Shoulder Peak Research Articles

Thermoluminescence properties of nanocrystalline BaSO4 doped with Eu2+ produced by solid state combustion synthesis

Nanocrystalline powder samples of barium sulfate doped with Europium (BaSO4:Eu2+) were prepared, at a dopant concentration of 0.02 mol%, by the combustion solid-state technique in air atmospheres. Thermoluminescence (TL) response and dosimetric studies have been carried out for this phosphor in order to characterize it as a radiation dosimeter. The results showed that the TL glow curve of BaSO4:Eu2+present an intense TL peak at 200 °C accompanied by a small shoulder peak at 270 °C. The TL low detection limit for BaSO4:Eu (0.02 mol%) was found to be 17.8μGy for the gamma radiation emitted by 137Cs. The comparative study with the LiF:Mg, Ti (TLD-100) and calcium fluoride doped with thulium CaF2:Tm dosimeters showed that the TL response of the BaSO4:Eu(0.02 mol%) synthesized by the combustion solid-state technique is highly sensitive: it is 5.8 times higher than the response of the CaF2:Tm pellets and 9.4 times higher than the response of TLD-100. The high sensitivity of BaSO4:Eu and its linear dose response indicate that it can be used as sensor for gamma ionizing radiations.

Discrete AlN mole fraction of n/12 (n = 4–8) in Ga-rich zones functioning as electron pathways created in nonflat AlGaN layers grown on high-miscut sapphire substrates

Ga-rich zones created along macrosteps in n-AlGaN plausibly function as electron pathways of AlGaN-based deep-ultraviolet (DUV) LEDs fabricated on AlN templates using 1.0°-miscut c(0001) sapphire substrates toward the m[1-100] axis. This work was performed to clarify AlN mole fractions (xAl) of Ga-rich zones. xAl ≃ (7/12, 6/12, and 5/12) was observed in Ga-rich zones in AlαGa1−αN (α ≃ 0.63, 0.55, and 0.43, respectively) by the method proposed in our previous article in which we showed that Ga-rich zones of Al8/12Ga4/12N were created in Al0.7Ga0.3N. xAl in the Ga-rich zones obtained from an energy-dispersive x-ray signal by scanning transmission electron microscopy calibrated by Rutherford backscattering well agreed with xAl obtained by cross-sectional cathodoluminescence (CL) spectroscopy using scanning electron microscopy. A weak CL shoulder peak corresponding to Al4/12Ga8/12N was also observed for Al0.43Ga0.57N. In addition, xAl ≃ n/12 (n = 6–9) in Al-rich zones appeared in the rest of the Ga-rich zones. Furthermore, nanobeam electron diffraction patterns of the Ga-rich zones indicated a high possibility of a regular configuration of Ga and Al atoms on the c(0001) plane in our samples. Consequently, xAl values in nonflat AlGaN layers with macrosteps were often determined to be near n/12 (n: integer). Thus, Ga-rich zones (xAl = n/12: n = 4–8) formed in our nonflat AlGaN layers, which originated from the macrosteps along [11–20] edgelines normal to the m[1–100] axis, are suggested to be metastable. The creation of discrete xAl in Ga-rich zones should contribute to the stable production of DUV-LEDs using high-miscut sapphire substrates.

Comparative Study on Au-Ag composition in Lithium Zinc Calcium Fluroborate Glasses: Nonlinear Optics Perspective

20Li2O-15CaF2-20ZnO-45B2O3- 0.XAu-(0.5-X) Ag, (where X= 0.2, 0.3) glasses were prepared by the conventional melt quench technique and coded as 2G3S and 3G2S respectively. The idea of this current work is to check the compositional dependence on the gold and silver nanoparticles in the glass. The XRD results confirmed presence of Au-Ag (111) peak at 38.11. The Infrared spectral study confirms the presence of borate segments. The UV Visible Spectroscopic studies confirms the presence of surface plasmon resonance shoulder peak for Ag nanoparticles around 490nm and 509 nm for glass 2G3S and 3G2S which had overlapped with SPR resonance peak of Au around 603 nm for glass 2G3S and around 559nm for glass 3G2S. The nonlinear optical properties were characterized using Z-Scan experimental technique for these glasses and it suggests the Glass 3G2S exhibited better nonlinear refractive index and nonlinear absorption coefficient compared to Glass 2G3S

Motor Function Assessment of Upper Limb in Stroke Patients.

