Changes In Emission Characteristics Research Articles

Tuning the Structures of Amide‐Imine Conjugates for Sequential Optical Recognition of Mo(VI) and AsO2− Ions

AbstractTwo amide‐imine conjugates where amide is synthesized by reacting hydrazine with 4‐hydroxybenzoic acid and subsequently condensed with 2‐hydroxy naphthalene‐1‐carbaldehyde (m1) and 2‐hydroxy benzaldehyde (m2), selectively detects Mo(VI) at nano molar level via change in emission characteristics. The interactions have been authenticated from single crystal X‐ray structures of resulting Mo(VI) complexes (Mo1 and Mo2). Further, Mo1 selectively interacts with AsO2− via formation of H‐bond that facilitates its detection through change of emission characteristics. The binding constant of Mo1 for AsO2− is 1.02×105 M−1/2. The TCSPC studies support the interaction of Mo1 with AsO2−. The probe‐analyte interaction has also been established by different spectroscopic techniques like 1H NMR, ESI‐MS, FTIR and Jobs experiment. Theoretical DFT studies justifies the reason behind the interaction and support experimental spectroscopic findings. Notably, the sequential fluorescence recognition of Mo(VI) and AsO2− by m1 have been explored to construct a logic gate.

Finer Particle Size Distribution and Potential Higher Toxicity of Elemental Carbon and Polycyclic Aromatic Hydrocarbons Emitted by Ships after Fuel Oil Quality Improvement.

Ship emissions are a significant source of air pollution, and the primary policy to control is fuel oil quality improvement. However, the impact of this policy on particle size distribution and composition characteristics remains unclear. Measurements were conducted on nine different vessels (ocean-going vessels, coastal cargo ships, and inland cargo ships) to determine the impact of fuel upgrading (S < 0.1% m/m marine gas oil (MGO) vs S < 0.5% m/m heavy fuel oil (HFO)) on elemental carbon (EC) and polycyclic aromatic hydrocarbons (PAHs) emitted by ships. (1) Fuel improvement significantly reduced EC and PAH emission, by 31 ± 25 and 45 ± 38%, respectively. However, particle size distributions showed a trend toward finer particles, with the peak size decreasing from DP = 0.38-0.60 μm (HFO) to DP = 0.15-0.25 μm (MGO), and the emission factor of DP < 100 nm increased. (2) Changes in emission characteristics led to an increase in the toxicity of ultrafine particulate matter. (3) Ship types and engine conditions affected the EC and PAH particle size distributions. Inland ships have a more concentrated particle size distribution. Higher loads result in higher emissions. (4) The composition and engine conditions of fuel oils jointly affected pollutant formation mechanisms. MGO and HFO exhibited opposite EC emissions when emitting the same level of PAHs.

Detection of a cyclotron line in the Be X-ray pulsar IGR J06074+2205

Context. IGR J0607.4+2205 is a transient Be X-ray binary discovered two decades ago. IGR J0607.4+2205 underwent an outburst in 2023 during which it was observed twice with NuSTAR. Aims. The main goal of this work is to model the broadband X-ray spectrum of IGR J0607.4+2205 during the outburst and to study the variations of the spectral and timing features at different intensities. Methods. We extracted the light curve and spectrum of the source from the two NuSTAR observations carried out during the recent outburst in the energy range of 3−78 keV. We used the epoch folding technique to find pulsation from the source and to study the changes in emission characteristics from the source with energy across an order of magnitude variation in source luminosity. Results. IGR J0607.4+2205 shows pulsations with a period of ∼347.6 s during both the observations, with a pulse fraction of ≥50%. The broadband spectrum of the source was modelled using a power-law continuum with a high-energy cutoff. During the first observation, a cyclotron absorption line at ∼51 keV was also present in the source with an optical depth of ∼1.3. However, no cyclotron line feature was detected in the second observation when the source was an order of magnitude fainter. Additionally, soft excess was detected in the second observation, which was modelled with a black body component emerging from close to the neutron star (NS). Conclusions. We report the first ever detection of a cyclotron line in the broadband spectrum of IGR J0607.4+2205 centred at 51 ± 1 keV. The magnetic field strength of the NS is estimated to be ∼4 × 1012 G from the centroid energy of the absorption line. A significant change is observed in the pulse profile with luminosity during the decay of the outburst, indicating an associated change in the beaming pattern.

