The age estimation of biological traces is one of the holy grails in forensic investigations. We developed a method for the age estimation of semen stains using fluorescence spectroscopy in conjunction with a stoichiometric ageing model. The model describes the degradation and generation rate of proteins and fluorescent oxidation products (FOX) over time. The previously used fluorimeter is a large benchtop device and requires system optimization for forensic applications. In situ applications have the advantage that measurements can be performed directly at the crime scene, without additional sampling or storage steps. Therefore, a portable fiber-based fluorimeter was developed, consisting of two optimized light-emitting diodes (LEDs) and two spectrometers to allow the fluorescence protein and FOX measurements. The handheld fiber can be used without touching the traces, avoiding the destruction or contamination of the trace. In this study, we have measured the ageing kinetics of semen stains over time using both our portable fluorimeter and a laboratory benchtop fluorimeter and compared their accuracies for the age estimation of semen stains. Successful age estimation was possible up to 11 days, with a mean absolute error of 1.0 days and 0.9 days for the portable and the benchtop fluorimeters, respectively. These results demonstrate the potential of using the portable fluorimeter for in situ applications.
DOCUMENT
Light scattering is a fundamental property that can be exploited to create essential devices such as particle analysers. The most common particle size analyser relies on measuring the angle-dependent diffracted light from a sample illuminated by a laser beam. Compared to other non-light-based counterparts, such a laser diffraction scheme offers precision, but it does so at the expense of size, complexity and cost. In this paper, we introduce the concept of a new particle size analyser in a collimated beam configuration using a consumer electronic camera and machine learning. The key novelty is a small form factor angular spatial filter that allows for the collection of light scattered by the particles up to predefined discrete angles. The filter is combined with a light-emitting diode and a complementary metal-oxide-semiconductor image sensor array to acquire angularly resolved scattering images. From these images, a machine learning model predicts the volume median diameter of the particles. To validate the proposed device, glass beads with diameters ranging from 13 to 125 µm were measured in suspension at several concentrations. We were able to correct for multiple scattering effects and predict the particle size with mean absolute percentage errors of 5.09% and 2.5% for the cases without and with concentration as an input parameter, respectively. When only spherical particles were analysed, the former error was significantly reduced (0.72%). Given that it is compact (on the order of ten cm) and built with low-cost consumer electronics, the newly designed particle size analyser has significant potential for use outside a standard laboratory, for example, in online and in-line industrial process monitoring.
MULTIFILE
The transmission of constant-envelope orthogonal frequency division multiplexing (CE-OFDM) signals, based on electrical phase modulation, was shown to improve the tolerance to noise and the nonlinearity introduced by light-emitting diodes (LEDs) in visible light communication (VLC) systems. This allows the application of larger signal amplitudes despite the LED-nonlinearities and, thus, data transmission over larger distances. The performance of a 9.51 Mb/s CE-OFDM based system, with 16-QAM subcarrier mapping in a bandwidth of 5 MHz, was compared to the efficiency of a conventional OFDM system. The error vector magnitude (EVM) was reduced from 17.5% to 10% (which is below the FEC limit), an improvement around 43%, when the CE-OFDM scheme was applied in the VLC link of 6 m. A good performance was achieved by the CE-OFDM based VLC system in a link of 8 m, when 4-QAM was used as subcarrier mapping.
