Step-like Behavior Research Articles

Electrical characteristics of ZnO–SnO2 composites with emphasis on their frequency dependence as a function of SnO2 content

In this experimental work, a well-behaved ZnO-based composite varistor, containing ZnO as a filler and SnO2, high-density polyethylene, and multi-walled carbon nano-tube as additives has been introduced. Samples were prepared using the hot-press method at a pressure of 60 MPa and temperature of 140 °C. Findings indicate that the samples with 92% ZnO have the highest nonlinear coefficient around 21 at the breakdown field of 230.8 × 104(Volt/m). By increasing SnO2 content upto 5%, the breakdown field, nonlinear coefficient, and potential barrier height increase and reach to their maximum values of 230.8 × 104(Volt/m), 21, and 0.71 eV, respectively. However, by further increasing SnO2 content to 8%, these properties decrease. According to the Maxwell-Wagner effect, the frequency-dependent behavior of samples showes that the relative dielectric constant and dielectric loss decrease drastically at frequencies less than 1 kHz. Both parameters show a step-like behavior at the frequency range of 2600–2800 kHz and 4200–5000 kHz.

Multifunctional behaviour in B-site disordered double perovskite EuPrCoMnO6

We report magnetic, transport, dielectric, and complex impedance of polycrystalline double perovskite EuPrCoMnO6 which crystallizes in disordered orthorhombic phase with space group Pnma. The DC magnetization shows two successive ferromagnetic transitions around 146 K and 138 K. The temperature and magnetic field variation of DC-susceptibility suggest the existence of Griffith phase and spontaneous exchange bias. AC susceptibility measurement shows a glassy dynamic behaviour near ferromagnetic transition. Further, a re-entrant glassy dynamic state is seen at a low temperature around 40 K. Temperature-dependent resistivity shows semiconducting/insulating nature, which gets increased under the application of magnetic field, showing positive magnetoresistance. The dielectric study shows usual frequency-dependent step-like behaviour with a colossal dielectric constant near room temperature. The complex impedance study shows both grain and grain boundary contribute to the electrical properties. The observed properties suggest the material can be used for spintronic devices and high dielectric applications.

Effect of cation substitutions in Y-type Ba0.5Sr1.5Me2Fe12O22 hexaferrites on the magnetic phase transitions

We investigated the magnetic properties and magnetic phase transition in Y-type Ba0.5Sr1.5NiMgFe12O22 hexaferrite powder prepared by citrate sol-gel spontaneous combustion. The saturation magnetisation value of 32 emu/g at 4.2 K was lowered to 24 emu/g at 300 K. The magnetisations curves did not saturate even at a magnetic field of 50 kOe for both temperatures - 4.2 K and 300 K. A step-like behaviour appeared in the initial magnetisation curve at 4.2 K. A magnetic phase transformation from a spiral magnetic ordering to a conical spin one was observed at 40 K.

FORC-Diagram Analysis for a Step-like Magnetization Reversal in Nanopatterned Stripe Array.

The fabrication approach of a magnonic crystal with a step-like hysteresis behavior based on a uniform non-monotonous iron layer made by shadow deposition on a preconfigured substrate is reported. The origin of the step-like hysteresis loop behavior is studied with local and integral magnetometry methods, including First-Order Reversal Curves (FORC) diagram analysis, accompanied with magnetic microstructure dynamics measurements. The results are validated with macroscopic magnetic properties and micromagnetic simulations using the intrinsic switching field distribution model. The proposed fabrication method can be used to produce magnonic structures with the controllable hysteresis plateau region’s field position and width that can be used to control the magnonic crystal’s band structure by changing of an external magnetic field.

Experimental method to determine specific heat capacity and transition enthalpy at a first-order phase transition: Fundamentals and application to a Ni-Mn-In Heusler alloy

A new method that characterizes thermal properties during a first-order phase transition is described. The technique consists in exciting the sample by a series of constant frequency thermal pulses which one in every N pulses –N is a small number like four—being exceedingly large in amplitude. This pulse induces phase transformation which is inhibited during the following smaller pulses due to thermal hysteresis. That way the specific heat capacity for a given mixture of phases can be determined. The results obtained are independent of experimental parameters like the rate and the amplitude of the pulses, unlike what happens in other calorimetric techniques. The method also provides the enthalpy excess by analysing the energy balance between the dissipated heat and the heat flowing during each pulse of measurement.The protocol is tested to analyse the phase transitions of a Heusler alloy Ni50.53Mn33.65In15.82. The paramagnetic-ferromagnetic transition for the austenite phase is continuous and the specific heat capacity shows a lambda anomaly. The martensitic phase transition shows a first-order character and the specific heat capacity follows a step-like behaviour.

