Variation Of Gap Research Articles

Comprehensive Structural, Chemical, and Optical Characterization of Cu2ZnSnS4 Films on Kapton Using the Automated Successive Ionic Layer Adsorption and Reaction Method

This study provides a comprehensive structural, chemical, and optical characterization of CZTS thin films deposited on flexible Kapton substrates via the Successive Ionic Layer Adsorption and Reaction (SILAR) method. The investigation explored the effects of varying deposition cycles (40, 60, 70, and 80) and annealing treatments on the films. An X-ray diffraction (XRD) analysis demonstrated enhanced crystallinity and phase purity, particularly in films deposited with 70 cycles. These films exhibited a notable reduction in secondary phases in the as-deposited state, with further improvements observed after annealing at 400 °C and 450 °C in a sulfur atmosphere. A pole figure analysis indicates a decrease in texture disorder with annealing, suggesting improved crystalline orientation at higher temperatures. Field emission scanning electron microscopy (FE-SEM) showed enhancements in surface morphology, with increased grain size and uniformity post-annealing. Chemical uniformity was confirmed through Secondary Ion Mass Spectrometry (SIMS), Energy-Dispersive Spectroscopy (EDS), and X-ray Photoelectron Spectroscopy (XPS). XPS revealed the presence of CZTS phases alongside oxidized phases. Annealing effectively reduced secondary phases, such as ZnO, SnO2, CuO, and SO2, enhancing the CZTS phase. An optical analysis demonstrated that annealing at 200 °C in an air atmosphere reduced the band gap from 1.53 eV to 1.38 eV. In contrast, annealing at 400 °C and 450 °C in a sulfur atmosphere increased the band gap to 1.59 eV and 1.63 eV, respectively. The films exhibited p-type conductivity, as inferred from a valence band structure analysis. Density Functional Theory (DFT) calculations provided insights into the observed band gap variations, further substantiating the findings.

Electronic confinement induced quantum dot behavior in magic-angle twisted bilayer graphene.

Magic-angle twisted bilayer graphene (TBLG) has emerged as a versatile platform to explore correlated electron phases driven primarily by low-energy flat bands in moiré superlattices. While techniques for controlling the twist angle between graphene layers have spurred rapid experimental progress, understanding the effects of doping inhomogeneity on electronic transport in correlated electron systems remains challenging. In this work, we investigate the interplay of confinement and doping inhomogeneity on the electrical transport properties of TBLG by leveraging device dimensions and twist angles. We show that reducing device dimensions can magnify disorder potentials caused by doping inhomogeneity, resulting in pronounced carrier confinement. This phenomenon is evident in charge transport measurements, where the Coulomb blockade effect is observed. Temperature-dependent measurements reveal a large variation in the activation gap across the device. These findings highlight the critical role of doping inhomogeneity in TBLG and its significant impact on the transport properties of the system.

Electron and hole energy spectrum of non-concentric spherical core-shell quantum dot under an externally applied electric field

A model of the non-concentric spherical core–shell quantum dot under the influence of an externally applied electric field was proposed. It was established that the energy spectrum of both the electron and the hole depends on the intensity of the electric field as well as on the specific location of the core within the quantum dot. The phenomenon of energy level splitting and degeneration was analyzed in detail. Additionally, the variations in the optical gap were determined and expressed as a function of the applied electric field strength and the position of the core in the quantum dot.

Maternal Health Planning and Prioritization in Chad: Developing a supportive tool.