Background Quantitative assessment of motor function is extremely important for poststroke patients as it can be used to develop personalized treatment strategies. This study aimed to propose an evaluation method for upper limb motor function in stroke patients. Methods Thirty-four stroke survivors and twenty-five age-matched healthy volunteers as the control group were recruited for this study. Inertial sensor data and surface electromyography (sEMG) signals were collected from the upper limb during voluntary upward reaching. Five features included max shoulder joint angle, peak and average speeds, torso balance calculated from inertial sensor data, and muscle synergy similarity extracted from sEMG data by the nonnegative matrix factorization algorithm. Meanwhile, the Fugl–Meyer score of each patient was graded by professional rehabilitation therapist. Results Statistically significant differences were observed among severe, mild-to-moderate, and control group of five features (p ≤ 0.001). The features varied as the level of upper limb motor function changes since these features significantly correlated with the Fugl–Meyer assessment scale (p ≤ 0.001). Moreover, the Bland–Altman method was conducted and showed high consistency between the evaluation method of five features and Fugl–Meyer scale. Therefore, the five features proposed in this paper can quantitatively evaluate the motor function of stroke patients which is very useful in the rehabilitation process.

Effects of growth temperature change in quantum well on luminescence performance and optical spectrum

This paper discusses the effects of extended temperature change time of InGaN well growth on the luminescent properties of blue LEDs with sapphire substrate. Extending the temperature change time will increase the area of the In composition gradient in the quantum well, thereby changing the PL luminescence peak shape, which is conducive to increasing the brightness of the LED. The change of EL-luminescent peaks under different current is further studied. In combination with PL, the source of the shoulder peak on the long-wave-side of the main luminescent peak in the blue light InGaN quantum well growing on the sapphire substrate is explored under normal temperature condition. One illumination mechanism related to a main illuminating center provides a research direction for the improvement of the photoelectric performance of the blue-light LED.

Environmental impact of amino acids on the release of selenate immobilized in hydrotalcite: Integrated interpretation of experimental and density-functional theory study

The environmental impact of amino acids on the release of SeO42− immobilized into hydrotalcite (Mg2Al-LDH) which belongs to the layered double hydroxides (LDHs) family was investigated by experimental study and the observed layer structure of hydrotalcite was verified through density-functional theory (DFT) calculations. Glycine, l-cysteine, and l-aspartic acid, which have smaller molecular sizes, can release SeO42− largely due to intercalation, unstabilization of Mg2Al-LDH and simple dissolution, while l-tryptophan and l-phenylalanine caused limited SeO42− release due to their larger sizes and aromaticity. XRD patterns for the solid residues after intercalation of amino acids revealed that the layer distance of Mg2Al-LDH was partially expanded. The main peaks and shoulder features corresponding to d003 diffraction were well explained by DFT simulations using glycine as a model: the layer spacing of the main peak is responsible for the remaining SeO42− and singly stacked glycine molecule and the layer spacing of the shoulder peak was well explained by doubly stacked glycine molecules. Hydrogen bonds between amino acids and hydroxyl ions in the metallic layers of Mg2Al-LDH were responsible for the stable configuration of the intercalated Mg2Al-LDH. This study indicates potential limitations to the stability of low-level radioactive wastes of 79Se in repositories which are affected by smaller molecules of amino acids released through degradation of organic matters in the pedosphere.

Assessment of Structural Stability of Pure and Xylenol Orange Dye Doped Potassium Dihydroegn Phosphate Probed by Shock Waves

In the present research article, we report the impact of shock waves and the crystallographic structural stability of pure, 0.001 M and 0.01M xylenol orange doped potassium dihydroegn phosphate (KDP) powder samples. The structural stability and crystalline nature of the test samples are demonstrated by powder X-ray diffraction and Raman spectroscopy. The obtained structural properties clearly show that the control sample has a highly stable crystallographic phase at the atomic level. But several shoulder peaks have appeared at shocked conditions due to the lattice distortions and lattice disorders in atomic sites. Among the three samples, 0.001M dye doped KDP exhibits the least shock resistance. The interesting results obtained such as crystallographic phase stability and degree of crystalline stability of the test samples during the course of the experiment are discussed.

