Search

We explore the ultrafast generation of spin currents in magnetic multilayer samples by applying fs laser pulses to one layer and measuring the magnetic response in the other layer by element-resolved x-ray spectroscopy. In Ni(5 nm)/Ru(2 nm)/Fe(4 nm), the Ni and Fe magnetization directions couple antiferromagnetically due to the Ruderman–Kittel–Kasuya–Yosida interaction but may be oriented parallel through an applied magnetic field. After exciting the top Ni layer with a fs laser pulse, we also find that the Fe layer underneath demagnetizes, with a 4.1 ± 1.9 % amplitude difference between parallel and antiparallel orientation of the Ni and Fe magnetizations. We attribute this difference to the influence of a spin current generated by the fs laser pulse that transfers angular momentum from the Ni into the Fe layer. Our results confirm that superdiffusive spin transport plays a role in determining the sub-ps demagnetization dynamics of synthetic antiferromagnetic layers, but also evidence large depolarization effects due to hot electron dynamics, which are independent of the relative alignment of the magnetization in Ni and Fe. [ABSTRACT FROM AUTHOR]

Aim: Reoperative pelvic surgery is rarely hostile and unsafe. Kraske's procedure has historically been used to approach the mid‐rectum and to resect retrorectal tumors. However, it provides limited access to the pelvis and is best in the 'virgin' pelvis. We have encountered a select group of patients who required completion proctectomy or resection of a disconnected ileoanal J‐pouch where trans‐abdominal access to the pelvis was not possible and access to the pelvis could only be safely gained by a prone en bloc sacrectomy. Method: We describe a prone approach that provides an alternative route of access to the hostile pelvis. After exposure of the sacrum and coccyx and transection of the sacrum, access to the mesorectal plane is achieved and a proctectomy (or resection of an ileoanal J‐pouch) can be completed. The procedure is similar to the Kraske approach but requires a higher and wider exposure similar to the extent of an abdominal resection; however, the operation is performed in 'reverse'. Results: We found that this approach was feasible and safe in the previously operated, hostile pelvis. We employed it in one patient to excise a disconnected J‐pouch with chronic sepsis and in another patient for a completion proctectomy. Both patients had an uneventful recovery and clear margins were obtained with no complications. Conclusion: The en bloc prone sacrectomy approach is a useful alternative in a very select group of patients with difficult trans‐abdominal access to the pelvis. Experience in pelvic surgery and identification of clear anatomical landmarks is paramount to avoid catastrophic uncontrollable bleeding. [ABSTRACT FROM AUTHOR]

We present a compact setup for spin-, time-, and angle-resolved photoemission spectroscopy. A 10 kHz titanium sapphire laser system delivers pulses of 20 fs duration, which drive a high harmonic generation-based source for ultraviolet photons at 21 eV for photoemission. The same laser also excites the sample for pump–probe experiments. Emitted electrons pass through a hemispherical energy analyzer and a spin-filtering element. The latter is based on spin-polarized low-energy electron diffraction on an Au-passivated iridium crystal. The performance of the measurement system is discussed in terms of the resolution and efficiency of the spin filter, which are higher than those for Mott-based techniques. [ABSTRACT FROM AUTHOR]

Most experiments on ultrafast magnetodynamics have been conducted using the magneto-optical Kerr effect. Here, we compare the Kerr effect's magnetic sensitivity to the spin dynamics measured by photoemission. The magnetization dynamics on an Fe/W(110) thin film are probed by spin-resolved photoemission spectroscopy and the Kerr effect. The results reveal similarities between the spin dynamics at low binding energy and the response probed by the Kerr effect. Therefore, the Kerr effect probes states relevant for spin transport and spin flips but may not be sensitive to the entire magnetic moment in femtosecond spin dynamics experiments. [ABSTRACT FROM AUTHOR]

Time-resolved photoemission with ultrafast pump and probe pulses is an emerging technique with wide application potential. Real-time recording of nonequilibrium electronic processes, transient states in chemical reactions, or the interplay of electronic and structural dynamics offers fascinating opportunities for future research. Combining valence-band and core-level spectroscopy with photoelectron diffraction for electronic, chemical, and structural analyses requires few 10 fs soft X-ray pulses with some 10 meV spectral resolution, which are currently available at high repetition rate free-electron lasers. We have constructed and optimized a versatile setup commissioned at FLASH/PG2 that combines free-electron laser capabilities together with a multidimensional recording scheme for photoemission studies. We use a full-field imaging momentum microscope with time-of-flight energy recording as the detector for mapping of 3D band structures in (kx, ky, E) parameter space with unprecedented efficiency. Our instrument can image full surface Brillouin zones with up to 7 Å−1 diameter in a binding-energy range of several eV, resolving about 2.5 × 105 data voxels simultaneously. Using the ultrafast excited state dynamics in the van der Waals semiconductor WSe2 measured at photon energies of 36.5 eV and 109.5 eV, we demonstrate an experimental energy resolution of 130 meV, a momentum resolution of 0.06 Å−1, and a system response function of 150 fs. [ABSTRACT FROM AUTHOR]

