An analytical approach for unsupervised learning rate estimation using rectified linear units.

Unsupervised learning based on restricted Boltzmann machine or autoencoders has become an important research domain in the area of neural networks. In this paper mathematical expressions to adaptive learning step calculation for RBM with ReLU transfer function are proposed. As a result, we can automatically estimate the step size that minimizes the loss function of the neural network and correspondingly update the learning step in every iteration. We give a theoretical justification for the proposed adaptive learning rate approach, which is based on the steepest descent method. The proposed technique for adaptive learning rate estimation is compared with the existing constant step and Adam methods in terms of generalization ability and loss function. We demonstrate that the proposed approach provides better performance.

Study on high-precision three-dimensional reconstruction of pulmonary lesions and surrounding blood vessels based on CT images.

The adoption of computerized tomography (CT) technology has significantly elevated the role of pulmonary CT imaging in diagnosing and treating pulmonary diseases. However, challenges persist due to the complex relationship between lesions within pulmonary tissue and the surrounding blood vessels. These challenges involve achieving precise three-dimensional reconstruction while maintaining accurate relative positioning of these elements. To effectively address this issue, this study employs a semi-automatic precise labeling process for the target region. This procedure ensures a high level of consistency in the relative positions of lesions and the surrounding blood vessels. Additionally, a morphological gradient interpolation algorithm, combined with Gaussian filtering, is applied to facilitate high-precision three-dimensional reconstruction of both lesions and blood vessels. Furthermore, this technique enables post-reconstruction slicing at any layer, facilitating intuitive exploration of the correlation between blood vessels and lesion layers. Moreover, the study utilizes physiological knowledge to simulate real-world blood vessel intersections, determining the range of blood vessel branch angles and achieving seamless continuity at internal blood vessel branch points. The experimental results achieved a satisfactory reconstruction with an average Hausdorff distance of 1.5 mm and an average Dice coefficient of 92%, obtained by comparing the reconstructed shape with the original shape,the approach also achieves a high level of accuracy in three-dimensional reconstruction and visualization. In conclusion, this study is a valuable source of technical support for the diagnosis and treatment of pulmonary diseases and holds promising potential for widespread adoption in clinical practice.

Revisiting ultrasmall phosphine-stabilized rhodium-doped gold clusters AunRh (n = 5, 6, 7, 8): geometric, electronic, and vibrational properties.

Incorporation of other transition metals in Au nanoclusters has been thriving recently due to its effect on their electronic and photophysical properties. Here, the ultrasmall phosphine-stabilized Rh-doped gold clusters AunRh (n = 5, 6, 7, 8), with metal core structures represented as fragments of a rhodium-centered icosahedron, are considered. The geometric and electronic properties of these nanoclusters are revisited and analyzed using density functional theory (DFT). Moreover, infrared spectra are simulated to identify the effects of Rh doping on the clusters through vibrational properties. Peaks are assigned to breathing-like normal modes for all AuRh clusters except for Au8Rh, likely due to the presence of bound Cl ligands. Unlike their pure gold core counterparts, the % motions of both Au and Rh atoms are lower in the mixed metal clusters, suggesting more restrained metal cores by rhodium, which could result in other novel physical and chemical properties not hitherto discovered.

In Situ Incorporation of Atomically Precise Au Nanoclusters within Zeolites for Ambient Temperature CO Oxidation.

Preserving ultrasmall sizes of metal particles is a key challenge in the study of heterogeneous metal-based catalysis. Confining the ultrasmall metal clusters in a well-defined crystalline porous zeolite has emerged as a promising approach to stabilize these metal species. Successful encapsulation can be achieved by the addition of ligated metal complexes to zeolite synthesis gel before hydrothermal synthesis. However, controlling the metal particle size during post-reduction treatment remains a major challenge in this approach. Herein, an in situ incorporation strategy of pre-made atomically precise gold clusters within Na-LTA zeolite was established for the first time. With the assistance of mercaptosilane ligands, the gold clusters were successfully incorporated within the Na-LTA without premature precipitation and metal aggregation during the synthesis. We have demonstrated that the confinement of gold clusters within the zeolite framework offers high stability against sintering, leading to superior CO oxidation catalytic performance (up to 12 h at 30 °C, with a space velocity of 3000 mL g-1 h-1).

