High-Spin Superatom Stabilized by Dual Subshell Filling.

Quantum confinement in small symmetric clusters leads to the bunching of electronic states into closely packed shells, enabling the classification of clusters with well-defined valences as superatoms. Like atoms, superatomic clusters with filled shells exhibit enhanced electronic stability. Here, we show that octahedral transition-metal chalcogenide clusters can achieve filled shell electronic configurations when they have 100 valence electrons in 50 orbitals or 114 valence electrons in 57 orbitals. While these stable clusters are intrinsically diamagnetic, we use our understanding of their electronic structures to theoretically predict that a cluster with 107 valence electrons would uniquely combine high stability and high-spin magnetic moment, attained by filling a majority subshell of 57 electrons and a minority subshell of 50 electrons. We experimentally demonstrate this predicted stability, high-spin magnetic moment (S = 7/2), and fully delocalized electronic structure in a new cluster, [NEt4]5[Fe6S8(CN)6]. This work presents the first computational and experimental demonstration of the importance of dual subshell filling in transition-metal chalcogenide clusters.

Improvement in vitamin B12 status of Wistar rats by supplementing the diet with Chlorella vulgaris biomass.

The sources of bioavailable vitamin B12 are limited, and most of them are animal-derived. Chlorella vulgaris, a freshwater microalga, is known for immune system boosting, nutraceutical properties and presence of a natural form of vitamin B12. The present study focused on the in vivo evaluation of the Chlorella biomass as a source of bioavailable vitamin B12 to alleviate the vitamin B12 deficiency status of Wistar rats. Experimental animals were evaluated for the vitamin B12 deficiency-related circulatory marker (serum vitamin B12) and functional markers (plasma homocysteine and urinary methylmalonic acid), haematological and histological changes. The results showed that an increase of 2.4-fold in urinary methylmalonic acid (13.01 ± 0.89 µmoles moles of creatinine-1), 2.6-fold in plasma homocysteine (17.18 ± 3.57 µmole L-1), and 48% decrease in serum vitamin B12 levels (252.69 ± 1.46 pg mL-1) in vitamin B12 deficient group compared to control animals. The Chlorella biomass supplementation in the diet led to the restoration of the functional and circulatory markers, hematological parameters, and vitamin B12 content of kidney and liver to control levels. The Chlorella biomass supplementation increased the erythrocyte precursors and MAST cells in the bone marrow and also normalized the histological features of kidney, liver, and lung tissues. The results suggest that the vitamin B12 from the Chlorella biomass was bioavailable and facilitated the improvement of vitamin B12 status in deficient rats.

Comparative life cycle assessment of autotrophic cultivation of Scenedesmus dimorphus in raceway pond coupled to biodiesel and biogas production.

Life cycle assessment (LCA) of indigenous freshwater microalgae, Scenedesmus dimorphus, cultivation in open raceway pond and its conversion to biodiesel and biogas were carried out. The LCA inventory inputs for the biogas scenario was entirely based on primary data obtained from algal cultivation (in pilot scale raceway pond), harvesting, and biogas production; while only the downstream processing involved in biodiesel production namely drying, reaction and purification were based on secondary data. Overall, eight scenarios were modeled for the integrated process involving: algae-based CO2 capture and downstream processing scenarios for biodiesel and biogas along with impact assessment of nutrient addition and extent of recycling in a life cycle perspective. The LCA results indicated a huge energy deficit and net CO2 negative in terms of CO2 capture for both the biodiesel and biogas scenarios, majorly due to lower algal biomass productivity and higher energy requirements for culture mixing. The sensitivity analysis indicated that variability in the biomass productivity has predominant effect on the primary energy demand and global warming potential (GWP, kg CO2 eq.) followed by specific energy consumption for mixing algal culture. Furthermore, the LCA results indicated that biogas conversion route from microalgae was more energy efficient and sustainable than the biodiesel route. The overall findings of the study suggested that microalgae-mediated CO2 capture and conversion to biodiesel and biogas production can be energy efficient at higher biomass productivity (> 10 g m-2 day-1) and via employing energy-efficient systems for culture mixing (< 2 W m-3).

