Higher Fitness Research Articles

Competitiveness of reutericyclin producing and nonproducing Limosilactobacillus reuteri in food and intestinal ecosystems: a game of rock, paper, and scissors?

The ecological relationships among antimicrobial producing, resistant, and sensitive strains have been proposed to follow rock-paper-scissors dynamics, but evidence is mainly based on Gram-negative bacteriocins in vitro. The ecological relevance of antimicrobials in vivo or in situ has not been systematically studied. This study therefore aimed to analyze binary and ternary competitions among reutericyclin-producing strain Limosilactobacillus reuteri TMW1.656, its reutericyclin-resistant, nonproducing isogenic derivative L. reuteri TMW1.656∆rtcN, and the reutericyclin-sensitive, nonproducing L. reuteri TMW1.656∆rtcN∆rtcT in vitro (liquid culture and static plate), in situ (sourdough fermentation), and in vivo (gut of germ-free mice). In liquid culture, L. reuteri TMW1.656 had a higher fitness than TMW1.656∆rtcN and TMW1.656∆rtcN∆rtcT. Limosilactobacillus reuteri TMW1.656∆rtcN∆rtcT had a higher fitness than TMW1.656∆rtcN. On agar plates, L. reuteri TMW1.656 had a higher fitness than TMW1.656∆rtcN∆rtcT. In situ, reutericyclin production and resistance had no influence on the fitness of the strains. In vivo, TMW1.656 had an advantage over TMW1.656∆rtcN and TMW1.656∆rtcN∆rtcT. Ternary competitions showed reutericyclin production was ecologically beneficial in all ecosystems. The findings support the ecological importance of reutericyclin in a variety of environments/niches, providing an explanation for the acquisition of the reutericyclin gene cluster in L. reuteri and its contribution to the ecological fitness of Streptococcus mutans.

High-temperature strain sensor based on sapphire fiber Bragg grating.

Sapphire fiber Bragg grating (SFBG) is a promising high-temperature strain sensor due to its melting point of 2045°C. However, the study on the long-term stability of SFBG under high temperature with an applied strain is still missing. In this paper, we reported for the first time to our knowledge on the critical temperature point of plastic deformation of the SFBG and demonstrated that the SFBG strain sensor can operate stably below 1200°C. At first, we experimentally investigated the topography and the spectral characteristics of the SFBG at different temperatures (i.e., 25°C, 1180°C, and 1600°C) with applied 650 µε. The reflection peak of the SFBG exhibits a redshift of about 15 nm and broadens gradually within 8 h at 1600°C, and the tensile force value decreases by 0.60 N in this process. After the test, the diameter of the SFBG region decreases from 100 to 88.6 µm, and the grating period is extended from 1.76 to 1.79 µm. This indicates that the plastic deformation of the SFBG happened indeed, and it was elongated irreversibly. Moreover, the stability of the Bragg wavelength of the SFBG under high temperature with the applied strain was evaluated. The result demonstrates the SFBG can be used to measure strain reliably below 1200°C. Furthermore, the strain experiments of SFBG at 25°C, 800°C, and 1100°C have been carried out. A linear fitting curve with high fitness (R2 > 0.99) and a lower strain measurement error (<15 µε) can be obtained. The aforementioned results make SFBG promising for high-temperature strain sensing in many fields, such as, power plants, gas turbines, and aerospace vehicles.

