Simulating graphene-based single-electron transistor: incoherent current effects due to the presence of electron-electron interaction.

Carbon-based nanostructures have unparalleled electronic properties. At the same time, using an allotrope of carbon as the contacts can yield better device control and reproducibility. In this work, we simulate a single-electron transistor composed of a segment of a graphene nanoribbon coupled to carbon nanotubes electrodes. Using the non-equilibrium Green's function formalism we atomistically describe the electronic transport properties of the system including electron-electron interactions. Using this methodology we are able to recover experimentally observed phenomena, such as the Coulomb blockade, as well as the corresponding Coulomb diamonds. Furthermore, we separate the different contributions to transport and show that incoherent effects due to the interaction play a crucial role in the transport properties depending on the region of the stability diagram being considered.

Optical spectra and exciton radiative lifetimes in bulk transition metal dichalcogenides.

The optical response of layered transition metal dichalcogenides (TMDCs) exhibits remarkable excitonic properties which are important from both fundamental and device application viewpoints. One of these phenomena is the observation of intralayer/interlayer excitons. While much effort has been done to characterize excitons in monolayer TMDCs and their heterostructures, a quite limited number of works have addressed the exciton spectra of their bulk counterparts. In this work, we employ ab initio many-body perturbation calculations to investigate the exciton dynamics and spectra of bulk 2H-MX2 (M = Mo, W, and X = S, Se). For molybdenum-based systems, we find the presence of interlayer excitons at energies higher than the first bright exciton (XA), with non-negligible strength intensity. Our results also show that interlayer excitons in tungsten-based systems are almost degenerate in energy with XA and possess very small oscillator strengths when compared with molybdenum-based systems. At room temperature, and considering the thermal exciton fine-structure population for the XA-exciton, we estimate effective radiative lifetimes in the range of ∼4-14 ns. For higher energy excitons we predict longer effective lifetimes of tens of nanoseconds.

Total absorption spectrum of benzene aggregates obtained from two different approaches.

CONTEXT: The study of molecular aggregation effects on the electronic spectrum is essential for the development of optoelectronic devices. However, investigating the entire valence absorption spectrum of aggregates using quantum mechanical methods is a challenging task. In this work, we perform systematic simulations of the absorption spectrum of benzene molecular clusters up to 35 eV applying two approaches based on time-dependent density functional theory. The results show that depending on the dimer packing, different energy shifts occur for the symmetry allowed [Formula: see text] transition, in comparison to the monomer. The transition intensity increases for the band around 6 eV for larger aggregates from the monomer to dimers and tetramer, indicating the occurrence of the symmetry forbidden (in [Formula: see text] point group) [Formula: see text] [Formula: see text] transition. The benzene crystal exhibits a large redshift following the experimental spectrum. Also, the continuum regions of all spectra show a good agreement with the experiments both in gas and solid phases. METHODS: Geometry optimization of the monomer was carried out with Gaussian 09 software using the PBE0/def2-TZVP level of theory. We used dimers and tetramer molecular geometries extracted from the experimental crystal structure. The absorption spectra were directly obtained by the Liouville-Lanczos TDDFT approach with plane waves basis set or indirectly by TDDFT pseudo-spectra calculated in a [Formula: see text] basis followed by analytic continuation procedure to obtain complex polarizability. The former is available at Quantum ESPRESSO, and the latter was calculated using Gaussian 09 with the post-processing performed with a code previously developed in our group.

Obesity Cut-Off Points Using Prepregnancy Body Mass Index according to Cardiometabolic Conditions in Pregnancy.