Degradation of sulfamethoxazole in water by AgNbO3 photocatalyst mediated by persulfate.

In this paper, silver niobate (AgNbO3) material was synthesized by a solid-state reaction. AgNbO3 was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS), and Brunauer-Emmett-Teller (BET) measurement. The photocatalytic activity of AgNbO3 was investigated in degradation of sulfamethoxazole (SMX) under visible light, which is a widely used antibiotic with significant threats towards health and aquatic organisms. Persulfate (PS) oxidant was found to improve the efficiency of the proposed photocatalytic removal of SMX by AgNbO3. The different operational parameters in the AgNbO3/PS/Vis system were investigated. The best photocatalytic performance was achieved with 0.5 g L-1 AgNbO3, 1.0 mM PS, and pH = 5.0 as the optimal conditions, achieving 98% of SMX degradation after 8 h of visible-light irradiation. Scavenger and electron spin resonance (ESR) experiments were carried out to identify the major reactive species in the SMX degradation and to propose the photocatalytic mechanism by the AgNbO3/PS/Vis system. The photodecomposition was found to be majorly caused by holes and ˙O2 - species, with ˙OH and SO4˙- radicals contributing to improve the photocatalytic process. The AgNbO3 catalyst was stable and reusable with efficient photocatalytic activity in three successive recycling experiments and its XRD patterns remained virtually unchanged. The reported process of PS activation by the AgNbO3 photocatalyst is promising for visible-light application in remediation of antibiotic-contaminated water.

Graphene Bridge for Photocatalytic Hydrogen Evolution with Gold Nanocluster Co-Catalysts.

Herein, the UV light photocatalytic activity of an Au101NC-AlSrTiO3-rGO nanocomposite comprising 1 wt% rGO, 0.05 wt% Au101(PPh3)21Cl5 (Au101NC), and AlSrTiO3 evaluated for H2 production. The synthesis of Au101NC-AlSrTiO3-rGO nanocomposite followed two distinct routes: (1) Au101NC was first mixed with AlSrTiO3 followed by the addition of rGO (Au101NC-AlSrTiO3:rGO) and (2) Au101NC was first mixed with rGO followed by the addition of AlSrTiO3 (Au101NC-rGO:AlSrTiO3). Both prepared samples were annealed in air at 210 °C for 15 min. Inductively coupled plasma mass spectrometry and high-resolution scanning transmission electron microscopy showed that the Au101NC adhered almost exclusively to the rGO in the nanocomposite and maintained a size less than 2 nm. Under UV light irradiation, the Au101NC-AlSrTiO3:rGO nanocomposite produced H2 at a rate 12 times greater than Au101NC-AlSrTiO3 and 64 times greater than AlSrTiO3. The enhanced photocatalytic activity is attributed to the small particle size and high loading of Au101NC, which is achieved by non-covalent binding to rGO. These results show that significant improvements can be made to AlSrTiO3-based photocatalysts that use cluster co-catalysts by the addition of rGO as an electron mediator to achieve high cluster loading and limited agglomeration of the clusters.

Emergent electronic properties in Co-deposited superatomic clusters.

We report an intercluster compound based on co-deposition of the Au cluster [Au9(PPh3)8](NO3)3 and the fulleride KC60(THF). Electronic properties characteristic for a charge interaction between superatoms emerge within the solid state material [Au9(PPh3)8](NO3)3-x(C60)x, as confirmed by UV-VIS and Raman spectroscopy and I-V measurements. These emergent properties are related to the superatomic electronic states of the initial clusters. The material is characterized by Fourier-transform infrared spectroscopy, x-ray diffraction, Raman spectroscopy, and electrical measurements. Structural optimization and ab initio band structure calculations are performed with density functional theory to interpret the nature of the electronic states in the material; Bader charge calculations assign effective oxidation states in support of the superatomic model of cluster interactions.

Photocatalytic Degradation of Ethiofencarb by a Visible Light-Driven SnIn4S8 Photocatalyst.

