Microwave Microlitre Lab-on-Substrate Liquid Characterisation based on SIW Slot Antenna

A microwave microlitre binary liquid mixture concentration detection sensor with potential biological analysis is presented. The microwave lab-on-substrate sensor is fabricated using a substrate integrated waveguide (SIW) slot antenna. The microfluidic channel encapsulating liquid under investigation is located on top of the antenna slot at a quarter wavelength from the short-circuited end of the SIW. The radiated electric nearfield interaction with the liquid mixture exhibits different relationships between the complex permittivity of the liquid mixtures versus the resonant frequency and return loss, discriminating types and percentages of mixed liquid. The sensor was initially demonstrated with three types of samples: deionised water, methanol and air. A resonant frequency shift of 110MHz was measured to discriminate between air and deionised water while we obtained a 20MHz resonant frequency shift between air and methanol. Furthermore, the sensor was used to assess deionised water-methanol mixtures with methanol fractional volumes of 0 to 1 in 0.2 steps. The microwave-microfluidic sensor is contactless, uses readily available materials, cost effective and offers fast and accurate liquid characterisation

A Microfluidic-Integrated SIW Lab-on-Substrate Sensor for Microliter Liquid Characterization

A novel microfluidic-integrated microwave sensor with potential application in microliter-volume biological/biomedical liquid sample characterization and quantification is presented in this paper. The sensor is designed based on the resonance method, providing the best sensing accuracy, and implemented by using a substrate-integrated-waveguide (SIW) structure combining with a rectangular slot antenna operating at 10 GHz. The device can perform accurate characterization of various liquid materials from very low to high loss, demonstrated by measurement of deionized (DI) water and methanol liquid mixtures. The measured relative permittivity, which is the real part of complex permittivity, ranges from 8.58 to 66.12, which is simply limited by the choice of test materials available in our laboratory, not any other technical considerations of the sensor. The fabricated sensor prototype requires a very small liquid volume of less than 7 µl, while still offering an overall accuracy of better than 3 %, as compared to the commercial and other published works. Key advantages of the proposed sensor are that it combines 1.) a very low-profile planar and miniaturized structure sensing microliter liquid volume; 2.) ease of design and fabrication, which makes it cost-effective to manufacture and 3.) noninvasive and contactless measurements. Moreover, since the microfluidic subsystem can potentially be detached from the SIW microwave sensor and, afterward, replaced by a new microfluidic component, the sensor can be reused with no life-cycle limitation and without degrading any figure of merit

Development of Novel Microwave and Millimetre-wave Sensors for Liquid Characterisation

This research investigates the characterisation of liquids using primarily substrate integrated waveguides and extending this to other interesting conventional transmission lines. Focus is drawn to liquid mixture quantification, which is significant in the distinction of the quantity of one biological or chemical liquid from another. This work identified and confirmed that microwave resonance methods are best suited to perform mixture quantification due to their high sensing accuracy and inherent single point detection. The tracking of the resonant frequency change with either the corresponding return loss or insertion loss (depending on the type of resonant structure) gives a good solution in this regard. On the other hand, it was affirmed that transmission line methods are best suited for general broadband characterisation of a particular liquid. Three major outputs were achieved in this research work, namely: (i) In-SIW millimetre wave sensor; (ii) SIW slot antenna microlitre sensor and (iii) Sub-terahertz CSRR sensor for solid dielectric characterisation. Using the SIW slot antenna sensor, microlitre liquid volumes of 7 μl were characterised and binary mixtures quantified with an overall accuracy of better than 3 % when compared with results from a commercial sensor. The In-SIW millimetre wave sensor showed proof of concept through simulation results of the characterisation of 15 μl liquid volume results when compared to 100 ml liquid volume measurement done using the Keysight dielectric probe. The sub-terahertz CSRR sensor was used to characterise solid dielectrics using its multifuctionality capability of performing both resonant measurements and transmission line measurements

