Isotope shifts in electron affinities and in binding energies of Pb and hyperfine structure of 207Pb.

The isotope shifts in electron affinities of Pb were measured by Walter et al. [Phys. Rev. A 106, L010801 (2022)] to be -0.002(4) meV for 207-208Pb and -0.003(4) meV for 206-208Pb by scanning the threshold of the photodetachment channel Pb-(S3/2◦4) - Pb (3P0), while Chen and Ning reported 0.015(25) and -0.050(22) meV for the isotope shifts on the binding energies measured relative to 3P2 using the SEVI method [J. Chem. Phys. 145, 084303 (2016)]. Here we revisited these isotope shifts by using our second-generation SEVI spectrometer and obtained -0.001(15) meV for 207-208Pb and -0.001(14) meV for 206-208Pb, respectively. In order to aid the experiment by theory, we performed the first ab initio theoretical calculations of isotope shifts in electron affinities and binding energies of Pb, as well as the hyperfine structure of 207Pb-, by using the MCDHF and RCI methods. The isotope shifts in electron affinities of 207-208Pb and 206-208Pb are -0.0023(8) and -0.0037(13) meV for the 3P0 channel, respectively, in good agreement with Walter et al.'s measurements. The isotope shifts in binding energies relative to 3P1,2, -0.0015(8) and -0.0026(13) meV for 207-208Pb and 206-208Pb, respectively, are compatible with the present measurements. The hyperfine constant for the ground state of 207Pb- obtained by the present calculations, A(S3/2◦4)=-1118 MHz, differs by a factor of 3 from the previous estimation by Bresteau et al. [J. Phys. B: At., Mol. Opt. Phys. 52, 065001 (2019)]. The reliability is supported by the good agreement between the theoretical and experimental hyperfine parameters of 209Bi.

Bottom-Up Growth of Monolayer Honeycomb SiC.

The long theorized two-dimensional allotrope of SiC has remained elusive amid the exploration of graphenelike honeycomb structured monolayers. It is anticipated to possess a large direct band gap (2.5 eV), ambient stability, and chemical versatility. While sp^{2} bonding between silicon and carbon is energetically favorable, only disordered nanoflakes have been reported to date. Here we demonstrate large-area, bottom-up synthesis of monocrystalline, epitaxial monolayer honeycomb SiC atop ultrathin transition metal carbide films on SiC substrates. We find the 2D phase of SiC to be almost planar and stable at high temperatures, up to 1200 °C in vacuum. Interactions between the 2D-SiC and the transition metal carbide surface result in a Dirac-like feature in the electronic band structure, which in the case of a TaC substrate is strongly spin-split. Our findings represent the first step towards routine and tailored synthesis of 2D-SiC monolayers, and this novel heteroepitaxial system may find diverse applications ranging from photovoltaics to topological superconductivity.

Debaryomyces is enriched in Crohn's disease intestinal tissue and impairs healing in mice.

Alterations of the mycobiota composition associated with Crohn's disease (CD) are challenging to link to defining elements of pathophysiology, such as poor injury repair. Using culture-dependent and -independent methods, we discovered that Debaryomyces hansenii preferentially localized to and was abundant within incompletely healed intestinal wounds of mice and inflamed mucosal tissues of CD human subjects. D. hansenii cultures from injured mice and inflamed CD tissues impaired colonic healing when introduced into injured conventionally raised or gnotobiotic mice. We reisolated D. hansenii from injured areas of these mice, fulfilling Koch's postulates. Mechanistically, D. hansenii impaired mucosal healing through the myeloid cell-specific type 1 interferon-CCL5 axis. Taken together, we have identified a fungus that inhabits inflamed CD tissue and can lead to dysregulated mucosal healing.

Atg14 protects the intestinal epithelium from TNF-triggered villus atrophy.

