载人航天器座舱大气控制系统优化设计方法的探讨

本文把最优化原理用于载人航天器座舱大气控制系统设计,以系统的重量、体积、可靠性、成本和技术复杂程度为目标,建立了系统及其部组件的目标函数和有关性能计算公式,并用BASIC 语言编制了计算机设计程序,在微型计算机上进行了实例计算,证明本优化设计方法能够用于载人航天座舱大气控制系统总体设计。     

载人航天器通风除湿系统运行参数的优化分析

目的：研究载人航天器通风除湿系统运行参数及一些组件的设计与优化方法，方法：建立了载人航天器通风除湿系统的数学物理模型，通过设计合适的系统运行参数及时有效地除去舱内产生的热量、水分、防止结露，满足人体的舒适性要求，并且采用计算的方法，分析了各种运行参数及组件对系统当量质量的影响。结果：载人航天器进舱气流温度、相对湿度及通风率、稻谷散湿量都影响舱内气体的露点温度及舒适性。舱内空气参数的有两种方式：以控制温度为主要目标的设计方法，回路中不需要使用余热回收换热器，结构简单，但有时不能满足除湿要求，优先满足湿度控制目标的方法，能够稳定控制舱内露点的温度、有利于防止结露，但系统结构较为复杂，结论：在保证系统性能的前提下，采用优化设计措施可以减轻空气处理系统的质量及耗电量，实现系统的轻量化。     

重力/失重条件下密闭舱内温湿度控制系统的通风和换热特性研究

目的 在地面条件下研究、评估载人航天飞行中密闭舱内温湿度控制系统的通风和换热特性.方法 在实验室密闭舱内构建一个温湿度控制系统,测量舱内不同剖面的温度、湿度和气流速度,并通过计算流体力学分析重力和失重条件下该温湿度控制系统的效能.结果 全面评估了构建的温湿度控制系统重力和失重务件下的温度、湿度控制能力,系统分析了重力和失重条件下的气流分布状态,证明它满足空间站的使用要求.结论 本文提供的方法可以作为密闭舱内温湿度控制系统工程设计的辅助手段,用于任意重力条件下的密闭舱布局设计和大气环境分析.     

载人航天器固态胺吸附动力学模型研究

目的研究固态胺吸附过程的动力学模型,为后续载人航天器固态胺系统的设计提供精确的理论分析方法。方法在分析多个动力学模型的基础上,选择分数阶动力学模型作为固态胺吸附模型;设计不同温度下吸附性能实验,利用热重仪,获得固态胺样品的吸附能力,辨识出分数阶吸附动力学参数k、m、n;采用其它吸附模型,并识别其参数,计算模型误差,获得最佳动力学模型。结果 H-S分数阶模型在各个条件下的误差均最低,与仿真曲线结果一致,能正确反映固态胺复杂吸附机理;温度升高,固态胺CO_2吸附性能呈线性显著下降趋势;浓度越高,吸附速率越快,吸附量也越大。结论 H-S分数阶是目前反映固态胺吸附动力学过程的最佳模型,能反映出多个工况下多个吸附阶段综合作用的结果,在固态胺系统仿真与设计时可采用此动力学模型作为理论依据。     

载人航天器压力应急状况下舱压变化的仿真研究

目的 研究载人航天器压力应急状况下尤其是舱壁穿孔时的 舱压变化。方法 通过对飞船座舱等孔边界条件和影响因素的分析，建立应急情况下舱压文化对象数学模型，采用计算机程序对舱压氧分压变化进行仿真研究。结果 通过仿真结果和试验结果的比较证明了仿真结果的可信性。结论 建立的对象模型是可信的，可以作的工程设计参考依据。     

载人航天器的人工控制问题

在载人航天器总体设计中,提供一定程度的人工控制系统,是确保系统安全可靠的技术途径之一,这对长期飞行尤为重要,本文阐述了载人航天器系统设计时进行人工控制的原则,主要应用项目和对人－机界面的一般要求,最后,提出几点看法以供讨论。     

载人飞行舱内压力服技术研究与实现

目的研究用于载人飞行舱内压力服的实现技术,研制舱内压力服系统.方法通过分析提出研制方案,针对载人航天器应急救生的技术性能要求,研究压力服的结构实现技术、压力控制技术、操作活动性能的保证技术、通风供氧技术、视觉保证和防雾技术的实现方法,通过研制和试验验证保证航天服的技术性能.结果在设计和工艺上实现了载人航天飞行所需压力防护和工效保障要求的舱内压力服系统,并通过了性能和接口匹配试验以及严酷的环境试验验证. 结论所研制的舱内压力服完全能够满足天地往返运输系统的压力应急工况使用要求.     

