Publications by authors named "J C Pascual"

1,885 Publications

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Topological phase transition in chiral graphene nanoribbons: from edge bands to end states.

Nat Commun 2021 Sep 20;12(1):5538. Epub 2021 Sep 20.

CIC nanoGUNE-BRTA, Donostia-San Sebastián, Spain.

Precise control over the size and shape of graphene nanostructures allows engineering spin-polarized edge and topological states, representing a novel source of non-conventional π-magnetism with promising applications in quantum spintronics. A prerequisite for their emergence is the existence of robust gapped phases, which are difficult to find in extended graphene systems. Here we show that semi-metallic chiral GNRs (chGNRs) narrowed down to nanometer widths undergo a topological phase transition. We fabricated atomically precise chGNRs of different chirality and size by on surface synthesis using predesigned molecular precursors. Combining scanning tunneling microscopy (STM) measurements and theory simulations, we follow the evolution of topological properties and bulk band gap depending on the width, length, and chirality of chGNRs. Our findings represent a new platform for producing topologically protected spin states and demonstrate the potential of connecting chiral edge and defect structure with band engineering.
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http://dx.doi.org/10.1038/s41467-021-25688-zDOI Listing
September 2021

Challenges in tin perovskite solar cells.

Phys Chem Chem Phys 2021 Sep 17. Epub 2021 Sep 17.

Department of Novel Materials and Interfaces for Photovoltaic Solar Cells, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.

Perovskite solar cells are the rising star of third-generation photovoltaic technology. With a power conversion efficiency of 25.5%, the record efficiency is close to the theoretical maximum efficiency of a single-junction solar cell. However, lead toxicity threatens commercialization efforts and market accessibility. In this context, Sn-based perovskites are a safe alternative. Nevertheless, the efficiency of Sn-based devices falls far behind the efficiency of Pb-based counterparts. This concise review sheds light on the challenges that the field faces toward making Sn-based perovskites the perovskite photovoltaic benchmark. We identified four key challenges: materials and solvents, film formation, Sn(II) oxidation, and energy band alignment. We illustrate every single challenge and highlight the most successful attempts to overcome them. Finally, we provide our opinion on the most promising trends of this field in the future.
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http://dx.doi.org/10.1039/d1cp02596aDOI Listing
September 2021

Noncollinear Magnetic Order in Two-Dimensional NiBr Films Grown on Au(111).

ACS Nano 2021 Sep 7. Epub 2021 Sep 7.

CIC nanoGUNE-BRTA, 20018 Donostia-San Sebastián, Spain.

Metal halides are a class of layered materials with promising electronic and magnetic properties persisting down to the two-dimensional limit. While most recent studies focused on the trihalide components of this family, the rather unexplored metal dihalides are also van der Waals layered systems with distinctive magnetic properties. Here we show that the dihalide NiBr grows epitaxially on a Au(111) substrate and exhibits semiconducting and magnetic behavior starting from a single layer. Through a combination of a low-temperature scanning-tunneling microscopy, low-energy electron diffraction, X-ray photoelectron spectroscopy, and photoemission electron microscopy, we identify two competing layer structures of NiBr coexisting at the interface and a stoichiometrically pure layer-by-layer growth beyond. Interestingly, X-ray absorption spectroscopy measurements revealed a magnetically ordered state below 27 K with in-plane magnetic anisotropy and zero-remanence in the single layer of NiBr/Au(111), which we attribute to a noncollinear magnetic structure. The combination of such two-dimensional magnetic order with the semiconducting behavior down to the 2D limit offers the attractive perspective of using these films as ultrathin crystalline barriers in tunneling junctions and low-dimensional devices.
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http://dx.doi.org/10.1021/acsnano.1c05221DOI Listing
September 2021

A prospective examination of sex differences in posttraumatic autonomic functioning.

Neurobiol Stress 2021 Nov 21;15:100384. Epub 2021 Aug 21.

Department of Psychology, Temple University, Philadelphia, PA, 19121, USA.

