Dataset of phase-resolved images of internal, corona, and surface partial discharges in electrical generators

This article presents the data collection process for the classification of partial discharges in electrical generators using PNG format images. The data were collected through field measurements on over 40 generators in various locations in Colombia, in addition to utilizing a partial discharge simulator provided by Omicron Energy. Throughout the collection process, special attention was given to the accuracy and coherence of the images, avoiding deformations and distortions that could impact the nature of partial discharges. Emphasis was placed on achieving high resolution in phase-resolved patterns (PRPD) to effectively correlate them with the adjacent physical phenomenon. The analysis focused on classifying the images according to the type of partial discharge, identifying them as internal, surface, or corona discharges. The obtained pulse patterns are represented in RGB color, which aids in assessing the repeatability of pulses across their distribution. These data hold potential for the development of pattern classification software for generator monitoring systems. They enable the training and validation of classification algorithms, simplifying the automated detection and analysis of partial discharges in electrical generators. Their applicability extends beyond the electrical industry and can be valuable in other fields requiring complex signal and pattern analysis. The article highlights the rigorous data collection process and precise analysis conducted to obtain a valuable set of PNG format images for partial discharge classification. These data have significant potential in advancing pattern classification software, driving progress in the monitoring and analysis of electrical generators.

Durvalumab plus tremelimumab for the treatment of advanced neuroendocrine neoplasms of gastroenteropancreatic and lung origin

Single immune checkpoint blockade in advanced neuroendocrine neoplasms (NENs) shows limited efficacy; dual checkpoint blockade may improve treatment activity. Dune (NCT03095274) is a non-randomized controlled multicohort phase II clinical trial evaluating durvalumab plus tremelimumab activity and safety in advanced NENs. This study included 123 patients presenting between 2017 and 2019 with typical/atypical lung carcinoids (Cohort 1), G1/2 gastrointestinal (Cohort 2), G1/2 pancreatic (Cohort 3) and G3 gastroenteropancreatic (GEP) (Cohort 4) NENs; who progressed to standard therapies. Patients received 1500 mg durvalumab and 75 mg tremelimumab for up to 13 and 4 cycles (every 4 weeks), respectively. The primary objective was the 9-month clinical benefit rate (CBR) for cohorts 1-3 and 9-month overall survival (OS) rate for Cohort 4. Secondary endpoints included objective response rate, duration of response, progression-free survival according to irRECIST, overall survival, and safety. Correlation of PD-L1 expression with efficacy was exploratory. The 9-month CBR was 25.9%/35.5%/25% for Cohorts 1, 2, and 3 respectively. The 9-month OS rate for Cohort 4 was 36.1%, surpassing the futility threshold. Benefit in Cohort 4 was observed regardless of differentiation and Ki67 levels. PD-L1 combined scores did not correlate with treatment activity. Safety profile was consistent with that of prior studies. In conclusion, durvalumab plus tremelimumab is safe in NENs and shows modest survival benefit in G3 GEP-NENs; with one-third of these patients experiencing a prolonged OS.

A reply to "Relevant factors in the eutrophication of the Uruguay River and the Río Negro"

A recent paper by Beretta-Blanco and Carrasco-Letelier (2021) claims that agricultural eutrophication is not one of the main causes for cyanobacterial blooms in rivers and artificial reservoirs. By combining rivers of markedly different hydrological characteristics e.g., presence/absence and number of dams, river discharge and geological setting, the study speculates about the role of nutrients for modulating phytoplankton chlorophyll-a. Here, we identified serious flaws, from erratic and inaccurate data manipulation. The study did not define how erroneous original dataset values were treated, how the variables below the detection/quantification limit were numerically introduced, lack of mandatory variables for river studies such as flow and rainfall, arbitrary removal of pH > 7.5 values (which were not outliers), and finally how extreme values of other environmental variables were included. In addition, we identified conceptual and procedural mistakes such as biased construction/evaluation of model prediction capability. The study trained the model using pooled data from a short restricted lotic section of the (large) Uruguay River and from both lotic and reservoir domains of the Negro River, but then tested predictability within the (small) Cuareim River. Besides these methodological considerations, the article shows misinterpretations of the statistical correlation of cause and effect neglecting basic limnological knowledge of the ecology of harmful algal blooms (HABs) and international research on land use effects on freshwater quality. The argument that pH is a predictor variable for HABs neglects overwhelming basic paradigms of carbon fluxes and change in pH because of primary productivity. As a result, the article introduces the notion that HABs formation are not related to agricultural land use and water residence time and generate a great risk for the management of surface waterbodies. This reply also emphasizes the need for good practices of open data management, especially for public databases in view of external reproducibility.