载人航天测控的医学监测问题

在载人航天中,为了确保航天员生命安全和飞行任务的实现,应对飞行中的航天器的环境和工作状态、航天员的身体健康状态和工作情况进行监测与控制。为此,需要设置载人航天测控网,对航天器的发射、轨道运行、再入和返回以及航天员的监督与保证,实施支持与监控。本文将从医学角度,阐述载人航天测控中的医学监测问题。     

航天器环控生保系统载人飞行性能地面试验研究

目的 地面重力条件下验证载人航天器环控生保系统载人飞行工作性能.方法 构建与真实飞行器密封舱段1:1的试验舱系统,集成了环控生保系统;选拔3名男性作为受试者参加试验,其消耗/代谢的物质和能量作为试验主要负荷;按照真实的载人飞行程序制定试验流程.结果 建成了一套仿真程度较高的模拟试验系统;确立了地面条件下环控生保系统性能...     

模拟条件及乘员感受对环控生保试验评价的影响

目的从载人航天器环控生保系统地面性能模拟试验的需求出发,根据对试验模拟条件和乘员感受影响进行改进,提高试验评价准确性。方法由以往多次地面模拟载人环控生保系统性能试验,分析出模拟条件与进舱参试乘员感受差异对环控生保系统性能试验评价的影响因素,并针对这些影响提出解决问题的方法。结果改善模拟试验条件和改进设备布局后使舱内环境模拟更加接近实际,乘员感觉得到改善,提高了评价结果的客观性和准确性。结论解决好模拟舱设备布局差异、环境模拟差异以及试验人员生活感受对评价的影响等问题,可以做好载人航天器环控生保系统性能的地面模拟试验,对载人航天器的环控生保系统的性能做出正确评价。     

Antimicrobial efficacy,optical properties and flexural strength following antimicrobial photodynamic therapy over vacuum-formed orthodontic retainers

Background and aimsVacuum-formed retainers (VFRs) are widely used in dental practices because of their superior esthetics. However, simultaneous maintenance of their hygiene, mechanical and optical properties is challenging. This study aimed to evaluate and compare the disinfection efficacy of antimicrobial photodynamic therapy (aPDT), chlorhexidine (CHX), sodium hypochlorite (NaOCl) and water over VFRs specimens, along with their effect on flexural strength and color stability.Materials and methodsFabricated VFRs of thicknesses 1 mm and 2 mm were contaminated with S. mutans and C. albicans. Brain Heart Infusion agar was used to seed Streptococcus Mutans whereas Candida Albicans was seeded in Sabourand Dextrose Agar. The contaminated retainers were divided into four groups and decontaminated using four different treatment protocols: aPDT, CHX, NaOCl and water, with 10 specimens per group. Microbial viability following decontamination, was assayed using MTT. To assess the color stability, pre and post decontamination color difference of 10 specimens was recorded using a spectrophotometer by blinding technique. The flexural strength of 10 specimens was measured using a universal testing machine by a standardized 3-point flexural strength (FS) test.ResultaPDT showed the highest reduction in the viability of S. mutans (28%) and C. albicans (20%) species in 1 mm thickness group while the second highest reduction following disinfection with CHX (40%) in followed by NaOCl disinfection (50%). On comparison between 1 mm and 2 mm, a statistically significant difference was noted for S. mutans in aPDT (p = 0.033) and NaOCl (p = 0.028) groups, and for C. albicans, a significant difference was noted within NaOCl (p = 0.001) and CHX (p = 0.043) groups. For FS, a statistically significant difference (p < 0.05) was observed between aPDT and the rest of the groups, whereas there was no statistically significant difference in the flexural strength between the CHX, NaOCl and water groups (p > 0.05) in both 1 mm and 2 mm specimens. Between 1 mm and 2 mm specimens, no statistically significant difference in the mean color difference was noted after any disinfection protocol (p > 0.05).ConclusionAntimicrobial photodynamic therapy showed a remarkable reduction in candidal and bacterial viability over VFRs. aPDT treated VFR specimens showed increased flexural strength and a higher color difference post treatment compared to other reagents.     

