Exchange Sites Research Articles

Effect of tubulin self-association on GTP hydrolysis and nucleotide exchange reactions

We investigated how the self-association of isolated tubulin dimers affects the rate of GTP hydrolysis and the equilibrium of nucleotide exchange. Both reactions are relevant for microtubule (MT) dynamics. We used HPLC to determine the concentrations of GDP and GTP and thereby the GTPase activity of SEC-eluted tubulin dimers in assembly buffer solution, free of glycerol and tubulin aggregates. When GTP hydrolysis was negligible, the nucleotide exchange mechanism was studied by determining the concentrations of tubulin-free and tubulin-bound GTP and GDP. We observed no GTP hydrolysis below the critical conditions for MT assembly (either below the critical tubulin concentration and/or at low temperature), despite the assembly of tubulin 1D curved oligomers and single-rings, showing that their assembly did not involve GTP hydrolysis. Under conditions enabling spontaneous slow MT assembly, a slow pseudo-first-order GTP hydrolysis kinetics was detected, limited by the rate of MT assembly. Cryo-TEM images showed that GTP-tubulin 1D oligomers were curved also at 36 °C. Nucleotide exchange depended on the total tubulin concentration and the molar ratio between tubulin-free GDP and GTP. We used a thermodynamic model of isodesmic tubulin self-association, terminated by the formation of tubulin single-rings to determine the molar fractions of dimers with exposed and buried nucleotide exchangeable sites (E-sites). Our analysis shows that the GDP to GTP exchange reaction equilibrium constant was an order-of-magnitude larger for tubulin dimers with exposed E-sites than for assembled dimers with buried E-sites. This conclusion may have implications on the dynamics at the tip of the MT plus end.

Halomethoxybenzenes in air of the Nordic region

Halomethoxybenzenes (HMBs) are a group of compounds with natural and anthropogenic origins. Here we extend a 2002–2015 survey of bromoanisoles (BAs) in the air and precipitation at Råö on the Swedish west coast and Pallas in Subarctic Finland. New BAs data are reported for 2018 and 2019 and chlorinated HMBs are included for these and some previous years: drosophilin A methyl ether (DAME: 1,2,4,5-tetrachloro-3,6-dimethoxybenzene), tetrachloroveratrole (TeCV: 1,2,3,4-tetrachloro-5,6-dimethoxybenzene), and pentachloroanisole (PeCA). The order of abundance of HMBs at Råö was ΣBAs > DAME > TeCV > PeCA, whereas at Pallas the order of abundance was DAME > ΣBAs > TeCA > PeCA. The lower abundance of BAs at Pallas reflects its inland location, away from direct marine influence. Clausius-Clapeyron (CC) plots of log partial pressure (Pair)/Pa versus 1/T suggested distant transport at both sites for PeCA and local exchange for DAME and TeCV. BAs were dominated by distant transport at Pallas and by both local and distant sources at Råö. Relationships between air and precipitation concentrations were examined by scavenging ratios, SR = (ng m−3)precip/(ng m−3)air. SRs were higher at Pallas than Råö due to greater Henry's law partitioning of gaseous compounds into precipitation at colder temperatures. DAME is produced by terrestrial fungi. We screened 19 fungal species from Swedish forests and found seven of them contained 0.01–3.8 mg DAME per kg fresh weight. We suggest that the volatilization of DAME from fungi and forest litter containing fungal mycelia may contribute to atmospheric levels at both sites.

On engliscre spræce? Old English and the politics of intralingual translation

The idea that translation from Old to Modern English involves “updating” within the same language—rather than what Jakobson calls “translation proper”—is a pervasive one. In this article I argue that this “interlingual fallacy” still conditions the ways in which the language and early medieval period are represented in the public sphere today. Focussing on two high-profile engagements with the language—Seamus Heaney’s Beowulf and Paul Kingsnorth’s shadow language in his novel The Wake—, I argue that the intralingual fallacy has had the dual effect of marginalising the act of translation as a site of cultural exchange, and limiting the possibilities for interrogating those productive issues it shares with interlingual translation. Several examples are given of recent projects that set out to problematise this narrative of intralingual transfer, and that present a way forward for further integrating Old English into the contemporary discourse on translation.

Could Size Moderate Managerial Ownership, Institutional Ownership, and Audit Quality of Tax Avoidance Occurs in Southeast Asia’s Banking?

