Heat and acute dehydration effects on acceleration response in man

1979 ◽  
Vol 47 (1) ◽  
pp. 197-200 ◽  
Author(s):  
S. A. Nunneley ◽  
R. F. Stribley
Keyword(s):  
High Performance ◽  
Rapid Onset ◽  
High Tolerance ◽  
Acceleration Response ◽  
Protective Mechanisms ◽  
Gradual Onset ◽  
Fluid Deficit ◽  
Induced Tolerance ◽  
Mean Time ◽  
G Tolerance

Though heat and dehydration each impair acceleration tolerance, interactions among these stresses have not previously been studied. Seven men were dehydrated in heat by 0, 1, and 3% of body weight before a series of +Gz, gradual-onset centrifuge runs with the capsule first 38 degrees C, then 20 degrees C. Heat alone raised heart rate by 6.5 beats/min independent of other stresses. Dehydration and acceleration appeared to act synergistically in raising HR. Heat lowered relaxed G tolerance by 0.3 G; dehydration tended to lower G tolerance and increased the variability of response to heat. A high-tolerance subgroup (n = 4) could normally sustain +7 Gz for 60 s with anti-G suit and straining, but 3% dehydration reduced mean time to 35 s. Dehydration was associated with a decrease in the loss of plasma volume at 7 G. Heat-induced tolerance loss appears similar for both gradual- and rapid-onset centrifuge profiles. In contrast, dehydration effects are greater in rapid-onset runs, evidence that normal anti-G protective mechanisms can partly counteract the effect of fluid deficit. The results are relevant for crew members of high-performance aircraft, where unexpected diminution of their normally high G tolerance can have disastrous consequences.

scholarly journals Hemodynamic Responses and G Protection Afforded by Three Different Anti-G Systems

2019 ◽  
Vol 90 (11) ◽  
pp. 925-933
Author(s):  
Ross D. Pollock ◽  
Rachel V. Firth ◽  
Jessica A. Storey ◽  
Katherine E. Phillips ◽  
Desmond M. Connolly ◽  
...  
Keyword(s):  
Air Force ◽  
Peripheral Resistance ◽  
Rapid Onset ◽  
Lower Limbs ◽  
Lower Body ◽  
Hemodynamic Responses ◽  
Royal Air Force ◽  
Gradual Onset ◽  
Clear Vision ◽  
G Tolerance

BACKGROUND: UK Royal Air Force fast jet aircrew use three different anti-G systems, however, little objective comparison of the G protection they provide exists. The G-protection afforded by each system and associated hemodynamic responses were investigated.METHODS: Ten subjects performed centrifuge acceleration exposures using Mk-10 (S1) and Mk-4 (S2) five-bladder anti-G trousers (AGT) and full coverage AGT plus pressure breathing for G-protection (PBG; S3). Measurements of relaxed G tolerance (RGT), eye-level blood pressure (BPeye), lower body blood volume (LBV), stroke volume (SV) and total peripheral resistance (TPR) were made during gradual onset runs (GOR) and rapid onset runs (ROR). The subjective effort required to maintain clear vision at +7 and +8 Gz provided an indication of the protection provided by the system.RESULTS: All systems moderated decreases in SV and BPeye and increases in LBV under increased +Gz. S3 provided the greatest mean RGT during GOR (+6.2 Gz) and ROR (+6 Gz), reduced the effort required to maintain clear vision at up to +8 Gz, prevented venous pooling and afforded the greatest rise in TPR. The majority of indices revealed no difference between S1 and S2 although RGT during the ROR was greater with S2 (+0.25 Gz).DISCUSSION: S3 effectively prevented pooling of blood in the lower limbs under +Gz, despite the use of PBG, and offers an advantage over five-bladder AGT. Given the similarities of S1 and S2, it was unsurprising that the majority of indices measured were similar. The objective measurement of hemodynamic parameters provides useful information for comparing the G-protection provided by anti-G systems.Pollock RD, Firth RV, Storey JA, Phillips KE, Connolly DM, Green NDC, Stevenson AT. Hemodynamic responses and G protection afforded by three different anti-G systems. Aerosp Med Hum Perform. 2019; 90(11):925–933.

