Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism

We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N_4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform.High-harmonic generation (HHG) results from an extreme nonlinear quantum response of atoms to intense laser fields. When implemented in a phase-matched geometry, bright, coherent HHG beams can extend to photon energies beyond 1.6 keV (1, 2). For many years, however, bright HHG was limited to linear polarization, precluding many applications in probing and characterizing magnetic materials and nanostructures, as well as chiral phenomena in general. Although X-ray optics can in principle be used to convert extreme UV (EUV) and X-ray light from linear to circular polarization, in practice such optics are challenging to fabricate and have poor throughput and limited bandwidth (3). A more appealing option is the direct generation of elliptically polarized (4–6) and circularly polarized (7–9) high harmonics. In recent work we showed that by using a combination of 0.8 and 0.4 µm counterrotating driving fields, bright (i.e., phase-matched) EUV HHG with circular polarization can be generated at wavelengths λ > 18 nm and used for EUV magnetic dichroism measurements (10–13).Here we make, to our knowledge, the first experimental demonstration of circularly polarized harmonics in the soft X-ray region to wavelengths λ < 8 nm, and use them to implement soft X-ray magnetic circular dichroism (XMCD) measurements using a tabletop-scale setup. By using counterrotating driving lasers at 0.79 µm (1.57 eV) and 1.3 µm (0.95 eV), we generate bright circularly polarized soft X-ray HHG beams with photon energies greater than 160 eV (14) and with flux comparable to the HHG flux obtained using linearly polarized 800-nm driving lasers (15). Moreover we implement, to our knowledge, the first advanced simulations of the coherent buildup of circularly polarized high harmonics to show how the macroscopic phase-matching physics and ellipticity of the driving lasers influence the HHG spectra, number of bright attosecond bursts, and the degree of circular polarization.This work presents several new capabilities and findings. First, circularly polarized HHG provides a unique route for generating bright narrowband (λ/Δλ > 400) harmonic peaks in the soft X-ray region, to complement the soft X-ray supercontinua that are produced with linearly polarized mid-IR lasers (2, 15, 16). This capability is significant because it provides an elegant and efficient route for shaping soft X-ray light by manipulating the driving laser light, and is very useful for applications in high-resolution coherent imaging (17–21) and photoelectron spectroscopies. Second, we show that the macroscopic phase-matching physics of circularly polarized soft X-ray HHG driven by mid-IR lasers has similarities to linearly polarized HHG, where the number of bright attosecond bursts is limited by the finite phase-matching temporal window. Third, we implement the first tabletop XMCD measurements at the N_4,5 absorption edges of Gd. The Gd/Fe multilayer sample is a candidate material for next-generation all-optical magnetic storage devices (22), but has been inaccessible to HHG XMCD until now. This capability also opens up the possibility of probing spin dynamics in rare-earth elements using HHG, which has been successfully used for 3d transition metals to uncover the fastest spin dynamics using EUV HHG (23, 24). Finally, and most importantly, these results demonstrate the universal nature of circularly polarized HHG that can be generated across the EUV and soft X-ray spectral regions using a broad range of driving laser wavelengths.     

The E/e filling index and right ventricular pressure in relation to applied international Doppler recommendations of left ventricular filling assessment.

AIM: A ratio>15 between the early diastolic pulsed Doppler velocities of the mitral inflow (E) and the basal left ventricular (LV) tissue (e) has been demonstrated to predict an elevated LV filling pressure (FP). An elevated LVFP implies an elevated right ventricular pressure (RVp). In order to investigate the sensitivity of the E/e filling index, we compared E/e and RVp, in their ability to identify a Doppler-assumed elevation of LVFP. METHODS AND RESULTS: Application of pulsed Doppler international recommendations grouped 134 patients with acute coronary syndromes (ACS) and 50 age- and sex-matched controls, according to LV filling: normal; delayed relaxation; an isolated pathological mitral-pulmonary venous-A-wave-duration difference; pseudo normal; or a restrictive filling pattern. An E/e>15 and an RVp>30 mmHg showed the following (%) sensitivity (32/94), specificity (95/76), positive (68/59), and negative (80/97) predictive values of a Doppler-assumed elevation of LVFP, in terms of either a pseudo normal or a restrictive filling pattern. CONCLUSION: The low sensitivity of E/e to detect a Doppler-assumed elevation of LVFP could limit its clinical usefulness as a single variable, in ACS. The high sensitivity and negative predictive value of RVp support its use as an additional LV filling variable in these patients.     

