**5. Conclusions**

To our knowledge, this is the first study that demonstrated a cytokine-dependent increase in the gene expression of TRPA1, TRPV2, and TRPV4 and a decrease in the gene expression of TRPC6 and TRPV1 in human IVD cells. Although TRPA1 and TRPV1 are commonly associated with inflammatory pain, their activation in inflamed IVD cells did not have profound pro-inflammatory and catabolic effects. Instead, TRPA1 expression and activation was associated with ECM metabolism. Future studies will use targeted gene editing techniques to elucidate the exact role of TRPA1/TRPV1 in DDD.

#### **Supplementary Materials:** Supplementary materials can be found at http://www.mdpi.com/1422-0067/20/7/ 1767/s1.

**Author Contributions:** T.K. performed cell culture experiments, calcium flux analysis and drafted part of the manuscript. J.Z. performed cell culture experiments. M.V. performed cell culture experiments. A.S. performed tissue analyses. W.K.T. and V.Y.L. performed and evaluated FAST staining. K.B. and Z.H. secured the mouse experiments. L.A.A. provided fetal IVD cell lysates. O.N.H. and J.K. provided human IVD samples and clinical expertise. O.K. performed cell culture experiments, supervised the study and drafted parts of the manuscript. K.W.-K. supervised the study and conceived funding. The authors declare no conflict of interest.

**Acknowledgments:** This study was funded by the Swiss National Science Foundation (SNF PP00P2\_163678/1), the Spine Society of Europe (Eurospine 2016\_4), and Hungarian grants GINOP-2.3.2.-15-2016-00048 "Stay Alive" and EFOP 3.6.2. "Live longer". We thank H. Greutert for technical assistance in the study.

**Conflicts of Interest:** The authors declare no conflict of interest.


**2.3 Astronomy telescope science requires nano-accuracy optics in large scale**

In order to improve the resolution of astronomical telescopes, the desired tendency is to enlarge the aperture of the telescope and achieve the diffraction limited image by use of

Control of surface slope error is especially important in the fabrication of far off-axis aspheres used in grazing incidence x-ray applications. Incoherent x-rays act much like bullets in reflecting off of aspheric surfaces. Slight deviations in surface slope, on the order of fractions of a micro-radian, are sufficient to reduce the quality of the focal spot in long synchrotron beam lines. The stringent requirements for these precision optical components have stimulated research into new measurement methods for spheres and aspheres, and new sophisticated optical measurement instruments are rapidly evolving. A specially designed nano-accuracy profiler for synchrotron optics is urgently needed. It should be also

able to measure mid-spatial frequencies and be able to test strongly curved surfaces.

metrology instrumentation from the micro-accuracy level to the nano-accuracy level.

Since the early 1980s, when the first and second-generation synchrotron light sources came on-line, the requirement for RMS slope error tolerance of SR optics has dropped from 5 μrad to 100 nrad as the desired focal spot size at the beam line end-station has gone from 10µm to 1 nm (Table 1). These continual machine improvements have driven the development of the

Years Slope error requirement Spot size 1980s 5 μrad 10 μm 1990s 1 μrad 1 μm 2011 for NSLS II 100 **nrad 1 nm**

X-ray free electron lasers (XFEL) and EUV lithography require a variety precise of optics with nano-radian accuracy as well. For example, "elliptical mirror with 0.21 μrad rms accuracy is required for XFEL oscillator" (Kim, K., 2009) and "0.1 μrad accuracy mirror is required for FEL focusing" (Assoufid, L. et al.; Minura et al., 2008). In the case of extreme ultra violet lithography (EUVL) "Neither the figure errors nor the roughness of mirrors for

In order to improve the resolution of astronomical telescopes, the desired tendency is to enlarge the aperture of the telescope and achieve the diffraction limited image by use of

**2.3 Astronomy telescope science requires nano-accuracy optics in large scale**

Fig. 1. K-B elliptical mirrors for nanometer spot focusing

Table 1. The requirements of slope error and spot size

**2.2 X-ray free electron lasers (XFEL) and EUVL Lithography**

the imaging system must exceed a few angstroms" (Soufli, R., 2011).

perfect optics. This leads to the application of optics with nano-accuracy. This is the new challenge to manufacturing and metrology. Following quoted contents is the clear examples for describing these demands.

