The oxidation resistance of Ni-Co-Cr-Al-W-Mo-Ta-Re-Ru alloys is evaluated by cyclic oxidation at 1100 °C and modelled using an artificial neural network. The database required for the modelling was ...constructed using design of experiment (the Box-Behnken method) followed by oxidation experiments. The obtained model with a 7-10-1 architecture exhibits consistent prediction of the experimental data (R = 0.999). Cr and Al enhance the oxidation resistance by promoting the formation of a protective NiAl2O4 layer. Mo and Ru are detrimental to the oxidation resistance. W, Ta and Re exhibit complex behaviours depending on the contents of other alloying elements.
•Oxidation resistance of Ni-base alloys is modelled in Cr-Mo-W-Al-Ta-Re-Ru space.•By using Box-Behnken design, the number of samples to create database drops to 62.•The obtained neural network model has a 7-10-1 architecture and R = 0.999.•Mo and Ru deteriorate the oxidation resistance by forming oxide nodules.•W and Re are not as harmful as Mo and Ru to the oxidation resistance.
Objective/Hypothesis
To characterize the pathology and outcomes of skull base surgery in the pediatric population by open versus endoscopic surgical approach.
Study Design
Retrospective cohort study.
...Methods
A retrospective review of pediatric patients (<18 years) who underwent skull base surgery for nonmalignant disease from May 2000 to August 2019 was performed. Patient demographics, pathology, and operative characteristics by surgical approach were recorded and analyzed. Patients with a combined endoscopic/open approach were classified as open for the analysis.
Results
Eighty‐two pediatric skull base patients were identified with a mean age of 11.3 years (standard deviation 5.2). A purely endoscopic approach was used in 63 (77%) patients, a purely open approach was used in nine (11%) patients, and a combined open/endoscopic approach was used in 10 (12%) patients. The all‐cause complication rate was 9.8%. There was no statistically significant difference in rate of complications between patients with an open versus endoscopic approach for resection (15.8% vs. 7.9%; P = .379). Risk of having a complication did not significantly vary by patient age. The odds of having a complication with an open approach was not statistically significant in a multivariable model adjusted for age, sex, race, intraoperative cerebrospinal fluid leak, tracheostomy requirement, and vascular flap use (odds ratio 2.76, 95% confidence interval 0.28–26.94; P = .383).
Conclusions
Our retrospective study demonstrates a similar risk of complication for open versus endoscopic approach to resection in pediatric skull base patients at our institution. Safety and feasibility of the endoscopic approach has previously been demonstrated in children, and this is the first study to directly compare outcomes with open approaches.
Level of Evidence
4 Laryngoscope, 131:996–1001, 2021
Abstract
Chordomas are rare tumors of the axial skeleton that are refractory to conventional therapy. Few studies have compared the morphological and molecular characteristics of chordomas according ...to the skull base and sacral locations. Histopathological data and changes revealed by array comparative genomic hybridization (CGH) and next-generation sequencing (NGS) of cell cycle regulation genes were analyzed for 28 skull base (SBCs) and 15 sacral (SC) chordomas. All cases were conventional chordomas. SBCs were significantly more frequent in patients aged <40 years and SCs predominated in patients aged >60 years. Mitotic indices ≥2 mitoses/10 high-power fields were correlated with high degrees of nuclear atypia and Ki67 labeling indices ≥6%. We identified 321 genomic positions, and copy number variation losses were more frequent than gain. Moreover, we report a panel of 85 genetic variants of cell cycle genes and the presence of molecular clusters for chordoma as well in CGH as in NGS. These new data strengthen the view that the chordoma should not be considered as a single molecular entity.
