Small Cross Section Research Articles

Rate coefficients for rotational state-to-state transitions in H2O + H2O collisions for cometary and planetary applications, as predicted by mixed quantum-classical theory

Aims. We present new calculations of collision cross sections for state-to-state transitions between the rotational states in an H2O + H2O system, which are used to generate a new database of collisional rate coefficients for cometary and planetary applications. Methods. Calculations were carried out using a mixed quantum-classical theory approach that is implemented in the code MQCT. The large basis set of rotational states used in these calculations permits us to predict thermally averaged cross sections for 441 transitions in para- and ortho-H2O in a broad range of temperatures. Results. It is found that all state-to-state transitions in the H2O + H2O system split into two well-defined groups, one with higher cross-section values and lower energy transfer, which corresponds to the dipole-dipole driven processes. The other group has smaller cross sections and higher energy transfer, driven by higher-order interaction terms. We present a detailed analysis of the theoretical error bars, and we symmetrized the state-to-state transition matrixes to ensure that excitation and quenching processes for each transition satisfy the principle of microscopic reversibility. We also compare our results with other data available from the literature for H2O + H2O collisions.

Enhanced Thomson scattering x-ray sources with flying focus laser pulse

X-ray source based on the Thomson scattering of laser interacting with energetic electron beams features high photon energy, small spot size, and good collimation. However, the photon number is insufficient for practical application because of the small cross section of the Thomson scattering. To solve this problem, here, we replace a traditional Gaussian laser pulse with a flying focus laser pulse to extend interaction length and restrain nonlinear effects. Simulation results show that the scattered photon number can be increased by about 25 and 2 times for high and low energy lasers, respectively. In particular, a 1010 photon number can be generated with a 10 J flying focus laser pulse, and the energy spread can also be greatly reduced for high energy laser, from a broad spectrum to a monoenergetic peak. Combining these two advantages, the peak spectrum brightness of x ray is 3 × 108 photons/keV at 240 keV, which is about three orders of magnitude more than the traditional case.

Vibration and resonance reliability analysis of non-uniform beam with randomly varying boundary conditions based on Kriging model

In order to prevent the function failure of the structure due to resonance in the working process. The vibration responses and resonance reliability of non-uniform beam (NUB) with randomly varying boundary conditions (RVBCs) are investigated in this paper. The natural frequencies calculated by Adomian decomposition method (ADM) are used to establish the sample space, based on which the Kriging model is obtained through learning. The influences of boundary support spring stiffness (BSSS) and taper ratio on natural frequencies, vibration responses, and resonance reliability are then studied. The numerical results show that within the range of studied parameters, when the BSSS of the NUB change simultaneously during vibration, the influences and trends of the BSSS on each order’s natural frequency are different and challenging to predict. Due to the geometric nonuniformity of the NUB, the influence of the spring at the left end with a smaller cross-section on the resonance failure probability is more significant than that on the other side. With the increase in taper ratio, the amplitude, maximum strain, and resonance failure probability increase first and then decrease. The method can also be used to solve the vibration characteristics and resonance reliability of NUBs with randomly varying elastic modulus, density and dimensions, which can provide a reference for the data monitoring and use maintenance of the non-uniform beam in vibration.

Feasibility Studies for the Measurement of Open-Charm Mesons at ALICE-3 Using Decay Channels with Neutral Mesons and Photons in the Final State

ALICE-3 is being designed as a next-generation heavy-ion experiment to be operated at the high-luminosity Large Hadron Collider. With luminosities higher by a factor of fifty, ALICE-3 will be able to study5 properties of quark–gluon matter with probes and precision which were previously unavailable due to small cross sections, high background levels, and insufficient detector sensitivity. In particular, the properties of hot and dense QCD matter will be studied by measuring production cross sections, flow coefficients, azimuthal angular correlations and nuclear modification factors for open-charm hadrons. In this contribution, we present the results of feasibility studies for the measurement of ground and excited states of open-charm mesons in decay channels D0 → K− + π+ + π0, D*(2007)0 → D0 + γ and D*(2010)± → D0 + π± in pp, p-Pb and Pb-Pb collisions at LHC energies using the ALICE-3 experimental setup. We formulate the main requirements for the selection of particles and their combinations to ensure reliable signal extraction in a wide transverse momentum range and estimate the minimum size of the required data samples. The results obtained are also compared to previous findings for the open-charm measurements in different decay channels.