Aim: To suggest cut-off points for body mass index (BMI) using gestational hypertension, preeclampsia, and gestational diabetes mellitus (GDM) as cardiometabolic conditions in pregnancy. Methods: In this prospective study, singleton pregnant women from the fetal medicine service of the Brazilian Unified Health System were included. The pregnancy, perinatal, and newborn data were obtained from the clinical medical records. Maternal anthropometry included an assessment of weight and height and the prepregnancy BMI evaluation categorized according to the World Health Organization cut-off points. The area under the curve and confidence interval values from receiver operator curves were generated to identify the optimal cut-off points using prepregnancy BMI with better sensitivity and specificity. Results: Data on 218 pregnancies were analyzed, with 57.9% (n = 124) being classified as overweight/obese, 11% (n = 24) with GDM, 6.9% (n = 15) with preeclampsia, and 11.0% (n = 24) with gestational hypertension. The BMI cut-off points for predicting cardiometabolic conditions were 27.52 kg/m2 (S: 66.7%; E: 63.8%) for women with GDM; 27.40 kg/m2 (S: 73.3%; E: 62.4%; S: 79.2%; E: 64.9%; S: 70.3%; E: 66.3%) for women with preeclampsia, gestational hypertension, and gestational hypertension plus preeclampsia, respectively; and 27.96 kg/m2 (S: 69.6%; E: 65.6%) for women with preeclampsia plus GDM. Conclusion: The findings suggest that the optimal prepregnancy BMI cut-off point is around 27 kg/m2 for pregnant women with maternal cardiometabolic conditions.

Gas-phase C60Hn+q (n = 0-4, q = 0,1) fullerenes and fulleranes: spectroscopic simulations shed light on cosmic molecular structures.

The discovery of C60, C60+, and C70 in the interstellar medium has ignited a profound interest in the astrochemistry of fullerene and related systems. In particular, the presence of diffuse interstellar bands and their association with C60+ has led to the hypothesis that hydrogenated derivatives, known as fulleranes, may also exist in the interstellar medium and contribute to these bands. In this study, we systematically investigated the structural and spectroscopic properties of C60Hn+q (n = 0-4, q = 0,1) using an automated global minimum search and density functional theory calculations. Our results revealed novel global minimum structures for C60H2 and C60H4, distinct from previous reports. Notably, all hydrogenated fullerenes exhibited lower ionization potentials and higher proton affinities compared to C60. From an astrochemical perspective, our results exposed the challenges in establishing definitive spectroscopic criteria for detecting fulleranes using mid-infrared and UV-Vis spectroscopies. However, we successfully identified distinct electronic transitions in the near-infrared range that serve as distinctive signatures of cationic fulleranes. We strongly advocate for further high-resolution experimental studies to fully explore the potential of these transitions for the interstellar detection of fulleranes.

Revisiting the Spectrum of Co(CN)63-: The Role of Correlation, Solvation, and Vibronic and Spin-Orbit Couplings.

In the present work, we revisit the spectrum of the hexacyanocobaltate(III) ion, [Co(CN)6]3-, which has been considered a prototype complex in the coordination chemistry, with modern quantum chemistry methods. The main features have been describing by revealing the role of different effects, such as vibronic coupling, solvation and spin-orbit coupling. The UV-vis spectrum is composed by two bands (1A1g → 1T1g and 1A1g → 1T2g), characterized by singlet-singlet metal-centered transitions, and a more intense third one, characterized by charge transfer transition. There is also a small band shoulder. The first two are symmetry-forbidden transitions in the Oh group. Their intensity can only be explained by a vibronic coupling mechanism. For the band shoulder, additional to vibronic coupling, spin-orbit coupling is also necessary, since the transition is characterized as singlet to triplet, 1A1g → 3T1g.

Size and Quality of Quantum Mechanical Data Set for Training Neural Network Force Fields for Liquid Water.

Molecular dynamics simulations have been used in different scientific fields to investigate a broad range of physical systems. However, the accuracy of calculation is based on the model considered to describe the atomic interactions. In particular, ab initio molecular dynamics (AIMD) has the accuracy of density functional theory (DFT) and thus is limited to small systems and a relatively short simulation time. In this scenario, Neural Network Force Fields (NNFFs) have an important role, since they provide a way to circumvent these caveats. In this work, we investigate NNFFs designed at the level of DFT to describe liquid water, focusing on the size and quality of the training data set considered. We show that structural properties are less dependent on the size of the training data set compared to dynamical ones (such as the diffusion coefficient), and a good sampling (selecting data reference for the training process) can lead to a small sample with good precision.