Impact of electrical aging on x-ray image quality and dose rate with vertically aligned carbon nanotube based cold cathode electron beam (C-beam)

The adoption of vertically aligned carbon nanotubes (VACNTs) as electron emitters in x-ray generation has opened a new path for medical imaging technology advancement. With their outstanding electron emission capabilities, VACNTs provide a distinct advantage in miniaturizing and improving the performance of x-ray devices. This research focuses on the effect of electrical aging on x-ray imaging quality and the dose rate while using VACNTs as the electron source. The study includes a thorough examination of the electrical aging effects on VACNT-based x-ray systems, with an emphasis on changes in emission characteristics, beam stability, and the resulting variations in x-ray output. Experiment results show that electrical aging has a considerable impact on the performance of VACNT-based x-ray sources, with visible changes in electron emission parameters and subsequent consequences on x-ray imaging quality. Furthermore, the study investigates the relationship between electrical aging and the x-ray dose rate, providing vital insights into radiation exposure optimization in medical diagnostics.

Heterogeneous Variations on Historical and Future Trends of CO2 and Multiple Air Pollutants from the Cement Production Process in China: Emission Inventory, Spatial-Temporal Characteristics, and Scenario Projections.

Cement production is a major contributor to carbon dioxide (CO2) and multiple hazardous air pollutant (HAP) emissions, threatening climate mitigation and urban/regional air quality improvement. In this study, we established a comprehensive emission inventory by coupling the unit-based bottom-up and mass balance methods, revealing that emissions of most HAPs have been remarkably controlled. However, an increasing 6.0% of atmospheric mercury emissions, as well as 14.1 and 23.7% of fuel-related and process-related CO2 emission growth were witnessed unexpectedly. Industrial adjustment policies have imposed a great impact on the spatiotemporal changes in emission characteristics. Monthly emissions of CO2 and multiple HAPs decreased from December to February due to the "staggered peak production," especially in northern China after implementing the intensified action plan for air pollution control in winter. Upgrading environmental technologies and adjusting capacity structures are identified as dominant driving forces for reducing HAP emissions. Besides, energy intensity improvement can help offset some of the impact caused by the increase in clinker/cement production. Furthermore, scenario analysis results show that ultra-low emission and low-carbon technology transformation constitute the keys to achieve the synergic reduction of CO2 and multiple HAP emissions in the future.

Quantifying the emission potentials of fugitive dust sources in Nanjing, East China

Most cities in China have suffered severe atmospheric particulate matter (PM) pollution, with reduced visibility and worsened air quality. Fugitive dust that primarily originates from soils through the action of wind and anthropogenic activities is recognized to be a major source of urban PM. However, it remains challenging to quantify and parameterize fugitive dust emission from various sources due to a lack of observation data. In this study, a portable wind erosion system, PI-SWERL, was applied to characterize the dynamics and magnitude of PM10 and PM2.5 (particles smaller than 10 μm and 2.5 μm respectively) emissions from several possible sources in Nanjing, a typical large city in the Yangtze River Delta economic regions, East China. Results indicate that aerodynamic suspension and abrasion were two major physical mechanisms responsible for fugitive dust emissions, with varying characteristics by location. Changes of emission characteristics and quantities were primarily associated with differences in the supply of fine particles available for wind erosion, controlled by source-specific surface characteristics and anthropogenic disturbances. Construction sites and unpaved roads were identified as two significant sources, with total emission rates of 95.85 (56.97) and 57.22 (32.62) kg s−1 respectively for PM10 (PM2.5) at a friction velocity of 0.82 m s−1. These values were up to five times the amounts of PM emitted from arable lands and woodlands, and 1–2 orders of magnitude greater than those from paved roads, grasslands and bare lands. These data demonstrate the importance of construction sites and unpaved roads as local PM sources which might be significant in policy making for air quality management strategies and prioritization of emission control targets in an urban area.