This work reports the preparation and detailed characterization of stannum indium sulfide (SnIn4S8) semiconductor photocatalyst for degradation of ethiofencarb (toxic insecticide) under visible-light irradiation. The as-prepared SnIn4S8 showed catalytic efficiency of 98% in 24 h under optimal operating conditions (pH = 3, catalyst dosage of 0.5 g L-1). The photodegradation reaction followed pseudo-first-order kinetics. The major intermediates have been identified using gas chromatography/mass spectrometry. •O2- and •OH radicals appeared to be the primary active species in the degradation process as revealed by scavenger and electronic spin resonance studies, while photogenerated holes had a secondary role in this process. A plausible mechanism involving two routes was proposed for ethiofencarb degradation by SnIn4S8 after identifying the major intermediate species: oxidative cleavage of the CH2-S and the amide bonds of the carbamate moiety. Lastly, SnIn4S8 was found to be efficient, stable, and reusable in treating real water samples in three successive photodegradation experiments. This study demonstrates the prospect of SnIn4S8 photocatalysis in treatment of natural and contaminated water from extremely toxic organic carbamates as ethiofencarb.

Size-activity threshold of titanium dioxide-supported Cu cluster in CO oxidation.

Development of non-noble metal cluster catalysts, aiming at concurrently high activity and stability, for emission control systems has been challenging because of sintering and overcoating of clusters on the support. In this work, we reported the role of well-dispersed copper nanoclusters supported on TiO2 in CO oxidation under industrially relevant operating conditions. The catalyst containing 0.15 wt% Cu on TiO2 (0.15 CT) exhibited a high dispersion (59.1%), a large specific surface area (381 m2/gCu), a small particle size (1.77 nm), and abundant active sites (75.8% Cu2O). The CO oxidation activity measured by the turnover frequency (TOF) was found to be enhanced from 0.60 × 10-3 to 3.22 × 10-3 molCO·molCu-1·s-1 as the copper loading decreased from 5 to 0.15 wt%. A CO conversion of approximately 60% was still observed in the supported cluster catalyst with a Cu loading of 5 wt% at 240 °C. No deactivation was observed for catalysts with low copper loading (0.15 and 0.30 CT) after 8 h of time-on-stream, which compares favorably with less stable Au cluster-based catalysts reported in the literature. In contrast, catalysts with high copper loading (0.75 and 5 CT) showed deactivation over time, which was ascribed to the increase in copper particle size due to metal cluster agglomeration. This study elucidated the size-activity threshold of TiO2-supported Cu cluster catalysts. It also demonstrated the potential of the supported Cu cluster catalyst at a typical temperature range of diesel engines at light-load. The supported Cu cluster catalyst could be a promising alternative to noble metal cluster catalysts for emission control systems.

Au101-rGO nanocomposite: immobilization of phosphine-protected gold nanoclusters on reduced graphene oxide without aggregation.

Graphene supported transition metal clusters are of great interest for potential applications, such as catalysis, due to their unique properties. In this work, a simple approach to deposit Au101(PPh3)21Cl5 (Au101NC) on reduced graphene oxide (rGO) via an ex situ method is presented. Reduction of graphene oxide at native pH (pH ≈ 2) to rGO was performed under aqueous hydrothermal conditions. Decoration of rGO sheets with controlled content of 5 wt% Au was accomplished using only pre-synthesised Au101NC and rGO as precursors and methanol as solvent. High resolution scanning transmission electron microscopy indicated that the cluster size did not change upon deposition with an average diameter of 1.4 ± 0.4 nm. It was determined that the rGO reduction method was crucial to avoid agglomeration, with rGO reduced at pH ≈ 11 resulting in agglomeration. X-ray photoelectron spectroscopy was used to confirm the deposition of Au101NCs and show the presence of triphenyl phosphine ligands, which together with attenuated total reflectance Fourier transform infrared spectroscopy, advocates that the deposition of Au101NCs onto the surface of rGO was facilitated via non-covalent interactions with the phenyl groups of the ligands. Inductively coupled plasma mass spectrometry and thermogravimetric analysis were used to determine the gold loading and both agree with a gold loading of ca. 4.8-5 wt%. The presented simple and mild strategy demonstrates that good compatibility between size-specific phosphine protected gold clusters and rGO can prevent aggregation of the metal clusters. This work contributes towards producing an agglomeration-free synthesis of size-specific ligated gold clusters on rGO that could have wide range of applications.