Relaxed +GZ tolerance in healthy men: effect of age

1978 ◽  
Vol 45 (4) ◽  
pp. 626-629 ◽  
Author(s):  
D. H. Hull ◽  
R. A. Wolthuis ◽  
K. K. Gillingham ◽  
J. H. Triebwasser
Keyword(s):  
Air Force ◽  
Visual Fields ◽  
Rapid Onset ◽  
Healthy Men ◽  
Positive Correlation ◽  
Gradual Onset ◽  
Us Air Force ◽  
The Subject ◽  
Effect Of Age ◽  
G Tolerance

Fifty-three healthy US Air Force aircrewmen, 26–55 yr old, volunteered for a centrifuge study designed to determine the effect of age on relaxed +GZ tolerance. Each was subjected to G forces of gradual and rapid onset, with G tolerance determined by standardized contraction of peripheral visual fields. Of the subject characteristics studied, only age was positively correlated with rapid-onset G tolerance; both age and weight were positively correlated with gradual-onset G tolerance. A combination of age and weight gave a stronger positive correlation with G tolerance (rapid- and gradual-onset) than did either characteristic alone. No significant negative correlations were observed. We conclude that aging may offer some protection from G stress; there is no evidence that aging leads to a decrement in G tolerance.

scholarly journals OP0074 MULTIMORBIDITY CLUSTERS, DETERMINANTS AND TRAJECTORIES IN OSTEOARTHRITIS IN THE UK: FINDINGS FROM THE CLINICAL PRACTICE RESEARCH DATALINK

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 49.1-50
Author(s):  
S. Swain ◽  
C. Coupland ◽  
V. Strauss ◽  
C. Mallen ◽  
C. F. Kuo ◽  
...  
Keyword(s):  
Chronic Conditions ◽  
Index Date ◽  
Latent Class ◽  
Rapid Onset ◽  
Practice Research ◽  
Clinical Practice Research Datalink ◽  
Research Support ◽  
Gradual Onset ◽  
The Uk ◽  
Slow Onset

Background:Multimorbidity (≥2 chronic conditions) escalates the risk of adverse health outcomes. However, its burden in people with osteoarthritis (OA) remains largely unknown.Objectives:To identify the clusters of patients with multimorbidity and associated factors in OA and non-OA populations and to estimate the risk of developing multimorbidity clusters after the index date (after diagnosis).Methods:The study used the Clinical Practice Research Datalink – a primary care database from the UK. Firstly, age, sex and practice matched OA and non-OA people aged 20+ were identified to explore patterns and associations of clusters of multimorbidity within each group. Non-OA controls were assigned with same index date as that of matched OA cases. Secondly, multimorbidity trajectories for 20 years after the index date were examined in people without any comorbidities at baseline in both OA and non-OA groups. Latent class analysis was used to identify clusters and latent class growth modelling was used for cluster trajectories. The associations between clusters and age, sex, body mass index (BMI), alcohol use, smoking habits at baseline were quantified through multinomial logistic regression.Results:In total, 47 long-term conditions were studied in 443,822 people (OA- 221922; non-OA- 221900), with a mean age of 62 years (standard deviation ± 13 years), and 58% being women. The prevalence of multimorbidity was 76.6% and 68.9% in the OA and non-OA groups, respectively. In the OA group five clusters were identified including relatively healthy (18%), ‘cardiovascular (CVD) and musculoskeletal (MSK)’ (12.3%), metabolic syndrome (28.2%), ‘pain and psychological (9.1%), and ‘musculoskeletal’ (32.4%). The non-OA group had similar patterns except that the ‘pain+ psychological’ cluster was replaced by ‘thyroid and psychological’. (Figure 1) Among people with OA, ‘CVD+MSK’ and metabolic syndrome clusters were strongly associated with obesity with a relative risk ratio (RRR) of 2.04 (95% CI 1.95-2.13) and 2.10 (95% CI 2.03-2.17), respectively. Women had four times higher risk of being in the ‘pain+ psychological’ cluster than men when compared to the gender ratio in the healthy cluster, (RRR 4.28; 95% CI 4.09-4.48). In the non-OA group, obesity was significantly associated with all the clusters.Figure 1: Posterior probability distribution of chronic conditions across the clusters in Osteoarthritis (OA, n=221922) and Non-Osteoarthritis (Non-OA, n=221900) group. COPD- Chronic Obstructive Pulmonary Disease; CVD- Cardiovascular; MSK- MusculoskeletalOA (n=24139) and non-OA (n=24144) groups had five and four multimorbidity trajectory clusters, respectively. Among the OA population, 2.7% had rapid onset of multimorbidity, 9.5% had gradual onset and 11.6% had slow onset, whereas among the non-OA population, there was no rapid onset cluster, 4.6% had gradual onset and 14.3% had slow onset of multimorbidity. (Figure 2)Figure 2: Clusters of multimorbidity trajectories after index date in OA (n=24139) and Non-OA (n=24144)Conclusion:Distinct identified groups in OA and non-OA suggests further research for possible biological linkage within each cluster. The rapid onset of multimorbidity in OA should be considered for chronic disease management.Supported by:Acknowledgments:We would like to thank the University of Nottingham, UK, Beijing Joint Care Foundation, China and Foundation for Research in Rheumatology (FOREUM) for supporting the study.Disclosure of Interests:Subhashisa Swain: None declared, Carol Coupland: None declared, Victoria Strauss: None declared, Christian Mallen Grant/research support from: My department has received financial grants from BMS for a cardiology trial., Chang-Fu Kuo: None declared, Aliya Sarmanova: None declared, Michael Doherty Grant/research support from: AstraZeneca funded the Nottingham Sons of Gout study, Consultant of: Advisory borads on gout for Grunenthal and Mallinckrodt, Weiya Zhang Consultant of: Grunenthal for advice on gout management, Speakers bureau: Bioiberica as an invited speaker for EULAR 2016 satellite symposium

