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1.
Trends Genet ; 39(7): 521-523, 2023 07.
Artículo en Inglés | MEDLINE | ID: mdl-37100683

RESUMEN

Although biobanks can support research across geographic and governance boundaries, biomedical researchers consistently describe preferences for either collaborating with local biobanks or establishing their own biobanks. This article summarizes the potential research impacts of local biobank use and suggests how descriptions of biospecimen provenance can be improved in research publications.


Asunto(s)
Bancos de Muestras Biológicas , Investigación Biomédica
2.
Phys Chem Chem Phys ; 26(23): 16589-16596, 2024 Jun 12.
Artículo en Inglés | MEDLINE | ID: mdl-38814318

RESUMEN

Isolated mixed-ligand complexes provide tractable model systems in which to study competitive and cooperative binding effects as well as controlled energy flow. Here, we report spectroscopic and isotopologue-selective infrared photofragmentation dynamics of mixed gas-phase Au(12/13CO)n(N2O)m+ complexes. The rich infrared action spectra, which are reproduced well using simulations of calculated lowest energy structures, clarify previous ambiguities in the assignment of vibrational bands, especially accidental coincidence of CO and N2O bands. The fragmentation dynamics exhibit the same unexpected behaviour as reported previously in which, once CO loss channels are energetically accessible, these dominate the fragmentation branching ratios, despite the much lower binding energy of N2O. We have investigated the dynamics computationally by considering anharmonic couplings between a relevant subset of normal modes involving both ligand stretch and intermolecular modes. Discrepancies between correlated and uncorrelated model fit to the ab initio potential energy curves are quantified using a Boltzmann sampled root mean squared deviation providing insight into efficiency of vibrational energy transfer between high frequency ligand stretches and the softer intermolecular modes which break during fragmentation.

3.
BMC Med ; 21(1): 445, 2023 11 16.
Artículo en Inglés | MEDLINE | ID: mdl-37974189

RESUMEN

BACKGROUND: Acquired brain injury (ABI) is linked to increased depression risk. Existing therapies for depression in ABI (e.g., cognitive behavioural therapy) have mixed efficacy. Behavioural activation (BA), an intervention that encourages engaging in positively reinforcing activities, shows promise. The primary aims were to assess feasibility, acceptability, and potential efficacy of two 8-week BA groups. METHODS: Adults (≥ 18 years) recruited from local ABI services, charities, and self-referral via social media were randomised to condition. The Activity Planning group (AP; "traditional" BA) trained participants to plan reinforcing activities over 8 weeks. The Activity Engagement group (AE; "experiential" BA) encouraged engagement in positive activities within session only. Both BA groups were compared to an 8-week Waitlist group (WL). The primary outcomes, feasibility and acceptability, were assessed via recruitment, retention, attendance, and qualitative feedback on groups. The secondary outcome, potential efficacy, was assessed via blinded assessments of self-reported activity levels, depression, and anxiety (at pre- and post-intervention and 1 month follow-up) and were compared across trial arms. Data were collected in-person and remotely due to COVID-19. RESULTS: N = 60 participants were randomised to AP (randomised n = 22; total n = 29), AE (randomised n = 22; total n = 28), or re-randomised following WL (total n = 16). Whether in-person or remote, AP and AE were rated as similarly enjoyable and helpful. In exploring efficacy, 58.33% of AP members had clinically meaningful activity level improvements, relative to 50% AE and 38.5% WL. Both AP and AE groups had depression reductions relative to WL, but only AP participants demonstrated anxiety reductions relative to AE and WL. AP participants noted benefits of learning strategies to increase activities and learning from other group members. AE participants valued social discussion and choice in selecting in-session activities. CONCLUSIONS: Both in-person and remote group BA were feasible and acceptable in ABI. Though both traditional and experiential BA may be effective, these may have different mechanisms. TRIAL REGISTRATION: Clinicaltrials.gov, NCT03874650. Protocol version 2.3, May 26 2020.


