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Influence of water evaporation on elastohydrodynamic lubrication with water-containing polyalkylene glycols

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Friction 2024年第10期12卷 2370-2388页

作者： Stefan HOFMANN Thomas LOHNEr Karsten stahl Technical University of Munich School of Engineering and DesignDepartment of Mechanical EngineeringGear Research Center(FZG)Boltzmannstraße 1585748 Garching near MunichGermany

The reduction of frictional power losses in power transmitting gears takes a crucial role in the design of energy-and resource-efficient ***-containing lubricants like glycerol and polyalkylene glycols have shown great potential in achieving friction within the superlubricity regime with coefficients of friction lower than 0.01 under elastohydrodynamic ***,a bio-based production of the base stocks can lead to the development of green ***,one challenge associated with the application of water-containing lubricants to gearboxes is the evaporation of water and its impact on the lubricant *** this study,the influence of water evaporation on elastohydrodynamic friction and film thickness was investigated for three water-containing polyalkylene *** nominal water contents of 20 wt%and 40 wt%and two viscosities were *** results show that the friction increases continuously with higher evaporated water content,while the overall friction level remains low in nearly water-free states.A similar trend is observed for film thickness,where the strong increase in viscosity results in a notable increase in film ***,the sensitivity of friction and film thickness to water evaporation is low for small amounts of evaporated *** allows generous thresholds for permissible variations in water content.

关键词： friction superlubricity aqueous lubrication elastohydrodynamic lubrication(EHL) evaporation polyalkylene glycol

Exploring the effects of coronary artery disease as a preexisting comorbidity on mortality in hospitalized septic patients:a retrospective observation study

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Emergency and Critical Care Medicine 2024年第2期4卷 47-51页

作者： Anmol Multani Greg stahl Kerry Johnson Scott Goade robert D.Arnce College of Osteopathic Medicine Kansas City UniversityJoplinMOUSA Department of Data Improvement Freeman Health SystemJoplinMOUSA Department of Mathematics Missouri Southern State UniversityJoplinMOUSA Department of Pharmacy Freeman Health SystemJoplinMOUSA

Background:Sepsis has high prevalence and mortality rate,and it is imperative to identify populations at risk of poor sepsis *** patients with preexisting chronic comorbidities are shown to have worse sepsis *** identifying comorbidities with greater influence on sepsis progression,we can direct limited resources to septic patients with comorbidities and reduce health care *** comorbidities can impact the risk of developing sepsis and having worse *** artery disease(CAD)is a common comorbidity,especially in the elderly,and a leading cause of death *** wished to investigate the influence of CAD as a comorbidity on sepsis and hypothesized that preexisting CAD would increase mortality in hospitalized septic ***:We conducted retrospective observational study using patient data from Freeman Health System in Joplin,*** analyzed patient records from Freeman Health System database from January 1,2019,to June 30,*** patients were identified using the International Classification of Diseases,Tenth revision sepsis *** identify septic patients with preexisting CAD,we used International Classification of Diseases,Tenth revision codes for *** compared mortality rates for septic patients with and without ***:Two-sample proportion test was conducted to test the difference in mortality between septic patients with and without preexisting *** difference in mortality for the total population was−0.016(P=0.553).In the male and female subgroups,the differences in mortality were 0.0122(P=0.739)and−0.0511(P=0.208),*** differences in mortality in patients aged 40 to 64 years and 65 years and older were−0.0077(P=0.870)and 0.0007(P=0.983),*** statistical tests failed to find significant differences when comparing septic patients with and without preexisting *** was no significant difference in the age and sex ***:Our study showed that CAD alone was n

关键词： Comorbidity Coronary artery disease Inflammation Mortality rate in sepsis prognosis Sepsis

running‑In Behavior of Wet Multi‑plate Clutches:Introduction of a New Test Method for Investigation and Characterization

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Chinese Journal of Mechanical Engineering 2020年第2期33卷 152-160页

作者： Katharina Voelkel Hermann Pflaum Karsten stahl Gear research Centre(FZG) Technical University of MunichGarchingGermany

Wet multi-plate clutches are relevant components of modern drivetrain applications,not only in terms of function but also safety and *** at the beginning of their lifetime,distinct changes of the friction behavior may occur and make the actuation of the clutch *** transcript describes the typical running-in behavior of wet multi-plate clutches and gives a general definition for running-in of ***,a new test method to systematically investigate the running-in behavior of clutches is *** test method contains a test procedure to characterize the running-in behavior on different load ***,a multi-stage procedure to evaluate and characterize the running-in behavior of clutches with mathematical approaches and new characteristic values is *** quality of the test method is demonstrated on the example of three different tribological systems from dual clutch transmissions(DCT)and automatic transmissions(AT)application using paper friction linings.

