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Physicochemical properties constitute a key factor for the success of a drug candidate. Whereas many strategies to improve the physicochemical properties of small heterocycle-type leads exist, complex hydrocarbon skeletons are more challenging to derivatize because of the absence of functional groups. A variety of C-H oxidation methods have been explored on the betulin skeleton to improve the solubility of this very bioactive, yet poorly water-soluble, natural product. Capitalizing on the innate reactivity of the molecule, as well as the few molecular handles present on the core, allowed oxidations at different positions across the pentacyclic structure. Enzymatic oxidations afforded several orthogonal oxidations to chemical methods. Solubility measurements showed an enhancement for many of the synthesized compounds.

Epsilon‐and‐mu‐near‐zero (EMNZ) metamaterials have garnered significant attention in near‐zero‐parameter metamaterial research for their exceptional ability to attain concurrent near‐zero permittivity and permeability. Nowadays achieving EMNZ properties through the use of metacomposites remains a novel endeavor. Presented here is an innovative approach of near‐zero‐parameter metacomposites, illustrating excellent and tunable EMNZ properties in the radio frequency regime. The self‐organization approach is applied to construct the conductive 3D network and the circuits, serving as the underlying framework for achieving EMNZ properties. Near‐zero permeability is effectively maintained while permittivity reaches epsilon‐near‐zero frequency regime. Efficient manipulation of electromagnetic parameters is initially realized via adjusting component content in metacomposites. Significantly, an excellent EMNZ property is observed as carbon content reaches 15 wt.% at 915 MHz. Through both numerical simulations and experimental testing, the PGC metacomposites have exhibited tunneling effects and directional emission characteristics, confirming their EMNZ properties. Besides, the Lego‐like adjustment facilitates the achievement of EMNZ property and advances the EMNZ frequency point to 700 MHz, expanding the EMNZ range. Furthermore, thanks to the remarkable excitation effect of photo‐induced adjustment, the metacomposite with low‐carbon content also achieves extraordinary EMNZ properties. This research offers promising self‐organized EMNZ metacomposites and lays the foundation for future endeavors in precisely adjusting near‐zero parameters. [ABSTRACT FROM AUTHOR]

For a graph G and positive integers t , k , a (t , k) -tree-vertex coloring of G refers to a t -vertex coloring of G satisfying every component of each induced subgraph generated by every set of vertices with the same color forms a tree with maximum degree not larger than k , and it is called equitable if the difference between the cardinalities of every pair of sets of vertices with the same color is at most 1. The strong equitable vertex k -arboricity of G , denoted by v a k ≡ (G) , is defined as the least positive integer t satisfying G , which admits an equitable (t ′ , k) -tree-vertex coloring for each integer t ′ with t ′ ≥ t. The strong equitable vertex k -arboricity of a graph is very useful in graph theory applications such as load balance in parallel memory systems, constructing timetables and scheduling. In this paper, we present the tight upper and lower bounds on v a k ≡ (G) for an arbitrary graph G with n vertices and a given integer k with 1 ≤ k ≤ n − 1 , and we characterize the extremal graphs G with v a k ≡ (G) = 1 , v a k ≡ (G) = ⌈ n / 2 ⌉ − 1 , v a k ≡ (G) = ⌈ n / 2 ⌉ , respectively. Based on the above extremal results, we further obtain the Nordhaus–Gaddum-type results for v a k ≡ (G) of graphs G with n vertices for a given integer k with 1 ≤ k ≤ n − 1. [ABSTRACT FROM AUTHOR]

In order to suppress the transverse vibration of a plate, a quasi-zero-stiffness (QZS) resonator with tunable ultralow frequency bandgaps was introduced and analyzed. The resonator was designed by introducing the quasi-zero-stiffness systems into mass-in-mass resonators. The plane wave expansion method was employed to derive the bandgap characteristics of the locally resonant (LR) plate with QZS resonators, and corresponding simulations were carried out by finite element method (FEM). The results show that an LR plate with a QZS resonator can provide two bandgaps, and the ranges of the bandgaps agree well with the vibration attenuation bands calculated by FEM. Owing to the introduction of the QZS system, the bandgaps can be easily transferred to a lower frequency or even an ultralow frequency. The damping of the QZS resonators can effectively broaden the vibration attenuation bands. In addition, the differentiated design of the bandgap frequencies can be realized to obtain broadband low-frequency transverse wave suppression performance. Finally, a mechanical structure design scheme was proposed in order to achieve flexible adjustment of the bandgap frequency, which significantly increases the engineering applicability of QZS resonators. [ABSTRACT FROM AUTHOR]

