Field-Induced Rocking-Curve Effects in Attosecond Electron Diffraction.

Recent advances in electron microscopy trigger the question of whether attosecond electron diffraction can resolve atomic-scale electron dynamics in crystalline materials in space and time. Here, we explore the ultrafast dynamics of the relevant electron-lattice scattering process. We drive a single-crystalline silicon membrane with the optical cycles of near-infrared laser light and use phase-locked attosecond electron pulses to produce electron diffraction patterns as a function of delay. For all Bragg spots, we observe time-dependent intensity changes and position shifts that are correlated with a time shift of 0.5-1.2 fs. For single-cycle excitation pulses with strong peak intensity, the correlations become nonlinear. The origins of these effects are local and integrated beam deflections by the optical electric and magnetic fields at the crystal membrane. Those deflections modify the diffraction intensities in addition to the atomic structure factor dynamics by time-dependent rocking-curve effects. However, the measured time delays and symmetries allow one to disentangle both effects. Future attosecond electron diffraction and microscopy experiments need to be based on these results.

Polarized phonons carry angular momentum in ultrafast demagnetization.

Magnetic phenomena are ubiquitous in nature and indispensable for modern science and technology, but it is notoriously difficult to change the magnetic order of a material in a rapid way. However, if a thin nickel film is subjected to ultrashort laser pulses, it loses its magnetic order almost completely within femtosecond timescales1. This phenomenon is widespread2-7 and offers opportunities for rapid information processing8-11 or ultrafast spintronics at frequencies approaching those of light8,9,12. Consequently, the physics of ultrafast demagnetization is central to modern materials research1-7,13-28, but a crucial question has remained elusive: if a material loses its magnetization within mere femtoseconds, where is the missing angular momentum in such a short time? Here we use ultrafast electron diffraction to reveal in nickel an almost instantaneous, long-lasting, non-equilibrium population of anisotropic high-frequency phonons that appear within 150-750 fs. The anisotropy plane is perpendicular to the direction of the initial magnetization and the atomic oscillation amplitude is 2 pm. We explain these observations by means of circularly polarized phonons that quickly absorb the angular momentum of the spin system before macroscopic sample rotation. The time that is needed for demagnetization is related to the time it takes to accelerate the atoms. These results provide an atomistic picture of the Einstein-de Haas effect and signify the general importance of polarized phonons for non-equilibrium dynamics and phase transitions.

Measurement of Temporal Coherence of Free Electrons by Time-Domain Electron Interferometry.

The temporal properties of an electron beam are decisive for modern ultrafast electron microscopy and for the quantum optics of the free electron in laser fields. Here, we report a time-domain interferometer that measures and distinguishes the pure and ensemble coherences of a free-electron beam in a transmission electron microscope via symmetry-breaking shifts of photon-order sideband peaks. This result is a free-electron analog to the reconstruction of attosecond busts and photoemission delays in optical attosecond spectroscopy. We find a substantial pure electron coherence that is connected to the thermodynamics of the emitter material and a lower ensemble coherence that is governed by space-charge effects. Pure temporal coherences above 5 fs are measured at >10^{9} electrons per second in a high-brightness beam.

Jitter-free terahertz pulses from LiNbO3.

Intense terahertz pulses are indispensable for modern science and technology, but time-critical applications require ultimate stability of the field cycles with respect to a reference clock. Here we report the nonlinear optical generation of terahertz single-cycle fields by femtosecond laser pulses under passive compensation of timing jitter. The converter is based on optical rectification in a LiNbO3 slab with two silicon prisms for extracting and combining the emitted Cherenkov radiation from both sides into a single beam. In this way, we achieve suppression of timing jitter to <200 as/µm of beam displacement, a factor of >70 better than in conventional non-collinear geometries.

Hospital volume following major surgery for gastric cancer determines in-hospital mortality rate and failure to rescue: a nation-wide study based on German billing data (2009-2017).

