Showing papers by "Philips published in 2010"

Light trapping in ultrathin plasmonic solar cells.

Abstract: We report on the design, fabrication, and measurement of ultrathin film a-Si:H solar cells with nanostructured plasmonic back contacts, which demonstrate enhanced short circuit current densities compared to cells having flat or randomly textured back contacts. The primary photocurrent enhancement occurs in the spectral range from 550 nm to 800 nm. We use angle-resolved photocurrent spectroscopy to confirm that the enhanced absorption is due to coupling to guided modes supported by the cell. Full-field electromagnetic simulation of the absorption in the active a-Si:H layer agrees well with the experimental results. Furthermore, the nanopatterns were fabricated via an inexpensive, scalable, and precise nanopatterning method. These results should guide design of optimized, non-random nanostructured back reflectors for thin film solar cells.

Applications, challenges, and prospective in emerging body area networking technologies

Abstract: Advances in wireless technology and supporting infrastructure provide unprecedented opportunity for ubiquitous real-time healthcare and fitness monitoring without constraining the activities of the user. Wirelessly connected miniaturized sensors and actuators placed in, on, and around the body form a body area network for continuous, automated, and unobtrusive monitoring of physiological signs to support medical, lifestyle and entertainment applications. BAN technology is in the early stage of development, and several research challenges have to be overcome for it to be widely accepted. In this article we study the core set of application, functional, and technical requirements of the BAN. We also discuss fundamental research challenges such as scalability (in terms of data rate, power consumption, and duty cycle), antenna design, interference mitigation, coexistence, QoS, reliability, security, privacy, and energy efficiency. Several candidate technologies poised to address the emerging BAN market are evaluated, and their merits and demerits are highlighted. A brief overview of standardization activities relevant to BANs is also presented.

A survey of stimulation methods used in SSVEP-based BCIs

Abstract: Brain-computer interface (BCI) systems based on the steady-state visual evoked potential (SSVEP) provide higher information throughput and require shorter training than BCI systems using other brain signals. To elicit an SSVEP, a repetitive visual stimulus (RVS) has to be presented to the user. The RVS can be rendered on a computer screen by alternating graphical patterns, or with external light sources able to emit modulated light. The properties of an RVS (e.g., frequency, color) depend on the rendering device and influence the SSVEP characteristics. This affects the BCI information throughput and the levels of user safety and comfort. Literature on SSVEP-based BCIs does not generally provide reasons for the selection of the used rendering devices or RVS properties. In this paper, we review the literature on SSVEP-based BCIs and comprehensively report on the different RVS choices in terms of rendering devices, properties, and their potential influence on BCI performance, user safety and comfort.

User experience evaluation methods: current state and development needs

Abstract: The recent shift of emphasis to user experience (UX) has rendered it a central focus of product design and evaluation. A multitude of methods for UX design and evaluation exist, but a clear overview of the current state of the available UX evaluation methods is missing. This is partly due to a lack of agreement on the essential characteristics of UX. In this paper, we present the results of our multi-year effort of collecting UX evaluation methods from academia and industry with different approaches such as literature review, workshops, Special Interest Groups sessions and an online survey. We have collected 96 methods and analyzed them, among other criteria, based on the product development phase and the studied period of experience. Our analysis reveals development needs for UX evaluation methods, such as early-stage methods, methods for social and collaborative UX evaluation, establishing practicability and scientific quality, and a deeper understanding of UX.

Organic Nonvolatile Memory Devices Based on Ferroelectricity

Abstract: A memory functionality is a prerequisite for many applications of electronic devices. Organic nonvolatile memory devices based on ferroelectricity are a promising approach toward the development of a low-cost memory technology. In this Review Article we discuss the latest developments in this area with a focus on three of the most important device concepts: ferroelectric capacitors, field-effect transistors, and diodes. Integration of these devices into larger memory arrays is also discussed.

Prostate cancer: value of multiparametric MR imaging at 3 T for detection--histopathologic correlation.

Abstract: Combined use of anatomic (T2-weighted MR imaging) and functional (MR spectroscopy and dynamic contrast material–enhanced MR imaging) modalities improves the performance of MR imaging for prostate tumor detection.

