bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective Length Factors for Gusset Plate Buckling
Authors: Dowswell Bo
Published: April 2024

Gusset plates are commonly used in steel buildings to connect bracing members to other structural members in the lateral force resisting system. Failure modes for gusset plates have been identified, and design procedures are well documented in the literature, but uncertainties still exist for gusset plates in compression. The previous research includes laboratory tests, finite element models, and theoretical studies. Many of the previous studies concentrated on the capacity of gusset plates in compression. A literature review revealed a total of 170 experimental specimens and finite element models with compressive loads applied. The procedures that are currently used to design gusset plates are reviewed. Using the experimental and finite element data from the previous studies, the capacity of gusset plates in compression are compared to the current design procedures. Based on a statistical analysis, effective length factors are proposed for use with the current design procedures.
Cold Bending of Wide-Flange Shapes for Construction
Authors: Bjorhovde Reidar
Published: April 2024

In addition to complete structures such as arches, curved structural members are also used extensively in construction. Some of the individual members are curved about the strong axis of the shapes; others are curved about the weak axis. Common to the examples presented and to most building applications is the fact that the curving of such members is mostly done at ambient temperature. Such cold bending places greater demands on the curving equipment that is used, to the effect that larger curving forces are needed. Higher temperature curving is certainly feasible for many applications, and a number of bending companies use it on a regular basis. It is almost always used when straightening repair of bridge girders is needed. For practical reasons the material that is presented focuses on applications of bent structural members for building-type structures. Bridge structures rarely use members that are curved as much as those described, and therefore, fatigue and similar considerations are not addressed.
The Analyses of Extended Shear Tab Steel Connections Part I: The Unstiffened Connections
Authors: Rahman Adeeb , Mahamid Mustafa , Amro Akef , Ghorbanpoor Al
Published: April 2024

The objective of this paper is to develop a viable, comprehensive 3-D finite element model capable of predicting the nonlinear behavior of unstiffened extended shear tab connections building on the experimental investigations of Sherman and Ghorbanpoor. In order to overcome the limitations and the extensive and expensive demands required by the experimental investigation, the development of a computational model to validate and expand on the experimental results is merited and presents a powerful tool in examining the actual structural behavior. It presents the opportunity for the analyst and the designer to investigate full field results output for all the structural members. The model allows the examination of a wide range of connection types, configurations, materials, and loadings. The paper also identifies and presents important relevant parameters that are crucial in making the finite element (FE) analysis possible. The FE model is intended to validate the existing experimental results and to predict the behavior of deeper connections without the need for further expensive experiments. This model presents a viable modeling procedure to effectively account for contact behavior, bolt tensioning and nonlinearity. Analysis of surfaces in contact requires special numerical techniques due to the inherent nonlinearity. Parameters such as coefficient of friction, bolt pre-tensioning, and surface stiffness must be considered to achieve proper contact between the surfaces. In this paper two 3-D FE models, having 3-bolt and 5-bolt unstiffened extended shear tab connections are constructed. The 3-bolt connection failed primarily in column web mechanism failure mode with bolt shear and twist of the shear tab as secondary failure modes. However, the 5-bolt connection failed primarily in twisting of the shear tab, while column web mechanism and bolt shear were the secondary failure modes. The web mechanism failure mode is due to the punching of the shear tab into the web of the column, resulting in high plastic strains and permanent deformation in the web.
Direct Analysis and Design Using Amplified First-Order Analysis Part I: Combined Braced and Gravity Framing Systems
Authors: White Donald W. , Surovek Andrea , Kim Sang-Cheol
Published: April 2024

In 1976 and 1977, LeMessurier published two landmark papers on practical methods of calculating second-order effects in frame structures. LeMessurier addressed the proper calculation of second-order displacements and internal forces in general rectangular framing systems based on first-order elastic analysis. He also addressed the calculation of column buckling loads or effective length factors using the results from first-order analysis. The 2005 AISC Specification provides a new method of analysis and design, termed the Direct Analysis Method (or the DM). The DM involves the use of a second-order elastic analysis that includes a nominally reduced stiffness and an initial out-of-plumbness of the structure. The 1999 AISC LRFD and the 2005 AISC Specifications permit this type of analysis as a fundamental alternative to their base provisions for design of stability bracing. In fact, the base 1999 AISC Specification and the 2005 AISC Specification stability bracing requirements are obtained from this type of analysis. This paper demonstrates how a form of LeMessurier's simplified second-order analysis equations can be combined with the 2005 AISC Specification DM to achieve a particularly powerful analysis-design procedure.
Performance-Based Plastic Design of Special Truss Moment Frames
Authors: Chao Shih-Ho , Goel Subhash C.
Published: April 2024

