Non-degenerate-pump four-wave mixing kinetic inductance travelling-wave parametric amplifiers

Kinetic inductance travelling-wave parametric amplifiers (KITWPAs) have been demonstrated to achieve high gain over broad bandwidths whilst achieving near quantum-limited noise performance, properties which are extremely important for many ultra-sensitive experiments. In early KITWPA designs, the requirement for phase-matching lead to the creation of a large zero-gain gap in the centre of the gain profile where the peak gain is, which also slightly narrows down the operational bandwidth of the device. This has been mitigated in more recent designs by introducing a DC bias to the KITWPA device, which allows the gap to be tuned away from the amplification band. However, the added DC biasing requires a more complicated experimental setup and potentially leads to unwanted heat leak in the cryogenic environment. Additionally, operation with a DC bias also become challenging at higher frequencies beyond the microwave regime. In this paper, we present the concept of a KITWPA operating in a non-degenerate-pump four-wave mixing (NP-4WM) regime, whereby the injection of two pump tones along with a weak signal results in a broad, flat gain profile that removes the zero-gain gap as well as eliminates the need for a DC bias and the complexities associated with it. We demonstrate how a NP-4WM KITWPA is feasible to achieve broadband amplification at a range of frequencies, first in the microwave range where most KITWPAs reported to-date have been successfully experimentally characterised. We then extend the designs to several millimetre (mm) bands to illustrate how we can use this technique to design a broadband front-end pre-amplifier that covers several Atacama Large Millimetre/sub-millimetre Array (ALMA) Bands

Simulations of Flow in a Solar Roof Collector Driven by Natural Convection.

The solar roof collector is modelled as a two dimensional air gap with one heated wall. The Boussinesq approximation is used to model the density variation. Four different air gap heights were simulated, namely 0.07m, 0.014m, 0,21m and 0.28m for a 2m long solar roof collector. The tilt angle of the solar collector was also varied between 15° and 55�� from horizontal. Predictions of velocities and mass flow rates in the air-gap are presented together with streamlines showing air flow patterns. The simulations show that a 0.14m air gap height at higher inclination angles is optimal for ventilation

Le Théâtre

We present preliminary measured responses of a planar superconducting on/off switch operating at millimeter wavelengths. The superconducting switch, comprising three niobium nitride (NbN) bridges, is deposited across the slotline section of a back-to-back unilateral finline. The transmission characteristics of the superconducting switch illuminated by a millimeter source was measured using a superconductor-insulator-superconductor (SIS) tunnel junction as direct detector. The NbN bridges were switched from the superconducting state to the normal state by passing current through the bridges with magnitude that exceeds its critical current value. With this arrangement, we have measured a typical switching dynamic range of approximately 10 dB across the 205-240 GHz band, with the highest dynamic range of ?20 dB at 230 GHz. This demonstrated the successful operation of the multiple NbN bridges as a planar superconducting on/off switch

Investigating the effects of sum-frequency conversions and surface impedance uniformity in traveling wave superconducting parametric amplifiers

Traveling wave parametric amplifiers (TWPAs) offer the most promising solution for high gain, broadband, and quantum noise limited amplification at microwave frequencies. Experimental realization of TWPAs has proved challenging with often major discrepancies between the theoretically predicted and the measured gain performance of the devices. Here, we extend the conventional modeling techniques to account for spatial variation in the surface impedance of the thin film and the parametric sum-frequency conversions effect, which subsequently results in accurate reproduction of experimental device behavior. We further show that such an analysis may be critical to ensure fabricated TWPAs can operate as designed