Yeast-Based Magnetic Biocomposite for Efficient Sorption of Organic Pollutants

The study aimed to prepare a biocomposite containing Yarrowia lipolytica yeast cells with magnetic properties. The work proposes the use of this biocomposite as a sorbent for the removal of organic pollutants like methylene blue from liquids. The sorption process was conducted in a periodic process through which different parameters were analyzed such as initial concentration (50–250 mg/dm3), time of the process (0.167–24 h), and temperature (25–40 °C). To fit the experimental data to theoretical models, the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models were used. In addition, pseudo-first-rate, pseudo-second-rate order, Weber–Morris and Elovich kinetic models were evaluated. The highest fit was the Freundlich isotherm model (R2 = 0.9959 and ARE = 3.41%) and the pseudo-second-rate order model (R2 = 0.9989 and ARE = 1.14%). It has been shown that the process of removing methylene blue using a biocomposite is exothermic and its usefulness decreases with an increase in temperature (from 32.10 mg/g to 23.64 mg/g). To acquire information about the material characteristics, different instrumental methods were applied: FTIR, SEM-EDX, TGA, and VSM. This study provides new information on the possibility of using composites made of biochar, yeast, and magnetic particles in the process of removing dyes from an aqueous environment. The obtained biocomposite is effective in removing contaminants and is easily separated after the performed process.

Replicative fitness and pathogenicity of primate lentiviruses in lymphoid tissue, primary human and chimpanzee cells: relation to possible jumps to humans

Simian immunodeficiency viruses (SIV) have been jumping between non-human primates in West/Central Africa for thousands of years and yet, the HIV-1 epidemic only originated from a primate lentivirus over 100 years ago. This study examined the replicative fitness, transmission, restriction, and cytopathogenicity of 22 primate lentiviruses in primary human lymphoid tissue and both primary human and chimpanzee peripheral blood mononuclear cells. Pairwise competitions revealed that SIV from chimpanzees (cpz) had the highest replicative fitness in human or chimpanzee peripheral blood mononuclear cells, even higher fitness than HIV-1 group M strains responsible for worldwide epidemic. The SIV strains belonging to the "HIV-2 lineage" (including SIVsmm, SIVmac, SIVagm) had the lowest replicative fitness. SIVcpz strains were less inhibited by human restriction factors than the "HIV-2 lineage" strains. SIVcpz efficiently replicated in human tonsillar tissue but did not deplete CD4+ T-cells, consistent with the slow or nonpathogenic disease observed in most chimpanzees. In contrast, HIV-1 isolates and SIV of the HIV-2 lineage were pathogenic to the human tonsillar tissue, almost independent of the level of virus replication. Of all primate lentiviruses, SIV from chimpanzees appears most capable of infecting and replicating in humans, establishing HIV-1. SIV from other Old World monkeys, e.g. the progenitor of HIV-2, replicate slowly in humans due in part to restriction factors. Nonetheless, many of these SIV strains were more pathogenic than SIVcpz. Either SIVcpz evolved into a more pathogenic virus while in humans or a rare SIVcpz, possibly extinct in chimpanzees, was pathogenic immediately following the jump into human. Support for this study to E.J.A. was provided by the NIH/NIAID R01 AI49170 and CIHR project grant 385787. Infrastructure support was provided by the NIH CFAR AI36219 and Canadian CFI/Ontario ORF 36287. Efforts of J.A.B. and N.J.H. was provided by NIH AI099473 and for D.H.C., by VA and NIH AI AI080313.

Empirical validation of ProteinMPNN's efficiency in enhancing protein fitness.

Introduction: Protein engineering, which aims to improve the properties and functions of proteins, holds great research significance and application value. However, current models that predict the effects of amino acid substitutions often perform poorly when evaluated for precision. Recent research has shown that ProteinMPNN, a large-scale pre-training sequence design model based on protein structure, performs exceptionally well. It is capable of designing mutants with structures similar to the original protein. When applied to the field of protein engineering, the diverse designs for mutation positions generated by this model can be viewed as a more precise mutation range. Methods: We collected three biological experimental datasets and compared the design results of ProteinMPNN for wild-type proteins with the experimental datasets to verify the ability of ProteinMPNN in improving protein fitness. Results: The validation on biological experimental datasets shows that ProteinMPNN has the ability to design mutation types with higher fitness in single and multi-point mutations. We have verified the high accuracy of ProteinMPNN in protein engineering tasks from both positive and negative perspectives. Discussion: Our research indicates that using large-scale pre trained models to design protein mutants provides a new approach for protein engineering, providing strong support for guiding biological experiments and applications in biotechnology.