This paper presents the results of a study in which a recently developed performance-based plastic design (PBPD) methodology was used to design the special truss moment frame (STMF) system rather than conventional elastic method. This newly developed performance-based method has been successfully applied to moment frames and also extended to eccentrically braced frames, buckling-restrained braced frames, and concentrically braced frames. The procedure begins by selecting a desired yield mechanism for the frame. Design base shear and lateral forces are determined from input spectral energy for a given hazard level needed to monotonically push the structure in the yielded state up to a pre-selected target drift. The frame members are then designed by following the plastic design method in order to develop the needed strength and the intended yield mechanism. A new seismic design lateral force distribution based on nonlinear dynamic behavior is also presented. The proposed design procedure was validated by extensive nonlinear dynamic analyses for a number of ground motion records. The results confirm the validity of the proposed method for the study STMFs in terms of meeting all the performance design objectives, such as target drifts and intended yield mechanism. An important advantage of the PBPD method is that, generally, no nonlinear analysis is needed to check the structural performance after the initial design.
A Modified Equation for Expected Maximum Shear Strength of the Special Segment for Design of Special Truss Moment Frames
Authors: Chao Shih-Ho , Goel Subhash C.
Published: April 2024

Special truss moment frame (STMF) is a relatively new type of steel structural system that was developed for resisting forces and deformations induced by severe earthquake ground motions. The system dissipates earthquake energy through ductile special segments located near the mid-span of the truss girders. The other elements outside the special segments, such as truss members, girder-to-column connections, and columns, are designed based on the expected vertical shear strength (Vne) of the special segment and are expected to remain elastic during a major earthquake. As a consequence, overestimation of in the special segment can result in significant over-design of the elements outside the special segment. This study shows that the equation for expected shear strength in the current AISC Seismic Provisions can be quite conservative, thereby leading to considerable over-design of members outside the special segment. Based on more realistic assumptions, a modified expression for is proposed in this paper, which results in a better estimation of the expected shear strength while maintaining an adequate safety margin. The proposed expression was validated by using previous experimental results as well as nonlinear static and dynamic analyses (to determine the seismic demand in the special segment). A design equation of for STMF using multiple Vierendeel panels in the special segment is also proposed.
Design and Behavior of Multi-Orientation Fillet Weld Connections
Authors: Callele Logan J. , Driver Robert G. , Grondin Gilbert Y.
Published: April 2024

Several independent research projects have demonstrated that the strength and ductility of fillet welds are a function of the angle between the weld axis and the line of action of the applied load. It has been demonstrated that transverse welds are about 50% stronger than longitudinal welds, but have considerably lower ductility. This difference in behavior can have a significant impact on the design of welded connections with multiple weld orientations within the same joint. Tests on concentrically loaded welded double lapped joints have recently been conducted to investigate the strength of connections with multiple weld segments of different orientations. The tests indicate that these joints possess capacities significantly lower than the sum of the individual weld segment strengths. The tested connections' capacities are a function of the interaction of the load versus deformation characteristics of the individual weld segments. A general approach for the design of welded joints that combine welds in various directions that reflects the individual segments' load versus deformation interaction is recommended.
A Strength Design Approach to Ponding
Authors: Silver Edward
Published: April 2024

This article proposes a strength design approach to ponding resistance. It derives methods to include camber, nonuniform loading, and end fixity. The intent is to expand on the existing American Institute of Steel Construction (AISC) provisions so they may be adapted to unique framing and loading conditions.
Discussion: Critical Evaluation of Equivalent Moment Factor Procedures for Laterally Unsupported Beams
Authors: Wilkerson Steven
Published: April 2024

Discussion
Fillet Weld Design for Rectangular HSS Connections
Authors: Packer Jeffrey A. , Sun Min
Published: April 2024

The 2010 AISC Specification for Structural Steel Buildings has expanded the scope in Chapter K ("Design of HSS and Box Member Connections"�) with a new Section K4, "Welds to Branches."� This paper describes the background to this development and examines the structural reliability of the weld effective length provisions contained therein. The latter is achieved by using a database of 31 welded square/rectangular hollow structural section (HSS) K-, T- and cross- (or X-) connections in which all test specimen failures were reached by fracture of the welded joints. The potential inclusion (or exclusion) of the sin θ effect, whereby fillet weld capacity is increased for loading not parallel to the axis of the weld, has also been investigated. In conclusion, some design examples are given to illustrate the weld design method, performed to the 2010 AISC Specification in both LRFD and ASD.
Stability Design of Cross-Bracing Systems for Frames
Authors: Eric M. Lui and Xiaoran Zhang
Published: April 2024