Sex Differences in Proximal Thoracic Aortic Disease Pathology: A Call to Action

Introduction/Objective

Sex disparity is reported across all forms of cardiovascular diseases. Only few studies have focused on sex differences in thoracic aortic disease pathology. We aim to identify and understand sex differences in this patient group to bridge the knowledge gap and improve clinicopathologic outcomes.

Methods/Case Report

This is a retrospective analysis of 83 proximal thoracic aortic aneurysm and dissection (TAAD) cases treated at a single quaternary care center in 2019. Chart review was done for demographics. Consensus criteria (Stone JR et al. Cardiovasc Pathol 2015; 24:267-78; Halushka MK et al. Cardiovasc Pathol 2016; 25:247-57) and a scoring system (Waters KM et al. Cardiovasc Pathol 2017; 30:6-11) were used for pathology reporting. Clinical correlation was also made. Pearson’s chi-square test was used for statistical analysis.

Results (if a Case Study enter NA)

83 patients (61 male and 22 female) were retrieved. Overall thoracic aortopathy was higher among males, accounting for 73.4% of individuals with TAAD. In a subgroup analysis, there was no sex difference in dissection, aortic root involvement, and bicuspid aortic valve (p>0.05). Genetic aortopathy was more prevalent in females than males (27.2% vs 9.8%, p=0.04) alongside early age at first aortic event (median age: 31y vs 52y). Histopathologically, females had frequent translamellar mucoid extracellular matrix accumulation (45.4% vs 22.9%, p=0.04), extensive (54.5% vs 27.8%, p=0.02) and severe (59% vs 34.4%, p=0.04) elastic fiber fragmentation, higher band like (9% vs 6.5%, p>0.05) plus extensive (13.6% vs 4.9%, p>0.05) smooth muscle nuclei loss, and extensive (13.6% vs 1.6%, p=0.01) plus dense (4.5% vs 1.6%, p>0.05) laminar medial collapse than males.

Conclusion

In our patient population, females have a lower prevalence of thoracic aortic disease treated with open repair. However, those who develop TAAD harbor a greater burden of wall pathology and probable worse outcomes. We recommend sex-based analysis of all research on thoracic aortic diseases.

Low frequency of cytomegalovirus (CMV) disease despite high prevalence of CMV viraemia in patients with advanced HIV infection: a clinical and immunological 48-week follow-up study

OBJECTIVES

The aim of the study was to investigate the dynamics of cytomegalovirus (CMV) replication and CMV-specific immune response recovery after antiretroviral treatment (ART) initiation in patients with advanced HIV infection.

METHODS

A prospective observational study of patients with HIV infection and CD4 counts of < 100 cells/µL was carried out (September 2015 to July 2018). HIV viral load (VL), CD4 count and CMV VL were determined by quantitative polymerase chain reaction (PCR) at baseline and at 4, 12, 24 and 48 weeks, and CMV-specific immune response was determined by QuantiFERON-CMV assay at baseline and 48 weeks. All patients were started on ART but only those with CMV end-organ disease (EOD) received anti-CMV treatment.

RESULTS

Fifty-three patients with a median age of 43.6 [interquartile range (IQR) 36.7-52.4] years were included in the study. At baseline, the median CD4 count was 30 cells/µL (IQR 20-60 cells/µL) and the median HIV VL was 462 000 HIV-1 RNA copies/mL (IQR 186 000-1 300 000 copies/mL). At baseline, 32% patients had detectable CMV viraemia but none had detectable CMV viraemia at 48 weeks. Only one of 53 (1.9%) patients developed EOD during follow-up. Seven (13.2%) patients were lost to follow-up and six (11.3%) died; none of the deaths was related to CMV. Similar percentages of patients had a CMV-specific immune response at baseline (71.7%) and at 48 weeks (70.0%). The magnitude of this response tended to increase over time [median 1.63 (IQR 0.15-5.77) IU/mL at baseline vs. median 2.5 (IQR 0.1-8.325) IU/mL at 48 weeks; P = 0.11]. We did not find any risk factors associated with 48-week mortality.