Oxygen-deficient bismuth molybdate nanocatalysts: Synergistic effects in boosting photocatalytic oxidative coupling of benzylamine and mechanistic insight.

Herein, bismuth molybdate (Bi2MoO6) nanocatalysts containing oxygen vacancies (OVs) are found to considerably promote the photocatalytic performance toward oxidative coupling of benzylamine to N-benzylidenebenzylamine under visible light irradiation. The structure-activity relationship for this interesting catalyst is revealed for the first time. The oxygen-deficient Bi2MoO6 nanoplatelets (BMO-NPs) are synthesized using ethylene glycol-ethanol solvent mixture as a reaction medium in solvothermal method. A comparison with hydrothermally prepared Bi2MoO6 square-like sheets (BMO-SHs) suggests that the nanoplatelets are much smaller in size and contain higher amount of OVs. Benzylamine conversion over the BMO-NPs is ca. 4.0 times higher than that over the BMO-SHs and ca. 3.8 and ca. 34.6 times higher than that over the commercial benchmark TiO2 P25 and BiVO4 catalysts, respectively. The BMO-NPs achieve more than 80% product yield within 2 h of irradiation regardless of substituents of benzylamine derivatives. The enhanced activity of BMO-NPs is due to synergistic roles of high surface-to-volume ratio and OVs, providing enlarged active area, extended light absorption range and improved charge separation and transfer efficiency as evidenced from UV-vis DRS, BET surface area, photocurrent response, electrochemical impedance spectroscopy, and time-resolved fluorescence decay measurements. EPR-trapping and radical scavenging experiments indicate O2- as a main active species rather than 1O2 and a plausible imine formation mechanism via O2--assisted charge transfer is proposed accordingly. The work offers an alternative facile preparation method to design efficient semiconductor photocatalysts and for the first time reveals a possible benzylamine coupling mechanism over the oxygen-deficient Bi2MoO6 nanocatalyst.

Recent applications of click chemistry for the functionalization of gold nanoparticles and their conversion to glyco-gold nanoparticles.

Glycoscience, despite its myriad of challenges, promises to unravel the causes of, potential new detection methods for, and novel therapeutic strategies against, many disease states. In the last two decades, glyco-gold nanoparticles have emerged as one of several potential new tools for glycoscientists. Glyco-gold nanoparticles consist of the unique structural combination of a gold nanoparticle core and an outer-shell comprising multivalent presentation of carbohydrates. The combination of the distinctive physicochemical properties of the gold core and the biological function/activity of the carbohydrates makes glyco-gold nanoparticles a valuable tool in glycoscience. In this review we present recent advances made in the use of one type of click chemistry, namely the azide-alkyne Huisgen cycloaddition, for the functionalization of gold nanoparticles and their conversion to glyco-gold nanoparticles.

Pharmacological analysis of the transmembrane action potential configuration in myoepithelial cells of the spontaneously beating heart of the ascidian Styela rustica in vitro.

The mechanisms of action potential (AP) generation in the myoepithelial cells of the tunicate heart are not yet well understood. Here, an attempt was made to elucidate these mechanisms by analyzing the effects of specific blockers of K+, Na+ and Ca2+ currents on the configuration of transmembrane APs and their frequency in the spontaneously beating ascidian heart. In addition, an immunocytochemical analysis of heart myoepithelial cells was performed. Staining with anti-FMRF-amide and anti-tubulin antibodies did not reveal any nerve elements within the heart tube. Treatment with 1 mmol l-1 TEA (IK blocker) resulted in depolarization of heart cell sarcolemma by 10 mV, and inhibition of APs generation was recorded after 3 min of exposure. Prior to this moment, the frequency of AP generation in a burst decreased from 16-18 to 2 beats min-1 owing to prolongation of the diastole. After application of ivabradine (3 or 10 µmol l-1), the spontaneous APs generation frequency decreased by 24%. Based on these results and published data, it is concluded that the key role in the automaticity of the ascidian heart is played by the outward K+ currents, Na+ currents, activated hyperpolarization current If and a current of unknown nature IX.