The evolution of the Ω-phase dispersion during aging in an Al-5.6Cu-0.72Mg-0.5Ag-0.32Mn-0.17Sc-0.12Zr-0.1Ge-0.08Ti-0.02Fe-0.01Si (wt%) alloy was examined at the temperatures, T, of 200 and 250°C with ...dwelt times, τ, of 1.8–86.4 and 0.6–25.2ks, respectively. The precipitation sequence during aging can be written as SSSS→Ag-Mg clusters→Ω-phase+θ′-phase→θ-phase+Ag,Mg,Cu-enriched phases. Only a minor portion of Cu is consumed for the precipitation of the Ω-phase. Approximately 3.3wt% of Cu is retained in the solid solution after peak-aging. Therefore, the Ω-phase is a transition phase with a high free energy. The Ω-phase plates exhibit superior coarsening resistance. The kinetics of the coarsening is successfully predicted by the equation in a form of Ctt×τ0.2, where Ctt is a coefficient depending on aging temperature. Effect of aging on yield stress (YS) was analyzed in terms of additive sum of the contribution arising from the grain boundary strengthening, dislocation strengthening, solid solution strengthening and precipitation strengthening mechanisms. The contribution of the precipitate strengthening can be predicted satisfactorily by Nie and Muddle’s model of dislocation shearing of the {111}α plates. It was shown that the Ω-phase is a most efficient strengthening agent in the Al-Cu-Mg(-Ag) alloys and gives the major contribution to the overall YS. It is attributed to high efficiency of interfacial strengthening and high number density of the Ω-phase plates.
To survive in the current business environment, a firm must embrace ‘innovation’ in its overall business strategies. While scholars have investigated drivers of firms’ innovation performance, the ...concentration of a firm’s supply base and its potential link to innovation performance remains unexplored. We draw on the Knowledge-Based View (KBV) and the power asymmetry literature to propose that supply base concentration influences a firm’s innovation performance non-linearly, and that structure of the supply base in terms of breadth, depth, and geographical dispersion, and nature of the supply base in terms of collaboration moderate this relationship. Using data from 185 firms spanning six years and eleven industry sectors and implementing a robust empirical procedure that accounts for endogeneity and unobserved firm-level heterogeneity, we find that supply base concentration has an inverted U-shaped relationship with innovation performance. Moreover, breadth positively and geographical dispersion negatively influence this relationship. The results also show that supply base collaboration strengthens the relationship between concentration and innovation performance. Through multiple post hoc analyses, we also show partial empirical evidence of the theoretical mechanisms we propose. We contribute to the extant literature on supplier management, innovation performance, and the structure of the supply base.
•The oxidation of three high-entropy alloys was studied in dry air at 700–900°C.•The oxidation kinetics of all the alloys followed the parabolic rate law.•Multiple scales formed on the alloys were ...strongly composition-dependent.
The oxidation of three quinary equimolar high-entropy alloys, containing FeCoNiCrAl, FeCoNiCrMn, and FeCoNiCrSi was studied in dry air at 700–900°C. The Mn-containing alloy was single-phase, while both Al- and Si-containing alloys were dual-phase. The oxidation kinetics of all the alloys followed the parabolic rate law, regardless of temperature and alloy composition. The oxidation rates of both Al- and Si-containing alloys were lower than those of the quaternary FeCoNiCr alloy, while those of the Mn-containing alloy went to an opposite direction. Multiple scales formed on the alloys were strongly composition-dependent.
From the reaction of ceftriaxone 1 antibiotic with 2,6-diaminopyridine 2 a ceftriaxone-based Schiff base (H2L,3) was obtained and its transition metal complexes were synthesized. Spectroscopic and ...physicochemical techniques, namely, UV–visible, FT-IR, 1H NMR, EPR, mass spectrometry, molar conductance, magnetic susceptibility and density functional theory (DFT) calculations, together with elemental and thermal analyses, were used to find out the binding mode and composition of these complexes. The ceftriaxone-based Schiff base 3 behaves as a monoanionic tridentate N,N,O ligand. Spectral and magnetic data suggest an octahedral geometry for all complexes and the general formulae M(HL)(OAc)(H2O)2 (M(II) = Mn2+4, Co2+5, Ni2+6, Cu2+7, Zn2+8), are proposed for them. All compounds were screened for antibacterial activity using both the agar disc diffusion method and the minimal inhibitory concentration (MIC). It was found that complex 8 exhibited the most promising bactericidal activity against S. aureus (MIC = 0.0048 μmol/ml) and E. coli (MIC = 0.0024 μmol/ml). It is more active than the free ligand 1 (MIC = 0.0560 μmol/ml for S. aureus and 0.0140 μmol/ml for E. coli). These MIC results were compared with those obtained using similar zinc(II) Schiff base complexes, and with the values obtained using ceftriaxone conjugated with silver and gold nanoparticles (NPs), using earlier published data. Synthesized metal complexes exhibited LC50 values >1000 ppm indicating their nontoxicity against brine shrimp nauplii (Artemia Salina).