Background: Cross-sectional studies have found that individuals with posttraumatic stress disorder (PTSD) exhibit deficits in autonomic functioning. While PTSD rates are twice as high in women compared to men, sex differences in autonomic functioning are relatively unknown among trauma-exposed populations. The current study used a prospective design to examine sex differences in posttraumatic autonomic functioning.

Methods: 192 participants were recruited from emergency departments following trauma exposure ( age = 35.88, 68.2% female). Skin conductance was measured in the emergency department; fear conditioning was completed two weeks later and included measures of blood pressure (BP), heart rate (HR), and high frequency heart rate variability (HF-HRV). PTSD symptoms were assessed 8 weeks after trauma.

Results: 2-week systolic BP was significantly higher in men, while 2-week HR was significantly higher in women, and a sex by PTSD interaction suggested that women who developed PTSD demonstrated the highest HR levels. Two-week HF-HRV was significantly lower in women, and a sex by PTSD interaction suggested that women with PTSD demonstrated the lowest HF-HRV levels. Skin conductance response in the emergency department was associated with 2-week HR and HF-HRV only among women who developed PTSD.

Conclusions: Our results indicate that there are notable sex differences in autonomic functioning among trauma-exposed individuals. Differences in sympathetic biomarkers (BP and HR) may have implications for cardiovascular disease risk given that sympathetic arousal is a mechanism implicated in this risk among PTSD populations. Future research examining differential pathways between PTSD and cardiovascular risk among men versus women is warranted.
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http://dx.doi.org/10.1016/j.ynstr.2021.100384DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8397921PMC
November 2021

Development and validation of a LC-MS/MS method for quantitation of 3-hydroxypentanoic acid and 3-oxopentanoic acid in human plasma and its application to a clinical study of glucose transporter type I deficiency (G1D) syndrome.

J Pharm Biomed Anal 2021 Aug 27;205:114335. Epub 2021 Aug 27.

Department of Pharmacy Practice, Jerry H. Hodge School of Pharmacy, Texas Tech University Health Sciences Center, Dallas, TX 75235, USA; Clinical Pharmacology and Experimental Therapeutics Center, Jerry H. Hodge School of Pharmacy, Texas Tech University Health Sciences Center, Dallas, TX 75235, United States; Department of Pharmaceutical Sciences, Jerry H. Hodge School of Pharmacy, Texas Tech University Health Sciences Center, Dallas, TX 75235, United States. Electronic address:

Interest in human and experimental animal metabolism of substrates containing an odd number of carbons capable of fueling the tricarboxylic acid cycle such as heptanoic acid has motivated us to develop and validate a selective and specific liquid chromatographytandem mass spectrometric method for the simultaneous, quantitative determination of the ketone body byproducts 3-hydroxypentanoic acid and 3-oxopentanoic acid in plasma. Human plasma samples were protein-precipitated with methanol containing 0.2% formic acid. Chromatographic resolution was achieved on a Phenomenex Luna C18 column using gradient elution with mobile phases of water containing 0.1% formic acid and methanol containing 0.1% formic acid at 0.3 mL/min flow rate. The retention times of 3-hydroxypentanoic acid, 3-oxopentanoic acid and sulbactam (internal standard) were 3.85, 4.23, and 5.11 min, respectively. Validation was conducted in accordance with United States Food and Drug Administration guidance. The validated range of 3-hydroxypentanoic acid was 0.078-5 µg/mL and 0.156-10 µg/mL for 3-oxopentanoic acid. The method was accurate and precise over this range and exhibited 10-fold dilution integrity in human plasma. Recovery> 88% was achieved for analytes and internal standard. There was no matrix effect observed in human plasma. Both 3-hydroxypentanoic acid and 3-oxopentanoic acid were stable across conditions including autosampler, benchtop and freeze-thaw, as well as demonstrated long-term stability at -80 °C. The method was applied to the measurement of 3-hydroxypentanoic acid and 3-oxopentanoic acid concentrations in plasma from subjects receiving the triglyceride triheptanoin (as a source of heptanoate) for the experimental treatment of glucose transporter type I deficiency (G1D) syndrome.
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http://dx.doi.org/10.1016/j.jpba.2021.114335DOI Listing
August 2021
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