Differences in Molecular Adsorption Emanating from the (2 × 1) Reconstruction of Calcite(104).

Calcite, in the natural environment the most stable polymorph of calcium carbonate (CaCO3), not only is an abundant mineral in the Earth's crust but also forms a central constituent in the biominerals of living organisms. Intensive studies of calcite(104), the surface supporting virtually all processes, have been performed, and the interaction with a plethora of adsorbed species has been studied. Surprisingly, there is still serious ambiguity regarding the properties of the calcite(104) surface: effects such as a row-pairing or a (2 × 1) reconstruction have been reported, yet so far without physicochemical explanation. Here, we unravel the microscopic geometry of calcite(104) using high-resolution atomic force microscopy (AFM) data acquired at 5 K combined with density functional theory (DFT) and AFM image calculations. A (2 × 1) reconstruction of a pg-symmetric surface is found to be the thermodynamically most stable form. Most importantly, a decisive impact of the (2 × 1) reconstruction on adsorbed species is revealed for carbon monoxide.

Spontaneous Regression of a Symptomatic Cyst of the Cavum Septi Pellucidi and Vergae.

Spontaneous regression of cysts of the cavum septi pellucidi (CSP) and cavum vergae (CV) is rare and little discussed. The authors present their case report of this phenomenon following a severe headache in a 23-year-old woman, in whom magnetic resonance imaging (MRI) had previously confirmed significant thinning of the left lateral cyst wall. We consider this finding to be a possible predisposing factor to rupture and the spontaneous regression of such cysts. In addition to the mechanism of cyst regression, the interrelated causes of their expansion and formation will be discussed.

On-surface synthesis of disilabenzene-bridged covalent organic frameworks.

Substituting carbon with silicon in organic molecules and materials has long been an attractive way to modify their electronic structure and properties. Silicon-doped graphene-based materials are known to exhibit exotic properties, yet conjugated organic materials with atomically precise Si substitution have remained difficult to prepare. Here we present the on-surface synthesis of one- and two-dimensional covalent organic frameworks whose backbones contain 1,4-disilabenzene (C4Si2) linkers. Silicon atoms were first deposited on a Au(111) surface, forming a AuSix film on annealing. The subsequent deposition and annealing of a bromo-substituted polyaromatic hydrocarbon precursor (triphenylene or pyrene) on this surface led to the formation of the C4Si2-bridged networks, which were characterized by a combination of high-resolution scanning tunnelling microscopy and photoelectron spectroscopy supported by density functional theory calculations. Each Si in a hexagonal C4Si2 ring was found to be covalently linked to one terminal Br atom. For the linear structure obtained with the pyrene-based precursor, the C4Si2 rings were converted into C4Si pentagonal siloles by further annealing.

Does Endoscopic Transnasal Optic Nerve Decompression Followed by Radiosurgery Improve Outcomes in the Treatment of Parasellar Meningiomas?

INTRODUCTION: The clinical management of parasellar meningiomas (PM) is challenging due to their intimate association with critical neurovascular structures. Consensus regarding the recommended treatment protocol is lacking. This study will evaluate patients' visual outcomes following endoscopic transnasal optic nerve decompression (ETOND) and will investigate the possibility of reducing the rate of complications associated with stereotactic radiosurgery (SRS). METHODS: Retrospective analysis was conducted on all patients who underwent ETOND for PM between 2013 and 2020. The study comprised 12 patients (7 women and 5 men aged 36-75 years; mean, 55.2 years; median, 57.6 years) in which 14 optic nerve decompression procedures were carried out. Patients were followed up for 6 to 86 months (mean, 29.3 months; median, 25 months). There were five cases of spheno-orbital meningioma, four cases of cavernous sinus meningioma, and one case each of petro-clival meningioma, optic nerve sheath meningioma, and planum sphenoidale/tuberculum sellae meningioma. Visual outcome was evaluated and any postoperative complications noted. RESULTS: Improvements in visual acuity were noted in 10 of 14 eyes (71.4%) 3 to 6 months postoperation. Visual acuity remained stable in the remaining four eyes. No deterioration of visual acuity was noted during the follow-up period. In total, 9 of the 12 patients underwent SRS. No tumor growth was determined, while reduction in tumor volume was noted in five patients following SRS. No complications associated with SRS or the surgical procedure were noted. CONCLUSIONS: ETOND appears to be a promising technique for increasing rates of improved visual function, while reducing the risk of post SRS-related complications. In combination with subsequent SRS, it is an ideal treatment modality in the management of parasellar meningiomas. Confirmation of our findings would require a larger, prospective multicenter study.