Apparatus for the investigation of high-temperature, high-pressure gas-phase heterogeneous catalytic and photo-catalytic materials.

A high-temperature, high-pressure, pulsed-gas sampling and detection system has been developed for testing new catalytic and photocatalytic materials for the production of solar fuels. The reactor is fitted with a sapphire window to allow the irradiation of photocatalytic samples from a lamp or solar simulator light source. The reactor has a volume of only 3.80 ml allowing for the investigation of very small quantities of a catalytic material, down to 1 mg. The stainless steel construction allows the cell to be heated to 350 °C and can withstand pressures up to 27 bar, limited only by the sapphire window. High-pressure sampling is made possible by a computer controlled pulsed valve that delivers precise gas flow, enabling catalytic reactions to be monitored across a wide range of pressures. A residual gas analyser mass spectrometer forms a part of the detection system, which is able to provide a rapid, real-time analysis of the gas composition within the photocatalytic reaction chamber. This apparatus is ideal for investigating a number of industrially relevant reactions including photocatalytic water splitting and CO2 reduction. Initial catalytic results using Pt-doped and Ru nanoparticle-doped TiO2 as benchmark experiments are presented.

Atomically resolved structure of ligand-protected Au9 clusters on TiO2 nanosheets using aberration-corrected STEM.

Triphenylphosphine ligand-protected Au9 clusters deposited onto titania nanosheets show three different atomic configurations as observed by scanning transmission electron microscopy. The configurations observed are a 3-dimensional structure, corresponding to the previously proposed Au9 core of the clusters, and two pseudo-2-dimensional (pseudo-2D) structures, newly found by this work. With the help of density functional theory (DFT) calculations, the observed pseudo-2D structures are attributed to the low energy, de-ligated structures formed through interaction with the substrate. The combination of scanning transmission electron microscopy with DFT calculations thus allows identifying whether or not the deposited Au9 clusters have been de-ligated in the deposition process.

Engineered silver nanoparticles are sensed at the plasma membrane and dramatically modify the physiology of Arabidopsis thaliana plants.

Silver nanoparticles (Ag NPs) are the world's most important nanomaterial and nanotoxicant. The aim of this study was to determine the early stages of interactions between Ag NPs and plant cells, and to investigate their physiological roles. We have shown that the addition of Ag NPs to cultivation medium, at levels above 300 mg L(-1) , inhibited Arabidopsis thaliana root elongation and leaf expansion. This also resulted in decreased photosynthetic efficiency and the extreme accumulation of Ag in tissues. Acute application of Ag NPs induced a transient elevation of [Ca(2+) ]cyt and the accumulation of reactive oxygen species (ROS; partially generated by NADPH oxidase). Whole-cell patch-clamp measurements on root cell protoplasts demonstrated that Ag NPs slightly inhibited plasma membrane K(+) efflux and Ca(2+) influx currents, or caused membrane breakdown; however, in excised outside-out patches, Ag NPs activated Gd(3+) -sensitive Ca(2+) influx channels with unitary conductance of approximately 56 pS. Bulk particles did not modify the plasma membrane currents. Tests with electron paramagnetic resonance spectroscopy showed that Ag NPs were not able to catalyse hydroxyl radical generation, but that they directly oxidized the major plant antioxidant, l-ascorbic acid. Overall, the data presented shed light on mechanisms of the impact of nanosilver on plant cells, and show that these include the induction of classical stress signalling reactions (mediated by [Ca(2+) ]cyt and ROS) and a specific effect on the plasma membrane conductance and the reduced ascorbate.

Effects of 4-aminopyridine on action potentials generation in mouse sinoauricular node strips.

