Optimizing Chaotic Dynamics in a Semiconductor Laser with Dual Optical Feedback

Semiconductor lasers subject to optical feedback can behave chaotically, which can be used as a source of randomness. The optical feedback, provided by mirrors at a distance, determines the characteristics of the chaos and thus the quality of the randomness. However, this fixed distance also shows itself in the intensity, an unwanted feature called the Time Delay Signature (TDS). One promising solution to optimize the chaotic behavior is using double optical feedback, which we study here. In particular, we focus on the impact of the feedback phase, a small sub-wavelength change in the position of the mirrors, on the TDS and complexity of the system. We show that by optimizing the feedback parameters, including the feedback phases, the TDS can be suppressed, and that in some cases feedback phase control is necessary rather than optional. With control of all feedback parameters, it is possible to suppress the TDS without loss of the chaotic bandwidth. Further, we show that the system can restabilize at strong feedback rates, and one can switch between a chaotic and steady state by changing the feedback phase. Finally, we relate the feedback phase sensitivity to interference between the two delayed signals. This system is promising as one can either suppress the TDS without loss of the chaotic bandwidth or significantly increase the chaotic bandwidth.Comment: 9 pages, 7 figures, submitte

Insight into the dynamics of a long-runout mass movement using single-grain feldspar luminescence in the Pokhara Valley, Nepal

Mass movements play an important role in landscape evolution of high mountain areas such as the Himalayas. Yet, establishing numerical age control and reconstructing transport dynamics of past events is challenging. To fill this research gap, we bring luminescence dating to the test in an extremely challenging environment: the Pokhara Valley in Nepal. This is challenging for two reasons: (i) the optically stimulated luminescence (OSL) sensitivity of quartz, typically the mineral of choice for dating sediments younger than 100 ka, is poor, and (ii) highly rapid and turbid conditions during mass movement transport hamper sufficient OSL signal resetting prior to deposition, which eventually results in age overestimation. Here, we first assess the applicability of single-grain feldspar dating of medieval mass movement deposits catastrophically emplaced in the Pokhara Valley. Second, we exploit the poor bleaching mechanisms to get insight into the sediment dynamics of this paleo-mass movement through bleaching proxies. The Pokhara Valley is a unique setting for our case study, considering the availability of an extensive independent radiocarbon dataset as a geochronological benchmark. Single-grain infrared stimulated luminescence (IRSL) signals were measured at 50 ∘C (IRSL-50) and post-infrared infrared stimulated luminescence signals at 150 ∘C (pIRIR-150). Our results show that the IRSL-50 signal is better bleached than the pIRIR-150 signal. A bootstrapped minimum age model (bMAM) is applied to retrieve the youngest subpopulation to estimate the paleodose. However, burial ages calculated with this paleodose overestimate the radiocarbon ages by an average factor of ∼23 (IRSL-50) and ∼72 (pIRIR-150), showing that dating of the Pokhara Formation with a single-grain approach was not successful for most samples. Some samples, however, only slightly overestimate the true emplacement age and thus could be used for a rough age estimation. Large inheritances in combination with the scatter in the single-grain dose distributions show that the sediments have been transported under extremely limited light exposure prior to deposition, which is consistent with the highly turbid nature of the sediment-laden flood and debris flows depositing the Pokhara gravels. To investigate the sediment transport dynamics in more detail, we studied three bleaching proxies: the percentage of grains in saturation 2D0 criteria, the percentage of best-bleached grains (2σ range of bMAM-De) and the overdispersion (OD). None of the three bleaching proxies indicate a spatial relationship with runout distance of the mass movement deposits. We interpret this as evidence for the lack of bleaching during transport, which reflects the catastrophic nature of the event. While not providing reliable burial ages of the Pokhara mass movement deposits, single-grain feldspar dating can potentially be used as an age range finder method. Our approach shows the potential of luminescence techniques to provide insights in sediment transport dynamics of extreme and rare mass movement events in mountainous regions.</p

Кожный аллотрансплантат, консервированный в глицероле – ключ к эффективной подготовке раневого ложа

