bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of the source gap on transmission efficiency of a quadrupole mass spectrometer
Authors: Antony Joseph Mariya J. , McIntosh David G. , Gibson J. Raymond , Taylor Stephen 
Published: February 2018

RationaleRecent trends towards miniature and portable quadrupole mass spectrometry (QMS) entail challenges in instrumental sensitivity, which is influenced by 3D fringe field effects on ion transmission in the Quadrupole Mass Filter (QMF). The relationship of these effects with the gap from the ion source to the QMF entrance (source gap) is significant and little explored. We examine transmission characteristics experimentally and use the results to test the predictive accuracy of a recently developed 3D QMF simulation model. The model is then applied to directly investigate optimal transmission m/z ranges across multiple source gaps.MethodsA portable single filter quadrupole mass spectrometer is used to analyse transmission characteristics across a range of common gases. We use an experimental approach originally proposed by Ehlert, enhanced with a novel method for absolute calibration of the transmission curve. Custom QMF simulation software employs the boundary element method (BEM) to compute accurate 3D electric fields. This is used to study the effects of the source gap on transmission efficiency.ResultsExperimental findings confirm a centrally peaked transmission curve; simulations correctly predict the optimal transmission location (in m/z) and percentage, and extend the experimental trend. We compare several methods for determining fringe field length, demonstrating how the size of the physical source gap influences both the length and the intensity of the fringe field at the QMF entrance. A complex relationship with ion transmission is revealed in which different source gaps promote optimal transmission at differing m/z ranges.ConclusionsThe presented results map the relationship between the source gap and transmission efficiency for the given instrument, using a simulation method transferrable to other setups. This is of importance to miniature and portable quadrupole mass spectrometers design for specific applications, for the first time enabling the source gap to be tailored for optimal transmission in the desired mass range.
Quantification of volatile compounds released by roasted coffee by selected ion flow tube mass spectrometry
Authors: Dryahina Kseniya , Smith David , Španěl Patrik 
Published: February 2018

RationaleThe major objective of this exploratory study was to implement selected ion flow tube mass spectrometry, SIFT‐MS, as a method for the on‐line quantification of the volatile organic compounds, VOCs, in the headspace of the ground roasted coffee.MethodsThe optimal precursor ions and characteristic analyte ions were selected for real‐time SIFT‐MS quantification of those VOCs that are the most abundant in the headspace or known to contribute to aroma. NO+ reagent ion reactions were exploited for most of the VOC analyses. VOC identifications were confirmed using gas chromatography/mass spectrometry, GC/MS, coupled with solid‐phase microextraction, SPME.ResultsThirty‐one VOCs were quantified, including several alcohols, aldehydes, ketones, carboxylic acids, esters and some heterocyclic compounds. Variations in the concentrations of each VOC in the seven regional coffees were typically less than a factor of 2, yet concentrations patterns characteristic of the different regional coffees were revealed by heat map and principal component analyses. The coefficient of variation in the concentrations across the seven coffees was typically below 24% except for furfural, furan, methylfuran and guaiacol.ConclusionsThe SIFT‐MS analytical method can be used to quantify in real time the most important odoriferous VOCs in ground coffee headspace to sufficient precision to reveal some differences in concentration patterns for coffee produced in different countries.
Diel activity and foraging mode of juvenile Arctic charr in fluctuating water flow
Authors: Larranaga N. , Valdimarsson S.K. , Linnansaari T. , Steingrímsson S.Ó. 
Published: February 2018