In this study, the inelastic load-carrying capacity of the compression diagonal of a typical cross-bracing system used in concentrically braced frames under gravity and wind loads is investigated, taking into consideration its interaction effect with the tension diagonal. Depending on the lateral stiffness of the tension diagonal, the compression diagonal can be fully or partially braced by the tension diagonal at their intersection point. An expression for the transition lateral stiffness, kst, that demarcates the fully and partially braced conditions is derived. When the compression diagonal is fully braced, its maximum load-carrying capacity is a function of its member slenderness, L/r, only. However, when the compression diagonal is partially braced, its load capacity is dependent upon both its member slenderness, L/r, and the lateral stiffness, ks, of the tension diagonal. Once the equations for the maximum load-carrying capacity of the compression diagonal are established, design guidelines are proposed and design examples are given to demonstrate how the proposed guidelines can be used for the design of cross-bracing systems in steel frames. The consideration of the lateral bracing effect will result in a more economical and logical design for such bracing systems.
Steel Structures Research Update: System Behavior and Collapse Assessment of Braced Frames
Authors: Liu Judy
Published: April 2024

Current and recently completed research on system behavior and collapse assessment of braced frames is presented. The research includes work on concentrically braced frames, buckling restrained braced frames, and dual systems with braced frames and secondary moment frames.
Steel Structures Research: Design for Deconstruction with Demountable
Composite Beams and Floor Systems
Authors: Liu Judy
Published: April 2024

Ongoing and recently completed research on deconstructable steel-concrete composite beams and floor systems for
steel frame buildings is presented. This research includes demountable beam-slab connectors, deconstructable composite
floor systems with precast concrete planks, and lightweight modular two-way steel flooring systems.
The Chevron Effect and Analysis of Chevron Beams—A Paradigm Shift
Authors: Fortney Patrick J. , Thornton William A.
Published: April 2024

Beam designers and connection designers have a different standard of care in the analysis of beams in inverted V- and V-type braced frames subjected to lateral loads. When the summation of the vertical components of the brace forces is nonzero, (1) beam designers evaluate required beam shear and moment, treating the unbalanced vertical load as a concentrated force acting at the work point of the braces while ignoring any local effects resulting from the brace connection geometry, and (2) the connection designer evaluates the required beam shear based only on the moment acting at the gusset-to-beam interface(s). Thus, the beam designer considers beam span and work point location ignoring the local effect of the connection, and the connection designer considers the local effects of the connection while ignoring beam span and the location of the work point. This paper proposes a new method for evaluating required beam shear and moment that includes consideration of beam span, location of work point, and the local effects of the connection—a method that can be used by both the beam designer and the connection designer. Discussion is also provided to illustrate how this proposed method can be used to evaluate whether or not the local connection effect dominates the global effect. It is shown that the magnitude of the unbalanced vertical load influences the impact of the local connection effects; when the summation of the vertical brace force components is zero or relatively small, the local connection effects dominate the global effect. Conversely, when the unbalanced vertical load is relatively large, the global effects dominate; in this case, including the local connection effects will predict a smaller required beam moment possibly allowing for lighter beams.
Nonlinear Behavior and Design of Mid- to High-Rise Diagrid Structures in Seismic Regions
Authors: Asadi Esmaeel , Adeli Hojjat
Published: April 2024

The aesthetics and structural advantages of the diagrid structural system have made it an attractive choice for many buildings across the world, including several notable high-rise building structures built in recent years. This paper presents an investigation of nonlinear behavior and design of mid- to high-rise steel diagrid structures. Weight, story drift, fundamental period, lateral stiffness, and sequence of plastic hinge formation in steel diagrids are studied and compared with corresponding moment-resisting frames and concentrically braced frames. To improve the nonlinear behavior and increase the collapse load capacity of diagrid structures in high seismic regions, practical design guidelines are proposed by using virtual work/energy diagrams and by performing nonlinear static analysis. So far, the diagrid system has been used mostly in the design of tall buildings in the range of 20 to 100 stories. A conclusion of this research is that the diagrid system can also be an efficient and economical structural system for mid-rise buildings in the 8- to 15-story range.
Experimental Investigation of a Steel-Framed Building for Disproportionate Collapse
Authors: Akah Ebiji , Wood Curtis , Li Kai , Sezen Halil
Published: April 2024

This paper presents the experimental and numerical investigation of the progressive collapse vulnerability of an existing steel building, Haskett Hall, on the Ohio State University campus. The building was tested by removing one of the first-story columns to observe its collapse resistance and to evaluate the effectiveness of current modeling and analysis guidelines. Progressive collapse is a relatively large partial or complete collapse of a structure due to the loss of a vertical load-carrying element—a column in this case. Few researchers have been able to conduct full-scale experiments to understand the progressive collapse mechanism. In this research, deflections and deformations of steel structural components were measured during the field experiment. Computational models and simulations were examined and compared with the experimental data from the field tests. The contribution and effects of infill walls to progressive collapse resistance of frame structures were investigated. The test data collected in this research can be used to help develop recommendations for improved procedures for progressive collapse analysis of frame buildings.
Critical Temperature of Axially Loaded Steel Members with Wide-Flange Shapes Exposed to Fire
Authors: Sauca Ana , Chicchi Rachel , Zhang Chao , Choe Lisa
Published: April 2024