Monoisopropylglutathione ester protects A549 cells from the cytotoxic effects of sulphur mustard

1997 ◽  
Vol 16 (11) ◽  
pp. 636-644 ◽  
Author(s):  
Christopher D Lindsay ◽  
Joy L Hambrook ◽  
Alison F Lailey
Keyword(s):  
Cell Viability ◽  
Cell Cultures ◽  
A549 Cell ◽  
High Performance ◽  
Gentian Violet ◽  
A549 Cells ◽  
Rapid Onset ◽  
Neutral Red ◽  
Biochemical Basis ◽  
Sulphur Mustard

1 The A549 cell line was used to assess the toxicity of sulphur mustard (HD), using gentian violet (GV) and neutral red (NR) dyes as indicators of cell viability. It was found that exposure to concentrations in excess of 40 ?M HD resulted in a rapid onset of toxicity. 2 The ability of monoisopropylglutathione ester (MIPE) to protect A549 cells against the effects of a 100 ?M challenge dose ofHD was determined using the NR and GV assays. It was found that MIPE (8 mM) could protect cells against the effects ofHD though MIPE had to be present at the time of HD challenge. Cultures protected with MIPE were two times more viable than HD exposed cells 48 h after HD challenge when using the GV and NR assays to assess viability. Observations by phase contrast microscopy of NR and GV stained cultures confirmed these findings. Addition of MIPE after previously exposing the A549 cultures to HD (for up to 5 min) maintained cell viability at 72% compared to 37% for unprotected cultures, after which time viability fell significantly so that at 10 min there was no difference in viability between the MIPE treated and untreated cultures. 3 Pretreating A549 cultures with MIPE for 1 h followed by its removal prior to HD challenge did not maintain cell viability. Treatment of cultures with HD for 1 h followed by addition of MIPE did not maintain the viability of the cultures, thus the window within which it was possible for MIPE to rescue cell cultures from the effects of HD was of short duration. 4 High performance liquid chromatography was used to determine the biochemical basis of the actions of MIPE. It was found that whilst intracellular levels of cysteine were increased up to 40-fold following treatment of A549 cell cultures with MIPE, levels of reduced glutathione did not rise. The lack of protection seen in cultures pretreated with MIPE for 1 h prior to HD exposure suggests that raising intracellular cysteine levels was not an effective strategy for protecting cells from the effects of HD. The protection observed is probably due to extra cellular inactivation of HD by MIPE.

