Simple Source Research Articles

Novel MCP-Windowed EUV Light Source and Its Mass Spectrometric Application for Detecting Chlorinated Methanes.

Various vacuum ultraviolet (VUV) lamps are simple and convenient VUV light sources for mass spectrometry and other research fields. However, the strong absorption of high-energy photons by window materials limits the application of an extreme ultraviolet (EUV) light. In this study, a novel high-flux EUV light source is developed using a microchannel plate (MCP) window to transmit 73.6 nm (16.9 eV) EUV light generated via the radio frequency (RF) inductive discharge of neon. The MCP used is a 0.5 mm thick glass plate with a regular array of microtubes (12 μm i.d.). The photon fluxes of the EUV light source with the MCP window (12 mm i.d.) and an aperture (1.8 mm i.d.) are ∼1.31 × 1014 and ∼9.80 × 1012 photons s-1, respectively, while their corresponding leakage flow rates of the discharge gas are 0.062 and 0.046 cm3 atom s-1, according to the contrast experiments. The transmission efficiency of the MCP to the EUV light is 30.2%, with a 1.2% deviation. An EUV photoionization time-of-flight mass spectrometer (EUV-PI-TOFMS) is built to validate the practicality of the MCP-windowed EUV light source further. The detection sensitivities in 30 s measurements for methyl chloride (CH3Cl), methylene chloride (CH2Cl2), trichloromethane (CHCl3), and carbon tetrachloride (CCl4) in synthetic air are 4366, 4120, 5854, and 4095 counts ppbv-1, respectively. The corresponding 3σ limits of detection (LODs) are 42, 34, 24, and 15 pptv. This study develops a new feasible method for efficiently utilizing high-energy EUV light, with many application prospects in scientific research.

Frequency conversion of a chirped Ti:sapphire laser pulse to 11.4 μm wavelength with SrMoO4 Raman shifter and LiGaS2 DFG crystal

The simple mid-IR laser source based on femtosecond Ti:Sapphire laser and successive frequency conversion of its stretched up to 50 ps pulses in SrMoO4 Raman-active crystal and LiGaS2 second order nonlinear crystal is demonstrated. Energy of the mid-IR pulse at 11.4 μm wavelength was up to 250 nJ that was four times higher than the previous results for the similar setup. The influence of pump pulse intensity on spectral and energetic parameters of laser pulses after SrMoO4 and LiGaS2 crystals were studied in details.

Engineering acetylation platform for the total biosynthesis of D-amino acids

Optically pure D-amino acids are key chemicals with various applications. Although the production of specific D-amino acids has been achieved by chemical synthesis or with in vitro enzyme catalysts, it is challenging to convert a simple carbon source into D-amino acids with high efficiency. Here, we design an artificial metabolic pathway by engineering bacteria to heterologously express racemase and N-acetyltransferase to produce N-acetyl-D-amino acids from L-amino acids. This new platform allows the cytotoxicity of D-amino acids to be avoided. The universal potential of this acetylation protection strategy for effectively synthesizing optically pure D-amino acids is demonstrated by testing sixteen amino acid targets. Furthermore, we combine pathway optimization and metabolic engineering in Escherichia coli and achieve practically useful efficiency with four specific examples, including N-acetyl-D-valine, N-acetyl-D-serine, N-acetyl-D-phenylalanine and N-acetyl-D-phenylglycine, with titers reaching 5.65 g/L, 5.25 g/L, 8.025 g/L and 130 mg/L, respectively. This work opens up opportunities for synthesizing D-amino acids directly from simple carbon sources, avoiding costly and unsustainable conventional approaches.