X-ray characterization of anisotropic defect formation in SiC under irradiation with applied stress

High-energy x-ray diffraction is employed to gain insight into the irradiation-induced creep behavior of silicon carbide (SiC). Polycrystalline β-SiC specimens were simultaneously exposed to elevated temperature neutron-irradiation and mechanically applied stresses. The structural disordering was subsequently examined using two-dimensional x-ray diffraction. The intensity of the (111) shoulder peak, an indication of stacking disorder, increased when the specimens were irradiated under tensile stress. This is the first observation of nanoscale stress-induced stacking disorder in SiC at low neutron fluences. These findings suggest stress-induced preferential nucleation and/or growth of defect clusters as a key creep mechanism in neutron irradiated SiC.

Difluoroterthiophene as promising block to build highly planar conjugated polymer for polymer photovoltaic cells

Developing highly planar semiconducting polymer is essential for achieving high mobility and improving the photovoltaic performance of bulk-heterojunction polymer solar cells. In this contribution, two novel low-bandgap donor-acceptor copolymers, P1-3T and P2-3T2F, consisting of electron-accepting benzothiadiazole acceptor segment and electron-donating terthiophene donor segment with and without fluorine atoms were designed and synthesized. The density functional theory calculations and ultraviolet–visible absorption studies demonstrate that the fluorinated P2-3T2F polymer has more planar backbone conformation, deeper HOMO level, broader absorption spectrum with a vibronic shoulder peak, and higher absorption coefficient compared with the non-fluorinated analogue polymer, P1-3T. Furthermore, P2-3T2F exhibits good crystallinity and high hole mobility, presumably due to the well-ordered lamellar packing and the π-π stacking interaction between the backbones of the conjugated polymers. The optimized polymer solar cell based on P2-3T2F:PC61BM exhibits a short-circuit current density (Jsc) of 12.77 mA cm−2, a fill factor (FF) of 68.99%, an open-circuit voltage (Voc) of 0.80 V, and a maximum power conversion efficiency (PCE) of 7.14%, which is approximately 46% higher than that of the P1-3T:PC61BM device. The enhanced PCE is primarily due to increased light-harvesting ability and interconnected morphology with finely dispersed polymer-rich and PC61BM-rich domains, which improves the efficiency of exciton dissociation and rises the mobility of charge carriers, thus boosting the short-circuit current density and the FF value. Moreover, the relatively deep HOMO of P2-3T2F effectively increases the Voc.

A metric-based assessment of climate and tourism in major cities of Pakistan

Tourism plays an essential role in the economic development of a country and has become a growing phenomenon of global importance. The climate change on the other hand has a direct effect and degrades the environmental components and features of the destinations. Pakistan is highly vulnerable to changing the climate which has threatened the tourism sector. The study has emphasized on the significance of the climate in the tourism industry by using the Tourism Climate Index (TCI) which highlights suitable regions and seasons. TCI has been used worldwide to enumerate the impacts of climate change on tourism and tourist destinations. The current study calculates the TCI for four cities of Pakistan, chosen by public opinion. For measuring the index, climatic data of twenty-one years (1997–2017) were taken from the Pakistan Meteorological Department, which include temperature, precipitation, sunshine hours, humidity and wind speed. The results showed that among the seasonal distribution, autumn and spring are good seasons for tourism. Climatic suitability in summer was not favorable for Lahore and Islamabad because of high rainfall and lower thermal comfort. A rapid change in the Annual TCI score was observed and investigated through the contribution of TCI components which happens to be the core reason for the change. Analysis has shown that 75% of the study area as a Bi-modal shoulder peak and 25% as a winter peak. For city Lahore, a maximum number of months were observed as “Excellent” and “Good” for tourism due to a high TCI score. Furthermore, future projection predicts that tourism in Lahore will be highly threatened due to rapidly changing climate. Government and tourism stakeholders should conduct such relevant studies at large scale for a better understanding of favorable and unsuitable tourist destinations across Pakistan.

