insufficient surface passivation, increased junction recombination, and possible metal contamination, which are especially detrimental to p-n photodiodes. Here, we aim to change this by demonstrating how to fabricate high-performance MACE p-n photodiodes with above 90% external quantum efficiency (EQE) without external bias voltage at 200-1000 nm and dark current less than 3 nA/cm2 at -5 V using industrially applicable methods. The key is to utilize an induced junction created by an atomic layer deposited (ALD) highly charged Al2O3 thin film that simultaneously provides efficient field-effect passivation and full conformality over the MACE nanostructures. Achieving close to ideal performance demonstrates the vast potential of MACE nanostructures in the fabrication of high-performance low-cost p-n photodiodes.

Copper sulfide nanoparticles represent a class of dual-functional materials whose optical properties are dominated by interband electronic transitions and intraband plasmon resonances, both of whic...

Optically excited plasmonic nanostructures may function as molecular scissors with unique capabilities to cleave specific chemical bonds in molecular adsorbates through either plasmon-enhanced intr...

Plasmon-driven photocatalysis has emerged as a paradigm-shifting approach, based on which the energy of photons can be judiciously harnessed to trigger interfacial molecular transformations on metallic nanostructure surfaces in a regioselective manner with nanoscale precision. Over the past decade, the formation of aromatic azo compounds through plasmon-driven oxidative coupling of thiolated aniline-derivative adsorbates has become a testbed for developing detailed mechanistic understanding of plasmon-mediated photochemistry. Such photocatalytic bimolecular coupling reactions may occur not only between thiolated aniline-derivative adsorbates but also between their nonthiolated analogs. How the nonthiolated adsorbates behave differently from their thiolated counterparts during the plasmon-driven coupling reactions, however, remains largely unexplored. Here, we systematically compare an alkynylated aniline-derivative, para-ethynylaniline, to its thiolated counterpart, para-mercaptoaniline, in terms of their adsorption conformations, structural flexibility, photochemical reactivity, and transforming kinetics on Ag nanophotocatalyst surfaces. We employ surface-enhanced Raman scattering as an in situ spectroscopic tool to track the detailed structural evolution of the transforming molecular adsorbates in real time during the plasmon-driven coupling reactions. Rigorous analysis of the spectroscopic results, further aided by density functional theory calculations, lays an insightful knowledge foundation that enables us to elucidate how the alteration of the chemical nature of metal–adsorbate interactions profoundly influences the transforming behaviors of the molecular adsorbates during plasmon-driven photocatalytic reactions.

Optically excited plasmonic nanostructures exhibit unique capabilities to catalyze interfacial chemical transformations of molecules adsorbed on their surfaces in a regioselective manner through anomalous reaction pathways that are inaccessible under thermal conditions. The mechanistic complexity of plasmon-driven photocatalysis is intimately tied to a series of photophysical and photochemical processes associated with the radiative and non-radiative decay of localized plasmon resonances in metallic nanostructures. Plasmon-enhanced Raman spectroscopy combines ultrahigh detection sensitivity with unique time-resolving and molecular finger-printing capabilities, ideal for detailed kinetic and mechanistic studies of photocatalytic interfacial transformations of molecular adsorbates residing in the plasmonic hot spots. Through systematic case studies of several representative reactions, we demonstrate how plasmon-enhanced Raman spectroscopy can be judiciously utilized as a unique in situ spectroscopic tool to fine-resolve the detailed molecule-transforming processes on the surfaces of optically excited plasmonic nanostructures in real time during the photocatalytic reactions. We further epitomize the mechanistic insights gained from in situ plasmon-enhanced Raman spectroscopic measurements into several central materials design principles that can be employed to guide the rational optimization of the photocatalyst structures and the nanostructure-molecule interfaces for plasmon-mediated surface chemistry.

