Silent White Light

We investigate the intra-waveguide statistics manipulation of broadband light by combining semiconductor quantum dot physics with quantum optics. By cooling a quantum dot superluminescent diode to liquid nitrogen temperature of $77K$, Blazek et al. [Phys. Rev. A 84, 63840 (2011)] have demonstrated a temperature-dependent reduction of the second-order intensity correlation coefficient from two for thermal amplified spontaneous emission light to $g^{(2)}(T=190 K)\approx 1.33$. Here, we model the broadband photon statistics assuming amplified spontaneous emission radiation in a pumped, saturable quantum dot gain medium. We demonstrate that, by an intensity increase due to the quantum dot occupation dynamics via the temperature-tuned quasi Fermi levels, together with the saturation nonlinearity, a statistics manipulation from thermal Bose-Einstein statistics towards Poissonian statistics can be realized, thus producing "silent white light". Such intensity-noise reduced broadband radiation is relevant for many applications like optical coherence tomography, optical communication or optical tweezers

Histone Ubiquitination by the DNA Damage Response Is Required for Efficient DNA Replication in Unperturbed S Phase

Chromatin ubiquitination by the ubiquitin ligase RNF168 is critical to regulate the DNA damage response (DDR). DDR deficiencies lead to cancer-prone syndromes, but whether this reflects DNA repair defects is still elusive. We identified key factors of the RNF168 pathway as essential mediators of efficient DNA replication in unperturbed S phase. We found that loss of RNF168 leads to reduced replication fork progression and to reversed fork accumulation, particularly evident at repetitive sequences stalling replication. Slow fork progression depends on MRE11-dependent degradation of reversed forks, implicating RNF168 in reversed fork protection and restart. Consistent with regular nucleosomal organization of reversed forks, the replication function of RNF168 requires H2A ubiquitination. As this novel function is shared with the key DDR players ATM, γH2A.X, RNF8, and 53BP1, we propose that double-stranded ends at reversed forks engage classical DDR factors, suggesting an alternative function of this pathway in preventing genome instability and human disease

Emission spectrum of broadband quantum dot superluminescent diodes

We present a microscopic theory of the amplified spontaneous emission of a spectrally broadband quantum dot superluminescent diode within the quantum white noise limit. From this multimode quantum theory, we have the ability to obtain all orders of temporal correlation functions. In particular, we derive rate equations for the optical power densities, the level occupation of inhomogeneous ensemble of quantum dots within the diode, as well as the emitted optical spectra. As the main result, we find the external power spectrum as a convolution of the intra-diode photon spectrum with a Lorentzian response. Assuming a Gaussian light-matter coupling results in a similar shaped Gaussian output spectrum, which agrees very well with available experimental data

Intention Retrieval and Deactivation Following an Acute Psychosocial Stressor

We often form intentions but have to postpone them until the appropriate situation for retrieval and execution has come, an ability also referred to as event-based prospective memory. After intention completion, our cognitive system has to deactivate no-more-relevant intention representations from memory to avoid interference with subsequent tasks. In everyday life, we frequently rely on these abilities also in stressful situations. Surprisingly, little is known about potential stress effects on these functions. Therefore, the present study aimed to examine the reliability of event-based prospective memory and of intention deactivation in conditions of acute psychosocial stress. To this aim, eighty-two participants underwent the Trier Social Stress Test, a standardized stress protocol, or a standardized control situation. Following this treatment, participants performed a computerized event-based prospective memory task with non-salient and focal prospective memory cues in order to assess prospective memory performance and deactivation of completed intentions. Although the stress group showed elevated levels of salivary cortisol as marker of a stress-related increase in hypothalamus-pituitary-adrenal axis activity throughout the cognitive testing period compared to the no-stress group, prospective memory performance and deactivation of completed intentions did not differ between groups. Findings indicate that cognitive control processes subserving intention retrieval and deactivation after completion may be mostly preserved even under conditions of acute stress

Interferon-stimulated gene 15 accelerates replication fork progression inducing chromosomal breakage