This paper presents closed-form equations that were developed to evaluate critical temperatures of structural steel compression and tension members exposed to fire. The deterministic approach involved a parametric study using finite element simulations in order to identify influencing factors—for example, mechanical properties of steel, member slenderness, and axial load ratios. Statistical models were employed to develop closed-form equations representing the best fit of numerical results. A comparison with experimental column test data indicates that the proposed equation for compression members provides a conservative lower bound (16% lower on average) relative to the test data at load ratios greater than 0.3. A sensitivity study was also performed to further explore uncertainty in predicted critical temperatures due to variability of axial load ratios. For both compression and tension members, the ambient-temperature yield stress of steel, Fy, has a great impact on determination of axial load ratios, subsequently influencing the overall accuracy of the critical temperature estimated by the proposed equations. The applicability of the proposed equations is limited to wide-flange steel members that are simply supported, concentrically loaded, and exposed to uniform heating.
Design of Steel Bearing Plates
Authors: Fling Russell S.
Published: April 2024

Base plates for columns and bearing plates for beams resting on masonry are details associated with the design of all steel structures. Given the load and allowable bearing pressure, the area of the plate is easily computed. From this, the overhanging cantilever span can be determined. If the yield point of the steel is known, the thickness of the plate required can be determined by the procedures outlined on pages 2-44 or 3-75 of the AISC Manual. This solution is time consuming if more than an occasional bearing plate is encountered. Fortunately it can be easily presented in tabular or graphical form. Design procedures presented in the AISC Manual are silent on two important questions. No limit is placed on plate deflections. Column base plates nearly the same size as the column cannot be properly designed by the AISC procedures.
Buckling of Hyperbolic Paraboloids
Authors: Buchert Kenneth P.
Published: April 2024

Large spherical dome roofs are being constructed regularly because of their beauty, adaptability, and low cost. A decade ago this type of roof was rather rare because of the high cost of construction and the significant unknowns in the design. Considerable research and development in design and construction has resulted in analysis procedures that have a high degree of reliability and are carried out at minimum cost (often the dome analysis is much more economical than the analysis of a similar size conventional type structure.) Ingenious fabrication and erection methods have paralleled the analysis development with resulting relatively low final costs. Designs have been carried to completion for roofs up to 850 ft in base diameter (the Astrodome is about 620 ft in base diameter). Preliminary feasibility designs have been made for roofs over one mile in diameter. The buckling analysis is an important part of dome design. Several large domes have failed in the last decade and present methods of buckling analysis have been used to explain the failures. Experience in the field and laboratory has allowed reductions in factors of safety from about 10 to as low as 1.5 with satisfactory results.
Load Factor Design of Steel Buildings
Authors: Galambos Theodore V.
Published: April 2024

Since the early 1950s there have been an increasing number of articles and books in the structural engineering literature on the application of probability and statistics in the design of structures. Since 1965 the rate of development on the subject has increased greatly. A sizeable group of experts and researchers are now working on various facets of the problem. One may be somewhat confused by all these activities, and not quite see where all this is leading. This is not at all surprising, since some of the research is only now reaching fruition and there is much activity which has not yet shaken down with respect to method or terminology. Enough work has been done, however, to justify a look at what is happening and to relate this to the present state of steel design as exemplified by the 1969 AISC Specification. This paper will attempt to give a brief review of the activities, explain some basic ideas, and examine the possibilities of these principles being applied to steel building design. The paper is not written for the experts in probability and statistics; rather, it is addressed to the structural engineer who wants to become familiar with developments on the subject.
A Unified Approach to the Elastic Lateral Buckling of Beams
Authors: Nethercot David A. , Rockey K.C.
Published: April 2024

The lateral buckling of beams is a complicated phenomenon, the maximum elastic bending stress necessary to cause buckling being dependent upon the geometrical and material properties of the beam, the type and position of the loading, and also the support conditions. This paper presents a design procedure which enables all of these factors to be allowed for, in an accurate yet simple and direct manner, for 41 different cases of loading and support. The proposed method is both more accurate and more versatile than existing methods used in design codes.
Abdominal apoplexy in late trimester of pregnancy: Case reports
Authors:   Department of Gynecology and Obstetrics, Shenzhen Hospital of Southern Medical University, Shenzhen, Guangdong, China, CHAI Dan
Published: April 2024

