Fundamental Gap Research Articles

Valley-Polarized Quantum Hall Phase in a Strain-Controlled Dirac System.

In multivalley systems, the valley pseudospin offers rich physics going from encoding of information by its polarization (valleytronics), to exploring novel phases of matter when its degeneracy is changed. Here, by strain engineering, we reveal fully valley-polarized quantum Hall phases in the Pb_{1-x}Sn_{x}Se Dirac system. Remarkably, when the valley energy splitting exceeds the fundamental band gap, we observe a "bipolar quantum Hall phase," heralded by the coexistence of hole and electron chiral edge states at distinct valleys in the same quantum well. This suggests that spatially overlaid counterpropagating chiral edge states emerging at different valleys do not interfere with each other.

Induced ferromagnetism in Ni(II) doped ZnO monolayers via Al co-doping and their optical characteristics: ab initio study

For applications in magneto-electronic devices, diluted magnetic semiconductors (DMSs) usually exhibit spin-dependent coupling and induced ferromagnetism at high Curie temperatures. The processes behind the behavior of optical emission and ferromagnetism, which can be identified by complicated microstructural and chemical characteristics, are still not well understood. In this study, the impact of Al co-doping on the electronic, optical, and magnetic properties of Ni(II) doped ZnO monolayers has been investigated using first principles calculations. Ferromagnetism in the co-doped monolayer is mainly triggered by the exchange coupling between the electrons provided by Al co-doping and Ni(II)-d states; therefore, the estimated Curie temperature is greater than room temperature. The spin–spin couplings in mono-doped and co-doped monolayers were explained using the band-coupling mechanism. Based on the optical study, we observed that the Ni-related absorption peak occurred at 2.13–2.17 eV, showing a redshift as Ni concentrations increased. The FM coupling between Ni ions in the co-doped monolayer may be responsible for the reduction in the fundamental band gap seen with Al co-doping. We observed peaks in the near IR and visible regions of the co-doped monolayer, which improve the optoelectronic device’s photovoltaic performance. Additionally, the correlation between optical characteristics and spin–spin couplings has been studied. We found that the Ni(II)’s d–d transition bands or fundamental band gap in the near configuration undergoes a significant shift in response to AFM and FM coupling, whereas in the far configuration, they have a negligible shift due to the paramagnetic behavior of the Ni ions. These findings suggest that the magnetic coupling in DMS may be utilized for controlling the optical characteristics.

Reanalysis of NOAA H2 observations: implications for the H2 budget

Abstract. Hydrogen (H2) is a promising low-carbon alternative to fossil fuels for many applications. However, significant gaps in our understanding of the atmospheric H2 budget limit our ability to predict the impacts of greater H2 usage. Here we use NOAA H2 dry air mole fraction observations from air samples collected from ground-based and ship platforms during 2010–2019 to evaluate the representation of H2 in the NOAA GFDL-AM4.1 atmospheric chemistry-climate model. We find that the base model configuration captures the observed interhemispheric gradient well but underestimates the surface concentration of H2 by about 10 ppb. Additionally, the model fails to reproduce the 1–2 ppb yr−1 mean increase in surface H2 observed at background stations. We show that the cause is most likely an underestimation of current anthropogenic emissions, including potential leakages from H2-producing facilities. We also show that changes in soil moisture, soil temperature, and snow cover have most likely caused an increase in the magnitude of the soil sink, the most important removal mechanism for atmospheric H2, especially in the Northern Hemisphere. However, there remains uncertainty due to fundamental gaps in our understanding of H2 soil removal, such as the minimum moisture required for H2 soil uptake, for which we performed extensive sensitivity analyses. Finally, we show that the observed meridional gradient of the H2 mixing ratio and its seasonality can provide important constraints to test and refine parameterizations of the H2 soil sink.

B cells and the stressed brain: emerging evidence of neuroimmune interactions in the context of psychosocial stress and major depression.