Birthmarks and birth defects in the head and neck region and claims of past-life memories: A systematic review.

OBJECTIVE: This systematic review compiles published information on subjects with head or neck birth defects or birthmarks in which past-life memories were alleged. DATA SOURCES: Electronic searches were done in April 2022 in the following bibliographic databases: MEDLINE/PubMed, Web of Science, Scopus, EMBASE, and PsycINFO. STUDY SELECTION: References of the included studies and the gray literature were searched. Our sample included six studies reporting 19 cases of birthmarks and birth defects in the head and neck region with alleged past-life memories. DATA EXTRACTION: The features of the lesions varied, and their size ranged between 0.5 to 12 cm. All the cases had interviews with the family of the deceased person and the family of the child with the birthmarks, and nine of them included some type of verified official report. DATA SYNTHESIS: The strength of the evidence in the cases was analyzed using the strength-of-evidence scale. CONCLUSION: This study showed that birthmarks and birth defects in the head and neck region occurred mostly in male children, with the possibility of these marks being caused by the fatal injury of the alleged personality. The literature lacks new cases with high strength of evidence, emphasizing the need for further primary studies.

A multiscale approach for electronic transport simulation of carbon nanostructures in aqueous solvent.

Theoretical works addressing electronic nano-devices operating in an aqueous environment often neglect solvent effects. In order to assess the role played by the polarization effects on the electronic transport properties of solvated graphene, for example in possible bio-sensing applications, we have used here a combination of polarizable force-field molecular dynamics, hybrid quantum mechanics/molecular mechanics (QM/MM) approach, density functional theory, and non-equilibrium Green's function method. We considered different solvation conditions, the presence of defects in graphene, as well as various choices for the partitions between the quantum and classical regions in QM/MM, in which we explicitly account for polarization effects. Our results show that the polarization effects on graphene lead to changes in the structure of interfacial water molecules which are more pronounced in the vicinity of defects. The presence of water leads to increased scattering due to the long-range charge interactions with graphene. At the same time, changes in the conductance due to polarization or salt concentration are found to be small, paving the way for robust electronic nano-devices operating in aqueous environments.

Comparison among several vibronic coupling methods.

A comparison of four approaches to account the vibronic coupling in photoabsorption is performed. The methods considered are nuclear ensemble (NE), direct vibronic coupling (DVC), adiabatic Hessian (AH), and vertical gradient (VG). The case study is the symmetry-forbidden [Formula: see text] [Formula: see text]A[Formula: see text] [Formula: see text] [Formula: see text] [Formula: see text]A[Formula: see text] (n [Formula: see text] [Formula: see text]) transition in formaldehyde. Being forbidden in the equilibrium geometry, this transition is entirely induced by vibronic coupling and constitutes an appropriate case to study the performance of different methods. From DVC, it is found that mode 1 (C=O out-of-plane bending) is the most inducing, followed by mode 6 (in-plane C-H asymmetric stretching) and finally by mode 2 (in-plane C-H asymmetric bending). We were able to correlate 17 out of 20 structures obtained from NE with these modes, showing that these two methods, although different in principle, give comparable results. The simulated spectra were obtained for all methods and compared, and each one has its own advantage. In what concerns the transition studied, NE gives the best description of the spectrum, DVC is the only one that easily gives an absolute value for OOS, and AH and VG are the computationally less expensive methods. From the latter two, VG is the less demanding on computational grounds, since it does not require the excited state Hessian.

Testing alleged mediumistic writing: An experimental controlled study.

