Deeper-band electron contributions to stopping power of silicon for low-energy ions.

This study provides accurate results for the electronic stopping cross sections of H, He, N, and Ne in silicon in low to intermediate energy ranges using various non-perturbative theoretical methods, including real-time time-dependent density functional theory, transport cross section, and induced-density approach. Recent experimental findings [Ntemou et al., Phys. Rev. B 107, 155145 (2023)] revealed discrepancies between the estimates of density functional theory and the observed values. We show that these discrepancies vanish by considering the nonuniform electron density of the deeper silicon bands for ion velocities approaching zero (v → 0). This indicates that mechanisms such as "elevator" and "promotion," which can dynamically excite deeper-band electrons, are active, enabling a localized free-electron gas to emulate ion energy loss, as pointed out by Lim et al. [Phys. Rev. Lett. 116, 043201 (2016)]. The observation and the description of a velocity-proportionality breakdown in electronic stopping cross sections at very low velocities are considered to be a signature of the contributions of deeper-band electrons.

Efficient computational modeling of electronic stopping power of organic polymers for proton therapy optimization.

This comprehensive study delves into the intricate interplay between protons and organic polymers, offering insights into proton therapy in cancer treatment. Focusing on the influence of the spatial electron density distribution on stopping power estimates, we employed real-time time-dependent density functional theory coupled with the Penn method. Surprisingly, the assumption of electron density homogeneity in polymers is fundamentally flawed, resulting in an overestimation of stopping power values at energies below 2 MeV. Moreover, the Bragg rule application in specific compounds exhibited significant deviations from experimental data around the stopping maximum, challenging established norms.

Some cases of common variable immunodeficiency may be due to a mutation in the SBDS gene of Shwachman-Diamond syndrome.

Known genetic defects currently account for only a small proportion of patients meeting criteria for 'probable' or 'possible' common variable immunodeficiency (CVID). A 59-year-old male with a 12-year history of CVID on intravenous immunoglobulin (IVIG) is presented who developed bronchiectasis, cytopenias and malabsorption that are recognized complications of CVID. Work-up for his malabsorption suggested the possibility of Shwachman-Diamond syndrome, confirmed by mutation testing. With the identification of the molecular defect in Shwachman-Diamond syndrome (SDS), it is becoming clear that not all SDS patients have the prominent features of neutropenia or pancreatic malabsorption. A meta-analysis of published immunological defects in SDS suggests that four of 14 hypogammaglobulinaemic SDS patients meet criteria for 'possible' CVID. Mutations in the SBDS gene may therefore be the fifth identified molecular defect in CVID.

Severe neonatal manifestations of Costello syndrome.

BACKGROUND: Costello syndrome (CS) is due to mutations in HRAS, with the most common mutation being c.34G>A (p.G12S), found in most patients in all the published series. A small number of less common mutations have been reported. POPULATION STUDIED: HRAS mutation analysis has been undertaken in 74 predominantly British patients with a possible diagnosis of CS. A HRAS mutation was found in 27 patients, 15 of whom have been previously reported. PHENOTYPE ANALYSIS: Four cases had an unusually severe phenotype, associated in three cases with two unusual mutations, c.35G>A, p.G12D in two cases and c.34G>T, p.G12C in the other. Hypoglycaemia, renal abnormalities, severe early cardiomyopathy, congenital lung and airway abnormalities, pleural and pericardial effusion, chylous ascites and pulmonary lymphangectasia are confirmed as part of the clinical spectrum seen in CS. A lung pathology resembling alveolar capillary dysplasia is reported in one case. CONCLUSION: These cases illustrate that the diagnosis of CS may be difficult in the newborn period, and should be considered in the differential diagnosis of the sick newborn infant with multisystem disease. Study of more cases will be required to establish if there is a definite association between severe disease and less common mutations.