Although the intriguing plasmonic properties of noble metal nanoparticles originate from the collective oscillations of free electrons in the conduction band, nanoparticles of doped semiconductors may also exhibit metal-like, plasmonic features that are dictated by the resonantly excited free hole oscillations in the valence band. Here, we combine Au, a representative free electron metal, with copper sulfides, a class of plasmonic p-type semiconductors, in a core-shell nanoparticle geometry to construct dual-plasmonic hetero-nanostructures displaying unique multiplex optical characteristics dominated by plasmonic hole oscillations in the semiconductor shells, plasmonic electron oscillations in the metallic cores, and interband electronic transitions from the valence to conduction bands. Through deliberately designed colloidal synthesis, we are able to selectively grow nanoshells comprising copper sulfides of specifically targeted crystalline phases and Cu/S stoichiometries, such as covellite (CuS), digenite (Cu1.8S), and nonstoichiometric Cu2-xS, on the surfaces of Au nanoparticle cores. Our synthetic approach enables us not only to finely control the core and shell dimensions but also to systematically adjust the free hole concentrations in the semiconductor shells, which forms the keystone for the fine tuning of multiple optical resonance modes supported by these hybrid hetero-nanostructures. The dual-plasmonic Au@copper sulfide core-shell nanoparticles exhibit unique multimodal photothermal and photocatalytic behaviors upon selective photoexcitations of different optical transitions at their characteristic resonant frequencies, allowing us to quantitatively evaluate and rigorously compare the intrinsic photothermal and photocatalytic efficacies of multiple types of hot charge carriers, all photoexcited in the same hybrid nanoparticles but with distinct photophysical origins, excited-state lifetimes, energy distributions, and transfer pathways.

Raman spectroscopy was used to establish direct evidence of heterometallic metal centers in a metal-organic framework (MOF). The Cu3(BTC)2 MOF HKUST-1 (BTC3- = benzenetricarboxylate) was transmetalated by heating it in a solution of RhCl3 to substitute Rh2+ ions for Cu2+ ions in the dinuclear paddlewheel nodes of the framework. In addition to the Cu-Cu and Rh-Rh stretching modes, Raman spectra of (CuxRh1-x)3(BTC)2 show the Cu-Rh stretching mode, indicating that mixed-metal Cu-Rh nodes are formed after transmetalation. Density functional theory studies confirmed the assignment of a Raman peak at 285 cm-1 to the Cu-Rh stretching vibration. Electron paramagnetic resonance spectroscopy experiments further supported the conclusion that Rh2+ ions are substituted into the paddlewheel nodes of Cu3(BTC)2 to form an isostructural heterometallic MOF, and electron microscopy studies showed that Rh and Cu are homogeneously distributed in (CuxRh1-x)3(BTC)2 on the nanoscale.

The understanding of calcium phosphate precipitation is of major interest in different fields of science, including medicine, biomaterials, and physical chemistry. The presence of additive biomacromolecules has been known to influence various stages of the precipitation process from nucleation to crystal growth. In the current work, well-defined sequences of short, negatively charged peptides, oligo(l-glutamic acids), were utilized as a model, inspired by contiguous sequences of acidic amino acids in natural biomineralization proteins. The precipitate morphology and phases, the element time profile in solution and in the precipitates, as well as the kinetics during the precipitation process were analyzed to explain the effect of these short peptides on calcium phosphate precipitation. The results show that peptides can delay the phase transformation of an amorphous precursor phase to hydroxyapatite and that there is an optimal chain length for this effect at a given concentration of peptide. This study is the first part of a two-part series and is followed by a subsequent work to reveal the mechanism by which these short peptides influence the calcium phosphate precipitation.

The femtosecond-pulsed laser processed black silicon (fs-bSi) features high absorptance in a wide spectral range but suffers from high amount of laser induced damage as compared to bSi fabricated by other methods. Here, we aim to minimize the charge carrier recombination in the fs-bSi caused by laser damage as indicated by the sub-bandgap absorption and as quantified by the carrier lifetime, while maintaining high absorption in the above-bandgap. The effect of the laser parameters, including the focal position, the average power, and the scan speed are systematically studied by characterizing the surface morphology, the absorptance spectra, and the minority-carrier recombination lifetime. For the surface passivation of fs-bSi we use the well-established atomic layer deposited (ALD) Al2O3. The results show that with the tailored laser parameters, high average absorptance of about 96% in the visible range and minority carrier lifetime of 54 μs at the injection level of Δn = 1 ∙ 1015 cm−3 can be obtained simultaneously. This work paves the way towards high-performance broadband optoelectronic devices based on surface passivated fs-bSi.