AbstractStreams fluctuate in water flow because of natural (e.g., rain) and human‐induced events (e.g., hydropeaking). Magnitude, frequency, and predictability of these events can have drastic consequences for fish populations. We studied how rapid modifications of water flow affect diel activity and foraging mode of juvenile Arctic charr Salvelinus alpinus in stream enclosures exposed to either stable (intermediate) or fluctuating (low vs. high) water flow. Under stable conditions, Arctic charr showed limited activity (9.4%). In fluctuating water flow, charr increased activity during low flow periods, especially during the first hours after the flow decreased, but ceased activity almost completely at high flow. Charr were mostly nocturnal, and more nocturnal at low than intermediate water flow. Fish were more mobile and swam faster during prey search and attacked prey at longer distances at low water flow. Activity and foraging mode differed between the first and second day after reduced water flow, suggesting that Arctic charr require time to adjust their foraging behaviour. This study demonstrates the importance of behavioural flexibility for population ecology in fluctuating environments such as regulated rivers.
Exploring practices of science coordinators participating in targeted professional development
Authors: Whitworth Brooke A. , Maeng Jennifer L. , Bell Randy L. 
Published: February 2018

AbstractThis study describes how district science coordinators supported teachers and implemented professional development in their districts following participation in the Science Coordinator Academy. This qualitative descriptive case study comprised three district science coordinators from three districts in a mid‐Atlantic state, as well as principals and teachers from those districts. Data sources, including observations, surveys, artifacts, and interviews, were analyzed using the framework method (Gale, Heath, Cameron, Rashid, & Redwood, 2013). District context, science coordinator background, and collaboration were salient factors that influenced coordinator practices and coordinators’ abilities to impact teacher change. We hypothesize that the development of a coaching relationship, facilitating collaboration among teachers, utilizing the characteristics of effective professional development, and promoting reflection through modeling and feedback may be the most important reflection‐growth model of instructional leadership (Blase & Blase, 1999) practices for science coordinators to enact when working with teachers.
Recent Advances in Black‐Phosphorus‐Based Photonics and Optoelectronics Devices
Authors: Debnath Pulak Chandra , Park Kichul , Song Yong‐Won 
Published: February 2018

AbstractIn the recent past, 2D black phosphorus (BP) has been intensively studied and examined due to its unique electronic, photonic, and mechanical properties. The tunable and moderate direct bandgap and the high carrier mobility of BP provide enormous potential in electronic and optoelectronic applications. In addition, the unique intrinsic anisotropic characteristics resulting from the puckered structure yield remarkable optical, electronic, transport, mechanical, and thermal characteristics that can be utilized for designing new devices. Significant efforts have been directed toward the synthesis, basic understanding, and applications of BP in the fields of nanoelectronics, ultrafast optics, nanophotonics, and optoelectronics. Here, the current development of electronic, photonic, optoelectronic, and optical devices based on BP is summarized, along with the recent advances in investigating its electronic, optical, and mechanical properties, which form the foundation for next‐generation chip‐scale integrated devices. In addition, a comprehensive discussion on the requirements for forthcoming studies to upgrade well‐systemized fabrication techniques toward large‐area, high‐yield, and perfectly shielded BP‐film production for the development of reliable devices in optoelectronic applications and other areas is provided. Finally, some existing challenges in implementing BP‐based optoelectronic and photonic devices are addressed and the prospects for future BP‐related research are discussed.
Transmembrane domain dependent inhibitory function of FcγRIIB
Authors: Wang Junyi , Li Zongyu , Xu Liling , Yang Hengwen , Liu Wanli 
Published: March 2018

AbstractFcγRIIB, the only inhibitory IgG Fc receptor, functions to suppress the hyper-activation of immune cells. Numerous studies have illustrated its inhibitory function through the ITIM motif in the cytoplasmic tail of FcγRIIB. However, later studies revealed that in addition to the ITIM, the transmembrane (TM) domain of FcγRIIB is also indispensable for its inhibitory function. Indeed, recent epidemiological studies revealed that a non-synonymous single nucleotide polymorphism (rs1050501) within the TM domain of FcγRIIB, responsible for the I232T substitution, is associated with the susceptibility to systemic lupus erythematosus (SLE). In this review, we will summarize these epidemiological and functional studies of FcγRIIB-I232T in the past few years, and will further discuss the mechanisms accounting for the functional loss of FcγRIIB-I232T. Our review will help the reader gain a deeper understanding of the importance of the TM domain in mediating the inhibitory function of FcγRIIB and may provide insights to a new therapeutic target for the associated diseases.
The Influence of Treatment Timing and Shrub Size on Chinese Privet (Ligustrum sinense) Control with Cut Stump Herbicide Treatments in the Southeastern United States
Authors: Enloe Stephen F. , O’Sullivan Sarah E. , Loewenstein Nancy J. , Brantley Eve , Lauer Dwight K. 
Published: March 2018

