Bulk Reduction Research Articles

Microstructural characterization of field assisted sintered bulk nanostructured V-4Cr-4Ti alloys

ABSTRACTThis article deals with synthesis of single-phase bulk nanostructured V-4Cr-4Ti alloy by mechanical alloying and field assisted sintering. Mechanically alloyed powders were sintered at 1050 and 1100°C with different sintering time. Both powder and sintered samples were subjected to structural and morphological characterization using x-ray diffraction and electron microscopy studies. x-ray diffraction and transmission electron microscopy studies of sintered samples confirm that field assisted sintering technique aids nanostructuring in V-4Cr-4Ti alloy. Microstructural parameters of sintered samples were calculated from x-ray diffraction patterns. Role of sintering variables on the microstrain evolution and subsequent domain size reduction in bulk V-4Cr-4Ti alloy are briefly discussed. Optimal sintering parameters to achieve nanostructured V-4Cr-4Ti alloy by field assisted sintering were deduced. Micro-hardness and relative density of sintered V-4Cr-4Ti alloy are found to increase with sintering temperature and sintering time.

High‐Temperature Treatment of Li‐Rich Cathode Materials with Ammonia: Improved Capacity and Mean Voltage Stability during Cycling

Li‐rich electrode materials of the family xLi2MnO3·(1−x)LiNiaCobMncO2 (a + b + c = 1) suffer a voltage fade upon cycling that limits their utilization in commercial batteries despite their extremely high discharge capacity, ≈250 mA h g−1. Li‐rich, 0.35Li2MnO3·0.65LiNi0.35Mn0.45Co0.20O2, is exposed to NH3 at 400 °C, producing materials with improved characteristics: enhanced electrode capacity and a limited average voltage fade during 100 cycles in half cells versus Li. Three main changes caused by NH3 treatment are established. First, a general bulk reduction of Co and Mn is observed via X‐ray photoelectron spectroscopy and X‐ray absorption near edge structure. Next, a structural rearrangement lowers the coordination number of CoO and MnO bonds, as well as formation of a surface spinel‐like structure. Additionally, Li+ removal from the bulk causes the formation of surface LiOH, Li2CO3, and Li2O. These structural and surface changes can enhance the voltage and capacity stability of the Li‐rich material electrodes after moderate NH3 treatment times of 1–2 h.

ITPR - a new methodical approach for temperature programmed reduction of catalysts with improved sensitivity

A new method for temperature programmed reduction (TPR) of reducible bulk or supported metal compounds with hydrogen is presented. The setup, involving a flame ionization detector (FID) and methanizer, allows to study the reduction behavior of amounts down to 0.1mg as shown for the reduction of Cu2O. By co-feeding CO2 in excess, hydrogen is converted into methane which is then detected by the FID.

Size Reduction of Bulk Alumina for Mass Production of Fluorescent Nanoalumina by Fungus Humicola sp.

In recent years, nanomaterials have made their way into hundreds of biomedical, life-sciences and technological applications. One such nanomaterial of extreme importance is nanoalumina (Al2O3 nanoparticles). This nanomaterial is an epitome of diversity with applications exhibited in the fields of catalysis, cosmetics, theranostics, energy generation, biosensors, drug-delivery, tumor-regression, etc. However, problems persist in terms of biocompatibility, cost-effectiveness, reproducibility and mass-production of nanoalumina by the presently existent physical, chemical and biological methodologies. Herein, we for the first time are presenting a top-down biofabrication method by which size reduction of commercial bulk alumina/aluminum oxide (5 µm) into nanoalumina (5–25 nm) is carried out by a thermophilic fungus Humicola sp. within 96 h of reaction at just 50 °C. The so-formed nanoalumina is highly stable, water dispersible, fluorescent and natural protein capped; characterization engaged standard techniques. These nanoparticles exhibit anti-bacterial properties against Gram-positive Bacillus subtilis strain and may serve as broad spectrum bactericidal agents. We believe that our novel top-down approach may be extensively used in the facile, inexpensive, eco-friendly and reliable fabrication of abundant quantities of nanomaterials of different chemical compositions, sizes and shapes with better control and predictability over the properties as derived from their substrates. The mechanistic aspect of said protocol is underway.

