Bee Products as Functional Food

The studies that reveal the impact of the bee products on overall health are accompanied by new researches every year, and the importance of these researches are gradually on the rise. Bee products that are used as food and food supplements and drug concentrations in the historic process are drawing the attention with their marvellous characteristic features. The search for nourishment of the body on behalf of healthy living is currently being searched by many people. Therefore, the consumption of products that protect the health appears as the primary preference of people. In the light of this recent tendency, food sector is now offering well-supported products that are suitable for this preference. At this point, bee products such as honey, pollen, bee bread, royal jelly and propolis gain importance as functional food with their nutritious features that help in protecting the health. In this article, within the consideration of the researches that evaluate bee products as functional food, we aim to introduce the prominence of bee products in our nourishment and overall health

CDS Implied Default Probabilities: A Study of a Reduced Form Model for Credit Risk

ABSTRACT This study estimates risk-neutral probability of default from quoted Credit Default Swap (CDS) spreads by employing Hull and White (2000 and 2003) reduced form model for pricing CDS. Once fixing the recovery rate at a predetermined level, we introduce default probability density, q(t) in two forms; a continuous piecewise linear function and a step function. Considering CDS maturity times we extract default probability densities recursively from the model based on the CDS spreads quoted for each maturity. To apply the method to real life data, we construct term structure of default probability densities of 10 UK firms operating in various sectors and with different credit ratings over the three measurement dates: May 1, 2007, December 31, 2008 and December 31, 2009. These dates are believed to reflect changes in market conditions during the period 2007-2009 which covers subprime mortgage crisis. For this analysis, we use one year forward rates estimated from treasury rates as reference risk-free rate. The results suggest that the default probability densities record lowest values in 2007 for most of the firms and the typical positive relation between the default probability and maturity reverses in 2008 when default probability densities usually decline with longer maturities. We also test the model’s performance in terms of discriminating defaulters from non-defaulters by means of Receiver Operating Characteristics (ROC). We use U.S. firms for this analysis and compare performances of different default probability measures calculated based on the CDS implied default probabilities. We find that our model has a very strong discriminatory power in terms of firm defaults, despite a weakness arisen from period dependent analysis due to insufficient CDS data

Minimally-invasive Microneedle-based Biosensor Array for Simultaneous Lactate and Glucose Monitoring in Artificial Interstitial Fluid

Here we report the first mediated pain free microneedle‐based biosensor array for the continuous and simultaneous monitoring of lactate and glucose in artificial interstitial fluid (ISF). The gold surface of the microneedles has been modified by electrodeposition of Au‐multiwalled carbon nanotubes (MWCNTs) and successively by electropolymerization of the redox mediator, methylene blue (MB). Functionalization of the Au‐MWCNTs/polyMB platform with the lactate oxidase (LOX) enzyme (working electrode 1) and with the FAD‐Glucose dehydrogenase (FADGDH) enzyme (working electrode 2) enabled the continuous monitoring of lactate and glucose in the artificial ISF. The lactate biosensor exhibited a high sensitivity (797.4±38.1 μA cm−2 mM−1), a good linear range (10–100 μM) with a detection limit of 3 μM. The performance of the glucose biosensor were also good with a sensitivity of 405.2±24.1 μA cm−2 mM−1, a linear range between 0.05 and 5 mM and a detection limit of 7 μM. The biosensor array was tested to detect the amount of lactate generated after 100 minutes of cycling exercise (12 mM) and of glucose after a normal meal for a healthy patient (10 mM). The results reveal that the new microneedles‐based biosensor array seems to be a promising tool for the development of real‐time wearable devices with a variety of sport medicine and clinical care applications