BACKGROUND: For many cancer resections, a hospital volume-outcome relationship exists. The data regarding gastric cancer resection-especially in the western hemisphere-are ambiguous. This study analyzes the impact of gastric cancer surgery caseload per hospital on postoperative mortality and failure to rescue in Germany. METHODS: All patients diagnosed with gastric cancer from 2009 to 2017 who underwent gastric resection were identified from nation-wide administrative data. Hospitals were grouped into five equal caseload quintiles (I-V in ascending caseload order). Postoperative deaths and failure to rescue were determined. RESULTS: Forty-six thousand one hundred eighty-seven patients were identified. There was a significant shift from partial resections in low-volume hospitals to more extended resections in high-volume centers. The overall in-house mortality rate was 6.2%. The crude in-hospital mortality rate ranged from 7.9% in quintile I to 4.4% in quintile V, with a significant trend between volume categories (p < 0.001). In the multivariable logistic regression analysis, quintile V hospitals (average of 29 interventions/year) had a risk-adjusted odds ratio of 0.50 (95% CI 0.39-0.65), compared to the baseline in-house mortality rate in quintile I (on average 1.5 interventions/year) (p < 0.001). In an analysis only evaluating hospitals with more than 30 resections per year mortality dropped below 4%. The overall postoperative complication rate was comparable between different volume quintiles, but failure to rescue (FtR) decreased significantly with increasing caseload. CONCLUSION: Patients who had gastric cancer surgery in hospitals with higher volume had better outcomes and a reduced failure to rescue rates for severe complications.

Attosecond metrology in a continuous-beam transmission electron microscope.

Electron microscopy can visualize the structure of complex materials with atomic and subatomic resolution, but investigations of reaction dynamics and light-matter interaction call for time resolution as well, ideally on a level below the oscillation period of light. Here, we report the use of the optical cycles of a continuous-wave laser to bunch the electron beam inside a transmission electron microscope into electron pulses that are shorter than half a cycle of light. The pulses arrive at the target at almost the full average brightness of the electron source and in synchrony to the optical cycles, providing attosecond time resolution of spectroscopic features. The necessary modifications are simple and can turn almost any electron microscope into an attosecond instrument that may be useful for visualizing the inner workings of light-matter interaction on the basis of the atoms and the cycles of light.

Ultrafast electron diffraction from nanophotonic waveforms via dynamical Aharonov-Bohm phases.

Electron interferometry via phase-contrast microscopy, holography, or picodiffraction can provide a direct visualization of the static electric and magnetic fields inside or around a material at subatomic precision, but understanding the electromagnetic origin of light-matter interaction requires time resolution as well. Here, we demonstrate that pump-probe electron diffraction with all-optically compressed electron pulses can capture dynamic electromagnetic potentials in a nanophotonic material with sub-light-cycle time resolution via centrosymmetry-violating Bragg spot dynamics. The origin of this effect is a sizable quantum mechanical phase shift that the electron de Broglie wave obtains from the oscillating electromagnetic potentials within less than 1 fs. Coherent electron imaging and scattering can therefore reveal the electromagnetic foundations of light-matter interaction on the level of the cycles of light.

Nationwide in-hospital mortality rate following rectal resection for rectal cancer according to annual hospital volume in Germany.

