Spatial homogeneity of optically switched semiconductor photonic crystals and of bulk semiconductors

This paper discusses free carrier generation by pulsed laser fields as a mechanism to switch the optical properties of semiconductor photonic crystals and bulk semiconductors on an ultrafast time scale. Requirements are set for the switching magnitude, the time-scale, the induced absorption as well as the spatial homogeneity, in particular for silicon at lambda= 1550 nm. Using a nonlinear absorption model, we calculate carrier depth profiles and define a homogeneity length l_hom. Homogeneity length contours are visualized in a plane spanned by the linear and two-photon absorption coefficients. Such a generalized homogeneity plot allows us to find optimum switching conditions at pump frequencies near v/c= 5000 cm^{-1} (lambda= 2000 nm). We discuss the effect of scattering in photonic crystals on the homogeneity. We experimentally demonstrate a 10% refractive index switch in bulk silicon within 230 fs with a lateral homogeneity of more than 30 micrometers. Our results are relevant for switching of modulators in absence of photonic crystals

Fiber transport of spatially entangled photons

Entanglement in the spatial degrees of freedom of photons is an interesting resource for quantum information. For practical distribution of such entangled photons it is desireable to use an optical fiber, which in this case has to support multiple transverse modes. Here we report the use of a hollow-core photonic crystal fiber to transport spatially entangled qubits.Comment: 4 pages, 4 figure

Hybrid-Entanglement in Continuous Variable Systems

Entanglement is one of the most fascinating features arising from quantum-mechanics and of great importance for quantum information science. Of particular interest are so-called hybrid-entangled states which have the intriguing property that they contain entanglement between different degrees of freedom (DOFs). However, most of the current continuous variable systems only exploit one DOF and therefore do not involve such highly complex states. We break this barrier and demonstrate that one can exploit squeezed cylindrically polarized optical modes to generate continuous variable states exhibiting entanglement between the spatial and polarization DOF. We show an experimental realization of these novel kind of states by quantum squeezing an azimuthally polarized mode with the help of a specially tailored photonic crystal fiber

Ultrafast optical switching of three-dimensional Si inverse opal photonic band gap crystals

We present ultrafast optical switching experiments on 3D photonic band gap crystals. Switching the Si inverse opal is achieved by optically exciting free carriers by a two-photon process. We probe reflectivity in the frequency range of second order Bragg diffraction where the photonic band gap is predicted. We find good experimental switching conditions for free-carrier plasma frequencies between 0.3 and 0.7 times the optical frequency: we thus observe a large frequency shift of up to D omega/omega= 1.5% of all spectral features including the peak that corresponds to the photonic band gap. We deduce a corresponding large refractive index change of Dn'_Si/n'_Si= 2.0% and an induced absorption length that is longer than the sample thickness. We observe a fast decay time of 21 ps, which implies that switching could potentially be repeated at GHz rates. Such a high switching rate is relevant to future switching and modulation applications

Excitation of higher-order modes in optofluidic hollow-core photonic crystal fiber

Higher-order modes are controllably excited in water-filled kagomè-, bandgap-style, and simplified hollow-core photonic crystal fibers (HC-PCF). A spatial light modulator is used to create amplitude and phase distributions that closely match those of the fiber modes, resulting in typical launch efficiencies of 10–20% into the liquid-filled core. Modes, excited across the visible wavelength range, closely resemble those observed in air-filled kagomè HC-PCF and match numerical simulations. These results provide a framework for spatially-resolved sensing in HC-PCF microreactors and fiber-based optical manipulation

A new method to measure Bowen ratios using high-resolution vertical dry and wet bulb temperature profiles

The Bowen ratio surface energy balance method is a relatively simple method to determine the latent heat flux and the actual land surface evaporation. The Bowen ratio method is based on the measurement of air temperature and vapour pressure gradients. If these measurements are performed at only two heights, correctness of data becomes critical. In this paper we present the concept of a new measurement method to estimate the Bowen ratio based on vertical dry and wet bulb temperature profiles with high spatial resolution. A short field experiment with distributed temperature sensing (DTS) in a fibre optic cable with 13 measurement points in the vertical was undertaken. A dry and a wetted section of a fibre optic cable were suspended on a 6 m high tower installed over a sugar beet trial plot near Pietermaritzburg (South Africa). Using the DTS cable as a psychrometer, a near continuous observation of vapour pressure and air temperature at 0.20 m intervals was established. These data allowed the computation of the Bowen ratio with a high spatial and temporal precision. The daytime latent and sensible heat fluxes were estimated by combining the Bowen ratio values from the DTS-based system with independent measurements of net radiation and soil heat flux. The sensible heat flux, which is the relevant term to evaluate, derived from the DTS-based Bowen ratio (BR-DTS) was compared with that derived from co-located eddy covariance (<i>R</i>² = 0.91), surface layer scintillometer (<i>R</i>² = 0.81) and surface renewal (<i>R</i>² = 0.86) systems. By using multiple measurement points instead of two, more confidence in the derived Bowen ratio values is obtained

