Generating Static Fluid Spheres by Conformal Transformations

We generate an explicit four-fold infinity of physically acceptable exact perfect fluid solutions of Einstein's equations by way of conformal transformations of physically unacceptable solutions (one way to view the use of isotropic coordinates). Special cases include the Schwarzschild interior solution and the Einstein static universe. The process we consider involves solving two equations of the Riccati type coupled by a single generating function rather than a specification of one of the two metric functions.Comment: 4 pages revtex4, two figures, Final form to appear in Phys. Rev.

Sumptuary Synergy: British Imperialism Through the Tartan and Slave Trades

Sumptuary laws have been a useful tool for various national powers in regulating subjects and to promote class differentiation and business interests. The genesis of this study was one such law, entitled the South Carolina Negro Act of 1735, stipulating that slave garments could only be made of low-quality textiles. These fabrics were reflective of slaves living in chattel environments, thus also representing a slave’s status in society. This law forbade slaves from wearing “any sort of garment or apparel whatsoever, finer, other or of greater value than Negro cloth, duffels, coarse kerseys, osnabrigs, blue linen, check linen, or coarse garlix, or calicoes, checked cottons or Scottish plaids.” As most of the textiles listed in the law were somewhat generic and manufactured in several places, it was interesting to the authors that those who crafted the law were more specific to incorporate “Scottish plaids” as one of the acceptable textiles for slave clothing. Textiles were one of the pillars of England and colonial America’s slave trading economy. In fact, the American Colonies had become one of England’s greatest customers, as they represented a distinct piece of what has been termed the “Triangular Trade.” Gold bullion and manufactured goods left England bound for India’s textile manufacturing centers and also to Western Africa’s slave trading centers. These economic inputs provided the fuel necessary to procure goods, such as, inexpensive Indian Madras textiles and humans/slaves, which would then leave India and Africa bound for the plantations of the United States and Caribbean islands. Ships returning from the Americas to England would then supply raw materials, such as sugar and cotton, to fuel English industries, thus completing the cycle. By 1773, America would consume approximately one quarter of products that were made in England

Sumptuary Synergy: British Imperialism Through the Tartan and Slave Trades

Sumptuary laws have been a useful tool for various national powers in regulating subjects and to promote class differentiation and business interests. The genesis of this study was one such law, entitled the South Carolina Negro Act of 1735, stipulating that slave garments could only be made of low-quality textiles. These fabrics were reflective of slaves living in chattel environments, thus also representing a slave’s status in society. This law forbade slaves from wearing “any sort of garment or apparel whatsoever, finer, other or of greater value than Negro cloth, duffels, coarse kerseys, osnabrigs, blue linen, check linen, or coarse garlix, or calicoes, checked cottons or Scottish plaids.” As most of the textiles listed in the law were somewhat generic and manufactured in several places, it was interesting to the authors that those who crafted the law were more specific to incorporate “Scottish plaids” as one of the acceptable textiles for slave clothing. Textiles were one of the pillars of England and colonial America’s slave trading economy. In fact, the American Colonies had become one of England’s greatest customers, as they represented a distinct piece of what has been termed the “Triangular Trade.” Gold bullion and manufactured goods left England bound for India’s textile manufacturing centers and also to Western Africa’s slave trading centers. These economic inputs provided the fuel necessary to procure goods, such as, inexpensive Indian Madras textiles and humans/slaves, which would then leave India and Africa bound for the plantations of the United States and Caribbean islands. Ships returning from the Americas to England would then supply raw materials, such as sugar and cotton, to fuel English industries, thus completing the cycle. By 1773, America would consume approximately one quarter of products that were made in England

Reliability and cultural applicability of the Greek version of the International Personality Disorders Examination.