Antimicrobial photothermal therapy using diode laser with indocyanine green on Streptococcus gordonii biofilm attached to zirconia surface

PurposeThe purpose of this study was to evaluate the antimicrobial effects of photothermal therapy using indocyanine green (ICG) and an 810-nm infrared diode laser on Streptococcus gordonii biofilm attached to zirconia surfaces in vitro.MethodsA biofilm was formed using the static method on zirconia disks placed in a 24-well plate. The biofilms were subdivided into the following six treatment groups: control, commercial photodynamic therapy (PDT), chlorhexidine gluconate (CHX), laser only (L, 810-nm infrared diode), ICG, and laser with ICG (PTT). After treatment, each disk was agitated and the solution with detached bacteria was spread directly on a blood agar plate. Cells were cultured under anaerobic conditions and colony-forming units were counted. Confocal laser-scanning microscopy was used to assess the survival according to the height of the biofilm.ResultsThe PTT, PDT, and CHX groups showed a significant reduction in S. gordonii viability (p<0.05), while the L and ICG groups showed no significant difference compared to the control group (p = 0.32, p = 0.97; respectively). In confocal laser-scanning microscopy images, the PTT, PDT, and CHX groups presented most of the dead bacteria in both the upper and lower levels of biofilm.ConclusionWithin the limitations of this in vitro study, PTT with ICG was effective in significantly reducing the viability of S. gordonii bacteria on zirconia. Further studies are needed to establish a standardized PTT protocol to treat peri‑implant diseases.     

Disinfection efficacy and fracture strength of PMMA denture-based polymer with chlorhexidine,PDT utilizing Rose Bengal and hematoporphyrin,and Er,Cr: YSGG laser

Objective: The study aimed to assess and compare disinfection efficacy and fracture strength of PMMA based DBPs using chlorhexidine (CHX), PDT utilizing Rose Bengal (RB) and hematoporphyrin HPD, and Er,Cr:YSGG laser (ECL) induced antimicrobial action against in-vitro biofilms colonized with C.albicans, S.aureus, S. mutans, and E. coli.Material and Methods: American Type Culture Collection (ATCC) of C.albicans, S.aureus, S. mutans and E. coli were cultured. Forty-eight PMMA-based denture base plates (DBPs) were prepared by heat-cure acrylic resin and contaminated by in-vitro biofilm under-stimulated in-vitro conditions. DBPs were treated with group1; ECL group 2; RB 5µm, group 3; HPD 500 mg/L and group 4; 0.12% CHX (controls) respectively, for the disinfection of biofilms. All photosensitizers (PS) were activated by LED at a different wavelength. Each contaminated DBP was sprayed on all its surfaces with the aforementioned photosensitizers and CHX. One-way analysis of variance (ANOVA) was used to test the efficacy of disinfection and fracture load testing. Tukey multiple comparison tests were performed to compare means of CFU/mL (log10) for exposed E. coli, C. albicans, S aureus, and S. mutans.Results: Specimens in group 1 disinfected with erbium laser, group 3 disinfected with HPD, and group 4 sterilized with chemical disinfection were effective in decreasing bacterial load CFU/mL (log10) against C.albicans, S. aureus, S.mutans, and E. Coli (p>0.05). Intergroup comparison demonstrated ECL, CHX and HPD demonstrated a comparable reduction against C.albicans and S.aureus (p>0.05). Similarly, S.mutans and E.coli were sensitive against all experimental groups (p>0.05). no significant difference in fractural load analysis among the different investigated groups was noted (p>0.05).Conclusion: ECL and HPD photosensitizer revealed a significant reduction in CFU/ml of exposed viable colonies of C.albicans, S.aureus, S. mutans, and E. coli comparable to 0.12% CHX mediated disinfection of PMMA-based DBPs. Irrespective of the type of disinfection no influence of disinfection was noted on the fracture load of PMMA DBPs.     

