Principal Values Research Articles

Thermal Behavior (–180 ≤ T ≤ 1000°C) of Magnesium Orthosilicate Hydroxylclinohumite Mg5(SiO4)2(OH,F)2

Hydroxylclinohumite Mg5(SiO4)2(OH,F)2 is a common monoclinic orthosilicate of the humite group, which, on the one hand, is a prototype of promising materials, and, on the other hand, is an important source of information about both the transport and the presence of water in the Earth’s mantle, and therefore studying its thermal behavior is of particular interest. In this paper, the mineral is studied by powder X-ray diffraction for the first time in a wide temperature range (–180 ≤ T ≤ 1000°C). The temperature limits for the existence of the phase are established, the principal values of the thermal expansion tensor are calculated, and a structural interpretation of thermal expansion is given.

Understanding biosecurity behaviors of Australian beef cattle farmers using the ten basic human values framework.

On-farm biosecurity is an essential component of successful disease management in the beef cattle industry on an individual, regional, and national level. Participation in mandatory or voluntary assurance schemes, knowledge and trusted relationships have all been demonstrated to contribute to the development of behaviors that promote biosecurity. However, compliance with rules, socio-psychological relationships and knowledge-seeking behavior are all contingent upon the motivations and beliefs of the individual. It is widely accepted that the motivations and beliefs of all cultures can be defined by ten basic values (Self-direction, Stimulation, Hedonism, Achievement, Power, Security, Conformity, Tradition, Benevolence and Universalism). In this study, we use the ten basic values to characterize the on-farm biosecurity behaviors of Australian beef farmers to facilitate the identification of interventions that are most likely to align with producer motivations and therefore, more likely to result in wider adoption of effective on-farm biosecurity. Semi-structured interviews were conducted with 11 Australian beef farmers to discuss the reasons behind decisions to alter or implement biosecurity practices in response to endemic diseases. Thematic analysis was used to identify the motivations, opportunities, and capability of biosecurity behaviors. The ten basic human values were used to characterize these behaviors and inform enablers and barriers to biosecurity adoption. Benevolence and Self-direction, relating to self-transcendence and an openness to change, were the principal values associated with good biosecurity behaviors. This suggests that farmers will be receptive to education strategies that communicate the actual risk of disease in their area, the impact of disease on animal welfare, and the ability for on-farm biosecurity to mitigate these impacts. Farmers also expressed values of Security which entrenched behaviors as common practice; however, in some cases the Security of trusted relationships was identified as a potential barrier to behavior change. Overall, values associated with biosecurity behaviors were found to align with values that are most important for social cohesion, suggesting that collaborative disease efforts between industry stakeholders and farmers are likely to succeed if designed with these values in mind.

Universal Method for Determining the Principal Optical Indicatrix Axes in Triclinic Crystals

Determining the orientations of principal optical indicatrix axes is a key prerequisite for the applications of optical crystals, which is still an intriguing challenge for triclinic optical crystals due to the lowest symmetry. The prism method is one of the important ways to determine these directions, but no actual examples are available owing to the complexity and scarcity of the triclinic crystals so far. To solve this remaining problem among seven crystal systems, we proposed a universal method, the so-called “multiple prisms method,” to determine the orientations of principal optical indicatrix axes X, Y, and Z as well as the principal refractive index values nx, ny, and nz in triclinic crystals based on four prisms and demonstrated this method by employing triclinic Nd3+-doped La2CaB8O16 crystals, which is of great significance to the studies and applications of triclinic optical crystals in the future.

Symmetry of the Hyperfine and Quadrupole Interactions of Boron Vacancies in a Hexagonal Boron Nitride

The concept of optically addressable spin states of deep level defects in wide band gap materials is successfully applied for the development of quantum technologies. Recently discovered negatively charged boron vacancy defects (VB) in hexagonal boron nitride (hBN) potentially allow a transfer of this concept onto atomic thin layers due to the van der Waals nature of the defect host. Here, we experimentally explore all terms of the VB spin Hamiltonian reflecting interactions with the three nearest nitrogen atoms by means of conventional electron spin resonance and high frequency (94 GHz) electron-nuclear double resonance. We establish symmetry, anisotropy, and principal values of the corresponding hyperfine interaction (HFI) and nuclear quadrupole interaction (NQI). The HFI can be expressed in the axially symmetric form as Aperp = 45.5 MHz and Apar = 87 MHz, while the NQI is characterized by quadrupole coupling constant Cq = 1.96 MHz with slight rhombisity parameter n = (Pxx - Pyy)/Pzz = -0.070. Utilizing a conventional approach based on a linear combination of atomic orbitals and HFI values measured here, we reveal that almost all spin density (84 %) of the VB electron spin is localized on the three nearest nitrogen atoms. Our findings serve as valuable spectroscopic data and direct experimental demonstration of the VB spin localization in a single two dimensional BN layer.