Different populations of A(H1N1)pdm09 viruses in a patient with hemolytic-uremic syndrome

Respiratory viral infections may have different impacts ranging from infection without symptoms to severe disease or even death though the reasons are not well characterized.A patient (age group 5–15 years) displaying symptoms of hemolytic uremic syndrome died one day after hospitalization. qPCR, next generation sequencing, virus isolation, antigenic characterization, resistance analysis was performed and virus replication kinetics in well-differentiated airway cells were determined.Autopsy revealed hemorrhagic pneumonia as major pathological manifestation. Lung samples harbored a large population of A(H1N1)pdm09 viruses with the polymorphism H456H/Y in PB1 polymerase. The H456H/Y viruses replicated much faster to high viral titers than upper respiratory tract viruses in vitro. H456H/Y-infected air-liquid interface cultures of differentiated airway epithelial cells did reflect a more pronounced loss of ciliated cells. A different pattern of virus quasispecies was found in the upper airway samples where substitution S263S/F (HA1) was observed.The data support the notion that viral quasispecies had evolved locally in the lung to support high replicative fitness. This change may have initiated further pathogenic processes leading to rapid dissemination of inflammatory mediators followed by development of hemorrhagic lung lesions and fatal outcome.

Chlorella vulgaris Harvesting: Chemical Flocculation with Chitosan, Aluminum Sulfate, and Ferric Sulfate

Chlorella vulgaris, a widely cultivated microalgae with diverse commercial applications, faces challenges in economic viability and scalability during the crucial biomass harvesting step. This study explores chemical flocculation followed by sedimentation as a cost-effective solution. Optimization was performed for three flocculants (chitosan, aluminum sulfate, and ferric sulfate), with experiments determining optimal pH and dosage ranges (10–200 mg·L−1). A 24-full factorial design optimized flocculant dosage, settling time, rapid mixing time, and slow mixing time, analyzing their effects on harvesting efficiency through empirical models. The optimal dosage ranges were 50–200 mg·L−1 for aluminum sulfate and 150–200 mg·L−1 for ferric sulfate at pH 9, and 10–50 mg·L−1 for chitosan at pH 5. Empirical models exhibited high fitting performance (R2 &gt; 95%) and predictive capability (predicted R2 &gt; 96%). All flocculants demonstrated high efficiencies (98.4–99.5%), with inorganic types requiring fast and slow mixing phases, while chitosan achieved optimal results without the need for both mixing phases, suggesting potential industrial advantages in time and energy efficiency for microalgae harvesting.

Unveiling a novel mechanism for competitive advantage of ciprofloxacin-resistant bacteria in the environment through bacterial membrane vesicles

Ciprofloxacin (CIP) is a prevalent environmental contaminant that poses a high risk of antibiotic resistance. High concentrations of antibiotics can lead to the development of resistant bacteria with high fitness costs, which often face a competitive disadvantage. However, it is unclear whether low-cost resistant bacteria formed by exposure to sub-MIC CIP in the environment can evolve competitive mechanisms against sensitive Escherichia coli (SEN) other than stronger resistance to CIP. Our study exposed E. coli to sub-MIC CIP levels, resulting in the development of CIP-resistant E. coli (CIPr). In antibiotic-free co-culture assays, CIPr outcompeted SEN. This indicates that CIPr is very likely to continue to develop and spread in antibiotic-free environments such as drinking water and affect human health. Further mechanism investigation revealed that bacterial membrane vesicles (BMVs) in CIPr, functioning as substance delivery couriers, mediated a cleavage effect on SEN. Proteomic analysis identified Entericidin B (EcnB) within CIPr-BMVs as a key factor in this competitive interaction. RT-qPCR analysis showed that the transcription of its negative regulator ompR/envZ was down-regulated. Moreover, EcnB plays a crucial role in the development of CIP resistance, and some resistance-related proteins and pathways have also been discovered. Metabolomics analysis highlighted the ability of CIPr-BMVs to acidify SEN, increasing the lytic efficiency of EcnB through cationization. Overall, our study reveals the importance of BMVs in mediating bacterial resistance and competition, suggesting that regulating BMVs production may be a new strategy for controlling the spread of drug-resistant bacteria.