The IEEE 802.11 universe

Abstract: The introduction of IEEE's 80211 standards has enabled a mass market, with a huge impact in the home, office, and public areas Today, laptops, PCs, printers, cellular phones, VoIP phones, MP3 players, Blu-Ray players, and many more devices incorporate wireless LAN technology With low-cost chipsets and support for high data rates, 80211 has become a universal solution for an ever increasing application space As a direct consequence of its high market penetration, several amendments to the basic 80211 standard have been developed or are under development They fix technology issues or add functionality expected to be required by future applications In this article we overview the emerging 80211 standard and address the technical context of its extensions The article highlights its finalized amendments and those under development

Efficient Solar Cells Based on an Easily Accessible Diketopyrrolopyrrole Polymer

Abstract: A new easily accessible, high molecular weight, alternating dithieno-diketopyrrolopyrrolophenylene copolymer provides high electron and hole mobilities exceeding 0.02 cm2 V-1 s-1 in FETs and AM1.5 power conversion efficiencies of 4.6% and 5.5% in solar cells when combined with [60]PCBM and [70]PCBM. The performance of the solar cells strongly depends on the use of a processing agent.

Compressed sensing reconstruction for magnetic resonance parameter mapping

Abstract: Compressed sensing (CS) holds considerable promise to accelerate the data acquisition in magnetic resonance imaging by exploiting signal sparsity. Prior knowledge about the signal can be exploited in some applications to choose an appropriate sparsifying transform. This work presents a CS reconstruction for magnetic resonance (MR) parameter mapping, which applies an overcomplete dictionary, learned from the data model to sparsify the signal. The approach is presented and evaluated in simulations and in in vivo T(1) and T(2) mapping experiments in the brain. Accurate T(1) and T(2) maps are obtained from highly reduced data. This model-based reconstruction could also be applied to other MR parameter mapping applications like diffusion and perfusion imaging.

IEEE 802.11s: The WLAN Mesh Standard

Abstract: The wireless local area network standard IEEE 802.11 is the preferred solution for lowcost data services. Key to its success are the 2.4 and 5 GHz unlicensed bands. The transmit power limitations imposed due to regulatory requirements limit the range (coverage) that can be achieved by WLANs in these bands. However, the demand for "larger" wireless infrastructure is emerging, ranging from office/university campuses to city-wide deployments. To overcome the limitations of singlehop communication, data packets need to traverse over multiple wireless hops, and wireless mesh networks are called for. Since 2004 Task Group S has been developing an amendment to the 802.11 standard to exactly address the aforementioned need for multihop communication. Besides introducing wireless frame forwarding and routing capabilities at the MAC layer, the 802.11s amendment brings new interworking and security. In this article, we provide insights into the latest developments in 802.11s and explain how the overall mesh concept fits into the 802 set of networking standards.

Expressive robots in education: varying the degree of social supportive behavior of a robotic tutor

Abstract: Teaching is inherently a social interaction between teacher and student. Despite this knowledge, many educational tools, such as vocabulary training programs, still model the interaction in a tutoring scenario as unidirectional knowledge transfer rather than a social dialog. Therefore, ongoing research aims to develop virtual agents as more appropriate media in education. Virtual agents can induce the perception of a life-like social interaction partner that communicates through natural modalities such as speech, gestures and emotional expressions. This effect can be additionally enhanced with a physical robotic embodiment. This paper presents the development of social supportive behaviors for a robotic tutor to be used in a language learning application. The effect of these behaviors on the learning performance of students was evaluated. The results support that employing social supportive behavior increases learning efficiency of students.

Deeply penetrating in vivo photoacoustic imaging using a clinical ultrasound array system.

Abstract: Using a hand-held photoacoustic probe integrated with a clinical ultrasound array system, we successfully imaged objects deeply positioned in biological tissues. The optical contrasts were enhanced by methylene blue with a concentration of ~30 mM. The penetration depth reached ~5.2 cm in chicken breast tissue by using 650-nm wavelength, which is ~4.7 times the 1/e optical penetration depth. This imaging depth was achieved using a laser fluence on the tissue surface of only 3 mJ/cm2, which is 1/7 of the American National Standards Institute (ANSI) safety limit (20 mJ/cm2). The noise equivalent sensitivity at this depth was ~11 mM. Further, after intradermal injection of methylene blue in a rat, a sentinel lymph node was easily detected in vivo, beneath a 2-cm thick layer of chicken breast. Also, blood located 3.5 cm deep in the rat was clearly imaged with intrinsic contrast. We have photoacoustically guided insertion of a needle into a rat sentinel lymph node with accumulated methylene blue. These results highlight the clinical potential of photoacoustic image-guided identification and needle biopsy of sentinel lymph nodes for axillary staging in breast cancer patients.