CONTEXT: Mediumship is understood as a kind of spiritual experience in which a person (i.e., a medium) claims to be in communication with, or under the control of, spiritual beings. In the last decades there has been a resurgence of studies on psychological, psychiatric and neuroscientific aspects of mediumship, as well as studies assessing the claim that mediums can obtain anomalous information from deceased persons. OBJECTIVE: To assess the evidence for anomalous information reception about deceased people in texts produced through alleged mediumistic writing (psychographic letters) under strictly controlled experimental conditions. METHOD: Eight mediums and ninety-four sitters participated in the study. Eighteen mediumistic writing sessions were carried out using blind proxy sitters. Later, each sitter received the target mediumistic letter and five control letters paired by gender and age. Sitters blindly scored the accuracy of the six letters both with a global score and for each of the objectively verifiable items of information presented on the letters. Scores from target and control letters were compared. RESULTS: There was no difference in global evaluation and specific fit scores between control and target letters. The mediums involved in the research were not able to show evidence for providing anomalous information about deceased people when under our strict controlled conditions. We argue for establishing a reasonable compromise between ecological validity and controlled condition.

Using Neural Network Force Fields to Ascertain the Quality of Ab Initio Simulations of Liquid Water.

Accurately simulating the properties of bulk water, despite the apparent simplicity of the molecule, is still a challenge. In order to fully understand and reproduce its complex phase diagram, it is necessary to perform simulations at the ab initio level, including quantum mechanical effects both for electrons and nuclei. This comes at a high computational cost, given that the structural and dynamical properties tend to require long timescales and large simulation cells. In this work, we evaluate the errors that density functional theory (DFT)-based simulations routinely incur into due time- and size-scale limitations. These errors are evaluated using neural-network-trained force fields that are accurate at the level of DFT methods. We compare different exchange and correlation potentials for properties of bulk water that require large timescales. We show that structural properties are less dependent on the system size and that dynamical properties such as the diffusion coefficient have a strong dependence on the simulation size and timescale. Our results facilitate comparisons of DFT-based simulation results with experiments and offer a path to discriminate between model and convergence errors in these simulations.

Maternal adipose tissue to early preeclampsia risk detection: Is the time to maternal ultrasound beyond fetal evaluation?

INTRODUCTION: This study aims to determine the predictive capacity of isolated maternal periumbilical and epigastric fat measurements during pregnancy to hypertensive outcomes. METHODS: A cohort study was conducted with pregnant women in any trimester and followed until delivery to identify the outcomes of interest, preeclampsia (PE) and gestational hypertension (GH). The predictive capacity of fourth quartile measurements was compared with the first three quartiles of maternal subcutaneous and visceral adipose tissue from the periumbilical site (periumbilical m-SAT and m-VAT) (n = 155) and maternal adipose tissue from the epigastric site (preperitoneal m-SAT and m-VAT) (n = 261). The predictive ability of prepregnant body mass index (BMI) above 30 kg/m2 for PE and GH was also assessed. RESULTS: Fourth quartiles for the periumbilical ultrasound measurements were m-VAT 52.7 mm and m-SAT 21.7 mm. Preperitoneal site presents fourth quartiles m-VAT 15.2 mm and m-SAT 18.6 mm. Both m-VAT and m-SAT maternal periumbilical and preperitoneal sites are unable to predict PE, with the utmost sensitivity attributed to the periumbilical site m-SAT at 54%. The best PE predictor odds ratio (OR) found was the prepregnant BMI consistent with obesity, with an OR of 3.2 (95% CI 1.1-9.4), whereas the best OR to GH predictor was preperitoneal m-SAT with 8.9 (95% CI 2.3-34.6). CONCLUSION: PE pathogenic mechanisms related to maternal abdominal adipose tissue include differences in molecular, cytological, and tissue levels not detected by ultrasound in a quantified gray scale assessment. Periumbilical or epigastric m-VAT use is not able to predict PE during pregnancy.

Modifiable predictors to maternal visceral adipose tissue during pregnancy: A clinical, demographic, and nutritional study.