Simulation of Welding Residual Stresses in Large Structures – First Results of Thermal Analyses

AbstractSimulation of welding residual stresses and distortions has been applied mostly for small‐scale components, smaller than those applied in civil engineering structures, due to the high requirements in computational capacities. In the present study, work hypotheses, which can reduce the computational load of welding simulations for an accepted sacrifice in accuracy, are discussed. A series of thermal analyses is carried out, in order to check the validity of the proposed modelling approaches, which refer to the application of simple weld heat source models and hybrid shell‐solid element models. Application of local‐global models is also discussed. The present study aims to work as a first step towards the establishment of an engineering approach for the simulation of welds in civil engineering structures with sufficient accuracy and reduced requirements for computational capacity.

Laboratory Characterisation of a Commercial RGB CMOS Camera for Measuring Night Sky Brightness

The use of RGB cameras in photometric applications has grown over the last few decades in many fields such as industrial applications, light engineering and the analysis of the quality of the night sky. In this last field, they are often used in conjunction with a Sky Quality Meter (SQM), an instrument used for the measurement of night sky brightness (NSB), mainly when there is a significant amount of artificial light at night (ALAN). The performances of these two instruments are compared here. A simple source composed of nine narrowband LEDs in an integrating sphere was used to excite the two instruments and therefore measure the spectral responsivity of the SQM and of the three channels of the camera. The estimated uncertainties regarding spectral responsivity were less than 10%. A synthetic instrument approximating the SQM’s responsivity can be created using a combination of the R, G and B channels. The outputs of the two instruments were compared by measuring the spectral radiance of the night sky. An evaluation of the spectral mismatch between the two instruments completed the analysis of their spectral sensitivity. Finally, the measurements of real SQMs in four sites experiencing different levels of light pollution were compared with the values obtained by processing the recorded RGB images. Overall, the analysis shows that the two instruments have significantly different levels of spectral responsivity, and the alignment of their outputs requires the use of a correction which depends on the spectral distribution of the light coming from the sky. A synthetic SQM will always underestimate real SQM measures; an average correction factor was evaluated considering nine sky spectra under low and medium levels of light pollution; this was determined to be 1.11 and, on average, compensated for the gap. A linear correction was also supposed based on the correlation between the NSB levels measured by the two instruments; the mean squared error after the correction was 0.03 mag arcsec−2.

NA-GCAP: A New Full Moment Tensor Inversion Method Based on the Renewed GRTM and NA Method

Abstract Moment tensor inversion plays a crucial role in determining earthquake types, magnitude, and source geometry. Compared to polarity and amplitude methods, full-waveform approaches provide more comprehensive constraints on the complex full moment tensor (FMT). In this study, we propose a novel FMT inversion method named neighborhood algorithm-generalized cut-and-paste (NA-GCAP) method. Similar to the “cut-and-paste” method, our approach divides seismograms into Pnl and surface-wave segments. To enhance inversion efficiency, we employ the NA in conjunction with a newly developed strategy for efficient Green’s functions computation based on the renewed fast generalized reflection and transmission method (GRTM). Our method requires only a single forward computation and stores ten Green’s functions, significantly improving computational efficiency. We validate the robustness of our approach through synthetic tests using a velocity model perturbed by 5% relative to the input model. Furthermore, we apply the NA-GCAP method to the 2019 Changning earthquake sequence comprising 16 earthquakes, where twelve events exhibit double-couple (DC) components larger than 0.95, indicating a simple dislocation source, and four events display significant non-DC components. Our results align well with the previous studies and demonstrate the potential for widespread application to other earthquake sequences in the future.