CONCLUSIONS

Although the prevalence of CMV viraemia in patients with advanced HIV infection remains high, achieving a good immunological recovery through ART is enough to suppress CMV viraemia, without an increased risk of CMV EOD. The prevalence of a CMV-specific immune response was high and endured over time.

Multidisciplinary care and units for uveitis in the internal medicine departments in Spain: Survey of the Systemic Autoimmune Diseases Group

OBJECTIVE

To identify the multidisciplinary uveitis units in which internal medicine departments participate in collaboration with ophthalmology departments in Spain.

MATERIAL AND METHODS

We conducted a multicentre, observational cross-sectional study that collected information using a structured survey sent by email to 1015 partners of the Systemic Autoimmune Diseases Workgroup of the Spanish Society of Internal Medicine (GEAS-SEMI) from the 1st to the 31st of March 2017.

RESULTS

We identified a total of 21 support units/consultations for the ophthalmology departments. Seventeen (81%) of the units were specific internal medicine-ophthalmology consultations, and 5 (24%) units had been created in the past 5 years. A median of 460 patients were assessed per unit by the end of the year.

CONCLUSIONS

This study shows, for the first time in Spain, the important and close collaboration between ophthalmologists and internists, especially in highly specialised national reference institutions.

Innovative methods in teaching public health ethics. The need to adapt to the new times: from challenge to opportunity

Background

Public Health Ethics (PHE) has been taught first as optional and later as a mandatory subject in the Master of Public Health in Barcelona for about 6 years. During these years, professors have adapted the methodology to make it more attractive and to maximize students' participation and time spent debating and practicing moral reasoning.

Objectives

To showcase 3 different teaching strategies or methods, presenting for each of them: resources required, outcomes so far in terms of satisfaction and exam performance, as well as the pros and cons from the teacher's perspective.

Results

Flipped-classroom strategy: theoretical content is delivered outside the classroom, and the practice into the classroom. Works well but needs incentives for compliance in reading. Versatile debating Methods: from parliamentary debate, to role-playing, online debate, etc. Depending on the Case-study, some work better than others; in the online they practice written deliberation skills, but it is important to set rules. MOOC: Massive Online Open Courses in PHE. Can be used as independent teaching material, it is a great tool to introduce PHE into other PH areas and non-teaching environments.

Conclusions

So far, these methods have proven to increase students' motivation and engagement in Public Health Ethics.

Key messages

Practising reflection and debating skills is an essential part of PHE. Modern teaching strategies, more interactive and online-based, can help maximising the time spent in these activities. Although challenging and time-consuming at first, these methods also increase students' interest in PHE.

Multidisciplinary care and units for uveitis in the internal medicine departments in Spain: Survey of the Systemic Autoimmune Diseases Group

OBJECTIVE

To identify the multidisciplinary uveitis units in which internal medicine departments participate in collaboration with ophthalmology departments in Spain.

MATERIAL AND METHODS

We conducted a multicentre, observational cross-sectional study that collected information using a structured survey sent by email to 1015 partners of the Systemic Autoimmune Diseases Workgroup of the Spanish Society of Internal Medicine (GEAS-SEMI) from the 1st to the 31st of March 2017.

RESULTS

We identified a total of 21 support units/consultations for the ophthalmology departments. Seventeen (81%) of the units were specific internal medicine-ophthalmology consultations, and 5 (24%) units had been created in the past 5 years. A median of 460 patients were assessed per unit by the end of the year.

CONCLUSIONS

This study shows, for the first time in Spain, the important and close collaboration between ophthalmologists and internists, especially in highly specialized national reference institutions.

Combining electrokinetic transport and bioremediation for enhanced removal of crude oil from contaminated marine sediments: Results of a long-term, mesocosm-scale experiment

Marine sediments represent an important sink of harmful petroleum hydrocarbons after an accidental oil spill. Electrobioremediation techniques, which combine electrokinetic transport and biodegradation processes, represent an emerging technological platform for a sustainable remediation of contaminated sediments. Here, we describe the results of a long-term mesocosm-scale electrobioremediation experiment for the treatment of marine sediments contaminated by crude oil. A dimensionally stable anode and a stainless-steel mesh cathode were employed to drive seawater electrolysis at a fixed current density of 11 A/m². This approach allowed establishing conditions conducive to contaminants biodegradation, as confirmed by the enrichment of Alcanivorax borkumensis cells harboring the alkB-gene and other aerobic hydrocarbonoclastic bacteria. Oil chemistry analyses indicated that aromatic hydrocarbons were primarily removed from the sediment via electroosmosis and low molecular weight alkanes (nC₆ to nC₁₀) via biodegradation.