Near-infrared spectroscopy (NIRS) as a tool to monitor exhaust air from poultry operations

Intensive poultry operation systems emit a considerable volume of inorganic and organic matter in the surrounding environment. Monitoring cleaning properties of exhaust air cleaning systems and to detect small but significant changes in emission characteristics during a fattening cycle is important for both emission and fattening process control. In the present study, we evaluated the potential of near-infrared spectroscopy (NIRS) combined with chemometric techniques as a monitoring tool of exhaust air from poultry operation systems. To generate a high-quality data set for evaluation, the exhaust air of two poultry houses was sampled by applying state-of-the-art filter sampling protocols. The two stables were identical except for one crucial difference, the presence or absence of an exhaust air cleaning system. In total, twenty-one exhaust air samples were collected at the two sites to monitor spectral differences caused by the cleaning device, and to follow changes in exhaust air characteristics during a fattening period. The total dust load was analyzed by gravimetric determination and included as a response variable in multivariate data analysis. The filter samples were directly measured with NIR spectroscopy. Principal component analysis (PCA), linear discriminant analysis (LDA), and factor analysis (FA) were effective in classifying the NIR exhaust air spectra according to fattening day and origin. The results indicate that the dust load and the composition of exhaust air (inorganic or organic matter) substantially influence the NIR spectral patterns. In conclusion, NIR spectroscopy as a tool is a promising and very rapid way to detect differences between exhaust air samples based on still not clearly defined circumstances triggered during a fattening period and the availability of an exhaust air cleaning system.

Emission characteristics of high-voltage plasma diode cathode for metal surface modification

Electron beam cathodes have been used in various fields such as microscopy, X-ray tubes, welding, and surface modification. Generally, cathodes use metals with lower work function, higher thermal resistance, lower poisoning effects of gases, etc. LaB6, tungsten, and tantalum have normally been used as cathode materials with special materials coated if required. This study investigated the high-voltage plasma diode cathode for surface modifications of metal products such as polishing, hardening and heat treatment. The most fascinating features of this cathode are the high voltage and current that can be obtained at a low vacuum of a few mTorr. However, it is difficult to control the emission current to attain a steady state and to obtain higher brightness than that achieved using a thermal cathode. We studied the emission characteristics in terms of cathode and anode design parameters such as anode distance and cathode shape. Additionally, changes of emission characteristics are discussed in terms of the type of gas, pressure parameter, etc. using the emission resistance, effective breakdown voltage, and brightness. Finally, by measuring the change in surface roughness using the emitted electron beams, we found that the surface roughness values before the process were Ra=0.8 µm and Rz=5.4 µm, whereas those after the process were Ra=0.25 µm and Rz=2.3 µm. The electron beam polishing technology is eco-friendly and can minimize the emission of many harmful materials that arise when existing mechanical or electrochemical polishing technologies are used.

Effect of Ag Capping Layer on the Emission Characteristics of Transparent Organic Light-emitting Devices with Ca/Ag Double-layer Cathodes

We have investigated the effects of an Ag capping layer on the emission characteristics of transparent organic light-emitting devices with Ca/Ag double-layer cathodes. The thickness of the Ag layer was varied from 10 to 30 nm, whereas the Ca was fixed to be a 10 nm in the Ca/Ag structure. The luminance and current efficiency on the cathode and anode sides are significantly dependent on the Ag thickness. For example, the current efficiency on the anode side increases from 8.4 to 11.7 cd/A, whereas, on the cathode side, it decreases from 3.2 to 0.2 cd/A as the Ag thickness increases from 10 to 30 nm. These changes in emission characteristics were investigated by measuring electroluminescence, transmission, and reflection spectra.

Naphthyridine amide–urea conjugate: a case toward selective fluorometric sensing of N-acetyl proline carboxylate

A simple neutral naphthyridine-based chemosensor 1, which selectively recognizes the tetrabutylammonium salt of N-acetyl-l-proline over the other N-acetyl-l-amino acid salts studied in CHCl3 containing 0.1% DMSO, has been designed and synthesized. Moreover, the complexation-induced change in emission characteristics of 1 distinguishes the amino acid salts examined from their conjugate acids. Interaction studies were performed by UV–vis, fluorescence and NMR spectroscopic methods. A simple neutral naphthyridine –based chemosensor 1, which selectively recognizes the tetrabutylammonium salt of N-acetyl-l-proline in CHCl3 containing 0.1% DMSO, has been designed and synthesized. The complexation-induced change in emission characteristics of 1 distinguishes the amino acid salts from their conjugate acids.