Background: Abdominal apoplexy or Idiopathic Spontaneous Intraperitoneal Hemorrhage (ISIH) is rare and refers to intra-abdominal hemorrhage caused by spontaneous rupture of blood vessels in the abdominal cavity or retroperitoneum. The clinical diagnosis of abdominal apoplexy during pregnancy is rarer, and often made only after emergent exploratory laparotomy is performed for unstable vital signs and severe anemia. Affected by an enlarged uterus during pregnancy, the symptoms and signs of acute abdomen may be confused with placental abruption or other more common complications of pregnancy. Case presentation: Both cases in the study showed that the main symptoms were abdominal pain, hypotension, nausea, vomiting, and other associated blood loss symptoms of varying degrees. Due to its sudden onset, this dangerous condition with no typical symptoms and signs can be easily misdiagnosed, two cases were given urgent surgery finally. At a 12-month follow-up, no abnormalities were observed during medical examinations of both mother and child. Conclusions: The clinical diagnosis of abdominal apoplexy during pregnancy usually needs emergent exploratory laparotomy to find the hemorrhagic spot. We analyzed and summarized two cases of abdominal apoplexy in the late third trimester of pregnancy in and aims to provide certain clinical reference for surgeons when seeing the abnormal sustaining abdominal pain during pregnancy so that adverse pregnancy outcomes can be avoided.
The potential of Polish forests to provide ecosystem services
Authors: Affek Andrzej , Solon Jerzy , Kowalska Anna , Regulska Edyta , Wolski Jacek , Kołaczkowska Ewa
Published: April 2024

Polish forests differ in their potential to provide ecosystem services (ES), but it is unclear how and to what extent. We assessed the potential of 35 forest habitat types to provide 17 key ES and showed that the montane mesic broadleaved forest has a high potential to provide the largest number of key forest services (14 out of 17), which gives it the status of a multi-service hotspot. The highest overall potential was found in the forests of mountain regions, slightly lower in the postglacial northern regions, and the lowest in the central lowland regions.
Characteristics of basic psychological needs of atopic dermatitis and psoriasis patients
Authors:   University of Szeged, Faculty of Arts, Institute of Psychology, Personality-Clinical and Department of Health Psychology, Szeged, Szabó Csanád , Irsai-Mehwert Zsuzsanna , Kemény Lajos
Published: April 2024

The Authors examined the degree of satisfaction and frustration of basic psychological needs (autonomy, competence, relatedness) of dermatology outpatients . The study questionnaire were filled out, by 52 dermatology outpatients(22 patients with atopic dermatitis, 30 patients with psoriasis) in the autumn of 2023. In the two patient’s groups, the highest level of satisfaction was found at relatedness, followed by validation of competence and the fulfillment of the need for autonomy. Correlations were found between characteristics of psychological needs and levels of perceived stress, anxiety and depression. The Authors’ results may provide new perspectives in the field of psychoeducation, counseling, and psychotherapy for dermatology patients.
Health care is at the heart of preparing future social workers for activities to overcome the risks of social adaptation
Authors: Vasyuk Andrei Grigorievich
Published: April 2024

The subject of this article is health care in the activities of social workers to overcome the risks of social adaptation. The object is to prepare future social workers for activities to overcome the risks of social adaptation. Considering the essence of social adaptation of military personnel, the author names the main stages of social adaptation of military personnel, dwells on those that should be formed at the university, believes that at each stage different mechanisms of its formation and development should work. The article reveals the conceptual essence of the risks of adaptation of military personnel. The author argues that the system of training social workers to overcome the risks of social adaptation among combatants should be carried out in specially created conditions for the formation of subjective qualities, psychological relief, group and individual approaches. Health saving, the author emphasizes, health and a healthy lifestyle should become a priority in the education of these students, makes practical recommendations for improving health-saving technologies in education as a basis for preventing adaptation risks.   For the first time, the author shows the role of education in the activities of social workers to overcome the risks of social adaptation among combatants. For the first time, the article addresses the problem and reviews the literature on the topic of training social workers to overcome the risks of social adaptation among combatants. As a result of the analysis of the literature on the research topic, the author concludes that the system of training social workers to overcome the risks of social adaptation among combatants should be aimed at strengthening their health, makes specific proposals to improve the training of social workers to overcome the risks of adaptation in military personnel, names adaptation technologies in the training system of social workers to this type of activity. A special contribution of the author is the actualization of the research topic, conceptual approaches to its study and the conclusion that the development of the health culture of students participating in hostilities is ensured by the practical implementation of the specific conceptual provisions proposed by him.
An enhanced radiation pressure acceleration scheme for accelerating protons using the uniform density plasma channel
Authors: Yang Lu , Wang Xiao-Nan , Chen Xin , Chen Peng-Fan , Xia Qian-Wen , Xiong Li , Long Hao-Yu , Li Lin-Yang , Mao Xiao-Bao , Zhou Hai-Long , Zhang Wei-Wei , Lan Xiao-Fei , He Yang-Fan ,   School of Physics and Astronomy, China West Normal University, Nanchong 637001, China,   Panzhihua No.3 Senior High School, Panzhihua 617099, China
Published: April 2024