Machine learning-guided design of potent darunavir analogs targeting HIV-1 proteases: A computational approach for antiretroviral drug discovery.

In the pursuit of novel antiretroviral therapies for human immunodeficiency virus type-1 (HIV-1) proteases (PRs), recent improvements in drug discovery have embraced machine learning (ML) techniques to guide the design process. This study employs ensemble learning models to identify crucial substructures as significant features for drug development. Using molecular docking techniques, a collection of 160 darunavir (DRV) analogs was designed based on these key substructures and subsequently screened using molecular docking techniques. Chemical structures with high fitness scores were selected, combined, and one-dimensional (1D) screening based on beyond Lipinski's rule of five (bRo5) and ADME (absorption, distribution, metabolism, and excretion) prediction implemented in the Combined Analog generator Tool (CAT) program. A total of 473 screened analogs were subjected to docking analysis through convolutional neural networks scoring function against both the wild-type (WT) and 12 major mutated PRs. DRV analogs with negative changes in binding free energy ( ) compared to DRV could be categorized into four attractive groups based on their interactions with the majority of vital PRs. The analysis of interaction profiles revealed that potent designed analogs, targeting both WT and mutant PRs, exhibited interactions with common key amino acid residues. This observation further confirms that the ML model-guided approach effectively identified the substructures that play a crucial role in potent analogs. It is expected to function as a powerful computational tool, offering valuable guidance in the identification of chemical substructures for synthesis and subsequent experimental testing.

The Effective Path of High-quality Employment for College Students under the Perspective of “Internet+”

Abstract The rapid development of higher education has made the social supply far greater than the social demand, which has created the problem of difficult employment for college students. The implementation of the national strategy of strengthening human resources and the healthy development of a harmonious society is facilitated by solving the employment problem of college students. In this study, we first constructed a model of college students’ employment through factor analysis and explored the key factors that affect the employment quality of college students. The keywords were used to extract the hotspots of corporate recruitment and to extract measurement variables such as GPA scores. Factor analysis was used to find out the potential variables, extract the effective factors greater than 1, name and number the principal component factors, and identify the items with the highest correlation of each principal component factor, respectively. The model of this paper was validated through exploratory and validation analyses on the obtained data, which were consistent between the validation and exploratory samples. The actual value of X² was 0.7312, which was in line with the evaluation criteria. The evaluation criteria are met by the values of the other five indicators. The model’s high fit and scientific construction are reflected by it. This paper integrates factor analysis with the exploration of college students’ employment pathways, providing a set of application models that can be used as a reference.

Analysis and Research on Production Effects of Full-Film Double Ridge-Furrow Mulching with Polyethylene Film and Biodegradable Film Based on AquaCrop