From the reaction of ceftriaxone 1 with 2,6−diaminopyridine 2 a N,N,O tridentate ceftriaxone−based Schiff base 3 was obtained. Novel transition metal complexes 4−8 containing 3 were synthesized, characterized and tested for toxicity and antibacterial activity. E. coli and S. aureus are very sensitive to zinc(II) complex 8. Display omitted
•A new polydentate Schiff base using ceftriaxone and 2,6-diaminopyridine was prepared.•Metal complexes with a ceftriaxone-derived Schiff base were prepared and characterized.•Zinc(II) complex showed better antibacterial activity against E. coli and S. aureus.
A π‐conjugated Lewis base is introduced into perovskite solar cells, namely, indacenodithiophene end‐capped with 1.1‐dicyanomethylene‐3‐indanone (IDIC), as a multifunctional interlayer, which ...combines efficient trap‐passivation and electron‐extraction. Perovskite solar cells with IDIC layers yield higher photovoltages and photocurrents, and 45% enhanced efficiency compared with control devices without IDIC.
Anterior skull base meningioma produces symptoms as a result of mass effect and neurovascular compression. The bony anatomy of the anterior skull base is complex and houses the critical cranial ...nerves and vessels. Traditional microscopic approaches remove these tumors effectively but require extensive brain retraction and bone drilling. Endoscope assistance offers the advantages of a smaller incision, less brain retraction, and bone drilling. The most significant advantage of endoscope-assisted microneurosurgery for lesions invading the sella and optic foramen is the complete resection of the sellar and foraminal components frequently responsible for recurrence.
In this report, we describe the technique of endoscope-assisted microneurosurgical resection of anterior skull base meningiomas invading the sella and foramen.
We present 10 cases and 3 case examples of endoscope-assisted microneurosurgery for meningiomas invading the sella and optic foramen. This report presents the operating room setup and surgical details to resect sellar and foraminal tumors. The surgical procedure is presented as a video.
Endoscope-assisted microneurosurgery yielded excellent clinical and radiologic results and no recurrence at the last follow-up of meningiomas invading the sella and optic foramen. The present article discusses the challenges faced with endoscope-assisted microneurosurgery, techniques, and challenges in the procedure.
Endoscope assistance enables complete tumor excision under vision with less retraction and bone drilling in anterior cranial fossa meningioma, invading the chiasmatic sulcus, optic foramen, and sella. The mixed use of microscope and endoscope makes it safer and saves time and is like bringing out the best of both worlds.
Intracranial meningiomas are a diverse group of tumors, which vary by grade, genetic composition, location, and vasculature. Expanding the understanding of the supply of skull base (SBMs) and ...non-skull base meningiomas (NSBMs) will serve to further inform resection strategies. We sought to delineate the vascular supply of a series of intracranial meningiomas by tumor location.
A retrospective study of intracranial meningiomas that were studied using preoperative digital subtraction angiograms before surgical resection at a tertiary referral center was performed. Patient, tumor, radiologic, and treatment data were collected, and regression models were developed.
One hundred sixty-five patients met inclusion criteria. The mean age was 57.1 years (SD: 12.6). The mean tumor diameter was 4.9 cm (SD: 1.5). One hundred twenty-six were World Health Organization Grade I, 37 Grade II, and 2 Grade III. Arterial feeders were tabulated by Al-Mefty's anatomic designations. SBMs were more likely to derive arterial supply from the anterior circulation, whereas NSBMs were supplied by external carotid branches. NSBMs were larger (5.61 cm vs 4.45 cm, P = <.001), were more often presented with seizure (20% vs 8%, P = .03), were higher grade ( P = <.001) had more frequent peritumoral brain edema (84.6% vs 66%, P = .04), and had more bilateral feeders (47.7% vs 28%, P = .01) compared with SBMs. More arterial feeders were significantly associated with lower tumor grade ( P = .023, OR = 0.59). Higher tumor grade (Grade II/III) was associated with fewer arterial feeders ( P = .017, RR = 0.74).
Meningioma location is associated with specific vascular supply patterns, grade, and patient outcomes. This information suggests that grade I tumors, especially larger tumors, are more likely to have diverse vascular supply patterns, including internal carotid branches. This study may inform preoperative embolization and surgical considerations, particularly for large skull base tumors.
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