Effect of surface cleaning on seam quality of laser beam welded mixed joints

In this study, different surface cleaning methods were used to remove greases and oils from the surface of the E235 steel tube component of the diamond segmented drill bit before laser beam welding. The mechanical, chemical and electromechanical cleaning methods were selected because they are suitable for removing greases and oils adhering to the surface during tube production. The cleaned samples were successfully welded using the same heat inputs by laser welding. The effect of mechanical processes with sandblasting and dry-ice blasting, chemical processes with isopropyl alcohol, acetone and alkaline acidic liquid, electromechanical process with a laser beam on micro-computer tomography, break-out value and micro-hardness measurement examined. The cleanliness of the surfaces and strength of the laser-welded joint was inferred from the break-out value (BOV), as this is the principal qualification value in mass production. The results were compared to the untreated sample. According to the results obtained in this study, any defects in the seams were analyzed, and no cracks founded by computer tomography. According to a shade of grey diagram, all the pretreated samples had a higher absorption than the untreated sample. While the chemical methods had a significant effect (59–66 %), the mechanical and electromechanical methods had a positive effect (22–48 %) compared to the untreated sample. In addition, the break-out values showed that the mechanical methods had a significantly higher effect (19 %) than the other surface cleaning methods. This test showed different results from the micro-CT scan. The microhardness test showed no difference between the hardnesses of the cleaned and uncleaned samples and no difference in seam thicknesses. The optimal oil removal process discusses in the conclusion part.

Sustainable Fashion on Social Media

The sustainable fashion tribe is interested in ethical and ecological fashion consumption. To inform and reach various people, they use social media networks. However, as fashion consumption is often being used as a representation of wealth and status, the question arises, whether the underlying motives of the tribe to communicate on social media are altruistic or, on the contrary, promote conspicuous consumption. This qualitative study explores the underlying motives of the tribe communicating about sustainable fashion consumption on social media. The analysis of the nine interviews show, that there are four main motives: altruistic, social, egoistic and prestige-related motives. Even though the altruistic motives can be reconciled with the tribes’ principal values, the results also show signs of conspicuous consumption in terms of prestige-related motives. When posting on social media the tribe wants to inform about and influence its followers to a more sustainable fashion consumption, but also wants to gain reputation and recognition for it. Still, it is concluded that conspicuous consumption of sustainable fashion on social media can promote sustainable consumption overall and having a positive effect on the environment.

Patient-specific finite element simulation of peripheral artery percutaneous transluminal angioplasty to evaluate the procedure outcome without stent implantation.

The purpose of this work is to present a patient-specific (PS) modeling approach for simulating percutaneous transluminal angioplasty (PTA) endovascular treatment and assessing the balloon sizing influence on short-term outcomes in peripheral arteries, i.e. without stent implantation. Two 3D PS stenosed femoral artery models, one with a dominant calcified atherosclerosis while the other with a lipidic plaque, were generated from pre-operative computed tomography angiography images. Elastoplastic constitutive laws were implemented within the plaque and artery models. Implicit finite element method (FEM) was used to simulate the balloon inflation and deflation for different sizings. Besides vessel strains, results were mainly evaluated in terms of the elastic recoil ratio (ERR) and lumen gain ratio (LGR) attained immediately after PTA. Higher LGR values were shown within the stenosed region of the lipidic patient. Simulated results also showed a direct and quantified correlation between balloon sizing and LGR and ERR for both patients after PTA, with a more significant influence on the lumen gain. The max principal strain values in the outer arterial wall increased at higher balloon sizes during inflation as well, with higher rates of increase when the plaque was calcified. Results show that our model could serve in finding a compromise for each stenosis type: maximizing the achieved lumen gain after PTA, but at the same time without damaging the arterial tissue. The proposed methodology can serve as a step toward a clinical decision support system to improve angioplasty balloon sizing selection prior to the surgery.