Steplike Behavior in Grain-Size-Dependent Optical Emission of Plasma Induced by Laser-Ablating Granular Material

Optical emission of plasma induced by a pulsed laser ablating the surface of a randomly packed granular (RPG) material in air is investigated experimentally, taking sieved copper microspheres with discrete diameters, d, ranging from 49 to 390 \textmu{}m as examples. We find a steplike phenomenon (also called a critical-like phenomenon) in the dependence of plasma emission on the grain size: when d is less than a critical size, only weak emissions are detected; however, when d exceeds the critical size, the emissions abruptly become at least 5 times stronger. Such a phenomenon can be explained by considering the RPG material as a non-Newtonian fluid with a yield stress and an effective viscosity. Specifically, in the range of the grain size above (below) the critical value, the RPG target has a yield stress larger (smaller) than the shock pressure imparted by the energetic processes of plasma generation and expansion, and thus, behaves like an elastic solid (a viscous fluid) to assist (impede) the formation of the plasma with high temperature and high density as an optical emission source for spectrochemical analysis. This work not only has significance in assessing a lower size limit for direct multielement analysis of RPG material using laser-induced breakdown spectroscopy (LIBS), but also shows that the mechanical characteristics of RPG material may be probed using LIBS.

Thermo-magnetic characterization of phase transitions in a Ni-Mn-In metamagnetic shape memory alloy

The partially overlapped ferroelastic/martensitic and para-ferromagnetic phase transitions of a Ni50.53Mn33.65In15.82 metamagnetic shape memory alloy have been studied from calorimetric, magnetic and acoustic emission measurement. We have taken advantage of the existence of thermal hysteresis of the first order ferroelastic/martensitic phase transition (~2.5 K) to discriminate the latent heat contribution ΔHt=7.2115 kJkg-1 and the specific heat contribution ΔHc=2161 Jkg-1to the total excess enthalpy of the phase transition. The specific heat was found to follow a step-like behavior at this phase transition. The intermittent dynamics of the ferroelastic/martensitic transition has been characterized as a series of avalaches detected both from acoustic emission and calorimetric measurements. The energy distribution of these avalanche events was found to follow a power law with a characteristic energy exponent ε≅2 which is in agreement with the expected value for a system undergoing a symmetry change from cubic to monoclinic. Finally, the critical behavior of the para-ferromagnetic austenite phase transition that takes place at ~311 K has been studied from the behavior of the specific heat. A critical exponent α≅0.09 has been obtained, which has been shown to be in agreement with previous values reported for Ni-Mn-Ga alloys but different from the critical divergence reported for pure Ni.

Scattered Far-Field Sampling in Multi-Static Multi-Frequency Configuration.

This paper deals with an inverse scattering problem under a linearized scattering model for a multi-static/multi-frequency configuration. The focus is on the determination of a sampling strategy that allows the reduction of the number of measurement points and frequencies and at the same time keeping the same achievable performance in the reconstructions as for full data acquisition. For the sake of simplicity, a 2D scalar geometry is addressed, and the scattered far-field data are collected. The relevant scattering operator exhibits a singular value spectrum that abruptly decays (i.e., a step-like behavior) beyond a certain index, which identifies the so-called number of degrees of freedom (NDF) of the problem. Accordingly, the sampling strategy is derived by looking for a discrete finite set of data points for which the arising semi-discrete scattering operator approximation can reproduce the most significant part of the singular spectrum, i.e., the singular values preceding the abrupt decay. To this end, the observation variables are suitably transformed so that Fourier-based arguments can be used. The arising sampling grid returns several data that is close to the NDF. Unfortunately, the resulting data points (in the angle-frequency domain) leading to a complicated measurement configuration which requires collecting the data at different spatial positions for each different frequency. To simplify the measurement configuration, a suboptimal sampling strategy is then proposed which, by an iterative procedure, enforces the sampling points to belong to a rectangular grid in the angle-frequency domain. As a result of this procedure, the overall data points (i.e., the couples angle-frequency) actually increase but the number of different angles and frequencies reduce and lead to a measurement configuration that is more practical to implement. A few numerical examples are included to check the proposed sampling scheme.