AbstractSince its introduction to the United States in 1852, Chinese privet (Ligustrum sinenseLour.) has spread throughout the Southeast, invading many natural areas. Manual control by cutting or shredding is one of the most common strategies many land managers employ. However, rapid sprouting from the root collar and lateral roots commonly results in poor control. Cutting followed by either glyphosate or triclopyr application to the stumps is generally effective, but the efficacy of these herbicides in relation to treatment timing andL. sinenseroot collar diameter has not been evaluated. The objective of this experiment was to determine the effectiveness of glyphosate and triclopyr cut stump treatments compared with cutting alone at spring and fall timings across a range ofL. sinensesize classes. Studies were conducted at two locations in Auburn, AL. Treatments included cut stump+no herbicide, cut stump+ glyphosate (120 g L−1), or cut stump+triclopyr (90 g L−1). Treatments were applied to at least 50 experimental units each at April and November timings. Root collar diameter was recorded for each stem, stems were cut 2.5 cm above the ground, and herbicide treatments were applied within 30 s.Ligustrum sinensemortality and sprouting were quantified 6, 12, and 18 mo after treatment. Both glyphosate and triclopyr amine were very effective in controllingL. sinenseat both spring and fall timings. However, glyphosate provided slightly better results than triclopyr when lateral sprouting was included. Application timing also was significant, with a lower percentage of sprouting following November treatments than April treatments. Stem size influenced treatment success, as larger stumps tended to sprout more than smaller stumps. These results indicateL. sinensecan be controlled with cut stump herbicide treatment using either glyphosate or triclopyr with spring or fall timings at concentrations much lower than typically used.
Unsteady Stokes flow near boundaries: the point-particle approximation and the method of reflections
Authors: Simha A. , Mo J. , Morrison P. J. 
Published: March 2018

Problems of particle dynamics involving unsteady Stokes flows in confined geometries are typically harder to solve than their steady counterparts. Approximation techniques are often the only resort. Felderhof (see e.g. J. Phys. Chem. B, vol. 109 (45), 2005, pp. 21406–21412; J. Fluid Mech., vol. 637, 2009, pp. 285–303) has developed a point-particle approximation framework to solve such problems, especially in the context of Brownian motion. Despite excellent agreement with past experiments, this framework produces unsteady drag coefficients that depend on particle density. This is inconsistent, since the problem can be formulated mathematically without any reference to the particle’s density. We address this inconsistency in our work. Upon implementing our modifications, the framework passes consistency checks that it previously failed. Further, it is not obvious that such an approximation should work for short-time-scale motion. We investigate its validity by deriving it from a general formalism based on integral equations through a series of systematic approximations. We also compare results from the point-particle framework against a calculation performed using the method of reflections, for the specific case of a sphere near a full-slip plane boundary. We find from our analysis that the reasons for the success of the point-particle approximation are subtle and have to do with the nature of the unsteady Oseen tensor. Finally, we provide numerical predictions for Brownian motion near a full-slip and a no-slip plane wall based on the point-particle approximation as used by Felderhof, our modified point-particle approximation and the method of reflections. We show that our modifications to Felderhof’s framework would become significant for systems of metallic nanoparticles in liquids.
DISTRIBUTION OF ACCUMULATION POINTS OF ROOTS FOR TYPE (n - 1, 1) COXETER GROUPS
Authors: HIGASHITANI AKIHIRO , MINEYAMA RYOSUKE , NAKASHIMA NORIHIRO 
Published: March 2018