Emission diagnostics of laser plasma on the basis of CuInSe2 compound

The analysis of structure features of volume and film of CuInSe 2 compound is conducted. The spectrums of radiation and oscillogram of intensity of spectral lines of laser erosive plasma are investigated. The spatial and temporal change of emission characteristics of plasma is analysed. The plasma velocity is determined.

Modulated photophysics of 2-anthracene sulphonate in micellar assembly

The association of a non-ionic surfactant of polyoxyethylene-p-(1,1,3,3-tetramethylbutyl)phenyl ether (Triton X) series with 2-AS in aqueous solution has been studied by means of steady-state, time-resolved fluorescence and fluorescence anisotropy techniques. The effect of the hydrophobic chain length on the structural dynamism of the fluorophore has been reported. Experimental results demonstrate that the equilibrium of this dynamism is sensitive to the environment. The association constant of the probe molecule with the non-ionic micelles of Triton X (TX), location of the probe in the micellar environment, have been determined from the change in emission characteristics of the probe as a function of surfactant concentration. The rate constant of quenching and mode of quenching of probe in micellar media have been ascertained. Quantitative estimates of the micropolarity at the binding sites of the probe molecule have been determined. Some of the environment-dependent relevant fluorescence parameters, fluorescence anisotropy ( r), have been monitored for exploring the imposed motional restriction of the microenvironment around the probe. An attempt has been made to correlate the steady-state results with time resolved study.

Correlating composition and luminescence in AlInGaN epilayers

Epilayers of the quaternary alloy Al x In y Ga 1− x− y N have been grown on GaN/sapphire templates by plasma-assisted molecular beam epitaxy. The emission properties and elemental compositions of these samples were evaluated simultaneously and intercorrelated by combining hyperspectral cathodoluminescence imaging and wavelength-dispersive X-ray mapping. Use was made of inherent variations in growth temperature across a single epilayer to study the resultant effect on the different metal fractions and luminescence emission wavelength. By examining statistical correlations in this data, the interdependence of the fractions of constituent binary compounds, together with the associated changes in emission characteristics, can be clarified without the need to grow a systematic series of samples.

Effect of ion impinging on the microstructure and field emission of carbon nanotubes

Effects of ion impinging on the microstructure and field electron emission properties of screen-printed carbon nanotube films were investigated. We observed that the plasma treatment modified the microstructure of CNTs along with the remarkable increase of emission site density. With the prolongation of ion impinging time, the emission current falls down first, and then rises up to higher than that of the untreated films. It is proposed that the change of emission characteristics is due to the different emission mechanisms. After the treatment, electrons are emitted predominantly from the nano-nodes on the tube wall instead from the nanotube tips.

Field emission spectroscopy from field-enhanced diffusion-growth nano-tips

We have found a new formation procedure of nano-tips, namely field-enhanced diffusion-growth (FDG) method. This method has the advantage of forming the nano-protrusion at room temperature, which is quite different from the conventional method by Binh et al. With field ion microscope, we confirmed that the tip was terminated with either a few atoms or the less in the end. The field emission (FE) electrons from the nano-tips converged to a single spot, and the FE current was very stable. The FE spectra consist solely of well-separated peaks. These features are similar to the conventional ones. However, we have found that the FE current and the shape of FE spectrum were so sensitive to the atomic arrangement of the nano-protrusion that the site-shift of only a few atoms caused drastic change in emission characteristics.