Sentinel lymph nodes in the rat: noninvasive photoacoustic and US imaging with a clinical US system.

Abstract: Purpose: To evaluate in vivo sentinel lymph node (SLN) mapping by using photoacoustic and ultrasonographic (US) imaging with a modified clinical US imaging system. Materials and Methods: Animal protocols were approved by the Animal Studies Committee. Methylene blue dye accumulation in axillary lymph nodes of seven healthy Sprague-Dawley rats was imaged by using a photoacoustic imaging system adapted from a clinical US imaging system. To investigate clinical translation, the imaging depth was extended up to 2.5 cm by adding chicken or turkey breast on top of the rat skin surface. Three-dimensional photoacoustic images were acquired by mechanically scanning the US transducer and light delivery fiber bundle along the elevational direction. Results: Photoacoustic images of rat SLNs clearly help visualization of methylene blue accumulation, whereas coregistered photoacoustic/US images depict lymph node positions relative to surrounding anatomy. Twenty minutes following methylene blue injection, photoacoustic signals from SLN regions increased nearly 33-fold from baseline signals in preinjection images, and mean contrast between SLNs and background tissue was 76.0 ± 23.7 (standard deviation). Methylene blue accumulation in SLNs was confirmed photoacoustically by using the optical absorption spectrum of the dye. Three-dimensional photoacoustic images demonstrate dynamic accumulation of methylene blue in SLNs after traveling through lymph vessels. Conclusion: In vivo photoacoustic and US mapping of SLNs was successfully demonstrated with a modified clinical US scanner. These results raise confidence that photoacoustic and US imaging can be used clinically for accurate, noninvasive imaging of SLNs for axillary lymph node staging in breast cancer patients.

Method and apparatus for using light emitting diodes

Abstract: The present invention provides a method and apparatus for using light emitting diodes for curing and various solid state lighting applications. The method includes a novel method for cooling the light emitting diodes and mounting the same on heat pipe in a manner which delivers ultra high power in UV, visible and IR regions. Furthermore, the unique LED packaging technology of the present invention utilizes heat pipes that perform very efficiently in very compact space. Much more closely spaced LEDs operating at higher power levels and brightness are possible because the thermal energy is transported in an axial direction down the heat pipe and away from the light-emitting direction rather than a radial direction in nearly the same plane as the “p-n” junction.

Estimation of lipid and water concentrations in scattering media with diffuse optical spectroscopy from 900 to 1600 nm

Abstract: We demonstrate a method to estimate the concentrations of water and lipid in scattering media such as biological tissues with diffuse optical spectra acquired over the range of 900 to 1600 nm. Estimations were performed by fitting the spectra to a model of light propagation in scattering media derived from diffusion theory. To validate the method, spectra were acquired from tissue phantoms consisting of lipid and water emulsions and swine tissues ex vivo with a two-fiber probe.

Multi-cancer computational analysis reveals invasion-associated variant of desmoplastic reaction involving INHBA, THBS2 and COL11A1

Abstract: Despite extensive research, the details of the biological mechanisms by which cancer cells acquire motility and invasiveness are largely unknown. This study identifies an invasion associated gene signature shedding light on these mechanisms. We analyze data from multiple cancers using a novel computational method identifying sets of genes whose coordinated overexpression indicates the presence of a particular phenotype, in this case high-stage cancer. We conclude that there is one shared "core" metastasis-associated gene expression signature corresponding to a specific variant of stromal desmoplastic reaction, present in a large subset of samples that have exceeded a threshold of invasive transition specific to each cancer, indicating that the corresponding biological mechanism is triggered at that point. For example this threshold is reached at stage IIIc in ovarian cancer and at stage II in colorectal cancer. Therefore, its presence indicates that the corresponding stage has been reached. It has several features, such as coordinated overexpression of particular collagens, mainly COL11A1 and other genes, mainly THBS2 and INHBA. The composition of the overexpressed genes indicates invasion-facilitating altered proteolysis in the extracellular matrix. The prominent presence in the signature of INHBA in all cancers strongly suggests a biological mechanism centered on activin A induced TGF-β signaling, because activin A is a member of the TGF-β superfamily consisting of an INHBA homodimer. Furthermore, we establish that the signature is predictive of neoadjuvant therapy response in at least one breast cancer data set. Therefore, these results can be used for developing high specificity biomarkers sensing cancer invasion and predicting response to neoadjuvant therapy, as well as potential multi-cancer metastasis inhibiting therapeutics targeting the corresponding biological mechanism.