A microstructural model of tendon failure

Collagen fibrils are the most important structural component of tendons. Their crimped structure and parallel arrangement within the tendon lead to a distinctive non-linear stress–strain curve when a tendon is stretched. Microstructural models can be used to relate microscale collagen fibril mechanics to macroscale tendon mechanics, allowing us to identify the mechanisms behind each feature present in the stress–strain curve. Most models in the literature focus on the elastic behaviour of the tendon, and there are few which model beyond the elastic limit without introducing phenomenological parameters. We develop a model, built upon a collagen recruitment approach, that only contains microstructural parameters. We split the stress in the fibrils into elastic and plastic parts, and assume that the fibril yield stretch and rupture stretch are each described by a distribution function, rather than being single-valued. By changing the shapes of the distributions and their regions of overlap, we can produce macroscale tendon stress–strain curves that generate the full range of features observed experimentally, including those that could not be explained using existing models. These features include second linear regions occurring after the tendon has yielded, and step-like failure behaviour present after the stress has peaked. When we compare with an existing model, we find that our model reduces the average root mean squared error from 4.53MPa to 2.29MPa, and the resulting parameter values are closer to those found experimentally. Since our model contains only parameters that have a direct physical interpretation, it can be used to predict how processes such as ageing, disease, and injury affect the mechanical behaviour of tendons, provided we can quantify the effects of these processes on the microstructure.

Simulation on the mechanical performance and fracture behavior of unidirectional carbon fiber-reinforced composites

Unidirectional carbon fiber reinforced polyamide 6 (CF/PA6) laminates after tensile tests exhibited two different types of fracture modes, namely, splitting and step-like. In this study, the mechanical properties and fracture behavior of the unidirectional CF/PA6 laminates were simulated and analyzed by using finite element simulation of a tensile test. The simulations considered the actual deformation and damage mechanism (matrix plastic deformation, stochastic fiber fracture, and interfacial debonding between the fiber and the matrix) experimentally observed in previous research. Results of the numerical simulations were in good with the experimental stress–strain curves. Moreover, the above-mentioned two types of fracture mode were well simulated by changing the interfacial properties. The simulated results showed that the unidirectional laminates with weak interface properties exhibit the splitting fracture mode. Meanwhile, the unidirectional laminates with strong interface properties show the step-like fracture behavior.

Reliability of the prediction model for landslide displacement with step-like behavior

Based on the machine learning algorithms, prediction models for landslide displacement with step-like behavior in the reservoir area were established for landslides prevention and reduction; these models could predict a given test set very well. However, due to the length and the sequence of the training set in prediction models, the predictive ability of these prediction models could not be evaluated accurately if just validated with a given test set. To solve the problem, a hybrid reliability model was proposed. Complimentary ensemble empirical mode decomposition (CEEMD) algorithm was used to decompose the accumulated displacement into the trend displacement and the periodic displacement firstly. The Gauss function was used to predict the trend displacement, and the random forest (RF) and back propagation neural network (BPNN) algorithms were employed to predict the periodic displacement. Furthermore, a novel performance function for the reliability analysis of the displacement prediction model was derived to address failure probabilities in different cases. The Baijiabao landslide in the Three Gorges Reservoir Area was taken as an example for reliability analysis of the prediction model for landslide displacement with step-like behavior, and the predictive ability of the CEEMD-RF model and the CEEMD-BPNN model were compared. The results indicated that the CEEMD-RF model and CEEMD-BPNN model both can accurately predict the accumulated displacement of the given test set; the predictive value obtained with the CEEMD-RF model or the CEEMD-BPNN model showed uncertainties of the prediction model for landslide displacement and the predictive ability of the CEEMD-RF model was more reliable than the CEEMD-BPNN model under different cases. The failure probability proposed in the paper could evaluate the predictive ability of the model more accurately and comprehensively compared with the existing assessment indices.