The Republic of Chad has one of the highest rates of maternal mortality in the world. With scarce resources to respond to competing demands, pragmatic evidence-based planning tools are needed to aid planning and support priority setting. This action research aimed to develop a tool to support maternal health (MH) planning and prioritization decisions and identify priority regions/provinces for intervention in Chad based on aggregate MH coverage gap scores (Target-Coverage=Coverage Gap). A rapid review was conducted to identify key indicators and relevant national targets. The 2019 Multiple Indicator Cluster Survey and other national surveys were the data sources for selected indicators at the provincial level. Aggregate MH coverage gaps were calculated and displayed using Geographic Information System software to visualize variations by province. Eleven key informant interviews (KIIs) and six focus group discussions (FGDs) were conducted with clinicians and administrators to understand existing MH planning, prioritization, and maternal mortality risks in Chad. Wide provincial variation in aggregate MH coverage gaps was identified (mean score 374.3, SD: 77.4). Indicators contributing the most to coverage gaps include emergency obstetric care, adolescent births, tetanus vaccination, and delivery by skilled health personnel. Two weighting scenarios for the coverage gap scores are also considered. KIIs and FGDs revealed that existing MH planning in Chad differs provincially and by health system level, with no clear prioritization processes identified. Main themes regarding MH risks reported by stakeholders included challenges relating to the health system, policy landscape, country and population-specific factors, along with specific MH threats. Current centralized planning approaches may benefit from greater consideration of provincial differences to support more efficient and equitable resource distribution. This multi-indicator assessment offers an adaptable approach for evidence-based MH resource allocation to prioritize sub-national areas with worst health indicators in resource-limited settings, although further research is needed to test its impact.

Observing periodic gap variations in cuprates

The presence of multiple orders in strongly correlated electronic materials like the cuprate superconductors, coupled with spatial inhomogeneity, poses a challenge to the interpretation of spectroscopic data taken on them. Here, we present a technique that directly acknowledges these orders and inhomogeneities and extracts statistically significant features from such data. Applying this technique to scanning tunneling spectroscopy measurements from single and bilayer cuprates spanning a wide doping range, we peer through local inhomogeneities and identify a gaplike feature that breaks translational and rotational symmetries and varies periodically in a fourfold pattern. This identification of spectral features aligns well with theoretical predictions of spatially modulated pair density. Published by the American Physical Society 2024

Insights into Selective Sensitivity of In2O3-CuO Heterojunction Nanocrystals to CH4 over CO and H2: Experiments and First-Principles Calculations.

Metal oxide semiconductor gas sensors have demonstrated exceptional potential in gas detection due to their high sensitivity, rapid response time, and impressive selectivity for identifying various sorts of gases. However, selectively distinguishing CH4 from those of CO and H2 remains a significant challenge. This difficulty primarily stems from the weakly reducing nature of CH4, which results in a low adsorption response and makes it prone to interference from stronger reducing gases in the surroundings. Herein, we synthesized In2O3-xCuO nanocomposites using a hydrothermal method to explore their gas sensing properties toward CH4, CO, and H2. Characterization tests confirmed the successful preparation of In2O3-xCuO nanocomposites with different In:Cu molar ratios and the formation of a p-n heterojunction. The gas sensing test results indicated that the In2O3-2.1CuO nanocomposites calcined at 500 °C and measured at 350 °C displayed a p-type response for CH4 and an n-type response for CO and H2, allowing for accurate differentiation of CH4 from CO and H2. Moreover, the In2O3-2.1CuO sensor also showed excellent stability and reproducibility across all three gases. First-principles calculations revealed distinct changes in the electronic structure of the In2O3-CuO heterojunction upon adsorption of CH4, CO, and H2, a finding that aligns with empirical evidence. The gas selectivity mechanism was effectively explained by variations in the energy band gap, driven by electrical behavior during the adsorption process. This work suggests a promising approach for developing selective gas sensors capable of detecting weakly reducing gases.

Ultraviolet Radiation Driven Multifunctional Polyvinyl Alcohol Based Hybrid Polymer Nanocomposites

ABSTRACTHerein we report the tailoring of the band gap of polyvinyl alcohol (PVA)/graphene oxide (GO), PVA‐Ag (silver), PVA/GO‐Ag, and PVA/GO/Ag/GA (glutaraldehyde) employing ultraviolet (UV) irradiation. Nanocomposites were fabricated by the in situ solution casting method. Among fabricated, PVA/GO/Ag/GA was identified as the nanocomposite having enhanced properties. The structural and chemical studies confirm enhanced interfacial interaction and crosslinking between PVA and GO in the presence of GA. GA crosslinked PVA/GO‐Ag nanocomposite shows a reduction in band gap and enhanced dc conductivity compared to other composites. Post‐UV irradiation studies show PVA/GO/Ag/GA exhibits mechanical stability and good conductivity. The band gap of PVA/GO/Ag/GA decreased from 5.27 eV (unirradiated) to 2.66 eV for 24 h of UV exposure. As the exposure time increased to 48 h, the band gap increased to 5.16 eV and finally band gap decreased to 4.47 eV for 72 h of UV exposure. This reveals that though there is no linear variation in the energy gap with UV exposure time but accurate reproducibility was observed. This brings about the possibility of tailoring the band gap of PVA/GO/Ag/GA with better electrical conductivity (3.4 × 10−9 Sm−1) and good mechanical stability which is very crucial for optoelectronic applications. Additionally, for 72 h of UV radiation exposure, the PVA/GO/Ag/GA composite demonstrates UV transmittance of 3.3%, underscoring its UV shielding capability.