Rats’ Choice in a Coordination Task

We designed a free-operant choice procedure that represents a technical improvement to assess the control of mutual reinforcement contingencies over the choice of coordinated behavior. We demonstrate the advantages of the new procedure with eight rats that were trained to continuously move a steel ball from end to end of a gutter. Subjects were assigned to pairs and had to choose between two response options: one in which reinforcement was contingent upon an individual response, and another in which reinforcement depended on the coordination of intra-pair behavior. We evaluated (a) the effect of reinforcement magnitude over the distribution of responses, and (b) the role of behavioral cues on the rats’ coordinated actions via dividing the experimental chamber in two compartments with a clear/opaque partition. The coordinated actions were more likely when the larger reinforcer was initially associated with the mutual reinforcement option. The visual interaction between subjects did not impact their coordinated actions. The possibility to control organisms’ preference for social or nonsocial alternatives opens potential lines of research. For instance, identifying how the coordination of activities combines with the future value of outcomes to produce stable cooperative equilibria.

Two-dimensional collective electron magnetotransport, oscillations, and chaos in a semiconductor superlattice

When quantized, traces of classically chaotic single-particle systems include eigenvalue statistics and scars in eigenfuntions. Since 2001, many theoretical and experimental works have argued that classically chaotic single-electron dynamics influences and controls collective electron transport. For transport in semiconductor superlattices under tilted magnetic and electric fields, these theories rely on a reduction to a one-dimensional self-consistent drift model. A two-dimensional theory based on self-consistent Boltzmann transport does not support that single-electron chaos influences collective transport. This theory agrees with existing experimental evidence of current self-oscillations, predicts spontaneous collective chaos via a period doubling scenario, and could be tested unambiguously by measuring the electric potential inside the superlattice under a tilted magnetic field.

Structural Metastability and Quantum Confinement in Zn1-xCoxO Nanoparticles

This paper investigates the electronic structure of wurtzite (W) and rock-salt (RS) Zn1-xCoxO nanoparticles (NPs) by means of optical measurements under pressure (up to 25 GPa), X-ray absorption, and transmission electron microscopy. W-NPs were chemically synthesized at ambient conditions and RS-NPs were obtained by pressure-induced transformation of W-NPs. In contrast to the abrupt phase transition in W-Zn1-xCoxO as thin film or single crystal, occurring sharply at about 9 GPa, spectroscopic signatures of tetrahedral Co(2+) are observed in NPs from ambient pressure to about 17 GPa. Above this pressure, several changes in the absorption spectrum reveal a gradual and irreversible W-to-RS phase transition: (i) the fundamental band-to-band edge shifts to higher photon energies; (ii) the charge-transfer absorption band virtually disappears (or overlaps the fundamental edge); and (iii) the intensity of the crystal-field absorption peaks of Co(2+) around 2 eV decreases by an order of magnitude and shifts to 2.5 eV. After incomplete phase transition pressure cycles, the absorption edge of nontransformed W-NPs at ambient pressure exhibits a blue shift of 0.22 eV. This extra shift is interpreted in terms of quantum confinement effects. The observed gradual phase transition and metastability are related to the NP size distribution: the larger the NP, the lower the W-to-RS transition pressure.

Pressure-induced amorphization of YVO₄:Eu³⁺ nanoboxes

A structural transformation from the zircon-type structure to an amorphous phase has been found in YVO4:Eu(3+) nanoboxes at high pressures above 12.7 GPa by means of x-ray diffraction measurements. However, the pair distribution function of the high-pressure phase shows that the local structure of the amorphous phase is similar to the scheelite-type YVO4. These results are confirmed both by Raman spectroscopy and Eu(3+) photoluminescence which detect the phase transition to a scheelite-type structure at 10.1 and 9.1 GPa, respectively. The irreversibility of the phase transition is observed with the three techniques after a maximum pressure in the upstroke of around 20 GPa. The existence of two (5)D0-->(7)F0 photoluminescence peaks confirms the existence of two local environments for Eu(3+), at least for the low-pressure phase. One environment is the expected for substituting Y(3+) and the other is likely a disordered environment possibly found at the surface of the nanoboxes.