This study aims to determine the effect of managerial ownership, institutional ownership, and audit quality on tax avoidance and to determine the role of firm size as a moderator in strengthening or weakening the influence of the three independent variables on tax avoidance. The population used in this study is the financial statements and annual reports of banking companies in Southeast Asia which are available on the stock exchange sites of each country and the official websites of related companies in the 2015-2019 period. The sampling technique is used a purposive sampling method with the final result of as many as 144 units of analysis. Analysis of the data used is Multiple Linear Regression Analysis to determine the independent influence variables on dependence and Moderation Regression Analysis to determine the role of moderating variables. The result shows that managerial ownership and audit quality do not affect tax avoidance, while institutional ownership can negatively affect tax avoidance. Moderation analysis shows that firm size can affect independent institutional ownership variables and audit quality on tax avoidance. However, managerial ownership does not affect tax avoidance.

The potential and pitfalls of co-producing urban knowledge: Rethinking spaces of engagement

Securing sustainable and just transition pathways in cities is recognised as key to addressing global environmental challenges. There is increasing acceptance that transformative change in cities must be shaped by the co-production of knowledge between diverse partners. The creation of spaces of collaboration, referred to in the literature as ‘third spaces’, is integral to such co-production of knowledge. However, evidence to support a direct relationship between third spaces of engagement and securing urban transformation is largely undocumented. This paper deepens and develops the idea of shared spaces for knowledge co-production by drawing on the experiences of City officials and PhD researchers in a City-University knowledge partnership in Cape Town. It uses the data to critique the third space for its limited engagement with how the relationship between individual knowledge brokers and their home institutions effects change. The findings of the paper show that, despite the benefits of boundary crossing between the academy and practice, such crossings also leave individuals peripheralised from their ‘home’ institutions. This disconnect and sense of ‘homelessness’ limits the potential of co-production to affect urban transformation. To address the conceptual lacunae of the third space, I develop the idea of the portal to reflect the dynamic exchange required between individuals and their home institutions for realising relevant change. The form of the portal is not spatially bound, but reflects dynamic processes of entering and exiting sites of knowledge exchange to secure a sense of belonging. By highlighting the need to include processes for anchoring institutional learning, the concept of portals for knowledge exchange offers additional scope for securing urban transformation.

Hierarchical Polyaniline Core-Shell Nanocomposites Coated on Modified Graphite for Improved Electrical Conductivity Performance.

Graphite has recently gained scientific and industrial attention due to its high electrical conductivity. In the current endeavor, a new way to fabricate novel and multifunctional nanocomposites using functional graphite (FG) as filler is presented. The fabrication of multilayered conducting composites of PANi/PMMA/PPG-b-PEG-b-PPG was carried out via in situ polymerization, using polyaniline (PANi), poly(methyl methacrylate) (PMMA) and block copolymer as matrices in the presence of FGfiller. The growth of PANi chains is manifested by PMMA due to the formation of H-bonding between imine and carbonyl groups of PANi and MMA units, respectively, and are responsible for ion exchange sites. FTIR spectroscopy was used for structural elucidation of composites while elemental analysis was accomplished by XPS and EDX spectroscopy. The morphology of the prepared PANi/PMMA/PPG-b-PEG-b-PPG@FG composites was inspected by the SEM. The structure and crystallinity of the composites was investigated via XRD. The improved thermal stability and properties of the nanocomposites were observed using TGA and DSC. The conductivity measurements were used to characterize the electrical conductivity performance of the resulting composites. The presence of functional filler as well as polyaniline shows a significant contribution towards the enhancement of electrical conductivity of PANi/PMMA/PPG-b-PEG-b-PPG@FG nanocomposites.

Ion regulation at gills precedes gas exchange and the origin of vertebrates.

