Environmental Stress Cracking - Science topic

Yes, currently I'm writing about Indonesian's point of view towards the Netherland post-colonialization. I've so many interesting things. Hit me up for the cooperation

ACI report ACI 231 Report on Early-Age Cracking: Causes, Measurement, and Mitigation is available from ACI web site. Key causes include autogenous shrinkage, drying shrinkage, and subsidence cracking, in addition to any poor design and construction issues. Proper curing is critical to avoiding early age cracking. Mitigation strategies include internal curing (lightweight aggregates or superabsorbent polymers), shrinkage-reducing admixtures, and coarser cements (see the work/advocacy of Richard Burrows in the US).

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Published: 14 August 2017

Cardiorespiratory optimization during improvised singing and toning

N. F. Bernardi, S. Snow, …A. Lehmann Show authors

Scientific Reports volume 7, Article number: 8113 (2017) Cite this article

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Hello, I would like to ask something. I want to isolated motor neurons from mice hippocampus and spinal cor. is it possible to freeze this tissues and then do the isolation after some time? Our mice might die in the following days and i am

wairing for some materials to come.

bests,

Dear s. J Kim

These tutorials might be useful for you, have a look:

1. https://www.youtube.com/watch?v=-mD3bGD3Nbc

2. https://www.youtube.com/watch?v=S8aaMkqtxXw

3. https://www.youtube.com/watch?v=Iat_fcIA3_Y

Kind Regards

Dear Milad

The phenomenon of SCC normally occurrs in polycrystalline metallic alloys that are succeptible to a combined of corrosion,i.e.,chemical dissolution, and a tensile deformation. Therefore,the possibility of SCC of PLA is slim to impossible .

Dear Fayrouz,

Due to the limited number of soil tests and the measurements errors, there are some uncertainties in the determined Kv and Kh. According to the reported data in literature, the CoV of these two properties could be very big, so multiplying them by 10 is acceptable.

If you work in saturated steady state flow conditions, the Kv and Kh are indeed the most important properties for the PWP. The following ideas are maybe useful for you:

1. Use some empirical equations to predict the Hydraulic Conductivity so that you can have a range for respectively Kh and Kv

2. Modify the ratio of Kh/Kv. Since embankments are usually constructed by layers, Kh is normally significantly lager than Kv, and the ratio is related to the compaction, consolidation etc .

3. Consider the spatial variation of these two properties inside the embankment

Best regards,

Xiangfeng

Dear Mario,

RCP-Rapid crack propagation (RCP) is a phenomenon in which a long fast-moving brittle crack can propagate in a material body. Cracking of glass plates and frozen lakes is an example of RCP. RCP can also occur in pipes. Cast iron pipes and plastic pipes under certain conditions may also experience this phenomenon. Cracks are thought to initiate at internal defects on an impact of impulse event and can travel long distances quickly. RCP occurs in pressurized systems with enough stored energy to drive cracks faster than energy is released. Cracks tend to have a smooth fracture surface. RCP is affected by temperature, energy driving force, material, pipe size and processing efforts.

Unstable crack occur at load control, when the maximum load is reached, i.e. as soon as the preceding stable growth tends to occur under constant load.

(a) RCP can occur at fatigue striation load and material can get failed. There are fluctuations of stress. Maximum load is not required. There is no constant load. it can be instant fail.

Unstable crack growth occurs when the maximum load is reached, i.e. as soon as the preceding stable growth tends to occur under constant load.

(b) RCP occurs in pressurized systems with enough stored energy to drive cracks faster than energy is released.

For unstable crack, the stress-strain energy released, together with the energy supplied from the outer load goes to kinetic energy and to what is required by the dissipative region at the crack edge to sustain crack growth.

(c) RCP is smooth surface while unstable depicts brittle surface.

(d) RCP or Stable- Onset of stable crack growth (RCP) occurs at point S and fracture occurs at point F.

Unstable- During unstable crack growth, the stiff machine cannot supply the energy needed for dissipation in the crack edge region, and therefore all this energy is supplied by energy release from the stress-strain field in the specimen.

(e) RCP- RCP can be characterized by high crack speed, smooth surface with large plastic deformation, wavy propagation of the crack along the extrusion direction. It can be described by LEFM parameters, dynamic fracture resistance and dynamic fracture toughness. RCP is most common in plastic pipe as the majority of field failures in piping are attributable to slow crack growth (SCG) fractures or rapid crack growth. Shape is almost uniform. The crack edge generally accelerates to a very high velocity, often several hundred meters per second, and sometimes to a few thousand meters per second. The energy required for conversion from a static to a dynamic state of the structure is provided by stress-

Unstable- Shape of a small crack is generally non‐uniform growth. In addition, the deceleration and subsequent acceleration of crack growth corresponds to the transition from unstable to stable crack growth. Strain energy release from the body, sometimes assisted by energy supply from the loading device.