Background: The CXCL12-CXCR4 chemokine axis plays an important role in cell trafficking as well as in tumor progression. In colorectal cancer (CRC), the chemokine receptor CXCR4 has been shown to be an unfavorable prognostic factor in some studies, however, the role of its activated (phosphorylated) form, pCXCR4, has not yet been evaluated. Here, we aimed to investigate the prognostic value of CXCR4 and pCXCR4 in a large cohort of CRC patients. Patients and methods: A tissue microarray (TMA) of 684 patient specimens of primary CRCs was analyzed by immunohistochemistry (IHC) for the expression of CXCR4 and pCXCR4 by tumor cells and tumor-infiltrating immune cells (TICs). Results: The combined high expression of CXCR4 and pCXCR4 showed a favorable 5-year overall survival rate (68%; 95%CI = 59-76%) compared to tumors showing a high expression of CXCR4 only (48%; 95%CI = 41-54%). High expression of pCXCR4 was significantly associated with a favorable prognosis in a test and validation group ( p = 0.015 and p = 0.0001). Moreover, we found that CRCs with a high density of pCXCR4+ tumor-infiltrating immune cells (TICs) also showed a favorable prognosis in a test and validation group ( p = 0.054 and p = 0.004). Univariate Cox regression analysis for TICs revealed that a high density of pCXCR4+ TICs was a favorable prognostic marker for overall survival (HR = 0.97,95%CI = 0.96-1.00; p = 0.01). In multivariate Cox regression survival analyses a high expression of pCXCR4 in tumor cells lost its association with a better overall survival (HR = 0.99; 95%CI = 0.99-1.00, p = 0.098). Conclusion: Our results show that high densities of CXCR4 and pCXCR4 positive TICs are favorable prognostic factors in CRC. [ABSTRACT FROM AUTHOR]

Ultrafast demagnetization of ferromagnetic metals can be achieved by a heat pulse propagating in the electron gas of a non-magnetic metal layer, which absorbs a pump laser pulse. Demagnetization by electronic heating is investigated on samples with different thicknesses of the absorber layer on nickel. This allows us to separate the contribution of thermalized hot electrons compared to non-thermal electrons. An analytical model describes the demagnetization amplitude as a function of the absorber thickness. The observed change of demagnetization time can be reproduced by diffusive heat transport through the absorber layer. [ABSTRACT FROM AUTHOR]

Recent studies in multiple epithelial cancers have shown that the inhibitory receptor programmed cell death 1 (PD-1) is expressed on tumor-infiltrating lymphocytes and/or programmed death ligand 1 (PD-L1) is expressed on tumor cells, suggesting that antitumor immunity may be modulated by the PD-1/PD-L1 signaling pathway. In addition, phase 1 clinical trials with monoclonal antibodies targeting PD-1 or PD-L1 have shown promising results in several human cancers. The purpose of this study was to investigate the impact of PD-L1 expression in human breast cancer specimens. We conducted an immunohistochemistry study using a tissue microarray encompassing 650 evaluable formalin-fixed breast cancer cases with detailed clinical annotation and outcomes data. PD-L1 was expressed in 152 (23.4 %) of the 650 breast cancer specimens. Expression was significantly associated with age, tumor size, AJCC primary tumor classification, tumor grade, lymph node status, absence of ER expression, and high Ki-67 expression. In univariate analysis, PD-L1 expression was associated with a significantly worse OS. In multivariate analysis, PD-L1 expression remained an independent negative prognostic factor for OS. In subset analyses, expression of PD-L1 was associated with significantly worse OS in the luminal B HER2 subtype, the luminal B HER2 subtype, the HER2 subtype, and the basal-like subtype. This is the first study to demonstrate that PD-L1 expression is an independent negative prognostic factor in human breast cancer. This finding has important implications for the application of antibody therapies targeting the PD-1/PD-L1 signaling pathway in this disease. [ABSTRACT FROM AUTHOR]