Queen Fabiola Children’s University Hospital, Brussels, Belgium, Brugmann University Hospital, Brussels, BelgiumFor spontaneous wound healing to occur, wound preparation must be optimised. This may be impaired by several factors. This paper presents the authors experience and philosophy regarding wound bed preparation of extensive and complicated wounds. After the removal of all devitalized tissue, angiogenesis of the wound bed is promoted by the temporary application of the glycerol preserved allograft. This study included all patients with burns and wounds, who were admitted to the Queen Fabiola Children’s University Hospital in Brussels from January 2010 to November 2010 who had been treated with a glycerol preserved allograft. The results of the study showed the high effectiveness of these kinds of treatments: infection control, stimulation of angiogenesis, and granulation tissue formation.Спонтанное заживление раны может быть нарушено различными неблагоприятними факторами. Раневое ложе должно быть подготовленно. В этой статье авторы поделились своим опытом и тактикой подготовки раневого ложа обширных и осложнённых ран. После удаления всех нежизнеспособных тканей, ангиогенез был стимулирован путём временной аппликации кожного аллотрансплантата, консервированного в глицероле. В данное исследование были включены пациенты с ожогами и ранами, поступившие в Детский Университетский Госпиталь Королевы Фабиолы в Брюсселе с января по ноябрь 2010 года, в лечении которых был использован кожный аллотрансплантат, консервированный в глицероле. Результаты показали высокую эффективность данного лечения: контроль инфекции, стимуляция ангиогенеза, формирование грануляционной ткани, предотвращение контрактур и др

Differential bleaching of quartz and feldspar luminescence signals under high-turbidity conditions

Sediment burial dating using optically stimulated luminescence (OSL) is a well-established tool in geochronology. An important but often inapplicable requirement for its successful use is that the OSL signal is sufficiently reset prior to deposition. However, subaqueous bleaching conditions during fluvial transport are vastly understudied; for example the effect of turbidity and sediment mixing on luminescence bleaching rates is only poorly established. The possibility that slow bleaching rates may dominate under certain transport conditions led to the concept that OSL could be used to derive sediment transport histories. The feasibility of this concept is still to be demonstrated, and experimental set-ups are still to be tested. Our contribution to this scientific challenge involves subaquatic bleaching experiments, in which we suspend saturated coastal sand of Miocene age in a circular flume and illuminate it for discrete time intervals with natural light. We record the in situ energy flux density received by the suspended grains in the UV-NIR frequency range by using a broadband spectrometer with a submersible probe. Our analysis includes pre-profiling of each sample following a polymineral multiple signal (PMS) protocol. Using the PMS, the quartz-dominated, blue-stimulated luminescence signal at 125 ∘C (BSL-125) decays slower than the K-feldspar-dominated, infrared-stimulated luminescence signal at 25 ∘C (IR-25) even under subaerial conditions. The BSL-125 from purified quartz shows the opposite behaviour, which renders the PMS unreliable in our case. We find a negative correlation between suspended-sediment concentration and bleaching rate for all the measured signals. For outdoor bleaching experiments we propose to relate the measured luminescence dose to the cumulative received irradiance rather than to the bleaching time. Increases in the sediment concentration lead to a stronger attenuation of the UV–blue compared to the red–NIR wavelength. This attenuation thereby follows an exponential decay that is controlled by the sediment concentration and a wavelength-dependent decay constant, λ. As such λ could potentially be used in numerical models of luminescence signal resetting in turbid suspensions.</p

Variational assimilation of Lagrangian data in oceanography

We consider the assimilation of Lagrangian data into a primitive equations circulation model of the ocean at basin scale. The Lagrangian data are positions of floats drifting at fixed depth. We aim at reconstructing the four-dimensional space-time circulation of the ocean. This problem is solved using the four-dimensional variational technique and the adjoint method. In this problem the control vector is chosen as being the initial state of the dynamical system. The observed variables, namely the positions of the floats, are expressed as a function of the control vector via a nonlinear observation operator. This method has been implemented and has the ability to reconstruct the main patterns of the oceanic circulation. Moreover it is very robust with respect to increase of time-sampling period of observations. We have run many twin experiments in order to analyze the sensitivity of our method to the number of floats, the time-sampling period and the vertical drift level. We compare also the performances of the Lagrangian method to that of the classical Eulerian one. Finally we study the impact of errors on observations.Comment: 31 page

Malignant transformation of an abdominal inflammatory myofibroblastic tumor with distant metastases in a child

Inflammatory myofibroblastic tumors (IMT) are lesions that mostly affect young adults and children. The tumor is made up of myofibroblasts and a mixed inflammatory infiltrate and rarely undergoes malignant transformation. We present a case of a 13-year-old boy with a pelvic mass diagnosed as IMT which underwent malignant transformation and metastasised to the liver. We report the ultrasound, computed tomography (CT) and magnetic resonance (MR) findings of this rare disorder

Interdisciplinary research: putting the methods under the microscope

BACKGROUND: While the desirability of interdisciplinary inquiry has been widely acknowledged, indeed has become 'the mantra of science policy', the methods of interdisciplinary collaboration are opaque to outsiders and generally remain undescribed. DISCUSSION: Many have analysed interdisciplinarity, especially in relation to the creation of new disciplines and institutions. These analyses are briefly outlined. Still, there currently persists a silence about the methods of interdisciplinary collaboration itself, and the core of this paper proposes a template for such methods. SUMMARY: Breaking this silence – by making the methods of interdisciplinary projects transparent – could further invigorate interdisciplinary research