Mtindo katika Riwaya ya Marimba ya Majaliwa ya Edwin Semzaba

Lengo kuu la utafiti huu lilikuwa ni kuchambua matumizi ya mtindo katika riwaya ya Marimba ya Majaliwa. Malengo mahususi yalikuwa mawili ambayo ni kuchambua matumizi ya mtindo yanayohusiana na lugha katika riwaya ya Marimba ya Majaliwa na kubainisha matumizi ya mtindo yanayohusiana na vipengele vinginevyo vya kimtindo katika riwaya ya Marimba ya Majaliwa. Data za utafiti zimekusanywa kwa kutumia mbinu za usomaji makini na upitiaji wa nyaraka. Data hizo zilizokusanywa zilichambuliwa kwa kutumia mkabala wa kimaelezo na nadharia ya Simiotiki. Kwa upande wa lengo mahususi la kwanza, matokeo ya utafiti yanabainisha kuwa matumizi ya kimtindo ya lugha ni pamoja na tamathali za usemi za tashibiha, chuku na takriri. Pia kuna matumizi ya methali na Kiswahili cha kimaeneo. Kwa upande wa lengo mahususi la pili, matokeo ya utafiti ni kuwa vipengele vingine vya kimtindo vilivyotumika katika riwaya teule ni matumizi ya nyimbo, hadithi ndani ya hadithi, mwingiliano matini, tanzu ndani ya tanzu ndani ya tanzu na uhalisia mazingaombwe

Polyphenol- and fibre-rich dried fruits with green tea attenuate starch-derived postprandial blood glucose and insulin: a randomised, controlled, single-blind, cross-over intervention

Polyphenol- and fibre-rich foods (PFRF) have the potential to affect postprandial glycaemic responses by reducing glucose absorption, and thus decreasing the glycaemic response of foods when consumed together. A randomised, single-blind, cross-over study was conducted on sixteen healthy volunteers to test whether PFRF could attenuate postprandial blood glucose in healthy volunteers when added to a source of carbohydrate (starch in bread). This is the first study to examine the effects of a meal comprised of components to inhibit each stage of the biochemical pathway, leading up to the appearance of glucose in the blood. The volunteers were fasted and attended four visits: two control visits (bread, water, balancing sugars) and two test visits (single and double dose of PFRF) where they consumed bread, water and PFRF. Blood samples were collected at 0 (fasted), 15, 30, 45, 60, 90, 120, 150 and 180 min after consumption. The PFRF components were tested for α-amylase and α-glucosidase inhibitory potential in vitro. Plasma glucose was lower after consumption of both doses compared with controls: lower dose, change in mean incremental areas under the glucose curves (IAUC)=− 27·4 (SD 7·5) %, P< 0·001; higher dose, IAUC =− 49·0 (SD 15·3) %, P<0·001; insulin IAUC was also attenuated by − 46·9 (SD 13·4) %, P<0·01. Consistent with this, the polyphenol components of the PFRF inhibited α-amylase (green tea, strawberry, blackberry and blackcurrant) and α-glucosidase (green tea) activities in vitro. The PFRF have a pronounced and significant lowering effect on postprandial blood glucose and insulin response in humans, due in part to inhibition of α-amylase and α-glucosidase, as well as glucose transport

Nano-Fluidic Millimeter-Wave Lab-on-a-Waveguide Sensor for Liquid-Mixture Characterization

This paper reports on a miniaturized lab-on-a-waveguide liquid-mixture sensor, achieving highly-accurate nanoliter liquid sample characterization, for biomedical applications. The nanofluidic-integrated millimeter-wave sensor design is based on near-field transmission-line technique implemented by a single loop slot antenna operating at 91 GHz, fabricated into the lid of a photolaser-based subtractive manufactured WR-10 rectangular waveguide. The nanofluidic subsystem, which is mounted on top of the antenna aperture, is fabricated by using multiple Polytetrafluoroethylene (PTFE) layers to encapsulate and isolate the liquid sample during the experiment, hence, offering various preferable features e.g. noninvasive and contactless measurements. Moreover, the sensor is reusable by replacing only the nanofluidic subsystem, resulting a cost-effective sensor. The novel sensor can measure a liquid volume of as low as 210 nanoliters, while still achieving a discrimination accuracy of better than 2% of ethanol in the ethanol/deionized-water liquid mixture with a standard deviation of lower than 0.008 from at least three repeated measurements, resulting in the highest accurate ethanol and DI-water discriminator reported to date. The nanofluidic-integrated millimeter-wave sensor also offers other advantages such as ease of design, low fabrication and material cost, and no life-cycle limitation of the millimeter-wave subsystem