Sensing of Surface and Bulk Refractive Index Using Magnetophotonic Crystal with Hybrid Magneto-Optical Response.

We propose an all-dielectric magneto-photonic crystal with a hybrid magneto-optical response that allows for the simultaneous measurements of the surface and bulk refractive index of the analyzed substance. The approach is based on two different spectral features of the magneto-optical response corresponding to the resonances in p- and s-polarizations of the incident light. Angular spectra of p-polarized light have a step-like behavior near the total internal reflection angle which position is sensitive to the bulk refractive index. S-polarized light excites the TE-polarized optical Tamm surface mode localized in a submicron region near the photonic crystal surface and is sensitive to the refractive index of the near-surface analyte. We propose to measure a hybrid magneto-optical intensity modulation of p-polarized light obtained by switching the magnetic field between the transverse and polar configurations. The transversal component of the external magnetic field is responsible for the magneto-optical resonance near total internal reflection conditions, and the polar component reveals the resonance of the Tamm surface mode. Therefore, both surface- and bulk-associated features are present in the magneto-optical spectra of the p-polarized light.

Magnetic Properties of Mn2RhSi Heusler Alloy: Phase Transition and Hysteresis Behavior at a Very Low Temperature

Using Kaneyoshi approximation in the framework of effective field theory, we have carried out theoretically the magnetic phase transition and hysteresis behavior at a very low temperature in Mn2RhSi Heusler Alloy (Mn2RhSi-HA). The alloy shows to a ferrimagnetic successive phase transition while its atoms exhibit a various successive phase transition with Tt = 0.630 and TC = 1.560. At a very low temperature, we attain that the alloy has a multistep hysteresis behavior having a butterfly-like hysteresis loop with a large coercivity field while the Si1 atom shows a type-II superconducting hysteresis behavior. Step-like hysteresis behavior at low temperature is due to quantum tunneling of the magnetization. So, we suggest Mn2RhSi-HA could be a potential candidate for magnetic storage device application. Moreover, we can conclude that the competition of antiferromagnetic and ferromagnetic exchange couplings leads to the variety of magnetic phase transition and the hysteresis behavior in Mn2RhSi-HA and its atoms. We can also conclude that these atoms and their exchange interactions to other atoms make a significant contribution to controlling the hysteresis behavior of Mn2RhSi-HA, since the Mn and Rh2 core atoms have the same coercivity as that of Mn2RhSi-HA. The obtained results are consistent with the reported experimental and theoretical results of Mn2-based Heusler alloys and other alloys.

Impedance and modulus studies of Pb(Fe0.5Nb0.5)O3–Pb(Co0.33Nb0.67)O3 solid solutions

The high quality polycrystalline (1-x)Pb(Fe0.5Nb0.5)O3(PFN)–(x)Pb(Co0.33Nb0.67)O3(PCN) (abbreviated as PFCN) ceramic solid solutions (x = 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized via single-step solid-state reaction technique. The formation of a single-phase, monoclinic structure with Cm symmetry and without any secondary phase was confirmed through the room temperature (RT) X-ray diffraction (XRD). The microstructure of sintered ceramics with well-grown grains having average grain size of 1–2 µm were observed through scanning electron microscopy (SEM). To understand the electrical response of the material impedance and modulus spectroscopy studies were carried out. A detailed temperature (301–481 K) and frequency (100 Hz to 6 MHz) dependent impedance and modulus of PFCN ceramic solid solutions were reported. The impedance spectroscopy reveals the increase of conductivity in the system by the addition of Pb(Co0.33Nb0.67)O3 due to increased number of oxygen vacancies (OVs)/defects created at the grain boundary interface during the synthesis. The Z′ vs. frequency shows the creation of space charges by the participating ionized OVs in the conduction process and Z′′ vs. frequency shows the presence of temperature-dependent relaxation processes in the PFCN solid solutions. The Nyquist plot (Z′′ vs Z′) shows the depressed semicircles suggesting the deviation from Debye type of relaxation behaviour and a decrease in the grain resistance for all compositions with rise in temperature, correlates the NTCR (negative temperature coefficient of resistance) nature. The M′ vs. frequency display the step-like behavior due to dipole contribution to the modulus present in the grain and grain boundary region. Fitted Kohlrausch-Williams-Watts (KWW) function to M′′ vs. frequency demonstrates the non-Debye type relaxation behavior in the PFCN solid solutions. The mismatch of fmax in the Z′′, M′′ vs. frequency indicates the short-range mobility of localized charge carriers.