Exploring Electronic and Conformational Attributes of an Organic Donor‐Bridge‐Acceptor Molecular System

AbstractThis research explores the electronic properties and conformational dynamics of the ZnP‐COPV‐ (Zinc Porphyrin ‐ Carbon bridged Oligo Phenylenevinylene ‐ Fullerene) organic semiconductor via specialized Density Functional Theory (DFT) and Molecular Dynamics (MD) computational techniques. First, through DFT calculations, essential HOMO (Highest Occupied Molecular Orbital), LUMO (Lowest Unoccupied Molecular Orbital), and Molecular Electrostatic Potential (MEP) electronic attributes are meticulously dissected providing insights into the intricate charge transfer processes between the constituent donor‐acceptor moieties. Furthermore, MD simulations are employed to unveil the molecular system's multifaceted conformational flexibility and stability. The Root‐mean‐squared deviation (RMSD), end‐to‐end distance, and torsional angles quantitative analysis of conformational attributes support the carbon‐bridged oligo‐phenylenevinylene (COPV) molecular wire's ‐skeleton planar and rigid conformation. This minimal end‐to‐end distance variation (within Å) compared to the initially extended structure and the constrained torsional motion (within for ZnP‐COPV and for COPV‐) after thermalization showcases COPV's ability to maintain structural rigidity over time, aligning with the concept of effective ‐conjugation. Finally, through the lens of time dependent (TD)‐DFT, the dynamic evolution of the HOMO–LUMO energy gap, TD‐DFT excitation energies and oscillator strengths are explored as the molecular structure transforms over time. The observed energy gap variation underscores the molecule's adaptability in the face of structural modifications, hinting at an intriguing connection between structural stability and enhanced electronic properties. The research provides a comprehensive understanding of the intricate interplay between conformational dynamics and electronic attributes in organic semiconductors, providing quantitative insights crucial for designing stable, high‐performance materials for cutting‐edge optoelectronic applications and helping advance the collective understanding of sustainable energy conversion.

A Discovery of Pressure-Induced New Semiconductor Electronic Phase Transitions by DFT Calculations: Introducing a Glimpse of a Novel Semiconductor Family.

This study introduces a discovery of pressure-induced new semiconductor electronic phase transitions. A novel semiconductor family that exhibits pressure-induced nonmonotonic changes in band gaps was found and meets the definition of phase transitions, challenging the traditional understanding of linear and monotonic band gap modification through pressurization. Our findings suggest a complex interplay of atomic spacing and electron orbital contributions under varying pressure conditions, resulting in the variation of band gaps. This behavior, which includes three distinct steps: first, narrowing, second, broadening, and third, narrowing again and ultimately metalizing; some compounds could bypass step 1, has potential applications in piezoelectric and semiconductor technologies. We propose two new semiconductor electronic phase transitions (SEPT) associated with specific inflection points in the pressure-dependent band gap curve. Our results open avenues for further research into the electronic properties of crystals under high pressure, with the ultimate goal of uncovering the more profound physical principles governing these phenomena.