Ashish

We use gelatin from cold-water fish skin (Sigma) for murine ESC cultivation.

For human iPSCs we get much better results with Lamin521 (Biolamina)

As William recommended, check pluripotency status to find best coating strategy.

For such a small engine you should expect the best efficiency as high as ~20%, in any case not higher as 25%. This will be crucial for efficiency of your genset. The rest values of efficiency can be higher as 90%. It concerns BLDC, its inverter (working as rectifier) and DC-DC converter. Other thing is efficiency of a battery, it depends of its type (lead-acid, NiMH, Li-ion), sometimes of charging rate too (NiMH).

I think that this paper will help you sir

Hi,

I am sorry to tell you that it takes more than 40 days when you use human cells. Its depend on which stage of differentiation you start (ESC, hiPSC; NSC, early neural progenitors (eNP), neural progenitors (NP)).

When you start from ESC, hiPSC at the undifferentiated stage you have to obtain:

1. Neural roset(NE) from hiPSC, ESC (~ 15-21 days);

2. Select neural rosettes(NE) and prepared expansion of neural stem cells (NSC) (~ 6 weeks) to get the stable NSC phenotype;

3. Early neural progenitors(eNP) from NSC (~21 days);

4. Neural progenitors (NP) from eNP (~14 days);

5. Mature neurons from (NP) (~90days);

I use this protocol for hiPSC neural differentiation. It takes a long time, but at the stage of NSC, you can freeze the cells. Freezing in later stages of differentation (eNP, NP) is not recommended.

Good luck!

Since neither previous answer addressed the actual question, I will answer it.

Standard FBS is absolutely fine for the culture of murine fetal fibroblasts. For such cultures, the only difference will be price.

In my specialty (ICU), I would say that acute AF in context of sepsis, vasoactive medications, central lines, electrolyte imbalance, homeostatic disturbance, haemodynamic instability - all this means that AF in critically ill patients is a secondary problem. Despite no consensus yet, most intensivists do not recommend long term anticoagulation if one episode with no history of pAF.

see this paper

Do you suspect that your inducible gene might cause differentiation? Is there any cause to think the gene is turned on by the presence of Tet (sometimes found in FBS - which would be present of you're culturing your hPSCs on MEFs). You could check for expression of your gene first to determine if it's leaky or not. If you think this is the problem, you might want to go with feeder-free I'm culturing my hPSCs in E8; a bit different to work with, but it definitely works. Looking for certified Tet-free FBS for your MEFs is another way to go.

Dear Saleh,

Thank you very much for your reply but I want to borrow it from someone in India asap. I hope you can understand my concern. 

Cheers !

Since the difference are relatively small and the tendency is not evident (e.g. initially decreased and then increased stiffness after fatigue), I would be worried that this has more to do with scatter and uncontrolled test parameters than real deterministic behaviour due to fatigue damage. Also, were these values the results of a single test at each number of cycles or the average of multiple tests? I think that without information on the inherent variability of the natural frequency measurement, very little can be said.

You also need to be aware that with polymer composites, temperatuer may have a strong influence on the stiffness and damping properties of the structure, so you need to make sure that the test environment is quite steady between trials. You would have to at least report test temperature with your data and also ideally report some sensitivity study on possible parasitic effects such as those of temperature,

Also beware that polymer (such as the matrix, but also adhesives) age and that their stiffness changes with aging. However, the load history and temperature/moisture history also influence the aging characteristics. Therefore, simply performing the same test on the same undamaged part after aging may change the natural frequency even in the abscence of damage.

I think the idea of studying known damage states (that would be reresentative of real damage accumulation) to start with would definitely be advisable.

Best regards,

Laurent

If you are looking for the literature about the description of cracking with examples of fatigue fractures (ductile, brittle) and the mechanisms of initiation and propagation one of the best in my mind is "ASM Handbook - vol. 12 Fractography" This book is mainly about the fractography of fractures but includes also many interesting information concerning crack propagation. If you are looking for quantative description of crack propagation look for any book about fatigue fracture or fracture mechanics (it depends on the approach which do you want to apply)

thank you for your suggestions