In this paper, we investigate the set of accumulation points of normalized roots of infinite Coxeter groups for certain class of their action. Concretely, we prove the conjecture proposed in [6, Section 3.2] in the case where the equipped Coxeter matrices are of type
$(n-1,1)$
, where
$n$
is the rank. Moreover, we obtain that the set of such accumulation points coincides with the closure of the orbit of one point of normalized limit roots. In addition, in order to prove our main results, we also investigate some properties on fixed points of the action.
Disease-associated missense mutations in GluN2B subunit alter NMDA receptor ligand binding and ion channel properties
Authors: Fedele Laura , Newcombe Joseph , Topf Maya , Gibb Alasdair , Harvey Robert J. , Smart Trevor G. 
Published: February 2018

AbstractGenetic and bioinformatic analyses have identified missense mutations in GRIN2B encoding the NMDA receptor GluN2B subunit in autism, intellectual disability, Lennox Gastaut and West Syndromes. Here, we investigated several such mutations using a near-complete, hybrid 3D model of the human NMDAR and studied their consequences with kinetic modelling and electrophysiology. The mutants revealed reductions in glutamate potency; increased receptor desensitisation; and ablation of voltage-dependent Mg2+ block. In addition, we provide new views on Mg2+ and NMDA channel blocker binding sites. We demonstrate that these mutants have significant impact on excitatory transmission in developing neurons, revealing profound changes that could underlie their associated neurological disorders. Of note, the NMDAR channel mutant GluN2BV618G unusually allowed Mg2+ permeation, whereas nearby N615I reduced Ca2+ permeability. By identifying the binding site for an NMDAR antagonist that is used in the clinic to rescue gain-of-function phenotypes, we show that drug binding may be modified by some GluN2B disease-causing mutations.
The viscosity of atmospherically relevant organic particles
Authors: Reid Jonathan P. , Bertram Allan K. , Topping David O. , Laskin Alexander , Martin Scot T. , Petters Markus D. , Pope Francis D. , Rovelli Grazia 
Published: February 2018

AbstractThe importance of organic aerosol particles in the environment has been long established, influencing cloud formation and lifetime, absorbing and scattering sunlight, affecting atmospheric composition and impacting on human health. Conventionally, ambient organic particles were considered to exist as liquids. Recent observations in field measurements and studies in the laboratory suggest that they may instead exist as highly viscous semi-solids or amorphous glassy solids under certain conditions, with important implications for atmospheric chemistry, climate and air quality. This review explores our understanding of aerosol particle phase, particularly as identified by measurements of the viscosity of organic particles, and the atmospheric implications of phase state.
Toward a universal decoder of linguistic meaning from brain activation
Authors: Pereira Francisco , Lou Bin , Pritchett Brianna , Ritter Samuel , Gershman Samuel J. , Kanwisher Nancy , Botvinick Matthew , Fedorenko Evelina 
Published: February 2018

AbstractPrior work decoding linguistic meaning from imaging data has been largely limited to concrete nouns, using similar stimuli for training and testing, from a relatively small number of semantic categories. Here we present a new approach for building a brain decoding system in which words and sentences are represented as vectors in a semantic space constructed from massive text corpora. By efficiently sampling this space to select training stimuli shown to subjects, we maximize the ability to generalize to new meanings from limited imaging data. To validate this approach, we train the system on imaging data of individual concepts, and show it can decode semantic vector representations from imaging data of sentences about a wide variety of both concrete and abstract topics from two separate datasets. These decoded representations are sufficiently detailed to distinguish even semantically similar sentences, and to capture the similarity structure of meaning relationships between sentences.
Inverted valley polarization in optically excited transition metal dichalcogenides
Authors: Berghäuser Gunnar , Bernal-Villamil Ivan , Schmidt Robert , Schneider Robert , Niehues Iris , Erhart Paul , Michaelis de Vasconcellos Steffen , Bratschitsch Rudolf , Knorr Andreas , Malic Ermin 
Published: February 2018