Stretchable strain sensors with dentate groove structure for enhanced sensing recoverability

Stretchable strain sensors based on conductive polymer composites commonly utilize elastic polymers as the matrix. However, elastic polymers always show strong mechanical hysteresis effect leading to shoulder peak phenomenon and thereby poor recoverability of strain sensors. Herein, we design a stretchable rough filament strain sensor with dentate groove structure to eliminate the shoulder peak phenomenon and improve recoverability. The filament strain sensor is fabricated by the extrusion of poly(styrene-b-ethylene-b-butylene-b-styrene) (SEBS) filament constructing dentate groove structure and the subsequent ultrasonic treatment decorating carbon nanotubes (CNTs) on the surface of the SEBS filament. It is interesting to find that the strain sensing range of rough SEBS/CNTs filaments with dentate groove structure is wider than that of smooth filaments. More importantly, the rough filament strain sensors exhibit significantly enhanced recoverability without shoulder peak during the releasing process while the rough dentate groove structure has minor effects on the mechanical properties of SEBS filaments. The great improvement is ascribed to the uniform distribution of deformation because of the dentate groove structure, which induces reduction of the mechanical hysteresis effect and thereby decreases residual strain. Moreover, the rough filament strain sensors have a favorable integration of good stability, fast response time of 300 ms (0.5% strain is applied with a high strain rate of 500 mm/min) and excellent durability (1976 cycles at the strain of 50%). The rough filament strain sensors can accurately and stably monitor both large and subtle human motions (such as body motion, expression and phonation), showing broad application prospects in wearable devices.

Continuous-wave operation of an electrically pumped single microribbon based Fabry-Perot microlaser.

Fabry-Perot (FP) mode microlasers have been popularized and applied widely in on-chip coherent light sources because of the unique advantages of directional output emission. In this work, a heterojunction light-emitting diode (LED) made of a Ga-doped ZnO (ZnO:Ga) microribbon and p-GaAs template is fabricated. And its electroluminescence characteristics of strong coupling of exciton-photon and polariton lasing, in the blue-violet spectrum, were demonstrated under continuous-wave operation of an electrical injection. In the device structure, a single microribbon with a rectangular-shaped cross section can achieve the FP-mode lasing action by the optical oscillation between the two lateral sides of the microcrystals in the ultraviolet spectrum. As the reverse-current is below the threshold value, the device can have radiative polaritonic lighting directly from bilateral sides of the microribbon, yielding strong coupling between excitons and FP-mode microresonator. And the exciton-polariton coupling strengths characterized by a Rabi splitting energy were extracted to be 500 meV. Further, when the input current increased more than a certain value, strong laser illuminating developed as two sharp peaks at the lower energy shoulder of the spontaneous emission peak, and these oscillating modes can dominate the waveguide EL spectra. The experimental results can provide us with further unambiguous evidence that the lasing is originated from the polariton resonances for the microribbon with strong exciton-polariton coupling. Since single microribbon based optical FP-mode microresonators do not require additional feedback mirrors, their compact size and resulting low thresholds make them a powerful candidate to construct on-chip coherent light sources for future integrated nanophotonic and optoelectronic circuitry.

Resistance-strain sensitive rubber composites filled by multiwalled carbon nanotubes for structuraldeformation monitoring

