Dynamic investigations of a domestic scale thermally driven heat pump application

The subject is to employ an adsorption chiller to heat and cool two identical single family buildings. Its target is the creation of a dynamic model of a solar hot water system (SHWS) which includes a 3D model of the buildings, a dynamical model of the adsorption chiller and an automatic control system. The method consists in the creation of a dynamic model which simulates the components of the SHWS to predict the behavior of the SHWS during the entire year.ope

Development of polymeric drug delivery systems for biotech products

Since the early 80’s the forward steps in genetics and proteomics, have led a particular interest to biotech products, such as DNA and proteins. Although difficult, their large-scale production enabled the therapeutic use of this compounds. Proteins and DNA sequences can be very interesting therapeutic molecules owing to their high selectivity/affinity for the receptor or the specific site of action. Unfortunately, some issues still limit their pharmaceutical use, such as the susceptibility to enzymatic degradation, rapid renal clearance and immunogenicity. To overcome these limitations, many researchers are seeking solutions in the field of drug delivery systems (DDSs). In this respect, many systems have been developed and conjugation with PEG (polyethylene glycol) can be considered one of the leading approaches. PEGylation brings to the conjugated molecule great solubility and stability to proteolytic digestion, furthermore it reduces the tendency to aggregate and reduces the immunogenicity. Thanks to these advantages and the particular characteristics of PEG, to date, there are on the market 12 pegylated compounds: 9 are proteins, one peptide, one aptamer and a liposomal formulation, containing doxorubicin. The improvements in the pharmacokinetic profile of these drugs, thanks to the use of drug delivery systems, can be also applied in the field of tissue engineering, where the same issues are of fundamental importance for the development of scaffolds for cells capable of releasing growth factors. In the last years various polymers have been studied by many research groups to find an alternative to PEG, but its excellent biocompatibility and the know-how in its use has not brought any polymer to be truly competitive against PEG. Nevertheless, PEG presents some limits such as its non-biodegradability and in some case there are reports of antibodies against PEG. Therefore, there is an increased need for a PEG substitute. In the first section of this work hyaluronic acid (HA) has been studied as a candidate polymer for bioconjugation of proteins (HAylation). HA, being biodegradable can compensate this limit of PEG. HA, is also present in humans and is metabolized by hyaluronidase. Moreover, HA has the advantage of a high loading compared to PEG, thanks to the presence of repetitive functional groups in each monomer. This part of the work was focused on the study of HA conjugation (HAylation) to two model enzymes, trypsin and Ribonuclease A, and then to an interesting protein in pharmaceutical field, insulin. In order to avoid cross-linking phenomena, only a fraction of all carboxyl groups of the polymer has been modified to aldehyde allowing the conjugation with the amino groups of the protein models. Furthermore, by modulating the pH of reaction two protein-HA conjugates were obtained, selective N-terminal (pH 6) or random (pH 8), this taking advantage of the different pKa values of the amino groups in the proteins. The first products obtained with the enzymes Ribonuclease A and trypsin were tested verifying the residual activity compared to the native proteins. All conjugates, in particular those obtained by N-terminal selective conjugation, maintain a good activity on small substrates (30% decrease); only the HA-derived trypsin retains about 60% of residual activity against the substrate with a high weight molecular. Furthermore, enhanced stability over time was found for HA-trypsin respect to the free enzyme (45% on average) and also susceptibility to hyaluronidase was confirmed for both conjugates. Polymer validation as potential protein carrier was then evaluated by preparing conjugates with bovine insulin, as an example of pharmacologically active protein. Two conjugates were synthesized by N-terminal selective conjugation starting from polymers with different degree of aldehyde derivatization, 4% and 21%, yielding products with a protein loading of 17% and 32% (w/w), respectively. The therapeutic efficacy of the conjugates in comparison with insulin was tested in Sprague Dawley rats with induced diabetes. The conjugate with a lower protein loading was more effective and with a longer pharmacodynamic effect on the reduction on blood glucose level. The second section of the work was focused on an innovative strategy of enzymatic PEGylation of oligonucleotides. Briefly, the method investigated on model oligonucleotides is composed of two steps: the first consists in the chemical conjugation of a short oligonucleotide to a PEG chain, the second step is the enzymatic-mediated conjuagation of the PEGylated oligonucleotide with a DNA sequence by the DNA T4 ligase. To study the enzymatic PEGylation, 4 oligo sequences have been prepared as ligation model: two complementary pairs ending with sticky-ends in turn complementary (18-mer + 21-mer and 16-mer + 19-mer). The 18-mer has a thiol group in 5’-ending, in order to perform the coupling with PEG. Applying some modifications to ligation classical protocols, excellent results were obtained: PEGylated portion completely ligate the other ds-DNA and no undesired products were found. To further confirm the effective ligation, the ligated and PEGylated sequence was restricted with EcoRI. Indeed, the EcoRI recognized a sequence that is present only the ligated DNA. Complete restriction was found in absence and even in the presence of the polymer, further confirming the successes of ligation. Furthermore it was investigated if a reduced number of bases coupled to PEG can still preserve the requirements for the ligase enzyme activity. Thus, the pair of the complementary sequences then coupled to PEG has been reduced to half (9-mer + 12-mer). Even with a shorter PEGylated sequence a complete ligation was obtained. In conclusion in this thesis it has been demonstrated that HA can be a valid alternative to PEG for protein conjugation. In the field of oligonucleotide delivery an enzymatic approach of oligonucleotide conjugation can open new horizons that so far have not been completely explored