The physiological role of Ito has yet to be clarified. The goal of this study is to investigate the possible contribution of the transient outward current (Ito) on the generation of transmembrane action potentials (APs) and the sensitivity of mouse sinoauricular node (SAN) cells to a 4-aminopyridine (4AP) as Ito blocker. The electrophysiological identification of cells was performed in the sinoauricular node artery area (nstrips = 38) of the subendocardial surface using microelectrode technique. In this study, for the first time, it was observed that dependence duration of action potential at the level of 20% repolarization (APD20) level under a 4AP concentration in the pacemaker SAN and auricular cells corresponds to a curve predicted by Hill's equation. APD20 raised by 70% and spike duration of AP increased by 15-25%, when 4AP concentration was increased from 0.1 to 5.0 mmol/L. Auricular cells were found to be more sensitive to 4AP than true pacemaker cells. This was accompanied by a decrease in the upstroke velocity as compared to the control. Our data and previous findings in the literature lead us to hypothesize that the 4AP-sensitive current participates in the repolarization formation of pacemaker and auricular type cells. Thus, study concerning the inhibitory effects of lidocaine and TTX on APD20 can explain the phenomenon of the decrease in upstroke velocity, which, for the first time, was observed after exposure to 4AP. Duration of AP at the level of 20% repolarization (APD20) under a 4-AP concentration 0.5 mmol/L in the true pacemaker cells lengthen by 60-70% with a control.

Size-optimized galactose-capped gold nanoparticles for the colorimetric detection of heat-labile enterotoxin at nanomolar concentrations.

The development of a galactose-capped gold nanoparticle-based colorimetric sensor for the detection of the lectin heat-labile enterotoxin is reported. Heat-labile enterotoxin is one of the pathogenic agents responsible for the intestinal disease called 'traveller's diarrhoea'. By means of specific interaction between galactose moieties attached to the surface of gold nanoparticles and receptors on the B-subunit of heat-labile enterotoxin (LTB), the gold nanoparticles reported here act as an efficient colorimetric sensor, which can detect the toxin at nanomolar concentrations. The effect of gold nanoparticle size on the detection sensitivity was investigated in detail. Amongst the various sizes of gold nanoparticles studied (2, 7, 12, and 20 nm), the 12 nm sized gold nanoparticles were found to be the most efficient, with a minimum heat-labile enterotoxin detection concentration of 100 nM. The red to purple colour change of the gold nanoparticle solution occurred within two minutes, indicating rapid toxin sensing.

Gold Nanoparticles Decorated with Sialic Acid Terminated Bi-antennary N-Glycans for the Detection of Influenza Virus at Nanomolar Concentrations.

Invited for this month's cover picture is the group of Professor Antony Fairbanks and his collaborators at the University of Canterbury and University of Otago. The cover shows the isolation of complex bi-antennary oligosaccharides from hens' eggs and their conjugation to gold nanoparticles. Gold nanoparticles carrying these sugars can then bind to specific receptors (hemagglutinin) on the surface of the influenza virus, causing particle aggregation, which changes their spectroscopic properties. Upon aggregation, they undergo a red-shift in their surface plasmon resonance, as illustrated by the bound particles shining in the cover image. These changes in spectroscopic properties are the basis of a detection system capable of detecting viral hemagglutinin at nanomolar concentrations, as well as the virus itself. For more details, see the Full Paper on p. 708 ff.Read the full text of the article at 10.1002/open.201500109.

Gold Nanoparticles Decorated with Sialic Acid Terminated Bi-antennary N-Glycans for the Detection of Influenza Virus at Nanomolar Concentrations.

Gold nanoparticles decorated with full-length sialic acid terminated complex bi-antennary N-glycans, synthesized with glycans isolated from egg yolk, were used as a sensor for the detection of both recombinant hemagglutinin (HA) and whole influenza A virus particles of the H1N1 subtype. Nanoparticle aggregation was induced by interaction between the sialic acid termini of the glycans attached to gold and the multivalent sialic acid binding sites of HA. Both dynamic light scattering (DLS) and UV/Vis spectroscopy demonstrated the efficiency of the sensor, which could detect viral HA at nanomolar concentrations and revealed a linear relationship between the extent of nanoparticle aggregation and the concentration of HA. UV/Vis studies also showed that these nanoparticles can selectively detect an influenza A virus strain that preferentially binds sialic acid terminated glycans with α(2→6) linkages over a strain that prefers glycans with terminal α(2→3)-linked sialic acids.