We study the surface morphology, optical absorption (400–1100 nm), and carrier lifetime of black silicon fabricated by femtosecond (fs) laser in air. We explore a large laser parameter space, for which we adopt a single parameter ξ to describe the cumulative fluence delivered to the sample. We also study the laser-oxidized surface layer by measuring its photoluminescence spectra and comparing its effect on the aforementioned properties. Our study in a broad range of ξ is instructive in choosing laser parameters when targeting different applications.

The Bluest Eye is the first and also the representative work of American female black writer Toni Morrison. Published in 1970, The Bluest Eye is an innovative novel exploring themes of race, class, and beauty standards. Eco-translatology, the translatology theory devised by Chinese professor Hu Gengshen, gains insights from the tenets of natural selection and provides its description and interpretation of translation activities. Based on the three-dimensional transformation of Eco-translatology, this paper analyzes Yang Xiangrong’s Chinese translation of The Bluest Eye. In recent years, the three-dimensional transformation of Eco-translatology has been analyzed in many fields of translation, but it has never been applied to Toni Morrison’s works. Therefore, this paper explores the feasibility of the three-dimensional transformation of Eco-translatology to guide the translation of The Bluest Eye, and finally comes to the conclusion that Yang maintains the ecological balance and harmony between the source language and the target language.

Growing SiO2 layer by wet-chemical oxidation of Si surfaces before growth of another insulating film(s) is a used method to passivate Si interfaces in applications (e.g., solar cell, photodiode) at low temperatures (LT) below 450 oC. We report on potential of LT ultrahigh-vacuum (UHV) treatments combined with the wet-chemical oxidation, by investigating effects of LT-UHV oxidation after the wet-chemical growth of SiO2 and before growing Al2O3 film on top of SiO2/Si. This method modifies the SiO2/Si and is found to (i) decrease defect- level density, (ii) increase negative fixed charge density, and (iii) increase carrier lifetime for Al2O3/SiO2/p-Si, as compared to state-of-the-art SiO2/p-Si reference interfaces without LT-UHV. X-ray photoelectron spectroscopy shows that the LT-UHV treatment decreases amount of Si+3 oxidized atoms in chemically grown SiO2 and also amount of carbon contamination. In order to pave the way for further tests of LT-UHV in silicon technology, we present a design of simple UHV instrument. The above-described benefits are reproduced for 4-inch silicon wafers by means of the instrument, which is further utilized to make LT-UHV treatments for complementary SiO2/Si interfaces of the native oxide at silicon diode sidewalls to decrease the reverse bias leakage current of the diodes.

Background The Short Physical Performance Battery (SPPB) is an established test of physical performance. We provide reference values for SPPB and determine SPPB performance and cut-offs in assessing sarcopenia for Asian community-dwelling older adults. Methods Five hundred thirty-eight (57.8% women) community-dwelling adults aged 21–90 years were recruited. SPPB and its subtest scores and timings (8 ft. gait speed (GS), five-times repeated chair sit-to-stand (STS) and balance) were determined. Appendicular lean mass divided by height-squared, muscle strength (handgrip) and physical performance (6 m GS, STS and SPPB) were assessed to define sarcopenia for various Asian criteria. Area under the ROC curve (AUC) was used to assess performance of SPPB and subtests in discriminating sarcopenia in adults aged ≥60 years. Optimal SPPB and GS subtest cut-offs for each sarcopenia criterion were determined by maximizing sensitivity and specificity. Results The mean SPPB score was 11.6(SD 1.1) in men and 11.5(SD1.2) in women. Majority of participants(≥50%) aged 21–80 years achieved the maximum SPPB score. SPPB total and subtest scores generally decreased with age (all p Conclusions Population-specific normative SPPB values are important for use in diagnostic criteria and to interpret results of studies evaluating and establishing appropriate treatment goals. Performance on the SPPB should be reported in terms of the total sum score and registered time to complete the repeated-chair STS and 8-ft walk tests. The performance of GS subtest was comparable to SPPB and could be a useful, simple and accessible screening tool for discriminating severe sarcopenia in community-dwelling older adults.