Disparities in management of symptomatic osteoporotic vertebral compression fractures: a nationwide multidisciplinary survey

SummaryThis nationwide multidisciplinary survey found dissatisfaction among physicians with current osteoporotic vertebral compression fracture care, revealing significant disparities in diagnosis, treatment, and follow-up practices. Issues include poor communication and differing guidelines. Improving interdisciplinary collaboration and standardized care strategies is essential for better patient outcomes.PurposeThis survey aims to assess current preferred care practices for symptomatic osteoporotic vertebral compression fractures (OVCF) in the Netherlands, focusing on guideline adherence, identifying knowledge gaps, and clarifying consensus and collaboration across medical disciplines in OVCF treatment.MethodsThis cross-sectional study was conducted via Qualtrics (Provo, UT) using a self-administered online survey distributed to 238 general practitioners and physicians in orthopedics, traumatology, internal medicine, rheumatology, and geriatrics working at 51 hospitals in the Netherlands. The survey, conducted in Dutch, included 36 multiple-choice and two open questions and was accessible via an anonymous email link or QR code. General practitioners received additional questions specific to their role. Data was anonymized, stored securely, and analyzed using descriptive statistics in Microsoft Excel and SPSS (Version 24). Open-ended responses were coded and categorized. The survey was conducted prior to the publication of the updated Federation of Medical Specialists guidelines in 2024.ResultsPhysicians across various disciplines uniformly expressed dissatisfaction with current OVCF care. The survey highlighted significant disparities in diagnosis, treatment, and follow-up practices. A lack of communication between primary and secondary care providers and differing guidelines further complicate OVCF management. These issues point to considerable variation in clinical practice and gaps in interdisciplinary collaboration.ConclusionAddressing the identified issues requires fostering interdisciplinary collaboration and creating cohesive care strategies. Ensuring access to diagnostic resources in both primary and secondary care and establishing coordinated care models promises more structured and standardized treatment. These steps are crucial for enhancing patient outcomes in OVCF management.

Stress affects the electronic transition and effectively regulates the optical properties of SnS2

SnS2 is a Ⅳ-Ⅵ group semiconductors, and has excellent photoelectronic properties, but the properties are significantly affected by stress. So, the properties and influence mechanism are studied using first principles method. The band gap of SnS2 shows three changes points with stress, which occurs at 1.0 GPa, 7.0 GPa and 8.0 GPa, respectively. The reason is that the electrons of Sn-5 s, Sn-5p and S-3p are sensitive differently to stress, the electrons are easy to be excited, and the electronic structure and optical properties are affected. The ε1 and η of SnS2 show three different variation rules, which are similar to the variation of the band gap, and the first peak of ε1 increases with the increase of stress. ε2, the edge of absorption and k are move to the direction of low energy with the increase of stress. It is means that stress can effectively regulate the electronic structure of SnS2 and improve the utilization of light.

Dosimetry in MRgPT: Impact of magnetic fields on TLD dose response during proton irradiation.

Proton beam therapy, when integrated with MRI guidance, presents complex dosimetric challenges due to interactions with magnetic fields. Prior research has emphasized the nuanced impact of magnetic fields on dosimetry. For thermoluminescent dosimeters (TLDs) the electron-return effect, alongside small air cavities surrounding the pellets, can lead to nonuniform dose distributions. Future MR-guided proton therapy will require reliable methods for end-to-end tests and dosimetric audits, which so far are often performed using TLDs equipped with phantoms. This implicates the necessity of accounting for theseinteractions. This study investigates the influence of magnetic fields on TLDs at two proton energies, using magnetic field strengths of 0, 0.25, and , aiming to clarify their impact on dose measurementaccuracy. The study was conducted at a synchrotron-based ion beam therapy beam line, enhanced by a resistive dipole magnet for creating magnetic fields up to to simulate MR-guided proton therapy. Individual correction factors were applied for TLD measurements. The impact of air gaps on the TLD signal was evaluated using three dedicated TLD holders with air gaps of 0.1, 0.25, and 0.5 mm surrounding the TLD pellets using the highest available proton energy of . Additionally, the influence of the magnetic field strength on the TLD response was evaluated for two proton energies of and . The study found no statistically significant variation in TLD dose response attributable to changes in the air gap or the presence of magnetic fields. A power analysis indicated an upper limit on a potential change in dose-response as small as 1.5%. The findings suggested that the impact of air gap variations and magnetic field strengths on the TLD response was below the detection threshold of TLD sensitivity. This emphasizes the suitability of TLDs for dose measurement in MR-guided proton therapy, indicating that additional correction factors may not be necessary despite the influence of magneticfields.