Investigation of lattice dynamical and dielectric properties of MgO under high pressure by means of mid- and far-infrared spectroscopy

We investigate the lattice dynamical and dielectric properties of MgO single crystals and powders by measurements in the mid- and far-infrared frequency region under high pressures, ranging up to 21.7 GPa. The shift of the restrahlen region is used to determine the pressure dependence of the transverse and longitudinal optical modes. The analysis of the refractive index in the mid- and far-infrared region allowed us to obtain the pressure behavior of the static and electronic dielectric constants. The transverse effective charge slowly decreases under high pressure, reflecting the stability of MgO. As a consequence, the pressure dependence of the static and electronic dielectric constants is mainly determined by the pressure dependence of the polar phonon frequency and Penn gap, resulting in a pronounced decrease of the former and a moderate decrease of the latter.

Lethal Toxicity After 5-Fluorouracil Chemotherapy and Its Possible Relationship to Dihydropyrimidine Dehydrogenase Deficiency: A Case Report and Review

5-fluorouracil (5-FU) is a chemotherapeutic agent widely used in the treatment of solid malignancies, especially in colorectal cancer. A characteristic note seen with its use is the considerable interindividual variation in the incidence and severity of the toxicities seen among patients. We report the case of a 55-year old woman who presented with severe, lethal toxicity to standard doses of 5-fluorouracil (5-FU) and folinic acid. We discuss the known clinical determinants of toxicity. We also discuss the possible molecular factors implicated in the variable toxicity seen to 5-FU, especially in regards to dihiyropyrimidine dehydrogenase, a pivotal enzyme in the metabolism of 5-FU.

XRD and XAS structural study of CuAlO2 under high pressure

We present the results of x-ray diffraction and x-ray absorption spectroscopy experiments in CuAlO(2) under high pressure. We discuss the polarization dependence of the x-ray absorption near-edge structure at the Cu K-edge. XRD under high pressure evidences anisotropic compression, the a-axis being more compressible than the c-axis. EXAFS yields the copper-oxygen bond length, from which the only internal parameter of the delafossite structure is deduced. The combination of anisotropic compression and the internal parameter decrease results in a regularization of the AlO(6) octahedra. The anisotropic compression is related to the chemical trends observed in the lattice parameters when Al is substituted by other trivalent cations. Both experiments evidence the existence of an irreversible phase transition that clearly manifests at 35 ± 2 GPa. The structure of the high-pressure polymorph could not be determined, but it implies a change of the Cu environment, which remains anisotropic. Precursor effects are observed from the lowest pressures, which are possibly related to crystal breaking at a submicroscopic scale with partial reorientation of the crystallites.

Anomalous high-pressure Jahn-Teller behavior in CuWO4

High-pressure optical-absorption measurements performed in CuWO(4) up to 20 GPa provide experimental evidence of the persistence of the Jahn-Teller (JT) distortion in the whole pressure range both in the low-pressure triclinic and in the high-pressure monoclinic phase. The electron-lattice couplings associated with the e(g)(E⊗e) and t(2g)(T⊗e) orbitals of Cu(2+) in CuWO(4) are obtained from correlations between the JT distortion of the CuO(6) octahedron and the associated structure of Cu(2+) d-electronic levels. This distortion and its associated JT energy (E(JT)) decrease upon compression in both phases. However, both the distortion and associated E(JT) increase sharply at the phase-transition pressure (P(PT)=9.9 GPa), and we estimate that the JT distortion persists for a wide pressure range not being suppressed up to 37 GPa. These results shed light on the transition mechanism of multiferroic CuWO(4), suggesting that the pressure-induced structural phase transition is a way to minimize the distortive effects associated with the toughness of the JT distortion.