The design of improved materials for orthopedic implants and bone tissue engineering scaffolds relies on materials mimicking the properties of bone. Calcium phosphate (Ca-PO4)-mineralized collagen fibrils arranged in a characteristic hierarchical structure constitute the building blocks of mineralized vertebrate tissues and control their biomechanical and biochemical properties. Large, flexible, acidic noncollagenous proteins (ANCPs) have been shown to influence collagen mineralization but little is known about mineralization mechanisms with the aid of small proteins. Osteocalcin (OCN) is a small, highly structured biomolecule known as a multifunctional hormone in its undercarboxylated form. Here, we examined the potential mechanism of collagen intrafibrillar mineralization in vitro mediated by OCN as a model protein. Rapid and random extrafibrillar mineralization of flakey Ca-PO4 particles was observed by transmission electron microscopy mainly on the outer surfaces of collagen fibrils of a preformed collagen scaffold in the absence of the protein. In contrast, the protein stabilized hydrated, spherical nanoclusters of Ca-PO4 on the outer surface of the fibrils, thereby retarding extrafibrillar mineralization. The nanoclusters then infiltrated the fibrils resulting in intrafibrillar mineralization with HAP crystals aligned with the fibrils. This mechanism is similar to that observed for unstructured ANCPs. Results of fibrillogenesis and immunogold labeling studies showed that OCN was associated primarily with the fibrils, consistent with ex vivo studies on mineralizing turkey tendon. The present findings contribute to expanding our understanding of collagen intrafibrillar mineralization and provide insight into design synthetic macromolecular matrices for orthopedic implants and bone regeneration.

Hydroxyapatite (HAP) is an extensively used orthopedic biomaterial because of its high biocompatibility and osteoconductivity. Implant-related infection is a major cause of orthopedic device failure. Previous research showed that silver-doped hydroxyapatite nanoparticles (Ag-HAP NPs) have prominent antimicrobial activity, but their biocompatibility and plasma protein response remained unexplored. Here we investigated the effects of synthesis conditions on Ag-HAP NP antimicrobial (

Objective: To investigate the feasibility and effect of minimal media lower hemisternotomy for cardiac surgery under cardiopulmonary bypass (CPB) in infant congenital heart disease. Methods: In our hospital from May 2019 to October 2019, 170 infants with congenital heart disease underwent surgical treatment (median age 6.6 months; weight 6.0 kg). They were divided into 2 groups: those with conventional chest median incision and those with minimal sternotomy. Minimal lower hemisternotomy began from the third intercostal level and ended 0.5 cm above the xiphoid, just enough to insert a small sternal distractor. Results: There was no significant difference between the 2 groups in CPB time. The operation time of small incision group was slightly longer (P < .05). There was no difference in prognosis between the 2 groups, but the wound length of the small incision group was significantly reduced (4.0 ± 0.5 versus 7.8 ± 0.8 cm, P < .05). Time of intensive care unit and hospital stay was shorter among hemisternotomy patients at a statistically significant level (P < .05). Conclusion: Minimal media lower hemisternotomy with the basic advantages of the sternal incision can expose the various parts of the heart, which meets most cardiac exploration and surgical operation needs, and the incision may still be extended if necessary. Lower hemisternotomy appears to be a safe, effective, and versatile alternative for many surgical interventions in infants with congenital heart disease.

Background Sarcopenia and obesity are reportedly associated with risk of cognitive decline, and sarcopenic obesity (SO) heightens the risk, but the evidence is sparse and inconclusive. This study aimed to examine the association between SO and cognitive impairment. Methods A total of 542 community-dwelling adults aged between 21 and 90 years were recruited. All participants were assessed for body composition (dual X-ray absorptiometry), handgrip strength (HGS), gait speed (GS), and cognitive function (Repeatable Battery for the Assessment of Neuropsychological Status). Sarcopenia was defined by the presence of low appendicular lean mass index (ALMI) and low HGS or low GS according to the 2019 Asian Working Group for Sarcopenia criteria, and obesity was defined based on the upper two quintiles of fat mass index (FMI). Results Sarcopenia alone or in combination with obesity were not significantly associated with cognitive impairment after controlling for confounding variables. Obesity on its own was significantly associated with greater odds of impaired attention (OR: 2.05, 95%CI 1.12–3.82). Low ALMI was not associated, but low HGS, slow GS, and high FMI were individually associated with cognitive impairment: low HGS and immediate memory (OR: 1.91, 95% CI 1.04–3.49); low GS and immediate memory (OR: 2.17, 95% CI 1.26–3.72); high FMI and attention (OR: 2.06, 95% CI 1.22–3.51). Co-occurring high FMI with either low HGS or slow GS exacerbated the observed odds of global and domain-specific (attention, visuospatial) cognitive impairment. Conclusions Lean mass is not relevant, whereas muscle strength and physical performance or adiposity are relevant in defining sarcopenia or sarcopenic obesity in terms of their cognitive impacts.