High-energy proton beams have broad application prospects in medical imaging, tumor therapy and nuclear fusion physics. Laser plasma acceleration is a new particle acceleration method with great potential because its acceleration gradient can reach 103–106 times that of traditional acceleration method, so it can theoretically accelerate electrons and ions to high energies in the scale of a few centimeters to a few meters. Radiation pressure acceleration (RPA) is considered to be the most promising mechanism of high energy proton acceleration in laser plasma acceleration, but the Rayleigh-Taylor instability (RTI) inherent in the process of radiation pressure acceleration will cause transverse density modulation on the target surface, resulting in the premature termination of the proton acceleration process and the failure to obtain high energy proton beams. In order to obtain high-energy proton beams, an acceleration scheme combining radiation pressure acceleration with laser wakefield is proposed. In this scheme, a high-energy proton beam with peak energy of 22.2 GeV, cut-off energy of 36.4 GeV and charge of 0.67 nC is obtained by adding a uniform density plasma channel at the back end of the thin target with critical density, the cut-off energy of the high energy proton can be increased by two orders of magnitude compared with the proton only in the radiation pressure acceleration process. The results confirm that in a uniform-density plasma channel connected behind a thin target, the laser wakefield can capture protons pre-accelerated by the radiation pressure process and maintain the acceleration for a long period of time, finally obtain high-energy protons. The acceleration of protons in plasma channels with different uniform densities is also investigated in this work, and it is found that the higher the density, the higher the peak energy, cut-off energy and charge of the accelerated protons are. The combined acceleration scheme is instructive for the generation and application of high-energy proton beams.
Flow evolution of mixed layer on convex curvature wall under hypersonic conditions
Authors: Zhang Zhen , Yi Shi-He , Liu Xiao-Lin , Chen Shi-Kang , Zhang Zhen ,   College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: April 2024

With the continuous upgrading of hypersonic vehicles, a new requirement for designing imaging window i.e. conformal window for improving aerodynamic characteristics, is put forward, in which the supersonic cooling film and optical window are required to maintain the same curvature shape as the aircraft body. In this work, the mixed-layer flow evolution on a convex wall (CV) is investigated. A nanoparticle-based planar laser scattering technique is used to design the flow field structure of the mixed layer in Ma = 6 hypersonic static wind tunnel, and the location of the mixed-layer instability is studied by combing fractal dimension. The results of pressure, and impulse of compression (Ip) evolution along the flow direction are obtained by numerical simulation, showing that the total incoming pressure (P0) has a significant effect on the flow evolution of the mixed layer: as P0 increases, the ratio of static pressure (RSP) decreases, that the position of the mixed-layer instability is delayed, and that the flow velocity of the typical vortex structure increases. The favorable gradient existing at the CV wallleads the pressure to drop along the flow direction, and the pressure is enhanced when the supersonic air film along the tangential direction of the wall is under the operating condition. However, as P0 increases, the RSP decreases, and the lifting effect of the pressure on the CV decreases. The flow field is affected by the expansion effect of the CV, and Ip decreases along the flow direction. The supersonic air film can weaken the expansion effect on the CV and thus suppressing the decrease of Ip. The change rate of Ip (ΔIp) is significantly affected by P0, in a range of bending impulse |IΦ| = 0.191–3.62, ΔIp decreases from 178.67% to 12.02% when P0 = 0.5 MPa, and ΔIp decreases from 40.38% to 5.64% when P0 = 1.0 MPa. ΔIp decreases as |IΦ| increases, but the decrease becomes less as P0 increases. The results reveal the flow evolution law of hypersonic mixed layer under the influence of convex curvature, and provide a certain reference for designing the shape of hypersonic vehicle to achieve aerodynamic drag reduction and thermal protection characteristics.
Simulation study of decoherence and light intensity uniformization for extreme ultraviolet of uniform light pipe
Authors: Li Hui , Tan Fang-Rui , Yin Hao-Yu , Ma Yue-Yang , Wu Xiao-Bin ,   R & D Center of Optoelectronic Technology, Institute of Microelectronics of the Chinese Academy of Sciences, Beijing 100029, China,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: April 2024

Free electron laser (FEL) is a high-quality laser source with wavelengths ranging from short-wave X-ray to long-wave infrared ray. Extreme ultra-violet (EUV) radiation at λ = 13.5 nm emitted by FEL can be used in manufacturing integrated circuit, such as EUV lithography exposure and mask defect inspection. However, the high spatial coherence characteristics and similar Gauss intensity profile distribution of FEL source has a negative effect on imaging, and cannot meet the requirements of imaging applications in EUV lithography. In this work, a newly light pipe for decoherence and intensity uniformity in an EUV spectral range is designed through the simulation calculations. The new light pipe consists of two pairs of tilted elements which are symmetrically distributed in the y-z plane and x-z plane, respectively. In this way, the beam transmission divergence in two dimensions can be widened at the same time, and the disturbance of the ray transmission track and spatial phase distribution is increased, so as to achieve the uniformization of light intensity and the reduction of spatial coherence.