关键词： Clutch running-in Test method Paper friction lining

On the experimental characterization of the fluid volume influence on the friction between rough surfaces

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Friction 2023年第7期11卷 1334-1348页

作者： Lukas stahl Michael MÜLLEr Georg-Peter OSTErMEYEr Institute of Dynamics and Vibrations Technische Universität BraunschweigBraunschweig 37106Germany

The load-bearing behaviour of lubricated contacts depends primarily on the normal force,the relative velocity,and the ***,with the aid of the Stribeck curve,it is usually well possible to characterize whether hydrodynamics,mixed friction,or boundary friction is more likely to be *** fact that the load regime can also depend on the fluid quantity is obvious,but has hardly been systematically investigated so *** for contacts with microscopic roughness,the defined application of a very small amount of fluid is a very challenging *** this paper,a very fundamental study shows how a pin-on-disc tribometer can be used to achieve the transition from dry friction via mixed friction to predominant hydrodynamics by the amount of supplied *** experiments are carried out on samples filed with different *** addition,the simultaneous influence of partial filling and normal force as well as relative velocity is also *** good reproducibility has been practically reached over the entire range of the *** the quantities for the coefficient of friction(COF),it was concluded that close to full filling,a reduction of the fluid quantity has a similar effect on the COF as the reduction of the *** property goes along with the common theory of starved lubricated *** behaviour was not observed to the same extent for the normal *** the vicinity of smaller fluid quantities,the COF increases very rapidly with further reduction in fluid quantity,far more disproportionately than that with reduction in *** a deeper understanding of this problem,various practical issues such as idling or the run-up process in bearings can also be studied in a more focused manner.

关键词： starved lubrication Stribeck curve pin-on-disc tribometer fluid supply experimental studies

Numerical Visualization of Grease Flow in a Gearbox

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Chinese Journal of Mechanical Engineering 2023年第2期36卷 220-233页

作者： Hua Liu Florian Dangl Thomas Lohner Karsten stahl School of Engineering&Design Department of Mechanical EngineeringTechnical University of MunichGear Research Center(FZG)BoltzmannstraBe1585748 Garching near MunichGermany

Lubricating greases are widely used in *** gear drives and gearboxes with difficult sealing *** efficiency and heat balance of grease-lubricated gearboxes depend strongly on the lubrication mechanisms channeling and circulating,for which the grease flow is *** computational fluid dynamics opens up the possibility to visualize and understand the grease flow in gearboxes in more *** this study,a single-stage gearbox lubricated with an NLGI 1-2 grease was modeled by the finite-volume method to numerically investigate the fluid *** show that the rotating gears influence the grease sump only locally around the *** a low grease fill volume,the rotation of the gears is widely separated from the grease *** a high grease fill volume,a pronounced geargrease interaction results in a circulating grease flow around the *** simulated grease distributions show good accordance with high-speed camera recordings.

关键词： Lubrication Grease Transmission Gearbox Computational fluid dynamics

Challenges in determination of microscopic degree of cleanliness in ultra-clean gear steels

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Journal of Iron and Steel research International 2022年第10期29卷 1583-1600页

作者： D.Fuchs T.Tobie K.stahl Gear research Center(FZG) Technical University of Munich85748 GarchingGermany

Shot-peened,case-hardened gears can fail in the tooth root due to crack initiation below the surface of the steel ***,the crack is initiated at a non-metallic inclusion in the center of a so-called *** failure type can lead to a reduced endurance fatigue limit of the *** is for this reason that,over the last decade,much effort has been invested by steel manufacturers to reduce the non-metallic inclusion content of gear steels so as to mitigate or even completely prevent such crack *** ultra-clean gear steels were achieved by various measures in the steel production ***,as a result,the remaining non-metallic inclusions are inhomogeneously distributed in the steel volume in terms of both size and ***,due to the inhomogeneity of ultra-clean steels,the question arose if the values derived according to the standards are still representative of ultra-clean steel *** results show that the standards can still be applied,but more effort must be *** determine the degree of cleanliness,six microsections are currently evaluated according to steel test specification(SEP)1571,method *** is shown that an examination of 24 microsections starting from size class 0 seems beneficial to get more reliable and comparable results of the degree of cleanliness of these ultra-clean gear *** addition,it is shown that a high degree of cleanliness has been achieved for all steel batches investigated with the measures taken in the steel production process.