Chlorogenic and phenolic acids are only very weak inhibitors of human salivary α-amylase and rat intestinal maltase activities

There is increasing evidence that consumption of polyphenol and phenolic-rich foods and beverages have the potential to reduce the risk of developing diabetes type 2, with coffee a dominant example according to epidemiological evidence. One of the proposed mechanisms of action is the inhibition of carbohydrate-digesting enzymes leading to attenuated post-prandial blood glucose concentrations, as exemplified by the anti-diabetic drug, acarbose. We determined if the phenolic, 5-caffeoylquinic acid, present in coffee, apples, potatoes, artichokes and prunes, for example, and also selected free phenolic acids (ferulic acid, caffeic acid and 3,4-dimethoxycinnamic acid), could inhibit human salivary α-amylase and rat intestinal maltase activities, digestive enzymes involved in the degradation of starch and malto-oligosaccharides. Using validated assays, we show that phenolic acids, both free and linked to quinic acid, are poor inhibitors of these enzymes, despite several publications that claim otherwise. 5-CQA inhibited human α-amylase only by <20% at 5 mM, with even less inhibition of rat intestinal maltase. The most effective inhibition was with 3,4-dimethoxycinnamic acid (plateau at maximum 32% inhibition of human α-amylase at 0.6 mM), but this compound is found in coffee in the free form only at very low concentrations. Espresso coffee contains the highest levels of 5-CQA among all commonly consumed foods and beverages with a typical concentration of ~5 mM, and much lower levels of free phenolic acids. We therefore conclude that inhibition of carbohydrate-digesting enzymes by chlorogenic or phenolic acids from any food or beverage is unlikely to be sufficient to modify post-prandial glycaemia, and so is unlikely to be the mechanism by which chlorogenic acid-rich foods and beverages such as coffee can reduce the risk of developing type 2 diabetes

Pomegranate juice, but not an extract, confers a lower glycemic response on a high–glycemic index food: randomized, crossover, controlled trials in healthy subjects

Background: Low–glycemic index diets have demonstrated health benefits associated with a reduced risk of developing type 2 diabetes. Objectives: We tested whether pomegranate polyphenols could lower the glycemic response of a high–glycemic index food when consumed together and the mechanism by which this might occur. Design: We compared the acute effect of a pomegranate juice and a polyphenol-rich extract from pomegranate (supplement) on the bread-derived postprandial blood glucose concentration in 2 randomized, crossover, controlled studies (double-blinded for the supplements), each on 16 healthy volunteers. An additional randomized, crossover, controlled study on 16 volunteers consuming constituent fruit acids in a pH-balanced solution (same pH as pomegranate) and bread was conducted to determine any contributions to postprandial responses caused by acidic beverages. Results: As primary outcome, the incremental area under the curve for bread-derived blood glucose (−33.1% ± 18.1%, P = 0.000005) and peak blood glucose (25.4% ± 19.3%, P = 0.0004) were attenuated by pomegranate juice, compared with a control solution containing the equivalent amount of sugars. In contrast, the pomegranate supplement, or a solution containing the malic and citric acid components of the juice, was ineffective. The pomegranate polyphenol punicalagin was a very effective inhibitor of human α-amylase in vitro, comparable to the drug acarbose. Neither the pomegranate extract nor the individual component polyphenols inhibited 14C-D-glucose transport across differentiated Caco-2/TC7 cell monolayers, but they inhibited uptake of 14C-glucose into Xenopus oocytes expressing the human glucose transporter type 2. Further, some of the predicted pomegranate gut microbiota metabolites modulated 14C-D-glucose and 14C-deoxy-D-glucose uptake into hepatic HepG2 cells. Conclusions: These data indicate that pomegranate polyphenols, when present in a beverage but not in a supplement, can reduce the postprandial glycemic response of bread, whereas microbial metabolites from pomegranate polyphenols exhibit the potential to further modulate sugar metabolism much later in the postprandial period. This trial was registered at clinicaltrials.gov as NCT02486978, NCT02624609, and NCT03242876