Gas exchange and ion regulation at gills have key roles in the evolution of vertebrates1-4. Gills are hypothesized to have first acquired these important homeostatic functions from the skin in stem vertebrates, facilitating the evolution of larger, more-active modes of life2,3,5. However, this hypothesis lacks functional support in relevant taxa. Here we characterize the function of gills and skin in a vertebrate (lamprey ammocoete; Entosphenus tridentatus), a cephalochordate (amphioxus; Branchiostoma floridae) and a hemichordate (acorn worm; Saccoglossus kowalevskii) with the presumed burrowing, filter-feeding traits of vertebrate ancestors6-9. We provide functional support for a vertebrate origin of gas exchange at the gills with increasing body size and activity, as direct measurements in vivo reveal that gills are the dominant site of gas exchange only in ammocoetes, and only with increasing body size or challenges to oxygen supply and demand. Conversely, gills of all three taxa are implicated in ion regulation. Ammocoete gills are responsible for all ion flux at all body sizes, whereas molecular markers for ion regulation are higher in the gills than in the skin of amphioxus and acorn worms. This suggests that ion regulation at gills has an earlier origin than gas exchangethat is unrelated to vertebrate size and activity-perhaps at the very inception of pharyngeal pores in stem deuterostomes.

The effect of reaction condition on catalytic cracking of wheat straw pyrolysis volatiles over char-based Fe–Ni–Ca catalyst

In this study, the catalytic reforming of wheat straw pyrolysis volatiles over char-based Fe–Ni–Ca catalyst in a fixed bed reactor to investigate the influence of heating rate, pyrolysis temperature and catalyst calcination temperature on the yield of bio-oil, char and pyrolysis gas was presented. Char-based Fe–Ni–Ca catalysts had good activity for the removal of heavy oil, the heavy oil yield is 0.43% with 500 °C pyrolysis temperature and 5 °C/min heating rate. The maximum yield of hydrogen (288.41 mL/g) and combustible gas (hydrogen, methane and carbon monoxide; 403.45 mL/g) were obtained at a pyrolysis temperature of 800 °C and 10 °C/min heating rate. XPS, H2-TPR, XRD, TEM, SEM-EDS and BET were employed to analyze char-based Fe–Ni–Ca catalyst. Characterization results reveal that heating rate, pyrolysis temperature and catalyst calcination temperature had a significant effect on the distribution of active phase. Comparing to 800 °C, the diffraction peaks of Fe, Fe0.64Ni0.36, and Fe2O3 become weak as 500 °C, the particle size changed from 23.17 nm to 24.34 nm. At 500 °C, the power of the diffraction peak decreases successively from Fe2O3, Fe, and Fe0.64Ni0.36. At 800 °C, the highest intensity of the diffraction peak is Fe, followed by Fe2O3. The high activity of char-based Fe–Ni–Ca catalyst is also attributed to the robust adsorption of CO2 forming CaCO3 species facilitated on the oxide ion vacancy site of CaO acting as oxygen exchange site. Also, the char-based Fe–Ni–Ca catalyst can be utilized as an appropriate candidate to crack the bio-oil. The pyrolysis temperature of 800 °C and the heating rate of 10 °C/min can be used as the best reaction conditions for industrial hydrogen production.

Thermal stabilization of extraframework Cs+ in zeolite 13X

Given the reversible nature of ion exchange, Cs+-exchanged zeolite 13X was thermally treated to safely retain extraframework Cs+. By thermal gravimetric-differential scanning calorimeter (TG-DSC) analysis, both endothermic and exothermic peaks, indicative of phase transitions, gradually shifted to higher temperatures at the higher surface loading of Cs+ (i.e., [Cs+]0/[NaX]0), indicating that extraframework Cs+ stabilized the zeolite framework. By thermal treatment at ≤ 800 °C, X-ray diffraction (XRD) showed that the samples with [Cs+]0/[NaX]0 = 0.5 and 5 mmol/g maintained the faujasite framework. Nonetheless, as indicated by Cs LIII-edge X-ray absorption spectroscopy (XAS) analysis, the Cs-Si(Al) interaction at ∼4.37 Å became stronger relative to the Cs-O interaction at ∼2.98 Å with the increasing treatment temperature, indicating that thermally induced dehydration caused extraframework Cs+ to migrate from spacious sites to confined (less exchangeable) sites. Thus, the redistribution of extraframework Cs+ among exchange sites was responsible for the lower leaching with the increasing treatment temperature. On the other hand, by thermal treatment at ≥ 900 °C, bulk-phase analyses such as XRD, scanning electron microscopy, and surface area measurement showed that the zeolite framework completely broke down to form non-porous phases. The XAS analysis further indicated that Cs+ was mainly incorporated into amorphous phases at 900 °C and pollucite at ≥ 1,000 °C. This was consistent with the markedly low Cs+ leaching for the ≥ 900 °C-treated samples. Since pollucite can provide the greatest retainability of Cs+, the thermal treatment leading to its formation is recommended before storing Cs+-exchanged zeolite 13X at nuclear waste repositories.