Objectives The “timed up and go” (TUG) test is a simple and widely used test of overall functional mobility. There is a paucity of TUG normative data among Asian individuals who differ in habitual gait speed and fall risk from Western population. The objectives of this study were to determine TUG reference values and optimum cutoffs predicting prevalent and incident disability for community-dwelling adults. Design One cross-sectional (Study 1–Yishun Study) and one longitudinal (Study 2–Singapore Longitudinal Aging Study) study in Singapore. Setting and Participants Study 1 comprised 538 nondisabled, community-dwelling adults aged between 21 and 90 years. Study 2 comprised 1356 community-dwelling older adults aged ≥55 years followed for 3 years. Methods Study 1 collected TUG reference values and assessed physiological fall risk (PFR) using the Physiological Profile Assessment (PPA). Study 2 assessed association of TUG with disability with the Barthel Index and the Lawton scale at baseline and follow-up. Results From Study 1, mean TUG time for individuals aged 60 to 74 years was 9.80 seconds, shorter than values reported for Westerners of 12.30 seconds. It was significantly associated with high PFR [odds ratio (OR) 1.14, 95% confidence interval (CI) 1.03–1.27], 74.0% agreement, Cohen's kappa = 0.314 (95% CI 0.238–0.390); area under the curve = 0.85 (95% CI 0.80–0.90). A TUG cutoff of 10.2 seconds discriminated high PFR from low PFR with 84.4% sensitivity and 72.6% specificity. In Study 2, the threshold for observing significantly increased risk of disability was ≥9.45 seconds for prevalent disability (OR 2.98, 95% CI 1.41–6.78), functional decline (OR 2.68, 95% CI 1.33–5.80), and incidental disability (OR 2.25, 95% CI 1.08–4.97). Conclusions and Implications TUG reference values and cutoff predicting disability for community-dwelling older adults in Singapore are consistent with Asian data and lower than for Western individuals. TUG could be used to guide development and evaluation of risk screening of adverse health outcomes across the life span in Singapore.

Nanostructured surfaces are known to provide excellent optical properties for various photonics devices. Fabrication of such nanoscale structures to germanium (Ge) surfaces by metal assisted chemical etching (MACE) is, however, challenging as Ge surface is highly reactive resulting often in micron-level rather than nanoscale structures. Here we show that by properly controlling the process, it is possible to confine the chemical reaction only to the vicinity of the metal nanoparticles and obtain nanostructures also in Ge. Furthermore, it is shown that controlling the density of the nanoparticles, concentration of oxidizing and dissolving agents as well as the etching time plays a crucial role in successful nanostructure formation. We also discuss the impact of high mobility of charge carriers on the chemical reactions taking place on Ge surfaces. As a result we propose a simple one-step MACE process that results in nanoscale structures with less than 10% surface reflectance in the wavelength region between 400 nm and 1600 nm. The method consumes only a small amount of Ge and is thus industrially viable and also applicable to thin Ge layers., Comment: 8 pages, 4 figures. Full citation details and link to manuscript published in Nanotechnology were added

Low-temperature (LT) passivation methods ( 700oC). Therefore, the LT passivation of SiOx/Si has been, since long, a research topic to improve applications performance. Here, we demonstrate that a LT (