Electrostatic Discovery Atomic Force Microscopy.

While offering high resolution atomic and electronic structure, scanning probe microscopy techniques have found greater challenges in providing reliable electrostatic characterization on the same scale. In this work, we offer electrostatic discovery atomic force microscopy, a machine learning based method which provides immediate maps of the electrostatic potential directly from atomic force microscopy images with functionalized tips. We apply this to characterize the electrostatic properties of a variety of molecular systems and compare directly to reference simulations, demonstrating good agreement. This approach offers reliable atomic scale electrostatic maps on any system with minimal computational overhead.

Biphenylene network: A nonbenzenoid carbon allotrope.

The quest for planar sp2-hybridized carbon allotropes other than graphene, such as graphenylene and biphenylene networks, has stimulated substantial research efforts because of the materials' predicted mechanical, electronic, and transport properties. However, their syntheses remain challenging given the lack of reliable protocols for generating nonhexagonal rings during the in-plane tiling of carbon atoms. We report the bottom-up growth of an ultraflat biphenylene network with periodically arranged four-, six-, and eight-membered rings of sp2-hybridized carbon atoms through an on-surface interpolymer dehydrofluorination (HF-zipping) reaction. The characterization of this biphenylene network by scanning probe methods reveals that it is metallic rather than a dielectric. We expect the interpolymer HF-zipping method to complement the toolbox for the synthesis of other nonbenzenoid carbon allotropes.

Hydrocephalus Caused by Primary Fourth Ventricle Outlet Obstruction: Our Experience and Literature Review.

OBJECTIVE: Primary fourth ventricle outlet obstruction (PFVOO) is a rare cause of hydrocephalus with an unclear etiopathogenesis, and thus, consensus regarding the recommended treatment protocol is lacking. This study aims to summarize current knowledge of this condition in the light of our own treatment experience. METHODS: Retrospective analysis was carried out of all patients treated for noncommunicating tetraventricular hydrocephalus between 2006 and 2019, from which a subgroup of patients with PFVOO was created. A literature review of PFVOO cases was also carried out. RESULTS: A total of 62 patients with PFVOO were discovered, of whom 8 were treated at our institution, representing 3.8% of our patients with noncommunicating hydrocephalus. Patients most commonly presented with headaches, gait disturbance, or symptoms of intracranial hypertension. The mean follow-up duration was 75.4 months among our patients and 29.9 months in the literature. Most patients (54.8%) were treated by endoscopic third ventriculostomy (ETV), with the remainder undergoing suboccipital craniotomy alone (17.7%) or in combination with shunt surgery (9.7%), or endoscopic magendieplasty (12.9%). Treatment failure was noted in 28.6% of ETVs and 9% of craniotomies. No failures were recorded after endoscopic magendieplasty. The risk of treatment failure was found to be significantly higher with ETV compared with other treatment modalities (P < 0.0005). CONCLUSIONS: Despite the fact that PFVOO can be defined as an obstructive hydrocephalus, there seems to be a higher risk of ETV failure in such cases. The alternative treatment modalities presented are still recommended. Confirmation of these findings requires a larger multicenter study.

Non-communicating hydrocephalus with a primary empty sella presenting with growth hormone deficiency and delayed puberty successfully treated by endoscopic third ventriculocisternostomy.