AbstractLarge spin–orbit coupling in combination with circular dichroism allows access to spin-polarized and valley-polarized states in a controlled way in transition metal dichalcogenides. The promising application in spin-valleytronics devices requires a thorough understanding of intervalley coupling mechanisms, which determine the lifetime of spin and valley polarizations. Here we present a joint theory–experiment study shedding light on the Dexter-like intervalley coupling. We reveal that this mechanism couples A and B excitonic states in different valleys, giving rise to an efficient intervalley transfer of coherent exciton populations. We demonstrate that the valley polarization vanishes and is even inverted for A excitons, when the B exciton is resonantly excited and vice versa. Our theoretical findings are supported by energy-resolved and valley-resolved pump-probe experiments and also provide an explanation for the recently measured up-conversion in photoluminescence. The gained insights might help to develop strategies to overcome the intrinsic limit for spin and valley polarizations.
Saccade-synchronized rapid attention shifts in macaque visual cortical area MT
Authors: Yao Tao , Treue Stefan , Krishna B. Suresh 
Published: February 2018

AbstractWhile making saccadic eye-movements to scan a visual scene, humans and monkeys are able to keep track of relevant visual stimuli by maintaining spatial attention on them. This ability requires a shift of attentional modulation from the neuronal population representing the relevant stimulus pre-saccadically to the one representing it post-saccadically. For optimal performance, this trans-saccadic attention shift should be rapid and saccade-synchronized. Whether this is so is not known. We trained two rhesus monkeys to make saccades while maintaining covert attention at a fixed spatial location. We show that the trans-saccadic attention shift in cortical visual medial temporal (MT) area is well synchronized to saccades. Attentional modulation crosses over from the pre-saccadic to the post-saccadic neuronal representation by about 50 ms after a saccade. Taking response latency into account, the trans-saccadic attention shift is well timed to maintain spatial attention on relevant stimuli, so that they can be optimally tracked and processed across saccades.
Context-dependent interactions and the regulation of species richness in freshwater fish
Authors: MacDougall Andrew S. , Harvey Eric , McCune Jenny L. , Nilsson Karin A. , Bennett Joseph , Firn Jennifer , Bartley Timothy , Grace James B. , Kelly Jocelyn , Tunney Tyler D. , McMeans Bailey , Matsuzaki Shin-Ichiro S. , Kadoya Taku , Esch Ellen , Cazelles Kevin , Lester Nigel , McCann Kevin S. 
Published: February 2018

AbstractSpecies richness is regulated by a complex network of scale-dependent processes. This complexity can obscure the influence of limiting species interactions, making it difficult to determine if abiotic or biotic drivers are more predominant regulators of richness. Using integrative modeling of freshwater fish richness from 721 lakes along an 11o latitudinal gradient, we find negative interactions to be a relatively minor independent predictor of species richness in lakes despite the widespread presence of predators. Instead, interaction effects, when detectable among major functional groups and 231 species pairs, were strong, often positive, but contextually dependent on environment. These results are consistent with the idea that negative interactions internally structure lake communities but do not consistently ‘scale-up’ to regulate richness independently of the environment. The importance of environment for interaction outcomes and its role in the regulation of species richness highlights the potential sensitivity of fish communities to the environmental changes affecting lakes globally.
Stirring does not make populations well mixed
Authors: Herrerías-Azcué Francisco , Pérez-Muñuzuri Vicente , Galla Tobias 
Published: February 2018

AbstractIn evolutionary dynamics, the notion of a ‘well-mixed’ population is usually associated with all-to-all interactions at all times. This assumption simplifies the mathematics of evolutionary processes, and makes analytical solutions possible. At the same time the term ‘well-mixed’ suggests that this situation can be achieved by physically stirring the population. Using simulations of populations in chaotic flows, we show that in most cases this is not true: conventional well-mixed theories do not predict fixation probabilities correctly, regardless of how fast or thorough the stirring is. We propose a new analytical description in the fast-flow limit. This approach is valid for processes with global and local selection, and accurately predicts the suppression of selection as competition becomes more local. It provides a modelling tool for biological or social systems with individuals in motion.