Improved CO Oxidation Activity of 3DOM Pr-Doped Ceria Catalysts: Something Other Than an Ordered Macroporous Structure

It is demonstrated that the synthesis procedure for preparing three-dimensionally ordered macroporous (3DOM) Pr-doped ceria catalysts using a polymethylmethacrylate (PMMA) template not only affects the porous structure, but also the chemistry of the ceria surface. The PMMA template does not affect the crystalline features (type of phases, crystallite size, and cell parameter) of Pr-doped ceria, Ce and Pr location into the particles, and the bulk reduction of the Ce-Pr mixed oxide catalysts. On the contrary, the utilization of the PMMA template improves both the porosity and surface redox properties. 3DOM Ce-Pr mixed oxide catalysts combine micro, meso, and macropores, the most area being in the macropore range, while a reference unshaped catalyst presents poor porosity in all ranges. However, the catalyzed CO oxidation rates do not correlate with the surface area of the catalysts (neither micro nor meso/macro). The Ce-Pr-3DOM catalyst also presents improved surface reducibility with regards to the counterpart reference material prepared without the template, and improved redox behavior under reaction conditions; that is, it has a higher area and this area is reduced and reoxidized more easily. X-ray photoelectron spectroscopy analysis evidences that this is mainly attributed to praseodymium cations, which accomplish redox cycles more easily than cerium cations.

Impact of Extended Contact Cofiring on Multicrystalline Silicon Solar Cell Parameters

During the temperature spike of the contact cofiring step in a solar cell process, it has been shown that the concentration of lifetime-killer dissolved metallic impurities increases, while adding an annealing after the spike getters most of the dissolved impurities toward the phosphorus emitter, where they are less detrimental. The contact cofiring temperature profile, including the after-spike annealing, has been called extended contact cofiring, and it has also been proposed as a means to decrease the emitter saturation current density of highly doped emitters, thus benefiting a wide range of materials in terms of detrimental impurity content. The aim of the present work is to determine the effect of performing this additional annealing on contact quality and solar cell performance, looking for an optimal temperature profile for reduction of bulk and emitter recombination without affecting contact quality. It presents the effect of the extended cofiring step on fill factor, series resistance, and contact resistance of solar cells manufactured with different extended cofiring temperature profiles. Fill factor decreases when extended cofiring is performed. Series resistance and contact resistance increase during annealing, and this happens more dramatically when the temperature peak is decreased. Scanning electron microscopic images show silver crystallites in contact with silver bulk before the annealing that allow a direct current path, and silver crystallites totally surrounded by glass layer ( $>$ 100 nm thick) after annealing. Glass layer redistribution and thickening at low temperatures at the semiconductor–metal interface can be related to the series resistance increase. Degradation of series resistance during the temperature spike, when it is below the optimum one, can also be attributed to an incomplete silicon nitride etching and silver crystallite formation. To make full use of the beneficial effects of annealing, screen-printing metallic paste development supporting lower temperatures without a thick glass layer growth is needed.

A 14.7% Organic/Silicon Nanoholes Hybrid Solar Cell via Interfacial Engineering by Solution-Processed Inorganic Conformal Layer.

We demonstrated a high-performance Si-organic hybrid heterojunction solar cell utilizing low-temperature and liquid-phase-processed TiO2 as an interlayer between poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and Si nanoholes to produce a conformal contact on the surface of the Si nanostructure. The hydrophilic TiO2/Si-nanohole surface enabled the PEDOT:PSS to flow into the spacing of the close-packed nanoholes. Scanning electron microscopy images were used to confirm the PEDOT:PSS nanohole filling induced by the TiO2. With forming gas annealing of the double-sided TiO2, high Voc (0.63 V) and Jsc (35.7 mA/cm2) values were obtained, yielding a high power conversion efficiency of 14.7%. The high Voc was attributed to the surface passivation of Si by annealed TiO2. The X-ray photoelectron spectroscopy investigation at the TiO2/Si interface indicates the TiOx signal decreased and the TiO2 and SiOx signals increased after annealing. The Si-O bonding found in the O 1s study appeared in the form of Si-O-Si bonding to serve surface passivation. The band alignment of the PEDOT:PSS/TiO2/n-Si hetero-interfaces was postulated and plotted. The Vbi in the system after annealing was assumed to be higher because of the reduction of bulk and surface states that yield high Voc. After annealing, the Vbi increased from 0.805 to 0.905 V. The reduction of surface recombination velocity proved the passivation ability of TiO2 after annealing. With proven surface passivation and conformal PEDOT:PSS/Si nanohole interfaces for enhanced contact, this Si-organic hybrid heterojunction solar cell with solution-processed TiO2 interlayers has excellent potential for application as a high-efficiency and low-cost Si solar cell.

