Publications

Nickel Complexes with Bis(8-quinolyl)silyl Ligands. An Unusual Ni₃Si₂ Cluster Containing Six-Coordinate Silicon

Efforts to install the bis(8-quinolyl)methylsilyl (Me-NSiN; 1 = Me-NSiNH) and bis(8-quinolyl)phenylsilyl (Ph-NSiN; 2 = Ph-NSiNH) ligands onto nickel are described. Reaction of 1 with NiCl2(DME) and NiPr2Et afforded [(iPr2EtNH)2Cl][(QnH)NiCl3] (3; Qn = quinolyl) via degradation of the silane. Reaction of 2 with Ni(COD)2 in chlorobenzene yielded [Ph-NSiN]2Ni3Cl2 (5), which is a rare example of a silylnickel cluster with a [Ni3Si2] core. An X-ray structure determination reveals the presence of a triangular Ni3 core with two face-capping silyl groups: one that is bonded symmetrically to the three nickel atoms, while the other is unsymmetrically bound. The bonding in 5 has been investigated by computational methods to obtain descriptions of the molecular orbitals. The unsymmetrical bonding of Si(1) results from a two-electron bonding interaction with Ni(1), and this explains the short Si(1)−Ni(1) contact (2.2688(6) Å). The symmetrical bonding of Si(2) appears to result from its interaction with a delocalized Ni3 skeletal orbital. Complex 5 slowly decomposes in dichloromethane-d2 to (PhClSiQn2)NiCl (6), a Ni(I) chloride complex in which the phenyl group is bonded to the nickel with an intramolecularly coordinated (silyl)arene ligand. The η2-coordination of the aryl group involves interaction of ipso and ortho carbon atoms with the metal center. Theoretical studies of 6 support a very weak Ni−Si interaction (2−3 kcal/mol at the NBO level) that is supported by the arene coordination. The strength of the η2-coordination of the arene was estimated at the second-order donor−acceptor NBO level to be 25 kcal/mol.

Overcoming insomnia: protocol for a large-scale randomised controlled trial of online cognitive behaviour therapy for insomnia compared with online patient education about sleep

Introduction Insomnia is a major public health concern. While cognitive behaviour therapy for insomnia (CBT-I) is acknowledged as the best available intervention, there are unanswered questions about its wider dissemination, socioeconomic benefits and its impact on health resource utilisation. The aim of this randomised controlled trial (RCT) is to investigate the effectiveness of a fully automated online version of CBT-I compared with online patient education about sleep (PE). Outcome measures comprise changes in symptoms of insomnia, time off work due to sick leave as well as medication and health resource utilisation. Also, we will examine (i) putative mediators of the effects of CBT-I on insomnia severity and (ii) selected potential psycho-bio-social moderators of the effects of the interventions. Methods and analysis A parallel-group RCT will be conducted in a target sample of about 1500 adults recruited across Norway. Participants will complete an online screening and consent process. Those who meet eligibility criteria will be randomised to receive direct access to fully automated online CBT-I or to an online PE programme. The primary outcome is change in insomnia severity immediately postintervention; secondary outcomes are change in daytime functioning and other sleep measures postintervention and at 6-month and 24-month follow-up. Objective data from national registries will be obtained at two time points (1 year and 2 years post-treatment), allowing a mirror image study of preintervention and postintervention rates of sick leave, and of medication and healthcare utilisation by condition. Ethics and dissemination The study protocol was approved by the Regional Committee for Medical and Health Research Ethics in South East Norway (2015/134). Findings from the RCT will be disseminated in peer-reviewed publications and conference presentations. Exploratory analyses of potential mediators and moderators will be reported separately. User-friendly outputs will be disseminated to patient advocacy and other relevant organisations. Trial registration number NCT02558647 ; Pre-results.

Effects of Support Composition and Pretreatment Conditions on the Structure of Vanadia Dispersed on SiO₂, Al₂O₃, TiO₂, ZrO₂, and HfO₂