Water is an important factor limiting the development of arid rain-fed agriculture. Film mulching is an effective way to ensure yield in arid areas. However, whether biodegradable film can be used instead of polyethylene film for agricultural production in arid areas is a matter of contention. In this study, AquaCrop model simulation and field experiment were used to analyze the production effect of corn whole film double ridge furrow sowing technology covering polyethylene film (PM) and biodegradable film (BM) in Dingxi City from 2016 to 2020. The results showed that the AquaCrop simulation data have a high fitting with the field test data, and the model was suitable for simulating dry farming in Dingxi City. The best sowing time in Dingxi City is to select the average temperature to be stable at about 15 °C (around 15 April to 25 April each year), and the yield is the highest after sowing during this period. Although BM can achieve environmental protection and energy saving, it is weaker than PM in water storage and soil evaporation inhibition in arid areas. The average yield, aboveground biomass, water productivity, and harvest index of PM were 63.95%, 18.57%, 76.35%, and 38.22% higher than those of BM, respectively. In drought years, BM water stress on leaf expansion, induced stomatal closure, and premature senescence were 61%, 17%, and 9.5% higher than PM, respectively, and the stress time was 28.5 d, 5 d, and 26 d, respectively. The maximum canopy coverage and effective root zone water content were 24.5% and 30.49% lower, respectively. In the wet year, water stress under BM only had a certain effect on the leaf expansion of crops but had no effect on the induction of stomatal closure and premature senescence. The maximum canopy coverage and effective root zone water content were 13.56% and 31.35% lower, respectively. The above studies show that BM has a certain ability to store water and preserve moisture, but the parameters of PM are better than BM. Especially in dry years, the crop production efficiency of PM is more significant. It can be seen that in rain-fed agricultural areas with rainfall less than 500 mm, biodegradable film can not replace polyethylene film.

Construction of Electricity Load Forecasting Model Based on Electricity Data Analysis

Abstract This paper builds a time series prediction model of recurrent neural networks based on time series electricity load forecasting. In this paper, the household electricity consumption record data of some residents in urban area S is taken as the research object, and the laws and characteristics of users’ electricity consumption behavior are analyzed in depth based on the real residential electricity consumption data. External factors such as temperature conditions, holidays, etc. The arithmetic cases are also analyzed using real load data sets. In the short-term continuous electricity data analysis, the smaller the time interval is, the closer its corresponding electricity consumption ratio is to 1. There is a negative correlation between long-term continuous electricity consumption. When the temperature is 30~35oC versus -5~0oC, electricity consumption rises significantly. Comparing and analyzing the time series decomposition-RNN with several models, the time series decomposition-RNN model has the highest fit at 10:00-12:00 and 12:00-14:00, and the result verifies the validity of the model proposed in this paper.

Development and psychometric properties of a self-medication behavior inventory.

Self-medication is a prevalent behavior with significant health implications. Understanding its psychosocial determinants can inform preventative strategies and interventions. We evaluated the psychometric properties of the Self-Medication Behavior Inventory (SMBI-9) in a binational study with 779 Colombian and Mexican participants. Concurrent validity was assessed through correlations with related inventories, and confirmatory factor analysis tested the proposed four-factor model. The SMBI-9 demonstrated high model fit (CFI = 0.995, TLI = 0.991) and invariance across countries. The factors-Social Influence, Attitude toward Medicine, Avoidance, and Prevention-varied significantly with knowledge of medicine, schooling, health insurance status and gender, underscoring the role of social and personal beliefs in self-medication practices. SMBI-9 emerged as a reliable tool for capturing the multifaceted nature of self-medication behaviors. Findings highlight the influence of social norms and personal attitudes, suggesting targeted approaches for behavioral interventions.

Research on the linkage of “one, two, three, four classrooms” of ideological and political education in colleges and universities based on big data platform.

Abstract To comprehensively improve the quality of ideological and political education in colleges and universities, and to ensure the realization of the fundamental goal of cultivating morality and educating people, this paper emphasizes the importance of the “one, two, three, four classrooms” linkage teaching mode, and proposes an intelligent ideological and political education platform based on big data technology. The platform integrates the first, second, third and fourth classrooms to form an efficient linkage education model. To assess the specific impact of this model on education quality, this study constructed a model using multiple linear regression and estimated the parameters using the least squares method. Through the questionnaire survey and data analysis of five colleges and universities in the university city of L city, it was found that the development quality of the “one, two, three, four classrooms” linkage was generally distributed with the mean value lying in the interval of [0.35,0.55]. Under the baseline regression analysis, the four classrooms had a high R2 fit value of 0.8517 to the dependent variable. The quantile regression analysis showed that as the quantile nodes increased from 0.5 to 1, the number of classroom nodes risen from 1 to 2. Showed that as the quantile node increased from 0.1 to 0.9, the R2 fit value improved more than twofold. This result highlights the need to consider the teaching effect of each classroom comprehensively to ensure that the goal of high-quality development can be realized when colleges and universities promote the “one, two, three, four classrooms” linkage teaching mode of Civics.