Adsorptive removal of beryllium by Fe-modified activated carbon prepared from lotus leaf.

Lotus leaf was used as raw material to prepare HNO3-activated carbon with 1.5:1 (HNO3:lotus leaf) (wt:wt) impregnation. Then, the activated carbon was modified by Fe(NO3)3 to obtain Fe-activated carbon (Fe-AC). The adsorption test results show that Fe-AC maximum saturated adsorption capacity (Qm) is 45.68mg/g when the Fe(NO3)3 loading is 5% of the total activated carbon, pH = 6, and the temperature is 35 ℃. The adsorption effect of Fe-AC under neutral conditions is better than that under alkaline and acidic conditions. The modified activated carbon has better adsorption selectivity. The obtained material (Fe-AC) was characterized by N2 adsorption-desorption isotherm, SEM, FT-IR, BET, XRD, XPS, and pHpzc. The total pore volume, specific surface area, and zero charges of modified activated carbon were increased. The types of modified functional groups were reduced, and the iron reacted with the functional groups, providing ion exchange sites for the adsorption of beryllium. The adsorption thermodynamics showed that the adsorption process was spontaneous and endothermic. The adsorption mechanism of Fe-AC to beryllium is mainly chemical adsorption.

Microhydration of the metastable N-protomer of 4-aminobenzoic acid by condensation at 80K: H/D exchange without conversion to the more stable O-protomer.

4-aminobenzoic acid (4ABA) is a model scaffold for studying solvent-mediated proton transfer. Although protonation at the carboxylic group (O-protomer) is energetically favored in the gas phase, the N-protomer, where the proton remains on the amino group, can be kinetically trapped by electrospray ionization of 4ABA in an aprotic solvent such as acetonitrile. Here, we report the formation of the hydrated deuterium isotopologues of the N-protomers, RND3 +·(H2O)n=1-3, (R = C6H4COOD), which are generated by condensing water molecules onto the bare N-protomers in a liquid nitrogen cooled, radiofrequency octopole ion trap at 80K. The product clusters are then transferred to a 20K cryogenic ion trap where they are tagged with weakly bound D2 molecules. The structures of these clusters are determined by analysis of their vibrational patterns, obtained by resonant IR photodissociation. The resulting patterns confirm that the metastable N-protomer configuration remains intact even when warmed by the sequential condensation of water molecules. The attachment of H2O molecules onto the RND3 + head group also affords the opportunity to explore the possibility of H/D exchange between the acid scaffold and the proximal water network. The spectroscopic results establish that although the RND3 +·(H2O)n=1,2 clusters are formed without H/D exchange, the n = 3 cluster exhibits about 10% H/D exchange as evidenced by the appearance of the telltale HOD bands. The site of exchange on the acid is determined to be the acidic OH group by the emergence of the OH stretching fundamental in the -COOH motif.

Slantwise Convection in the Irminger Sea

AbstractThe subpolar North Atlantic is a site of significant carbon dioxide, oxygen, and heat exchange with the atmosphere. This exchange, which regulates transient climate change and prevents large‐scale hypoxia throughout the North Atlantic, is thought to be mediated by vertical mixing in the ocean's surface mixed layer. Here we present observational evidence that waters deeper than the conventionally defined mixed layer are affected directly by atmospheric forcing in this region. When northerly winds blow along the Irminger Sea's western boundary current, the Ekman response pushes denser water over lighter water, potentially triggering slantwise convection. We estimate that this down‐front wind forcing is four times stronger than air–sea heat flux buoyancy forcing and can mix waters to several times the conventionally defined mixed layer depth. Slantwise convection is not included in most large‐scale ocean models, which likely limits their ability to accurately represent subpolar water mass transformations and deep ocean ventilation.