Orbital evolution of satellite galaxies in self-interacting dark matter models

Dark matter self-interactions can leave distinctive signatures on the properties of satellite galaxies around Milky Way--like hosts through their impact on tidal stripping, ram pressure, and gravothermal collapse. We delineate the regions of self-interacting dark matter parameter space---specified by interaction cross section and a velocity scale---where each of these effects dominates and show how the relative mass loss depends on the satellite's initial mass, density profile, and orbit. We obtain novel, conservative constraints in this parameter space using Milky Way satellite galaxies with notably high central densities and small pericenter distances. Our results for self-interacting dark matter models, in combination with constraints from clusters of galaxies, favor either velocity-dependent cross sections that lead to gravothermal core collapse in the densest satellites or small cross sections which more closely resemble cold and collisionless dark matter.

Integrating Bio-Sensing Array with Blood Plasma Separation on a Centrifugal Platform.

Numerous immunoassays have been successfully integrated on disc-based centrifugal platforms (CDs) over the last 20 years. These CD devices can be used as portable point-of-care (POC) platforms with sample-to-answer capabilities where bodily fluids such as whole blood can be used as samples directly without pre-processing. In order to use whole blood as a sample on CDs, centrifugation is used to separate red blood cells from plasma on CDs. There are several techniques for using specific fluidic patterns in the centrifugal fluidic network, such as reciprocation, that enhances the sensitivity of the immunoassays, including those using microarray antigen membranes. Present work demonstrates, for the first time, simultaneous integration of blood plasma separation (BPS) and reciprocation on the CD platform. The integrated design allows plasma that is separated from the red blood cells in a sedimentation chamber to flow into the reciprocation chamber via a narrow connecting channel of 0.5 mm × 0.5 mm cross-section. Due to the small cross-section of the connecting channel, there is no inflow of the red blood cell into the reciprocation chamber during subsequent fluidic operations of the CD. While no inflow of the red blood cells into the reciprocation chamber was observed, the conditions of 20 g jerk acceleration were also simulated in ANSYS finite element analysis software, and it was found that the CD design that was used is capable of retaining red blood cells in the sedimentation chamber. Experimentally, the isolation of red blood cells in the sedimentation chamber was confirmed using the ImageJ image processor to detect the visible color-based separation of the plasma from the blood. A fluorescent analyte testing on the bio-sensing array of the presented novel integrated design and on the standard reciprocation design CD was conducted for 7 min of reciprocation in each case. The test analyte was Europium Streptavidin Polystyrene analyte (10-3 mg/mL) and the microarray consisted of Biotin bovine serum albumin (BSA) dots. The fluorescent signals for the standard and integrated designs were nearly identical (within the margin of error) for the first several minutes of reciprocation, but the fluorescent signal for the integrated design was significantly higher when the reciprocation time was increased to 7 min.

Model Test Study on the Load-bearing Behaviour of Multi-tooth Piles under Different Bearing Layers

In soft soil or karst areas, several problems exist, such as the poor properties of the pile tip bearing layer or difficulties in cutting the rock. Using multi-tooth piles, end-bearing piles can be turned into friction piles to solve these problems. Through the scale model device, three variables: the bearing layer, tooth length, and tooth number, are designed to experimentally explore the load-bearing behaviour of multi-tooth piles under different bearing layer conditions. The test results show that the model pile has better anti-settlement performance in the sand bearing layer than in the red clay bearing layer. Compared with smooth piles, multi-tooth piles can greatly improve the bearing capacity of pile foundations in bearing layers with poor stiffness. The tooth length and tooth number greatly impact the compressive bearing capacity and the pile-side resistance of the multi-tooth pile, respectively. The concept of roughness is innovatively introduced to quantify the roughness of pile surfaces, which provides an effective method for the subsequent experimental and theoretical research of multi-tooth piles and other similar piles with small cross-section modifications. This study can enrich the research field of small, modified cross-section piles and provide a reference for innovative research on pile foundations.

Dissociation Dynamics of Anionic Nitrogen Dioxide in the Low-Lying Resonant States.

Experimental studies of the dynamics near the molecular dissociation threshold are frequently frustrated, due to the small cross sections and the demand for identification of close-lying electronic states or nuclear motions with multiple degrees of freedom. Using the high-resolution anion velocity map imaging technique, here we report a dynamics study of the dissociations of anionic nitrogen dioxide in low-lying resonant states formed by electron attachment [e- + NO2 (X2A1) → NO2- → NO (X2Π) + O- (2P)]. The long-term puzzling issues about the near-threshold dissociations of NO2- are settled. We suggest that three low-lying resonant states (1B1, 3B1, and 3B2) of NO2- contribute to the production of O- at attachment energies of <5 eV. Furthermore, B1 and B2 symmetries of the resonant states lead to different anisotropies of the O- angular distribution. At the relatively high electron attachment energies, a prompt fragmentation in the molecular bent conformation competes with an indirect dissociation in the straightened conformation.