Development of a carotenoid enriched probiotic yogurt from fresh biomass of Spirulina and its characterization.

Incorporation of Spirulina in milk as thermally dried powder has the disadvantages of non-uniform distribution with undesirable odor and flavor. Through homogenization (200 ± 10 bar), complete dispersion of fresh Spirulina biomass (7% w/w) in milk was achieved and thereafter a carotenoid enriched probiotic yogurt was developed. Confocal microscopy revealed porous Spirulina-milk protein matrix integrated with smaller fat globules in the yogurt. Spirulina led to a 29.56% increase in Lactobacillus acidophilus count, a 20% reduction in fermentation time and a total probiotic count of 1.2 × 107 CFU mL-1. The protein, total chlorophyll, total carotenoid and ß-carotene content (on dry w/w basis) were 3.58 ± 0.08 g 100 g-1, 0.407 ± 0.018 mg g-1, 0.235 ± 0.016 mg g-1 and 13.28 ± 0.08 µg g-1, respectively. During storage (18 days at 6-8 °C), the L. acidophilus count reached 8.83 ± 0.11 log CFU mL-1 with 103.03% increase in the viability by day three and the yogurt retained 71.5% carotenoids. The probiotc Spirulina yogurt was found to be acceptable to consumers as evaluated by affective consumer test.

Strong Effect of Organic Ligands on the Electronic Structure of Metal-Chalcogenide Clusters.

It is shown that multiple ionization energies of metal-chalcogenide clusters can be substantially reduced by adding ligands that form charge transfer complexes. We demonstrate this intriguing phenomenon by considering metal-chalcogenide clusters including cases where a cluster has a filled electronic shell with a large gap between the occupied and unoccupied states reminiscent of stable species. The studies include a Co6Se8 core ligated with tri-ethylphosphine (PEt3) ligands forming a stable Co6Se8(PEt3)6 species. All of the ligated clusters have a first ionization energy in the range for alkali atoms and multiple ionization energies that are considerably lower than those for the non-ligated clusters. The change in electronic behavior upon ligation can be associated with a shift in the electronic spectrum via a crystal field like effect due to attaching ligands that form charge transfer complexes. We also show that metal-chalcogenide species can be programmed by proper ligand replacement to promote dimerization by first forming the Co6Se8(PEt3) n(CO)6- n ( n = 0-6) clusters where the CO ligands could be replaced by diisocyanide (CNC6H4NC) ligands. The diisocyanide ligand acts as a rigid linker between the metallic cores, enabling the formation of a Co6Se8(PEt3)5(CNC6H4NC)Co6Se8(PEt3)5 superatomic molecule (SM), and we examine the electronic and magnetic properties of the recently synthesized SM via studies on an analogous SM with smaller ligands.

Metal Chalcogenide Clusters with Closed Electronic Shells and the Electronic Properties of Alkalis and Halogens.

Clusters with filled electronic shells and a large gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are generally energetically and chemically stable. Enabling clusters to become electron donors with low ionization energies or electron acceptors with high electron affinities usually requires changing the valence electron count. Here we demonstrate that a metal cluster may be transformed from an electron donor to an acceptor by exchanging ligands while the neutral form of the clusters has closed electronic shells. Our studies on Co6Te8(PEt3)m(CO)n (m + n = 6) clusters show that Co6Te8(PEt3)6 has a closed electronic shell and a low ionization energy of 4.74 eV, and the successive replacement of PEt3 by CO ligands ends with Co6Te8(CO)6 exhibiting halogen-like behavior. Both the low ionization energy Co6Te8(PEt3)6 and high electron affinity Co6Te8(CO)6 have closed electronic shells marked by high HOMO-LUMO gaps of 1.24 and 1.39 eV, respectively. Further, the clusters with an even number of ligands favor a symmetrical placement of ligands around the metal core.

CO ligands stabilize metal chalcogenide Co6Se8(CO)n clusters via demagnetization.