AIM: Higher amounts of maternal visceral adipose tissue were related to abnormal outcomes in pregnancy. Our objective was to evaluate the impact of modifiable and nonmodifiable predictors related to abnormal amounts of maternal visceral fat during three trimesters of pregnancy. METHODS: Visceral fat thickness was evaluated by ultrasound during three trimesters centered in the maternal epigastrium (preperitoneal m-VAT) and additionally fat thickness evaluation centered at maternal periumbilical region (periumbilical m-VAT) among cases with gestational age below 20 weeks. The fourth quartile was considered abnormal m-VAT and the first three quartiles as normal m-VAT. Nonmodifiable characteristics included maternal age, past term pregnancies, and ethnicity. Modifiable characteristics included pre-pregnancy body mass index (BMI), weight gain, usual macronutrients, and sugar consumption during pregnancy. RESULTS: Preperitoneal m-VAT was assessed in 270 pregnant women and m-VAT periumbilical assessment in 154. The fourth quartile measurement was 15 mm and 53 mm, respectively. Nonmodifiable predictors including maternal age and past term pregnancies significantly impacted the primary study outcome of abnormal periumbilical m-VAT. Having a non-Caucasian ethnicity had a significant impact on the amount of normal preperitoneal m-VAT. Among the modifiable characteristics, both pre-pregnancy BMI and pre-pregnancy obesity impacted the amount of abnormal preperitoneal and periumbilical m-VAT. CONCLUSION: Abnormal amounts of maternal visceral fat during pregnancy are related to nonmodifiable predictors and those present before pregnancy. No impact was found among weight gain during pregnancy or macronutrients and sugar consumption at pregnancy.

Revealing Temozolomide Resistance Mechanisms via Genome-Wide CRISPR Libraries.

Glioblastoma is a severe type of brain tumor with a poor prognosis and few therapy options. Temozolomide (TMZ) is one of these options, however, with limited success, and failure is mainly due to tumor resistance. In this work, genome-wide CRISPR-Cas9 lentiviral screen libraries for gene knockout or activation were transduced in the human glioblastoma cell line, aiming to identify genes that modulate TMZ resistance. The sgRNAs enriched in both libraries in surviving cells after TMZ treatment were identified by next-generation sequencing (NGS). Pathway analyses of gene candidates on knockout screening revealed several enriched pathways, including the mismatch repair and the Sonic Hedgehog pathways. Silencing three genes ranked on the top 10 list (MSH2, PTCH2, and CLCA2) confirm cell protection from TMZ-induced death. In addition, a CRISPR activation library revealed that NRF2 and Wnt pathways are involved in TMZ resistance. Consistently, overexpression of FZD6, CTNNB1, or NRF2 genes significantly increased cell survival upon TMZ treatment. Moreover, NRF2 and related genes detected in this screen presented a robust negative correlation with glioblastoma patient survival rates. Finally, several gene candidates from knockout or activation screening are targetable by inhibitors or small molecules, and some of them have already been used in the clinic.

Nanogap-based all-electronic DNA sequencing devices using MoS2 monolayers.

The realization of nanopores in atom-thick materials may pave the way towards electrical detection of single biomolecules in a stable and scalable manner. In this work, we theoretically study the potential of different phases of MoS2 nanogaps to act as all-electronic DNA sequencing devices. We carry out simulations based on density functional theory and the non-equilibrium Green's function formalism to investigate the electronic transport across the device. Our results suggest that the 1T'-MoS2 nanogap structure is energetically more favorable than its 2H counterpart. At zero bias, the changes in the conductance of the 1T'-MoS2 device can be well distinguished, making possible the selectivity of the DNA nucleobases. Although the conductance fluctuates around the resonances, the overall results suggest that it is possible to distinguish the four DNA bases for energies close to the Fermi level.

Rotational spectrum simulations of asymmetric tops in an astrochemical context.

