Nucleation and early stages of layer-by-layer growth of metal organic frameworks on surfaces

High resolution atomic force microscopy (AFM) is used to resolve the evolution of crystallites of a metal organic framework (HKUST-1) grown on Au(111) using a liquid-phase layer-by-layer methodology. The nucleation and faceting of individual crystallites is followed by repeatedly imaging the same submicron region after each cycle of growth and we find that the growing surface is terminated by {111} facets leading to the formation of pyramidal nanostructures for [100] oriented crystallites, and triangular [111] islands with typical lateral dimensions of tens of nanometres. AFM images reveal that crystallites can grow by 5−10 layers in each cycle. The growth rate depends on crystallographic orientation and the morphology of the gold substrate, and we demonstrate that under these conditions the growth is nanocrystalline with a morphology determined by the minimum energy surface

Calculation of the properties of the rotational bands of 155,157^{155,157}Gd

We reexamine the long-standing problem of the microscopic derivation of a particle-core coupling model. We base our research on the Klein-Kerman approach, as amended by D\"onau and Frauendorf. We describe the formalism to calculate energy spectra and transition strengths in some detail. We apply our formalism to the rotational nuclei $^{155,157}$Gd, where recent experimental data requires an explanation. We find no clear evidence of a need for Coriolis attenuation.Comment: 27 pages, 13 uuencoded postscript figures. Uses epsf.st

Stability and Representation Dependence of the Quantum Skyrmion

A constructive realization of Skyrme's conjecture that an effective pion mass ``may arise as a self consistent quantal effect'' based on an ab initio quantum treatment of the Skyrme model is presented. In this quantum mechanical Skyrme model the spectrum of states with $I=J$, which appears in the collective quantization, terminates without any infinite tower of unphysical states. The termination point depends on the model parameters and the dimension of the SU(2) representation. Representations, in which the nucleon and $\Delta_{33}$ resonance are the only stable states, exist. The model is developed for both irreducible and reducible representations of general dimension. States with spin larger than 1/2 are shown to be deformed. The representation dependence of the baryon observables is illustrated numerically.Comment: 19 pages, Late

High temperature MBE of graphene on sapphire and hexagonal boron nitride flakes on sapphire

The discovery of graphene and its remarkable electronic properties has provided scientists with a revolutionary material system for electronics and optoelectronics. Here, the authors investigate molecular beam epitaxy (MBE) as a growth method for graphene layers. The standard dual chamber GENxplor has been specially modified by Veeco to achieve growth temperatures of up to 1850 _C in ultrahigh vacuum conditions and is capable of growth on substrates of up to 3 in. in diameter. To calibrate the growth temperatures, the authors have formed graphene on the Si-face of SiC by heating wafers to temperatures up to 1400 _C and above. To demonstrate the scalability, the authors have formed graphene on SiC substrates with sizes ranging from 10 _ 10mm2 up to 3-in. in diameter. The authors have used a carbon sublimation source to grow graphene on sapphire at substrate temperatures between 1000 and 1650 _C (thermocouple temperatures). The quality of the graphene layers is significantly improved by growing on hexagonal boron nitride (h-BN) substrates. The authors observed a significant difference in the sticking coefficient of carbon on the surfaces of sapphire and h-BN flakes. Our atomic force microscopy measurements reveal the formation of an extended hexagonal moir_e pattern when our MBE layers of graphene on h-BN flakes are grown under optimum conditions. The authors attribute this moir_e pattern to the commensurate growth of crystalline graphene on h-BN

Is physical activity a trigger factor for subarachnoid hemorrhage?