DOCUMENT
Despite Dutch Hospitality industry’s significant economic value, employers struggle to attract and retain early career professionals at a time when tourism is forecasted to grow exponentially (Ruël, 2018). Universally, hospitality management graduates are shunning hospitality careers preferring other career paths; stimulating the Dutch Hospitality to find innovative ways of attracting and retaining early career professionals. Following calls from the Human Resource Management (HRM) community (Ehnert, 2009), we attribute this trend to personnel being depicted as rentable resources, driving profit’’ often at personal expense. For example, hotels primarily employ immigrants and students for a minimum wage suppressing salaries of local talent (Kusluvan, et al 2010, O’Relly and Pfeffer, 2010). Similarly, flattening organizational structures have eliminated management positions, placing responsibility on inexperienced shoulders, with vacancies commonly filled by pressured employees accepting unpaid overtime jeopardizing their work life balance (Davidson, et al 2010,). These HRM practices fuel attrition by exposing early career professionals to burnout (Baum et al, 2016, Goh et al, 2015, Deery and Jog, 2009). Collectively this has eroded the industry’s employer brand, now characterized by unsocial working hours, poor compensation, limited career opportunities, low professional standing, high turnover and substance abuse (Mooney et al, 2016, Gehrels and de Looij, 2011). In contrast, Sustainable HRM “enables an organizational goal achievement while simultaneously reproducing the human resource base over a long-lasting calendar time (Ehnert, 2009, p. 74).” Hence, to overcome this barrier we suggest embracing the ROC framework (Prins et al, 2014), which (R)espects internal stakeholders, embraces an (O)pen HRM approach while ensuring (C)ontinuity of economic and societal sustainability which could overcome this barrier. Accordingly, we will employ field research, narrative discourse, survey analysis and quarterly workshops with industry partners, employees, union representatives, hotel school students to develop sustainable HRM practices attracting and retaining career professionals to pursue Dutch hospitality careers.
Consumenten wensen light-emitting diodes (LEDs) die energie-efficiënt zijn, maar tegelijkertijd de gewenste kleuren licht uitzenden. Binnenverlichting moet bijvoorbeeld voldoende rood bevatten om een warme sfeer te creëren, terwijl beeldschermen mooie pure kleuren moeten produceren. De Universiteit Utrecht en het bedrijf Seaborough B.V. gaan samenwerken aan nieuwe manieren om efficiënt licht te genereren met nanokristallen. Nanokristallen hebben als voordeel dat het uitgezonden lichtspectrum nauwkeurig kan worden gestuurd en dat hun fabricage minder schaarse materialen gebruikt dan bestaande technologieën. Om ze licht te laten uitzenden, moet er echter energie worden toegevoerd. De onderzoekers gaan een strategie uittesten om energie zo snel en efficiënt mogelijk door een dunne film van nanokristallen te laten reizen. De beoogde strategie berust op het gebruik van golfgeleiders, die elektromagnetische straling in een gewenst richting sturen. Succes in dit project zal bijdragen aan het efficiënter en mooier maken van kunstmatige lichtbronnen, terwijl er minder materialen gebruikt hoeven te worden.
Light-emitting diodes (LEDs) vervangen andere typen kunstmatige verlichting in rap tempo, omdat ze zuiniger en robuuster zijn. LEDs vormen dan ook een alsmaar groeiende markt van vele tientallen miljarden. De meest voorkomende technologie maakt gebruik van InGaN om blauw licht te maken onder elektrische aandrijving. “Fosforen” zetten vervolgens een deel van dit blauwe licht om in de andere kleuren van de regenboog. Helaas werken bestaande fosforen vooral goed in toepassingen waarbij lage lichtintensiteit voldoende is. Bij hogere lichtintensiteit treedt “verzadiging” op: de efficiëntie van kleuromzetting wordt minder. Dit leidt tot energieverliezen. Daarnaast kan verzadiging de kleurbeleving van een LED-lamp ongewenst blauwig oftewel “koel” maken, aangezien vooral “warme” rode fosforen last hebben van dit probleem. De onderzoekers willen innovatieve fosformaterialen ontwerpen die efficiënt blijven ook bij hoge lichtintensiteit. Ze gaan samengestelde nanomaterialen maken met twee componenten, waarbij blauw licht wordt geabsorbeerd door de ene component en rood licht uitgezonden door de andere. Via het ontwerp van de samengestelde fosfor kan de snelheid van energieoverdracht van de ene naar de andere component worden gecontroleerd. Berekeningen wijzen uit dat slim gebruik van energieoverdracht verzadiging van de kleuromzetting kan verminderen. Dit project zal deze berekeningen toetsen en de praktische mogelijkheden verkennen om dit concept te gebruiken. Het kan daarmee de basis leggen voor vervolgonderzoek waar de beste ontwerpen verder worden ontwikkeld tot heldere rode fosforen. Deze zijn nodig voor de realisatie van zuinigere verlichting met een prettigere kleurbeleving voor de consument.