Step-like dependence of memory function on pulse width in spintronics reservoir computing

Physical reservoir computing is a type of recurrent neural network that applies the dynamical response from physical systems to information processing. However, the relation between computation performance and physical parameters/phenomena still remains unclear. This study reports our progress regarding the role of current-dependent magnetic damping in the computational performance of reservoir computing. The current-dependent relaxation dynamics of a magnetic vortex core results in an asymmetric memory function with respect to binary inputs. A fast relaxation caused by a large input leads to a fast fading of the input memory, whereas a slow relaxation by a small input enables the reservoir to keep the input memory for a relatively long time. As a result, a step-like dependence is found for the short-term memory and parity-check capacities on the pulse width of input data, where the capacities remain at 1.5 for a certain range of the pulse width, and drop to 1.0 for a long pulse-width limit. Both analytical and numerical analyses clarify that the step-like behavior can be attributed to the current-dependent relaxation time of the vortex core to a limit-cycle state.

Simultaneous activation of multiple vestibular pathways upon electrical stimulation of semicircular canal afferents

Background and purposeVestibular implants seem to be a promising treatment for patients suffering from severe bilateral vestibulopathy. To optimize outcomes, we need to investigate how, and to which extent, the different vestibular pathways are activated. Here we characterized the simultaneous responses to electrical stimuli of three different vestibular pathways.MethodsThree vestibular implant recipients were included. First, activation thresholds and amplitude growth functions of electrically evoked vestibulo-ocular reflexes (eVOR), cervical myogenic potentials (ecVEMPs) and vestibular percepts (vestibulo-thalamo-cortical, VTC) were recorded upon stimulation with single, biphasic current pulses (200 µs/phase) delivered through five different vestibular electrodes. Latencies of eVOR and ecVEMPs were also characterized. Then we compared the amplitude growth functions of the three pathways using different stimulation profiles (1-pulse, 200 µs/phase; 1-pulse, 50 µs/phase; 4-pulses, 50 µs/phase, 1600 pulses-per-second) in one patient (two electrodes).ResultsThe median latencies of the eVOR and ecVEMPs were 8 ms (8–9 ms) and 10.2 ms (9.6–11.8 ms), respectively. While the amplitude of eVOR and ecVEMP responses increased with increasing stimulation current, the VTC pathway showed a different, step-like behavior. In this study, the 200 µs/phase paradigm appeared to give the best balance to enhance responses at lower stimulation currents.ConclusionsThis study is a first attempt to evaluate the simultaneous activation of different vestibular pathways. However, this issue deserves further and more detailed investigation to determine the actual possibility of selective stimulation of a given pathway, as well as the functional impact of the contribution of each pathway to the overall rehabilitation process.

Spin structure at zero magnetic field and field-induced spin reorientation transitions in a layered organic canted antiferromagnet bordering a superconducting phase