Sensitivity and specificity of the Yang Tobin Index to predict extubation success in critical patients

Background: The Yang Tobin Index (Y/T) is a simple and objective measure to predict successful extubation. There are no Colombian studies supporting the use of Y/T as a predictor of successful ventilator weaning. Objective: To estimate the sensitivity and specificity of Y/T as predictor of weaning and to valuate the association with clinical and socio-demographic characteristics in adult patients at the intensive care unit. Methods: Retrospective study. We analyzed a database of 332 records of patients under mechanical ventilation (MV) for more than 48 hours, from January 2006 to December 2007, with spontaneous breathing trial and measurement of Y/T before extubation. Results: The sensitivity of Y/T was 98.6%, specificity 9.6%, positive predictive value 85.4%, egative predictive value 55.5%. The cumulative incidence of successful extubation was 84%. The greater incidence of unsuccessful extubation was associated with COPD (46.2%). The MV time period showed a direct proportional relationship with failed extubation (p=0.186). Conclusions: The Y/T index is not a good predictor of success of extubation in the study opulation. No association was found between clinical and sociodemographic characteristics of the opulation, with respect to the sensitivity and specificity of the Y/T as a predictor of success.

Citrus mealybug (Hemiptera: Pseudococcidae) movement and population dynamics in an arbor-trained vineyard

The citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae), is the main grapevine pest in vineyards in some countries, such as Spain and Brazil. In Galician vineyards (northwestern Spain), mealybug population levels are low because the accumulated degree-days are lower than in other grapevine-growing areas. The main problem caused by mealybugs is the transmission of viruses, even at low infestation levels. The active period of citrus mealybug in the study vineyard lasted from July until December, with an important movement peak at the end of July and August and a lower peak in November. The mealybug mainly moved upward along arbor-trained plants, and there were no important downward movements at the end of the season as has been described for other grapevine mealybugs. The mealybugs were normally restricted to the woody organs and were only present on leaves, branches, and green canes (always close to woody parts) in plants with high infestations. The movement of mealybugs between plants does not seem to take place by contact between green organs. Passive aerial transport and movement of pruning remains may play an important role in mealybug movement and thus in spread of the virus. The number of mealybugs carrying Grapevine leafroll-associated virus 3 (GLRaV-3) was found to represent approximately 75% of mealybugs caught in a GLRaV-3 infected vineyard.

Novel (60%) and recurrent (40%) androgen receptor gene mutations in a series of 59 patients with a 46,XY disorder of sex development

BACKGROUND

Androgen receptor (AR) gene mutations are the most frequent cause of 46,XY disorders of sex development (DSD) and are associated with a variety of phenotypes, ranging from phenotypic women [complete androgen insensitivity syndrome (CAIS)] to milder degrees of undervirilization (partial form or PAIS) or men with only infertility (mild form or MAIS).

OBJECTIVE

The aim of the study was to characterize the contribution of the AR gene to the molecular cause of 46,XY DSD in a series of Spanish patients.

SETTING

We studied a series of 133 index patients with 46,XY DSD in whom gonads were differentiated as testes, with phenotypes including varying degrees of undervirilization, and in whom the AR gene was the first candidate for a molecular analysis.

METHODS

The AR gene was sequenced (exons 1 to 8 with intronic flanking regions) in all patients and in family members of 61% of AR-mutated gene patients.

RESULTS

AR gene mutations were found in 59 individuals (44.4% of index patients), of whom 46 (78%) were CAIS and 13 (22%) PAIS. Fifty-seven different mutations were found: 21.0% located in exon 1, 15.8% in exons 2 and 3, 57.9% in exons 4-8, and 5.3% intronic. Twenty-three mutations (40.4%) had been previously described and 34 (59.6%) were novel.

CONCLUSIONS

AR gene mutation is the most frequent cause of 46,XY DSD, with a clearly higher frequency in the complete phenotype. Mutations spread along the whole coding sequence, including exon 1. This series shows that 60% of mutations detected during the period 2002-2009 were novel.

Bond length compressibility in hard ReB2 investigated by x-ray absorption under high pressure

This work describes x-ray absorption measurements under high pressure in ReB(2), complemented by ab initio calculations. The EXAFS analysis yields the average Re-B bond compressibility, which turns out to be χ(ReB) = 5.6(9) × 10(-4) GPa(-1). Combining this information with previous x-ray diffraction experiments we have characterized the network of covalent bonds responsible for the rigidity of the structure. The main conclusion is that the compression is anisotropic and nonhomogeneous, reflecting bonding differences between Re-B and B-B bonds and also between nonequivalent Re-B bonds. The layer defined by boron atoms tends to become flatter under high pressure. As a consequence, the structural rigidity, necessary to attain high hardness values, is compromised.