关键词： Degree of cleanliness Non-metallic inclusion Evaluation of inclusion SEP 1571 DIN 50602 Ultrasonic immersion testing Ultra-clean gear steel Gear

Medical therapy for spermatogenic failure

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Asian Journal of Andrology 2012年第1期14卷 57-60,176页

作者： ranjith ramasamy Peter J stahl Peter N Schlegel Department of Urology Weill Cornell Medical College New York NY 10065 USA

Medical treatment of men with primary spermatogenic failure remains largely ineffective in contrast to those with secondary testicular failure. Treatment has been attempted with a multitude of agents ranging from hormones to nutritional supplements （antioxidants）. While some studies have demonstrated benefit to some treatments, no treatments have consistently demonstrated efficacy nor has it been possible to reliably identify patients likely to benefit. Idiopathic spermatogenic failure likely results from multiple discrete defects in sperm production that are as yet unidentified. A better understanding of these defects will yield more effective treatment options and appropriate triage of patients to specific therapeutic regimens. This review focuses on the rationale and current evidence for hormonal and antioxidant therapy in medical treatment of male infertility, spermatogenic failure in particular. Although empiric medical therapy for spermatogenic failure has been largely replaced by assisted reproductive techniques, both treatment modalities could play a role, oerhaos as combination therapy.

关键词： antioxidant hormones male infertility sperm spermatogenesis spermatogenic failure testicular failure

Androgen receptor gene CAG and GGN repeat lengths as predictors of recovery of spermatogenesis following testicular germ cell cancer treatment

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Asian Journal of Andrology 2017年第5期19卷 538-542页

作者： Karolina Bogefors Yvonne Lundberg Giwercman Jakob Eberhard Olof stahl Eva Cavallin-stahl Gabriella Cohn-Cedermark Stefan Arver Aleksander Giwercman reproductive Medicine Centre Skane University Hospital Malmo Sweden Department of Oncology Skane University Hospital Malmo Sweden Department of Translational Medicine Lund University Malmo Sweden Department of Oncology Skane University Hospital Lund Sweden radiumhemmet Karolinska HospitalStockholm Sweden Centre of Andrology and Sexual Medicine Karolinska Hospital Stockholm Sweden

Spermatogenesis is an androgen-regulated process that depends on the action of androgen receptor （Ar）. Sperm production may be affected in men treated for testicular cancer （TC）, and it is important to identify the factors influencing the timing of spermatogenesis recovery following cancer treatment. It is known that the CAG and GGN repeat numbers affect the activity of the Ar; therefore, the aim of this study is to investigate if the CAG and GGN polymorphisms in the Ar gene predict recovery of sperm production after TC treatment. TC patients （n = 130） delivered ejaculates at the following time points： postorchiectomy and at 6, 12, 24, 36, and 60 months posttherapy （TO, T6, T12, T24, T36, and T60）. The CAG lengths were categorized into three groups, 〈22 CAG, 22-23 CAG, and 〉23 CAG, and the GGN tracts were also categorized into three groups, 〈23 GGN, 23 GGN, and 〉23 GGN. At T12, men with 22-23 CAG presented with a statistically significantly （P = 0.045） lower sperm concentration than those with other CAG numbers （8.4 × 10^6 ml^-1 vs 16 × 10^6 ml^-1; 95% CI： 1.01-2.65）. This association was robust to omitting adjustment for treatment type and sperm concentration at TO （P= 0.021; 3.7× 10^6 ml^-1 vs 10 × 10^6 ml^-1; 95% CI： 1.13-4.90）. The same trends were observed for total sperm number. The least active Ar variant seems to be associated with a more rapid recovery of spermatogenesis. This finding adds to our understanding of the biology of postcancer therapy recovery of fertility in males and has clinical implications.

关键词： androgen receptor CAG and GGN repeat sperm number testicular cancer

Update on acute myeloid leukemia stem cells:New discoveries and therapeutic opportunities

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World Journal of Stem Cells 2016年第10期8卷 316-331页

作者： Maximilian stahl Tae Kon Kim Amer M Zeidan Section of Hematology Department of Internal MedicineYale School of Medicine

The existence of cancer stem cells has been wellestablished in acute myeloid leukemia. Initial proof of the existence of leukemia stem cells(LSCs) was accomplished by functional studies in xenograft models making use of the key features shared with normal hematopoietic stem cells(HSCs) such as the capacity of self-renewal and the ability to initiate and sustain growth of progenitors in vivo. Significant progress has also been made in identifying the phenotype and signaling pathways specific for LSCs. Therapeutically, a multitude of drugs targeting LSCs are in different phases of preclinical and clinical development. This review focuses on recent discoveries which have advanced our understanding of LSC biology and provided rational targets for development of novel therapeutic agents. One of the major challenges is how to target the selfrenewal pathways of LSCs without affecting normal HSCs significantly therefore providing an acceptable therapeutic window. Important issues pertinent to the successful design and conduct of clinical trials evaluating drugs targeting LSCs will be discussed as well.

关键词： Leukemia stem cells Cancer stem cells Acute myeloid leukemia Stem cell niche Xenotransplantation Plerixafor NF-κ B C-X-C chemokine receptor type 4