Regulation of intestinal epithelial turnover is a key component of villus maintenance in the intestine. The balance of cell turnover can be perturbed by various extrinsic factors including the cytokine TNF, a cell signaling protein that mediates both proliferative and cytotoxic outcomes. Under conditions of infection and damage, defects in autophagy are associated with TNF-mediated cell death and tissue damage in the intestinal epithelium. However, a direct role of autophagy within the context of enterocyte cell death during homeostasis is lacking. Here, we generated mice lacking ATG14 (autophagy related 14) within the intestinal epithelium [Atg14f/f Vil1-Cre (VC)+]. These mice developed spontaneous villus loss and intestinal epithelial cell death within the small intestine. Based on marker studies, the increased cell death in these mice was due to apoptosis. Atg14f/f VC+ intestinal epithelial cells demonstrated sensitivity to TNF-triggered apoptosis. Correspondingly, both TNF blocking antibody and genetic deletion of Tnfrsf1a/Tnfr1 rescued villus loss and cell death phenotype in Atg14f/f VC+ mice. Lastly, we identified a similar pattern of spontaneous villus atrophy and cell death when Rb1cc1/Fip200 was conditionally deleted from the intestinal epithelium (Rb1cc1f/f VC+). Overall, these findings are consistent with the hypothesis that factors that control entry into the autophagy pathway are also required during homeostasis to prevent TNF triggered death in the intestine. Abbreviations: ANOVA: analysis of variance; Atg14: autophagy related 14; Atg16l1: autophagy related 16-like 1 (S. cerevisiae); Atg5: autophagy related 5; cCASP3: cleaved CASP3/caspase-3; cCASP8: cleaved CASP8/caspase-8; CHX: cycloheximide; EdU: 5-ethynyl-2´-deoxyuridine thymidine; f/f: flox/flox; H&E: hematoxylin and eosin; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; Nec-1: necrostatin-1; Rb1cc1/Fip200: RB1-inducible coiled-coil 1; Ripk1: receptor (TNFRSF)-interacting serine-threonine kinase 1; Ripk3: receptor (TNFRSF)-interacting serine-threonine kinase 3; Tnfrsf1a/Tnfr1: tumor necrosis factor receptor superfamily, member 1a; Tnf/ Tnfsf1a: tumor necrosis factor; VC: Vil1/villin 1-Cre.

Reproductive trade-offs in a long-lived bird species: condition-dependent reproductive allocation maintains female survival and offspring quality.

Life history theory is an essential framework to understand the evolution of reproductive allocation. It predicts that individuals of long-lived species favour their own survival over current reproduction, leading individuals to refrain from reproducing under harsh conditions. Here we test this prediction in a long-lived bird species, the Siberian jay Perisoreus infaustus. Long-term data revealed that females rarely refrain from breeding, but lay smaller clutches in unfavourable years. Neither offspring body size, female survival nor offspring survival until the next year was influenced by annual condition, habitat quality, clutch size, female age or female phenotype. Given that many nests failed due to nest predation, the variance in the number of fledglings was higher than the variance in the number of eggs and female survival. An experimental challenge with a novel pathogen before egg laying largely replicated these patterns in two consecutive years with contrasting conditions. Challenged females refrained from breeding only in the unfavourable year, but no downstream effects were found in either year. Taken together, these findings demonstrate that condition-dependent reproductive allocation may serve to maintain female survival and offspring quality, supporting patterns found in long-lived mammals. We discuss avenues to develop life history theory concerning strategies to offset reproductive costs.

Observation of 54Ni: cross-conjugate symmetry in f7/2 mirror energy differences.

Gamma decays from excited states up to Jpi=6+ in the N=Z-2 nucleus 54Ni have been identified for the first time. Level energies are compared with those of the isobars 54Co and 54Fe and of the cross-conjugate nuclei of mass A=42. The good but puzzling f7/ cross-conjugate symmetry in mirror and triplet energy differences is analyzed. Shell model calculations reproduce the new data but the necessary nuclear charge-dependent phenomenology is not fully explained by modern nucleon-nucleon potentials.

Isospin symmetry of odd-odd mirror nuclei: identification of excited states in N=Z-2 48Mn.

Excited states have been observed in the N=Z-2 odd-odd nucleus 48Mn for the first time. Through comparison with the structure of 48V, a first high-spin study of an odd-odd mirror pair has been achieved. Differences between the T=1 analogue states in this pair have been interpreted in terms of Coulomb effects, with the aid of shell-model calculations in the full pf valence space. Unlike other mirror pairs, the energy differences have been interpreted almost entirely as due to a monopole effect associated with smooth changes in radius (or deformation) as a function of angular momentum. In addition, the large energy shift between analogue negative-parity states is interpreted in terms of the electromagnetic spin-orbit interaction in nuclei.