Genes associated with fitness and disease severity in the pan-genome of mastitis-associated Escherichia coli.

Bovine mastitis caused by Escherichia coli compromises animal health and inflicts substantial product losses in dairy farming. It may manifest as subclinical through severe acute disease and can be transient or persistent in nature. Little is known about bacterial factors that impact clinical outcomes or allow some strains to outcompete others in the mammary gland (MG) environment. Mastitis-associated E. coli (MAEC) may have distinctive characteristics which may contribute to the varied nature of the disease. Given their high levels of intraspecies genetic variability, virulence factors of commonly used MAEC model strains may not be relevant to all members of this group. In this study, we sequenced the genomes of 96 MAEC strains isolated from cattle with clinical mastitis (CM). We utilized clinical severity data to perform genome-wide association studies to identify accessory genes associated with strains isolated from mild or severe CM, or with high or low competitive fitness during in vivo competition assays. Genes associated with mastitis pathogens or commensal strains isolated from bovine sources were also identified. A type-2 secretion system (T2SS) and a chitinase (ChiA) exported by this system were strongly associated with pathogenic isolates compared with commensal strains. Deletion of chiA from MAEC isolates decreased their adherence to cultured bovine mammary epithelial cells. The increased fitness associated with strains possessing this gene may be due to better attachment in the MG. Overall, these results provide a much richer understanding of MAEC and suggest bacterial processes that may underlie the clinical diversity associated with mastitis and their adaptation to this unique environment.

Early Career South African Occupational Therapists' Perceptions of Person-Environment Fit in Work-Life Areas That Influence Work Stress.

Introduction: Poor fit between the work environment and work expectations is associated with high levels of workplace-related stress. Work stress in occupational therapy has been attributed to the nature of the profession and various other workplace-related factors. Workplace-related stress leading to burnout has been found to be higher in early career occupational therapists with less than 5 years of experience. This study explored workplace factors that result in poor person-work environment fit in six work-life areas in South African early career occupational therapists. Methods: A descriptive electronic survey design was used to access a sample of South African 261 occupational therapists with 2-5 years of work experience. The Area of Work-Life Survey (AWS) considers six work-life areas: control, workload, community, rewards, values, and fairness, which were used to collect data. Data were analysed to determine low, moderate, and high work environment fit for workplace factors including employment setting, field of practice, years' experience, time with current organization, and hours worked. Results: Of the six work-life areas, only the scores for workload fell below the norm for the respondents. All six work-life areas were impacted by employment settings, with respondents in public health hospitals and clinics indicating significantly low person-environment fit in most areas. Respondents in physical rehabilitation had a significantly low fit for workload, as did years of experience, length of time with organization, and hours worked. Fairness had a low fit for physical rehabilitation and medicolegal fields of practice. Conclusion: Workload impacted workplace-related stress in respondents with scores below the norm on the AWS for this work-life area. Although some work-related factors affected workplace-related stress, the overall scores for the other work-life areas were above the norm, with only respondents in public service settings and in the field of physical rehabilitation reporting low work environment fit.