Weighted iterative reconstruction for magnetic particle imaging

Abstract: Magnetic particle imaging (MPI) is a new imaging technique capable of imaging the distribution of superparamagnetic particles at high spatial and temporal resolution. For the reconstruction of the particle distribution, a system of linear equations has to be solved. The mathematical solution to this linear system can be obtained using a least-squares approach. In this paper, it is shown that the quality of the least-squares solution can be improved by incorporating a weighting matrix using the reciprocal of the matrix-row energy as weights. A further benefit of this weighting is that iterative algorithms, such as the conjugate gradient method, converge rapidly yielding the same image quality as obtained by singular value decomposition in only a few iterations. Thus, the weighting strategy in combination with the conjugate gradient method improves the image quality and substantially shortens the reconstruction time. The performance of weighting strategy and reconstruction algorithms is assessed with experimental data of a 2D MPI scanner.

Perception of affect elicited by robot motion

Abstract: Nonverbal behaviors serve as a rich source of information in inter human communication. In particular, motion cues can reveal details on a person's current physical and mental state. Research has shown, that people do not only interpret motion cues of humans in these terms, but also the motion of animals and inanimate devices such as robots. In order to successfully integrate mobile robots in domestic environments, designers have therefore to take into account how the device will be perceived by the user. In this study we analyzed the relationship between motion characteristics of a robot and perceived affect. Based on a literature study we selected two motion characteristics, namely acceleration and curvature, which appear to be most influential for how motion is perceived. We systematically varied these motion parameters and recorded participants interpretations in terms of affective content. Our results suggest a strong relation between motion parameters and attribution of affect, while the type of embodiment had no effect. Furthermore, we found that the level of acceleration can be used to predict perceived arousal and that valence information is at least partly encoded in an interaction between acceleration and curvature. These findings are important for the design of behaviors for future autonomous household robots.

Model-Based Reconstruction for Magnetic Particle Imaging

Abstract: Magnetic particle imaging (MPI) is a new imaging modality capable of imaging distributions of superparamagnetic nanoparticles with high sensitivity, high spatial resolution and, in particular, high imaging speed. The image reconstruction process requires a system function, describing the mapping between particle distribution and acquired signal. To date, the system function is acquired in a tedious calibration procedure by sequentially measuring the signal of a delta sample at the positions of a grid that covers the field of view. In this work, for the first time, the system function is calculated using a model of the signal chain. The modeled system function allows for reconstruction of the particle distribution in a 1-D MPI experiment. The approach thus enables fast generation of system functions on arbitrarily dense grids. Furthermore, reduction in memory requirements may be feasible by generating parts of the system function on the fly during reconstruction instead of keeping the complete matrix in memory.

Computed Tomography in Color: NanoK-Enhanced Spectral CT Molecular Imaging

Abstract: New multidetector cardiac computed tomography (MDCT) can image the heart within the span of a few beats, and as such, it is the favored noninvasive approach to assess coronary anatomy rapidly. However, MDCT has proven to be more useful for excluding coronary disease than for making positive diagnoses. The inability to detect unstable cardiac disease arises from the confounding attenuating effects of calcium deposits within atherosclerotic plaques, which obscure lumen anatomy, and from the insensitivity of CT X-rays to image low attenuating intraluminal thrombus adhered to a disrupted plaque cap, the absolute condition of ruptured plaque and unstable disease.[1–6] It is now well understood that the sensitive detection and quantification of small intravascular thrombus in coronary arteries with molecular imaging techniques could provide a direct metric to diagnose and risk stratify patients presenting with chest pain.[7,8]