A SURVEY OF CHECKPOINT/RESTART TECHNIQUES ON DISTRIBUTED MEMORY SYSTEMS

2013 ◽  
Vol 23 (04) ◽  
pp. 1340011 ◽  
Author(s):  
FAISAL SHAHZAD ◽  
MARKUS WITTMANN ◽  
MORITZ KREUTZER ◽  
THOMAS ZEISER ◽  
GEORG HAGER ◽  
...  
Keyword(s):  
High Performance ◽  
Building Blocks ◽  
Memory Systems ◽  
Time To Failure ◽  
Flow Solver ◽  
The Road ◽  
System A ◽  
Node Level ◽  
Mean Time ◽  
Performance Computing

The road to exascale computing poses many challenges for the High Performance Computing (HPC) community. Each step on the exascale path is mainly the result of a higher level of parallelism of the basic building blocks (i.e., CPUs, memory units, networking components, etc.). The reliability of each of these basic components does not increase at the same rate as the rate of hardware parallelism. This results in a reduction of the mean time to failure (MTTF) of the whole system. A fault tolerance environment is thus indispensable to run large applications on such clusters. Checkpoint/Restart (C/R) is the classic and most popular method to minimize failure damage. Its ease of implementation makes it useful, but typically it introduces significant overhead to the application. Several efforts have been made to reduce the C/R overhead. In this paper we compare various C/R techniques for their overheads by implementing them on two different categories of applications. These approaches are based on parallel-file-system (PFS)-level checkpoints (synchronous/asynchronous) and node-level checkpoints. We utilize the Scalable Checkpoint/Restart (SCR) library for the comparison of node-level checkpoints. For asynchronous PFS-level checkpoints, we use the Damaris library, the SCR asynchronous feature, and application-based checkpointing via dedicated threads. Our baseline for overhead comparison is the naïve application-based synchronous PFS-level checkpointing method. A 3D lattice-Boltzmann (LBM) flow solver and a Lanczos eigenvalue solver are used as prototypical applications in which all the techniques considered here may be applied.

scholarly journals A comparative study of low doses of intrathecal ketamine and midazolam with bupivacaine for postoperative analgesia in infraumbilical surgeries

2019 ◽  
Vol 6 (2) ◽  
pp. 197
Author(s):  
Rajabhushanam M. ◽  
Sunil Kumar K. ◽  
Syed Ali Aasim ◽  
Venkatesh S.
Keyword(s):  
Postoperative Analgesia ◽  
Cost Effective ◽  
Rapid Onset ◽  
Spinal Block ◽  
P Value ◽  
Sensory Level ◽  
Hyperbaric Bupivacaine ◽  
First Choice ◽  
Mean Time

Background: Infra-umbilical surgeries may be performed under local, regional (spinal or epidural) or general anaesthesia, spinal block is still a first choice, because of its rapid onset, high quality of blockade, lack of catheter related infection, less failure rate and also cost effective but the duration of block and postoperative analgesia is limited. The purpose of study was to compare the efficacy of adding ketamine to 0.5% hyperbaric bupivacaine with midazolam to 0.5% hyperbaric bupivacaine in elective infraumbilical procedures.Methods: A randomized, single blinded, clinical study. 60 subjects were enrolled from the patients presenting for elective infraumbilical surgeries after following the inclusion and exclusion criteria laid down for the study. Sixty ASA Grade I and II patients undergoing infra umbilical surgeries were randomly divided into one of the two equal groups (n=30).Results: Total 60 patients were included in this study. The mean time to achieve T10 sensory level and modified bromage scale III was prolonged in group M (4.33±1.09, 6.66±1.26 min) as compared to group K (3.3±0.7, 4.96±1.21 min) which was statistically significant (P value <0.05).Conclusions: The present study concludes that addition of intrathecal midazolam to hyperbaric bupivacaine provide very good and prolonged post-operative analgesia without significant intra-operative and post-operative side effects compared to intrathecal ketamine.

scholarly journals Analysis of incapacitation during +Gz induced loss of consciousness