Rotational spectroscopy plays a major role in the field of observational astrochemistry, enabling the detection of more than 200 species including a plethora of complex organic molecules in different space environments. Those line detections allow correctly determining the sources and physical properties, as well as exploring their morphology, evolutionary stage, and chemical evolution pathways. In this context, quantum chemistry is a powerful tool to the investigation of the molecular inventory of astrophysical environments, guiding laboratory experiments and assisting in both line assignments and extrapolation of the experimental data to unexplored frequency ranges. In the present work, we start by briefly reviewing the rotational model Hamiltonian for asymmetric tops beyond the rigid-rotor approximation, including rotational-vibrational, centrifugal, and anharmonic effects. Then, aiming at further contributing to the recording and analysis of laboratory microwave spectroscopy by means of accessible, less demanding quantum chemical methods, we performed density functional theory (DFT) calculations of the spectroscopic parameters of astrochemically relevant species, followed by their rotational spectrum simulations. Furthermore, dispersion-correction effects combined with different functionals were also investigated. Case studies are the asymmetric tops H2CO, H2CS, c-HCOOH, t-HCOOH, and HNCO. Spectroscopic parameter predictions were overall very close to experiment, with mean percentage errors smaller than 1% for zeroth order and [Formula: see text] for first-order constants. We discuss the implications and impacts of those constants on spectrum simulations, and compare line-frequency predictions at millimeter wavelengths. Moreover, theoretical spectroscopic parameters of c-HCOOH and HNCO are introduced for the first time in this work.

Anthropometrical measurements and maternal visceral fat during first half of pregnancy: a cross-sectional survey.

BACKGROUND: Determining anthropometric measures that indicate different fat deposits can be useful to predict metabolic risk and set specific treatment goals, reducing negative consequences for maternal and fetal health. In cases where pre-gestational weight measure and subsequent body mass index (BMI) values cannot be determined, other anthropometric measurements may be ideal for measuring the nutritional status of pregnant women, especially in low- and middle-income countries. This study aims to identify which anthropometric measurements correlate better with the maternal fat deposits measured by ultrasound. METHODS: A cross-sectional study was conducted with pregnant women from the city of Porto Alegre (city), capital of Rio Grande do Sul (state), southern Brazil, from October 2016 until January 2018. Anthropometrical variables (weight, height, mid-upper arm circumference [MUAC], circumferences of calf and neck and triceps skinfolds [TSF] and subscapular skinfolds [SBSF]), and ultrasound variables (visceral adipose tissue [VAT] and total adipose tissue [TAT]) were collected. To verify the correlation of anthropometric and ultrasound measurements, a non-adjusted and adjusted Spearman correlation was used. The study was approved by the ethics committees. RESULTS: The age median of the 149 pregnant women was 25 years [21-31], pre-pregnancy BMI was 26.22 kg/m² [22.16-31.21] and gestational age was 16.2 weeks [13.05-18.10]. The best measurements correlated with VAT and TAT were MUAC and SBSF, both of which showed a higher correlation than pre-pregnancy BMI. CONCLUSIONS: It is possible to provide a practical and reliable estimate of VAT and TAT from the anthropometric evaluation (MUAC or SBSF) that is low cost, efficient and replicable in an outpatient clinic environment, especially in low- and middle-income countries.

Structure, Stability, and Spectroscopic Properties of Small Acetonitrile Cation Clusters.

Ionization and fragmentation pathways induced by ionizing agents are key to understanding the formation of complex molecules in astrophysical environments. Acetonitrile (CH3CN), the simplest organic nitrile, is an important molecule present in the interstellar medium. In this work, DFT and MP2 calculations were performed in order to obtain the low energy structures of the most relevant cations formed from electron-stimulated ion desorption of CH3CN ices. Selected reaction pathways and spectroscopic properties were also calculated. Our results indicate that the most stable acetonitrile cation structure is CH2CNH+ and that hydrogenation can occur successively without isomerization steps until its complete saturation. Moreover, the stability of distinct cluster families formed from the interaction of acetonitrile with small fragments, such as CHn+, C2Hn+, and CHnCNH+, is discussed in terms of their respective binding energies. Some of these molecular clusters are stabilized by hydrogen bonds, leading to species whose infrared features are characterized by a strong redshift of the N-H stretching mode. Finally, the rotational spectra of CH3CN and protonated acetonitrile, CH3CNH+, were simulated using distinct computational protocols based on DFT, MP2, and CCSD(T) considering centrifugal distortion, vibrational-rotational coupling, and vibrational anharmonicity corrections. By adopting an empirical scaling procedure for calculating spectroscopic parameters, we were able to estimate the rotational frequencies of CH3CNH+ with an expected average error below 1 MHz for J values up to 10.