Asunto(s)
Acer , Lesiones Encefálicas , Terapia Cognitivo-Conductual , Adulto , Humanos , Lesiones Encefálicas/terapia , Terapia Cognitivo-Conductual/métodos , Estudios de Factibilidad , Satisfacción Personal , Proyectos Piloto
4.
Chemistry ; 29(37): e202203570, 2023 Jul 03.
Artículo en Inglés | MEDLINE | ID: mdl-36794765

RESUMEN

Gas-phase solvation of halides by 1,3-butadiene has been studied via a combination of photoelectron spectroscopy and density functional theory. Photoelectron spectra for X- ⋯(C4 H6 )n (X=Cl, Br, I where n=1-3, 1-3 and 1-7 respectively) are presented. For all complexes, the calculated structures indicate that butadiene is bound in a bidentate fashion through hydrogen-bonding, with the chloride complex showing the greatest degree of stabilisation of the internal C-C rotation of cis-butadiene. In both Cl- and Br- complexes, the first solvation shell is shown to be at least n = 4 ${n = 4}$ from the vertical detachment energies (VDEs), however for I- , increases in the VDE may suggest a metastable, partially filled, first solvation shell for n = 4 ${n = 4}$ and a complete shell at n = 6 ${n = 6}$ . These results have implications for gas-phase clustering in atmospheric and extraterrestrial environments.

5.
Chemphyschem ; 24(7): e202200733, 2023 Apr 03.
Artículo en Inglés | MEDLINE | ID: mdl-36504309

RESUMEN

Hydrogen bonding and halogen bonding are important non-covalent interactions that are known to occur in large molecular systems, such as in proteins and crystal structures. Although these interactions are important on a large scale, studying hydrogen and halogen bonding in small, gas-phase chemical species allows for the binding strengths to be determined and compared at a fundamental level. In this study, anion photoelectron spectra are presented for the gas-phase complexes involving bromide and the four chloromethanes, CH3 Cl, CH2 Cl2 , CHCl3 , and CCl4 . The stabilisation energy and electron binding energy associated with each complex are determined experimentally, and the spectra are rationalised by high-level CCSD(T) calculations to determine the non-covalent interactions binding the complexes. These calculations involve nucleophilic bromide and electrophilic bromine interactions with chloromethanes, where the binding motifs, dissociation energies and vertical detachment energies are compared in terms of hydrogen bonding and halogen bonding.

6.
J Phys Chem A ; 127(44): 9220-9228, 2023 Nov 09.
Artículo en Inglés | MEDLINE | ID: mdl-37906705

RESUMEN

In this study, mixed carbonyl and nitrous oxide complexes with Rh+ were studied by mass-selective infrared photodissociation spectroscopy in a molecular beam. The infrared spectra, recorded in the region of the CO and N2O N═N stretches, were assigned and interpreted with the aid of simulated spectra of low-energy structural isomers. Clear evidence of an inner coordination shell of four ligands is observed. The observed vibrational structure can be understood on the basis of local mode vibrations in the two ligands. However, there is also evidence of multiple low-lying isomers and cooperative binding effects between the two ligands. In particular, σ donation from directly coordinated nitrous oxide ligands drives more classical carbonyl bonding than has been observed in pure carbonyl complexes. The observed fragmentation branching ratios following resonant infrared absorption are explained by simple statistical and energetic arguments, providing a contrast with those of equivalent Au+ complexes.