Annual report on surveillance of respiratory infectious diseases 2013, the Netherlands

Het griepseizoen (influenza) 2013/2014 was erg mild, na de uitzonderlijk langdurende epidemie in het seizoen 2012/2013. Ook was het een mild seizoen wat betreft het aantal mensen dat een longontsteking (pneumonie) opliep. In 2013 waren er geen grote uitbraken van de meldingsplichtige luchtweginfectieziekten legionellose (308 meldingen), papegaaienziekte (psittacose; 51 meldingen), Q-koorts (19 meldingen) en tuberculose (848 meldingen). Deze aantallen waren in het verslagjaar vergelijkbaar of lager dan het aantal meldingen in voorgaande jaren. Dit blijkt uit de jaarlijkse surveillance luchtweginfectieziekten 2013 van het RIVM. Griep en longontsteking leiden tot veel ziekenhuisopnames en sterfte in Nederland, waardoor het RIVM ze actief volgt. In vergelijking met griep komen de meldingsplichtige luchtweginfecties in Nederlands maar weinig voor. Ze zijn meldingsplichtig, omdat tijdige maatregelen, zoals de besmettingsbron opsporen, belangrijk kunnen zijn om uitbraken of verdere verspreiding van de ziekte te voorkomen. Het RIVM volgt ook potentieel gevaarlijke nieuwe luchtweginfecties die elders in de wereld voorkomen. In mei 2014 werden voor het eerst in Nederland twee patiënten gediagnostiseerd met het MERS coronavirus. In het seizoen 2013/2014 lag het aantal mensen dat met griepachtige klachten bij de huisarts kwam begin 2014 gedurende vier weken boven de grens waarmee een griepepidemie wordt geduid. Bij de patiënten met griepachtige klachten kwam naast influenzavirus vaak RSV (respiratoir syncytieel virus) en neusverkoudheid (rhinovirus) voor. Er kwamen minder mensen met een longontsteking bij de huisarts dan voorgaande seizoenen, maar het aantal longontstekingpatiënten in verpleeghuizen bleef gelijk.The 2013/2014 influenza season was extremely mild in the Netherlands, compared to the exceptionally long-lasting epidemic in 2012/2013. In addition, the number of pneumonia patients and overall mortality, possible complications of influenza, were low. In 2013, no major outbreaks of the notifiable respiratory infectious diseases legionellosis (308 notifications), psittacosis (51 notifications), Q-fever (19 notifications) and tuberculosis (848 notifications) occurred. These incidences are either comparable to or lower than preceding years. These are the outcomes of the annual report: 'Surveillance of respiratory infectious diseases 2013, the Netherlands', published by the Dutch National Institute for Public Health and the Environment (RIVM). Influenza and pneumonia are an important cause of hospital admissions and death in the Netherlands, a reason for the RIVM to actively monitor these diseases. In comparison to influenza, notifiable respiratory infectious diseases only rarely occur. These diseases are notifiable, as timely measures like source finding, are important for preventing outbreaks and/ or ongoing transmission of the disease. The RIVM also monitors potential threats to public health from new (worldwide) respiratory infections. In May 2014, the first two cases of MERS coronavirus were diagnosed in the Netherlands. During the 2013/2014 influenza-season, the number of patients with influenza-like illness (ILI) consulting a general practitioner, was above the threshold set for an influenza epidemic for four weeks at the beginning of 2014. In nose and throat samples of ILI-patients, RSV (respiratory syncytial virus) and rhinovirus were found in addition to the influenza virus. During the 2013/2014 influenza-season, fewer patients consulted the general practitioner for pneumonia than in previous years, however the number of pneumonia patients in nursing homes was similar.Ministerie van VW