Ceramic materials are widely used in engineering field because of their good physical and chemical properties. The poor mechanical properties of traditional ceramics seriously limit the development of ceramic materials and have attracted extensive attention since its birth. The development of high toughness, light weight, and functional ceramic materials has long been the pursuit of materials scientists. Since ancient times, nature has been the source of all kinds of human technological ideas, engineering principles, and major inventions. The functional structure of biology provides a good research object for the bionic design and preparation of ceramic materials. Therefore, it is necessary to summarize the functional structures and mechanisms in nature and biomimetic preparation technology. The purpose of this review is to provide guidance for the functionalized biomimetic design and efficient preparation of ceramic materials. Some typical functional examples in nature are introduced in detail, and several representative biomimetic preparation methods are listed. Finally, the performance and application status of biomimetic ceramics are summarized, and the future development direction of biomimetic ceramic materials is prospected. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) technology based on magnetic resonance (a basic physical phenomenon) can directly transfer energy from the source to the load without wires and other physical contacts, and has been successfully applied to implantable medical devices, electric vehicles, robotic arms and other fields. However, due to the frequency splitting of near-field coupling, the resonant WPT system has some unique limitations, such as poor transmission stability and low efficiency. Here, we propose anti-resonance with level pinning for high-performance WPT. By introducing the anti-resonance mode into the basic WPT platform, we uncover the competition between dissipative coupling and coherent coupling to achieve novel level pinning, and construct an effective anti-parity-time (anti- PT)-symmetric non-Hermitian system that is superior to previous PT -symmetric WPT schemes. On the one hand, the eigenvalue of the anti- PT -symmetric system at resonance frequency is always pure real in both strong and weak coupling regions, and can be used to overcome the transmission efficiency decrease caused by weak coupling, as brought about by, for example, a large size ratio of the transmitter to receiver, or a long transmission distance. On the other hand, due to the level pinning effect of the two kinds of coupling mechanisms, the working frequency of the system is guaranteed to be locked, so frequency tracking is not required when the position and size of the receiver change. Even if the system deviates from the matching condition, an efficient WPT can be realized, thereby demonstrating the robustness of the level pinning. The experimental results show that when the size ratio of the transmitter coil to the receiver coil is 4.29 (which is in the weak coupling region), the transfer efficiency of the anti- PT -symmetric system is nearly 4.3 (3.2) times higher than that of the PT -symmetric system when the matching conditions are satisfied (deviated). With the miniaturization and integration of devices in mind, a synthetic anti- PT -symmetric system is used to realize a robust WPT. Anti- PT -symmetric WPT technology based on the synthetic dimension not only provides a good research platform for the study of abundant non-Hermitian physics, but also provides a means of going beyond traditional near-field applications with resonance mechanisms, such as resonance imaging, wireless sensing and photonic routing. [ABSTRACT FROM AUTHOR]

To meet the requirements of shorter synchronization time and higher life for the synchronizer in transmission, mathematical models aiming at synchronization time and synchronizer life were established separately based on Newton’s second law and adhesive wear theory, M-B fractal contact model. The evaluation function was constructed by ideal point method to establish a multi-objective parameter optimization model with the two objectives. Using the AHP to determine weight value of the target in the multi-objective optimization model, and using the improved particle swarm algorithm to optimize the multi-objective parameter optimization model. The results show that the synchronization time is reduced by 8% and the synchronizer life is increased by 9% compared with that before optimization, the two objectives are improved better. The using of the improved particle swarm algorithm improves the performance of the synchronizer, and the application of the ideal point method effectively avoids the problem that the high order of magnitude dominates the multi-objective optimization.

Amyand hernia is a rare form of inguinal hernia wherein the appendix is in the hernial sac. Moreover, the incidence of Amyand hernia is reportedly three times higher in children than in adults. Here, we report a case of Amyand hernia in the right groin of a 55-year-old patient admitted to our hospital. We describe our approach to the diagnosis and treatment of Amyand hernia in this case. Altogether, we conclude that reasonable individualized diagnosis and treatment for Amyand hernia according to the patient's conditions is warranted in such cases.

Abstract Background The Chinese government has provided health services to those infected by the human immunodeficiency virus (HIV) under the acquired immunodeficiency syndrome (AIDS) care policy since 2003. Detailed research on the actual expenditures and costs for providing care to patients with AIDS is needed for future financial planning of AIDS health care services and possible reform of HIV/AIDS-related policy. The purpose of the current study was to determine the actual expenditures and factors influencing costs for untreated AIDS patients in a rural area of China after initiating highly active antiretroviral therapy (HAART) under the national Free Care Program (China CARES). Methods A retrospective cohort study was conducted in Yunnan and Shanxi Provinces, where HAART and all medical care are provided free to HIV-positive patients. Health expenditures and costs in the first treatment year were collected from medical records and prescriptions at local hospitals between January and June 2007. Multivariate linear regression was used to determine the factors associated with the actual expenditures in the first antiretroviral (ARV) treatment year. Results Five ARV regimens are commonly used in China CARES: zidovudine (AZT) + lamivudine (3TC) + nevirapine (NVP), stavudine (D4T) + 3TC + efavirenz (EFV), D4T + 3TC + NVP, didanosine (DDI) + 3TC + NVP and combivir + EFV. The mean annual expenditure per person for ARV medications was US$2,242 (US$1 = 7 Chinese Yuan (CNY)) among 276 participants. The total costs for treating all adverse drug events (ADEs) and opportunistic infections (OIs) were US$29,703 and US$23,031, respectively. The expenses for treatment of peripheral neuritis and cytomegalovirus (CMV) infections were the highest among those patients with ADEs and OIs, respectively. On the basis of multivariate linear regression, CD4 cell counts (100-199 cells/μL versus