BACKGROUND: The impact of hospital volume after rectal cancer surgery is seldom investigated. This study aimed to analyse the impact of annual rectal cancer surgery cases per hospital on postoperative mortality and failure to rescue. METHODS: All patients diagnosed with rectal cancer and who had a rectal resection procedure code from 2012 to 2015 were identified from nationwide administrative hospital data. Hospitals were grouped into five quintiles according to caseload. The absolute number of patients, postoperative deaths and failure to rescue (defined as in-hospital mortality after a documented postoperative complication) for severe postoperative complications were determined. RESULTS: Some 64 349 patients were identified. The overall in-house mortality rate was 3·9 per cent. The crude in-hospital mortality rate ranged from 5·3 per cent in very low-volume hospitals to 2·6 per cent in very high-volume centres, with a distinct trend between volume categories (P < 0·001). In multivariable logistic regression analysis using hospital volume as random effect, very high-volume hospitals (53 interventions/year) had a risk-adjusted odds ratio of 0·58 (95 per cent c.i. 0·47 to 0·73), compared with the baseline in-house mortality rate in very low-volume hospitals (6 interventions per year) (P < 0·001). The overall postoperative complication rate was comparable between different volume quintiles, but failure to rescue decreased significantly with increasing caseload (15·6 per cent after pulmonary embolism in the highest volume quintile versus 38 per cent in the lowest quintile; P = 0·010). CONCLUSION: Patients who had rectal cancer surgery in high-volume hospitals showed better outcomes and reduced failure to rescue rates for severe complications than those treated in low-volume hospitals.

ANTECEDENTES: El impacto del volumen hospitalario en los resultados de la cirugía del cáncer de recto ha sido poco investigado. Este estudio tuvo como objetivo analizar el impacto de los casos anuales de cirugía de cáncer de recto por hospital en la mortalidad postoperatoria (postoperative mortality, POM) y el fracaso en el rescate (failure to rescue, FtR). MÉTODOS: Todos los casos de pacientes hospitalizados con un diagnóstico de cáncer de recto y un código de procedimiento de resección rectal, tratados de 2012 a 2015, se identificaron a partir de datos hospitalarios administrativos a nivel nacional. Los hospitales se agruparon en cinco quintiles según el volumen de casos. Se determinó el número absoluto de pacientes, la POM y el FtR por complicaciones postoperatorias graves. El FtR se definió como la mortalidad hospitalaria después de una complicación postoperatoria documentada. RESULTADOS: Se identificaron 64.349 casos entre 2012 y 2015. La tasa de mortalidad hospitalaria global fue del 3,89% (n = 2.506). Las tasas brutas de mortalidad hospitalaria variaron de 5,34% (n = 687) en hospitales de muy bajo volumen a 2,63% (n = 337) en centros de muy alto volumen, con una tendencia distinta entre las categorías de centros (P < 0,001). En el análisis de regresión logística multivariante utilizando el volumen hospitalario como efecto aleatorio, los hospitales de muy alto volumen (53 intervenciones/año) tenían una razón de oportunidades (odds ratio, OR) ajustada por riesgo de 0,58 (i.c. del 95%: 0,47-0,73) en comparación con la tasa basal de mortalidad hospitalaria en hospitales de muy bajo volumen (6 intervenciones/año) (P < 0,001). La tasa global de complicaciones postoperatorias fue comparable entre los diferentes quintiles de volumen, pero el FtR disminuyó significativamente con el aumento del volumen de casos (15,63% FtR tras una embolia pulmonar en el quintil más alto versus 38,4% en el hospital del quintil más bajo, P = 0,01). CONCLUSIÓN: Los pacientes sometidos a cirugía de cáncer de recto en hospitales de gran volumen presentaron mejores resultados y una disminución de las tasas de fracaso en el rescate por complicaciones graves en comparación con los pacientes tratados en hospitales de bajo volumen.

Nationwide in-hospital mortality following colonic cancer resection according to hospital volume in Germany.