The authors present the unusual case of a 15-year-old boy with a primary empty sella caused by non-communicating hydrocephalus due to fourth ventricle outflow obstruction whose secondary symptoms of growth hormone deficiency and delayed puberty were successfully treated by endoscopic third ventriculocisternostomy (ETV). Hypopituitarism occurs only rarely in cases of hydrocephalus; rarer still are cases where hypopituitarism is the sole symptom of hydrocephalus. A primary empty sella may indicate elevated intracranial pressure; if the cause is non-communicating hydrocephalus, ETV is indicated as the preferred treatment modality.

Preparation, Thermal Analysis, and Mechanical Properties of Basalt Fiber/Epoxy Composites.

In this study, basalt fiber-reinforced polymer (BFRP) composites with epoxy matrix, 20 layers, and volume fraction of fibers Vf = 53.66%, were prepared by a hand lay-up compression molding combined method. The fabric of the basalt fibers is in twill 2/2 weave. Through dynamic mechanical analysis (DMA), their viscoelastic behavior at elevated temperatures and in various frequencies was explored, whereas thermomechanical analysis (TMA) took part in terms of creep recovery and stress-relaxation tests. Moreover, the glass transition temperature (Tg) of the BFRP composites was determined through the peak of the tanδ curves while the decomposition of the BFRP composites and basalt fibers, in air or nitrogen atmosphere, was explored through thermogravimetric analysis (TGA). The mechanical behavior of the BFRP composites was investigated by tensile and three-point bending experiments. The results showed that as the frequency is raised, the BFRP composites can achieve slightly higher Tg while, under the same circumstances, the storage modulus curve obtains a less steep decrease in the middle transition region. Moreover, the hand lay-up compression molding hybrid technique can be characterized as efficient for the preparation of polymer matrix composites with a relatively high Vf of over 50%. Remarkably, through the TGA experiments, the excellent thermal resistance of the basalt fibers, in the temperature range 30-900 °C, was revealed.

On-Surface Synthesis of a π-Extended Diaza[8]circulene.

Heterocyclic [8]circulenes are an important class of polycyclic aromatic hydrocarbon molecules because of their unique structural properties and promising applications. However, the synthesis of heterocyclic [8]circulenes is still limited and thus is an important synthetic challenge. Here we describe the first example of a π-extended diaza[8]circulene surrounded by and fused with six hexagons and two pentagons, which was successfully synthesized only by a combined in-solution and on-surface synthetic strategy. State-of-the-art scanning tunneling microscopy with a CO-functionalized tip and density functional theory calculations revealed its planar conformation and unique electronic structure.

Automated structure discovery in atomic force microscopy.

Atomic force microscopy (AFM) with molecule-functionalized tips has emerged as the primary experimental technique for probing the atomic structure of organic molecules on surfaces. Most experiments have been limited to nearly planar aromatic molecules due to difficulties with interpretation of highly distorted AFM images originating from nonplanar molecules. Here, we develop a deep learning infrastructure that matches a set of AFM images with a unique descriptor characterizing the molecular configuration, allowing us to predict the molecular structure directly. We apply this methodology to resolve several distinct adsorption configurations of 1S-camphor on Cu(111) based on low-temperature AFM measurements. This approach will open the door to applying high-resolution AFM to a large variety of systems, for which routine atomic and chemical structural resolution on the level of individual objects/molecules would be a major breakthrough.

Three-dimensional graphene nanoribbons as a framework for molecular assembly and local probe chemistry.

Recent advances in state-of-the-art probe microscopy allow us to conduct single molecular chemistry via tip-induced reactions and direct imaging of the inner structure of the products. Here, we synthesize three-dimensional graphene nanoribbons by on-surface chemical reaction and take advantage of tip-induced assembly to demonstrate their capability as a playground for local probe chemistry. We show that the radical caused by tip-induced debromination can be reversibly terminated by either a bromine atom or a fullerene molecule. The experimental results combined with theoretical calculations pave the way for sequential reactions, particularly addition reactions, by a local probe at the single-molecule level decoupled from the surface.

The role of third ventricle bowing in the success of endoscopic third ventriculostomy in pediatric and adult patients.