A Performance Enhancement Method for MEMS Thermopile Pirani Sensors Through In-Situ Integration of Nanoforests

In this letter, we report a performance enhancement approach for MEMS thermopile Pirani sensors through in-situ integration of nanoforests. The nanoforests not only increase the light absorption of the thermopile, resulting in an improved output voltage, but also increase the contact area and heat exchange sites for gas molecules due to their high porosity and large surface area to volume ratio, subsequently improve the gas heat conduction, extend pressure detection range and increase sensitivity of the Pirani sensor. With integration of the nanoforests, the lower detection limit of the sensor is widened by one order of magnitude compared with the pristine sensor, and the maximum increment in sensitivity reached 56.7%. Moreover, such a sensor can be easily fabricated with a CMOS-compatible process, thus is suitable for mass production. This work provides a new route to enhance performance of current MEMS thermopile Pirani sensors.

A highly efficient and durable solar evaporator based on hierarchical ion‐selective nanostructures

AbstractSolar‐driven vapor generation technology can directly produce clean water, but existing strategies remain challenging in achieving both high evaporation performance and good salt resistance due to complex water‐thermal management. Here, we constructed hydrogel‐based hierarchically nanostructured evaporator (HNE) with vertically aligned micro water transportation pathways and water confined ion selective nanochannels. Based on the polarity modified hierarchical structures and umbrella‐shaped geometry design, HNEs can achieve high‐speed water transfer at low saturated water content to realize efficient heat energy confinement, and provide more heat exchange sites. Consequently, an exciting water evaporation rate of 3.68 kg m−2 h−1 and the efficiency of 91.1% were achieved under 1 sun solar radiation. More importantly, the overlapping electrical double layer in the narrow nanochannels endows the ions selectivity of the nanochannel to reject anions, resulting in reliable long‐term salt resistance. The ingenious design was creatively confirmed by streaming potential and validated during long‐term efficient work.image

Victorian Women Poets

Victorian Women Poets Heather Bozant Witcher (bio) A. Mary F. Robinson was best known, to her English audience, for her poetry and, to her French audience, as a woman of letters. So begins the introduction to Robinson's "Anglo-French" life in Patricia Rigg's A. Mary F. Robinson (Montreal: McGill-Queen's Univ. Press, 2021). Rigg seeks to reconcile these dual identities in this comprehensive and engaging biographical study. Rigg's book offers a nuanced look at an international poet: the unorthodoxy of Robinson's life, the integration of various literary styles (poetics, historical, biographical), and her Anglo-French identity. Highlighting Anglo-French literary communities and the social components of Robinson's life, Rigg's biography sets the tone for this year's scholarship on Victorian women poets. Its rich, layered approach—bringing together extensive archival material with personal and familial relationships (Rigg details her time in the Robinson family home and her relationship with Robinson's great-granddaughter by marriage)—offers a methodology that foregrounds materiality, affect, and form. Similarly, James Diedrick's edited edition for the MHRA Jewelled Tortoise Series, Mathilde Blind: Selected Fin-de-Siècle Poetry and Prose (Cambridge, U.K.: Modern Humanities Research Association, 2021) foregrounds Blind's contributions as a transnational and displaced (or expatriate) writer. His scholarly edition of Blind's late poetry brings three volumes (published between 1889 and 1895) together, alongside selections of her reviews and literary essays, to foreground Blind's experimental verse forms and affiliations with leading Decadent communities. The scholarship, then, of 2021 predominantly interrogates an intersectional approach to Victorian women poets: from exploring the ecological impact of Decadent poets to the intersections of poetry with a wide range of nineteenth-century sciences, transnational and cosmopolitan outlooks, and various modes of being. In this way, Victorian poetry becomes a site of curiosity, exchange, and engagement—in all senses of the word—with the world. In "Haptic Ekphrasis" (Victorian Studies 64, no. 1 [2021]: 88–114), Jill R. Ehnenn reconsiders the ekphrastic text, usually defined as a technology of vision: the relationship between word and image. In the Victorian period—and more broadly—ekphrasis involves not only vision but a technology of feeling, "both touch and emotion" (p. 89). In what Ehnenn calls "haptic ekphrasis," she identifies the centrality of affect and the sensing body as a method of [End Page 418] phenomenological interpretation and poetic encounter, or poetry's ability to do something, to move our bodies and brains into reconsiderations of the self/ object within the world (in both the nineteenth century and our world today). She makes three central claims. Focusing on haptics alongside vision enables reconsiderations of poetic form that foreground the "visceral register of experience" (p. 92). New ways of analyzing poetry emerge when we consider the tactility of the ekphrastic text or the arousal of emotion when we are attuned to meter and metrical variance. Rather than viewing ekphrasis as a description of an art object, haptic ekphrasis documents the poet's encounter with the art object. When reading poems like Elizabeth Barrett Browning's "Hiram Powers' Greek Slave" (1850) or Julia Margaret Cameron's "On a Portrait" (1876), with priority given to haptics, formal readings encourage sympathy for the object and what it represents. The language of sympathy here foregrounds another of Ehnenn's claims: that haptic ekphrasis resonates with the nineteenth-century discursive shift from sympathy to empathy (Einfühlung). Most intriguingly, perhaps, Ehnenn identifies haptic ekphrasis as a strategic technique for "minoritarian" (women and queer) writers (p. 100). Through insightful close readings of poetry by John Gray, Olive Custance, Julia Margaret Cameron, Graham R. Tomson, and the Bengali poet Sarojini Naidu, Ehnenn showcases how haptic readings communicate the complexities of lived experiences as a woman or queer poet. Not only, then, does haptic ekphrasis permit realistic detail and transportation of feeling, but "ekphrasis built on the haptic . . . permits the author to safely articulate the ineffable, the non-canonical, and the private" (p. 105). In providing a new framework from which to understand ekphrasis, Ehnenn points toward the phenomenological and epistemological potentials of poetic experience and poetic encounter—for both the Victorians and the twenty-first-century reader. Sight and...