Gap tolerance and molten pool destabilization mechanism in oscillating laser-arc hybrid welding of aluminum alloys

Oscillating laser-arc hybrid welding (O-LAHW) offers significant advantages in enhancing efficiency and mechanical properties. However, in actual production, gap fluctuations can cause instability, limiting its application in large-scale structure manufacturing. In this study, we explored the impact of gap fluctuation on the destabilization of the molten pool in aluminum alloy O-LAHW and identified the maximum gap tolerance for various conditions. High-speed photography revealed that the oscillating molten pool undergoes a transitional state of periodic collapse before complete instability, a behavior distinct from that of a non-oscillating molten pool. We also analyzed the variations in weld geometry prior to destabilization and developed a global force model of the molten pool to identify key geometrical parameters and related driving forces contributing to destabilization. The results show that maintaining a surface tension ratio of over 55 % at the root of the molten pool is crucial for its stability. Additionally, the effects of oscillatory behavior and gap variations on the laser-substrate interaction were explored, revealing the physical mechanisms behind the changes in key geometrical parameters of the melt pool cross-section. The centrifugal effect generated by high-frequency oscillation is identified as a crucial mechanism for extending the duration of periodic collapse compared to non-oscillating molten pools. By discussing the interactions between energy absorption, molten pool shape, and molten pool forces, the study reveals the evolution process of weld destabilization and explains the differences in gap tolerance between oscillating and non-oscillating laser-arc hybrid welding, providing a reference for improving weld stability.

Band Gap Variation and Structural Disorder in the Two-Dimensional Mixed-Halide Hybrid Lead Perovskites

Band Gap Variation and Structural Disorder in the Two-Dimensional Mixed-Halide Hybrid Lead Perovskites

Structural, electronic, optical and thermoelectric properties of FrSnI3-xFx (X=0, 1, 2, 3) perovskites using the TB-mBJ approach

In this study, we investigate the structural, optical, electronic, and thermoelectric properties of FrSnI3-xFₓ (x = 0, 1, 2, 3) perovskites using density functional theory with the modified Becke-Johnson method (TB-mBJ) for exchange correlation functions. This research is the first theoretical investigation of these promising materials. Our results show that each variant of the perovskite exhibits p-type semiconductor behavior, and that the energy gap of FrSnI₃ can be tuned by substituting an iodine atom with fluorine. This substitution causes a significant variation in the energy gap, ranging from 1.169 eV to 2.951 eV. In particular, the FrSnI₂F compound stands out with a direct gap of 1.539 eV, making it an ideal candidate for solar cell applications. Optical properties, including real and imaginary dielectric function components, absorption and refractive indices, highlight the performance of these materials. Their high absorption capabilities suggest that these perovskites can be tailored and integrated into optical and optoelectronic devices in a variety of spectral ranges.Furthermore, thermoelectric property calculations using BoltzTrap software show that FrSnI3-xFₓ (x = 0, 1, 2, 3) has a promising Seebeck coefficient and an impressive figure of merit approaching unity at high temperatures. These results underscore the immense potential of these materials in thermoelectric applications, opening the door to new possibilities in energy conversion technology.

Impact of air gap thickness on acoustic metamaterials with internal simple expansion chamber structure

The air gap thickness plays a significant role in enhancing sound absorption. This study explores the role of air gap thickness in enhancing sound absorption in 3D-printed acoustic metamaterials (AMMs) featuring a Simple Expansion Chamber (SEC) structure. Nine samples (B1 to B9) were designed and then 3D-printed with varying SEC lengths (2-18 mm) maintaining an area expansion ratio of 16. An air gap (5-30 mm) was introduced between each sample and the rigid backing. The Sound Absorption Coefficient (SAC) was measured using the Impedance Tube Apparatus. Results showed a notable increase in peak SAC from 0.57 to 0.96 with a 5 mm air gap for a sample with a 2 mm long SEC. However, this effect did not replicate across other samples, suggesting the peak SAC was unaltered by further variation of the air gap. Additionally, the peak absorption frequency exhibited an exponential reduction with increasing air gap thickness. This research illuminates the nuanced relationship between air gap thickness and the acoustic performance of 3D-printed materials, offering insights for optimizing sound absorption in diverse applications. Keywords: Air gap thickness, Simple Expansion Chamber, Area expansion ratio, Sound Absorption Coefficient, Sound Transmission Loss

Changes in Family Structure and Increasing Care Gaps in the United States, 2015–2050