OBJECTIVE: Preoperative third ventricle deformation (known as 'bowing') is associated with higher endoscopic third ventriculostomy (ETV) success. In children, the effect of bowing has not to date been systematically studied. Aim of of this study is to determine the effect of bowing on ETV success in adult and child patients. PATIENTS AND METHODS: In this retrospective, monocentric study were included 135 (70 adults and 65 children) of 157 patients who underwent ETV between 2008-2016, with mean follow-up 4.3 years. Presence and extent of bowing and its impact on ETV outcome were evaluated. Third ventricular anatomy was assessed on pre- and postoperative MR imaging. RESULTS: In patients > 6 months old, the ETV success rate was 91% in bowing-positive cases and 47.6% in bowing-negative cases. Among patients < 6 months old, ETV was successful in 37% of those with bowing and 36.4% of those without. Presence of bowing strongly indicates ETV success in patients older than 6 months (p < 0.000 5), including children of 7 months and older (p 0.001). This relationship was not confirmed in pediatric patients up to 6 months old (p 1.000). The extent of bowing does not influence ETV success (p 0.559). Bowing correction strongly correlates with ETV success (p < 0.000 5). CONCLUSION: We confirmed significant correlation between bowing and ETV success in patients over 6 months old. This relationship was not determined in those younger than 6 months and therefore we do not recommend bowing in ETV indication criteria for this patient cohort.

Symptomatic cysts of the cavum septi pellucidi, cavum vergae and cavum veli interpositi: A retrospective duocentric study of 10 patients.

OBJECTIVE: Cysts of the Cavum septi pellucidi (CSP), cavum vergae (CV) and cavum veli interpositi (CVI) are anterior midline intracranial findings which are typically incidental - only rarely do we encounter symptomatic cysts of this type. Only a quite small number of these cysts series have been published, controversies regarding optimal management still exist. PATIENTS AND METHODS: This is a retrospective study of 10 patients treated at 2 clinics between 2002-2018. 9 patients underwent surgery and 1 is under long-term monitoring. Apart from demographic data, the study analyzed symptoms, cyst size and progression over time, ventricle size, complications, and treatment modality. RESULTS: CSP with CV was found in 8 cases with 1 case each of CSP and CVI. The study comprised 6 men and 4 women, including 4 children. The mean follow-up time was 43.4 months. The average cyst size was 20.4 mm in CSP and 19.8 mm in CV; the CVI was 33 mm. Headache was most commonly reported (70%) followed by behavioral disturbance (30%). Disturbance in memory, psychomotor development, school performance, visual acuity, and vomiting was variously noted in 20%. The prevailing symptom was headache in adults and behavioral and autonomic disturbance in children. Postoperatively, cysts had reduced by an average of 44.3% while the ventricles remained unchanged. Symptoms resolved in all cases with residual problems in patients presenting with memory loss. No complications were noted. CONCLUSION: Endoscopic fenestration is the method of choice in the treatment of symptomatic midline cysts. We recommend that any further research focuses on precisely establishing their clinical presentation, particularly neuropsychological symptoms.

Interface dipoles of Ir(ppy)3 on Cu(111).

The interplay of adsorption geometry and interface dipoles of the transition-metal complex Ir(ppy)3 on Cu(111) was studied using low-temperature scanning probe microscopy and density-functional-theory calculations. We find that the orientation of the molecule's intrinsic dipole moment with respect to the surface has a strong influence on the total energy of the different configurations, where the most stable one has the molecular dipole moment pointing out of the surface plane along the surface normal. Adsorption-induced redistribution of charges results in an additional dipole moment that also points out of the surface plane for all configurations. Submolecularly resolved maps of the resulting local contact potential difference suggest that any in-plane dipole moment is very effectively screened.

Brain abscess and pyocephalus: our experience with treatment.