The immune system has emerged as a key regulator of central nervous system (CNS) function in health and in disease. Importantly, improved understanding of immune contributions to mood disorders has provided novel opportunities for the treatment of debilitating stress-related mental health conditions such as major depressive disorder (MDD). Yet, the impact to, and involvement of, B lymphocytes in the response to stress is not well-understood, leaving a fundamental gap in our knowledge underlying the immune theory of depression. Several emerging clinical and preclinical findings highlight pronounced consequences for B cells in stress and MDD and may indicate key roles for B cells in modulating mood. This review will describe the clinical and foundational observations implicating B cell-psychological stress interactions, discuss potential mechanisms by which B cells may impact brain function in the context of stress and mood disorders, describe research tools that support the investigation of their neurobiological impacts, and highlight remaining research questions. The goal here is for this discussion to illuminate both the scope and limitations of our current understanding regarding the role of B cells, stress, mood, and depression.

Mitochondrial genome and nuclear ribosomal RNA analysis place Alveonasus lahorensis within the Argasinae and suggest that the genus Alveonasus is paraphyletic.

Two major families exist in ticks, the Argasidae and Ixodidae. The Argasidae comprise 2 sub-families, Argasinae and Ornithodorinae. The placement into subfamilies illuminate differences in morphological and molecular systematics and is important since it provides insight into evolutionary divergence within this family. It also identifies fundamental gaps in our understanding of argasid evolution that provide directions for future research. Molecular systematics based on mitochondrial genomics and 18S/28S ribosomal RNA confirmed the placement of various genera and subgenera into the Argasinae: Argas (including Argas and Persicargas), Navis, Ogadenus, Otobius lagophilus, Proknekalia, Secretargas and the Ornithodorinae: Alectorobius, Antricola (including Antricola and Parantricola), Carios, Chiropterargas, Nothoaspis, Ornithodoros (including Microargas, Ornamentum, Ornithodoros sensu strictu, Pavlovskyella), Otobius sensu strictu, Reticulinasus and Subparmatus. The position of Alveonasus remains controversial since traditional taxonomy placed it in the Ornithodorinae, while cladistic and limited molecular analysis placed it in the Argasinae. The current study aimed to resolve the systematic position of Alveonasus using mitochondrial genomic and 18S/28S ribosomal RNA systematics by sequencing the type species Alveonasus lahorensis from Pakistan. In addition, the mitochondrial genomes for Argas reflexus and Alectorobius kelleyi are reported from Germany and the USA, respectively. The systematic data unambiguously place Alveonasus in the Argasinae and also suggest that Alveonasus may be another paraphyletic genus.

Wellbeing in the age of virtual teams and workplace automation – a systematic review and future research agenda

Purpose In the wake of the COVID-19 pandemic organisations are adapting to a new environment of global talent shortages, economic uncertainty and geo-political turmoil. As an outcome, the organisational strategies of digital transformation and remote working have been accelerated in the race to boost innovation, competitivity and attract staff. This has led to the rise of two new organisational dynamics: the increase of virtual teams (VTs) and focus on widespread work automation. However, despite the rise of these two related phenomena, literature does not connect them as one research area, and there is a gap in the understanding of the new employee wellbeing needs they form and how to respond to them. This paper aims to bridge this gap through a systematic literature across these areas. Design/methodology/approach This paper conducts a systematic literature review across the areas of leadership, VTs and automation over the past three years. Findings In this review, a number of newly arising employee wellbeing needs are identified such as fear of job displacement, a lack of self-efficacy and social cohesion, poor relationships with leaders and more. In addition, this paper recommends three fundamental research gaps to be addressed by future studies: 1. How to build and cultivate the new leadership skills needed to support VTs and workplace automation? 2. How to design work in a way that caters for employee wellbeing needs when operating in VTs or hybrid teams and working on or with workplace automation? 3. How to design work in a way that builds and emphasises the new employee skillsets to support augmentation and solves for the new employee wellbeing needs experienced by workplace automation? Originality/value This paper provides a novel contribution to literature by centralising current schools of thought across the cross-disciplinary themes and synthesising literature to recommend new wellbeing and leadership skills for organisations to focus on, alongside producing a new research agenda for scholars to focus.

Excitons, optical spectra, and electronic properties of semiconducting Hf-based MXenes.