Background: Colonic cancer is the most common cancer of the gastrointestinal tract. The aim of this study was to determine mortality rates following colonic cancer resection and the effect of hospital caseload on in-hospital mortality in Germany. Methods: Patients admitted with a diagnosis of colonic cancer undergoing colonic resection from 2012 to 2015 were identified from a nationwide registry using procedure codes. The outcome measure was in-hospital mortality. Hospitals were ranked according to their caseload for colonic cancer resection, and patients were categorized into five subgroups on the basis of hospital volume. Results: Some 129 196 colonic cancer resections were reviewed. The overall in-house mortality rate was 5·8 per cent, ranging from 6·9 per cent (1775 of 25 657 patients) in very low-volume hospitals to 4·8 per cent (1239 of 25 825) in very high-volume centres (P < 0·001). In multivariable logistic regression analysis the risk-adjusted odds ratio for in-house mortality was 0·75 (95 per cent c.i. 0·66 to 0·84) in very high-volume hospitals performing a mean of 85·0 interventions per year, compared with that in very low-volume hospitals performing a mean of only 12·7 interventions annually, after adjustment for sex, age, co-morbidity, emergency procedures, prolonged mechanical ventilation and transfusion. Conclusion: In Germany, patients undergoing colonic cancer resections in high-volume hospitals had with improved outcomes compared with patients treated in low-volume hospitals.

Efficient middle-infrared generation in LiGaS2by simultaneous spectral broadening and difference-frequency generation: erratum.

In this erratum, we correct the abstract and introduction of Opt. Lett.43, 1742 (2018)OPLEDP0146-959210.1364/OL.43.001742 to not include a wrong name for the crystal.

Efficient middle-infrared generation in LiGaS2 by simultaneous spectral broadening and difference-frequency generation.

We report a surprisingly broadband and efficient midinfrared pulse generation in LiGaS2 (Langasite, LGS) by invoking a simultaneous interplay of intrapulse difference-frequency generation, self-phase modulation, and dispersion. This cascaded mechanism expands the output bandwidth and output power at the same time. With 30-fs driving pulses centered at 1030-nm wavelength we obtain a broadband middle-infrared spectrum of 8-11 µm with an LGS crystal as thick as 4 mm, which is eight times longer than the walk-off length.

Up-regulated autophagy: as a protective factor in adipose tissue of WOKW rats with metabolic syndrome.

BACKGROUND: Wistar Ottawa Karlsburg W (RT1u) rats (WOKW) are a model of the metabolic syndrome (MetS). Adipose tissue (AT) and peripheral nerves of WOKW rats exhibit up-regulated autophagy and inflammation corresponding with decreased apoptosis rate. The aim of this study was to characterize AT in WOKW rats in relation to autophagic activity. METHODS: mRNA and protein expression of adiponectin, pro-inflammatory and pro-apoptotic markers including MCP1, TNFα, cleaved caspase-3 and RNF157, a new candidate gene regulated through autophagy, were analyzed in adipocytes isolated from visceral and subcutaneous AT of 5-month old WOKW rats with MetS and LEW.1W controls in response to pharmacological inhibition of autophagy. Immunohistochemistry was performed to detect adiponectin and RNF157 protein in cultured adipocytes. RESULTS: Inhibition of autophagy by LY294002 was associated with a fourfold up-regulation of adiponectin expression and a decrease of RNF157 protein and pro-inflammatory markers-MCP-1 and TNFα predominantly in visceral adipocytes of obese WOKW rats compared to LEW.1W rats. Moreover, inhibition of autophagic activity correlates with an activation of cleaved caspase-3 apoptotic signaling pathway. CONCLUSIONS: Up-regulated autophagy in obese WOKW rats contributes to the regulation of visceral AT function and involves an altered balance between pro-inflammatory and protective adipokine expression. Our data suggest that activation of AT autophagy protects against adipocyte apoptosis at least under conditions of obesity related MetS in WOKW rats.

Electron microscopy of electromagnetic waveforms.

Rapidly changing electromagnetic fields are the basis of almost any photonic or electronic device operation. We report how electron microscopy can measure collective carrier motion and fields with subcycle and subwavelength resolution. A collimated beam of femtosecond electron pulses passes through a metamaterial resonator that is previously excited with a single-cycle electromagnetic pulse. If the probing electrons are shorter in duration than half a field cycle, then time-frozen Lorentz forces distort the images quasi-classically and with subcycle time resolution. A pump-probe sequence reveals in a movie the sample's oscillating electromagnetic field vectors with time, phase, amplitude, and polarization information. This waveform electron microscopy can be used to visualize electrodynamic phenomena in devices as small and fast as available.