7.
Histopathology ; 81(4): 467-476, 2022 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-35869801

RESUMEN

AIMS: To describe a new international dataset for pathology reporting of ductal carcinoma in situ (DCIS), variants of lobular carcinoma in situ (LCIS) and low-grade lesions (encapsulated papillary carcinoma, solid papillary carcinoma in situ, Paget's disease) produced by the International Collaboration on Cancer Reporting (ICCR). METHODS AND RESULTS: The ICCR, a global alliance of pathology bodies, uses a rigorous and efficient process for the development of evidence-based, structured datasets for pathology reporting of common cancers. Their aim is to support quality pathology reporting and engender understanding between the breast surgeon, pathologist, and oncologist for optimal and uniform patient management globally. Here we describe the dataset for DCIS, some variants of LCIS (namely the pleomorphic and the florid variants), and low-grade lesions by a multidisciplinary panel of internationally recognized experts. The agreed dataset comprises 12 core (required) and five noncore (recommended) elements suitable for both developed and low-income jurisdictions, derived from a review of current evidence. Areas of contention were addressed using a pragmatic approach in the absence of evidence. Use of all core elements is the minimum reporting standard for any individual case. Commentary is provided, explaining each element's clinical relevance, definitions to be applied where appropriate for the agreed list of value options and the rationale for considering the element as core or noncore. CONCLUSION: This first internationally agreed dataset for DCIS, variants of LCIS, and low-grade lesions reporting will enable their standardization of pathology reporting and enhance clinicopathological communication leading to improved patient outcomes. Widespread adoption will also facilitate international comparisons, multinational clinical trials, and help to improve the management of breast disease globally.


Asunto(s)
Carcinoma de Mama in situ , Neoplasias de la Mama , Carcinoma in Situ , Carcinoma Intraductal no Infiltrante , Carcinoma Lobular , Carcinoma Papilar , Carcinoma de Mama in situ/cirugía , Carcinoma Intraductal no Infiltrante/patología , Carcinoma Lobular/patología , Femenino , Humanos , Hiperplasia , Patólogos
8.
Chemphyschem ; 23(21): e202200278, 2022 Nov 04.
Artículo en Inglés | MEDLINE | ID: mdl-35708114

RESUMEN

Mass spectrometry and anion photoelectron spectroscopy have been used to study the gas-phase S N 2 ${{{\rm S}}_{{\rm N}}2}$ reaction involving B r - ${{{\rm B}{\rm r}}^{-}}$ and C H 3 I ${{{\rm C}{\rm H}}_{3}{\rm I}}$ . The anion photoelectron spectra associated with the reaction intermediates of this S N 2 ${{{\rm S}}_{{\rm N}}2}$ reaction are presented. High-level CCSD(T) calculations have been utilised to investigate the reaction intermediates that may form as a result of the S N 2 ${{{\rm S}}_{{\rm N}}2}$ reaction along various different reaction pathways, including back-side attack and front-side attack. In addition, simulated vertical detachment energies of each reaction intermediate have been calculated to rationalise the photoelectron spectra.


Asunto(s)
Teoría Cuántica , Espectroscopía de Fotoelectrones , Aniones/química
9.
J Child Psychol Psychiatry ; 63(1): 58-67, 2022 01.
Artículo en Inglés | MEDLINE | ID: mdl-34128219

RESUMEN

BACKGROUND: The introduction of developmentally adapted criteria for posttraumatic stress disorder (PTSD) has improved the identification of ≤6-year-old children with clinical needs. Across two studies, we assess predictors of the development of PTSD in young children (PTSD-YC), including the adult-led acute stress disorder (ASD) diagnosis, and provide proof of principle for cognitive-focused therapy for this age range, with the aim of increasing treatment options for children diagnosed with PTSD-YC. METHOD: Study 1 (N = 105) assessed ASD and PTSD-YC diagnosis in 3- to 8-year-old children within one month and at around three months following attendance at an emergency room. Study 2 (N = 37) was a preregistered (www.isrctn.com/ISRCTN35018680) randomized controlled early-phase trial comparing CBT-3M, a cognitive-focused intervention, to treatment-as-usual (TAU) delivered within the UK NHS to 3- to 8-year-olds diagnosed with PTSD-YC. RESULTS: In Study 1, the ASD diagnosis failed to identify any young children. In contrast, prevalence of acute PTSD-YC (minus the duration requirement) was 8.6% in the first month post-trauma and 10.1% at 3 months. Length of hospital stay, but no other demographic or trauma-related characteristics, predicted development of later PTSD-YC. Early (within one month) diagnosis of acute PTSD-YC had a positive predictive value of 50% for later PTSD-YC. In Study 2, most children lost their PTSD-YC diagnosis following completion of CBT-3M (84.6%) relative to TAU (6.7%) and CBT-3M was acceptable to recipient families. Effect sizes were also in favor of CBT-3M for secondary outcome measures. CONCLUSIONS: The ASD diagnosis is not fit for purpose in this age-group. There was a strong and encouraging signal of putative efficacy for young children treated using a cognitive-focused treatment for PTSD, and a larger trial of CBT-3M is now warranted.