We attempted to assign the spin structure of a layered organic antiferromagnet, $\ensuremath{\kappa}$-(d8-BEDT-${\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\mathrm{Br}$, which is a key material located closest to the Mott boundary at ambient pressure among this family of compounds, by investigating its macroscopic magnetization thoroughly, motivated by a recent successful assignment of the spin structure of an isostructural material, $\ensuremath{\kappa}$-(BEDT-${\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\mathrm{Cl}$ [BEDT-TTF and d8-BEDT-TTF are bis(ethylenedithio)tetrathiafulvalene and its deuterated molecule, respectively]. We measured the isothermal magnetization after careful choice of the measurement temperatures and cooling speed at around 80 K, so that the magnetism of the antiferromagnetic phase can be effectively extracted. Consequently, we observed hysteresis loops signifying ferromagnetism and steplike behavior when the magnetic field applied parallel to the crystallographic $b$ and $a$ axes was swept, respectively. The possible spin structure consistent with these results was discussed in terms of probable interactions between the spins, such as exchange interactions and the Dzyaloshinskii-Moriya interaction. Eventually, we asserted that $\ensuremath{\kappa}$-(d8-BEDT-${\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\mathrm{Br}$ has a spin structure with the easy axis being the $c$ axis and the net canted moment parallel to the $b$ axis, which is surprisingly different from that of $\ensuremath{\kappa}$-(BEDT-${\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\mathrm{Cl}$. We suggested that this difference originates from the difference of the sign of the interlayer interaction between the two materials. We also elucidated the overall picture of the magnetization processes of this material under the magnetic fields parallel to the three principle axes, which are also in contrast to those of $\ensuremath{\kappa}$-(BEDT-${\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\mathrm{Cl}$. In particular, the spin-reverse transition at which half of the spins rotate by ${180}^{\ensuremath{\circ}}$ was not induced by the $b$-axis magnetic field, as in the case of $\ensuremath{\kappa}$-(BEDT-${\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\mathrm{Cl}$, but by the $a$-axis magnetic field. Finally, numerical simulations and magnetic symmetry analysis enabled us to confirm the validity of the spin structures proposed for the two antiferromagnets under zero and high magnetic fields.

Improved lunar edge response function for on-orbit modulation transfer function calibration using albedo flattening

The resolution of an imaging system can be quantified using the modulation transfer function (MTF) derived from an image with an edge feature. For Earth-viewing satellites, imaging an appropriate terrestrial edge feature is difficult when optical blur from the atmosphere contaminates the MTF. With a sharp edge and no atmosphere, our Moon has provided researchers with an alternative by deriving the line spread function from the lunar edge. The Moon’s surface, however, has features, e.g., craters and seas, that depart from clean step-like behavior, making curve fitting to the data difficult and diminishing the effectiveness of the method. We demonstrate an improvement in which a reflectance (albedo) map of the Moon, created from a mosaic of the U.S. Department of Defense/NASA Clementine images, is used to flatten the surface features before the edge spread function is measured. The objective is to improve the reliability of MTF measurements for on-orbit calibration of the National Oceanic and Atmospheric Administration/NASA Geostationary Operational Environmental Satellite (GOES) weather satellites and similar missions. The technique is applied to the reflective bands of the Advanced Baseline Imager on GOES-16 and GOES-17 weather monitoring satellites.

Dynamics of structural relaxation in bioactive 45S5 glass

Kinetics of physical aging in archetypic 45S5 bioactive silicate glass composition with different types of phase separation are studied in situ below the glass transition temperature (Tg). The qualitative nature of aging is found to be almost independent of the structural differences on the micrometer scale. A well-expressed step-like behavior in the enthalpy recovery kinetics is observed for aging temperatures Ta ∼ 0.90Tg and Ta ∼ 0.85Tg, which, however, disappears when the aging occurs at Ta ∼ 0.95Tg. The overall kinetics are described by a stretched-exponential function with stretching exponent close to 3/7 at Ta ∼ 0.95Tg, and 1/3 when the aging temperature drops to ∼0.90Tg and below. The values correlate well with the predictions of Phillips’ diffusion-to-traps and percolating fractals models. Appearance of step-like behavior at larger departure from Tg is attributed to the hierarchical scheme of approaching equilibrium based on an alignment-shrinkage mechanism of physical aging proposed earlier for chalcogenide glasses.

Self-assembled monolayer formation of pentamers-like molecules onto FCC(111) surfaces: the case of curcuminoids onto Au(111) surface

The adsorption of rigid straight electrically polarized pentamers over a FCC(111) surface is studied. The model was inspired by the deposition of 2-thiophene molecules over the Au(111) surface, which was previously characterized by experimental techniques and simulated under the frame of the density functional theory. We now obtain and report the charge distribution of the molecule which allows to propose a deposition model followed by Monte Carlo simulations over an ad-hoc lattice gas model. We show that for a certain value of the chemical potential there exists an isotropic-nematic phase transition which can explain the formation of a self-assembled monolayer like the one observed in the transmission electron microscopy images. An order parameter is defined to characterize the transition which presents a step-like behavior at a critical chemical potential value. The possible nature of the nematic transition in conjunction with an ergodicity breakdown is discussed as future work by means of statistical physics techniques.