A hybrid material consisting of bulk-reduced TiO2, graphene oxide and polyaniline for resistance based sensing of gaseous ammonia at room temperature

A hybrid material consisting of bulk-reduced TiO2, graphene oxide (GO) and polyaniline (PANI) was fabricated by decorating TiO2 with GO, followed by in-situ oxidative chemical polymerization of aniline. The TiO2 nanoparticles (NPs) with thermally stable bulk reduction states were initially prepared from porous amorphous titanium as the precursor. The TiO2 NPs and GO were chemically conjugated to each other via amide bonds to improve the stability of the composite. The sensor, if operated in the conductivity mode, exhibits strong signal changes, and fast response and recovery times (of 32 and 17 s, respectively) to gaseous ammonia even at room temperature. Its response range extends from 5 to 300 ppm, and the lower detection limit is 5 ppm. The sensor is fairly selective and not interfered by gases such as CO, CH4, and trimethylamine, and by vapors of methanol and ethanol. It also displays good temporal stability. This is attributed to the bulk-reduced state of TiO2, the presence of oxygen functional groups on GO, and the strong adsorption and rapid diffusion of ammonia. The results also imply the presence of a synergetic effect between TiO2 and GO/PANI, which is probably beneficial for the potential application of the resulting composite as a gas sensor.

Influence of Both Cooling Rate and TeO2 Addition on the Properties of YBCO Superconductor

Composite of superconducting system YBCO-TeO2 was synthesized utilizing solid-state reaction technique. Different weight percentages of TeO2 were mixed with a basic mixture [YBCO] for the synthesis of [YBa2Cu3O7−y]1−x(TeO2)x composites. These mixtures were sintered at 1213 K (940 °C) for 24 hours and the samples cooled down by two different ways. The first way carried out via slowly cooling in furnace with the rate of 274 K/min to 275 K/min (1 °C/min to 2 °C/min) and the second one is quenching in oxygen gas. The XRD analysis showed that YBCO orthorhombic phase is the major phase appeared in all samples with different TeO2 content regardless of the cooling way. Additionally, minor unknown secondary phases appeared and enlarged with increasing TeO2 addition. Although quenched samples showed a phase difference between the sample's outer surface (orthorhombic) and its interior (tetragonal), the slowly cooled one did not clearly show such distinction. Moreover, doping YBCO with TeO2 leads to increase in the sample bulk density and reduction in their degradation degree in the wet atmosphere.

Effect of Cobalt on Reduction Characteristics of Ceria under Ethanol Steam Reforming Conditions: AP-XPS and XANES Studies

The surface and bulk reduction characteristics of bare ceria and ceria with supported cobalt nanoparticles were investigated under ethanol steam reforming conditions using AP-XPS and XANES techniques. Ceria particles were prepared in two different particle sizes, one in nano and the other in micron size (termed CeO2-NP and CeO2-MP), with average particle sizes of 4 and 120 nm, respectively. It was found that particle size affects surface reducibility of ceria particles; smaller particle size leads to a higher extent of surface reduction. Supported cobalt nanoparticles have a significant effect on the surface reducibility of both CeO2-NP and CeO2-MP. Compared to bare ceria particles, the presence of fully oxidized cobalt nanoparticles on the surface of ceria support retards surface reducibility of ceria since reduction of the cobalt oxide phases (Co3O4 and CoO) takes precedence over that of ceria. The degree of reduction of the cobalt phase during ethanol steam reforming determines the effect of cobalt on ...