The simulation results show that for an EUV Gaussian beam at λ = 13.5nm, with a diameter of 200 μm, and a divergence of 20 mrad, the newly designed light pipe has more significant decoherence and illumination field uniformity than the conventional light pipe structure. When the new light pipe has an inner diameter of 1mm, a total length of not less than 600 mm, and a tilt angle of 10mrad , a basically uniform illumination field can be obtained, the coherence is completely disordered, and the non-uniformity of light intensity distribution in the illumination field decreases to 0.97 from 28.38 achieved by conventional cylindrical light pipe. At the same time, the light power transmission efficiency is about 37.6% and the maximum transmission efficiency is about 44.58%. The uniformity can be further improved by increasing the number of reflections. When the inner diameter and tilted angle of the light pipe are unchanged, the length of the light pipe increases to 1m, the non-uniformity of intensity distribution at the illumination field further decreases to 0.90, and the light power transmission efficiency is about 22.35%. The results show that the newly designed light pipe structure can meet the application requirements of decoherence and improve the uniformity of illumination field at EUV wavelength range, and it has great application prospects in EUV lithography and other imaging applications.
Structural insights in the GTP-driven monomerization and activation of a bacterial LRRK2 homologue using allosteric nanobodies
Authors: Galicia Christian , Guaitoli Giambattista , Fislage Marcus , Gloeckner Christian J. , Versées Wim
Published: April 2024

The Roco proteins are a family of GTPases, characterized by the conserved presence of a Roc-COR tandem domain. These proteins entered the limelight after mutations in human LRRK2 were identified as a major cause of familial Parkinson’s disease. LRRK2 is a large and complex protein combining a GTPase and protein kinase activity, and disease mutations increase the kinase activity, while presumably decreasing the GTPase activity. Although a cross-communication between both catalytic activities has been suggested, the underlying mechanisms and the regulatory role of the GTPase domain remain unknown. Recently, several structures of LRRK2 have been reported, but so far structures of Roco proteins in their activated GTP-bound state are lacking. Here, we use single particle cryo-EM to solve the structure of a simpler bacterial Roco protein (CtRoco) in its GTP-bound state, aided by the use of two conformation-specific nanobodies: Nb
Roco1
and Nb
Roco2
. This structure presents CtRoco in an active monomeric state, featuring very significant conformational changes compared to the previously solved nucleotide-free dimer structure. In particular, the structure shows a very large GTP-induced conformational change of the LRR domain, unleashing it from the Roc-COR domains, using the LRR-Roc linker as a hinge. Furthermore, this structure shows how Nb
Roco1
and Nb
Roco2
collaborate to activate CtRoco in an allosteric way. Altogether, our data provide important new insights in the activation mechanism of Roco proteins, with relevance to LRRK2 regulation, and suggest new routes for the allosteric modulation of their GTPase activity.
Embedding stochastic dynamics of the environment in spontaneous activity by prediction-based plasticity
Authors: Asabuki Toshitake , Clopath Claudia
Published: April 2024

The brain learns an internal model of the environment through sensory experiences, which is essential for high-level cognitive processes. Recent studies show that spontaneous activity reflects such learned internal model. Although computational studies have proposed that Hebbian plasticity can learn the switching dynamics of replayed activities, it is still challenging to learn dynamic spontaneous activity that obeys the statistical properties of sensory experience. Here, we propose a pair of biologically plausible plasticity rules for excitatory and inhibitory synapses in a recurrent spiking neural network model to embed stochastic dynamics in spontaneous activity. The proposed synaptic plasticity rule for excitatory synapses seeks to minimize the discrepancy between stimulus-evoked and internally predicted activity, while inhibitory plasticity maintains the excitatory-inhibitory balance. We show that the spontaneous reactivation of cell assemblies follows the transition statistics of the model’s evoked dynamics. We also demonstrate that simulations of our model can replicate recent experimental results of spontaneous activity in songbirds, suggesting that the proposed plasticity rule might underlie the mechanism by which animals learn internal models of the environment.
LPS-induced systemic inflammation is suppressed by the PDZ motif peptide of ZO-1 via regulation of macrophage M1/M2 polarization
Authors: Lee Hyun-Chae , Park Sun-Hee , Jeong Hye Min , Shin Goeun , Lim Sung In , Kim Jeongtae , Shim Jaewon , Park Yeong-Min , Song Kyoung Seob
Published: April 2024