Nutritional implications of olives and sugar: attenuation of post-prandial glucose spikes in healthy volunteers by inhibition of sucrose hydrolysis and glucose transport by oleuropein

Purpose: The secoiridoid oleuropein, as found in olives and olive leaves, modulates some biomarkers of diabetes risk in vivo. A possible mechanism may be to attenuate sugar digestion and absorption. Methods: We explored the potential of oleuropein, prepared from olive leaves in a water soluble form (OLE), to inhibit digestive enzymes (α-amylase, maltase, sucrase), and lower [¹⁴C(U)]-glucose uptake in Xenopus oocytes expressing human GLUT2 and [¹⁴C(U)]-glucose transport across differentiated Caco-2 cell monolayers. We conducted 7 separate crossover, controlled, randomised intervention studies on healthy volunteers (double-blinded and placebo-controlled for the OLE supplement) to assess the effect of OLE on post-prandial blood glucose after consumption of bread, glucose or sucrose. Results: OLE inhibited intestinal maltase, human sucrase, glucose transport across Caco-2 monolayers, and uptake of glucose by GLUT2 in Xenopus oocytes, but was a weak inhibitor of human α-amylase. OLE, in capsules, in solution or as naturally present in olives, did not affect post-prandial glucose derived from bread, while OLE in solution attenuated post-prandial blood glucose after consumption of 25 g sucrose, but had no effect when consumed with 50 g of sucrose or glucose. Conclusion: The combined inhibition of sucrase activity and of glucose transport observed in vitro was sufficient to modify digestion of low doses of sucrose in healthy volunteers. In comparison, the weak inhibition of α-amylase by OLE was not enough to modify blood sugar when consumed with a starch-rich food, suggesting that a threshold potency is required for inhibition of digestive enzymes in order to translate into in vivo effects

Inhibition of Human and Rat Sucrase and Maltase Activities To Assess Antiglycemic Potential: Optimization of the Assay Using Acarbose and Polyphenols

We optimized the assays used to measure inhibition of rat and human α-glucosidases (sucrase and maltase activities), intestinal enzymes which catalyze the final steps of carbohydrate digestion. Cell-free extracts from fully differentiated intestinal Caco-2/TC7 monolayers were shown to be a suitable source of sucrase–isomaltase, with the same sequence as human small intestine, and were compared to a rat intestinal extract. The kinetic conditions of the assay were optimized, including comparison of enzymatic and chromatographic methods to detect the monosaccharide products. Human sucrase activity was more susceptible than the rat enzyme to inhibition by acarbose (IC₅₀ (concentration required for 50% inhibition) = 2.5 ± 0.5 and 12.3 ± 0.6 μM, respectively), by a polyphenol-rich green tea extract, and by pure (−)-epigallocatechin gallate (EGCG) (IC₅₀ = 657 ± 150 and 950 ± 86 μM respectively). In contrast, the reverse was observed when assessing maltase activity (e.g., EGCG: IC₅₀ = 677 ± 241 and 14.0 ± 2.0 μM for human and rat maltase, respectively). 5-Caffeoylquinic acid did not significantly inhibit maltase and was only a very weak inhibitor of sucrase. The data show that for sucrase and maltase activities, inhibition patterns of rat and human enzymes are generally qualitatively similar but can be quantitatively different