Coupled size and temperature effects on intermittent plasticity of BCC micro-crystals

The intermittent plasticity of pure Mo microcrystals with diameters from 500 to 3500 nm was studied using micro-pillar compression methodology at temperatures ranging from 25 °C to 200 °C, in order to explore its dependence on external size and temperature. The technological background is the potential value of BCC metals in the manufacture of high-temperature components in modern fields requiring miniaturization, such as microelectronics. We analyzed plastic fluctuations in terms of wildness, avalanche size distribution, and burst peak velocity. This reveals coupled size and temperature effects on a mild-to-wild transition: the transition temperature decreases with decreasing sample diameter, while the transition diameter increases with rising temperature. In addition, strain-rate sensitivity tests were conducted, implying that mild plasticity is associated to screw dislocation motions controlled by thermally activated nucleation of kink-pairs, whereas wild plasticity is nearly athermal. This experimental observation is interpreted by a damping effect of the thermally activated motion of screw dislocations on the propagation of avalanches. From this, we propose a controlling parameter based on a simple dislocation source model, which unifies the coupled sample size and temperature effects on the mild-to-wild transition, and which could be of practical significance for microscale applications.

Capillary self-aspirating electrospray ionization (CSESI) for convenient and versatile mass spectrometry analysis

Electrospray ionization (ESI) is one of the most widely used ionization techniques, and its simplification can benefit many interested users. In this study, sample introduction by capillary action was studied and used to develop a simple ESI source called capillary self-aspirating electrospray ionization (CSESI). A conventional CSESI source requires only a common capillary of appropriate diameter in addition to the support of high voltage (HV). No pumps and sample loading is needed because the solution can spontaneously climb across the capillary by capillary action. With the proper modification of the glass capillary, the operation of CSESI can be further simplified and efficient. Specifically, cold plasma processing of the capillary creates a more hydrophilic surface that can facilitate sample introduction. Moreover, sputtering a thin platinum layer on the capillary tip makes the application of HV more convenient, and it also eliminates the influence of air bubbles in the capillary to ensure a sustained and stable electrospray. Overall, CSESI exhibits multiple desirable features such as simple structure, self-aspiration ability, low sample consumption, and inherent physical filtration capability. Apart from the routine ESI-MS analysis, it has also been applied in real-time monitoring of the oxidative dimerization of 8-methyl-1,2,3,4-tetrahydroquinoline, as well as direct analysis of muddy soil solutions without pretreatment.

Comparison of force and moment tensor estimations of subevents during the 2022 Hunga–Tonga submarine volcanic eruption

SUMMARYThe 2022 January 15 Hunga–Tonga submarine volcanic eruption was unprecedented in the modern era for its size, in terms of its plume height and atmospheric waves, including sound. Global seismic stations recorded maximal radiated energy during 30 min of the plume-forming phase of the eruption (04:00 to 04:30 UTC), with the largest subevents occurring over a 5-min interval starting at 04:15:17 UTC. Here, we consider two simple point-source models—force and moment tensor—and separately consider the single main subevent and the sequence of four subevents. Estimation of source models for the first subevent in the sequence is achieved with a complete search of model parameter space to find the global minimum of a waveform misfit function (body or surface waves). We performed 25 runs to explore the impact of depth, source model (force or moment tensor), wave type (body or surface), and component (vertical, radial, and transverse) on the waveform fits and estimated best-fitting source. Visualization of the misfit function reveals complex trade-offs among model parameters, highlighting the importance of characterizing uncertainties and parameter trade-offs. The four-subevent source model has up to 28 model parameters and requires an efficient search algorithm to find the best-fitting source. For this, we use the covariance matrix adaptation evolution strategy implemented on a high-performance computing cluster. The 10 four-subevent runs for each source model return sequences of subvertical downward forces and explosive-like moment tensors for each subevent. Our results show that these two simple source models provide comparable fits to regional and global seismic waveforms and that the source types for each subevent—either force direction or moment tensor source type on the eigenvalue lune—are similar enough to each other to consider that the subevents originate from the same process. Our estimation of the source mechanisms, sizes, and relative timing should benefit a physical interpretation of the eruption sequence.