Introduction: Subarachnoid hemorrhage (SAH) is a serious pathology, associated with 43% mortality and significant disability. In the absence of relevant guidelines, some teams advocate that patients harboring an unruptured intracranial aneurysm (ICA) abstain from all sports activity, as a prophylactic precaution. The aim of the present study was to evaluate the impact of physical activity as a risk factor for SAH, through a review of the literature. Method: A systematic literature review was performed for the period 2000 to 2020 in accordance with the PRISMA guidelines. Prospective and retrospective articles reporting more than 50 patients whose physical activity was associated with onset of SAH were included. The main end-point was prevalence of SAH occurring after physical activity. For comparison purposes, the prevalences of other circumstances were calculated to establish a range of frequency. Results: Physical activity appeared to be quite rarely associated with onset of SAH, with a prevalence of 3%, compared to 30% at rest, 7.3% in association with defecation and 4.5% in association with sexual activity. Age under 60 years, male gender (M/F ratio 1.38) and smoking (67.1%) were associated with onset of SAH during physical activity. Conclusion: Physical activity appears to be a rare trigger factor for SAH. These results are in contrast to the idea that physical activity should, as a precaution, be avoided in patients with unruptured ICA. There is at present no scientific evidence of an association with aneurysmal SAH.Introduction. – L’hémorragie sous-arachnoïdienne (HSA) est une maladie grave responsable de 43 % de mortalité et d’un handicap important. Devant l’absence de recommandation, le principe de précaution a conduit certains soignants à déconseiller la pratique sportive chez les patients présentant un anévrisme intracrânien. L’objectif de ce travail était d’évaluer la responsabilité de l’activité physique comme circonstance de la survenue d’une HSA en se basant sur une revue de la littérature. Méthode. – Une revue systématique de la littérature selon les critères PRISMA a été réalisée de 2000 à 2020. Des articles prospectifs ou rétrospectifs de plus de 50 patients dont l’activité physique était une circonstance d’hémorragie sous-arachnoïdienne ont été inclus. Le critère de jugement principal était la prévalence de l’HSA survenant après une activité physique. À des fins de comparaison, les prévalences des autres circonstances ont été calculées pour établir un rang de fréquence. Résultats. – L’activité physique semble être une circonstance rare dans la survenue de l’HSA avec une prévalence de 3 % par rapport au repos (30 %), à la défécation (7,3 %) ou aux rapports sexuels (4,5 %). Les patients de moins de 60 ans (67 %), les hommes (ratio H/F de 1,38) et les fumeurs (67,1 %) semblaient plus susceptibles d’être victimes d’une HSA lors de la pratique d’une activité physique. Conclusion. – L’activité physique semble être une circonstance rare d’HSA. Ces résultats vont à l’encontre du principe de précaution chez les patients atteints d’un anévrisme intracrânien non rompu, car il n’existe actuellement aucune preuve scientifique d’association de l’activité physique avec l’HSA anévrismale. © 2021 Elsevier Masson SAS. Tous droits reserves

Quantitative imaging of concentrated suspensions under flow

We review recent advances in imaging the flow of concentrated suspensions, focussing on the use of confocal microscopy to obtain time-resolved information on the single-particle level in these systems. After motivating the need for quantitative (confocal) imaging in suspension rheology, we briefly describe the particles, sample environments, microscopy tools and analysis algorithms needed to perform this kind of experiments. The second part of the review focusses on microscopic aspects of the flow of concentrated model hard-sphere-like suspensions, and the relation to non-linear rheological phenomena such as yielding, shear localization, wall slip and shear-induced ordering. Both Brownian and non-Brownian systems will be described. We show how quantitative imaging can improve our understanding of the connection between microscopic dynamics and bulk flow.Comment: Review on imaging hard-sphere suspensions, incl summary of methodology. Submitted for special volume 'High Solid Dispersions' ed. M. Cloitre, Vol. xx of 'Advances and Polymer Science' (Springer, Berlin, 2009); 22 pages, 16 fig

Performance evaluation of the solar backscatter ultraviolet radiometer, model 2 (SBUV/2) inflight calibration system

The Solar Backscatter Ultraviolet Radiometer, Model 2 (SBUV/2) instruments, as part of their regular operation, deploy ground aluminum reflective diffusers to deflect solar irradiance into the instrument's field-of-view. Previous SBUV instrument diffusers have shown a tendency to degrade in their reflective efficiencies. This degradation will add a trend to the ozone measurements if left uncorrected. An extensive in-flight calibration system was designed into the SBUV/2 instruments to effectively measure the degradation of the solar diffuser (Ball Aerospace Systems Division 1981). Soon after launch, the NOAA-9 SBUV/2 calibration system was unable to track the diffuser's reflectivity changes due, in part, to design flows (Frederick et al. 1986). Subsequently, the NOAA-11 SBUV/2 calibration system was redesigned and an analysis of the first 2 years of data (Weiss et al. 1991) indicated the NOAA-11 SBUV/2 onboard calibration system's performance to be exceeding preflight expectations. This paper will describe the analysis of the first three years NOAA-11 SBUV/2 calibration system data

Central Nervous System Siderosis Associated with Multiple Cerebral Aneurysms: Literature Review and Description of an Additional Case