Background: While there have been studies in Singapore on the prevalence and economic burden of osteoporotic hip fracture, there is a severe lack of reference data on bone mineral density and prevalence of osteoporosis. The purpose of this study is to establish the reference values for BMD and compare prevalence of osteoporotic conditions using other available reference values so as to better understand the status of bone health in Singaporean adults.Methods: We carried out a population-based cross-sectional study using dual-energy x-ray absorptiometry (Hologic Discovery Wi) to measure the bone mineral density of Singaporean adults aged ³ 21 years. A total of 542 participants were recruited from the large north-eastern residential town of Yishun. We computed T- scores (denoted by TSG) for each individual in the study. Similar diagnoses were also done based on T-scores provided by the densitometer (TDXA), NHANES database (TNHANES), and China (TCHN), and the differences in prevalence compared. We then compared the concordance between TSG and TDXA in the classification of osteoporosis. Osteoporosis was defined according to criteria by the World Health Organization (WHO).Results: Peak lumbar spine BMD was 1.093±0.168g/cm2 in women, and 1.041±0.098g/cm2 for men. Peak whole-body BMD was 1.193±0.93g/cm2 in women at, and 1.224±0.112g/cm2 for men. Prevalence of osteoporosis based on lumbar spine was 9.3% in postmenopausal women, and 0.7% in men after 50 years of age. The percentage difference in prevalence range from 60.5 - 163.6%, when using reference values from TDXA, TNHANES, and TCHN. Comparing diagnosis using TDXA and TSG cut-off values, 28 versus 15 women were diagnosed as osteoporotic respectively. The kappa statistics was 0.81 for women and 0.85 for men. Conclusion: Our study shows that T-scores provided by DXA manufacturer over-diagnosed osteoporosis in Singaporeans, and the prevalence of osteoporotic conditions is not accurately represented. This over-diagnosis may result in unnecessary treatment in some individuals.

Background: While there have been studies in Singapore on the prevalence and economic burden of osteoporotic hip fracture, there is a severe lack of reference data on bone mineral density and prevalence of osteoporosis. The purpose of this study is to establish the reference values for BMD and compare prevalence of osteoporotic conditions using other available reference values so as to better understand the status of bone health in Singaporean adultsMethods: We carried out a population-based cross-sectional study using dual-energy x-ray absorptiometry (Hologic Discovery Wi) to measure the bone mineral density of Singaporean adults aged ³ 21 years. 314 women and 223 men were recruited from the large north-eastern residential town of Yishun. We computed T- scores (denoted by TSG) for each individual in the study. Similar diagnoses were also done based on T-scores provided by the densitometer (TDXA), NHANES database (TNHANES), and China (TCHN), and the differences in prevalence compared. We then compared the concordance between TSG and TDXA in the classification of osteoporosis. Osteoporosis was defined according to criteria by the World Health Organization (WHO).Results: Peak lumbar spine BMD was 1.090±0.168g.cm-2 in women, and 1.041±0.098g.cm-2 for men. Peak whole body BMD was 1.193±0.93g.cm-2 in women at, and 1.224±0.112g.cm-2 for men. Prevalence of osteoporosis based on lumbar spine was 9.3% in women, and 0.7% in men. The percentage difference in prevalence range from 60.5 - 163.6%, when using reference values from TDXA, TNHANES, and TCHN. Among the 28 women who were diagnosed as osteoporotic by TDXA, 16.5% only had osteopenia according to TSG. The kappa statistics was 0.81 for women and 0.85 for men. Conclusion: Our study shows that T-scores provided by DXA manufacturer over-diagnosed osteoporosis in Singaporeans, and the prevalence of osteoporotic conditions is not accurately represented. This over-diagnosis may result in unnecessary treatment in some individuals.

Background: The prevalence of sarcopenic obesity (SO) and its effect on functional disability is of particular concern. Due to the lack of a uniform obesity definition, there is marked variability in reported SO prevalence and inconsistent data on observed adverse health outcomes.Objectives: We compare SO prevalence and the associations of SO with physical function using sarcopenia according to current AWGS guidelines with different obesity measures. We recommend that the most optimal SO diagnostic formulation would be one that is most significantly associated with reduced physical function.Design: 542 healthy, community-dwelling Singaporeans were recruited (21-90 years old, 57.9% women). We assessed anthropometry, body composition, and questionnaire-based physical and cognitive factors, and estimated SO prevalence with obesity defined according to waist circumference (WC), percentage body fat (PBF), fat mass index (FMI) and fat mass/fat-free mass ratio (FM/FFM). Muscle function was compared among phenotypes and obesity definitions using ANOVA. Differences across obesity measures were further ascertained using multiple linear regressions to determine their associations with the Short Physical Performance Battery (SPPB).Results: Overall prevalence of SO was 7.6% (WC-based), 5.1% (PBF-based), 2.7% (FMI-based), and 1.5% (FM/FFM-based). The SO phenotype consistently performed poorer than the obese group (pppConclusions: Our findings suggest FMI as the most preferred measure for obesity and support its use as a diagnostic criteria for sarcopenic obesity.