Application of the in-situ stress testing technology for the design of operating pressure of underground gas storage reservoir

The appropriate design of the operating pressure of underground gas storages (UGSs) is of great significance to their safe and profitable operation. In situ stress is basic data for determining the upper limit pressure of UGSs, analyzing fault stability in reservoir areas, and evaluating trap tightness. Generally, the design of the upper limit gas injection pressure of UGSs is a comprehensive geomechanical problem. After research and comparison of measurement methods, it is believed that the measurement of in situ stress induced by hydraulic fracturing can accurately obtain the in situ stress value near the wellbore, and having knowledge about the reservoir stress path will considerably decrease the risk of reservoir and cap rock instability during gas injection and production. Taking Well C1, an oil reservoir-type UGS in Block M, eastern China as an example, this paper introduces the use of hydraulic fracturing (HF) in situ stress testing technology to obtain the minimum principal stress values of the caprock, reservoir and floor intervals of Well C1. The measured minimum principal stress of the caprock is 32.8–36.8 MPa. Because it is an old well, the minimum principal stress of the reservoir is 33.7–34.2 MPa after correction of the in situ stress measurement according to the theory of elasticity. Based on the comprehensive analysis of the measured in situ stress data, it is believed that the safe upper limit of the reservoir-type gas storage in Block M is 27.2 MPa.

Research on stress evolution law and failure characteristics of top coal in fully mechanized caving of extra-thick coal seams

In this study, based on the engineering background of the No. 8222 working face of the Tashan coal mine in Shanxi Province, China, true triaxial experiments were carried out on Geotechnical Consulting and Testing Systems rock mechanics testing machine using cubic coal samples, and the numerical simulation was conducted through the FLAC3D software. Moreover, the stress evolution law of different layers of extra-thick coal seams and the failure mechanism of top coal in the fully mechanized caving were investigated, and the failure structure model of top coal was established. The results show that there are differences in the principal stress values at different layers of the top coal.

Stress distribution of endodontically treated mandibular molars with varying amounts of tooth structure restored with direct composite resin with or without cuspal coverage: A 3D finite element analysis.

Decision-making regarding whether cuspal coverage is required or not for the restoration of root canal-treated posterior teeth is still a matter of challenge for the dentist. Four models of endodontically treated mandibular molars with mesio-occlusal (MO) cavity were designed and simulated with direct composite resin restorations. Group 1A - cavity width <½ the intercuspal distance restored without cuspal coverage, Group 1B - same as Group 1A but with cuspal coverage, Group 2A - MO cavity width >½ but <2/3rd the intercuspal distance restored without cuspal coverage, and Group 2B - same as Group 2A but with cuspal coverage. The models received occlusal load to simulate a mastication load. Static finite element analysis (FEA) was adopted for predicting the stress distribution generated in the restored tooth by the loading condition. FEA of the models have shown that the variations in stress values were significant in bulk-fill material compared to enamel and other structures. Comparing the maximum and minimum principal stress values in the overall region demonstrated that 2A was safer, whereas 2B was found to be the worst case. The results indicate that restoration of endodontically treated mandibular molar with loss of one marginal ridge with composite resin without cuspal coverage revealed minimal internal stress values and showed the best performance overall.

Comparative photoelastic stress analysis between all-on-four implant-supported cobalt-chromium framework and carbon fiber reinforced framework with varying cantilever lengths - An in vitro study

CONTEXT: In implant prosthodontics, metal frameworks are used to rigidly spilt the implants together to provide rigidity and stiffness to the prosthesis. However, due to the limitations associated with the metal framework fabrication, the recent advances have made it possible to fabricate metal-free implant-supported prostheses using fiber-reinforced composite frameworks.AIM: This study aimed to evaluate and compare photoelastic stresses between all-on-four implant-supported cobalt-chromium (Co-Cr) framework and the carbon fiber-reinforced composite (CFRC) framework at varying cantilever lengths.MATERIALS AND METHODS: Two photoelastic models of an edentulous mandible were fabricated according to the all-on-four concept. Following this, frameworks with a bilateral cantilever extension of 20 mm, one with CFRC and the other with Co-Cr, were fabricated and were subjected to a progressive load of 120–180 N with an interval of 20 N. The principal stresses (σ) were calculated using the mean maximum fringe order.STATISTICAL ANALYSIS: The quantitative analysis was performed using the Kruskal–Wallis test and Mann–Whitney U-test, P ≤ 0.05.RESULTS: The CFRC framework showed mean principal stress values significantly lower than the Co-Cr framework under all loading conditions; however, deformation of the framework was observed at the cantilever lengths of 15 mm and 20 mm.CONCLUSION: The study and its findings have indicated that the CFRC framework appears suitable for the fabrication of a framework for an “All-on-four” prosthesis. Within the confines of this study, the use of 10 mm as an arbitrary cantilever length recommendation for the CFRC framework and 15 mm for the Co-Cr framework seems reasonable.

