Balances de elementos en un agroecosistema de caña de azúcar: I. Balance de nitrógeno

In a tropical mollisol cropped with sugar cane the annual nitrogen balance was quantified taken into account the main i) inputs, ii) outputs and iii) transference of the element (N-NO3 + N-NH4) in the plant and soil subsystems. Precipitation input corresponded to 26.3 kg N.h–1.yr-1 mainly as N-NH4. After the rain water passes the sugar cane canopy there was a retention of N in the N-NH4 form, whereas N-NO3 was leached from the canopy. Outputs through leaching reached 5.3 kg N. ha-1.yr–1 mainly as N-NO3. An important part of total soil N is fixed to the 2:1 type clay particles (montmorillonitic), abundant in the studied mollisol. It is hypothesised that this fixed N could act as a soil N reserve. Net mineralization of the organic-N reached a high value (343 kg N.ha-1.yr–1) in accordance with the intense nitrification process occurring in the soil as a consequence of the convenient C/N ratio and urea fertilisation. Major N losses in the agrosystem correspond to cropping export and removal of ashes after fire. Yearly 98% of N accumulated in the aerial biomass is lost through those ways. In general the annual nitrogen budget is driven off through input by fertilisation and output through stem cropping and N volatilisation by fire

Pumped heat energy storage with liquid media: Thermodynamic assessment by a transcritical Rankine-like model

[EN]A pumped heat energy storage (PHES) system based on a Rankine cycle for supercritical working fluids, such as carbon dioxide and ammonia, accounting for the irreversible latent and sensible heat transfers between the working fluid and the storage liquid medium, as water or thermal oil, is analyzed. The model also includes several parameters such as pressure losses, heat exchanger efficiencies, and isentropic efficiencies of the compressor, pump, and expansion devices (such as turbines and valves), that take into account the main internal and external losses and heat leak to the environment. The model allows for the calculation of specific energy, the heat pump performance coefficient, heat engine efficiency, and overall round-trip efficiency, as well as the temperatures of the working fluid and reservoirs. A zero-dimensional model is also used to determine the time dependence of heat leak in the tanks. The main results show that this technology could achieve round trip efficiency values in the order of 50–70%. Irreversibilities in compression and expansion appears as the most influential energy losses factor. The time effect of the ambient conditions on the tanks has been analyzed for a wet subtropical climate but it seems that the ambient conditions have no major influence on the performance of the system. In addition, explicit numerical results and temperature–entropy plots are presented for two representative systems as carbon dioxide-water and ammonia-thermal oil to take into account the main values in an operating condition

Genetics: Is LADA just late onset type 1 diabetes?

Background: There is a controversy regarding Latent Autoimmune Diabetes in Adults (LADA) classification and whether it should be considered a slowly progressing form of type 1 (T1) diabetes (DM) or a distinct type of DM altogether. Methods: This cross-sectional study assessed major genes associated with T1DM (class II Results: A total of 578 participants were included: 248 with T1DM (70 diagnosed after the age of 30), 256 with T2DM and 74 with LADA. High risk HLA alleles were significantly more frequent in LADA than in T2DM, whereas the opposite was true for protective alleles. We found a lower frequency of the high-risk DRB1*04-DQB1*03:02-DQA1*03:01 haplotype in LADA (21.1%) than in the overall T1DM (34.7%) (p\u3c0.05), whereas no differences were found between these groups for DRB1*03-DQB1*02:01-DQA1*05:01 or for protective alleles. Only 12% the overall T1DM group had no risk alleles vs 30% of LADA (p\u3c0.0005). However, HLA allele distribution was similar in LADA and T1DM diagnosed after the age of 30. A total of 506 individuals (195 with T1DM [21 diagnosed after age 30] 253 with T2DM and 58 with LADA) were genotyped for the Conclusion: In this relatively small cross-sectional study, the genetic profile of subjects with LADA showed a similar T1DM-related risk allele distribution as in participants with T1DM diagnosed after the age of 30, but fewer risk alleles than those diagnosed before 30. Differences were present for HLA, as well a