The use of compaction in the manufacture of tablets

В производстве таблеток используют метод прямого прессования, влажной и сухой грануляции. Сухое гранулирование может быть использовано, если материалы имеют достаточные когезионные свойства с образованием гранул. Научные публикации последних лет убедительно доказывают перспективность использования компактирования в фармацевтической промышленности. Цель работ ы – обобщить доступные данные, касающиеся использования компактирования в фармацевтической промышленности. Материалы и методы. На основе доступных литературных источников по использованию компактирования при производстве таблеток изучили и проанализировали научную литературу. Использовали методы обзорного и системного анализа. Результаты. Собрали и систематизировали материал относительно характеристики процесса компактирования, его преимуществ и условий применения, выделили параметры процесса, обобщили теории компактирования; приведены характеристика оборудования для уплотнения, продемонстрированы ключевые характеристики материала при использовании в фармацевтической промышленности. Компактирование является технологией сухого гранулирования, в которой порошок, содержащий активные ингредиенты и вспомогательные вещества, уплотняют между двумя противоположно вращающимися валками путём применения механического давления. По сравнению с исходным порошком гранулы после уплотнения характеризуются значительно лучшей текучестью и высокой плотностью за счёт уменьшения объёма. Процесс уплотнения на валках существенно влияет на распределение частиц по размерам, сыпучесть, однородность, прессованность, уплотнение активных фармацевтических ингредиентов и вспомогательных веществ, таким образом, может повлиять на растворение, время распада, устойчивость к раздавливанию, истираемость и другие параметры таблетки. Основными параметрами компактирования являются давление уплотнения и способ его применения, условия и скорость проведения процесса. Выводы. Применение компактирования обеспечивает уменьшение или увеличение размера частиц с образованием гранул, ведёт к улучшению характеристик текучести порошка, избеганию грануляционной индуцированной деградации влагой, большей стабильности продукта, предотвращению сегрегации, уменьшению насыпного объёма. Это свидетельствует о перспективности использования технологии компактирования при производстве таблеток, которые соответствуют фармацевтическим требованиям.

Hypopharyngeal cancer: United Kingdom National Multidisciplinary Guidelines.

This is the official guideline endorsed by the specialty associations involved in the care of head and neck cancer patients in the UK. With an age standardised incidence rate of 0.63 per 100 000 population, hypopharynx cancers account for a small proportion of the head and neck cancer workload in the UK, and thus suffer from the lack of high level evidence. This paper discusses the evidence base pertaining to the management of hypopharyngeal cancer and provides recommendations on management for this group of patients receiving cancer care. Recommendations • Cross-sectional imaging with computed tomography of the head, neck and chest is necessary for all patients; magnetic resonance imaging of the primary site is useful particularly in advanced disease; and computed tomography and positron emission tomography to look for distant disease. (R) • Careful evaluation of the upper and lower extents of the disease is necessary, which may require contrast swallow or computed tomography and positron emission tomography imaging. (R) • Formal rigid endoscopic assessment under general anaesthetic should be performed. (R) • Nutritional status should be proactively managed. (R) • Full and unbiased discussion of treatment options should take place to allow informed patient choice. (G) • Early stage disease can be treated equally effectively with surgery or radiotherapy. (R) • Endoscopic resection can be considered for early well localised lesions. (R) • Bulky advanced tumours require circumferential or non-circumferential resection with wide margins to account for submucosal spread. (R) • Offer primary surgical treatment in the setting of a compromised larynx or significant dysphagia. (R) • Midline lesions require bilateral neck dissections. (R) • Consider management of silent nodal areas usually not addressed for other primary sites. (G) • Reconstruction needs to be individualised to the patients' needs and based on the experience of the unit with different reconstructive techniques. (G) • Consider tumour bulk reduction with induction chemotherapy prior to definitive radiotherapy. (R) • Consider intensity modulated radiation therapy where possible to limit the consequences of wide field irradiation to a large volume. (R) • Use concomitant chemotherapy in patients who are fit enough and consider epidermal growth factor receptor blockers for those who are less fit. (R).

Synthesis, Structural and Optical Properties of Mn-Doped Ceria Nanoparticles: A Promising Catalytic Material

The structure, the morphology and the thermal, optical and the surface properties of nanocrystalline CeO2 doped with Mn have been studied by X-ray diffraction (XRD), field-emission transmission electron microscopy (FE-TEM), energy-dispersive X-ray analysis, thermogravimetric analysis, UV–Vis absorption spectroscopy and Fourier transform infrared spectroscopy. The XRD results confirmed the successful incorporation of Mn into the CeO2 lattice through the formation of nanoscale face-centered cubic solid solution. The FE-TEM observations supported the nanocrystalline nature of the solid solutions. The presence of structural defects and their role on the band gap have been discussed on the basis of absorption spectral studies. The structural differences correlate with results from temperature-programmed reaction (TPR) experiments with H2 consumption. The TPR measurements showed an enhanced bulk reduction at much lower temperatures, indicating increased oxygen mobility in the samples, which enable to enhanced oxygen diffusion at lower temperatures.