Determination of optimal effective combinations of antimicrobial substances and the antibacterial photodynamic principle

There are various approaches (disc-diffusion assay, time-kill kinetics assay, post-antibiotic effect, or checkerboard assay) available for the investigation of antibacterial substances, but combinations of these have not been fully investigated, including the combination of antimicrobial photodynamic therapy (aPDT) and conventionally used antibacterial substances. Furthermore, no method has yet been established as a standard procedure to investigate combined effects and to evaluate them in a generally valid and unambiguous way.The focus of the study was on how an antibacterial substance behaves in a combined application with aPDT using TMPyP as the appropriate photosensitizer. For this purpose, the two antiseptics BAC or CHX and the antibiotic CIP were applied to the three bacteria E. coli, S. aureus and E. faecalis in combination with aPDT, each in non-lethal concentrations. The checkerboard method was used to describe and evaluate combined antibacterial effects. The antibacterial effect of a combined application was defined to be effective, if the used doses or conditions completely killed the bacterial culture treated with it.Here a method is presented for the first time, which allows the determination of optimal effective combinations of active doses, abbreviated as OPECC (optimal effective concentration combination). The OPECC defines the required concentrations of an antibacterial substance in combination with aPDT, whereby both combined applied concentrations of the substance and the setting of the aPDT procedure are in the sublethal range of its single application. For the three bacteria investigated, the following findings were obtained in the sublethal concentration range:1) For the combined application of the antiseptics BAC or CHX and aPDT to E. coli, S. aureus and E. faecalis, an OPECC could be determined.2) For the combined application of the antibiotic CIP and aPDT, an OPECC could be determined as well.In each case, an OPECC could be determined. This allows the conclusion that the minimal inhibitory concentration (MIC) of the single application of BAC, CHX, or CIP and aPDT are higher compared to the OPECC of the combined application of BAC_TMPyP, CHX_TMPyP and CIP_TMPyP. The combined application enables the reduction of the individual concentrations for an effective antibacterial effect, whereby the selected test conditions have a subordinate role. Overall, the OPECC will allow the optimization or reduction of the concentration ranges of the investigated substances in binary use. It could be mentioned here, that the synergy principle gives a statement about the considered system of two combined processes (substances), but that the OPECC gives an exact concentration pair at which the bacteria can be effectively combated and that this concentration pair is optimal in the sense of the antibacterial effect. In the future, it will be important to investigate further substances in combination in this way.     

放线菌酮对大鼠脑损伤的神经保护作用

目的：探讨放线菌酮对脑创伤的神经保护作用及其机制。方法：在液压颅脑损伤模型中,观察伤后神经功能、神经病理学改变、细胞凋亡的特征以及凋亡促进基因bax的表达；比较治疗组在液压致伤前5min皮下注射放线菌酮（2.5mg/kg）对上述指标的影响。结果：治疗组伤后行走功能、平衡功能障碍程度明显低于未治疗组（P＜0．01）。治疗组大鼠伤后神经病理学改变减轻，不同脑区各个时间点凋亡细胞数均显著减少，DNA电泳未见凋亡带谱。伤后不同脑区bax蛋白水平升高，放线菌酮可抑制bax蛋白表达。结论：放线菌酮有效地抑制创伤后bax蛋白表达及神经细胞凋亡，减轻神经病理损害，具有神经保护作用。     

Dentin disinfection and adhesive bond strength using modified photoactivated carbon nanoparticles