The role of carbon monoxide ligands on the magnetic moment of Co6Se8(CO)n clusters, n = 0-6 was investigated to better understand the interplay between the electronic structure of metal chalcogenide clusters and their ligands. We find that the addition of CO ligands to Co6Se8 results in the gradual demagnetization of the cluster. Generally, the addition of a CO ligand effectively adds two electrons to the cluster that occupy deeper states and further pushes up an antibonding orbital out of the valence manifold of cluster states. Through such processes, the fully ligated Co6Se8(CO)6 cluster attains a closed electronic shell with a large gap between occupied and unoccupied states. Each removal of a CO ligand from the cluster then stabilizes an antibonding state that adds unoccupied states to the valence manifold. Such a cluster with partially filled states may either deform as in a Jahn-Teller distortion to quench the spin, or maintain its core structure and be stabilized in a high spin state as in Hund's rules. As these clusters generally maintain their octahedral core, the high spin state prevails and the removal of the ligands results in an increase in spin multiplicity.

Magnetic behavior of superatomic-fullerene assemblies.

It has recently been possible to synthesize ordered assemblies composed of magnetic superatomic clusters Ni9Te6(PEt3)8 separated by C60 and study their magnetic behavior. We have carried out theoretical studies on model systems consisting of magnetic superatoms separated by non-magnetic species to examine the evolution in magnetic response as the nature of the magnetic superatom (directions of spin quantization), the strength of isotropic and anisotropic interactions, the magnetic anisotropy energy, and the size of the assembly are varied. We have examined square planar configurations consisting of 16, 24 and 48 sites with 8, 12 and 24 magnetic superatoms respectively. The magnetic atoms are allowed 2 or 5 orientations. The model Hamiltonian includes isotropic exchange interactions with second nearest neighbor ferromagnetic and nearest neighbor antiferromagnetic couplings and anisotropic Dzyaloshinskii-Moriya interactions. It is shown that the inclusion of Dzyaloshinskii-Moriya interaction that cause spin canting is necessary to get qualitative response as observed in experiments.

Symmetry and magnetism in Ni9Te6 clusters ligated by CO or phosphine ligands.

The removal of a single ligand from the magnetic Ni9Te6(L)8 (L = P(CH3)3, CO) clusters is found to quench the magnetic moment. The reduction in magnetic moment is caused by a geometric deformation of the Ni9Te6 core that breaks the octahedral symmetry of the cluster. This effect is observed in both the CO and phosphine based ligands. The octahedral symmetry bare cluster is also found to have a large magnetic moment. These results highlight the dilemma faced by magnetic ligand protected clusters whose symmetry has been broken: whether to break the spin symmetry as in Hund's rules or to break the spatial symmetry as in the Jahn-Teller effect. The spatial symmetry breaking is found to be an oblate distortion that forms additional Ni-Te bonds resulting in the enhanced stability of the cluster.

Ni9Te6(PEt3)8C60 Is a Superatomic Superalkali Superparamagnetic Cluster Assembled Material (S(3)-CAM).

First-principles theoretical studies enable an electronic and magnetic characterization of the recently synthesized Ni9Te6(PEt3)8C60 ionic material consisting of Ni9Te6(PEt3)8 superatoms and C60. The PEt3 ligands are shown to create an internal coulomb well that lifts the quantum states of the Ni9Te6 cluster, lowering its ionization potential to 3.39 eV thus creating a superalkali motif. The metallic core has a spin magnetic moment of 5.3 µB in agreement with experiment. The clusters are marked by low magnetic anisotropy energy (MAE) of 2.72 meV and a larger intra-exchange coupling exceeding 0.2 eV, indicating that the observed paramagnetic behavior around 10K is due to superparamagnetic relaxations. The magnetic motifs separated by C60 experience a weak superexchange that stabilizes a ferromagnetic ground state as observed around 2 K. The calculated MAE is sensitive to the charged state that could account for the observed change in magnetic transition temperature with size of the ligands or anion.

Transforming Ni9Te6 from Electron Donor to Acceptor via Ligand Exchange.