Fiberoptic Microneedles for Transdermal Light Delivery

Shallow light penetration in tissue has been a technical barrier to the development of photothermal therapies for cancers in the epithelial tissues and skin. This problem can potentially be solved by utilizing minimally invasive probes to deliver light directly to target areas potentially > 2 mm deep within tissue. To develop this solution, fiber optic microneedles capable of delivering light for therapy were manufactured. We have manufactured fiberoptic microneedles by tapering silica-based optical fibers employing a melt-drawing process. These fiberoptic microneedles were 35 to 139 microns in diameter and 3 mm long. Some of the microneedles were manufactured to have sharper tips (tip diameter < 8 microns) by changing the heat source during the melt-drawing process. All of the microneedles were individually inserted into ex vivo porcine skin samples to demonstrate the feasibility of their application in human tissues. Skin penetration experiments showed that sharp fiber optic microneedles with a minimum average diameter of 73 microns and a maximum tip diameter of 8 microns were able to penetrate skin without buckling. Flat microneedles, which had larger tip diameters, required a minimum average diameter of 125 microns in order to penetrate through porcine skin samples. Force versus displacement plots showed that a sharp tip on a fiber optic microneedle decreased the skin's resistance during insertion. Also, the force acting on a sharp microneedle increased more steadily compared with a microneedle with a flat tip. Melt-drawn fiberoptic microneedles provided a means to mechanically penetrate dermal tissue and deliver light directly into a localized target area. We also described an alternate fiberoptic microneedle design with the capability of delivering more diffuse, but therapeutically useful photothermal energy using hydrofluoric acid etching of optical fibers. Microneedles etched for 10, 30, and 50 minutes, and an optical fiber control was compared for their ability to deliver diffuse light using three techniques. First, red light delivery from the microneedles was evaluated by imaging the reflectance of the light from a white paper. Second, spatial temperature distribution of the paper in response to near-IR light (1,064 nm, 1 W, CW) was recorded using infrared thermography. Third, ex vivo adipose tissue response during 1,064 nm, (5 W, CW) irradiation was recorded with bright field microscopy. Increasing etching time decreased microneedle diameter (from 125 to 33 microns), resulting in increased uniformity of red and 1,064 nm light delivery along the microneedle axis. For equivalent total energy delivery, microneedles with smaller diameters reduced carbonization in the adipose tissue experiments. However, thin fiberoptic microneedles designed to minimize tissue disruption and deliver diffuse therapeutic light are limited in their possible clinical application due to a lack of mechanical strength. Fiberoptic microneedles have been embedded in an elastomeric support medium (polydimethylsiloxane, PDMS) to mitigate this issue. The critical buckling force of silica microneedles with 55, 70, and 110 microns diameters and 3 mm length were measured with and without the elastomeric support in place (N = 5). Average increases in the mechanical strength for microneedles of 55, 70, and 110 microns diameters were measured to be 610%, 290%, and 33%, respectively. Aided by mechanical strengthening through an elastomeric support, microneedles with 55 microns diameter were able to repeatedly penetrate ex vivo porcine skin.Ph. D

CDS Implied Default Probabilities: A Study of a Reduced Form Model for Credit Risk

ABSTRACT This study estimates risk-neutral probability of default from quoted Credit Default Swap (CDS) spreads by employing Hull and White (2000 and 2003) reduced form model for pricing CDS. Once fixing the recovery rate at a predetermined level, we introduce default probability density, q(t) in two forms; a continuous piecewise linear function and a step function. Considering CDS maturity times we extract default probability densities recursively from the model based on the CDS spreads quoted for each maturity. To apply the method to real life data, we construct term structure of default probability densities of 10 UK firms operating in various sectors and with different credit ratings over the three measurement dates: May 1, 2007, December 31, 2008 and December 31, 2009. These dates are believed to reflect changes in market conditions during the period 2007-2009 which covers subprime mortgage crisis. For this analysis, we use one year forward rates estimated from treasury rates as reference risk-free rate. The results suggest that the default probability densities record lowest values in 2007 for most of the firms and the typical positive relation between the default probability and maturity reverses in 2008 when default probability densities usually decline with longer maturities. We also test the model’s performance in terms of discriminating defaulters from non-defaulters by means of Receiver Operating Characteristics (ROC). We use U.S. firms for this analysis and compare performances of different default probability measures calculated based on the CDS implied default probabilities. We find that our model has a very strong discriminatory power in terms of firm defaults, despite a weakness arisen from period dependent analysis due to insufficient CDS data