Out-of-plane nesting driven spin spiral in ultrathin Fe/Cu(001) films

Epitaxial ultrathin Fe films on fcc Cu(001) exhibit a spin spiral (SS), in contrast to the ferromagnetism of bulk bcc Fe. We study the in-plane and out-of-plane Fermi surfaces (FSs) of the SS in 8 monolayer Fe/Cu(001) films using energy dependent soft x-ray momentum-resolved photoemission spectroscopy. We show that the SS originates in nested regions confined to out-of-plane FSs, which are drastically modified compared to in-plane FSs. From precise reciprocal space maps in successive zones, we obtain the associated real space compressive strain of 1.5+-0.5% along c-axis. An autocorrelation analysis quantifies the incommensurate ordering vector q=(2pi/a)(0,0,~0.86), favoring a SS and consistent with magneto-optic Kerr effect experiments. The results reveal the importance of in-plane and out-of-plane FS mapping for ultrathin films.Comment: 4 pages, 3 figure

The emergence of a new wintertime Arctic energy balance regime

The modern Arctic climate during wintertime is characterized by sea-ice cover, a strong surface temperature inversion, and the absence of convection. Correspondingly, the energy balance in the Arctic atmosphere today is dominated by atmospheric radiative cooling and advective heating, so-called radiative advective equilibrium. Climate change in the Arctic involves sea-ice melt, vanishing of the surface inversion, and emergence of convective precipitation. Here we show climate change in the Arctic involves the emergence of a new energy balance regime characterized by radiative cooling, convective heating, and advective heating, so-called radiative convective advective equilibrium. A time-dependent decomposition of the atmospheric energy balance shows the regime transition is associated with enhanced radiative cooling followed by decreased advective heating. The radiative cooling response consists of a robust clear-sky greenhouse effect and a transient cloud contribution that varies across models. Mechanism-denial experiments in an aquaplanet with and without interactive sea ice highlight the important role of sea-ice melt in both the radiative cooling and advective heating responses. The results show that climate change in the Arctic involves temporally evolving mechanisms, suggesting that an emergent constraint based on historical data or trends may not constrain the long-term response

Quantifying Key Mechanisms That Contribute to the Deviation of the Tropical Warming Profile From a Moist Adiabat

Climate models project tropical warming is amplified aloft relative to the surface in response to increased CO2. Here we show moist adiabatic adjustment overpredicts the multimodel mean 300 hPa temperature response by 16.6–25.3% across the CMIP5 model hierarchy. We show three mechanisms influence overprediction: climatological large-scale circulation, direct effect of increased CO2, and convective entrainment. Accounting for the presence of a climatological large-scale circulation and the direct effect of CO2 reduces the CMIP5 multimodel mean overprediction by 0.7–7.2% and 2.8–3.9%, respectively, but does not eliminate it. To quantify the influence of entrainment, we vary the Tokioka parameter in aquaplanet simulations. When entrainment is decreased by decreasing the Tokioka parameter from 0.1 to 0, overprediction decreases by 9.6% and 10.4% with and without a large-scale circulation, respectively. The sensitivity of overprediction to climatological entrainment rate in the aquaplanet mostly follows the predictions of zero-buoyancy bulk-plume and spectral-plume models

Raman and fluorescence contributions to resonant inelastic soft x-ray scattering on LaAlO3_3/SrTiO3_3 heterostructures

We present a detailed study of the Ti 3$d$ carriers at the interface of LaAlO$_3$/SrTiO$_3$ heterostructures by high-resolution resonant inelastic soft x-ray scattering (RIXS), with special focus on the roles of overlayer thickness and oxygen vacancies. Our measurements show the existence of interfacial Ti 3$d$ electrons already below the critical thickness for conductivity and an increase of the total interface charge up to a LaAlO$_3$ overlayer thickness of 6 unit cells before it levels out. By comparing stoichiometric and oxygen deficient samples we observe strong Ti 3$d$ charge carrier doping by oxygen vacancies. The RIXS data combined with photoelectron spectroscopy and transport measurements indicate the simultaneous presence of localized and itinerant charge carriers. However, it is demonstrated that the relative amount of localized and itinerant Ti $3d$ electrons in the ground state cannot be deduced from the relative intensities of the Raman and fluorescence peaks in excitation energy dependent RIXS measurements, in contrast to previous interpretations. Rather, we attribute the observation of either the Raman or the fluorescence signal to the spatial extension of the intermediate state reached in the RIXS excitation process.Comment: 9 pages, 6 figure

Changes to the cerite group nomenclature

The cerite and merrillite groups belong to the cerite supergroup. Some nomenclature and classification changes have been made to the cerite group, whereas the merrillite group remains unchanged. Minerals of the cerite group have the general formula A9XM[T7O24Ø4]Z3, where T is Si. The cerite group, from now on, is subdivided into two subgroups, cerite and taipingite. The root name will be cerite and taipingite if the Z anions are dominated by (OH) and F, respectively. The prefix ferri-or alumino-will be added if the M cations are dominated by Fe3+ or Al, respectively. If the M cation is Mg, there will be no prefix. Taking into account the valency-imposed double site occupancy and the site total charge approach, a double suffix will be used to represent the essential A constituents in the general chemical formula. Cerite-(Ce), aluminocerite-(Ce), ferricerite-(La), and taipingite-(Ce) have been renamed cerite-(CeCa), aluminocerite-(CeCa), ferricerite-(LaCa), and taipingite-(CeCa), respectively. The newly approved mineral aluminotaipingite-(CeCa) also belongs to the taipingite subgroup

Tracking of Normal and Malignant Progenitor Cell Cycle Transit in a Defined Niche.

While implicated in therapeutic resistance, malignant progenitor cell cycle kinetics have been difficult to quantify in real-time. We developed an efficient lentiviral bicistronic fluorescent, ubiquitination-based cell cycle indicator reporter (Fucci2BL) to image live single progenitors on a defined niche coupled with cell cycle gene expression analysis. We have identified key differences in cell cycle regulatory gene expression and transit times between normal and chronic myeloid leukemia progenitors that may inform cancer stem cell eradication strategies