Low-Frequency Noise Attenuation in a Closed Space Using Adaptive Directivity Control Sources of a Quadrupole Type

A novel method of active noise control using adaptive radiation sound sources is investigated. A finite element model of a modal enclosed sound field is excited harmonically, representing a noise field in the low-frequency range. The control sources are comprised of elementary dipole sources for which the driving signals are adjusted by an optimization method. Two set-up cases of the proposed compound sources are investigated. The coupling of the control sources with the modal sound field is discussed. The simulated performance of the proposed method is compared with that of a system with distributed simple sources and the results show the effectiveness of the sources with adaptive radiation for active noise control in small enclosures.

Recent Advances and Development in Visible‐Light‐Mediated Glycosylation: An Expanding Research Area in Glycochemistry

AbstractIn the last fifteen years, the development of visible‐light photocatalysis, metal/photoredox dual catalysis has become the forefront as a new paradigm in organic synthesis as well as in carbohydrate chemistry. It led to the discovery of unprecedented transformations and also the improvement of known reactions under mild conditions, employing simple household light sources and bench‐stable precursors, which meet the requirements of green chemistry and sustainable development in excellent yield and stereocontrol. In a general sense, the exploitation of photoredox catalysis hinges on the capability of photocatalyst or redox mediator to transform visible light into chemical energy via photo‐irradiated SET (single electron transfer), PET (photoinduced electron transfer), HAT (hydrogen atom transfer), and XAT (halogen atom transfer) to potentially unlock unique reaction pathways, thereby generating a diverse array of reactive intermediates. In view of reaction type, mechanism, and status, this review will systematically summarize the latest advances in visible‐light‐promoted photocatalytic glycosylation reactions, which are driven by single or dual photoredox catalysis and by the photoactivity of electron donor‐acceptor (EDA) complexes.

Synthesis of Multiple Emission Carbon Dots from Dihydroxybenzoic Acid via Decarboxylation Process.

Carbon dots (CDs), as a new zero-dimensional carbon-based nanomaterial with desirable optical properties, exhibit great potential for many application fields. However, the preparation technique of multiple emission CDs with high yield is difficult and complex. Therefore, exploring the large-scale and straightforward synthesis of multicolor CDs from a simple carbon source is necessary. In this work, the solvent-free method prepares a series of multicolor emission CDs from dihydroxybenzoic acid (DHBA). The maximum emission wavelengths are 408, 445, 553, 580, and 610 nm, respectively, covering the visible light region. The 2,4- and 2,6-CDs possess the longer emission wavelength caused by the 2,4-, and 2,6-DHBA easily undergo decarboxylation to form the larger sp2 domain graphitized structure. These CDs incorporated with g-C3N4 can significantly improve the photocatalytic water-splitting hydrogen production rate by extending the visible light absorption and enhancing the charge separation efficiency. The long-wavelength emission CDs can further enhance photocatalytic activity primarily by improving visible light absorption efficiency.

A novel layered double hydroxides oleogel lubricant: Inspired by conventional greases

Grease lubricants serve as a simple, effective and convenient source of lubrication for saving energy. However, the most applicable lithium greases meet contradictory pressures of high performance and low pricing demands because of the substantial development of the global electric vehicles industry and the ubiquity of lithium batteries. In order to alleviate the dependence on lithium resources and develop resource-widespread and economical lubricating grease, herein, a class of thickener and oleogel system based on organic acid intercalated layered double hydroxides (LDHs) inspired by traditional grease has been reported. LDHs materials can be regarded as a preassembled “salt-like” compound, comparable to the self-assembled traditional metal soap salt thickener. LDHs oleogels exhibit viscoelastic properties and tribological performance similar to those of lithium greases. This study presents ideas for future development through layered materials regarding as "salt-like" compounds as a replacement for traditional grease thickeners.