2021 ◽  
Vol 65 ◽  
pp. 91-96
Author(s):  
MD Sharma ◽  
P Biswal ◽  
N Taneja ◽  
A Agarwal
Keyword(s):  
Air Force ◽  
High Performance ◽  
Age Groups ◽  
Rapid Onset ◽  
Loss Of Consciousness ◽  
Video Recordings ◽  
Operational Capabilities ◽  
Significant Difference ◽  
The Mean ◽  
The Difference

Introduction: Occurrence of G induced loss of consciousness (G-LOC) during centrifuge training is a known entity. The Indian Air Force is currently undertaking high G training of its fighter pilots in High Performance Human Centrifuge (HPHC) which has significantly higher operational capabilities. The study aimed to analyse the incapacitation periods and myoclonic jerks associated with G-LOC occurring during HPHC training. Material and Methods: Records of episodes of 161 G-LOC during closed loop Rapid Onset Rates (ROR) runs over a period of 7 years from 2011 to 2017 were analyzed. The video recordings of these G-LOC episodes were assessed in terms of the participant demographics, +Gz onset rates, incapacitation periods, and presence or absence of myoclonic jerks during the G-LOC episodes. Descriptive statistics was applied to analyze the incapacitation periods and the duration of the myoclonic flail movements. Single tailed t-test was used to analyze the difference between the incapacitation periods of the aircrew who suffered myoclonic flail movements and those who did not. One-way ANOVA was carried out to assess the differences in incapacitation periods, if any, between aircrew of different age groups. Significance was set at P < 0.05. Results: Of these 161 episodes of G-LOC, 43.5% were seen in trainee aircrew. The mean Absolute Incapacitation Period (AIP), Relative Incapacitation Period (RIP) and Total Incapacitation Period (TIP) was 6.9 ± 2.3 s, 12.2 ± 4.7 s, and 19.1 ± 5.5 respectively. Age and flying experience did not show any significant effect with any of the incapacitation periods (p>0.05). The TIP correlated better with the RIP than with the AIP (Pearson’s correlation values of 0.9 and 0.52 respectively). Myoclonic flail movements were witnessed in 25.5% of G-LOC episodes with an average duration of 5.3 s and more than 50% occurring at ≥8Gz. The mean duration of RIP was significantly higher (P=0.03) when G-LOC was associated with myoclonic flail movements, whereas, the duration of AIP did not show any significant difference. Conclusion: The shorter incapacitation periods observed in the study compared to that reported in most of the previous studies could be attributed to the faster Gz offset rates of the present HPHC. Episodes of G-LOC having myoclonic movements were found to have higher relative incapacitation periods. Even though these movements were associated with G-LOC occurring at higher Gz levels, the durations were independent of the Gz levels.

scholarly journals Efficient checkpoint/verification patterns

2016 ◽  
Vol 31 (1) ◽  
pp. 52-65 ◽  
Author(s):  
Anne Benoit ◽  
Saurabh K Raina ◽  
Yves Robert
Keyword(s):  
High Performance Computing ◽  
High Performance ◽  
Error Recovery ◽  
The Other ◽  
Critical Problem ◽  
Mean Time Between Failures ◽  
Time Between Failures ◽  
Mean Time ◽  
Performance Computing

Errors have become a critical problem for high-performance computing. Checkpointing protocols are often used for error recovery after fail-stop failures. However, silent errors cannot be ignored, and their peculiarity is that such errors are identified only when the corrupted data is activated. To cope with silent errors, we need a verification mechanism to check whether the application state is correct. Checkpoints should be supplemented with verifications to detect silent errors. When a verification is successful, only the last checkpoint needs to be kept in memory because it is known to be correct. In this paper, we analytically determine the best balance of verifications and checkpoints so as to optimize platform throughput. We introduce a balanced algorithm using a pattern with p checkpoints and q verifications, which regularly interleaves both checkpoints and verifications across same-size computational chunks. We show how to compute the waste of an arbitrary pattern, and we prove that the balanced algorithm is optimal when the platform MTBF (mean time between failures) is large in front of the other parameters (checkpointing, verification and recovery costs). We conduct several simulations to show the gain achieved by this balanced algorithm for well-chosen values of p and q, compared with the base algorithm that always perform a verification just before taking a checkpoint ( p =  q = 1), and we exhibit gains of up to 19%.

