Functional nuclear organization of transcription and DNA replication: a topographical marriage between chromatin domains and the interchromatin compartment

We studied the nuclear topography of RNA transcription and DNA replication in mammalian cell types with super-resolution fluorescence microscopy, which offers a resolution beyond the classical Abbe/Raleigh limit. Three-dimensional structured illumination microscopy (3D-SIM) demonstrated a network of channels and wider lacunas, called the interchromatin compartment (IC). The IC starts at nuclear pores and expands throughout the nuclear space. It is demarcated from the compact interior of higher-order chromatin domains (CDs) by a 100-200-nm thick layer of decondensed chromatin, termed the perichromatin region (PR). Nascent DNA, nascent RNA, RNA polymerase II (RNA Pol II), as well as histone modifications for transcriptionally competent/active chromatin, are highly enriched in the PR, whereas splicing speckles are observed in the interior of the IC. In line with previous electron microscopic evidence, spectral precision distance/position determination microscopy (SPDM) confirmed the presence of RNA Pol II clusters indicative of transcription factories. Still, a substantial part of transcription apparently takes place outside of such factories. Previous electron microscopic evidence has suggested that the functional nuclear organization of DNA replication depends on brownian movements of chromatin between the CD interior and the PR. As an incentive for future studies, we hypothesize that such movements also take place during transcription, i.e., only the actually transcribed part of a gene may be located within the PR, whereas its major part, including previously or later transcribed sequences, is embedded in a higher-order chromatin configuration in the interior of the CD.

Calling 911 in Response to Stroke: No Change following a Four-Year Educational Campaign

<i>Background:</i> Public awareness campaigns are conducted to increase stroke awareness, yet evidence of their long-term effectiveness is limited. Since 2006, the Czech Stroke Society has conducted an educational campaign throughout the Czech Republic (CR) to increase awareness about stroke. This report evaluates the effectiveness of this campaign by comparing the results of a nationwide survey on stroke awareness in 2009 with the results from 2005. <i>Methods:</i> In 2009, a nationwide survey was conducted throughout the CR using the same methodology as in 2005 and employing a 3-stage random sampling method (area, household, and household member sampling). Participants >40 years of age were personally interviewed via a structured questionnaire concerning their knowledge and ability to correctly respond to stroke as assessed by the validated Stroke Action Test (STAT). The primary outcome measure was the difference in a STAT score >50% (i.e. respondents chose to call 911 for >50% of stroke symptoms) between 2005 and 2009. Campaign intensity was characterized by a systematic search for media messages about stroke in the CR. <i>Results:</i> A total of 601 interviews were obtained (90% response rate) in 2009 (592 people were interviewed in 2005). A STAT score >50% was achieved by 18% of the respondents both in 2005 and 2009 (p = 0.89). There was no increase in the knowledge of risk factors or warning signs between 2005 and 2009. Respondents who noticed the campaign (19%) had better STAT scores than respondents who did not (25 vs. 17%; p = 0.038). A systematic search revealed that the campaign had reasonable intensity because there were 978 media reports about stroke between 2006 and 2008. <i>Conclusions:</i> A medium-intensity educational campaign, based on donated advertising media, failed to increase stroke awareness. However, if the campaign had reached more people, it might have been effective. Therefore, in the future, paid advertising media should accompany free media, although such approach would require a substantially larger budget. Awareness campaigns should be constantly evaluated for their effectiveness to develop more successful strategies.

Ultrafast double-slab regenerative amplifier with combined gain spectra and intracavity dispersion compensation

We report on a diode-pumped double-slab Yb:KYW regenerative amplifier with combined gain spectra and intracavity dispersion compensation. At repetition rates > 20 kHz an average power of up to 5 W after compression was generated, resulting in a maximum pulse energy of 250 µJ. Pulse durations of around 190 fs were achieved by using a GRISM compressor with a transmission efficiency of 90%.

Transport, separation, and accumulation of proteins on supported lipid bilayers

Transport, separation, and accumulation of proteins in their natural environment are central goals in protein biotechnology. Miniaturized assays of supported lipid bilayers (SLBs) have been proposed as promising candidates to realize such technology on a chip, but a modular system for the controlled transport of membrane proteins does not exist. In this letter, we demonstrate that standing surface acoustic waves drive the in-plane redistribution of proteins on planar SLBs over macroscopic distances (3.5 mm). Accumulation of proteins in periodic patterns of about 10-fold protein concentration difference is accomplished and shown to relax into the homogeneous state by diffusion. Different proteins separate in individual fractions from a homogeneous distribution and are transported and accumulated into clusters using beats. The modular planar setup has the potential of integrating other lab-on-a-chip tools, for monitoring the membrane-protein integrity or adding microfluidic features for blood screening or DNA analysis.

Quantum-limited noise performance of a femtosecond all-fiber ytterbium laser

We report on quantum-limited noise performance of a mode-locked ytterbium all-fiber laser. The laser operates at a high normal net dispersion without dispersion compensation. We show that the naïve application of analytical models to such lasers leads to strongly underestimated timing jitter, whereas a numerical simulation is in reasonable agreement with measurements. The measured timing phase noise is found to be essentially limited by quantum noise influences and not by technical noise. Furthermore we show that the phase noise of different comb lines has a quasi-fix point at the center of the optical spectrum and that the jitter is translated into high carrier-envelope offset phase noise with a linewidth of around 3 MHz.

Ultrafast high power Yb:KLuW regenerative amplifier

We report on an high power ultra-short pulse regenerative Yb:KLuW amplifier based on the thin disk concept. A maximum pulse energy of 571 microJ was extracted at a repetition rate of 20 kHz. Compression of the output pulses resulted in a pulse duration of 197 fs assuming a deconvolution factor of 2.16. At a repetition rate of 125 kHz a maximum average power of 17.9 W was measured in front of the compressor.

Sub-100 fs pulses from a low repetition rate Yb-doped fiber laser

We report on a passively mode-locked ytterbium-doped fiber laser with a repetition rate of 1.8 MHz. The laser was hybridly mode-locked via nonlinear polarization evolution and a semiconductor saturable absorber mirror. It generated chirped 3.8 ps long pulses with a pulse energy of 1.0 nJ which could be dechirped to a pulse duration of 93 fs.