INTRODUCTION: Pyocephalus always presents serious complications in the treatment of brain abscesses, and is associated with high rates of mortality and morbidity. This study aimed to comprehensively evaluate this understandably feared complication from a purely medical perspective by using an evidence-based approach and drawing comparisons from the available literature, which mostly comprises case reports. METHODS: This was a prospective monocentric study of all patients treated for brain abscesses at the Neurosurgery Clinic of the University Hospital Ostrava between 2012 and 2017. The cohort was divided into two groups for statistical comparison; one group comprised those in which pyocephalus occurred before or during treatment, while the other group comprised patients without this complication. Particular consideration was given to the effect of pyocephalus on morbidity and mortality rates and C-reactive protein levels, as well as to the identification of risk factors, and to its possible therapeutic influence. Patients were followed up for six months. RESULTS: A total of 43 patients were treated for a brain abscess. An unequivocal diagnosis of pyocephalus was established via CT and MRI brain scans in five cases (11.6%). In the cohort as a whole, mortality and morbidity rates were 23.3% and 48.8% respectively. Among patients with pyocephalus the incidence of mortality and morbidity was 40% and 66.6% respectively. The presence of pyocephalus is not a significant predictor of either morbidity (p 0.575) or mortality (p 0.664). In patients with pyocephalus, we determined elevated CRP levels on the day of surgery (p 0.038). The occurrence of epileptic seizures in the acute phase of the disease is associated with a poor outcome (p 0.039). CONCLUSIONS: Pyocephalus will continue to be a serious complication in the treatment of brain abscesses, although we were unable to determine its utility as a prognostic factor. Patients with this complication have elevated CRP levels on the day of operation.

Bonding Motifs in Metal-Organic Compounds on Surfaces.

The bonds in metal organic networks on surfaces govern the resulting geometry as well as the electronic properties. Here, we study the nature of these bonds by forming phenazine-copper complexes on a copper surface by means of atomic manipulation. The structures are characterized by a combination of scanning probe microscopy and density functional theory calculations. We observed an increase of the molecule-substrate distance upon covalent bond formation and an out-of-plane geometry that is in direct contradiction with the common expectation that these networks are steered by coordination bonds. Instead, we find that a complex energy balance of hybridization with the substrate, inhomogeneous Pauli repulsion, and elastic deformation drives the phenazine-copper interaction. Most remarkably, this attractive interaction is not driven by electron acceptor properties of copper but is of completely different donation/back-donation mechanism between molecular π-like orbitals and sp-like metal states. Our findings show that the nature of bonds between constituents adsorbed on surfaces does not have to follow the common categories.

Diacetylene Linked Anthracene Oligomers Synthesized by One-Shot Homocoupling of Trimethylsilyl on Cu(111).

On-surface chemical reaction has become a very powerful technique to conjugate small precursor molecules and several reactions have been proposed with the aim to fabricate functional nanostructures on surfaces. Here we present an unforeseen adsorption mode of 9,10-bis((trimethylsilyl)ethynyl)anthracene on a Cu(111)surface and the resulting one-shot desilylative homocoupling of of the adsorbate by annealing at 400 K. With a combination of high-resolution atomic force microscopy and density functional theory calculations, we found that the triple bonds and silicon atoms of the monomer chemically interact with the copper surface. After the oligomerization, we discovered that the anthracene units are linked to each other via buta-1,3-diynediyl fragments while keeping the surface clean. Furthermore, the force measurement revealed the chemical nature at the center of anthracene unit.

Non-covalent control of spin-state in metal-organic complex by positioning on N-doped graphene.

Nitrogen doping of graphene significantly affects its chemical properties, which is particularly important in molecular sensing and electrocatalysis applications. However, detailed insight into interaction between N-dopant and molecules at the atomic scale is currently lacking. Here we demonstrate control over the spin state of a single iron(II) phthalocyanine molecule by its positioning on N-doped graphene. The spin transition was driven by weak intermixing between orbitals with z-component of N-dopant (pz of N-dopant) and molecule (dxz, dyz, dz2) with subsequent reordering of the Fe d-orbitals. The transition was accompanied by an electron density redistribution within the molecule, sensed by atomic force microscopy with CO-functionalized tip. This demonstrates the unique capability of the high-resolution imaging technique to discriminate between different spin states of single molecules. Moreover, we present a method for triggering spin state transitions and tuning the electronic properties of molecules through weak non-covalent interaction with suitably functionalized graphene.