Footprint of increased anthropogenic disturbance elevates termite pest status

Tese de doutoramento em Ciências Farmacêuticas, na especialidade de Farmacognosia e Fitoquímica, apresentada à Faculdade de Farmácia da Universidade de CoimbraCymbopogon citratus (DC). Stapf (Poaceae), commonly known as lemongrass, is a tropical perennial shrub originated from the Southeast Asia. This plant is reported to possess antifungal, insecticidal, anti-diabetic, anti-septic, anti-mutagenic, anti-carcinogenic activities as well as anti-inflammatory. In fact, aqueous extracts of dried leaves are used all over the year in folk medicine for the treatment of peptic ulcers and inflammatory conditions. Recently, some phenolic compounds, such as luteolin and apigenin glycosides and condensed tannins, were identified and related to both antioxidant and anti-inflammatory properties. The purposes of this work were to i) validate an analytical method for quantification of phenolic compounds of C. citratus; ii) study the influence of harvest time and plant quality on the phenolic composition and antioxidant activity; iii) characterize the tannins; iv) validate the traditional uses of lemongrass infusion as anti-inflammatory in vivo; v) obtain a topical formulation to evaluate the phenolic compounds permeation and their anti-inflammatory activity; vi) trace the pharmacokinetic profile of the main phenolic compounds in rats. Three different extracts: infusion (CcI), 50% aqueous ethanol (CcM50%) and ethanol (CcM100%) extracts were prepared and a simple and efficient RP-HPLC-PDA method was successfully validated for simultaneous identification and quantification of phenolic acids and flavonoids. Infusions were also obtained from different harvest dates (April, June, July, August and September) and quality grades (High, Medium and Low). It was verified that the content on polyphenols and the antioxidant capacity of CcI is strongly related with the quality of the plant. The total phenols assay showed a substantial loss from August to September. It was possible to find out the best month to harvest the plant to get the most of each phenolic group: April and June for hydroxycinnamic acids; June and September for flavonoids; June, July and August for tannins. Regardless the group of phenolic compound addressed, its content was always inversely proportional to the degree of leaves ageing. For all tested oxidant species, the high-quality samples exhibited the best antioxidant results. CcI was fractionated by column chromatography and polyphenol-rich fractions, namely phenolic acids (CcPA), flavonoids (CcF) and tannins (CcT) were obtained. CcT was characterized by HPLC-PDA-ESI/MSn, revealing the presence of proanthocyanidin hetero-dimers, along with some common procyanidin dimers. These hetero-dimeric flavan structures have been described for the first time in lemongrass and consist of apigeniflavan or luteoliflavan units linked to a flavanone, either naringenin or eriodictyol, and may occur as aglycone or glycosylated forms. For the in vivo assays, CcI, CcF and CcT were tested. CcI administered before and after ethanol stimulus, significantly reduced the incidence and severity of gastric lesions and, consequently, the ulcer index, corroborating the traditional medicinal use of this plant to ameliorate gastritis and/or peptic ulcers symptoms. On the other hand, CcI, CcF and CcT were orally administered to rats, in order to evaluate the anti-inflammatory effect at the carrageenan-induced paw edema assay. The observed effect by CcI (68.24 mg/kg), 82.30% of edema inhibition, was very similar to that obtained by the reference NSAID used (diclofenac, 10 mg/kg), 84.00%. On the other hand, flavonoid (7.42 mg/kg) and the tannin-rich (5.96 mg/kg) fractions significantly contributed for the anti-inflammatory activity on the edema volume (59 and 61%, respectively). The topical anti-inflammatory activity of CcI was also addressed. The results suggest that flavonoids, mainly, luteolin 7-O-neohesperidoside, cassiaoccidentalin B, carlinoside and cynaroside, may contribute to the topical anti-inflammatory effect. CcF (0.6%), CcT (0.3%) and CcF+CcT (0.66%+0.34%) topical formulations were also tested, and the results obtained suggest that tannins and flavonoids also possess a significant activity and that a synergistic mechanism of action may occur. In fact, edema inhibitions of 43%, 47% and 59% were respectively verified, being CcF+CcT effect very close to that of 1% diclofenac (65.9%). Pharmacokinetic analysis was performed in plasma, liver and kidney and showed that the compounds present in CcI are not detected in vivo after a single-dose oral administration. In contrary, the metabolites, luteolin 7-O-glucuronide and luteolin 3’-O-sulfate, present at the highest bioavailability, are probably the main responsible for the anti-inflammatory activity previously reported. In conclusion, this work has developed a method to quantify the phenolic compounds contained in C. citratus; pointed the importance of harvesting and storing the plant material, in order to take the maximum advantages from the phenolic compounds use; and demonstrated, in safe doses, its anti-inflammatory activity, using an in vivo approach, which supports the traditional use of lemongrass infusion. Furthermore, C. citratus leaves flavonoids and tannins were highlighted as bioactive compounds, encouraging the development of new anti-inflammatory drugs or nutraceuticals

