93 research outputs found
Four-wave mixing enhanced white-light cavity
We discuss in-medium propagation dynamics in a white light cavity that leads
to an enhancement of the cavity's bandwidth without reducing its maximum
intensity buildup. We analyze the spatiotemporal dynamics of our system with a
full simulation of the field propagation in a regime that leads to strong
absorption of the control fields. We find that an additional coherent field is
generated within the medium via four-wave mixing. This self-generated field
leads to a backaction of the medium onto the probe field. Counter intuitively,
this pronounced in-medium dynamics throughout the propagation leads to an
additional enhancement of the cavity bandwidth.Comment: 5 pages, 4 figure
Group velocity control in the ultraviolet domain via interacting dark-state resonances
The propagation of a weak probe field in a laser-driven four-level atomic
system is investigated. We choose mercury as our model system, where the probe
transition is in the ultraviolet region. A high-resolution peak appears in the
optical spectra due to the presence of interacting dark resonances. We show
that this narrow peak leads to superluminal light propagation with strong
absorption, and thus by itself is only of limited interest. But if in addition
a weak incoherent pump field is applied to the probe transition, then the peak
structure can be changed such that both sub- and superluminal light propagation
or a negative group velocity can be achieved without absorption, controlled by
the incoherent pumping strength
Nonlinear Effects in Pulse Propagation through Doppler-Broadened Closed-Loop Atomic Media
Nonlinear effects in pulse propagation through a medium consisting of
four-level double--type systems are studied theoretically. We apply
three continous-wave driving fields and a pulsed probe field such that they
form a closed interaction loop. Due to the closed loop and the finite frequency
width of the probe pulses the multiphoton resonance condition cannot be
fulfilled, such that a time-dependent analysis is required. By identifying the
different underlying physical processes we determine the parts of the solution
relevant to calculate the linear and nonlinear response of the system. We find
that the system can exhibit a strong intensity dependent refractive index with
small absorption over a range of several natural linewidths. For a realistic
example we include Doppler and pressure broadening and calculate the nonlinear
selfphase modulation in a gas cell with Sodium vapor and Argon buffer gas. We
find that a selfphase modulation of is achieved after a propagation of
few centimeters through the medium while the absorption in the corresponding
spectral range is small.Comment: 4 figure
Early detection and intervention of psychosis in children and adolescents: urgent need for studies
Seasonal variation of BMI at admission in German adolescents with anorexia nervosa
Objective
Recent preliminary studies indicated a seasonal association of BMI at admission to inpatient treatment for anorexia nervosa (AN), indicating lower BMI in the cold season for restrictive AN. An impaired thermoregulation was proposed as the causal factor, based on findings in animal models of AN. However, findings regarding seasonality of BMI and physical activity levels in the general population indicate lower BMI and higher physical activity in summer than in winter. Therefore, we aimed to thoroughly replicate the findings regarding seasonality of BMI at admission in patients with AN in this study.
Method
AN subtype, age- and gender-standardized BMI scores (BMI-SDS) at admission, mean daily sunshine duration and ambient temperature at the residency of 304 adolescent inpatients with AN of the multi-center German AN registry were analyzed.
Results
A main effect of DSM-5 AN subtype was found (F(2,298) = 6.630, p = .002), indicating differences in BMI-SDS at admission between restrictive, binge/purge and subclinical AN. No main effect of season on BMI-SDS at admission was found (F(1,298) = 4.723, p = .025), but an interaction effect of DSM-5 subtype and season was obtained (F(2,298) = 6.625, p = .001). Post-hoc group analyses revealed a lower BMI-SDS in the warm season for restrictive AN with a non-significant small effect size (t(203.16) = 2.140, p = .033; Hedges′g = 0.28). Small correlations of mean ambient temperature (r = −.16) and daily sunshine duration (r = −.22) with BMI-SDS in restrictive AN were found. However, the data were widely scattered.