AimsThe present study aimed to investigate the bond integrity and disinfection efficacy of Methylene blue(MB) alone, MB-PDT (Photodynamic therapy), MB@ carbon nanoparticles (CP)-PDT, and Cr, Cr: YSGG (ECL) against lactobacilli in Caries-affected dentin (CAD)Material and methodsMethods consisted of Shear bond strength (SBS), Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), methods of disinfection, and failure analysis. CAD samples were prepared and biofilm formed on the specimens randomly allocated into five groups based on disinfection. Group 1: CHX; Group 2: MB; Group 3: MB-PDT: group 4: MB@CP-PDT and group 5: ECL. After disinfection Colony forming units were measured and specimens were restored and positioned under a universal testing machine (UTM). Failure analysis was performed using a stereomicroscope. The difference in survival rate was assessed using the Kruskal-Walis test. Mean and standard deviation for bond values after different methods of disinfection was evaluated using analysis of variance (ANOVA) and Post Hoc Tukey. The significance level was p<0.05ResultsMorphological analysis revealed that CPs under SEM are flat discs with edged irregular shapes. EDX analyses show a spike indicating carbon particles by more than 95%. MB@CP-PDT displayed the highest reduction in lactobacillus levels in comparison to the other disinfection methods. The highest SBS was exhibited by the CAD sample disinfected with ECL. The lowest SBS values in CAD specimens after cavity cleansing with MB alone. The predominant failure type in CAD disinfected with MB alone, ECL CHX, MB-PDT, and MB@CP-PDT was adhesive.ConclusionThe use of MB@CP-PDT showed high antibacterial potency against lactobacillus but demonstrated bond values similar to CHX. Use of Er, Cr: YSGG showed considerable effectiveness against lactobacillus along with the highest bond values     

Effect of an experimental antiplaque preparation on salivary microbial counts in military academy cadets refraining from mechanical cleaning of the teeth.

Dental emergencies in the army are mostly due to infections of the teeth, caused by dental plaque micro-organisms. Because practicing normal oral hygiene is restricted during terrain maneuvers, for example, we developed a new antiseptic tablet preparation which can be used to make an antiplaque solution or even chewed and thus mixed with saliva to rinse the mouth. The preparation contains chlorhexidine, fluoride, and xylitol (XYLIHEX) and can be added to the soldier's kit. The efficiency of the preparation on selected oral micro-organisms was tested against mouthwash solutions containing plain chlorhexidine (CHX) and sodium fluoride (F) in 45 military cadets who volunteered to participate in this double-blind cross-over study. The results showed a significant decrease in salivary mutants streptococci after rinsing periods with XYLIHEX and CHX when compared with F (p less than 0.001). Lactobacilli and yeast counts were not affected. The new preparation appeared promising as a new means for improving soldiers' oral hygiene.     

Adjunctive therapies for in vitro carious lesions: Antimicrobial activity,activation of dentin metalloproteinases and effects on dental pulp cells

BackgroundAdjunctive therapies used before dental restorative procedures may encourage carious tissue removal. Beyond promising antimicrobial properties, treatments could positively modulate the dentin-pulp complex while not interfering with restoration survival. Herein, we evaluated a set of substances and their effects on carious lesions and the underlying dentin or pulp cells.MethodsArtificial caries lesions were developed in bovine teeth cavities immersed in Streptococcus mutans and Lactobacillus casei co-cultures. The cavities were treated according to the following groups: Phosphate Buffer Saline (PBS), Chlorhexidine (CHX), Papacárie® (Papain gel), Ozone (O₃), and antimicrobial Photodynamic Therapy (aPDT). After treatments, samples were cultivated to count isolated microbial colonies. The zymography assay evaluated the activity of dentin metalloproteinases (MMP-2 and MMP-9). Cell viability was indirectly assessed on human dental pulp cells after 24, 72, or 120 h, whereas the odontodifferentiation potential was evaluated after ten days of cell culture.ResultsCHX and aPDT led to around 1 log bacterial load reduction. PBS, CHX, and aPDT showed the eventual expression of MMP-2 and MMP-9. Cell viability was reduced (< 30%) after 120 h for all groups compared to the control. CHX, O3, and aPDT induced greater odontodifferentiation (≈ 20% higher) than PBS and papain gel.ConclusionAdjunctive therapies presented little or no biological significance in reducing bacterial load in artificial carious lesions. Although the activation of endogenous metalloproteinases may represent a possible concern for adhesive restorations, some of these treatments may have a positive role in dental pulp tissue repair.     