The Rotational Doppler Effect of Twisted Photons in Scattered Fields

AbstractAlong with broad applications of the linear Doppler effect, the rotational Doppler effect (RDE) of a structured light source carrying orbital angular momentum (OAM) has attracted significant attention for applications ranging from optical sensors to Doppler cooling. However, the high‐purity structured source's low energy efficiency and unknown optimal OAM parameters have significantly degraded the RDE's performance in previous work. Here, instead of utilizing an optical vortex source, the Doppler features are analyzed in scattered twisted photons carrying OAM with a common light source, and it is demonstrated that the RDE induced by a typical rotator can be extracted using a spiral phase spatial filter (SPSF) at the receiver. This model reveals that a rotating rough surface scatters abundant twisted photons carrying varied OAM values, and the OAM spectrum distribution is modulated by its angular coherence of spatial signature. Furthermore, common surfaces with different autocorrelation structures on received signals using the SPSF method are analyzed theoretically and experimentally. Such a scheme facilitates rotator detection with a generalized nonvortex simple source and dozen–fold improved efficiency with robustness against noncoaxial problems. These demonstrations open a path for studying and applying scattered twisted photons during light detection.

Towards a better understanding concerning carbon to nitrogen ratio and the carbon source in aerobic granular sludge

This study investigated the effects of the carbon-to-nitrogen (C/N) ratio on aerobic granular sludge (AGS) using two identical biological reactors (C/N = 5 and C/N = 10). After 84 days of operation, the reactors' organic substrate was switched from a simple synthetic carbon source (acetate and propionate) to a more complex carbon source (50% volatile fatty acids and 50% fermentable substrate). The C/N = 10 resulted in smaller, uniform granules (200 < Diameter(D)(μm) < 500) with improved settling characteristics (sludge volumetric index - SVI5 < 30 mL gTSS L−1). The nitrogen compounds in the influent influenced the protein/polysaccharide ratio (PN/PS), with higher PS content observed under C/N = 5 and lower PS content under C/N = 10. Both C/N ratios achieved high carbon removal rates (∼90%), but ammonia oxidation was lower under C/N = 5 (up to 45%) due to alkalinity deficiency. Insufficient alkalinity and higher nitrogen compounds in the influent negatively affected phosphorus removal by reducing the activity of phosphorus-accumulating organisms and promoting the growth of glycogen-accumulating organisms. The complexity of the organic substrate hindered microbial activities through intermediate products from glucose and amino acid metabolic pathways. EPS-producing denitrifying organisms (Thauera and Xanthomonas) were favored in C/N = 5, while at C/N = 10, organisms associated with granular biomass stability (Zoogloea and Flavobacterium) were selected. The addition of glucose in the effluent led to a significant increase in fermentative organisms (Aeromonadaceae). This study emphasizes the crucial role of the C/N ratio and organic substrate complexity in achieving optimal performance in AGS systems.

Quantum-dot light-chip micro-spectrometer.

Micro-spectrometers have great potential in various fields such as medicine, agriculture, and aerospace. In this work, a quantum-dot (QD) light-chip micro-spectrometer is proposed in which QDs emit different wavelengths of light that are combined with a spectral reconstruction (SR) algorithm. The QD array itself can play the roles of both the light source and the wavelength division structure. The spectra of samples can be obtained by using this simple light source with a detector and algorithm, and the spectral resolution reaches 9.7 nm in the wavelength range from 580 nm to 720 nm. The area of the QD light chip is 4 × 7.5 mm2, which is 20 times smaller than the halogen light sources of commercial spectrometers. It does not need a wavelength division structure and greatly reduces the volume of the spectrometer. Such a micro-spectrometer can be used for material identification: in a demonstration, three kinds of transparent samples, real and fake leaves, and real and fake blood were classified with an accuracy of 100%. These results indicate that the spectrometer based on a QD light chip has broad application prospects.

Engineering Escherichia coli BL21 (DE3) for high-yield production of germacrene A, a precursor of β-elemene via combinatorial metabolic engineering strategies.