Pilot study comparison of regenerable and emerging single-use anion exchange resins for treatment of groundwater contaminated by per- and polyfluoroalkyl substances (PFASs)

This study reports the results of an 8-month pilot study comparing both regenerable and emerging single-use anion exchange resins (AERs) for treatment of per- and polyfluoroalkyl substances (PFASs) at a source zone impacted by historical use of aqueous film-forming foam (AFFF). Two regenerable (Purolite A860 and A520E) and three single-use (Purolite PFA694E, Calgon CalRes 2301, and Dowex PSR2+) AERs were tested in parallel, collecting effluent samples after treatment for 30-sec and 2-min total empty bed contact time (EBCT). Results demonstrate that single-use AERs significantly outperform regenerable resins, particularly for treatment of long-chain perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs). No detectable concentrations of ≥C7 PFCAs or PFSAs were observed within 150,000 bed volumes (BVs) after treatment with the single-use resins (2-min EBCT). Analysis of effluent samples following 30-sec EBCT treatment shows that even the shortest-chain PFSAs do not reach 50% breakthrough within the first 350,000 BVs, though differences in removal of short-chain PFCAs was less dramatic. The regenerable polyacrylic A860 resin performed very poorly compared to all polystyrene resins, with >90% breakthrough of all PFASs occurring within 10,000 BVs. The greater affinity of polystyrene resins is attributed to increased hydrophobic interactions in addition to electrostatic ion exchange. Analysis of breakthrough profiles reveals empirical correlation with ion exchange affinity coefficients (logKex) measured in batch experiments. Postmortem analysis of PFASs extracted from spent resins revealed chromatographic elution behavior and competition among PFASs for adsorption to the resins. PFSAs and long-chain PFCAs were preferentially adsorbed to earlier sections in the AER columns, whereas short-chain PFCAs were competitively displaced towards the later sections of the columns and into the effluent, consistent with effluent concentrations of the latter structures exceeding influent values. These results provide insights into the mechanisms that govern PFAS adsorption to AERs in real multisolute groundwater matrices and support findings from other diverse sites regarding PFAS affinity, elution behavior, and competition for exchange sites.

Metalation calculators for E. coli strain JM109 (DE3): aerobic, anaerobic, and hydrogen peroxide exposed cells cultured in LB media.