Semiconducting MXenes are an intriguing two-dimensional (2D) material class with promising electronic and optoelectronic properties. Here, we focused on recently prepared Hf-based MXenes, namely, Hf3C2O2 and Hf2CO2. Using the first-principles calculation and excited state corrections, we proved their dynamical stability, reconciled their semiconducting behavior, and obtained fundamental gaps by using the many-body GW method (indirect 1.1 and 2.2eV; direct 1.4 and 3.5eV). Using the Bethe-Salpeter equation, we subsequently provided optical gaps (0.9 and 2.7eV, respectively), exciton binding energies, absorption spectra, and other properties of excitons in both Hf-based MXenes. The indirect character of both 2D materials further allowed for a significant decrease of excitation energies by considering indirect excitons with exciton momentum along the Γ-M path in the Brillouin zone. The first bright excitons are strongly delocalized in real space while contributed by only a limited number of electron-hole pairs around the M point in the k-space from the valence and conduction band. A diverse range of excitonic states in Hf3C2O2 MXene lead to a 4% and 13% absorptance for the first and second peaks in the infrared region of absorption spectra, respectively. In contrast, a prominent 28% absorptance peak in the visible region appears in Hf2CO2 MXene. Results from radiative lifetime calculations indicate the promising potential of these materials in optoelectric devices requiring sustained and efficient exciton behavior.

Phonon and electronic properties of semiconducting silicon nitride bilayers

The two-dimensional (2D) IV-V semiconductors have attracted much attention due to their fascinating electronic and optical properties. In this work, we predicted three phases of silicon nitrides, denoted α-Si2N2, β-Si2N2, and γ-Si4N4, respectively. Both α-Si2N2 and β-Si2N2 consist of two buckled SiN sheets, and γ-Si4N4 consists of two puckered SiN sheets. It is challenging to transform between α-Si2N2 and β-Si2N2 because of the high energy barrier. The three dynamically stable bilayers are semiconductors with fundamental indirect band gaps from 0.25 eV to 2.92 eV. As expected, only the s and p orbitals contribute to the electronic states, and the pz orbitals dominate near the Fermi level. Furthermore, insulator-metal transitions occur in α-Si2N2 and β-Si2N2 under the biaxial strain of 16 %. These materials perhaps have potential applications in microelectronics and spintronics.

Abstract 1786: Metabolic rewiring induced by protein or calorie restriction provides unique therapeutic vulnerabilities in translocation and select clear cell renal cell carcinomas

Abstract While the approval of several combinations with immune checkpoint inhibitors have significantly improved the outcome of kidney cancer patients, advanced clear cell and non-clear cell renal cell carcinoma (RCC) remain a clinical challenge. There has been a longstanding interest in using dysregulated metabolism as a therapeutic target due to its association with the pathogenesis and progression of several cancer types. As one of these highly metabolic tumors, RCC has the potential to greatly benefit from strategies targeting tumor metabolism. Dietary interventions are an innovative adjunct therapy that has the potential to induce a wide range of anti-cancer effects by disrupting metabolism due to the role diet plays in providing tumors with macromolecules for energy metabolism. Unfortunately, tumor cell plasticity, intratumor heterogeneity, and a lack of understanding regarding metabolic vulnerabilities in tumors limit the efficacy of implementing these strategies and a fundamental gap in the field remains as to how basic metabolic requirements of the tumor can be targeted with specific dietary interventions. In this study, the inherent metabolic phenotypes of translocation RCC (tRCC) and clear cell RCC (ccRCC) were characterized by integrating in vivo metabolomics and transcriptomics data, assessing mitochondrial and glycolytic activity in vitro via Seahorse, and performing immunohistochemical analyses of patient samples. Interestingly, the respective mitochondrial and glycolytic dependencies in tRCC and ccRCC patient-derived xenograft (PDX) models appear to influence the response to nutrient deprivation as seen by in vitro assays conducted after amino acid or glucose restriction. Importantly, these results indicate that dietary interventions may be able to selectively target metabolic vulnerabilities in tRCC and ccRCC. Ongoing combination studies with either protein or calorie restriction and targeted therapies, such as standard of care receptor tyrosine-kinase inhibitors, suggest the benefit of using dietary interventions as an adjunct therapy in RCC. Overall, these studies reveal that selective dietary interventions alter the metabolic landscape of RCC and expose vulnerabilities that can be exploited with targeted therapy. As dietary interventions are a safe, affordable, and potentially well tolerated adjunct therapy, we anticipate that the results of these studies will provide the biologic and mechanistic support for translating this strategy to advanced RCC patients. Citation Format: Sabrina A. Orsi, Christopher Rupert, Sean Colligan, Musea Chang, Abbas Jawadwala, Ilaria Delle Fontane, Filomena de Nigris, Roberto Pili. Metabolic rewiring induced by protein or calorie restriction provides unique therapeutic vulnerabilities in translocation and select clear cell renal cell carcinomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1786.