In this article, multiwalled carbon nanotube/natural rubber composites with resistance-strain sensitivity were prepared by solution method, when the electrical percolation threshold of multiwalled carbon nanotube is only ∼3.5 wt%. The mechanical properties and resistance-strain response sensitivity were studied and analyzed systematically. The dispersion of multiwalled carbon nanotubes in the natural rubber matrix was characterized by field-emission scanning electron microscope and X-ray diffractometer. The composite exhibits good deformation sensitivity (gauge factor >27), large strain sensing range (>200%), and high signal stability when multiwalled carbon nanotube content was appropriate. The composite is suited to application in strain monitoring of large deformation structures since the resistance-strain response is more stable when strain exceeds 100%. To understand the mechanism of the resistance-strain response, the ‘shoulder peak’ of resistance-strain curve was researched and explained by the digital image correlation method, and an analytical model was developed when considering the effects of electronic tunneling and hopping in multiwalled carbon nanotube networks. Both experiment and analytical results confirm the break-restructure process of multiwalled carbon nanotube networks under applied strain cause the resistance-strain response. Finally, the practical application of the composite to monitoring strain load of rubber isolation bearing was realized.

Terahertz Spectroscopy and Molecular Modeling of Barbituric Acid

The well-resolved terahertz (THz) absorption spectrum of barbituric acid has been investigated using terahertz time-domain spectroscopy. Four distinct THz spectral features and two shoulder peaks were observed in the range of 10–124 cm–1. A complete analysis was performed with density functional theory, which provided an excellent agreement between solid-state simulation and experiment. The solid-state analysis indicates that the six experimental spectral features observed at low temperature consist of nine infrared-active vibrational modes. Further simulations based on hydrogen-bond isotopologues were performed to study the involvement of hydrogen bonds in the collective modes. A feature at 118.0 cm–1 mainly stems from the collective vibration of dimer hydrogen bonds (m) while features at 102.0 and 109.6 cm–1 primarily come from the collective vibrations of linear hydrogen bonds (n). The results may be useful for monitoring molecular reaction in industrial production according to the state of hydrogen bonds.

Pyrolysis characteristics and kinetics of lignin: effect of starting lignins

ABSTRACT To elucidate the impact of starting lignins on pyrolysis characteristics and kinetics of lignin, seven lignins were pyrolyzed on a thermogravimetric (TG) analyzer. Results show that hardwood lignins showed derivative thermogravimetric (DTG) curves with one weight loss peak, softwood lignin showed a curve with two weight loss peaks, while grass lignins showed curves with a main weight loss peak and a shoulder peak. The average apparent activation energy (Ea ) obtained with Starink model-free method varied greatly across the lignins. Prepared under mild conditions, the Ea values followed the order as grass lignin > hardwood lignin > softwood lignin. The most probable mechanism functions (MPMF) determined by Coats-Redfern model-fitting method also depended upon the lignins. This work shows that the slow pyrolysis behavior of lignin and the kinetic parameters are tightly related to its structure which depended greatly upon the biomass sources and isolation methods. More weak linkage structures, like β − O − 4 linkage, ferulates, and p-coumarates, could lead to the lower activation energy.

Effects of service condition on the performance of conductive polymer composites for flexible strain sensors

Flexible strain sensors based on conductive polymer composites (CPCs) are widely used in wearable electronics and electronic skin due to their simple preparation and outstanding performance. However, the performance like sensitivity and dynamical stability of flexible strain sensors is coupled with complex operational conditions, which prevents the sensors from large-scale practical applications. In this work, the effects of different loading rates and loading modes on the performance of the flexible strain sensor were systematically investigated. It was found that high loading rate can increase the sensitivity and the degree of hysteresis phenomenon (shoulder peak, spoon valley and drift), which is attributed to the viscoelasticity of polymer. Meanwhile, non-uniform loading mode has insignificant influence on the sensitivity and hysteresis of strain sensors in comparison to uniform loading mode. Moreover, the force-electric equivalent model was proposed to explain the causes of various hysteresis phenomena as well as the sensitivity mechanism affected by loading rate. Furthermore, a theoretical formula of the resistance of flexible strain sensor was presented and optimized to describe the relationship of variation of resistance against different loading rates. These presented results bring useful insights on the exploration of CPCs based strain sensors for wide applications under complex service conditions.

THE RELATIONSHIP OF RANGE OF MOTION, HIP SHOULDER SEPARATION, AND PITCHING KINEMATICS.