Background: Superficial siderosis (SS) of the central nervous system is a rare disease characterized by deposition of hemosiderin along the leptomeninges due to chronic or recurrent bleeding into the subarachnoid space. The association of unruptured intracranial aneurysm (IA) and cortical SS is quite rare. Methods: A systematic literature review to assess possible commonalities and/or differences of previous reported cases was undertaken. We report an additional case from our institution. Results: A 40-year-old woman presented with a history of generalized seizures over the past year. There was no clinical history suggestive of aneurysm rupture. Magnetic resonance imaging revealed 2 aneurysms of the right middle cerebral artery (MCA) bifurcation associated with hemosiderin deposition along the right sylvian fissure and a third aneurysm of the left MCA bifurcation. Magnetic resonance imaging showed wall enhancing thickening of the larger right MCA aneurysm. The patient underwent surgical clipping of all 3 MCA aneurysms in a staged procedure. Histological examination revealed hemosiderin deposits within the aneurysm wall and surrounding gliosis. Conclusions: Our literature review found 24 reported cases of unruptured IA associated with cortical SS. The possible source for leakages could be neovessels visible in IA walls. The case reported illustrates an uncommon presentation of recurrent bleeding from an IA as a source of SS. The presence of an apparently unruptured IA surrounded by cortical SS on imaging studies is of high relevance as this should be considered a sign of aneurysm wall instability and should indicate prompt treatment

Interventional magnetic-resonance-guided cryotherapy combined with microsurgery for recurrent glioblastoma: An innovative treatment?

Background: Glioblastoma invariably recurs after primary Stupp tumor therapy and portends a poor prognosis. Cryoablation is a well-established treatment strategy for extra-cranial tumors. The safety and efficacy of interventional MR-guided cryoablation (iMRgC) has not been explored in recurrent glioblastoma. Methods: A retrospective analysis of data collected over a period of 24 months was performed. The inclusion criteria were: (I) recurrent glioblastoma despite Stupp protocol; (II) MRI followed by histological confirmation of recurrent glioblastoma; (III) location allowing iMRgC followed by microsurgical resection; and (IV) patient's consent. The primary objective was to assess feasibility in terms of complications. The secondary objective was to analyze progression-free survival (PFS), post-iMRgC survival and overall survival (OS). Results: The study included 6 patients, with a mean age of 67 ± 7.6 years [range, 54–70 years]. No major complications were observed. Median PFS was 7.5 months [IQR 3.75–9.75] and 6-month PFS was 50%. Median post-iMRgC survival was 9 months [IQR 7.5–15.25] and 6-month post-iMRgC survival was 80%. Median OS was 22.5 months [IQR 21.75–30]. Conclusion: iMRgC for recurrent glioblastoma demonstrated a good safety profile, with no major complications. Our data suggest improved PFS and OS. Trial registration number: No. IRB00011687 retrospectively registred on July 7th 2021

Primary Brain Rhabdomyosarcoma Causing Extracranial Metastases: Case Report with Narrative Review of Atypical Presentations and Their Diagnostic Challenges

Background: Rhabdomyosarcoma is a rare malignant tumor originating from striated muscle cells. It accounts for only 3% of all soft tissue sarcomas in adults, and its metastases can also reach the central nervous system. Only sporadic cases of primary brain rhabdomyosarcoma (PBRMS) have been reported so far. Case Description: We discuss the atypical presentation and diagnostic challenge of PBRMS in a 65-year-old man. He presented with a 3-day history of progressive right hemiparesis caused by an unspecific left frontoparietal heterogeneously enhancing lesion. Total body computed tomography and positron emission tomography scans performed at baseline did not reveal other secondarisms. The patient underwent radical excision of the lesion, which allowed to establish the diagnosis, with immunohistochemical staining positive for desmin and myogenin. Stereotactic radiotherapy guaranteed local disease control; nonetheless, the patient also required adjuvant chemotherapy when he developed large right lung metastases 6 months postoperatively. Conclusions: PBRMS can be hardly distinguished from other malignant brain tumors during preoperative radiologic workup; only histology can raise the suspicion of primary or metastatic rhabdomyosarcoma, depending on the presence of other distant lesions. Our review of the literature demonstrates that prognosis is poor: 44% of patients die within 1 year from diagnosis. Overall, survival seems to correlate with radical resection, tolerance of stereotactic or if necessary full neuraxis radiotherapy, and adjuvant chemotherapy. Given the high relapse rate, close monitoring and restaging are imperative