Abstract 5403: Meeting the Physical Activity Guidelines is associated with increased CD8+ T-cell density in the tumor microenvironment of breast cancer patients

Abstract Background: Our current understanding of how physical activity (PA) is associated with immunity in breast cancer (BC) patients is based on pre-clinical evidence gleaned from mouse models or immune cells in the circulating blood, which may not be reflective of the tumor immune microenvironment (TIME). Whether self-reported PA is associated with immune cell infiltration in the breast TIME, the most relevant site for prognosis, remains a fundamental gap in knowledge. Herein, we examined the association of self-reported PA in the year before BC diagnosis with CD8+ T-cell density in the breast TIME. As prior evidence from healthy adults suggests the relationship between exercise and immunity is not linear, we hypothesized that patients reporting the highest PA level would not have the highest CD8+ T-cell density in their tumor. Methods: We leveraged data and tumor samples from 685 women with BC (548 self-identified Black and 137 self-identified White) enrolled in the Women’s Circle of Health Study and the Women’s Circle of Health Follow-Up Study. CD8+ T-cell density per square millimeter of tumor tissue was derived from IHC staining of tissue microarrays. Weekly PA in the year before diagnosis was categorized as inactive; low active (<7.5 MET hours/week); moderately active [7.5-14.9 MET hours/week, the equivalent of meeting the minimum PA Guidelines (PAG)]; or high active (≥15.0 MET-hours/week, exceeding the minimum PAG). Log transformed mean CD8+ T-cell densities were compared by PA level using t-tests and multivariable linear regression with adjustment for age, race, estrogen receptor status, and tumor grade. Results: Meeting the minimum PA Guidelines was associated with significantly higher CD8+ T-cell density in the breast TIME [120.4 (353.6)] in comparison to inactivity [62.0 (154.5), p=0.02]. Although there were also distinct differences in T-cell density between moderate and low-active patients [120.4 (353.6) versus 69.5 (172.6), p=0.10] and moderate and high-active patients [120.4 (353.6) versus 80.7 (223.3), p=0.051], associations were shy of significance. Multivariable linear regression analyses confirmed that moderately active patients had significantly higher CD8+ T-cell density in comparison to inactive patients, overall (p=0.029), and among Black patients (p=0.021). Conclusions: In comparison to inactivity, BC patients meeting the PAG (moderate activity) had significantly increased CD8+ T-cell density in their tumor, which is associated with better survival outcomes. This new translational knowledge suggests exercise-induced immunomodulation may be an important molecular mechanism underlying the association of PA with improved BC survival. As the immune system is a key player in treatment response and efficacy, further study of the role that PA ancillary to therapy may play in improving treatment and survival outcomes is warranted. Citation Format: Rikki Cannioto, Angela Omilian, Evan Davis, Lucas Mendicino, Scott Abrams, Bo Qin, Chi-Chen Hong, Elisa Bandera, Song Yao, Christine Ambrosone. Meeting the Physical Activity Guidelines is associated with increased CD8+ T-cell density in the tumor microenvironment of breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5403.