Solar Water Splitting: Enhancing Low‐Bias Performance of Hematite Photoanodes for Solar Water Splitting by Simultaneous Reduction of Bulk, Interface, and Surface Recombination Pathways (Adv. Energy Mater. 4/2016)

For solar water-splitting, hematite (α-Fe2O3) is considered as one of the most promising photo-anode materials with a theoretical solar-to-hydrogen efficiency of over ≈15%. However, the multiple electron/hole recombination pathways that occur in the bulk, interfaces, and surfaces largely limit its low-bias performance. In article number 1501840, Xiaolin Zheng and co-workers report a facile and rapid ‘Sol-flame’ approach to simultaneously reduce these recombinations for a hematite nanorods array photoanode, which leads to a greatly enhanced low-bias performance.

Management of Hyperleukocytosis.

Hyperleukocytosis has a high morbidity index. The involvement of the respiratory or central nervous system and the metabolic derangements accompanying tumor lysis are responsible for early mortality. Standard care for acute hyperleukocytosis must include cytoreduction, proper supportive care, and prevention of tumor lysis. Hydration, alkalization, allopurinol, or urate oxidase should be started immediately. In patients with low platelet count of less than 20,000/mm(3), platelet transfusions should be given to prevent cerebral hemorrhage, as platelets do not add substantially to blood viscosity. Packed red blood cells must be given with caution as they can significantly increase blood viscosity. If the patient is hemodynamically stable, packed red transfusions should be planned when the hemoglobin level is less than 7-8 g/dl, avoiding post-transfusional levels above 10 g/dl. Coagulation abnormalities should be corrected. Leukapheresis has been advocated to correct metabolic abnormalities and to decrease viscosity by reducing the peripheral white blood count. However, leukapheresis may fail to decrease the leukocyte count substantially or may achieve only a transient tumor bulk reduction. The procedure is generally well tolerated but can involve problems such as the need for anticoagulation or difficulty of access, and limited availability in many institutions.Specific antileukemic therapy must be initiated as soon as life-threatening complications have been corrected as it remains the first-line treatment of hyperleukocytosis.

Optimization of Holding Time on Microwave Irradiation of the Composite Iron-Chromium Reinforced with Alumina Particle

In this study, the effect of holding time on the microwave sintered 84Fe-11Cr-5Al2O3 metal matrix composite (MMC) was investigated. Sintering was carried out in a tubular microwave furnace HAMiLab-V3 under N2 atmosphere. The holding time was selected between 0 to 75 minutes with increment of 15 minutes respectively. A study of microstructure and physical properties was carried out on sintered samples. It was discovered that, when the samples sintered at 1400oC with 20oC/min heating rate, the hardness was significantly increased from 110Hv to 160 Hv for holding time ranging from 30 to 45oC/min. Further increment until 75 minutes of holding time, no significant changes were obtained and hardness values were at steady state. The enhancement of bulk density and reduction of porosity were observed commences at 30 minutes until 45 minutes holding time. However, the results showed that the optimum holding time was at 45 minutes where the micro hardness is at the highest point which is about 160Hv.

Decrease of the required dopant concentration for δ-Bi2O3crystal stabilization through thermal quenching during single-step flame spray pyrolysis

δ-Bi2O3 is one of the best oxygen ion conductors known. However, due to its limited thermal stability and complicated synthesis techniques, its applications are limited. Here, the synthesis of stable nano-sized δ-Bi2O3 using versatile and rapid flame spray pyrolysis (FSP) combined with in situ Ti and/or Mn doping for an enhanced thermal stability is reported for the first time. Exceptionally low Bi replacing cation concentrations (8 at% Ti) were sufficient to obtain phase-pure δ-Bi2O3 which was attributed to the extraordinarily high temperature gradient during FSP. The required cation amount for δ-phase stabilization was even further reduced by introducing mixtures of Mn and Ti (2.5 at% Mn + 2.5 at% Ti). Rietveld analysis revealed that the δ-Bi2O3 structure is best represented by the Fmm space group containing two closely neighbored 8c and 32f Wyckoff positions. Depending on the amount of Mn/Ti cations, about 25% of the possible oxygen positions remain vacant, suggesting high bulk oxygen mobility. The enhanced oxygen mobility was confirmed by temperature programmed reduction (H2-TPR) with bulk reduction for δ-Bi2O3 in contrast to exclusive surface reduction for β-Bi2O3.