Silicon solar cells are known to suffer from poor UV response because of high reflectance combined with recombination at the front side of the cell - including heavily doped emitter. While black silicon (b-Si) has proven to be excellent technology to overcome the reflectance losses, it has been challenging to integrate it to PERC cells with recombination-free emitter without compromising the optical properties. Here we show that no such tradeoffs are needed when using boron emitter with proper surface passivation. We demonstrate a b-Si emitter that has saturation current as low as 33 fA/cm2 resulting close to 100% EQE even down to 300 nm. This result should be interesting for the PV industry looking for further improvements in their current products.

Alkali solutions are not suitable for texturing multi-crystalline silicon (mc-Si) wafer due to the anisotropic etching. In this study, a two-step alkali-etch process is developed to form a flat surface on the wafer, which can be quickly and nearly isotropically etched by immersion in a sodium hydroxide solution, followed by a sodium hydroxide-sodium hypochlorite solution. The etching process leads to the formation of homogenous nanostructure, thereby improving the cell's repeatability and performance by simultaneously increasing its short-circuit current and open-circuit voltage.

Metal-assisted chemical etching (MACE) enables efficient texturing of diamond-wire sawn multicrystalline silicon (mc-Si) wafers. However, the excellent optics are often sacrificed by polishing the surface to achieve better surface passivation with chemical-vapor-deposited (CVD) silicon nitride (SiNx). In this work, we show that a polishing step is not required when CVD SiNx is replaced with atomic-layer-deposited (ALD) aluminum oxide (Al2O3). Indeed, while polishing increases reflectance, it has in general only very modest effect on surface recombination velocity of ALD-passivated b-Si. Furthermore, since ALD Al2O3 is compatible with various surface morphologies due to its excellent conformality, the MACE parameters can be more freely adjusted. First, the concentration of silver nitrate (AgNO3) in AgNO3/H2O solution that is used to deposit Ag nanoparticles is shown to affect the final b-Si morphology. Instead of needle-shaped b-Si produced by 5 mmol/L AgNO3 concentration, two orders of magnitude lower AgNO3 concentration produces porous structures, which are more challenging to passivate. Additionally, we demonstrate that a separate Ag nanoparticle removal step in nitric acid (HNO3) is not a prerequisite for high carrier lifetime. Instead, Ag nanoparticles present during polishing in a HF/HNO3/H2O solution affect the final b-Si morphology by accelerating the etching of Si. The results demonstrate that no trade-offs are necessary between optical and electrical properties of MACE b-Si when using ALD.

International audience; MACE nano-texture process applicable for both single-and multi-crystalline diamond-wire sawn Si solar cells. ABSTRACT The photovoltaic (PV) industry requires efficient cutting of large single and multi-crystalline (sc-and mc-) silicon (Si) wafers. Historically multi-wire slurry sawing (MWSS) dominated, but the higher productivity of diamond-wire-sawing (DWS) holds promise for decreasing PV costs in the future. While surface texturing of DWS wafers is more complicated than of MWSS wafers, especially in mc-Si wafers, nanotexturing has been shown to overcome this challenge. While the benefit of nanotexturing is thus clearer in mc-Si, a universal nano-texture process that also works on sc-Si would simplify and reduce the investments costs of PV production-lines. In this paper, such a nano-texture process is developed using a metal-assisted chemical etch (MACE) technique. Step-by-step characterization of surface structure and reflectance of the MACE process is used after: 1) wafering, 2) standard acidic texturing etch, 3) silver nanoparticles deposition, and 4) MACE nanotexturing for both sc and mc-Si. The results show that the same MACE process works effectively for both sc-Si and mc-Si wafers. Finally, the nano-textured wafers are processed into PV cells in an industrial process line with conversion efficiencies of 19.4 % and 18.7%, for sc-Si and mc-Si solar cells, respectively.