Fracture strength of Er,Yag laser treated PMMA denture-based polymer (DBP) colonized with C. albicans,S. aureus,S.mutans,and E.coli

AimTo assess and equate the efficacy of different disinfection protocols autoclave, chlorhexidine (CHX), PDT utilizing Rose Bengal (RB), chitosan, and Er, Yag laser and their effect on fracture strength of PMMA denture-based polymer (DBP) colonized with C. Albicans, S. aureus, S.mutans, and E.coli.Material and methodsA total of 50 (n = 10) PMMA DBP were manufactured and adulterated with the American Type Culture Collection (ATCC) of diverse microbial colonies inhabited by C. Albicans, S. aureus, S.mutans, and E.coli. The specimens were subjected to different denture disinfection approaches by randomly distributing in into five groups i.e., Er, Yag laser, RB, autoclave, CHX, and Chitosan, respectively for appraising antimicrobial effectiveness. PMMA fracture load was also assessed and statistical analysis was performed for CFU/mL (log10) of exposed C. Albicans, S. aureus, S.mutans, and E.coli by one-way ANOVA and Tukey's multiple comparison test at a significance level of p < 0.05.ResultsIntergroup comparison disclosed that denture disinfection with Er, Yag laser, autoclave, Chitosan, and CHX (control) validated comparable antimicrobial efficacy to denture against all inspected CFU/mL (log10) (p>0.05). The intragroup comparison revealed that DBP sanitization with Er, Yag laser, autoclave, Chitosan, RB, and CHX substantiated equivalent effective antimicrobial efficacy in plummeting CFU/mL (log10) of S. mutans and E. coli (p>0.05) but in consideration to S.aureus and C.albicans, all groups resulted in declining their count except 5µm RB activated by PDT(p < 0.05). No significant difference was perceived in fracture load of PMMA denture base among Er, Yag laser, RB, chitosan, and CHX (control) (p > 0.05) except autoclave decontamination procedure that indicated the least fracture strength of DBP when disinfected (p < 0.05).ConclusionEr, Yag laser, and Chitosan activated by PDT have the potential to be used as an alternative to chlorhexidine for disinfecting Polymethyl methacrylate denture base as they demonstrated the highest antimicrobial efficacy against E. coli, C. Albicans, S aureus, and S. mutans with optimal fracture load.     

Glass fiber post resistance to dislodgement from radicular dentin after using contemporary and conventional methods of disinfection

AimThe present study aimed to assess the bond integrity of curcumin photosensitizer (CPS) Photodynamic therapy (PDT) on fiber post disinfection bonded to radicular dentin in comparison to the conventional fiber post sterilant used.Materials and methodsFifty human permanent single-rooted premolars were utilized with the crown part sectioned using up to the cementoenamel junction. Root canal preparation was performed followed by canal obturation with gutta-percha (GP) and resin-based sealer. The post space was prepared using peso reamers leaving 4 mm at the apical part of the post space. Fifty glass fiber posts (GFP) were divided into five groups based on the surface disinfectant (n = 10). group 1: Autoclave sterilization (AS) group 2: chlorhexidine digluconate (CHX dig), group 3: CPS solution, group 4: 35% phosphoric acid (PA) gel, and group 5: No disinfection. Cementation was performed using dual-cure self-etch resin cement. Each tooth was sectioned and placed on the universal testing machine. Failure mode was analyzed using a stereomicroscope at 40x magnification. Statistical analysis was performed using one-way analysis of variance (ANOVA) and Tukey multiple comparison tests. (p = 0.05).ResultsIntragroup comparison analysis demonstrated that group 2 in which 2% CHX dig was used as a post-surface disinfectant revealed the highest bond integrity at all three levels. Group 5 where no disinfectant was used to decontaminate the post surface exhibited the lowest bond values. In all the investigated groups, PBS values showed a downward trend from coronal to the apical third of the post space. Group 1 in which AS was used to sterilize the fiber post and group 3 in which CPS was smeared to decontaminate the GFPs surface-displayed comparable outcomes of PBS to group 5 specimens at all three levels. (p > 0.05).ConclusionCHX dig and PA post-surface disinfection displayed a positive impact on bond strength with the radicular dentin. However, CPS and AS do not reveal any effect on the PBS when used for post-decontamination.