Asunto(s)
Terapia Cognitivo-Conductual , Trastornos por Estrés Postraumático , Adulto , Niño , Preescolar , Hospitales , Humanos , Prevalencia , Psicoterapia , Trastornos por Estrés Postraumático/diagnóstico , Trastornos por Estrés Postraumático/epidemiología , Trastornos por Estrés Postraumático/terapia
10.
Phys Chem Chem Phys ; 24(42): 25842-25852, 2022 Nov 02.
Artículo en Inglés | MEDLINE | ID: mdl-36278794

RESUMEN

Anion photoelectron spectroscopy has been used to determine the electron binding energies of the X-⋯C3H6 (X = Cl, Br, I) complexes. To complement the experimental spectra the DSD-PBEP86-D3BJ functional has been employed, following comparison with previously calculated halide/halogen-molecule van der Waals complexes. To validate the functional, comparison between the complex geometries and vertical detachment energies with both experimental and CCSD(T)/CBS data for a suite of halide-molecule complexes is also made. PES spectra determine the electron binding energies as 3.89 eV and 4.00 eV, 3.59 eV and 4.01 eV, and 3.26 eV and 4.20 eV for transitions to perturbed 2P states of the chlorine, bromine and iodine complexes respectively. Two contributing structures resulting in the photoelectron spectrum are those where the halide is coordinated by two hydrogens, each from a terminal carbon in C3H6, and when bifurcating the CC bond. These complexes are distinct from the corresponding halide-ethene complexes and represent potential entry pathways to haloakyl radical formation in atmospheric and extraterrestrial environments.

11.
Phys Chem Chem Phys ; 24(40): 24748-24758, 2022 Oct 19.
Artículo en Inglés | MEDLINE | ID: mdl-36196917

RESUMEN

Halide-formic acid complexes have been studied utilising a combined experimental and theoretical approach. Formic acid exists as two conformers, distinguished by the relative rotation about the C-OH bond. Computational investigation of the formic acid isomerisation reaction between the two conformers has revealed the ability of halide anions to catalyse the formation of, and preferentially stabilise, the higher energy conformer. Anion photoelectron spectroscopy has been used to study the halide-formic acid complexes, with the experimental vertical detachment energies compared with simulated photodetachment energies with respect to halide complexes with both formic acid conformers. The existence of experimental spectral features associated with halide complexes of the higher energy formic acid confomer confirms in situ generation, likely as a result of the halide mediated catalytic formation.


Asunto(s)
Formiatos , Formiatos/química , Espectroscopía de Fotoelectrones , Aniones/química , Catálisis
12.
Artículo en Inglés | MEDLINE | ID: mdl-36383431

RESUMEN

BACKGROUND: Early diagnosis of dementia is crucial for timely intervention. However, frequently, there is a substantial delay in diagnosis. Therefore, it is essential to recognise and address the barriers to early diagnosis. These have not been systematically studied in India. We at a specialist memory clinic in India investigated the time from symptom onset to diagnosis of dementia and factors contributing to the delay. METHODS: In this cross-sectional study, consecutive patients with dementia (n = 855) seen at a private hospital underwent a standard clinical assessment and investigations. The primary outcome variable was time from symptom onset to diagnosis (TTD). The association of age, education, gender, dementia subtype, and age of onset on TTD were examined using a univariate analysis of covariance. RESULTS: The median TTD was 24 months; 43% were diagnosed after 24 months. There was a significant association between TTD and age at onset (young onset-median 36 months vs. late onset-24 months) and dementia subtype. Patients with vascular dementia were diagnosed significantly earlier as compared to patients with Alzheimer's disease (AD) and frontotemporal dementia (FTD) [median 18, 24, and 30 months, respectively]. There was no effect of gender or education on the TTD. CONCLUSION: About 40% of patients with dementia were diagnosed more than 2 years after symptom onset, particularly young onset dementias and FTD. Our study findings highlight the gaps in diagnosing patients with dementia in urban India and have significant implications for developing and implementing multifaceted interventions to improve the early diagnosis of dementia.