The Gram-negative bacterium lipopolysaccharide (LPS) is frequently administered to generate models of systemic inflammation. In particular, both kidney and lung are more sensitive to acute injury caused by LPS-induced systemic inflammation. However, there are several side effects and no effective treatment for LPS-induced systemic inflammation.The PEGylated PDZ peptide was synthesized based on the PDZ motif of ZO-1 protein. We investigated the anti-inflammatory effect of PEGylated PDZ peptide on LPS-induced systemic inflammation in mice. We also performed the RNA-Sequencing analysis to know the expression pattern of 24,424 genes according to each comparison combination.PDZ peptide administration led to restoration of tissue injuries (kidney, liver, and lung) and prevented alterations in biochemical plasma markers. The production of pro-inflammatory cytokines was significantly decreased in the plasma and lung BALF in the PDZ-administered mice. Flow cytometry analysis revealed the PDZ peptide significantly inhibited inflammation, mainly by decreasing the population of M1 macrophages, neutrophils, and increasing M2 macrophages. Using RNA sequencing analysis, the expression levels of the NF-κB-related proteins were lower in PDZ-treated cells than in LPS-treated cells. Wild-type PDZ peptide significantly increased mitochondrial membrane integrity and decreased LPS-induced mitochondria fission. PDZ peptide dramatically could reduce LPS-induced NF-κB signaling, ROS production, and the expression of M1 macrophage marker proteins, but increased the expression of M2 macrophage marker proteins.These results indicated PEGylated PDZ peptide inhibits LPS-induced systemic inflammation, reducing tissue injuries and reestablishing homeostasis and may be a therapeutic candidate against systemic inflammation.
BMP9 and BMP10 coordinate liver cellular crosstalk to maintain liver health
Authors: Zhao Dianyuan , Huang Ziwei , Li Xiaoyu , Wang Huan , Hou Qingwei , Wang Yuyao , Yan Fang , Yang Wenting , Liu Di , Yi Shaoqiong , Han Chunguang , Hao Yanan , Tang Li
Published: April 2024

The liver is the largest solid organ in the body and is primarily composed of HCs, ECs, KCs, and HSCs, which spatially interact and cooperate with each other to maintain liver homeostasis. However, the complexity and molecular mechanisms underlying the crosstalk between these different cell types remain to be revealed. Here, we generated mice with conditional deletion of
Bmp9/10
in different liver cell types and demonstrated that HSCs were the major source of BMP9 and BMP10 in the liver. Using transgenic ALK1 (receptor for BMP9/10) reporter mice, we found that ALK1 is expressed on KCs and ECs other than HCs and HSCs. KCs from
Bmp9/10
HSC-KO
(conditional deletion of
Bmp9/10
from HSCs) mice lost their signature gene expression, such as ID1/3, CLEC4F, VSIG4 and CLEC2, and were replaced by monocyte-derived macrophages. ECs from
Bmp9/10
HSC-KO
mice also lost their identity and were transdifferentiated into continuous ECs, ultimately leading to collagen IV deposition and liver fibrosis. Hepatic ECs express several angiocrine factors, such as BMP2, BMP6, Wnt2 and Rspo3, to regulate liver iron metabolism and metabolic zonation. We found that these angiocrine factors were significantly decreased in ECs from
Bmp9/10
HSC-KO
mice, which further resulted in liver iron overload and disruption of HC zonation. In summary, we demonstrated that HSCs play a central role in mediating liver cell‒cell crosstalk via the production of BMP9/10 to maintain liver health.
A modified BPaL regimen for tuberculosis treatment replaces linezolid with inhaled spectinamides
Authors: Zohaib Ali Malik , Dutt Taru S , MacNeill Amy , Walz Amanda , Pearce Camron , Lam Ha , Philp Jamie S , Patterson Johnathan , Henao-Tamayo Marcela , Lee Richard , Liu Jiuyu , Robertson Gregory T , Hickey Anthony J , Meibohm Bernd , Gonzalez Juarrero Mercedes
Published: April 2024

The Nix-TB clinical trial evaluated a new 6 month regimen containing three oral drugs; bedaquiline (B), pretomanid (Pa), and linezolid (L) (BPaL regimen) for the treatment of tuberculosis (TB). This regimen achieved remarkable results as almost 90% of the multidrug-resistant or extensively drug-resistant TB participants were cured but many patients also developed severe adverse events (AEs). The AEs were associated with the long-term administration of the protein synthesis inhibitor linezolid. Spectinamide 1599 is also a protein synthesis inhibitor of Mycobacterium tuberculosis with an excellent safety profile, but it lacks oral bioavailability. Here, we propose to replace L in the BPaL regimen with spectinamide (S) administered via inhalation and we demonstrate that inhaled spectinamide 1599, combined with BPa ––BPaS regimen––has similar efficacy to that of the BPaL regimen while simultaneously avoiding the L-associated AEs. The BPaL and BPaS regimens were compared in the BALB/c and C3HeB/FeJ murine chronic TB efficacy models. After 4-weeks of treatment, both regimens promoted equivalent bactericidal effects in both TB murine models. However, treatment with BPaL resulted in significant weight loss and the complete blood count suggested the development of anemia. These effects were not similarly observed in mice treated with BPaS. BPaL and BPa, but not the BPaS treatment, also decreased myeloid to erythroid ratio suggesting the S in the BPaS regimen was able to recover this effect. Moreover, the BPaL also increased concentration of proinflammatory cytokines in bone marrow compared to mice receiving BPaS regimen. These combined data suggest that inhaled spectinamide 1599 combined with BPa is an effective TB regimen without L-associated AEs.