β-elemene is one of the most commonly used antineoplastic drugs in cancer treatment. As a plant-derived natural chemical, biologically engineering microorganisms to producegermacrene A to be converted to β-elemene harbors great expectations since chemical synthesis and plant isolation methods come with their production deficiencies. In this study, we report the design of an Escherichia coli cell factory for the de novo production of germacrene A to be converted to β-elemene from a simple carbon source. A series of systematic approaches of engineering the isoprenoid and central carbon pathways, translational and protein engineering of the sesquiterpene synthase, and exporter engineering yielded high-efficient β-elemene production. Specifically, deleting competing pathways in the central carbon pathway ensured the availability of acetyl-coA, pyruvate, and glyceraldehyde-3-phosphate for the isoprenoid pathways. Adopting lycopene color as a high throughput screening method, an optimized NSY305N was obtained via error-prone polymerase chain reaction mutagenesis. Further overexpression of key pathway enzymes, exporter genes, and translational engineering produced 1161.09 mg/L of β-elemene in a shake flask. Finally, we detected the highest reported titer of 3.52 g/L of β-elemene and 2.13 g/L germacrene A produced by an E. coli cell factory in a 4-L fed-batch fermentation. The systematic engineering reported here generally applies to microbial production of a broader range of chemicals. This illustrates that rewiring E. coli central metabolism is viable for producing acetyl-coA-derived and pyruvate-derived molecules cost-effectively.

Estimation of inhomogeneous occupational exposure to the lens of the eyes and the extremities of radiation workers in a research accelerator facility.

We performed an experimental investigation on occupational exposure of the eye lens and the extremity of radiation workers engaged in handling of highly activated materials in a small research accelerator facility. Using a simplified physical phantom to simulate the relevant inhomogeneous radiation exposure situations, the personal dose equivalents obtained at the eye lens and the extremities of radiation workers handling heavily radioactive converters were measured together with the dose measured by personal dosemeters worn on their trunk. Results of mockup experiments and the Monte Carlo calculations suggest that the quantitative estimation of the eye lens doses can be estimated from the trunk dose, while the extremity doses vary considerably from the dose readings from the trunk, depending on the use of simple point-source or volume source geometry.

Simple and compact high-power continuous-wave deep ultraviolet source at 261 nm based on diode-pumped intra-cavity frequency doubled Pr:LiYF4 green laser.

We report the recent progress on diode-pumped high-power continuous-wave Pr:LiYF4 (YLF) green laser and deep ultraviolet (DUV) laser generation via intracavity frequency doubling. Using two InGaN blue diode lasers as pump source to form a double-end pumping geometry, in this work, we have demonstrated a green laser at 522 nm with a maximum output power of 3.42 W, which is believed to be the highest power ever achieved in all-solid-state Pr3+ lasers in this specific spectral region. Moreover, by intracavity frequency doubling of the achieved green laser, we have further obtained a DUV laser at about 261 nm with a maximum output power of 1.42 W, which is far higher than previous results. The watt-level 261-nm laser paves the way towards the realization of simple and compact DUV source for a variety of applications.

The role of soft photon injection and heating in 21 cm cosmology

ABSTRACT The ARCADE radio excess and EDGES measurement remain puzzling. A link between the two has been previously considered, however, in this work we highlight an important related effect that was not analysed in detail before. By performing cosmological thermalization calculations with soft photon injection using cosmotherm, we show that for the 21 cm signal generation, the interplay between enhanced radio spectral distortions and the associated heating can hide a significant radio excess before the reionization era. We illustrate this effect for a simple power-law soft photon source in decaying particle scenarios. Even if simplistic, the uncovered link between CMB spectral distortions and 21 cm cosmology should apply to a much broader range of scenarios. This could significantly affect the constraints derived from existing and future 21 cm observations on the evolution of the ambient radio background. In particular, scenarios that would be ruled out by existing data without heating could become viable solutions once the heating is accounted for in the modelling. Our calculations furthermore highlight the importance of global 21 cm observations reaching into the dark ages, where various scenarios can potentially be distinguished.