Computer analysis of the differential equation of the model of the synchronous electric motor that does not include electric currents

Phase portraits of the well-known equation of the no-current model of the synchronous electric motor are obtained with use of computer, and some properties of its solutions are noted, which are imperceptible at the phase portraits, obtained analytically. With use of computer, a graph is built for the curve, representing the critical value versus the principal stationary value of the angular variable. Linear and sinusoidal approximations are proposed for this curve, maximum absolute and relative errors of these approximations are calculated.

Photocycle of a cyanobacteriochrome: a charge defect on ring C impairs conjugation in chromophore.

A large number of novel phytochromes named cyanobacteriochromes (CBCRs) have been recently identified. CBCRs appear to be attractive for further in-depth studies as paradigms for phytochromes because of their related photochemistry, but simpler domain architecture. Elucidating the mechanisms of spectral tuning for the bilin chromophore down to the molecular/atomic level is a prerequisite to design fine-tuned photoswitches for optogenetics. Several explanations for the blue shift during photoproduct formation associated with the red/green CBCRs represented by Slr1393g3 have been developed. There are, however, only sparse mechanistic data concerning the factors controlling stepwise absorbance changes along the reaction pathways from the dark state to the photoproduct and vice versa in this subfamily. Conventional cryotrapping of photocycle intermediates of phytochromes has proven experimentally intractable for solid-state NMR spectroscopy within the probe. Here, we have developed a simple method to circumvent this hindrance by incorporating proteins into trehalose glasses which allows four photocycle intermediates of Slr1393g3 to be isolated for NMR use. In addition to identifying the chemical shifts and chemical shift anisotropy principal values of selective chromophore carbons in various photocycle states, we generated QM/MM models of the dark state and photoproduct as well as of the primary intermediate of the backward-reaction. We find the motion of all three methine bridges in both reaction directions but in different orders. These molecular events channel light excitation to drive distinguishable transformation processes. Our work also suggests that polaronic self-trapping of a conjugation defect by displacement of the counterion during the photocycle would play a role in tuning the spectral properties of both the dark state and photoproduct.

Effective thermal conductivity of composites with anisotropic particles of various shapes embedded in an isotropic matrix

The paper demonstrates a method to calculate effective thermal conductivity in a two-phase medium with an isotropic host phase and embedded anisotropic particles. The presented scheme enables easy incorporation of various regular shapes of filler particles if the principal values of their Eshelby tensor are supplied. Basic shapes, such as spheroids, may approximate a wide range of fillers used to enhance thermal conduction, such as polymers filled with highly conductive metal and ceramic powders, graphite and graphene flakes, and nanotubes. Different spatial orientations and sizes of particles may be supplied to the model in the form of probability distributions. The method is well suited to numerical implementation, and the resulting computations are less demanding than popular mesh-based methods, i.e., Finite Volume and Finite Element Methods. It does not include interfacial thermal resistance between particles and matrix, but the addition of this component is planned in future papers.

