Purpose:
Knowing the contribution of neutron to collateral effects in treatments is both a complex and a mandatory task. This work aims to present an operative procedure for neutron estimates in any ...facility using a neutron digital detector.
Methods:
The authors’ previous work established a linear relationship between the total second cancer risk due to neutrons (TRn) and the number of MU of the treatment. Given that the digital detector also presents linearity with MU, its response can be used to determine the TRn per unit MU, denoted as m, normally associated to a generic Linac model and radiotherapy facility. Thus, from the number of MU of each patient treatment, the associated risk can be estimated. The feasibility of the procedure was tested by applying it in eight facilities; patients were evaluated as well.
Results:
From the reading of the detector under selected irradiation conditions, m values were obtained for different machines, ranging from 0.25 × 10−4% per MU for an Elekta Axesse at 10 MV to 6.5 × 10−4% per MU for a Varian Clinac at 18 MV. Using these values, TRn of patients was estimated in each facility and compared to that from the individual evaluation. Differences were within the range of uncertainty of the authors’ methodology of equivalent dose and risk estimations.
Conclusions:
The procedure presented here allows an easy estimation of the second cancer risk due to neutrons for any patient, given the number of MU of the treatment. It will enable the consideration of this information when selecting the optimal treatment for a patient by its implementation in the treatment planning system.
Torres et al. (2010) published a series of radiocarbon, AAR, ESR and OSL dates from the site of El Sidrón, northern Spain, which is notable for the discovery of the partial remains of 12 ...Neanderthals. Whilst the non‐radiocarbon methods suggested an age beyond 32 600–46 300 years, direct radiocarbon dates on the human fossils were inconsistent, ranging between 10 000 and 50 000 bp. This study uses the ultrafiltration pre‐treatment protocol to obtain a date of 48 400 ± 3200 bp (OxA‐21 776) on a bone fragment and confirm the antiquity of the Neanderthal assemblage. Moreover, it demonstrates the comparability of the ultrafiltration and ninhydrin bone radiocarbon pre‐treatment protocols, and highlights the need for appropriate screening methods where valuable collections with poor biomolecular preservation are sampled for collagen extraction.
The purpose of this paper is to model numerically the dynamics of CO
2
and
222
Rn in cave atmospheres, particularly in the noteworthy Cave of Altamira (Spain). We aim to get a better understanding of ...the nature of these dynamics and their couplings with climatic controls, more specifically the soil water content, which role in the said dynamics poses some questions. For the first time, we apply the global modeling technique in the field of cave microclimate and atmospheric composition. The global modeling technique is a methodology based on the theory of nonlinear systems and designed to extract mathematical models directly from observational time series. We were able to extract four global models from our data. These models represent a step forward from the existent conceptual ones. They also show that CO
2
and
222
Rn dynamics can be approximated by low-dimensional, deterministic systems, which can be chaotic or, at least, close to chaos; this has decisive methodological consequences for future research. Moreover, the global modeling technique was used for the first time in a non-autonomous formulation; this enabled the possibility of studying the influence of the external forcing (soil water content) on the gas concentration in different scenarios.
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•Pressurized GRAS solvents were evaluated for extraction of H. sabdariffa polyphenols.•Higher temperatures combined with greater % ethanol drove to lower dielectric constant.•Lower ...dielectric constant enhance the quantities of phenolic compounds extracted.•Optimized conditions were set up at 200 °C and 100% of ethanol.
An environmental friendly extraction procedure has been tested to extract phenolic compounds from H. sabdariffa calyces using pressurized GRAS solvents. A central composite rotatable design (CCRD) was performed to evaluate the influence of the main operational conditions: temperature (40–200 °C) and solvent composition based on aqueous hidroalcoholic solutions (0–100% ethanol). Phenolic composition of experimental extracts analyzed by HPLC-ESI-QTOF-MS showed that higher temperatures and greater ethanol percentages drove to solvents with lower dielectric constants, which resulted in extracts with major quantities of phenolic compounds. An exception was the extraction of cyanidin-3-sambubioside that could only be quantified in extracts performed at the lowest temperature (40 °C) due to its thermal sensibility. In addition, a RSM was carried out with the aim to maximize the extraction of total phenolic content. To this end, the predicted optimal extraction conditions by RSM were 200 °C and 100% (v/v) of ethanol. Results showed that temperature and ethanol percentage had a significant influence on the extraction of total phenolic compounds (p value < 0.05). The mathematical model pointed out 200 °C of temperature and 100% of ethanol as the optimum conditions to perform the isolation of phenolic compounds by means of pressurized GRAS solvents.