When pitching a baseball, pelvic and trunk pitching kinematics play an integral role in momentum transfer from the lower extremity to the upper extremity. However, it is unknown how hip and trunk ROM and hip shoulder separation interplay with pelvic and trunk pitching kinematics. To determine the relationship between clinical trunk and hip range of motion (ROM) and pitching biomechanical pelvis and trunk kinematics, and kinematic sequencing. Controlled biomechanical study. High school pitchers were assessed for trunk rotation via motion capture and hip ROM via a goniometer prior to pitching. Trunk rotation was designated as dominant and non-dominant sides, and hips as stance and lead limbs. Pitchers threw four fastballs during three dimensional biomechanical assessment. Spearman's Rho correlations were performed between trunk and hip ROM, and trunk and hip biomechanical kinematics, and kinematic pitching sequence. Thirty-two pitchers (mean age: 16.3 ± 1.2 years, height = 184.0 ± 6.9 cm, mass = 76.8 ± 20.8 kg) were included in this study. Their mean pitch velocity was 34.7 ± 2.3 m/s, peak pelvis rotation velocity: 669.1 ± 95.5 deg/s, and peak trunk rotation velocity: 1084.7 ± 93.0 deg/s. There were no differences between dominant and non-dominant side trunk rotation, or between stance and lead hip ROM. There were no significant relationships between trunk or hip ROM and pitching kinematics. There was a significant relationship between hip shoulder separation and peak trunk rotation velocity (r = 0.390, p=0.027). There was a significant relationship between pitch velocity and peak trunk rotation velocity (r = 0.478, p = 0.006). There were no other significant relationships between pitching kinematics or kinematic sequencing. Hip shoulder separation is related to trunk rotation velocity, and ultimately pitch velocity. These ROM measurements can be used as normative values for hip shoulder separation in high school pitchers. 3.

Hematological Analysis and Diagnosis of Two Rare Abnormal Hemoglobin

To analyze the hematological characteristics of Hb Broomhill and Hb Hornchurch, and prenatal diagnosis should be carried out in two families. RBC parameters and hemoglobin electrophoretogram were analyzed on the peripheral blood of all patients, and amniotic fluid was collected for prenatal diagnosis. PCR-Flow fluorescent hybridization and Sanger sequencing were performed for gene diagnosis of thalassemia. Three cases of Hb Broomhill were detected, including 2 cases with common SEA α-thalassemia, which was characterized by hypochromic microcytic mild anemia, the capillary electrophoregram revealed a tiny shoulder peak before the Hb A peak; 1 case was diagnosed as Hb Hornchurch combined with β-thalassemia, which also showed mild anemia. Hemoglobin electrophoretogram showed an abnormal hemoglobin variant peak at Hb A2 zone. The carriers of Hb Broomhill and Hb Hornchurch do not have microcytic hypochromic anemia, which do not aggravate the hematological symptoms, such as anemia when being combined with thalassemia of the same type.

Helically Grooved Gold Nanoarrows: Controlled Fabrication, Superhelix, and Transcribed Chiroptical Switching

Plasmonic chiroptical materials, coupled by chirality and surface plasmons, have been attracting great interest due to their potential applications, such as photonics, chiral recognition, asymmetri...

Investigation of localized state emissions in quaternary InGaAsSb/AlGaAsSb multiple quantum wells grown by molecular beam epitaxy

As an essential structure of infrared semiconductor lasers, the optical properties of InGaAsSb/AlGaAsSb multiple quantum wells need to be fully investigated. In this paper, the temperature and excitation power-dependent photoluminescence (PL) spectra of the InGaAsSb/AlGaAsSb MQWs are measured. A strong free exciton emission with a photon energy of 0.631 eV was observed at room temperature. Besides the main peak, an obvious shoulder peak, located at the low photon energy position under low temperature range (T≤90 K), was confirmed to be an emission of defect related localized carriers by power-dependent PL spectra. The power-dependent PL spectra were dominated by the localized carriers emission under low excitation power (Iex≤20 mW), while the free-exciton emission dominated the PL spectra gradually when excitation power higher than 40 mW. This phenomenon is ascribed to the dissociation of localized states. Our work is of great significance for the device applications of InGaAsSb/AlGaAsSb multiple quantum wells.