BACKGROUND: The International Personality Disorders Examination (IPDE) constitutes the proposal of the WHO for the reliable diagnosis of personality disorders (PD). The IPDE assesses pathological personality and is compatible both with DSM-IV and ICD-10 diagnosis. However it is important to test the reliability and cultural applicability of different IPDE translations. METHODS: Thirty-one patients (12 male and 19 female) aged 35.25 ± 11.08 years, took part in the study. Three examiners applied the interview (23 interviews of two and 8 interviews of 3 examiners, that is 47 pairs of interviews and 70 single interviews). The phi coefficient was used to test categorical diagnosis agreement and the Pearson Product Moment correlation coefficient to test agreement concerning the number of criteria met. RESULTS: Translation and back-translation did not reveal specific problems. Results suggested that reliability of the Greek translation is good. However, socio-cultural factors (family coherence, work environment etc) could affect the application of some of the IPDE items in Greece. The diagnosis of any PD was highly reliable with phi >0.92. However, diagnosis of non-specfic PD was not reliable at all (phi close to 0) suggesting that this is a true residual category. Dianosis of specific PDs were highly reliable with the exception of schizoid PD. Diagnosis of antisocial and Borderline PDs were perfectly reliable with phi equal to 1.00. CONCLUSIONS: The Greek translation of the IPDE is a reliable instrument for the assessment of personality disorder but cultural variation may limit its applicability in international comparisons

The influence of ultrasonic pre-treatments on metal adsorption properties of softwood-derived biochar

Biomass-derived biochars are studied extensively because of their unique surface properties and efficiency in removing heavy metals from aqueous solution. Power ultrasound pre-treatments are interesting in this context, as they can make significant changes in the physicochemical characteristics of biomass. Herein, we studied their effect on adsorption characteristics of softwood biochar under different conditions of frequency, power, temperature and exposure time of ultrasound. The 40 kHz pre-treated samples exhibited around 0.3 to 0.65 mg/g increase in equilibrium adsorption capacity (Qe) which highly depends on the combination of power versus time and temperature of ultrasound. The isotherm and thermodynamic studies also showed that the mechanical effect of ultrasound plays a vital role in enhancing the surface. Results from this study demonstrated that ultrasound pre-treatment conditions influence the behaviour of biochar towards metal adsorption and ultrasonic pre-treatments can be used as an efficient processing method for biomass residues and the derived products. © 2020 Elsevier Lt

Pre- and post-pyrolysis effects on iron impregnation of ultrasound pre-treated softwood biochar for potential catalysis applications.

Slow pyrolysis is widely used to convert biomass into useable form of energy. Ultrasound pre-treatment assisted pyrolysis is a recently emerging methodology to improve the physicochemical properties of products derived. Biochar, the solid residues obtained from pyrolysis, is getting considerable attention because of its good physicochemical properties. Various modification techniques have been implemented on biochars to enhance their properties. Ultrasonic pre-treated wood biochar has showcased efficient surface and adsorption properties. Iron impregnated biochar is interesting as it has potentially proved the efficiency as an efficient low-cost catalyst. In this study, by combining the advantages of ultrasonic pre-treatment and iron impregnation, we have synthesized a series of Fe-impregnated biochar from softwood chips. Pre- and post-pyrolysis methods using a lab-scale pyrolyser had been implemented to compare the pyrolysis product yields and degree of impregnation. Biochars derived from ultrasound pre-treated woodchips by post pyrolysis demonstrated better impregnation of Fe ions on surface with better distribution of pyrolysis products such as biochar and biogas. The surface functionality of all ultrasound pre-treated biochars remained the same. However, post-pyrolysed samples at high frequency ultrasound pre-treatment showed better thermal stability. The chemical characteristics of these modified biochars are interesting and can indeed be used as a cost-effective replacement for various catalytic applications

Enhanced activation of ultrasonic pre-treated softwood biochar for efficient heavy metal removal from water

Physical and chemical modification on biochar is an interesting approach to enhance the properties and make them potential candidates in adsorption of heavy metals from water. Studies have shown that ultrasound treatments as well as alkali activations on biochar has positive impact on adsorption behaviour of the material. Base activation on biochar derived from ultrasound pre-treated woodchips were studied to understand the influence of ultrasound pre-treatment on chemical modification of biochar and the adsorption properties emerged from it. 40 and 170 kHz ultrasound pre-treated softwood woodchips were subjected to laboratory scale pyrolysis and the resulted biochars were treated with NaOH. The physicochemical properties were examined, and the adsorption experiments revealed that ultrasound pre-treatment assisted biochars have better adsorption capacity as compared to untreated biochar samples after activation. 170 kHz pre-treated sample exhibited an equilibrium adsorption capacity of 19.99 mg/g which is almost 22 times higher than that of corresponding non-activated sample. The ultrasound pre-treated samples showed improved competitive adsorption behaviour towards copper ions in comparison with nickel or lead. The overall study suggests that ultrasound pre-treated biochars combined with alkali activation enhances the heavy metal removal efficiency and these engineered biochars can be used as an effective adsorbent in the field of wastewater treatment. © 2021 Elsevier Lt