The study of Thermal Resistant Enhancement of Siloxane-Modified LED Transparent Encapsulants

2007 ◽  
Vol 1007 ◽  
Author(s):  
Kai-Chi Chen ◽  
Chia-Wen Hsu ◽  
Hsun-Tien Li
Keyword(s):  
Thermal Resistance ◽  
High Performance ◽  
Diglycidyl Ether ◽  
Thermal Treatments ◽  
Curing Agent ◽  
C Storage ◽  
Yellow Index ◽  
Modified Epoxy ◽  
Mean Time

ABSTRACTThermal resistant property of siloxane-modified epoxy compositions designed for long-term and high temperature storage was investigated. In this study, we developed two siloxane-modified epoxy compositions to improve the thermal stability of current epoxy encapsulants. One composition contained silicone epoxy, and the other one was cyclic aliphatic siloxane dianhydride.We selected triglycidyl ether terminated Phenylmethylsiloxnae-co-dimethylsiloxne (GT-1000), which was compatible with the diglycidyl ether of bisphenol A epoxy (Epon-828), to partial replaced the epoxy resin and was cured by liquid anhydride (MHHPA). In the mean time, we also synthesized 5, 5'-(1, 1, 3, 3-tetramethyl disiloxane-1, 3-dilyl)-bis-norborane-2, 3-dicarboxylic anhydride (A1) as a co-curing agent to cure Epon-828.The thermal resistance was studied by measuring the increase of yellow index (ΔYI) after thermal treatments. In 110 °C storage experiment for 1000 h, the ΔYI of GT-1000 0.2 equivalent was 1.51, whereas Epon-828/MHHPA (Comp 1) was 6.74. Moreover, The ΔYI of the composition with higher equivalent GT-1000 was only 2.15 after 2000 hours thermal aging. In the cyclic aliphatic siloxane dianhydride co-curing compositions, when A1 was 0.05 and 0.1 equivalent, the ΔYI was 2.28 and 0.72 after 1000 h, respectively. Compared with Comp 1, both GT-1000 and A1 were effective for thermal resistance.In IR-reflow test, the ΔYI of GT-1000/Epon-828/MHHPA= 0.5/0.5/1 was 0.65 and that of Epon-828/MHHPA was 1.49 after 260 °C for 10 seconds. The results revealed that either the siloxane-modified epoxy or siloxane-modified curing agent had excellent thermal resistant property for high performance LED applications.

scholarly journals An analysis of transcranial doppler to interpret changes in cerebral circulation under +Gz

2020 ◽  
Vol 63 ◽  
pp. 61-64
Author(s):  
S Dinakar ◽  
A Agarwal
Keyword(s):  
Transcranial Doppler ◽  
High Performance ◽  
Cerebral Blood Flow Velocity ◽  
Cerebral Arteries ◽  
Technical Difficulty ◽  
Adult Males ◽  
Non Invasive ◽  
Gradual Onset ◽  
Light Loss ◽  
Rate Profile

Introduction: The use of Transcranial Doppler (TCD) to measure the cerebral blood flow velocity (BFV) is one of the most elusive tasks under +Gz. The reason for this is the technical difficulty in keeping the TCD fixed during acceleration. There is no conclusive principle of the behavior of cerebral blood vessels under +Gz, despite earlier attempts in animal/human studies. In our study, we were able to overcome the technical difficulty and record the cerebral BFV of the middle cerebral artery under +Gz. Material and Methods: Twenty healthy adult males consented to participate in the study. High-performance human centrifuge was used to subject them to +Gz acceleration. The participants were instrumented with electrocardiography, thermistor bead, oxygen saturation probe, non-invasive blood pressure and TCD probe. Relaxed peripheral light loss (PLL) and straining PLL were recorded in a single gradual-onset rate profile. Results: The TCD data were retrieved and the data was plotted. The Doppler waveform varied with a change in +Gz. Pulsatility (Gosling) index was derived. The index increases as Gz level builds up, indicating an increase in arterial resistance. This increase was statistically significant. Conclusion: The understanding, so far, has been based on a presumption of vasoconstriction in the cerebral arteries. However, when monitoring TCD against increasing +Gz, it is not the presence or absence of the waveform that is of significance; however, it is the change in the pattern of the waveform that is noteworthy.

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