Effect of carbon coating on electron field emission from polysilicon

Carbon films deposited at relatively low temperatures were studied as a coating for polysilicon substrates to provide enhancement of the electron field emission. Undoped and phosphor doped polysilicon substrates were coated by carbon films grown by a very high frequency chemical vapor deposition process. Critical process parameters include substrate temperature of 225 °C, pressure of 56 mTorr, loaded power of 2 W/cm2, and discharge frequency of 56 MHz. The substrates were pretreated prior to film deposition, and bias enhanced nucleation was performed in hydrogen/C6H14 plasma. A carbon layer was grown to a thickness of 700 nm. Field emission measurements were performed in an ultrahigh vacuum chamber equipped with an electron gun, a carousel for five samples, and a Faraday cup. A multigrid quasispheric energy analyzer was used for Auger electron spectroscopy and electron energy loss spectroscopy characterization. Additionally, before and after field emission measurements, the secondary emission coefficient σ was measured by a scanning electron beam, which provided a two-dimensional σ map of the sample surface. The field emission current was measured in a diode configuration using a spacer thickness of 45–55 μm through a current collection window 2×5 mm2. Emission current–voltage curves were measured from three different regions of every sample by shifting the current collection window over the sample. A surface conditioning effect was observed, resulting in stabilization and better reproducibility of the emission current–voltage characteristics. The most significant changes in emission characteristics were observed in undoped polysilicon substrates with carbon coatings. Low deposition temperatures make this coating process very attractive because of its compatibility with addressing circuitry based on either silicon or poly-, microcrystalline, or amorphous silicon.

Emission Characteristics of Unburnt HC and Particulate Matter from a Small DI Diesel Engine. 3rd Report. Effect of Fuel Properties.

Many reports, related to the effects of fuel properties on exhaust emissions in DI diesel engines, have been published. It is reported that decreasing of high boiling point fraction, aromatic hydrocarbon and sulfur contents in fuel are effective to reduce PM emissions. However, the effectiveness of these properties differs from researcher to researcher, may be due to the difference in engine specifications. Especially in small DI diesel engines, the fuel properties have significant influence on PM emissions, since much fuel impinges on the combustion chamber walls. To clarify the effect of fuel properties on PM emission in a small DI diesel engine, we investigated the changes of emission characteristics using some paraffinic hydrocarbon fuels with different boiling point. Moreover, the changes in exhaust emissions by the addition of aromatic hydrocarbon to paraffinic, naphthenic and diesel fuel were investigated. The results showed that the amount of SOF when using low boiling point paraffinic fuels decreases to about one tenth of that of diese1 fuel. Blending of the aromatic hydrocarbon with the base fuel of diesel or olefin causes increased amount of SOF emission, but there is no change when the base fuel is para ffin. However, the dry Soot is increased regardless of the base fuel when blending the aromatic hydrocarbon.

Changes in emission characteristics of light-emitting diodes under variation of internal factors and pulse-excitation parameters

A relationship is established between the wavelength λ at the maximum of the near-edge emission band of a light-emitting diode (LED) and the external parameters of the pulse current ti and Q and the thermal time constant τi, which is determined by the product of the thermal resistance and capacitance. A dependence of the shift in λ on the relationship between the LED’s internal and external parameters is discovered. It is shown that for LED operation in the pulsed mode, the shift in λ with variation of ti. Q, and especially τi can reach values on the order of 10 nm (or more), which is a considerable source of errors.

Optical emission studies of laser ablated carbon plasma in a curved magnetic field

The laser produced carbon plasma in different regions of a curved magnetic field has been studied by emission spectroscopy. In addition to the ionic transitions CII, CIII, CIV; C 2 Swan bands are observed. The intensity of the C 2 Swan band is greatly enhanced when the magnetic field lines are convex to the moving plasma with the positive field gradient. The observed change in emission characteristics is attributed to the recombination of electrons due to the curvature gradient drift of the magnetic field.

Laser-induced modification of electron field emission from nanocrystalline diamond films

A significant reduction of electron field emission thresholds resulting from ArF laser irradiation of nanocrystalline diamond films in borazine (B3N3H6) and ammonia (NH3) atmospheres is reported. The change of emission characteristics is not connected with either laser surface graphitization or formation of bulk defects. X-ray photoelectron spectroscopy surface analysis and Raman spectroscopy data from these samples show that laser irradiation results in the synthesis of ultrathin layers of boron–carbon–nitrogen and in B and N atoms intergrain penetration into the film to a depth above 50 Å. The synthesis of the ternary B–C–N and the presence of sp2 bonded C–N compounds is demonstrated.