Left Bundle Branch Block in Type 2 Diabetes Mellitus: A Sign of Advanced Cardiovascular Involvement

Objective: To evaluate left bundle branch block (LBBB) as an indicator of advanced cardiovascular involvement in diabetic (DM) patients by examining left ventricular systolic function and proteinurea. Methods: Data of 26 diabetic patients with left bundle branch block (DM with LBBB) were compared with data of 31 diabetic patients without left bundle branch block (DM without LBBB) and 18 nondiabetic patients with left bundle branch block (non‐DM with LBBB). The inclusion criteria were age >45 years, and diabetes mellitus type 2 of >5 years. Results: Mean ages of patients in DM with LBBB, DM without LBBB, and non‐DM with LBBB groups were 67 ± 8, 68 ± 10, and 65 ± 10 years, respectively (P = NS). Females were 65%, 61%, and 61%, respectively (P = NS). Left ventricular ejection fraction in DM with LBBB was significantly lower than in DM without LBBB and non‐DM with LBBB (30 ± 10% vs 49 ± 12% and 47 ± 8%, P < 0.01). Left ventricular end‐diastolic volume was significantly higher in DM with LBBB than in DM without LBBB and non‐DM with LBBB (188.6 ± 16.4 mL vs 147.5 ± 22.3 mL and 165.3 ± 15.2 mL, P < 0.03). Similarly, left ventricular end‐systolic volume was significantly higher in DM with LBBB than in DM without LBBB and non‐DM with LBBB (135.4 ± 14.7 mL vs 83.7 ± 9.5 mL and 96.6 ± 18.4 mL, P < 0.02). No statistically significant difference was seen in left atrial size. Proteinurea in DM with LBBB (79.4 ± 18.9 mg/dL) was significantly higher than in DM without LBBB (35.6 ± 8.5 mg/dL, P < 0.05) and non‐DM with LBBB (12 ± 3.5 mg/dL, P < 0.05); however, there was no significant difference in Hb A1c levels in DM with LBBB and DM without LBBB (9.01% vs 7.81%, P = NS). Conclusions: Left bundle branch block in diabetic patients indicates advanced cardiovascular involvement manifesting with more severe left ventricular systolic dysfunction and proteinurea compared to both diabetic patients without left bundle branch block and nondiabetic patients with left bundle branch block.     

Can the left ventricular early diastolic tissue-to-blood time interval be used to identify a normal pulmonary capillary wedge pressure?

The pulsed Doppler early diastolic left ventricular (LV) tissue (e)-blood (E) onset temporal relationship (e-E) is suggested to predict pulmonary capillary wedge pressure (PCWP), through the formulas: tau = 32 + 0.7(e-E) and PCWP = LV end-systolic pressure x e(-IVRT/tau). Small changes/errors in E could influence the quotient IVRT/tau by oppositely affecting IVRT and e-E. At rest in 50 healthy individuals we noted: e-E: 2 +/- 14 ms; IVRT: 89 +/- 17 ms; calculated tau: 33 +/- 10 ms; and PCWP: 9 +/- 9 mmHg (> 12 mmHg in 28%). Non-pharmacological preload alterations in 14 individuals rendered an intraindividual 'PCWP'-fluctuation of up to 40 mmHg. This application may therefore not be clinically robust.     

Automated DNA extraction of single dog hairs without roots for mitochondrial DNA analysis

Dogs are intensely integrated in human social life and their shed hairs can play a major role in forensic investigations. The overall aim of this study was to validate a semi-automated extraction method for mitochondrial DNA analysis of telogenic dog hairs. Extracted DNA was amplified with a 95% success rate from 43 samples using two new experimental designs in which the mitochondrial control region was amplified as a single large (± 1260 bp) amplicon or as two individual amplicons (HV1 and HV2; ± 650 and 350 bp) with tailed-primers. The results prove that the extraction of dog hair mitochondrial DNA can easily be automated to provide sufficient DNA yield for the amplification of a forensically useful long mitochondrial DNA fragment or alternatively two short fragments with minimal loss of sequence in case of degraded samples.     

New approach to dextran derivatives containing primary amino functions

Dextran derivatives containing primary amino functions were prepared by reacting 4-nitrophenyl carbonate-substituted dextran with the mono-protected diamine N-tritylenediamine (7) . Acidic treatment of the resulting dextran N-[2-(N-trityl)aminoethyl]carbamate (8) yields dextran N-(2-aminoethyl)carbamate (5a) . Alternatively, aminodextran derivatives were prepared by adding 4-nitrophenyl carbonate-substituted dextran to a large excess of a diamine or a triamine.