Propagation of fundamental gap solitons in the fractional Schrödinger equation with combined linear and nonlinear optical lattices

The propagation of two-dimensional fundamental gap solitons is investigated in the framework of fractional Schrödinger equation with combined linear and nonlinear optical lattices. It is revealed that solitons exist in the first gap and can be stable in a large region. With a phase tilt, the fundamental gap solitons undergo oscillation during the propagation. And the oscillation is enhanced with the increase of the tilt. In addition, propagation of fundamental gap solitons are also studied by longitudinal modulation of Lévy index, nonlinear strength, and period of nonlinear lattices, respectively. With the sudden variation of Lévy index, the fundamental gap solitons undergo oscillation and become unstable, whereas the gradual variation generates the stable soliton. However, both sudden and gradual decreases of nonlinear strength can lead to the distortion of the soliton due to the weak nonlinearity. Interestingly, the small longitudinal modulation of the period of the nonlinear lattice has little effect on the propagation of fundamental gap soliton, while the effect of the large variation of the period of the nonlinear lattice is apparent.

Investigation of optical and dispersion parameters poly vinyl alcohol doped Safranin O dye (PVA/SO) thin film

Optical characteristics of polyvinyl alcohol/Safranin O dye (PVA/SO) thin films prepared by casting technique have been examined. Compositions and crystalline features of PVA/SO thin films are investigated with X-Ray Diffraction analyses. Ultraviolet–Visible spectroscopy has been utilized to measure the absorption and transmission optical properties of the thin films through the wavelength range 300-900 nm. Two regions can be recognized in absorption coefficient related to the direct band gaps, which are about 3.93 eV of the fundamental energy gap and 2.11eV of the onset gap. The theoretical WempleDiDomenico model has been performed to quantify the static refractive index n and the dispersion energy in addition to the oscillation energy (Eo). The results reveal that the data of the refractive index dispersion in this model obeyed the single oscillator, which is used to deduce the dispersion and the high frequency dielectric constant. In the examined wavelength range, it has been investigated the complex dielectric constant of PVA/SO dye thin films. The ratio of the carrier concentration to the effective mass has been estimated. Oscillation energy values have been examined in this study by describing the expression Eo ≈ Eg and checking the Wemple-DiDomenico model. PVA/SO thin films have interesting physical properties for solar cell applications.

Virtual BUILD Research Collaboratory: A biomedical data science training using innovative pedagogy to address structures of racism and inequitable stress for undergraduates of color.

The unprecedented events of 2020 required a pivot in scientific training to better prepare the biomedical research workforce to address global pandemics, structural racism, and social inequities that devastate human health individually and erode it collectively. Furthermore, this pivot had to be accomplished in the virtual environment given the nation-wide lockdown. These needs and context led to leveraging of the San Francisco Building Infrastructure Leading to Diversity (SF BUILD) theories of change to innovate a Virtual BUILD Research Collaboratory (VBRC). The purpose of VBRC was to train Black, Indigenous, and people of color (BIPOC) students to apply their unique perspectives to biomedical research. These training activities were evaluated using a pre-post survey design that included both validated and new psychosocial scales. A new scale was piloted to measure culturally relevant pedagogy. VBRC scholars increased science identity on two items: thinking of myself as a scientist (+1point, p = 0.006) and belonging to a community of scientists (+1point, p = 0.069). Overall, scholars perceived stress also decreased over VBRC (-2.35 points, p = 0.02). Post VBRC, scholars had high agency scores (μ = 11.02, Md = 12, range = 6-12, σ = 1.62) and cultural humility scores (μ = 22.11, Md = 23, range = 12-24, σ = 2.71). No notable race/ethnic differences were found in any measures. Taken together, our innovative approach to data science training for BIPOC in unprecedented times shows promise for better preparing the workforce critically needed to address the fundamental gaps in knowledge at the intersection of public health, structural racism, and biomedical sciences.

Strongly Bound Frenkel Excitons on TiO2 Nanoparticles: An Evolutionary and DFT Approach

An evolutionary algorithm was employed to locate the global minimum of TiO2n nanoparticles with n=2–20. More than 61,000 structures were calculated with a semiempirical method and reoptimized using density functional theory. The exciton binding energy of TiO2 nanoparticles was determined through the fundamental and optical band gap. Frenkel exciton energy scales as EB eV=8.07/n0.85, resulting in strongly bound excitons of 0.132–1.2 eV for about 1.4 nm nanoparticles. Although the exciton energy decreases with the system size, these tightly bound Frenkel excitons inhibit the separation of photogenerated charge carriers, making their application in photocatalysis and photovoltaic devices difficult, and imposing a minimum particle size. In contrast, the exciton binding energy of rutile is 4 meV, where the Wannier exciton energy scales as EB eV=13.61 μ/ε2. Moreover, the Wannier excitons in bulk TiO2 are delocalized according to the Bohr radii: 3.9 nm for anatase and 7.7 nm for rutile.