Asunto(s)
Enfermedad de Alzheimer , Demencia Vascular , Demencia Frontotemporal , Humanos , Edad de Inicio , Estudios Transversales , Enfermedad de Alzheimer/diagnóstico
13.
J Phys Chem A ; 126(20): 3072-3079, 2022 May 26.
Artículo en Inglés | MEDLINE | ID: mdl-35549219

RESUMEN

Anion photoelectron spectroscopy has been used to investigate the structure and dynamics of CH3OOI- van der Waals complexes. Peaks within the photoelectron spectrum are attributed to photodetachment to the perturbed 2P3/2 state of I···CH3OO (3.46 eV) and the two 2P states of bare iodine. A broad feature at 1.7-2.4 eV is attributed to detachment to the excited singlet states from two O2-···CH3I complexes. This represents the first anion photoelectron spectroscopy of a halide-bound methylperoxy radical species. Complex structures have been optimized using MP2/aug-cc-pVQZ with single-point energies at W1w theory for ground-state complexes and NEVPT2 for photodetachment to excited O2. Interactions are dominated by electrostatics, with the anion species interacting with the methyl pocket of the solvating molecule, suggesting conversion via an SN2 mechanism, and excess energy leading to complex dissociation within the timescale of mass spectrometry. The calculated W1w Gibbs energies suggest that while an electron transfer (ET) pathway to conversion is available, it is comparatively unfavored.

14.
J Phys Chem A ; 126(50): 9414-9422, 2022 Dec 22.
Artículo en Inglés | MEDLINE | ID: mdl-36480929

RESUMEN

We present a combined experimental and quantum chemical study of gas-phase group 9 metal nitrosyl complexes, M(NO)n+ (M = Co, Rh, Ir). Experimental infrared photodissociation spectra of mass-selected ion-molecule complexes are presented in the region 1600 cm-1 to 2000 cm-1 which includes the NO stretch. These are interpreted by comparison with the simulated spectra of energetically low-lying structures calculated using density functional theory. A mix of linear and nonlinear ligand binding is observed, often within the same complex, and clear evidence of coordination shell closing is observed at n = 4 for Co(NO)n+ and Ir(NO)n+. Calculations of Rh(NO)n+ complexes suggest additional low-lying five-coordinate structures. In all cases, once a second coordination shell is occupied, new spectral features appear which are assigned to (NO)2 dimer moieties. Further evidence of such motifs comes from differences in the spectra recorded in the dissociation channels corresponding to single and double ligand loss.

15.
Neuropsychol Rehabil ; 32(10): 2603-2627, 2022 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-34505555

RESUMEN

Cognitive difficulties are common following stroke and can have widespread impacts on everyday functioning. Technological advances offer the possibility of individualized cognitive training for patients at home, potentially providing a low-cost, low-intensity adjunct to rehabilitation services. Using this approach, we have previously demonstrated post-training improvements in attention and everyday functioning in fronto-parietal stroke patients. Here we examine whether these benefits are observed more broadly in a community stroke sample. Eighty patients were randomized to either 4 weeks of online adaptive attention training (SAT), working memory training (WMT) or waitlist (WL). Cognitive and everyday function measures were collected before and after the intervention, and after 3 months. During training, weekly measures of patients' subjective functioning were collected. The training was well received and compliance good. No differences in our primary end-point, spatial bias, or other cognitive functions were observed. However, on patient-reported outcomes, SAT participants showed greater levels of improvement in everyday functioning than WMT or WL participants. In line with our previous work, everyday functioning improvements were greatest for patients with spatial impairments and those who received SAT training. Whether attention training can be recommended for stroke survivors depends on whether cognitive test performance or everyday functioning is considered more relevant.