Research on caregiving in the United States has not clearly identified the scope of the gap between care needed and care received and the changes implied by ongoing and anticipated shifts in family structure. This article examines the magnitude of contemporary gaps in care among older adults in the United States and how they are likely to evolve through 2050. We use data from the Health and Retirement Study (1998–2014) to estimate care gaps, operationalized as having difficulties with activities of daily living (ADLs) or instrumental activities of daily living (IADLs) but not receiving care. We also estimate variation in care gaps by family structure. Then, we use data from demographic microsimulation to explore the implications of demographic and family changes for the evolution of care gaps. We establish that care gaps are common, with 13% and 5% of adults aged 50 or older reporting a care gap for ADLs and IADLs, respectively. Next, we find that adults with neither partners nor children have the highest care gap rates. Last, we project that the number of older adults with care gaps will increase by more than 30% between 2015 and 2050—twice the rate of population growth. These results provide a benchmark for understanding the scope of the potential problem and considering how care gaps can be filled.

Evaluation of Dural Venous Sinus Variations through Three-dimensional Phase-Contrast Magnetic Resonance Venography

Objective: The aim of this study was to evaluate the anatomy of dural venous sinus variations through three-dimensional phase-contrast (3D-PC) magnetic resonance venography (MRV). Awareness of the normal anatomical variations of venous sinuses and apparent MRV flow gaps prevent misdiagnosis of dural venous sinus diseases. Materials and Methods: The dural venous sinuses were assessed using nonenhanced 3D PC-MRV. Of these 968 patients, 154 were excluded due to venous thrombosis and mass invasion. A total of 814 patients (186 male and 628 female) were included in the study. Results: The most common variation of superior sagittal sinus (SSS) was atresia of anterior one-third SSS 19 (2.3%). Other variations were hypoplasia of the anterior half of SSS 2 (0.2%), atresia of posterior one-third of SSS (7, 0.9%), and combined variation of SSS (13, 1.6%). The left transverse sinus was hypoplastic in 224 (27.5%) and aplastic/atretic in 259 (31.8%) cases. The right transverse sinus was hypoplastic in 76 (9.3%) and aplastic/atretic in 57 (7.0%) patients. The combined variation of bilateral transverse sinuses had 42 (5.2%) cases. The left sigmoid sinus was hypoplastic in 22.2% (181) of cases. The right sigmoid sinus was hypoplastic in 60 (7.4%). Two patients had hypoplastic bilateral sigmoid sinuses (0.2%). The right occipital sinus was identified in 20 (2.5%) patients. Left occipital sinus was noted in 2 (0.2%) patients. Duplication or triplication of the occipital sinus is noted in 5 (0.6%) study populations. Straight sinus continued in 13 (1.6%) cases with the right transverse sinus and in 29 (3.6%) patients with left transverse sinus. Conclusion: These anatomical variants can be a potential pitfall in the MRV diagnosis of dural sinus variations, especially when there are no supportive imaging features such as brain infarcts or appropriate clinical background. 3D PC-MRV is a great option for patients with gadolinium allergy/renal insufficiency/pregnant patients. We hope this article can add information and assist in preoperative venous analysis for neurosurgeons and neuroradiologists.

Integrated LCC-LCC Topology for WPT System With CC Output Regarding Air Gap and Load Variations

Integrated LCC-LCC Topology for WPT System With CC Output Regarding Air Gap and Load Variations

Neural networks for ID gap orbit distortion compensation in PETRA III

Undulators are used in storage rings to produce extremely brilliant synchrotron radiation. In the ideal case, a perfectly tuned undulator always has a first and second field integrals equal to zero. But, in practice, field integral changes during gap movements can never be avoided for real-life devices. As they significantly impact the circulating electron beam, there is the need to routinely compensate such effects. Deep Neural Networks can be used to predict the distortion in the closed orbit induced by the undulator gap variations on the circulating electron beam. In this contribution several state-of-the-art deep learning algorithms were trained on measurements from PETRA III. The different architecture performances are then compared to identify the best model for the gap-induced distortion compensation. It is found that realistic data, with several gaps moving simultaneously to arbitrary gaps must be used to train the neural networks. The deep feed-forward neural network was found to be more effective than the recurrent and convolutional neural networks.