Fabrication of an Ag-based SERS nanotag for histamine quantitative detection

A crucial issue in analytical science and physiology is the detection of histamine with high sensitivity, specificity and credibility, which served as an important neurotransmitter in biofluids. Despite the high sensitivity of surface-enhanced Raman spectroscopy (SERS) at the level of single molecule, there are still challenges in providing high sensitivity for histamine with a small cross section. For the selective detection of histamine using SERS, a highly sensitive sandwich structure substrate combining Fe3O4 and an Ag-based SERS nanotag was developed. The Fe3O4@SiO2–COOH served as a capture component for enriching histamine. Upon functionalized Ag nanoparticles with glycine (Gly) and (3-Aminopheyonyl) boronic acid (APBA), they were then used to connect with histamine and serve as a SERS nanotag, respectively. A linear relationship between the Raman intensity and the histamine concentration was observed over the range 10−4-10−8 M with a limit of detection of 7.24 × 10−9 M. This methodology also exhibited good selectivity in the presence of other neurotransmitters. With our new approach, histamine can be detected sensitively and reliably in fish samples, which indicates the potential prospect of an effective method for analyzing histamine in complex specimens.

Small Fixed-Wing UAV Radar Cross-Section Signature Investigation and Detection and Classification of Distance Estimation Using Realistic Parameters of a Commercial Anti-Drone System

Various types of small drones constitute a modern threat for infrastructure and hardware, as well as for humans; thus, special-purpose radar has been developed in the last years in order to identify such drones. When studying the radar signatures, we observed that the majority of the scientific studies refer to multirotor aerial vehicles; there is a significant gap regarding small, fixed-wing Unmanned Aerial Vehicles (UAVs). Driven by the security principle, we conducted a series of Radar Cross Section (RCS) simulations on the Euclid fixed-wing UAV, which has a wingspan of 2 m and is being developed by our University. The purpose of this study is to partially fill the gap that exists regarding the RCS signatures and identification distances of fixed-wing UAVs of the same wingspan as the Euclid. The software used for the simulations was POFACETS (v.4.1). Two different scenarios were carried out. In scenario A, the RCS of the Euclid fixed-wing UAV, with a 2 m wingspan, was analytically studied. Robin radar systems’ Elvira Anti Drone System is the simulated radar, operating at 8.7 to 9.65 GHz; θ angle is set at 85° for this scenario. Scenario B studies the Euclid RCS within the broader 3 to 16 Ghz spectrum at the same θ = 85° angle. The results indicated that the Euclid UAV presents a mean RCS value (σ ¯) of −17.62 dBsm for scenario A, and a mean RCS value (σ ¯) of −22.77 dBsm for scenario B. These values are much smaller than the values of a typical commercial quadcopter, such as DJI Inspire 1, which presents −9.75 dBsm and −13.92 dBsm for the same exact scenarios, respectively. As calculated in the study, the Euclid UAV can penetrate up to a distance of 1784 m close to the Elvira Anti Drone System, while the DJI Inspire 1 will be detected at 2768 m. This finding is of great importance, as the obviously larger fixed-wing Euclid UAV will be detected about one kilometer closer to the anti-drone system.

UAV Propeller Rotational Speed Measurement through FMCW Radars

The growing number of civil applications in which Unmanned Aerial Vehicles (UAVs) are involved can create many concerns for airspace security and surveillance. Gathering as much information as possible about a drone can be crucial to apply proper countermeasures if a potentially dangerous situation is detected. Of course, the presence of a UAV can be detected by radar, but it is possible to extend the system capabilities to obtain additional information. For example, in the case in which the UAV is equipped with propellers, the radar-measured rotational speed could be important information to classify the type of UAV or to reveal if it is carrying some possibly harmful payload. In addition, the rotational speed measured through radar could be used for different purposes, such as to detect a drone manumission, to estimate its maximum payload, or for predictive maintenance of the drone. Measuring the propellers’ rotational speed with radar systems is a critical task, as the Doppler generated by the rotation can be very high, and it is very difficult to find commercial radar systems in the market able to handle such a high Doppler. Another problem is caused by the typically very small Radar Cross-Section (RCS) of the propellers, which makes their detection even more difficult. In the literature, common detection techniques are based on the measurement of the Doppler effect produced by the propellers to derive their rotational speed, but due to the very limited capabilities of commercial sensors, this approach can be applied only at very low values of the rotational speed. In this work, a different approach based on a Frequency-Modulated Continuous Wave (FMCW) radar is proposed, which exploits the vibration of the UAV generated by the rotation of the propellers. The phenomenon and how the sensor can detect it will be presented, which is joined with a performance analysis comparing different estimation techniques for the indirect measurement of the propellers’ speed to evaluate the potential benefits of the proposed approach.