Evidence of validity of a Jealousy Scale in Peruvian youth and adults: An item response theory approach

Introduction/Objective: In romantic relationships, jealousy can influence how individuals feel emotionally and interact with their partners. This study analysed the metric properties of the Brief Jealousy Scale (BJS) in young adults from Peru using current methods. Method: A total of 297 individuals were selected to participate in the study. They averaged 26.52 years of age (with a variation of 7.75 years), and 74.10% were women. The study used a technique called Item Response Theory (IRT) with a two-parameter model to confirm the structure and reliability of the BJS. Result: The BJS demonstrated high reliability and fit through goodness-of-fit indices. DIF analysis indicated slight gender biases in some items, reflecting differences in the perception of jealousy between men and women. Conclusions: The study highlights the importance and usefulness of the Jealousy Scale in relationships, as it helps to understand relationship dynamics and guides interventions. Future studies should address issues such as participant selection and study design and examine whether the scale can be used in different cultures.

Implementation of basic life support education for the lay public in China: barriers, enablers, and possible solutions.

Education for the lay public in basic life support (BLS) is critical for increasing bystander cardiopulmonary resuscitation (CPR) rates and improving survival from out-of-hospital cardiac arrest (OHCA). Despite years of implementation, the BLS training rate in China has remained modest. The aim of this study was to investigate the factors influencing the implementation of BLS training programs in emergency medical service (EMS) centers in China and to identify specific barriers and enablers. Qualitative interviews were conducted with key informants from 40 EMS centers in Chinese cities. The participants included 11 directors/deputy directors, 24 training department leaders, and 5 senior trainers. The interview guide was based on the Exploration, Preparation, Implementation, Sustainment (EPIS) framework. Thematic content analysis was used to identify themes and patterns across the interviews. We identified 16 factors influencing the implementation of BLS training programs encompassing the outer content, inner context, innovation and bridging factors. Some factors acted as either barriers or enablers at different EPIS stages. The main implementation barriers included limited external leadership, insufficient government investment, low public awareness, a shortage of trainers, an absence of incentives, an absence of authoritative courses and guidelines, a lack of qualification to issue certificates, limited academic involvement, and insufficient publicity. The main enablers were found to be supportive government leaders, strong public demand, adequate resources, program champions, available high-quality courses of high fitness within the local context, the involvement of diverse institutions, and effective publicity and promotion. Our findings emphasize the diversity of stakeholders, the complexity of implementation, and the need for localization and co-construction when conducting BLS training for lay public in city EMS centers. Improvements can be made at the national level, city level, and EMS institutional level to boost priority and awareness, promote legislation and policies, raise sustainable resources, and enhance the technology of BLS courses.

Improved electro-mechanical model and energy conversion efficiency analysis of pulsed plasma thrusters