CO2 exchange between terrestrial ecosystems and the atmosphere is key to understanding the feedbacks between climate change and the land surface. In regions with carbonaceous parent material, CO2 ...exchange patterns occur that cannot be explained by biological processes, such as disproportionate outgassing during the daytime or nighttime CO2 uptake during periods when all vegetation is senescent. Neither of these phenomena can be attributed to carbonate weathering reactions, since their CO2 exchange rates are too small. Soil ventilation induced by high atmospheric turbulence is found to explain atypical CO2 exchange between carbonaceous systems and the atmosphere. However, by strongly altering subsurface CO2 concentrations, ventilation can be expected to influence carbonate weathering rates. By imposing ventilation-driven CO2 outgassing in a carbonate weathering model, we show here that carbonate geochemistry is accelerated and does play a surprisingly large role in the observed CO2 exchange pattern of a semi-arid ecosystem. We found that by rapidly depleting soil CO2 during the daytime, ventilation disturbs soil carbonate equilibria and therefore strongly magnifies daytime carbonate precipitation and associated CO2 production. At night, ventilation ceases and the depleted CO2 concentrations increase steadily. Dissolution of carbonate is now enhanced, which consumes CO2 and largely compensates for the enhanced daytime carbonate precipitation. This is why only a relatively small effect on global carbonate weathering rates is to be expected. On the short term, however, ventilation has a drastic effect on synoptic carbonate weathering rates, resulting in a pronounced diel pattern that exacerbates the non-biological behavior of soil–atmosphere CO2 exchanges in dry regions \\mbox{with carbonate soils}.
The objective of this study was to evaluate the effects of nitrogen and carbon source on cellulase activity of
Aspergillus niger
ITV 02. The results obtained showed that nitrogen had an influence on ...the increase in cellulase activity by
A. niger
ITV 02 during submerged fermentation. Optimal concentrations obtained from nitrogen sources, using a Box–Behnken design were 0.9 g/L urea, 2.4 g/L ammonium sulfate and 1.5 g/L yeast extract, obtaining endoglucanase and β-glucosidase specific activities of 24.63 U/mg and 72.66 U/mg, respectively, at 50 h of fermentation. Subsequently, the effect of three carbon sources was evaluated: carboxymethylcellulose, delignified sweet sorghum bagasse (DSSB) and sweet sorghum bagasse cellulose (SSBC). Maximum cellulase specific activity was obtained when using DSSB, increasing endoglucanase activity fivefold and β-glucosidase activity 1.25-fold (126.72 and 85 U/mg) respectively. SSBC hydrolysis using enzymatic extract produced 18 g/L reducing sugars, equivalent to a 25% residue conversion. These results showed that it is possible to obtain an extract with cellulase activity from
A. niger
ITV 02 to be used in SSBC hydrolysis using low-cost substrates such as DSSB, which would contribute to a reduction in second-generation ethanol process production costs and an increase in the availability of enzymes for this use.
Sugarcane bagasse is an agro-industrial waste produced from the sugar industry, which is composed of cellulose, hemicellulose, and lignin. It can be used as a raw material to get xylose, which is ...used to obtain various products of industrial interest, such as bioethanol and xylitol, among others. The objective of this work was to optimize the acid hydrolysis stage of sugarcane bagasse to obtain the maximum of xylose and the minimum of acetic acid concentration. The response surface methodology and the desirability criterion were used, evaluating the concentration of sulfuric acid (H
2
SO
4
: 1, 2, 3% v/v), the solid-liquid ratio (LSR: 6, 9, 12 ml/g), and reaction time (t: 10, 20, 30 min), as dependent variables and as response variables the maximum of xylose and the minimum of acetic acid concentration. The optimal conditions found by acid hydrolysis were 0.86% v/v of H
2
SO
4
, 22.7 min of reaction time, and 6.2 of LSR showing values of 20.0 g/L of xylose and 3.05 g/L of acetic acid. These conditions were experimentally validated, obtaining 20.37 ± 0.12 g/L, while the acetic acid concentration was 2.82 ± 0.05 g/L. These results showed that the optimization method used is good, since it was possible to accurately validate the conditions obtained, achieving similar results to those found by the optimization model, and also 75% of removal of hemicellulose was revealed.