Three Web-based calculators, and three analogous spreadsheets, have been generated that predict in vivo metal occupancies of proteins based on known metal affinities. The calculations exploit estimates of the availabilities of the labile buffered pools of different metals inside a cell. Here, metal availabilities have been estimated for a strain of Escherichia coli that is commonly used in molecular biology and biochemistry research, e.g. in the production of recombinant proteins. Metal availabilities have been examined for cells grown in Luria-Bertani (LB) medium aerobically, anaerobically, and in response to H2O2 by monitoring the abundance of a selected set of metal-responsive transcripts by quantitative polymerase chain reaction (qPCR). The selected genes are regulated by DNA-binding metal sensors that have been thermodynamically characterized in related bacterial cells enabling gene expression to be read out as a function of intracellular metal availabilities expressed as free energies for forming metal complexes. The calculators compare these values with the free energies for forming complexes with the protein of interest, derived from metal affinities, to estimate how effectively the protein can compete with exchangeable binding sites in the intracellular milieu. The calculators then inter-compete the different metals, limiting total occupancy of the site to a maximum stoichiometry of 1, to output percentage occupancies with each metal. In addition to making these new and conditional calculators available, an original purpose of this article was to provide a tutorial that discusses constraints of this approach and presents ways in which such calculators might be exploited in basic and applied research, and in next-generation manufacturing.

Best practices of testing database manipulation code

Software testing enables development teams to maintain the quality of a software system while it evolves. The database manipulation code requires special attention in this context. However, it is often neglected and suffers from software maintenance problems.In this paper, we study the current state-of-the-practice in testing database manipulation code. We first analysed the tests of 72 open-source projects to gain insight into the coverage of database access code. The database was poorly tested: 46% of the projects did not cover with tests half of their database access methods, and 33% did not cover the database code at all. This poor coverage motivated us to study developers’ challenges and best practices. (i) First, we analysed 532 questions on Stack Exchange sites and deduced a taxonomy of issues. Developers mostly looked for general best practices to test database access code. Their technical questions were related to database management, mocking, parallelisation, or framework/tool usage. (ii) Next, we examined the answers to these questions. We manually labelled 598 answers to 255 questions. We distinguished 363 solutions and organised them in a taxonomy of best practices. Most of the suggestions considered the testing environment and recommended various tools or configurations. The second largest category was database management, where many addressed database initialisation and clean-up between tests. Other categories pertained to code structure or design, concepts, performance, processes, test characteristics, test code, and mocking. We illustrate the two taxonomies through intriguing examples.

Research on the flotation of sphalerite and germanium-bearing sphalerite activated by copper ion and its mechanism difference

Although numerous studies on the flotation activation of sphalerite by copper ion have been reported, but there are still some important problems to be studied further. Previous research works did not comprehensively investigate the effect of germanium content on the floatability of germanium-bearing sphalerite, and did not obtain direct evidence of the activation difference of copper ions on sphalerite and germanium-bearing sphalerite. In this paper, the effect of germanium content in sphalerite on the floatability of sphalerite was studied using micro flotation test. The difference mechanism between copper ion activated sphalerite and germanium-bearing sphalerite was studied using surface adsorption amount measurements, Zeta potential measurements, local electrochemical impedance spectroscopy analysis, and time-of-flight secondary ion mass spectrometry. The results show that the increase of germanium content reduces the floatability of sphalerite and reduces the adsorption of copper and xanthate. Especially after activation by copper ions, the downward trend is more obvious. The reason for the less adsorption of copper and xanthate on the surface of germanium-bearing sphalerite is that Ge occupies the exchange site of Cu and Zn.

Eco-friendly recycling of silicon−rich lye: Synthesis of hierarchically structured calcium silicate hydrate and its application for phosphorus removal

Silicon−rich lye (SRL), a byproduct generated from pre−treatment of coal−based solid waste (CSW), was considered as a preponderant silicon source to prepare hierarchically nanostructured calcium silicate hydrate (C-S-H). Through the novel mild−causticization synthesis strategy, C-S-H was prepared under optimal caustic process conditions at time of 3 h, temperature of 80 °C, Ca/Si of 1.25:1, and active CaO to obtain a conversion rate of Si up to 97.33 % during the high−value utilization of SRL. The synthesized C-S-H possesses abundant mesoporous structure and massive exchangeable active sites, whose formation is advanced through an appropriate elevation regulation of caustic temperature and time. The silicate chain depolymerization occurs to C-S-H prepared in the highly alkaline system at higher caustic temperature, longer caustic period, especially at existence of massive sodium ions, but it presents higher polymerization degree at more aluminum co-existing. The adsorption capacity up to 119.27 mg/g for C-S-H presents a valid removal performance toward phosphorus in the wastewater than massive present reports. The removal mechanism of phosphorus can be identified as the surface chemisorption and formation of calcium phosphate co-precipitation. This study can provide considerable and potential guidance to the coordinated disposal between industrial solid wastes and wastewater purification.