Spectroscopic techniques (X-ray absorption, Raman, and UV−visible) were utilized to monitor the effect of adsorbed water, calcination temperature, and reduction in H2 on the structure of dispersed VOx for vanadia supported on SiO2, Al2O3, TiO2, ZrO2, and HfO2 prepared with VOx surface densities ranging from 0.46 VOx/nm2 to 11.1 VOx/nm2. Supported vanadia was found to exist as monovanadate, polyvanadate, or V2O5 species, the distribution among these species depending on the support for a given VOx surface density. Dehydration resulted in the appearance of monovanadate species on all supports, with the extent of these species decreasing in the order HfO2 > Al2O3 > ZrO2 > TiO2 > SiO2. Hydration of the samples caused a decrease in the monovanadate species and a slight increase in polyvanadate species. Oxidation at elevated temperature resulted in an increase in the crystallinity of V2O5 present on SiO2, a conversion of V2O5 into polyvanadate species on Al2O3, and the appearance of mixed-metal oxide phases on TiO2, ZrO2 (ZrV2O7), and HfO2 (HfV2O7). The appearance of an interaction between vanadia and titania coincides with the transformation from anatase to rutile TiO2. ZrV2O7 and HfV2O7 are postulated to form via the interaction of surface VOx species with the support as the support begins to undergo a phase transition from tetragonal to monoclinic. H2 reduction produced limited changes in the structure of dispersed vanadia except on Al2O3, where V2O5 was transformed into polyvanadate species.

Exact decomposition of a Gaussian-averaged nonlinear function

We derive an exact formula for the decomposition of Gaussian spatially averaged experimental data. The true nonlinear functional dependence of a physical parameter on the local light intensity can be obtained.

Earthquake Response of Elastic Single-Degree-of-Freedom Systems with Nonlinear Viscoelastic Dampers

Investigated are the steady-forced and earthquake responses of single-degree-of-freedom (SDF) systems with a nonlinear viscoelastic damper (VED), which consists of a nonlinear fluid viscous damper (FVD) connected in series to a linear elastic bracing element (chevron or inverted V-shaped braces). For a wide range of bracing stiffness, nonlinear dampers are advantageous because they achieve essentially the same reduction in system responses but with a significantly reduced force. Damper nonlinearity has little influence on the structural response in the velocity-sensitive region of the spectrum even if the bracing is fairly flexible, but differences up to 16% were observed in other spectral regions. As expected, supplemental damping reduces structural response and the response reduction depends on the bracing stiffness, with this dependence varying with the spectral regions. For practical applications, a procedure is presented to estimate the design values of structural deformation, structural force, foundation shear, and damper force directly from the earthquake design (or response) spectrum. Finally, a procedure is presented to determine the damper and bracing properties necessary to limit the structural deformation to some design value or to the structural capacity.

CCDC 950762: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Evaluation of Infill Drilling Opportunities in Lekhwair Field, Oman

Abstract This paper presents an evaluation of infill drilling opportunities in a mature waterflood. Different infill drilling configurations for increased oil recovery are compared using a ranking scheme. The field has been on production since 1976. The field has a complex development history, with periods of primary recovery, shut-in, 5-spot, inverted 9-spot, and direct line-drive waterflood. The field is currently undergoing a linedrive waterflood. The challenge is to find new infill drilling opportunities and determine optimal well spacing to maximize oil production. Traditional infill drilling evaluations either use empirical techniques based on ad-hoc esimates of drainage areas or reservoir simulation of the field-level benefits of an infill drilling program. The former approach ignores the impact of reservoir heterogeneities while the latter approach makes it difficult to evaluate the contribution that each infill well makes to the field-level benefit. Our approach isolates the impact of each infill well and provides a fast and novel methodology to evaluate the incremental benefit while accounting for reservoir heterogeneity, well conditions, pattern configuration, injection rates, and voidage replacement ratio. This type of analysis helps optimize the number of wells to be drilled and at the same time leads to increased oil recovery through better waterflood management. Streamline analysis was used to identify dead spots and regions of unswept oil in a part of the field. A novel waterflood management workflow was used to evaluate new infill well configuration strategies to increase oil recovery and better manage the waterflood. Optimization studies were also conducted to minimize the number of wells with the right combination of injectors and producers and obtain significant incremental benefits. Work is underway in the field to implement these recommendations and early results point to the success of this approach. This paper presents a novel approach for evaluating the impact of infill drilling. The marginal utility of each infill well is calculated and then is used to optimize the number of wells and maximize oil recovery. The approach presented can be used to quantify the impact of infill drilling and increase oil rate and recovery in similar reservoirs.

Mechanical and friction properties of thermoplastic polyurethanes determined by scanning force microscopy

The mechanical and friction properties of additive-free polyurethane (PUR) consisting of polyether soft segments of polytetramethyleneoxide and hard segments (HS) comprising 4,4'-diphenylmethane diisocyanate and 1,4-butanediol as a chain extender were studied by scanning force microscopy. The hardness and elastic modulus of PUR containing 42, 57, 69, and 100 wt % HS were determined from nanoindentation experiments performed with a diamond tip of nominal radius of curvature equal to ∼20 μm and maximum indentation load in the range of 10–500 μN. The mechanical properties of PUR were found to strongly depend on the HS content and contact load. The elastic modulus of PUR with 42 wt % HS was found to decrease with increasing load due to the high softness of this material that influenced the measurements. The friction characteristics of the samples with 42, 57, and 69 wt % HS were studied in order to evaluate the dependence of the coefficient of friction on load and sliding speed. The PUR with 57 wt % HS exhibited the lowest coefficient of friction. Depending on the PUR composition, remarkably different friction behaviors were obtained. The observed mechanical behavior and friction characteristics are interpreted in terms of the chemical composition and microstructure of the samples.