Dynamic simulation of a novel liquid desiccant air-conditioning system for greenhouse cooling and water recovery

We present dynamic, hour-by-hour modelling of a multi-stage nanofiltration regeneration system for liquid desiccant air-conditioning (NF-LDAC) of horticultural greenhouses in 17 locations covering four climate types. Four technologies are compared: fan ventilation, evaporative cooling (EvapC), conventional air-conditioning (AC), and NF-LDAC. The comparison is based on acceptable conditions for cultivation and coefficient of performance (COP). On average, fan ventilation and EvapC achieve acceptable conditions for 2 months per year, compared to 5.4 and 10.5 months for AC and NF-LDAC respectively. The highest COP value of 7.6 for NF-LDAC is reached at Colombo (Sri Lanka), followed by 5.3 at Mecca (Saudi Arabia). The permeate of the multi-stage regenerator can be recycled for irrigation, providing water savings. The highest water saving of 63% is at Mecca. These results are inferior but more realistic than those from an earlier idealised and steady-state model, which predicted a COP of 12.4 and water savings of 100% at Mecca. Nevertheless, in hot desert climates, NF-LDAC maintains acceptable conditions for year-round cultivation and saves water that is scarce in such climates. Future advances in nanofiltration membrane fabrication could increase the COP of NF-LDAC to 12.1 at Colombo and 7.4 at Mecca

Experimental determination of molar polarizability of nitrogen by a multi-reflection inteferometric technique

A novel optical pressure standard, based on a multi-reflection interferometric technique, has been recently developed. It is based on the measurement of the refractive index of a gas through an unbalanced homodyne interferometer (UINT) and is able to measure pressure with a relative standard uncertainty of 10 ppm at 100 kPa [1]. In this work, the interferometer was used to measure the molar polarizability of nitrogen, which resulted in agreement with recent previous determinations, paving the way for using photonic pressure standards as accurate and fast transfer standards of the pascal

Arte, afeto fundamental e transcendência teológica em Heidegger

O objetivo do artigo é explorar a reflexão heideggeriana sobre a arte nos Beiträge zur Philosophie, escrito que oferece uma perspectiva inaudita sobre o pensamento do filósofo no período posterior ao da Ontologia Fundamental, notadamente no que diz respeito à arte e à técnica.The aim of the article is to explore Heidegger’s reflections on art and technique in the period that follows the Beiträge zur Philosophie, so as to show how the philosopher arrives at his Philosophy of Art

A multi-stage membrane system for cooling and water recovery in horticultural greenhouses

The increasing issues of water scarcity and food insecurity highlight the necessity to utilise water and produce food more efficiently. Agriculture, which accounts for 70% of global water usage, is related to both these issues. Controlled-environmental greenhouses have been investigated as a potential solution, with liquid desiccant air-conditioning showing promising results. However, controlled-environmental greenhouses face challenges in hot climates. This is because conventional liquid desiccant air-conditioning utilises thermal energy-intensive liquid desiccant regenerators, highlighting the need for an alternative regenerator with lower energy requirements. Thus, a comparison of six membrane-based desalination technologies was conducted, and multi-stage nanofiltration was identified as the most promising for use as a liquid desiccant regenerator (Chapters 1 and 2). After conducting a steady-state investigation on multi-stage nanofiltration regeneration combined with liquid desiccant air-conditioning for greenhouse applications, it was found that the proposed system could achieve better indoor conditions for crops compared to thermal regenerators and conventional cooling technologies (Chapter 3). Consequently, the practical feasibility of nanofiltration regeneration was demonstrated through dead-end filtration experiments using a 1-stage regenerator (Chapter 4) and cross-flow filtration experiments using a 2-stage regenerator (Chapter 5). Additionally, a 2-stage regenerator model was developed and verified with errors below 11% compared to the experimental data (Chapter 5). The verified model was then applied to a dynamic simulation of a greenhouse using the proposed system (Chapter 6). The proposed system enables year-round cultivation and saves 50% of water in desert and semi-arid climates where crop production is challenging, and 30% in tropical climates where agriculture typically overuses water. By reducing water demand and enabling year-round cultivation, the proposed system addresses the issues of water scarcity and food insecurity in hot climates

Review - Arte e técnica em Heidegger, de Irene Borges-Duarte (Lisboa: Documenta, 2014)

Resenha de Arte e técnica em Heidegger, de Irene Borges-Duarte (Lisboa: Documenta, 2014