The primary electro-mechanical model is developed for the acceleration kinetics of electromagnetic railguns. Pulsed plasma thrusters (PPTs), whose operation principle is similar to that of electromagnetic railguns, generate thrust via electromagnetic acceleration of plasma. Therefore, the electro-mechanical model serves as a valuable analytical tool to explore the mechanisms of energy conversion and thrust generation of PPTs. In fact, a PPT initiates discharge at its propellant surface and then ejects the discharged channel away to form accelerated plume. During the acceleration, the plasma channel assumes a curved shape, which is different from the flat sheet shape. The curved geometric shape of PPT discharge channel makes the flat current sheet model currently used in the electro-mechanical models inherently flawed. In this paper, a two-dimensional (2D) curved current sheet model is proposed to improve the PPT electro-mechanical model, by referring to the curved morphology of PPT discharge plasma channels. &lt;xref ref-type="fig" rid="Figure1"&gt;Figure 1&lt;/xref&gt; shows the schematic of a typical PPT discharge circuit and the curved PPT discharge plasma channel that is indicated as the pink curve &lt;inline-formula&gt;&lt;tex-math id="M1"&gt;\begin{document}$ \widehat{ab} $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; according to the curved thin current sheet model. Also in &lt;xref ref-type="fig" rid="Figure1"&gt;Fig. 1&lt;/xref&gt; a current element &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}$ {\mathrm{d}}\boldsymbol{l} $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;of the discharge channel is taken arbitrarily to display its instant velocity &lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}$ \boldsymbol{v} $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; and the Ampere force element &lt;inline-formula&gt;&lt;tex-math id="M4"&gt;\begin{document}$ {\mathrm{d}}\boldsymbol{F} $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; exerted by the magnetic field induced by the PPT current circuit. The pink dashed curve &lt;inline-formula&gt;&lt;tex-math id="M5"&gt;\begin{document}$ \widehat{cd} $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; represents the position of the current sheet just after time d&lt;i&gt;t&lt;/i&gt; . Using the 2D curved current sheet model and according to the detail shown in &lt;xref ref-type="fig" rid="Figure1"&gt;Fig. 1&lt;/xref&gt;, the Ampere force on discharge plasma channels and corresponding kinetics can be derived to obtain final kinetic energy of discharge plasma channels. As a result, the relation between the kinetic energy and the inductance of PPT discharge circuit is obtained and expressed as &lt;inline-formula&gt;&lt;tex-math id="M6"&gt;\begin{document}$ {E}_{{\mathrm{k}}}=\displaystyle\int _{0}^{{t}_{{\mathrm{e}}{\mathrm{n}}{\mathrm{d}}}}{i\left(t\right)}^{2}\frac{{\mathrm{d}}{L}_{{\mathrm{e}}{\mathrm{q}}}\left(t\right)}{{\mathrm{d}}t}{\mathrm{d}}t $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;. To determine the inductance as a temporal function, an algorithm for the inductance is proposed in which time-segment fitting of PPT discharge waveforms is adopted. Moreover, based on the temporal function of the inductance, PPT discharge waveforms can be simulated by using the ODE45 solver of MATLAB with high fitting goodness. So far, a calculation scheme for the kinetic energy of PPT plumes and simulation code for PPT discharge waveforms have set up based on the improved electro-mechanical model. To verify the improved model and the corresponding calculation scheme, the PPT prototype is used to evaluate its energy conversion efficiency. The results show that the model enables elucidating the low PPT electro-mechanical efficiency, which is attributed to the partition limitation of PPT energy to electromagnetic acceleration process. Accordingly, a possible exploration routine for elevating PPT electro-mechanical efficiency is suggested.

Different metabolic adaptation strategies after overwintering in Eutrema sp. and Arabidopsis accessions under field conditions in Germany.

Successful overwintering is a prerequisite for high fitness in temperate perennials and winter annuals and is highly dependent on increased freezing tolerance and timely balancing of deacclimation with growth resumption in spring. To assess fitness costs associated with overwintering and elucidate metabolic mechanisms underlying winter survival and the switch from acclimated freezing tolerance to growth resumption, we performed a comparative field study using 14 Eutrema salsugineum accessions, E. halophilum, E. botschantzevii and 11 Arabidopsis thaliana accessions differing in freezing tolerance. Winter survival and reproductive fitness parameters were recorded and correlated with phenological stage and metabolite status during growth resumption in spring. The results revealed considerable intraspecific variation in winter survival, but survival rates of the extremophyte Eutrema were not inherently better. In both Eutrema and A. thaliana, improved winter survival was associated with reduced reproductive fitness. Metabolic analysis by GC-MS revealed intrinsic differences in the primary metabolism of the two genera during deacclimation. Eutrema contained higher levels of several amino and chlorogenic acids, while Arabidopsis had higher levels of several sugars and sugar conjugates. In both genera, increased levels of several soluble sugars were associated with increased winter survival, whereas myo-inositol has different roles in overwintering of Eutrema and A. thaliana. In addition, differences in amino acid metabolism and polyhydroxy acids levels after winter survival were found. The results provide strong evidence for a trade-off between increased winter survival and reproductive fitness in both Eutrema and Arabidopsis and document inherent differences in their metabolic strategies to survive winter.