Fatigue and Fracture of Small Cracks in Superelastic Nitinol

The present study develops a hybrid total life and damage tolerance fatigue methodology for the determination of a small crack growth threshold in Nitinol. Axial tension-tension/Mode I fatigue testing was performed on superelastic Nitinol wire specimens with starter cracks milled into the specimens using focused-ion-beam (FIB). Fatigue testing was performed in displacement control at various strain amplitudes as is typical with Nitinol fatigue given its superelastic properties. The simplistic geometry of the test specimen and axial loading conditions also allowed for the calculation of stress amplitude and initial stress intensity factor range. A logistic regression analysis was used to determine strain/stress-based fatigue limits. The small crack growth threshold for superelastic Nitinol was obtained for the first time from physically small cracks with sizes comparable to native inclusions. Lastly, a fractographic analysis was performed to examine crack initiation and propagation from the FIB-milled starter cracks and to identify relevant fractographic features. While the proposed methodology is centered around the use case of Nitinol medical devices, it could be adapted for other materials and applications where small crack initiation and propagation play an important role in fatigue lifetime prediction.

Polymeric reagents. IX Use of a polysterene-based amine oxide as a regenerable oxidizing agent for alkyl halides

(Invited) Synthesizing Cathode Precursors Directly from Lithium Ores

Abstract: With the increasing demand of lithium (Li) used for energy storage, there is a need for diversified Li sources beyond brines. Among the minerals that can satisfy this need, spodumene is most often used for its high Li content and natural abundance. However, the traditional approach to process spodumene is costly and energy-intensive, requiring that the mineral be transformed from its naturally occurring α phase into the more reactive β phase at temperatures exceeding 1000 °C [1, 2]. Acid leaching is then used to extract Li, followed by neutralization to precipitate Li in the form of Li 2 CO 3 , a common precursor for the synthesis of Li-ion battery cathodes. Recently, we have developed an improved procedure to extract Li directly from α-spodumene, which can be performed at lower temperatures and avoids the use of acids. Li 2 CO 3 can be formed with > 90% yield at 750 °C by reacting α-spodumene with inexpensive additives. Following its extraction from spodumene, Li 2 CO 3 can be isolated with high purity by washing the sample using deionized water [3]. The Li extraction process introduced above presents a low-energy and acid-free route to obtain Li 2 CO 3 directly from spodumene, thereby fostering a more sustainable and efficient utilization of natural minerals to produce precursors that are essential for battery industry. We will also demonstrate how the in-situ formation of Li 2 CO 3 opens new opportunities for the direct synthesis of battery materials from raw ores (α-spodumene). References: [1] Karrech, A., et al., A review on methods for liberating lithium from pegmatities, Minerals Engineering , 2020. 145 . [2] Yelatontsev, D. and Mukhachev A., Processing of lithium ores: Industrial technologies and case studies – A review, Hydrometallurgy , 2021. 201 . [3] Shilong, W., Nathan, S., et al., Direct lithium extraction from α-spodumene through solid-state reactions for sustainable Li 2 CO 3 production, under review .

CCDC 1864492: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The Measurement of Bacterial Growth

Type 2 diabetes impairs annulus fibrosus fiber deformation and rotation under disc compression in the University of California Davis type 2 diabetes mellitus (UCD-T2DM) rat model