DNA replication is highly regulated by the ubiquitin system, which plays key roles upon stress. The ubiquitin-like modifier ISG15 (interferon-stimulated gene 15) is induced by interferons, bacterial and viral infection, and DNA damage, but it is also constitutively expressed in many types of cancer, although its role in tumorigenesis is still largely elusive. Here, we show that ISG15 localizes at the replication forks, in complex with PCNA and the nascent DNA, where it regulates DNA synthesis. Indeed, high levels of ISG15, intrinsic or induced by interferon-β, accelerate DNA replication fork progression, resulting in extensive DNA damage and chromosomal aberrations. This effect is largely independent of ISG15 conjugation and relies on ISG15 functional interaction with the DNA helicase RECQ1, which promotes restart of stalled replication forks. Additionally, elevated ISG15 levels sensitize cells to cancer chemotherapeutic treatments. We propose that ISG15 up-regulation exposes cells to replication stress, impacting genome stability and response to genotoxic drugs

Die Prävalenz von EHV-2 und EHV-5 bei Pferden mit Keratokonjunktivitis und augengesunden Pferden in der Schweiz

Not all viral keratoconjunctivitis can be detected by PCR as caused by EHV-2 and 5. The authors therefore compared the prevalence of EHV-2 and 5 by PCR in horses with keratoconjunctivitis and healthy horses. Conjunctival cytobrush samples of 131 horses with suspected viral keratoconjunctivitis between 2001 and 2010 and of 163 healthy horses from three different stables were tested by PCR for the pre- sence of EHV-2 and EHV-5. The prevalence of EHV-2 and 5 is not significantly different in healthy horses and horses with keratoconjunc- tivitis. No specific ophthalmic signs could be attributed to either EVH-2 or EHV-5. The punctate pattern on the corneal surface, which is considered typical for a viral keratitis, was found in horses infected with EHV-2 or EHV-5. It appears, that an EHV-5-infection causes only mild clinical signs compared to horses testing positive for EHV-2. The most severe clinical signs were seen in horse testing positive for EHV- 2 and 5. In this investigation the prevalence of EHV-2 and EHV-5 was similar in healthy horses and horses with keratoconjunctivitis. No sta- tistically significant differences were found. The pathogenicity of EHV-2 and 5 is not clear or very weak

Silent White Light

We investigate the intra-waveguide statistics manipulation of broadband light by combining semiconductor quantum dot physics with quantum optics. By cooling a quantum dot superluminescent diode to liquid nitrogen temperature of $77K$, Blazek et al. [Phys. Rev. A 84, 63840 (2011)] have demonstrated a temperature-dependent reduction of the second-order intensity correlation coefficient from two for thermal amplified spontaneous emission light to $g^{(2)}(T=190 K)\approx 1.33$. Here, we model the broadband photon statistics assuming amplified spontaneous emission radiation in a pumped, saturable quantum dot gain medium. We demonstrate that, by an intensity increase due to the quantum dot occupation dynamics via the temperature-tuned quasi Fermi levels, together with the saturation nonlinearity, a statistics manipulation from thermal Bose-Einstein statistics towards Poissonian statistics can be realized, thus producing "silent white light". Such intensity-noise reduced broadband radiation is relevant for many applications like optical coherence tomography, optical communication or optical tweezers

Neuroendocrine measures.

<p>Mean salivary α-amylase (sAA) and cortisol levels for the stress group and the no-stress group over the time-course of the experimental session (minutes before or after the Trier Social Stress Test [TSST] or the control condition, respectively). Error bars represent standard errors. *<i>p</i> < .05, **<i>p</i> < .01, ***<i>p</i> < .001.</p

Cognitive performance.

<p>Mean response time (RT) and mean error rates for the Prospective memory (PM) block and the Test block as a function of trial type (PM block: standard vs. PM; Test block: standard vs. PM_REPEATED) and treatment (stress vs. no stress). Error bars represent standard errors. </p