The Franz–Keldysh effect in the optical absorption spectrum of a TlGaSe2 layered semiconductor caused by charged native defects

The Franz–Keldysh effect in the optical absorption edge of a bulk TlGaSe2 layered semiconductor poled under an external electric field was investigated in the present work. The Franz–Keldysh shift below the optical bandgap absorption region, as well as the quasi-periodic oscillations above the fundamental bandgap of TlGaSe2, were observed. The measured changes in optical light absorption of the TlGaSe2 sample were revealed after poling processing. The poling technique is used to produce the built-in internal electric field within the TlGaSe2 semiconductor. The frozen-in internal electric field in TlGaSe2 was experimentally monitored through changes in the lineshape of the absorption spectra at the fundamental band edge. The observed results are accurately fitted with the theoretical lineshape function of the Franz–Keldysh absorption tail below the bandgap of TlGaSe2 and quasi-periodic oscillations above the bandgap. A good agreement between the theoretical and experimental results was observed. The present study demonstrated that the Franz–Keldysh effect can be used to identify and characterize the localized internal electric fields originating from electrically active native imperfections in the TlGaSe2 crystals.

New reference genomes to distinguish the sympatric malaria parasites, Plasmodium ovale curtisi and Plasmodium ovale wallikeri

Despite Plasmodium ovale curtisi (Poc) and wallikeri (Pow) being important human-infecting malaria parasites that are widespread across Africa and Asia, little is known about their genome diversity. Morphologically identical, Poc and Pow are indistinguishable and commonly misidentified. Recent rises in the incidence of Poc/Pow infections have renewed efforts to address fundamental knowledge gaps in their biology, and to develop diagnostic tools to understand their epidemiological dynamics and malaria burden. A major roadblock has been the incompleteness of available reference assemblies (PocGH01, PowCR01; ~ 33.5 Mbp). Here, we applied multiple sequencing platforms and advanced bioinformatics tools to generate new reference genomes, Poc221 (South Sudan; 36.0 Mbp) and Pow222 (Nigeria; 34.3 Mbp), with improved nuclear genome contiguity (> 4.2 Mbp), annotation and completeness (> 99% Plasmodium spp., single copy orthologs). Subsequent sequencing of 6 Poc and 15 Pow isolates from Africa revealed a total of 22,517 and 43,855 high-quality core genome SNPs, respectively. Genome-wide levels of nucleotide diversity were determined to be 2.98 × 10–4 (Poc) and 3.43 × 10–4 (Pow), comparable to estimates for other Plasmodium species. Overall, the new reference genomes provide a robust foundation for dissecting the biology of Poc/Pow, their population structure and evolution, and will contribute to uncovering the recombination barrier separating these species.

Low-Temperature X-ray Microanalysis Sheds New Light on Mineral Nutrition Aspects of Insect Leaf Galling.

Manipulation of host plant physiology by leaf-galling insects is a multifaceted process. Among fundamental knowledge gaps surrounding this scientifically intriguing phenomenon is the appropriation of plant mineral nutrients and moisture for galling advantage. Small, soluble mineral ions and watery cell contents in dense gall tissues risk disruption during routine sample preparations. In this study, an X-ray microanalysis was applied to investigate gall mineral nutrition. Morphologically diverse leaf galls were sampled from three Australian rainforest tree species. Using cryo-analytical scanning electron microscopy, real-time X-ray analytical maps of cellular mineral nutrients and water were integrated with anatomical images of gall and leaf cross-sectional surfaces. A comparison of host-leaf and gall anatomies bore direct evidence of drastic changes to leaf cells through the galling process. Distinct "wet" and "dry" regions within galls were anatomically and/or chemically differentiated, suggesting specific functionality. "Wet" regions comprising hydrated cells including soft gall-cavity linings where larvae are known to feed contained soluble plant mineral nutrients, while C-rich "dry" tissues largely devoid of mineral nutrients likely contribute structural support. Mapping immobile nutrients such as Mn may provide a means of "matching" specific gall cell types to those in ungalled host-leaf tissues. The findings here provided otherwise inaccessible insights into leaf-gall mineral nutrition.