Granatum carbon (GC) as electrode materials for supercapacitors is prepared via the chemical activation with different activating agent such as ZnC2 and KOH with an intention to improve the surface area and their electrochemical performance. The structure and electrochemical properties of GC materials are characterized with N2 adsorption/desorption measurements, scanning electron microscope (SEM), cyclic voltammetry (CV), galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy (EIS). The obtained results show that the specific surface area of the granatum-based activated carbons increased obviously from 573 m2 x g(-1) to 1341 m2 x g(-1) by ZnC2 activation and to 930 m2 x g(-1) by KOH treatment. Furthermore, GCZ also delivers specific capacitance of 195.1 Fx g(-1) at the current density of 0.1 A x g(-1) in 30 wt.% KOH aqueous electrolyte and low capacitance loss of 28.5% when the current density increased by 10 times.

Process intensification through membrane pervaporation (PV) integrated with a fixed-bed reactor could be successfully applied to the esterification of oleic acid and ethanol, which is a crucial step in the biodiesel synthesis using waste oil and grease as resource. The properties of the NaA zeolite membrane such as structure, formulation and separation were investigated by scanning electronic microscopy–energy dispersive spectrometry (SEM–EDS), X-ray diffractometry (XRD) and PV dehydration. Results showed that the NaA zeolite membrane had good separating property for removing water from the organics mixture. The operating conditions were optimized as the ethanol to oleic acid molar ratio of 15:1, feedstock flow rate of 1.0 ml/min, reaction temperature of 80.0 °C and catalyst bed height of 132 mm. The final conversion of oleic acid increased from 84.23% to 87.18% by PV using the NaA zeolite membrane at 24.0 h of operation. The membrane showed good PV performance after used for eight successive runs in the PV-assisted esterification. The resin exhibited a much high catalytic activity and operation stability after used for 100 h in the consecutive single pass fixed-bed esterification.

Near-infrared (NIR) sensors find numerous applications within various industry fields, including optical communications and medical diagnostics. However, the state-of-the-art NIR sensors made of germanium (Ge) suffer from rather poor response, largely due to high reflection from the illuminated device surface. We demonstrate here a method to increase the sensitivity of Ge sensors by implementing nanostructures to the wafer surfaces. The absorbance of nanostructured Ge wafers is measured to be >99 % in the whole UV-VIS-NIR spectrum up to 1600 nm wavelength, which is a significant improvement to bare Ge wafers that reach absorption of only 63 % in maximum. The process is shown to be capable of producing uniform nanostructures covering full 100-mm-diameter substrates as well as wafers with etch mask openings of different sizes and shapes, which demonstrates its applicability to CMOS sensor manufacturing. The results imply that nanostructured Ge has potential to revolutionize the sensitivity of Ge-based sensors., Comment: Article published in Advanced Optical Materials. Complete citation details and link to the article published in the journal were added

Yawning is an important indicator of drivers’ drowsiness or fatigue. Techniques for automatic detection of driver’s yawning have been developed for use as a component of driver fatigue monitoring system. However, detecting driver’s yawning event accurately in real-time is still a challenging task, in particular in applications such as driver fatigue detection, illumination conditions vary in a broad range, driver facial features vary in size, shape, texture and degrees of distortion. In this paper, we present a deep neural network model built using transfer learning and sequential learning from yawning video clips as well as augmented images for yawning detection. As a result, unlike many other methods that follow a sequence of processes such as face ROI detection, eye/nose/mouth positioning and mouth open/close determination, the proposed yawning detection system detect yawning events directly from video images without requiring any facial part positions. The system is robust to variations in object scales, positions and subject view angles. The system has been evaluated on publicly available yawning data sets, YawDD and NTHU-DDD, as well as a data set containing challenging yawning videos. The experimental results show that the proposed yawning detection system has the capability of detecting yawning events in high precision even when face turns away from camera up to 70 degrees, while exhibiting capability of being scale- and spatial-invariant. In addition, the model demonstrates the capability of discriminating yawning events very well from the actions involving mouth opening-closing motions such as talking and laughing.

Tightly coupled LTE---Wi-Fi networks have emerged as a promising solution for improving capacity and coverage of wireless networks. Different architectures which realize this integration include LTE---Wi-Fi radio level interworking with IPSec tunnel (LWIP) and LTE---Wi-Fi Aggregation (LWA). In this paper, we firstly have described the structure of LWIP and stated its specific implement process. Then we have designed and implemented three different scenes to compare the performance differences between LWIP and LTE/WLAN. Simulation results demonstrate that the performances of LWIP are better than separate LTE and WLAN.