"The NASA Science Missions Directorate seeks technology for nano-accuracy metrology on NASA SBIR AND STTR 2011 Program Solicitations. Following are some requirements for telescopes: "Metrology instruments should have 10 nm or better surface height resolution and span at least 3 orders of magnitude in lateral spatial frequency for Optics Manufacturing and Metrology of Telescope Optical Surfaces" and "In situ metrology systems that can measure optics and provide feedback to figuring/polishing instruments without removing the part from the spindle". "NASA is preparing potential future space telescopes, which have very specific mirror technology needs. UV/optical telescopes require 1 to 3 meter class mirrors with < 5 nm rms surface figures. IR telescopes (such as SAFIR/CALISTO) require 2 to 3 to 8 meter class mirrors with cryo-deformations < 100 nm rms. X-ray telescopes (such as GenX) require 1 to 2 meter long grazing incidence segments with angular resolution < 5 arc-sec down to 0.1 arc-sec and surface micro-roughness < 0.5 nm rms." (NASA NASA SBIR and STTR 2011 Program Solicitations)


**2. Material and methods: low-cost and climate-smart irrigation technology**

The experiment was carried out in northern Ethiopia and the results from this field work served as the data for several theses done at the University of Mekelle. The water seeps out through the micro-pores of the clay pots with relatively slow flow and larger surface wetting time, and thus promotes a greater area of coverage around the roots of plants. Contrarily, perforated clay pots leak water faster through the macro- and micro-pores and have relatively shorter wetting time and smaller area coverage.

On the other hand, the difference between perforated bars and round ones was simply the shapes of the pots which has to do with the area of coverage along the rows of the Swiss chard plant. Round types of pots were not as suitable as bar types (of the same volume) for rows of Swiss chard crops due to their wetting area coverage along the two sides of the bar.

Therefore, among the tested clay pot designs, the bar-shaped perforated clay pot designs were evaluated as best in terms of biomass yield and economic water-use efficiency. The water-use efficiency, economic aspects, and biomass for the perforated bar clay pot design were better than that of the bucket irrigation system. The other advantages of perforated bar clay pots over the bucket type is that the water source is inside the soil thus evaporation is almost zero and there is also less probability of occurrence of leaf disease due to wetting, and this ultimately improves the biomass and water-use efficiency.


*Article* **Effect of Multi-Walled Carbon Nanotubes on Strength and Electrical Properties of Cement Mortar**

**Elena Cerro-Prada \*,†, Rosalía Pacheco-Torres † and Fernando Varela †**

Construction, Infrastructure and Transportation Department, Universidad Politécnica de Madrid (UPM), Alfonso XII, 3, 28014 Madrid, Spain<EMAIL_ADDRESS>(R.P.-T<EMAIL_ADDRESS>(F.V.)

**\*** Correspondence<EMAIL_ADDRESS>Tel.: +34-91-067-4612

† These authors contributed equally to this work.

**Abstract:** This work aims to investigate the effects of multi-walled carbon nanotubes (MWCNTs) on the strength and electrical properties of cement mortar. MWCNTs were added to cement mortar in four different concentrations: 0.00 wt.%, 0.01 wt.%, 0.015 wt.%, and 0.02 wt.% by the mass of cement. The consistency, density, setting time and compressive and flexural strength of mixes were tested and analyzed at 28 and 90 days curing time. Mechanical performance tests confirm an increase of 25% and 20% in the ultimate compressive and flexural strength respectively, which results from MWCNT 0.02 wt.% loading at 90 days curing time. The resistivity measurements in mortars with 0.01 and 0.015 wt.% MWCNT loading result up to 10% decrement at both 28 and 90 days curing. Activation energy calculations show fully accordance with these statements, resuming that 0.01 wt.% MWCNT appears to be the most effective loading scheme to produce certain conductivity enhancement in cement mortar.

**Keywords:** multi-walled carbon nanotubes; cement-based materials; flexural strength; compressive strength; electrical resistivity; activation energy