Thermochemical conversion of Napier Grass for production of renewable syngas

Fuel resource diversification is a global effort to deviate from non-renewable fossil fuels. Biomass has been identified as an alternative solid biofuel source due to its desirable properties and carbon neutrality. As reported in the literature, biomass can positively contribute towards combating climate change while providing alleviation for energy security issue. As part of efforts to diversify biomass resources, this work intends to explore the potential of Napier grass, one type of energy crop, for the production of renewable syngas via gasification. This energy crop is originally from Africa, which is highly productive with low cost (40 tonnes per year per hectare). Limited studies were conducted to analyze the potential of such an energy crop as a fuel source, which is the subject of this work. In order to analyze the full potential of such energy crop, the physical and chemical characteristics of this biomass was first analyzed. To determine the productivity of syngas from this biomass, fluidized bed gasifier was used in this work. The effects of gasification process parameters (i.e., equivalence ratio and temperature) on product yield and producer gas compositions were examined. Besides, the effects of equivalence ratio towards higher heating value of syngas and carbon conversion efficiency were analyzed. Based on the ultimate analysis results, the molecular formula of Napier gas was CH1.56O0.81N0.0043. Meanwhile, the higher heating value of such biomass was determined as 16.73 MJ/kg, which was comparable to other biomasses. It is noted that in this work, the volatile matter was determined as 85.52% and this promoted gasification process remarkably. The dynamics of the reactions involved were observed as a significant variation in product yield and biogas components were recorded at varying equivalence ratio and gasifier operating temperature

The Influence of LO Power Heating of the Tunnel Junction on the Performance of THz SIS Mixers

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Thermogravimetric study of napier grass in inert and oxidative atmospheres conditions

Since the industrialisation of Malaysia, the energy demand which mainly relied on fossil fuels has risen continuously. Therefore, all parties including the government, academic society and communities have explored alternative fuel resources to improve the reliability and security of energy supply to meet the future energy. In recent years, biomass has been identified as one of the most promising renewable energy resources compared to hydro, solar, wind, etc. It is projected that energy crops could potentially supply around 200-400 EJ/year in Malaysia at a competitive cost by 2050. Perennial grass is one type of energy crop that could address the above mentioned challenge. In this work, Napier grass (NG) is chosen as the subject due to its desirable characteristics (availability, high growth rates, carbon neutrality and high volatility). In order to investigate the feasibility of NG for heat and power application, the thermal decomposition characteristics, reactivity, and kinetic of NG needed were tested via thermogravimetric analysis (TGA) under inert (nitrogen) and air atmosphere conditions, respectively. The results indicated that NG biomass has great potential as sustainable energy fuel source for energy generation via gasification process

Outcome-Based Engineering Education: A Global Report of International OBE Accreditation and Assessment Practices

Outcome-based education (OBE) is a paradigm in which instructional and assessment/ evaluation are explicitly designed for ensuring the attainment and mastery of predefined learning outcomes. OBE is now the underlying paradigm followed by global accreditation efforts such as the Washington Accord (ratified in 1989). The shift to OBE is so pronounced that some education experts identify the shift to outcome-based education and accreditation as one of the top 5 major changes of the last 100 years. OBE is starkly different from the previous content-based educational approaches in shifting the aim from covering the content to a student-centric mastery that is driven by exit-outcomes and educational objectives. And while OBE is often criticized for straitjacketing education, and resisted by hesitant faculty members suspecting additional burden, studies show that the OBE movement, on the whole, has helped in improving the educational standards and outcomes by helping ensure proper planning of curriculum and assessment and their alignment with the program objectives and desired outcomes. OBE is also flexible in the sense that it does not dictate the choice of specific education strategies or teaching methods. New OBE schemes have also diversified in response to early misgiving about OBE (related to excessive paperwork, and bean-counting-like auditing) and now admit diverse types of evidence (including qualitative and quantitative, formative and summative, formal and informal assessments). In this paper, we present—as a geographically dispersed set of academics from Pakistan, United Kingdom, United States of America, Malaysia, Saudi Arabia—a global international perspective on OBE accreditation standards, practices, and attitudes. We will trace the historical development leading to the great shift to OBE in recent times and also synthesize insights from our diverse transnational experience in meeting accreditation requirements in different countries