All-optical control and metrology of electron pulses.

Short electron pulses are central to time-resolved atomic-scale diffraction and electron microscopy, streak cameras, and free-electron lasers. We demonstrate phase-space control and characterization of 5-picometer electron pulses using few-cycle terahertz radiation, extending concepts of microwave electron pulse compression and streaking to terahertz frequencies. Optical-field control of electron pulses provides synchronism to laser pulses and offers a temporal resolution that is ultimately limited by the rise-time of the optical fields applied. We used few-cycle waveforms carried at 0.3 terahertz to compress electron pulses by a factor of 12 with a timing stability of <4 femtoseconds (root mean square) and measure them by means of field-induced beam deflection (streaking). Scaling the concept toward multiterahertz control fields holds promise for approaching the electronic time scale in time-resolved electron diffraction and microscopy.

Sub-phonon-period compression of electron pulses for atomic diffraction.

Visualizing the rearrangement of atoms in a wide range of molecular and condensed-matter systems requires resolving picometre displacements on a 10-fs timescale, which is achievable using pump-probe diffraction, given short enough pulses. Here we demonstrate the compression of single-electron pulses with a de Broglie wavelength of 0.08 ångström to a full-width at half-maximum duration of 28 fs or equivalently 12-fs root-mean square, substantially shorter than most phonon periods and molecular normal modes. Atomic resolution diffraction from a complex organic molecule is obtained with good signal-to-noise ratio within a data acquisition period of minutes. The electron-laser timing is found to be stable within 5 fs (s.d.) over several hours, allowing pump-probe diffraction at repetitive excitation. These measurements show the feasibility of laser-pump/electron-probe scans that can resolve the fastest atomic motions relevant in reversible condensed-matter transformations and organic chemistry.

Nursing Practicum in Gynaecology and Obstetrics - Early Influence Possibilities for a Specialty.

Background: The shortage of skilled personnel is ubiquitous, basic and further training is a key aspect in the recruitment of new medical colleagues. The significance of the nursing practicum in its function as gateway to the gynaecology and obstetrics discipline is practically unexplored. Methods: In an online questionnaire, medical students in all German faculties were questioned about the practica in their courses. The questionnaire reached 9079 medical students. 149 participants in nursing practica were selectively asked to answer 140 questions. We analysed those students who could, on the basis of their experiences in nursing practica, imagine undertaking an internship (clinical elective) in gynaecology (internship yes "Iy") separately from those who could not or were still undecided (internship no "In" or, respectively, internship perhaps "Ip"). Results: Altogether 149 medical students who participated in a nursing practicum in the gynaecology discipline were selected, of these 94.9 % were female. 92 (61.7 %) of the students replied that, after their gynaecological nursing practicum, they wanted to undertake an internship in gynaecology (Iy); 39 (26.2 %) answered negatively (In) and 18 (12.1 %) were still undecided (Ip). With regard to the parameters gender, age and duration of study, there were no significant differences among the 3 groups (χ2 0.83). Besides the didactic and professional quality of the training, Iy also mentioned having had a higher practical orientation. They attained their aims more frequently, were better integrated in the health-care team and acquired more practical competences. Satisfaction with the practicum was evaluated as highest among the Iy. Discussion: Those students who could imagine taking an internship in gynaecology were seen to be more satisfied with their practica than those participants who declined or were undecided. The high proportion of females is an early indicator for a feminisation of the specialty. If necessary this could be countered with the help of nursing management.

800-fs, 330-µJ pulses from a 100-W regenerative Yb:YAG thin-disk amplifier at 300 kHz and THz generation in LiNbO3.