Asunto(s)
Rehabilitación de Accidente Cerebrovascular , Accidente Cerebrovascular , Humanos , Entrenamiento Cognitivo , Cognición , Accidente Cerebrovascular/complicaciones , Accidente Cerebrovascular/psicología , Memoria a Corto Plazo , Atención
16.
Carcinogenesis ; 42(3): 369-377, 2021 04 17.
Artículo en Inglés | MEDLINE | ID: mdl-33300568

RESUMEN

Genome-wide association studies (GWAS) of esophageal adenocarcinoma (EAC) and its precursor, Barrett's esophagus (BE), have uncovered significant genetic components of risk, but most heritability remains unexplained. Targeted assessment of genetic variation in biologically relevant pathways using novel analytical approaches may identify missed susceptibility signals. Central obesity, a key BE/EAC risk factor, is linked to systemic inflammation, altered hormonal signaling and insulin-like growth factor (IGF) axis dysfunction. Here, we assessed IGF-related genetic variation and risk of BE and EAC. Principal component analysis was employed to evaluate pathway-level and gene-level associations with BE/EAC, using genotypes for 270 single-nucleotide polymorphisms (SNPs) in or near 12 IGF-related genes, ascertained from 3295 BE cases, 2515 EAC cases and 3207 controls in the Barrett's and Esophageal Adenocarcinoma Consortium (BEACON) GWAS. Gene-level signals were assessed using Multi-marker Analysis of GenoMic Annotation (MAGMA) and SNP summary statistics from BEACON and an expanded GWAS meta-analysis (6167 BE cases, 4112 EAC cases, 17 159 controls). Global variation in the IGF pathway was associated with risk of BE (P = 0.0015). Gene-level associations with BE were observed for GHR (growth hormone receptor; P = 0.00046, false discovery rate q = 0.0056) and IGF1R (IGF1 receptor; P = 0.0090, q = 0.0542). These gene-level signals remained significant at q < 0.1 when assessed using data from the largest available BE/EAC GWAS meta-analysis. No significant associations were observed for EAC. This study represents the most comprehensive evaluation to date of inherited genetic variation in the IGF pathway and BE/EAC risk, providing novel evidence that variation in two genes encoding cell-surface receptors, GHR and IGF1R, may influence risk of BE.


Asunto(s)
Adenocarcinoma/genética , Esófago de Barrett/genética , Biomarcadores de Tumor/genética , Neoplasias Esofágicas/genética , Somatomedinas/metabolismo , Adenocarcinoma/patología , Anciano , Esófago de Barrett/patología , Biomarcadores de Tumor/metabolismo , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Neoplasias Esofágicas/patología , Femenino , Predisposición Genética a la Enfermedad , Estudio de Asociación del Genoma Completo , Mutación de Línea Germinal , Humanos , Masculino , Persona de Mediana Edad , Polimorfismo de Nucleótido Simple , Receptor IGF Tipo 1/genética , Receptor IGF Tipo 1/metabolismo , Factores de Riesgo , Transducción de Señal/genética
17.
Chemphyschem ; 22(1): 69-75, 2021 Jan 07.
Artículo en Inglés | MEDLINE | ID: mdl-33184977

RESUMEN

A combined experimental and theoretical approach has been used to investigate X- ⋅⋅⋅CH2 O (X=F, Cl, Br, I) complexes in the gas phase. Photoelectron spectroscopy, in tandem with time-of-flight mass spectrometry, has been used to determine electron binding energies for the Cl- ⋅⋅⋅CH2 O, Br- ⋅⋅⋅CH2 O, and I- ⋅⋅⋅CH2 O species. Additionally, high-level CCSD(T) calculations found a C2v minimum for these three anion complexes, with predicted electron detachment energies in excellent agreement with the experimental photoelectron spectra. F- ⋅⋅⋅CH2 O was also studied theoretically, with a Cs hydrogen-bonded complex found to be the global minimum. Calculations extended to neutral X⋅⋅⋅CH2 O complexes, with the results of potential interest to atmospheric CH2 O chemistry.