Conclusions
Our findings are contrary to previous studies and question the thermoregulatory hypothesis, indicating that seasonality in AN is more complex and might be subject to other biological or psychological factors, for example physical activity or body dissatisfaction. Our results indicate only a small clinical relevance of seasonal associations of BMI-SDS merely at admission. Longitudinal studies investigating within-subject seasonal changes might be more promising to assess seasonality in AN and of higher clinical relevance
The psychopathological and psychosocial outcome of early-onset schizophrenia: Preliminary data of a 13-year follow-up
<p>Abstract</p> <p>Background</p> <p>Relatively little is known about the long-term psychopathological and psychosocial outcome of early-onset schizophrenia. The existing literature describes more severe courses of illness in these patients compared with adult-onset schizophrenia. This article reports preliminary data of a study exploring the outcome of early-onset schizophrenia 13.4 years (mean) after first admission. Predictors for interindividual outcomes were investigated.</p> <p>Methods</p> <p>We retrospectively assessed 27 former patients (mean age at first admission 15.5 years, SD = 2.0) that were consecutively admitted to the Department of Child and Adolescent Psychiatry at the University of Wuerzburg between 1990 and 2000. A multidimensional approach was chosen to assess the outcome consisting of a mail survey including different questions about psychopathological symptoms, psychosocial parameters, and standardized self-reports (ESI and ADS).</p> <p>Results</p> <p>Concerning the psychopathological outcome, 22.2% reported having acute schizophrenic symptoms. Almost one third (30.8%) described symptoms of depression and 37.0% reported having tried to commit suicide or seriously thought about it. 77.8% of the former patients were still in outpatient treatment. Compared to the general population, the number of patients without a school graduation was relatively high (18.5%). Almost half of participants still live with their parents (48.1%) or in assisted or semi-assisted living conditions (33.3%). Only 18.5% were working in the open market.</p> <p>Conclusion</p> <p>Schizophrenia with an early onset has an unfavourable prognosis. Our retrospective study of the psychopathological and psychosocial outcome concludes with a generally poor rating.</p
Photonic hydrogel sensors
Analyte-sensitive hydrogels that incorporate optical structures have emerged as sensing platforms for point-of-care diagnostics. The optical properties of the hydrogel sensors can be rationally designed and fabricated through self-assembly, microfabrication or laser writing. The advantages of photonic hydrogel sensors over conventional assay formats include label-free, quantitative, reusable, and continuous measurement capability that can be integrated with equipment-free text or image display. This Review explains the operation principles of photonic hydrogel sensors, presents syntheses of stimuli-responsive polymers, and provides an overview of qualitative and quantitative readout technologies. Applications in clinical samples are discussed, and potential future directions are identified
Semi-crystalline diblock copolymer nano-objects prepared via RAFT alcoholic dispersion polymerization of stearyl methacrylate
The RAFT dispersion polymerization of stearyl methacrylate (SMA) is conducted in ethanol at 70 °C using a poly(2-(dimethylamino)ethyl methacrylate) [PDMA] chain transfer agent. The growing PSMA block becomes insoluble in ethanol, which leads to polymerization-induced self-assembly (PISA) and hence produces a range of copolymer morphologies depending on the precise PDMAy–PSMAx formulation. More specifically, pure phases corresponding to either spherical nanoparticles, worm-like nanoparticles or vesicles can be prepared as judged by transmission electron microscopy. However, the worm phase space is relatively narrow, so construction of a detailed phase diagram is required for reproducible syntheses of this morphology. Inter-digitation of the stearyl (C18) side-groups leads to a semi-crystalline PSMA core block and the effect of systematically varying the mean degree of polymerization of both the PDMA and PSMA blocks on the Tm and Tc is investigated using differential scanning calorimetry. Finally, it is demonstrated that these cationic nanoparticles can be employed as colloidal templates for the in situ deposition of silica from aqueous solution
Pharmacological treatments prescribed to people with autism spectrum disorder (ASD) in primary health care
- …