Yb:YAG thin-disk lasers offer extraordinary output power, but systems delivering femtosecond pulses at a repetition rate of hundreds of kilohertz are scarce, even though this regime is ideal for ultrafast electron diffraction, coincidence imaging, attosecond science, and terahertz (THz) spectroscopy. Here we describe a regenerative Yb:YAG amplifier based on thin-disk technology, producing 800-fs pulses at a repetition rate adjustable between 50 and 400 kHz. The key design elements are a short regenerative cavity and fast-switching Pockels cell. The average output power is 130 W before the compressor and 100 W after compression, which at 300 kHz corresponds to pulse energies of 430 and 330 µJ, respectively. This is sufficient for a wide range of nonlinear conversions and broadening/compression schemes. As a first application, we use optical rectification in LiNbO3 to produce 30-nJ single-cycle THz pulses with 6 W pump power. The electric field exceeds 10 kV/cm at a central frequency of 0.3 THz, suitable for driving structural dynamics or controlling electron beams.

Femtosecond single-electron diffraction.

Ultrafast electron diffraction allows the tracking of atomic motion in real time, but space charge effects within dense electron packets are a problem for temporal resolution. Here, we report on time-resolved pump-probe diffraction using femtosecond single-electron pulses that are free from intra-pulse Coulomb interactions over the entire trajectory from the source to the detector. Sufficient average electron current is achieved at repetition rates of hundreds of kHz. Thermal load on the sample is avoided by minimizing the pump-probe area and by maximizing heat diffusion. Time-resolved diffraction from fibrous graphite polycrystals reveals coherent acoustic phonons in a nanometer-thick grain ensemble with a signal-to-noise level comparable to conventional multi-electron experiments. These results demonstrate the feasibility of pump-probe diffraction in the single-electron regime, where simulations indicate compressibility of the pulses down to few-femtosecond and attosecond duration.

Increased autophagy in peripheral nerves may protect Wistar Ottawa Karlsburg W rats against neuropathy.

OBJECTIVE: Wistar Ottawa Karlsburg W (RT1(u)) rats (WOKW) develop obesity, dyslipidemia, moderate hypertension, hyperinsulinemia and impaired glucose tolerance prone to induce peripheral neuropathy (PN). Autophagy has been shown to prevent neurodegeneration in the central and peripheral nervous system. We analyzed the potential protective role of autophagy in an established rat model in preventing PN. METHODS: We examined electrophysiology (motor-and sensory/mixed afferent conduction velocities and the minimal F-wave latency) and morphology, including ultrathin sections, myelin sheath thickness (g-ratio) and immunohistochemical markers of autophagy and inflammation in the sciatic nerve of five-month-old, male WOKW as compared to Wistar derived, congenic LEW.1W control rats, characterized by the same major histocompatibility complex as WOKW rats (RT1(u)). Moreover, the expression of axonal and synaptic proteins (NF68, GAP43, MP0), autophagy- (Atg5, Atg7, LC3), and apoptosis (cleaved caspase-3)-related markers was measured using Western blot. RESULTS: No abnormalities in nerve electrophysiology and morphology were found in WOKW compared to LEW.1W rats. However, autophagosomes were more frequently apparent in sciatic nerves of WOKW rats. In Western blot analyses no significant differences in expression of neuronal structural proteins were found, but autophagy markers were up-regulated in WOKW compared to LEW.1W sciatic nerves. Immunostaining revealed a greater infiltration of Iba1/ED-1-positive macrophages, CD-3-positive T-cells and LC3-expression in sciatic nerves of WOKW rats. CONCLUSIONS: Our results indicate that WOKW rats show an up-regulated autophagy and a mild inflammatory response but do not develop overt neuropathy. We suggest that autophagy and inflammatory cells may exert a protective role in preventing neuropathy in this rat model of the metabolic syndrome but the mechanism of action is still unclear.