Toward the development of an ecosystem model ensemble to support adaptive management in Lake Ontario

Notwithstanding the continuing advancement of our understanding of the broader ecosystem functioning in Lake Ontario, emerging evidence suggests that there are fundamental knowledge gaps to accurately describe the relationship between exogenous phosphorus (P) loading and in-lake total phosphorus (TP) concentrations. The whole-lake load appears to frequently exceed the Great Lakes Water Quality Agreement (GLWQA) interim target of 7000 metric tonnes·year−1, although the offshore-water P concentrations are consistently below the GLWQA interim substance concentration objective of 10 µg TP·L–1. Contrasting ecological conditions prevail in different locations of Lake Ontario, owing to the significant urban footprint along the shoreline but also the capacity of dreissenid mussels to sequester P in the littoral zone. Specifically, low ambient P levels threaten fisheries productivity in offshore waters, while nuisance benthic algae (predominantly Cladophora) and toxin-producing cyanobacteria blooms affect the water quality in the nearshore zone. The present study offers a technical analysis of the recent and ongoing modelling work that has been conducted in Lake Ontario and can be potentially used to address the multitude of ecosystem management challenges. Our aim is to provide an overview of all the major models developed by identifying their fundamental assumptions, structural attributes, and general consistency against empirical knowledge derived from the system. The existing modelling work has opted for parsimonious representations of the lower food web coupled with granular grid configurations to effectively link hydrodynamic processes and mass transport between nearshore and offshore waters. The establishment of comprehensive ecophysiological modules that will recreate the mechanisms underlying the interplay among bioavailable phosphorus, planktonic dynamics, dreissenid mussels, and Cladophora is a critical undertaking to reproduce the water quality conditions in the nearshore zone of Lake Ontario. Striving to integrate the lower food web with fisheries and ecosystem-service modelling, we also offer a technical analysis of knowledge gaps and monitoring-assessment objectives that should be addressed to ensure that ecosystem processes of management interest are adequately measured and the local modelling enterprise is focused on suitable performance indicators.

MORPHOFUNCTIONAL POLYMORPHISM OF THE MUCOSA IN CHRONIC LARINGITIS

Chronic laryngitis, characterized by inflammation of laryngeal tissue, is the most commonly diagnosed organic voice disorder, but treatments targeting putative etiologic factors have shown limited effectiveness. A major obstacle to the development of improved treatments for chronic laryngitis is a fundamental gap in knowledge regarding the pathophysiology of laryngeal inflammation. This article provides a review of the literature on the polymorphism of chronic laryngitis.

The deep-acceptor nature of the chalcogen vacancies in 2D transition-metal dichalcogenides

Chalcogen vacancies in the semiconducting monolayer transition-metal dichalcogenides (TMDs) have frequently been invoked to explain a wide range of phenomena, including both unintentional p-type and n-type conductivity, as well as sub-band gap defect levels measured via tunneling or optical spectroscopy. These conflicting interpretations of the deep versus shallow nature of the chalcogen vacancies are due in part to shortcomings in prior first-principles calculations of defects in the semiconducting two-dimensional TMDs that have been used to explain experimental observations. Here we report results of hybrid density functional calculations for the chalcogen vacancy in a series of monolayer TMDs, correctly referencing the thermodynamic charge transition levels to the fundamental band gap (as opposed to the optical band gap). We find that the chalcogen vacancies are deep acceptors and cannot lead to n-type or p-type conductivity. Both the (0/−1) and (−1/−2) transition levels occur in the gap, leading to paramagnetic charge states S=1/2 and S = 1, respectively, in a collinear-spin representation. We discuss trends in terms of the band alignments between the TMDs, which can serve as a guide to future experimental studies of vacancy behavior.