Pumped heat energy storage with liquid media: Thermodynamic assessment by a Brayton-like model

[EN]A thermodynamic model for a steady state pumped heat energy storage in liquid media is presented: it comprises a coupled Brayton-like heat pump and heat engine cycles connected to a cryogenic liquid and a hot molten salt by counter-flow heat exchangers. The model considers non-isothermal heat transfers between the working fluid and the liquid media and explicitly includes a set of parameters accounting for the main internal and external losses, heat leak, and pinch point effects for both the heat pump (charge) and heat engine (discharge) modes. Specific expressions for the main magnitudes in the charge (as the input power and coefficient of performance) and discharge (as power output and efficiency) modes and the global round trip efficiency have been analytically derived in terms of isentropic efficiencies of the compressor and turbine, pressure losses in the heat exchange processes, effectivenesses of the external counter-flow heat exchangers, and coupling between the working fluid and the storage and cryogenic liquid media. Round trip efficiencies around of 35 − 40% have been obtained, internal losses being those with main negative influence on the calculated values. The strong constraints imposed by the pinch point effects and liquid media have been analyzed. The model provides a thermodynamic assessment of the main involved processes and their interplay for a selected arrangement (molten salts, cryogenic fluid, and the charge and discharge power blocks) in order to check parametric strategies for thermodynamic optimization and design. These strategies are based on a reduced set of parameters of the overall installation and without the high computational costs of dynamical models.(ANII); Fondo Sectorial de Energía, Uruguay; contract FSE-1-2018-1-153077

Multicriteria optimization of Brayton-like pumped thermal electricity storage with liquid media

[EN]A multi-objective and multi-parametric optimization of a Pumped Thermal Electricity Storage system based on Brayton cycles is presented by the calculation of different Pareto fronts and the associated Pareto optimal sets for energetic and design analysis, respectively. A large range of internal and external irreversibilities and the thermodynamic properties of the storage media are taken into account. The analysis shows that the heat capacity of the working fluid and the heat capacity of the storage media should be the same in the contact with the hot reservoirs and in the contact with the cold reservoir in the heat pump, but in the contact with the cold reservoir for the heat engine the ratio should be 0.33, this offers information regarding the mass flow increasing significantly the achievable values for the round-trip efficiency, power output and the heat engine efficiency in the discharge process. Optimal values are given in terms of the degree of irreversibilities in the system and a comparison is made with extreme cases of infinite and minimum sizes for the storage system. Round-trip efficiencies in the so-called optimum scale/mass-flow-ratio design point exhibits noticeably larger values compared to previously reported results including the so-called endoreversible limit, where no internal irreversibilities are considered and where the improvement can achieve 49% over the endoreversible case in the most ideal scenario. Explicit numerical values of the maximum round trip efficiency, power output, and efficiency are given for a broad range of both internal and external irreversibilities.Agencia Nacional de Investigación e Innovación (ANII): Fondo Sectorial de Energía (Uruguay), under contract FSE-1-2018-1-153077 Universidad de Salamanca, Spain, under contracts 18.KB.YF/463A.C.01 and 0218463AB01

Effects of a simulation-based workshop on nursing students' competence in arterial puncture

Objective: To evaluate whether a short simulation-based workshop in radial artery puncture would improve nursing students’ competence to a level in which they could practise the procedure on a live patient without compromising his safety. Methods: Quasi-experimental one-group pretest-posttest study with 111 third-year nursing students. A 1.5-hour simulation-based workshop was implemented. This included a video-lecture, live demonstrations, selfdirected simulated practice in dyads and individual intermittent feedback. Participants’ skills, knowledge and self-efficacy in arterial puncture were measured before and after attending the workshop. Results: After the intervention, a total of 61.1% of the participants showed the level of competence required to safely practice radial artery puncture on a live patient under supervision. Conclusion: Effective simulation-based training in arterial puncture for nursing students does not necessarily need to be resource-intensive. Well-planned, evidence-based training sessions using low-tech simulators could help educators to achieve good educational outcomes and promote patient safety