Microstructural Evolution of a Cu and θ-Al2O3 Composite Formed By Reduction of Delafossite CuAlO2: A HAADF-STEM Study

In situ reduction of bulk, polycrystalline copper(I) aluminate (CuAlO2) results in the formation of an intimate two-phase mixture of metallic Cu and θ-alumina. The microstructure of a partially transformed region was studied at the atomistic scale using high-angle angular-dark-field scanning transmission electron microscopy (HAADF-STEM). The observations were consistent with a topotactic transformation mechanism whereby deintercalation of the Cu atoms occurs sequentially at the edges of the Cu+ atomic layers of the CuAlO2 delafossite structure. The Cu forms faceted nanoislands that exhibit an orientation relationship with the θ-alumina matrix. There is also concomitant outward diffusion of oxygen, and it is suggested that the θ-alumina is formed by the consolidation of the layers of Al–O octahedra of the delafossite structure, with some local rearrangement of the Al3+ ions. This model is supported by the observed continuity of the Al–O layers between the parent CuAlO2 and θ-alumina, together with the orie...

Enhancing Low‐Bias Performance of Hematite Photoanodes for Solar Water Splitting by Simultaneous Reduction of Bulk, Interface, and Surface Recombination Pathways

For a hematite (α‐Fe2O3) photoanode, multiple electron/hole recombination pathways occurring in the bulk, interfaces, and surfaces largely limit its low‐bias performance (low photocurrent density at low‐bias potential) for photoelectrochemical water splitting. Here, a facile and rapid three‐step approach is reported to simultaneously reduce these recombinations for hematite nanorods (NRs) array photoanode, leading to a greatly improved photocurrent density at low bias potential. First, flame‐doping enables high concentration of Ti doping without hampering the morphology and surface properties of the hematite NRs, which reduces both the bulk and surface recombinations effectively. Second, the addition of a dense‐layer between the hematite NRs and fluorine‐doped SnO2 substrate effectively reduces the interfacial recombination by suppressing the electron back‐injection into electrolyte. Finally, the sequential oxalic acid etching and FeOOH deposition improves both the interface quality between FeOOH electrocatalyst and hematite NRs and the surface catalytic activity. Significantly, the combination of flame‐doping, dense‐layer deposition, surface etching, and electrocatalyst deposition effectively reduces the multiple electron/hole recombination pathways in a hematite NRs photoanode, which decreases the photocurrent onset potential from 1.02 V RHE to 0.64 VRHE, a reduction of 380 mV.

Ocean acidification effect on prokaryotic metabolism tested in two diverse trophic regimes in the Mediterranean Sea

Notwithstanding the increasing amount of researches on the effect of ocean acidification (OA) on marine ecosystems, no consent has emerged on its consequences on many prokaryote-mediated processes. Two mesocosm experiments were performed in coastal Mediterranean areas with different trophic status: the summer oligotrophic Bay of Calvi (BC, Corsica, France) and the winter mesotrophic Bay of Villefranche (BV, France). During these experiments, nine enclosures (∼54 m3) were deployed: 3 unamended controls and 6 elevated CO2, following a gradient up to 1250 μatm. We present results involving free-living viral and prokaryotic standing stocks, bacterial carbon production, abundance of highly active cells (CTC+), and degradation processes (beta-glucosidase, chitinase, leucine-aminopeptidase, lipase and alkaline phosphatase activities).The experiments revealed clear differences in the response of the two prokaryotic communities to CO2 manipulation. Only abundances of heterotrophic prokaryotes, viruses and lipase activity were not affected by CO2 manipulation at both locations. On the contrary, the percent of CTC+ was positively correlated to CO2 only in BC, concomitantly to a bulk reduction of [3H]-leucine uptake. The other tested parameters showed a different response at the two sites suggesting that the trophic regime of the systems plays a fundamental role on the effect of OA on prokaryotes through indirect modifications of the available substrate.Modified degradation rates may affect considerably the export of organic matter to the seafloor and thus ecosystem functioning within the water column. Our results highlight the need to further analyse the consequences of OA in oligotrophic ecosystems with particular focus on dissolved organic matter.