58Ni: an unpaired band crossing at new heights of angular momentum for rotating nuclei.

High-spin states in 58Ni have been investigated by means of the fusion-evaporation reaction 28Si(32S, 2p)58Ni at 130 MeV beam energy. Discrete-energy levels are observed in 58Ni at record-breaking 42 MeV excitation energy and angular momenta in excess of 30h. The states form regular rotational bands with unprecedented high rotational frequencies. A comparison with configuration dependent cranked Nilsson-Strutinsky calculations reveals an exceptional two-band crossing scenario, the interaction strength of which is strongly shape dependent.

Effective charges in the fp shell.

Following the heavy-ion fusion-evaporation reaction 32S+24Mg at 95 MeV beam energy the lifetimes of analogue states in the T(z)=+/-1/2 A=51 mirror nuclei 51Fe and 51Mn have been measured using the Cologne plunger device coupled to the GASP gamma-ray spectrometer. The deduced B(E2;27/2(-)-->23/2(-)) values afford a unique opportunity to probe isoscalar and isovector polarization charges and to derive effective proton and neutron charges, epsilon(p) and epsilon(n), in the fp shell. A comparison between the experimental results and several different large-scale shell-model calculations yields epsilon(p) approximately 1.15e and epsilon(n) approximately 0.80e.

Unusual isospin-breaking and isospin-mixing effects in the A=35 mirror nuclei.

Excited states have been studied in 35Ar following the 16O(24Mg,1alpha1n)35Ar fusion-evaporation reaction at 60 MeV using the Ge-detector array GASP. A comparison with the mirror nucleus 35Cl shows two remarkable features: (i) A surprisingly large energy difference for the 13/2(-) states, in which the hitherto overlooked electromagnetic spin-orbit term is shown to play a major role, and (ii) a very different decay pattern for the 7/2(-) states, which provides direct evidence of isospin mixing.

A dynamic model of hypothermia as an adaptive response by small birds to winter conditions.

We present a dynamic programming model which is used to investigate hypothermia as an adaptive response by small passerine birds in winter. The model predicts that there is a threshold function of reserves during the night, below which it is optimal to enter hypothermia, and above which it is optimal to rest. This threshold function decreases during the night, with a particularly sharp drop at the end of the night, representing the time and energy costs associated with returning to normal body temperature. The results of the model emphasise the trade-off between energy and predation, not just between foraging options, but also between foraging during the day and entering hypothermia at night. The value of being able to use hypothermia represents not just energy savings, but also reduced predation risk due to changes in the optimal foraging strategy. Conditions which give a high value of hypothermia are short photoperiod, variable food supply, low temperatures, poor and scarce food supplies.

Dystroglycan overexpression in vivo alters acetylcholine receptor aggregation at the neuromuscular junction.

Dystroglycan is a member of the transmembrane dystrophin glycoprotein complex in muscle that binds to the synapse-organizing molecule agrin. Dystroglycan binding and AChR aggregation are mediated by two separate domains of agrin. To test whether dystroglycan plays a role in receptor aggregation at the neuromuscular junction, we overexpressed it by injecting rabbit dystroglycan RNA into one- or two-celled Xenopus embryos. We measured AChR aggregation in myotomes by labeling them with rhodamine-alpha-bungarotoxin followed by confocal microscopy and image analysis. Dystroglycan overexpression decreased AChR aggregation at the neuromuscular junction. This result is consistent with dystroglycan competition for agrin without signaling AChR aggregation. It also supports the hypothesis that dystroglycan is not the myotube-associated specificity component, (MASC) a putative coreceptor needed for agrin to activate muscle-specific kinase (MuSK) and signal AChR aggregation. Dystroglycan was distributed along the surface of muscle membranes, but was concentrated at the ends of myotomes, where AChRs normally aggregate at synapses. Overexpressed dystroglycan altered AChR aggregation in a rostral-caudal gradient, consistent with the sequential development of neuromuscular synapses along the embryo. Increasing concentrations of dystroglycan RNA did not further decrease AChR aggregation, but decreased embryo survival. Development often stopped during gastrulation, suggesting an essential, nonsynaptic role of dystroglycan during this early period of development.