Understanding the biomechanical behavior of the intervertebral disc is crucial for studying disease mechanisms and developing tissue engineering strategies for managing disc degeneration. We used synchrotron small-angle X-ray scattering to investigate how changes to collagen behavior contribute to alterations in the disc’s ability to resist compression. Coccygeal motion segments from 6-month-old lean Sprague-Dawley rats ( n=7) and diabetic obese University of California Davis type 2 diabetes mellitus (UCD-T2DM) rats ( n=6, diabetic for 68±7 days) were compressed during simultaneous synchrotron scanning to measure collagen strain at the nanoscale (beamline 7.3.3 of the Advanced Light Source). After compression, the annulus fibrosus was assayed for nonenzymatic cross-links. In discs from lean rats, resistance to compression involved two main energy-dissipation mechanisms at the nanoscale: (1) rotation of the two groups of collagen fibrils forming the annulus fibrosus and (2) straightening (uncrimping) and stretching of the collagen fibrils. In discs from diabetic rats, both mechanisms were significantly impaired. Specifically, diabetes reduced fibril rotation by 31% and reduced collagen fibril strain by 30% (compared to lean discs). The stiffening of collagen fibrils in the discs from diabetic rats was consistent with a 31% higher concentration of nonenzymatic cross-links and with evidence of earlier onset plastic deformations such as fibril sliding and fibril–matrix delamination. These findings suggest that fibril reorientation, stretching, and straightening are key deformation mechanisms that facilitate whole-disc compression, and that type 2 diabetes impairs these efficient and low-energy elastic deformation mechanisms, thereby altering whole-disc behavior and inducing the earlier onset of plastic deformation.

Matching shapes

We present a novel approach to measuring similarity between shapes and exploit it for object recognition. In our framework, the measurement of similarity is preceded by (1) solving for correspondences between points on the two shapes, (2) using the correspondences to estimate an aligning transform. In order to solve the correspondence problem, we attach a descriptor, the shape context, to each point. The shape context at a reference point captures the distribution of the remaining points relative to it, thus offering a globally discriminative characterization. Corresponding points on two similar shapes will have similar shape contexts, enabling us to solve for correspondences as an optimal assignment problem. Given the point correspondences, we estimate the transformation that best aligns the two shapes; regularized thin-plate splines provide a flexible class of transformation maps for this purpose. Dis-similarity between two shapes is computed as a sum of matching errors between corresponding points, together with a term measuring the magnitude of the aligning transform. We treat recognition in a nearest-neighbor classification framework. Results are presented for silhouettes, trademarks, handwritten digits and the COIL dataset.

Urban Marginality in the Coming Millennium

This paper sketches a characterisation of the regime of urban marginality that has emerged in advanced societies since the close of the Fordist era, highlighting four logics that combine to produce it: a macrosocietal drift towards inequality, the mutation of wage labour (entailing both deproletarianisation and casualisation), the retrenchment of welfare states, and the spatial concentration and stigmatisation of poverty. The rise of this new marginality does not signal a transatlantic convergence on the American pattern: European neighbourhoods of relegation are deeply penetrated by the state and ethnoracial tensions in them are fuelled, not by the growing gap between immigrants and natives, but by their increasing propinquity in social and physical space. To cope with emergent forms of urban marginality, societies face a three-pronged alternative: they can patch up existing programmes of the welfare state, criminalise poverty via the punitive containment of the poor, or institute new social rights that sever subsistence from performance in the labour market.

Flow Control Valves for Analytical Microfluidic Chips without Mechanical Parts Based on Thermally Responsive Monolithic Polymers

Monolithic plugs of poly(N-isopropylacrylamide) cross-linked with 5% methylenebisacrylamide have been prepared by photoinitiated polymerization within the channel of a microfluidic device. The volume change associated with the polymer phase transition at its lower critical solution temperature of 32 degrees C allows both the rapid swelling and the deswelling of the monoliths enabling the polymer to close or open the channel as it functions as a nonmechanical valve. Thermoelectric elements capable of changing the temperature of the system between 17 and 57 degrees C were used to actuate the valve. Flow through the device was monitored by fluorescence measurements via the laser-triggered photobleaching of a dye contained in the liquid phase. Photobleaching occurs quickly once the flow is stopped, and the time required to open and close the valve was 3.5 and 5.0 s, respectively. No changes in function were observed even after 120 open-close cycles. Although the 2-mm-long valve was prepared from a polymerization mixture consisting of only a 5% aqueous solution of monomers, it resists pressures of up to 1.38 MPa (200 psi) without observable structural damage.

Reticular Synthesis of Covalent Organic Borosilicate Frameworks

This paper reports the synthesis and characterization of a new crystalline 3D covalent organic framework, COF-202: [C(C6H4)4]3[B3O6 (tBuSi)2]4, formed from condensation of a divergent boronic acid, tetra(4-dihydroxyborylphenyl)methane, and tert-butylsilane triol, tBuSi(OH)3. This framework is constructed through strong covalent bonds (Si-O, B-O) that link triangular and tetrahedral building units to form a structure based on the carbon nitride topology. COF-202 demonstrates high thermal stability, low density, and high porosity with a surface area of 2690 m2 g-1. The design and synthesis of COF-202 expand the type of linkage that could be used to crystallize new materials with extended covalent organic frameworks.