Printed microwave frequency humidity sensor operating with phase shifting scheme

This paper investigates a shifting sensing scheme combining slots, transmission lines, and printing technologies. This sensing scheme translates the electrical sensitivity of a transmission line conductor to the insertion phase as a measurement variable. A coplanar waveguide (CPW) based structure was designed, screen-printed, and tested on relative humidity (RH) conditions ranging from 22.8-75.3 %RH. For the first time, a composite material made of poly-pyrrole and TEMPO Oxidized Cellulose Nanofibers (TOCN/PPy) was integrated to the structure and studied as a humidity sensitive conductor in microwave frequencies. The measured sensitivity was 0.154°/%RH at 5.870 GHz, while insertion losses decreased by 1.26 dB. The effects of sensing layers thickness as well as trade-off considerations between phase sensitivity and signal attenuation were analyzed by simulation. © 2001-2012 IEEE

Cellulose reinforced electrospun chitosan nanofibers bio-based composite sorbent for water treatment applications

Electrospun chitosan–polyethylene oxide/TEMPO-oxidized cellulose (CS–PEO/TOC) bio-based composite was fabricated for the first time for water treatment applications. This new concept allows cellulose and chitosan to be combined in a simpler and efficient way, avoiding the use of harmful solvents, compared to previously published related work. The “Sandwich-like” material is composed of a porous oxidized cellulosic fibers central core (TOC handsheet) and a thin layer of electrospun CS–PEO nanofibers on both sides of the core. Average diameters for CS–PEO and TOC were 159.3 ± 33.7 nm and 21.7 ± 5.1 µm, respectively. Fourier Transform Infrared Spectroscopy (FTIR) was carried out on the bio-based composite. Results suggest that no covalent bonds are involved but rather electrostatic interactions occur which allows bonding of the electrospun nanofiber layers on TOC core and no delamination. CS–PEO electrospinning time was varied to study the effect of nanofiber’s coating weight on strength, permeability and adsorption capacity of the bio-based material. Mechanical properties of the composite were improved over the electrospun nanofiber mat. The CS–PEO provides greater elasticity (strain%) and the TOC provides a higher tensile strength to the material. However, tensile index was reduced by 48% with electrospinning time, while burst index was almost constant. The best conditions were achieved for 2 h electrospinning time. Under these conditions, a high permeable material (290.13 L/m2 hbar) was developed. The adsorption capacity for Cu (II) ions reached up to 27% with only 12 mg of chitosan onto the CS–PEO/TOC (12.42 mg/g). The data fit better to the pseudo-second order model, suggesting chemisorption as the main mechanism involved for copper adsorption. This study opens-up potential opportunities for the development of a robust material for wastewater applications at an industrial scale. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to Springer Nature B.V

Temporal characterization of a multi-wavelength Brillouin-erbium fiber laser

This paper provides the first detailed temporal characterization of a multi-wavelength-Brillouin-erbium fiber laser (MWBEFL) by measuring the optical intensity of the individual frequency channels with high temporal resolution. It is found that the power in each channel is highly unstable due to the excitation of several cavity modes for typical conditions of operation. Also provided is the real-time measurements of the MWBEFL output power for two configurations that were previously reported to emit phase-locked picosecond pulse trains, concluded from their autocorrelation measurements. Real-time measurements reveal a high degree of instability without the formation of a stable pulse train. Finally, we model the MWBEFL using coupled wave equations describing the evolution of the Brillouin pump, Stokes and acoustic waves in the presence of stimulated Brillouin scattering, and the optical Kerr effect. A good qualitative consistency between the simulation and experimental results is evident, in which the interference signal at the output shows strong instability as well as the chaotic behavior due to the dynamics of participating pump and Stokes waves