Reduction in cell size during development of the spinal cord.

During development, spinal cord cells of the frog Xenopus laeuis undergo a reduction in size. This phenomenon occurs during neural tube formation and continues at least until the start of metamorphosis. The number and shape of spinal cord cells also changes, but not always in synchrony with the reduction in cell size. The concomitant change in size and number of spinal cord cells during embryogenesis suggests that a cleavage type of reductive division contributes to the decrease in cell size. Blocking cell division with a combination of hydroxyurea and aphidicolin (HUA) stops the decrease in cell size during embryonic development without affecting the differentiation of a specific class of catecholaminergic neurons. HUA treatment during larval stages does not block the decrease in catecholaminergic neuron size. Thus, both mitotic and postmitotic cells decrease in size during spinal cord development. The two mechanisms are prevalent at different developmental stages with reductive division and cellular atrophy common during embryonic and larval phases, respectively. Like other regressive changes such as cell death and synapse elimination, decreases in cell size affect spinal cord morphogenesis and presumably the function of developing spinal cord cells.

Multichip free-space global optical interconnection demonstration with integrated arrays of vertical-cavity surface-emitting lasers and photodetectors.

The experimental optical interconnection module of the Free-Space Accelerator for Switching Terabit Networks (FAST-Net) project is described and characterized. Four two-dimensional (2-D) arrays of monolithically integrated vertical-cavity surface-emitting lasers (VCSEL's) and photodetectors (PD's) were designed, fabricated, and incorporated into a folded optical system that links a 10 cm x 10 cm multichip smart pixel plane to itself in a global point-to-point pattern. The optical system effects a fully connected network in which each chip is connected to all others with a multichannel bidirectional data path. VCSEL's and detectors are arranged in clusters on the chips with an interelement spacing of 140 microm. Calculations based on measurements of resolution and registration tolerances showed that the square 50-microm detector in a typical interchip link captures approximately 85% of incident light from its associated VCSEL. The measured optical transmission efficiency was 38%, with the losses primarily due to reflections at the surfaces of the multielement lenses, which were not antireflection coated for the VCSEL wavelength. The overall efficiency for this demonstration is therefore 32%. With the measured optical confinement, an optical system that is optimized for transmission at the VCSEL wavelength will achieve an overall efficiency of greater than 80%. These results suggest that, as high-density VCSEL-based smart pixel technology matures, the FAST-Net optical interconnection concept will provide a low-loss, compact, global interconnection approach for high bisection-bandwidth multiprocessor applications in switching, signal processing, and image processing.

Automated design of integrated circuits with area-distributed input-output pads.

We present a method for automating the creation of complementary-metal-oxide-semiconductor (CMOS) integrated circuits that successfully utilizes a large number of area-distributed pads for input-output communication. This method uses Duet Technologies' epoch computer-aided-design tool for automated placement and routing of CMOS circuitry, given a schematic netlist as an input. The novelty of this approach is that it uses Duet Technologies' eggo program to place and route area-pad signals. To verify this methodology, it is applied to the design of a digital signal-processing circuit, with 200 optical area-pad input-outputs and 44 perimeter-pad input-outputs, that is being fabricated with Bell Labs 1997 CMOS-multiple-quantum-well foundry. The layout results are as good as or better than the results obtained by manual layout.

Survival enhancement through food sharing: a means for parental control of natal dispersal.

The value of food sharing among relatives is analyzed for a situation where fitness equals survival. In seasonal environments the minimum food abundance may set a limit to group living. Delayed dispersal is predicted to be linked to relaxed winter competition and high parental survival. Enhanced survival for the offspring when parents share food could be a sufficient reason to delay dispersal, while early dispersal in advance of food shortage periods may be induced by a competitive relationship. At low resource abundance dominant parents do best by being competitive and retaining all resources. For food abundance higher than the expected requirements food sharing with independent offspring is possible, although it has a non-zero cost. Food sharing parents still retain most of resources to themselves, but the resource share given to subordinate offspring gradually gets larger when food abundance increases. Except for at very low food abundance, where subordinates may adopt a "suicidal" behaviour and cede their resources to the dominant, there is a conflict over how to share the resources.