A segmented total energy detector (sTED) for (n, γ) cross section measurements at n_TOF EAR2

The neutron time-of-flight facility n_TOF is characterised by its high instantaneous neutron intensity, high-resolution and broad neutron energy spectra, specially conceived for neutron-induced reaction cross section measurements. Two Time-Of-Flight (TOF) experimental areas are available at the facility: experimental area 1 (EAR1), located at the end of the 185 m horizontal flight path from the spallation target, and experimental area 2 (EAR2), placed at 20 m from the target in the vertical direction. The neutron fluence in EAR2 is ˜ 300 times more intense than in EAR1 in the relevant time-of-flight window. EAR2 was designed to carry out challenging cross-section measurements with low mass samples (approximately 1 mg), reactions with small cross-sections or/and highly radioactive samples. The high instantaneous fluence of EAR2 results in high counting rates that challenge the existing capture systems. Therefore, the sTED detector has been designed to mitigate these effects. In 2021, a dedicated campaign was done validating the performance of the detector up to at least 300 keV neutron energy. After this campaign, the detector has been used to perform various capture cross section measurements at n_TOF EAR2.

Distribution of the temperature field in the rod, taking into account the correction for heat loss through its side surface

The article deals with heat transfer through a rod with a small cross-section. The rod is assumed to be so thin that the temperature at all points of its cross-section can be considered the same. When finding a solution, the power series decomposition method is used. Formulas were derived not only for finding the temperature field, taking into account the correction for heat loss through the lateral surface of the rod, but also for determining the coefficient of external heat transfer and the coefficient of thermal conductivity from known values of temperatures and heat flows at its ends.

Fast Dual Trifeature-Based Detection of Small Targets in Sea Clutter by Using Median Normalized Doppler Amplitude Spectra

High-resolution sea-surface surveillance radars are designed to find two classes of small targets, low-velocity and floating small targets on the sea surface and low-altitude small targets over the sea surface. Existing feature-based detectors using amplitude and Doppler spectra features of returns can fast detect the first class of small targets. But they often fail to find the second class of small targets due to their small radar cross sections and low signal-to-clutter ratios (SCR). This paper proposes a fast dual tri-feature-based detector to find the two classes of small targets. At the low-velocity tri-feature-based detector, the existing tri-feature-based detector is used to find the first class of small targets. At the high-velocity tri-feature-based detector, a new tri-feature-based detector is used to detect the second class of small targets by utilizing three new features from the median normalized Doppler amplitude spectra (MNDAS). Owing to the ability of the MNDAS to suppress sea clutter, the high-velocity tri-feature-based detector can effectively find the second class of small targets with low SCRs. The detected results in the two tri-feature-based detectors are combined into the binary output of the detector in terms of the ‘OR’ operation. Finally, the proposed detector is verified and compared with the existing detectors by the open and recognized IPIX and CSIR radar databases and one unmanned aerial vehicle radar dataset. Besides the detection performance for the two classes of small targets, a merit of the proposed detector is of low-complexity decision because no time-frequency features are available in detection.

Achieving two-photon fluorescence bioimaging and photodynamic therapy for D–A conjugated polymers through manipulating twisted intramolecular charge transfer

Two-photon fluorescence bioimaging holds immense promise for deep tissue imaging.

Improvement of functional and technological solutions for modernization of steel heating in the tundish of continuous casting machine