Graphical abstract
This study is based on field monitoring of a cave-soil-atmosphere system validated with laboratory experiments. CO2 and 222Rn dynamics in the cavity are dependent on climatic parameters, mainly on ...the differences between the outdoor and indoor temperature. The annual cycles in the cave are characterized by two outstanding phenomena: cave gas recharge and ventilation when the cave acts as a gas sink or source. A permanent relationship with soil above the cave exists. The soil temperature and moisture are responsible for CO2 production on various time scales. Soil CO2 at the Rull site reaches values higher than 3000ppm in April–May, but falls to nearly 1000ppm during the summer. Maximum CO2 values in the cave are reached in the warmest months and are in accordance with soil CO2 values. The maximum CO2 concentration in the cave is 3470ppm on average, while the minimum is 623ppm. To describe the field findings, CO2 production and diffusion experiments related to the soil behaviour were developed. The results show that the soil CO2 production increases as the soil temperature and moisture increase according to a calculated logarithmic equation until the soil water content exceeds the saturation value. The soil-produced CO2 reaches the Rull cave by diffusion, which in Rull soil is reduced to approximately 60% when the soil water content increased from 0 to 30%. We estimated that 57kg of CO2 was emitted from the cave to the atmosphere in an annual cycle, considering a cave volume of 9915m3. Finally, projections of the future climate at the study site confirm a general tendency for annual-mean conditions to be warmer and drier, which will directly affect the soil CO2 production. In this situation, the Rull cave will experience changes in the stored and subsequently exchanged annual amount of CO2.
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•The outdoor atmosphere, the soil/rock membrane and the underground atmosphere are closely related•Climatic parameters regulate whether the subterranean environment acts as a CO2 sink or source•CO2 diffusion recharges the cave and decreases as the soil water content increases•The soil CO2 concentration is parameterized as function of the soil moisture and temperature•Future predictions about climate change may consider caves as natural CO2 sources
This study tests the hypothesis that the degree of moisture in the soil pore system determines gas exchange processes (ventilation/charge) between the outer atmosphere and the karst-epikarst during ...the warm, dry period (summer). These processes explain “anomalous” CO2 fluxes measured over this and other ecosystems. Emission of CO2 by ventilation of cavities requires an open double membrane system (host rock and soil) through which air movement can take place (H2Ovapour, CO2, 222Rn, etc.). An experimental study on the behavior of the soil and host rock porous system under changing air humidity conditions, coupled with a broad analytical approach addressing CO2 fluxes using the eddy-covariance technique and monitoring of the cave microclimate serves to define the suitable environmental conditions favoring air transfer between the cave atmosphere and exterior. This study shows the correlation between evapotranspiration, CO2 emissions, and cave ventilation processes due to the daytime opening of the soil membrane. Thus, the role of the soil as a membrane/interface or transfer medium can be observed, and it is directly dependent on weather conditions (temperature, humidity, wind).
► Daily episodes of ventilation in caves represent net CO2 emissions to the exterior. ► Emission of CO2 of caves requires an open double membrane system (host rock–soil). ► The soil acts as a barrier limiting gas exchange depending on weather conditions. ► The soil porous system determines the daily cyclic operation of the membrane.
Bacteria are able to induce carbonate precipitation although the participation of microbial or chemical processes in speleothem formation remains a matter of debate. In this study, the origin of ...carbonate depositions such as moonmilk, an unconsolidated microcrystalline formation with high water content, and the consolidation of carbonate precipitates into hard speleothems were analyzed. The utilized methods included measurements of the composition of stable isotopes in these precipitates, fluorimetric determinations of RNA/DNA ratios and respirometric estimations in Altamira Cave. Results from isotope composition showed increases of the δ
18O and δ
13C ratios from moonmilk in the very first stages of formation toward large speleothems. Estimates of RNA/DNA ratios suggested an inactivation of microorganisms from incipient moonmilk toward consolidated deposits of calcium carbonate. Respiratory activity of microorganisms also showed a significant decrease in samples with accumulated calcite. These results suggest that bacterial activity induces the conditions required for calcium carbonate precipitation, initiating the first stages of deposition. Progressive accumulation of carbonate leads towards a less favorable environment for the development of bacteria. On consolidated speleothems, the importance of bacteria in carbonate deposition decreases and chemical processes gain importance in the deposition of carbonates.
►Formation of carbonate deposits in caves was analyzed through different techniques. ►Microbial activity induces carbonate precipitation at the early stages of deposition. ►A progressive microbial inactivation was observed during carbonate deposition. ►Microorganisms play a minimum role on the growth of consolidated speleothems.
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