The ability to donate or accept charge is a fundamental property of a chemical species. This property is typically rooted in the valence electron count and may be determined from the ionization potential and electron affinity. First-principles theoretical studies have been carried out to show that a cluster may be transformed from a donor to an acceptor by changing only the ligand. Our studies on a chalcogenide Ni9Te6 cluster show that the ionization potential and electron affinity undergo substantial changes as the attachment of phosphine PH3 decreases the ionization potential to be less than that of sodium, whereas the attachment of PCl3 or CO increases the adiabatic electron affinity to be greater than iodine. The ligands change the electronic properties by creating a coulomb well that can shift the electronic spectrum. Studies on Co9Te6(CO)8 clusters show agreement with experiment and demonstrate that the ideas developed here are applicable to a wider group of clusters.

Geometry controls the stability of FeSi14.

First-principles theoretical studies have been carried out to investigate the stability of Sin cages impregnated with a Fe atom. It is shown that FeSi9, FeSi11, and FeSi14 clusters exhibit enhanced local stability as seen through an increase in Si binding energy, Fe embedding energy, the gap between the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO), and the Ionization Potential (IP). The conventional picture for the stability of such species combines an assumption of electron precise bonding with the 18-electron rule; however, we find this to be inadequate to explain the enhanced stability in FeSi11 and FeSi14 because the d-band is filled for all FeSin clusters for n≥ 9. FeSi14 is shown to be the most stable due to a compact and highly symmetric Si14 cage with octahedral symmetry that allows better mixing between Fe 3d- and Si 3p-electronic states.

Nature of valence transition and spin moment in Ag(n)V(+) clusters.

Evolution in the atomic structure, bonding characteristics, stability, and the spin magnetic moment of neutral and cationic AgnV clusters has been investigated using first-principles density functional approach with gradient corrected functional. It is shown that at small sizes, the V 4s states hybridize with Ag states to form 1S and 1P like superatomic orbitals, whereas the 3d states are localized on V giving the V atom an effective valence of 1 or 2. Starting from Ag8V(+), the V 3d states begin to participate in the bonding by hybridizing with the nearly free electron gas to form 1D superatomic orbitals increasing the V atom effective valence toward 5. For the cationic clusters, this changing valence results in three shell closures that lead to stable species. These occur for cationic clusters containing 5, 7, and 14 Ag atoms. The first two stable species correspond to filled 1S and 1P shells in two and three dimensions with a valence of 2 for V, whereas the closure at 14 Ag atoms correspond to filled 1S, 1P, and 1D shells with V site exhibiting a valence of 5. The transition from filled 1S and 1P shells to filled 1S, 1P, and 1D shells is confirmed by a quenching of the spin magnetic moment. The theoretical findings are consistent with the observed drops in intensity in the mass spectrum of AgnV(+) clusters after 5, 7, and 14 Ag atoms.

Hund's rule in superatoms with transition metal impurities.

The quantum states in metal clusters bunch into supershells with associated orbitals having shapes resembling those in atoms, giving rise to the concept that selected clusters could mimic the characteristics of atoms and be classified as superatoms. Unlike atoms, the superatom orbitals span over multiple atoms and the filling of orbitals does not usually exhibit Hund's rule seen in atoms. Here, we demonstrate the possibility of enhancing exchange splitting in superatom shells via a composite cluster of a central transition metal and surrounding nearly free electron metal atoms. The transition metal d states hybridize with superatom D states and result in enhanced splitting between the majority and minority sets where the moment and the splitting can be controlled by the nature of the central atom. We demonstrate these findings through studies on TMMg(n) clusters where TM is a 3d atom. The clusters exhibit Hund's filling, opening the pathway to superatoms with magnetic shells.

Bibliometric review of telematics-based automobile insurance: Mapping the landscape of research and knowledge.

Telematics technology and its implementation in auto insurance have received great interest due to their potential to transform the insurance sector and promote safer driving practices. By implementing telematics technology, insurers may tailor insurance premiums to individual drivers, taking into account their real driving habits and performance, ultimately leading to improved road safety, cost savings, and an empowered driving community. The current study, through bibliometric analysis, carefully identifies and evaluates the existing body of scholarly literature on this subject for the last 21 years, including journal articles, conference papers, and related publications. The analysis uncovers key research studies, influential authors, top publication outlets, top countries with collaborations, and prolific research fields, providing useful insights into the evolution and growth of telematics-based insurance research. Furthermore, thematic mapping, cluster analysis, and critical analysis of top recent studies aided in identifying key research clusters and themes, as well as potential gaps and areas for further exploration, guiding future researchers and policymakers in advancing this transformative technology.