18.
Chemphyschem ; 22(13): 1316-1320, 2021 07 02.
Artículo en Inglés | MEDLINE | ID: mdl-33977585

RESUMEN

The anion photoelectron spectra of Cl- ⋅⋅⋅CD3 CDO, Cl- ⋅⋅⋅(CD3 CDO)2 , Br- ⋅⋅⋅CH3 CHO, and I- ⋅⋅⋅CH3 CHO are presented with electron stabilisation energies of 0.55, 0.93, 0.48, and 0.40 eV, respectively. Optimised geometries of the singly solvated species featured the halide appended to the CH3 CHO molecule in-line with the electropositive portion of the C=O bond and having binding energies between 45 and 52 kJ mol-1 . The doubly solvated Cl- ⋅⋅⋅(CH3 CHO)2 species features asymmetric solvation upon the addition of a second CH3 CHO molecule. Theoretical detachment energies were found to be in excellent agreement with experiment, with comparisons drawn between other halide complexes with simple carbonyl molecules.

19.
Chemphyschem ; 22(9): 808-812, 2021 05 05.
Artículo en Inglés | MEDLINE | ID: mdl-33704887

RESUMEN

A combined experimental and theoretical approach has been used to study intermolecular chalcogen bonding. Specifically, the chalcogen bonding occurring between halide anions and CS2 molecules has been investigated using both anion photoelectron spectroscopy and high-level CCSD(T) calculations. The relative strength of the chalcogen bond has been determined computationally using the complex dissociation energies as well as experimentally using the electron stabilisation energies. The anion complexes featured dissociation energies on the order of 47 kJ/mol to 37 kJ/mol, decreasing with increasing halide size. Additionally, the corresponding neutral complexes have been examined computationally, and show three loosely-bound structural motifs and a molecular radical.

20.
J Exp Biol ; 224(Pt 5)2021 03 11.
Artículo en Inglés | MEDLINE | ID: mdl-33504585

RESUMEN

Cranial morphology in lepidosaurs is highly disparate and characterised by the frequent loss or reduction of bony elements. In varanids and geckos, the loss of the postorbital bar is associated with changes in skull shape, but the mechanical principles underlying this variation remain poorly understood. Here, we sought to determine how the overall cranial architecture and the presence of the postorbital bar relate to the loading and deformation of the cranial bones during biting in lepidosaurs. Using computer-based simulation techniques, we compared cranial biomechanics in the varanid Varanus niloticus and the teiid Salvator merianae, two large, active foragers. The overall strain magnitude and distribution across the cranium were similar in the two species, despite lower strain gradients in V. niloticus In S. merianae, the postorbital bar is important for resistance of the cranium to feeding loads. The postorbital ligament, which in varanids partially replaces the postorbital bar, does not affect bone strain. Our results suggest that the reduction of the postorbital bar impaired neither biting performance nor the structural resistance of the cranium to feeding loads in V. niloticus Differences in bone strain between the two species might reflect demands imposed by feeding and non-feeding functions on cranial shape. Beyond variation in cranial bone strain related to species-specific morphological differences, our results reveal that similar mechanical behaviour is shared by lizards with distinct cranial shapes. Contrary to the situation in mammals, the morphology of the circumorbital region, calvaria and palate appears to be important for withstanding high feeding loads in these lizards.


Asunto(s)
Lagartos , Animales , Fenómenos Biomecánicos , Simulación por Computador , Cráneo/anatomía & histología , Especificidad de la Especie
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