The using of the system of plasma heating of metal directly in the tundish is quite promising in terms of improving the technology of continuous casting of steel. At the same time, the efficiency of this technology is significantly influenced by the design of the tundish, the location of the plasmatron, the direction of movement of the circulation flows and their speed, the presence of forced mixing of the liquid metal bath, etc. In terms of design, the main technical solutions proposed for plasma heating of steel in a ladle are based on the creation of two-chamber tundish. Moreover, steel is heated in a special receiving chamber. Such heating devices are compact enough to be built into tundish without any significant modifications. Moreover, such heating devices practically do not reduce the useful volume of the tundish. The widespread use of the technology of plasma heating of metal in the tundish of the continuous casting machine (CCM) at a few metallurgical plants in the world is due to the need to increase the stability of the parameters of the casting process and improve the quality of the workpiece while simultaneously reducing specific energy costs. At the same time, additional prerequisites are created for the transformation of the tundish into a multifunctional unit for adjusting the steel temperature and the possibility of its refining. The using of plasma heating in the tundish is especially relevant in the conditions of mini-mills operating technological units of small capacity, for which the implementation of traditional highly efficient solutions for out-of-furnace processing, as well as processing on tundish-furnace units, is not always possible due to the complexity of organizing the heating process, large heat losses and high specific costs of refractories. In addition, such tundish can be quite effective when pouring high-quality grades of steel into billets of small cross-sections, which are produced, as a rule, in relatively small mixer-batches, which makes it difficult to prove them in small steel pouring ladles.

Helical vortices with small cross-section for 3D incompressible Euler equation

In this article, we construct traveling-rotating helical vortices with small cross-section to the 3D incompressible Euler equations in an infinite pipe, which tend asymptotically to singular helical vortex filament evolved by the binormal curvature flow. The construction is based on studying a general semilinear elliptic problem in divergence form{−ε2div(K(x)∇u)=(u−q|ln⁡ε|)+p,x∈Ω,u=0,x∈∂Ω, for small values of ε. Helical vortex solutions concentrating near several helical filaments with polygonal symmetry are also constructed.

A flexible neural implant with ultrathin substrate for low-invasive brain–computer interface applications

Implantable brain–computer interface (BCI) devices are an effective tool to decipher fundamental brain mechanisms and treat neural diseases. However, traditional neural implants with rigid or bulky cross-sections cause trauma and decrease the quality of the neuronal signal. Here, we propose a MEMS-fabricated flexible interface device for BCI applications. The microdevice with a thin film substrate can be readily reduced to submicron scale for low-invasive implantation. An elaborate silicon shuttle with an improved structure is designed to reliably implant the flexible device into brain tissue. The flexible substrate is temporarily bonded to the silicon shuttle by polyethylene glycol. On the flexible substrate, eight electrodes with different diameters are distributed evenly for local field potential and neural spike recording, both of which are modified by Pt-black to enhance the charge storage capacity and reduce the impedance. The mechanical and electrochemical characteristics of this interface were investigated in vitro. In vivo, the small cross-section of the device promises reduced trauma, and the neuronal signals can still be recorded one month after implantation, demonstrating the promise of this kind of flexible BCI device as a low-invasive tool for brain–computer communication.

Using the nonlinear Breit-Wheeler process to test nonlinear vacuum birefringence

Quantum electrodynamics predicts that the quantum vacuum is birefringent, but due to the very small cross-section this is yet to be confirmed by experiment. Vacuum birefringence arises as the elastic part of photon-photon scattering; the inelastic part is Breit-Wheeler pair production. We outline how measurements of the photon-polarized nonlinear Breit-Wheeler process can be used to infer a measurement of all-order, nonlinear vacuum birefringence. As an example scenario, we calculate the accuracy of such a measurement for parameters anticipated at upcoming laser-particle experiments.

BARRIERS TO VACCINE UPTAKE IDENTIFIED BY COMMUNITY-BASED ORGANIZATIONS FOR INSITUTIONALLY UNDERSERVED GROUPS

Abstract Through a competitive proposal process for a recent funding opportunity, 38 community based organizations submitted proposals that addressed vaccine hesitancy among adults who are members of racial or ethnic minority communities. Proposals were required to include discussion of barriers identified in the community of focus and evidence to support all assertions. Submissions ranged from single employee projects to large collaborative networks, and were submitted from all regions of the US, including both tribal and territorial areas, including more than 45 ethnic and language groups. Barriers were coded by two reviewers and six (6) primary themes were identified: access related to transportation, distance, or time; lack of culturally responsive materials or sensitivity of providers; structural issues such as poor data collection, historical inequity, mistrust, or systemic racism; messages coming from untrusted sources; misinformation or no information available; and differing cultural perspectives. The most commonly identified issues were related to mistrust, historical structural issues or fear and racism (n=23), and lack of access due to transportation, distance, or time (n=17). This group of proposals for funding represent a small cross-section of communities who continue to have significant pockets of unvaccinated persons. While it is possible to see themes for barriers that are encountered in increasing vaccination rates among adults, communities demonstrate extremely nuanced realities, filtered through a range of culturally and paradigmatically different ways of knowing. Success in public health initiatives requires intensive focus on the variance across these different perspectives and careful attention to appropriately focus outreach and messaging.