Devastating Neurological Outcome Following a Subarachnoid-Pleural Fistula During Thoracic Surgery.

Pneumocephalus due to a subarachnoid-pleural fistula (SPF) has previously been described in the literature and is a rare complication following thoracic surgery. In this report, we discuss a patient who developed profound neurologic sequelae following right-sided pneumonectomy which was complicated by T2 nerve root avulsion and SPF development. The patient returned to the OR on postoperative day 21 in the setting of significant neurologic deterioration secondary to intracranial hypotension and pneumocephalus for SPF closure via thoracic laminectomy in the prone position. We present a rare cause of pneumocephalus and CSF leak, resulting in complications and sequelae and its management.

Development and Validation of Fast and Sensitive RP-HPLC Stability-Indicating Method for Quantification of Piroxicam in Bulk Drug.

A simple, rapid, sensitive, and cost-effective green solvent-assisted reverse-phase high-performance liquid chromatographic technique, coupled with a photodiode array detector, was developed and validated for the estimation of piroxicam (PRXM). The chromatographic separation was achieved by using a C-18 (250 × 4.6) mm, 5-µm stationary phase and a mobile phase consisting of methanol and 0.1% ortho-phosphoric acid in water in a ratio of (80:20) v/v at a flow rate of 1 ml/min. The detection was carried out at a wavelength of 254 nm with a constant injection volume of 10 µL throughout the analysis. The calibration curve was observed to be linear over the optimum concentration range of 50-300 µg mL-1, with an R2 value of 0.9995. The developed method was validated as per the International Council for Harmonisation (ICH) Q2 (R1) guideline. Various parameters like selectivity/specificity, accuracy/recovery, linearity, precision, detection limit, quantitation limit, robustness and stability of analyte in solution were performed for the method validation. The PRXM was evaluated under stressed conditions, including acidic, basic, oxidative, thermal and photolytic, as per ICH Q1 (R2) guidelines. Significant degradation was observed in acidic and basic degradation conditions. Conversely, the drug substance showed stability when exposed to oxidative, photolytic and thermal degradation conditions.

Alternate Electrode Placements to Facilitate Frontal Electroencephalography Monitoring in Anesthetized and Critically Ill Patients.

BACKGROUND: Frontal electroencephalography (EEG) monitoring can be useful in guiding the titration of anesthetics, but it is not always feasible to place electrodes in the standard configuration in some circumstances, including during neurosurgery. This study compares 5 alternate configurations of the Masimo Sedline Sensor. METHODS: Ten stably sedated patients in the intensive care unit were recruited. Frontal EEG was monitored in the standard configuration (bifrontal upright) and 5 alternate configurations: bifrontal inverse, infraorbital, lateral upright, lateral inverse, and semilateral. Average power spectral densities (PSDs) with 95% CIs in the alternate configurations were compared to PSDs in the standard configuration. Two-one-sided-testing with Wilcoxon signed-rank tests assessed equivalence in the spectral edge frequency (SEF-95), EEG power, and relative delta (0.5 to 3.5 Hz), alpha (8 to 12 Hz), and beta (20 to 30 Hz) power between each alternate and standard configurations. RESULTS: After the removal of unanalyzable tracings, 7 patients were included for analysis in the infraorbital configuration and 9 in all other configurations. In the lateral upright and lateral inverse configurations, PSDs significantly differed from the standard configuration within the 15 to 20 Hz band. The greatest decrease in EEG power was in the lateral inverse configuration (median: -97 dB; IQR: -130, -62 dB). The largest change in frequency distribution of EEG power was in the infraorbital configuration; median SEF-95 change of -1.4 Hz (IQR: -2.8, 0.7 Hz), median relative delta power change of +7.3% (IQR: 1.4%, 7.9%), and median relative alpha power change of -0.6% (IQR: -5.7%, 0.0%). CONCLUSIONS: These 5 alternate Sedline electrode configurations are suitable options for monitoring frontal EEG when the standard configuration is not possible.