Enhanced Nogo-P3 amplitudes of mothers compared with non-mother women during an emotional Go/Nogo task

Background: It is known that emotion regulatory responses of humans are changed by the experiences they have, but in particular, they are changed by becoming a mother. A recent study has found how a woman&apos;s emotion regulatory response to a child&apos;s crying changes after becoming a mother. However, mothers&apos; emotion regulatory responses other than those to children and the association between emotion regulatory response and parental stress are still unknown. Methods: Eighteen healthy Japanese females (nine mothers and nine non-mothers) participated in the experiment. They performed an emotional Go/Nogo task, with facial expressions of others (angry, happy, and neutral faces) used as emotional stimuli. The percentage of correct responses, response time, and event-related potentials (ERPs) during the task was measured. Results: This comparison revealed that the mother group had a larger P3 (Nogo-P3) amplitude than the non-mother group when Nogo trials were held. This indicates that in mothers, there was greater activation of the behavioral inhibition-related brain areas than in non-mother women when they inhibited inappropriate behavior following recognition of facial expressions of others. In addition, in the mother group, there was a negative correlation between parental stress levels and Nogo-P3 amplitudes evoked by angry faces. This suggests that there is a relation between the level of parental stress of mothers and their emotion regulatory responses to angry faces. Conclusions: Our results demonstrate that mothers&apos; emotion regulatory processes may differ from those of non-mothers in response, not only to a child&apos;s crying but also to expressions of emotions by others, and also suggest that the inhibitory recognition activity of mothers can be affected by parental stres

Neural correlates of sexual cue reactivity in individuals with and without compulsive sexual behaviours

Although compulsive sexual behaviour (CSB) has been conceptualized as a "behavioural" addiction and common or overlapping neural circuits may govern the processing of natural and drug rewards, little is known regarding the responses to sexually explicit materials in individuals with and without CSB. Here, the processing of cues of varying sexual content was assessed in individuals with and without CSB, focusing on neural regions identified in prior studies of drug-cue reactivity. 19 CSB subjects and 19 healthy volunteers were assessed using functional MRI comparing sexually explicit videos with non-sexual exciting videos. Ratings of sexual desire and liking were obtained. Relative to healthy volunteers, CSB subjects had greater desire but similar liking scores in response to the sexually explicit videos. Exposure to sexually explicit cues in CSB compared to non-CSB subjects was associated with activation of the dorsal anterior cingulate, ventral striatum and amygdala. Functional connectivity of the dorsal anterior cingulate-ventral striatum-amygdala network was associated with subjective sexual desire (but not liking) to a greater degree in CSB relative to non-CSB subjects. The dissociation between desire or wanting and liking is consistent with theories of incentive motivation underlying CSB as in drug addictions. Neural differences in the processing of sexual-cue reactivity were identified in CSB subjects in regions previously implicated in drug-cue reactivity studies. The greater engagement of corticostriatal limbic circuitry in CSB following exposure to sexual cues suggests neural mechanisms underlying CSB and potential biological targets for interventions

Hypertension persisting after pre-eclampsia: a prospective cohort study at Mulago Hospital, Uganda.

BACKGROUND: Pre-eclampsia/eclampsia usually resolves after delivery but sometimes hypertension persists and cardiovascular disease develops later. Our objective was to determine the incidence and maternal socio-demographic and obstetric risk factors for persistence of hypertension in women with pre-eclampsia/eclampsia. METHODS: This was a prospective cohort study conducted from July 2009 to June 2011 at Mulago Hospital labour ward and postnatal clinics. We followed up 188 women admitted with pre-eclampsia/eclampsia until 3 months after delivery. Data was collected using interviewer-administered questionnaires, examination of participants and review of medical records. Stata (version12) software was used for data analysis. Univariable analysis was used to compute the relative risk of persistent hypertension at the 95% confidence level. This was followed by multivariable logistic regression analysis to determine factors independently associated with persistence of hypertension. RESULTS: 64 (34%) out of the 188 women analysed had persistent hypertension three months after delivery. Maternal age, gestational age at delivery and parity were predictors of persistent hypertension. CONCLUSION: The proportion of women with pre-eclampsia/eclampsia at risk of persistent hypertension at three months after delivery was high, with nearly one of three mothers remaining hypertensive. Follow up of mothers who develop pre-eclampsia is important so that early diagnosis and management of chronic hypertension can be made to avoid long term morbidity and mortality