Substantiation and development of innovative container technology for rock mass lifting from deep open pits

Purpose. The research purpose is to substantiate the rational parameters of innovative container technology for transporting mine rocks in open pits with account of technological advantages. Methods. The winding machine normal operation was determined by calculation performed. The container metal structure was designed in the environment of the Compass-3D software complex. The structural elements were tested for normal operation using computer modeling methods in the APM WinMachine 9.7 program, which gives the possibility to obtain the strength calculation values. Findings. The results of modeling the stresses on the wall of the container and the frame, as well as the yield strength are presented. The test calculation confirms the technical feasibility for operating the dragline-based mine winding machines. The influence of the container capacity on the performance of the winding machine has been determined and the dependence of the economic efficiency of the container technology introduction at the open pit depth has been revealed. Originality. For the first time, on the basis of computer modeling, the parameters of stress distribution on the container wall have been substantiated when performing a strength calculation. It has been determined that the maximum stress in the container wall is 117.52 N/mm2; the principal stress value is 83.85 N/mm2. The safety factor for yield strength is 1.8. The maximum load acting on the structure is 957.5 kgf, which does not exceed the calculated value. Practical implications. The practical importance is to improve mining efficiency, reduce the cost of transporting rocks and ensure automatic container unloading. The use of replaceable containers in open pits can significantly change the formation principles of shovels and transport complexes, increase their performance and the efficiency of shovels in the main processes.

The Effects of Fixation Methods on the Composition and Activity of Sea Buckthorn (Hippophae rhamnoides L.) Leaf Tea

Fixation is the key step to improve the quality of sea buckthorn leaf tea. Composition and activity are important indexes to evaluate the quality of sea buckthorn leaf tea. Comparing the effects of fixation methods on components and activities provides a theoretical basis for the contemporary, controllable, and continuous production of sea buckthorn leaf tea. The effects of six different fixed methods, pan-firing fixed (PF), steaming fixed (SF), boiling water fixed (BF), hot air fixed (HF), microwave fixed (MWF), and infrared fixed (IRF) for sea buckthorn leaf tea in terms of α-glucosidase inhibitory activity, lipase inhibitory ability, and the antioxidant capacity were studied. The total flavonoids (TF) content, total soluble phenolics (TP) content, water-soluble carbohydrate (WSC) content, the inhibitory activity of α-glucosidase, lipase inhibitory ability, and the antioxidant capacity of fixed sea buckthorn leaf tea were significantly higher ( p ≤ 0.05 ) compared with sea buckthorn leaf. IRF and MWF samples had higher ( p ≤ 0.05 ) contents of TF (92.48 mg RE/g and 79.20 mg RE/g), TP (115.37 mg GA/g and 135.18 mg GA/g) and WSC (4.24% and 4.39%). The DPPH radical scavenging activity of the SF sample was the strongest one, followed by the MWF sample and IRF sample ( p ≤ 0.05 ). The hydroxyl radical scavenging ability and reducing power of IRF were the strongest one, followed by the MWF sample ( p ≤ 0.05 ). The IRF sample had the strongest α-glucosidase inhibitory activity ( p ≤ 0.05 ), and the MWF sample had the strongest lipase inhibitory ability while samples contained the same amount of total polyphenols ( p ≤ 0.05 ). Principal component analysis results showed that the IRF sample, MWF sample, and SF sample had higher comprehensive principal component values. MWF takes less time than IRF, which operated at 2,450 MHz (full power of 700 W) for 2 min. Therefore, MWF was the most suitable fixation method for sea buckthorn leaf tea. Practical Applications. Leaf tea is the main product of sea buckthorn leaf. However, at present, the quality of sea buckthorn leaf tea in the market is uneven, the processing methods are diverse, and there is no certain quality standard. This paper provides some data support and theoretical support for the production, processing, and purchase of sea buckthorn leaf tea.

ON THE CONVEXITY OF POTENTIAL OF NONLINEAR ELASTIC MEDIA MODEL WITH TENSOR DAMAGE PARAMETER

For solving problems of the theory of elasticity using nonlinear models, the question of the convexity of the potential used and the proof of the uniqueness of the solution are of decisive importance. The present work is devoted to the determination of conditions for the local strict convexity of the potential for the nonlinear elasticity model, which ensure the uniqueness of the solution to the problem in a sufficiently small neighborhood of the desired solution. The considered model is a generalization of a scalar nonlinear rheological model of brittle solid deformation for the case of the tensor damage parameter, the principal values of which describe the reduction in the cross-sectional area of the material in three orthogonal directions. An additional term of the second order in deformation in the elastic potential makes it possible to describe the dependence of the elastic moduli on the type of the stress-strain state, the dilatancy of the material under shear deformation, as well as the nonlinear deformation response even at low loads. The introduced damage tensor of the second rank makes it possible to describe the damage-induced anisotropy of the elastic properties of the material. Conditions of local strict convexity in the principal axes of the strain tensor are obtained in this work for the general case of misaligned strain and damage tensors. To illustrate the obtained convexity conditions, two special cases of the damage tensor type are considered: a transversely isotropic fractured medium with coaxial strain and damage tensors, and a transversely isotropic medium with obliquely oriented fracturing. For both cases, the dependence of the limiting values of damage on the parameter of the degree of anisotropy is shown. It is shown that in the case of weak damage anisotropy, the potential convexity conditions for the scalar damage parameter give a minorant estimate of the maximum allowable damage for various types of stress-strain state. For obliquely oriented fracturing, the dependences of the maximum permissible damage on the degree of anisotropy, the angle of inclination and the type of stress-strain state are plotted.

Biomechanical Behavior of Narrow Dental Implants Made with Aluminum- and Vanadium-Free Alloys: A Finite Element Analysis.

Titanium (Ti) alloys used for narrow dental implants usually contain aluminum (Al) and vanadium (V) for improved resistance. However, those elements are linked to possible cytotoxic effects. Thus, this study evaluated the biomechanical behavior of narrow dental implants made with Al- and V-free Ti alloys by the finite element method. A virtual model of a partially edentulous maxilla received single implants (diameter: 2.7 and 2.9 mm; length: 10 mm) at the upper lateral incisor area, with respective abutments and porcelain-fused-to-metal crowns. Simulations were performed for each implant diameter and the following eight alloys (and elastic moduli): (1) Ti-6Al-4V (control; 110 GPa), (2) Ti-35Nb-5Sn-6Mo-3Zr (85 GPa), (3) Ti-13Nb-13Zr (77 GPa), (4) Ti-15Zr (113 GPa), (5) Ti-8Fe-5Ta (120 GPa), (6) Ti-26.88Fe-4Ta (175 GPa), (7) TNTZ-2Fe-0.4O (107 GPa), and (8) TNTZ-2Fe-0.7O (109 GPa). The implants received a labially directed total static load of 100 N at a 45° angle relative to their long axis. Parameters for analysis included the maximum and minimum principal stresses for bone, and von Mises equivalent stress for implants and abutments. Ti-26.88Fe-4Ta reaches the lowest maximum (57 MPa) and minimum (125 MPa) principal stress values, whereas Ti-35Nb-5Sn-6Mo-3Zr (183 MPa) and Ti-13Nb-13Zr (191 MPa) models result in the highest principal stresses (the 2.7 mm model surpasses the threshold for bone overload). Implant diameters affect von Mises stresses more than the constituent alloys. It can be concluded that the narrow implants made of the Ti-26.88Fe-4Ta alloy have the most favorable biomechanical behavior, mostly by mitigating stress on peri-implant bone.

Finite Element Analysis-Based Evaluation of the Patient-Specific Spinal Rods for a Reduced Risk of Adjacent Segment Disease

Adjacent Segment Disease (ASD) is a postoperative drawback of spinal fusion surgery which yields an increase in the range of motion in the adjacent spinal level. Therefore, the main aim of this study is to investigate the optimum mechanical properties of the spinal rod allowing a reduced rigidity in the spinal fixation level for decreasing the displacement of the adjacent segment. In this study, the spinal fixation system was modelled and attached to L3-L4 level. The elasticity modulus of the rods and the follower load were parametrically defined in order to investigate their optimum values under physiological loading conditions of extension. The maximum displacement value determined for the upper adjacent intervertebral disc was defined as the output parameter. Thereafter, the biomechanical response of the spinal bone-implant complex was simulated using Finite Element Analysis (FEA). Using the parametric FEA results, a polynomial mathematical model was constructed and Response Surface Method (RSM) was used to plot the relationship between input and output parameters. According to the results of the study, the optimum elasticity modulus of the rods and the suggested follower load have been determined as 80.8 GPa and 303.84 N, respectively. The maximum principal strain values obtained in the pedicle screws were 746 µℇ, 1563 µℇ, 3037 µℇ and 2937 µℇ, respectively. However, since the results are strongly associated with anatomical and biomechanical differences, the proposed patient-specific approach may enhance the accuracy for a more successful spinal fusion surgery operation in terms of minimizing the risk of ASD.

Marshall Sahlins, where are you? From the intellectual to the existential

Marshall Sahlins, where are you? From the intellectual to the existential