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Utilizing reflectance spectroscopy to generate the necessary soil data to drive innovations in precision agriculture and soil management is an increasing focus of agronomic research. One of the key limitations for widespread practical adoption of reflectance spectroscopy is hardware cost, and lower cost hardware is actively being developed. This study evaluated two inexpensive nano Fourier‐transform near infrared spectrometers in the laboratory. One was a laboratory‐based analyzer (LabFlow) and the second was a field portable analyzer (Field Probe). Soil spectra were collected in the shortwave infrared range and processed using wavelet transforms and machine learning models. The optimal wavelet transforms and machine learning model were selected using cross validation on the training dataset, and performance of the optimal model was evaluated using an independent testing dataset. The Field Probe configuration total nitrogen model had the best performance when compared to the LabFlow laboratory analyzer with an R2of 0.91, a concordance correlation coefficient of 0.95, and an root mean square error of 0.03. Soil inorganic carbon did not perform as well with an R2of 0.65. However, performance was likely limited by a large number of low values and a limited range in the training dataset. Overall, these results highlight the potential for lower cost spectrometers to provide useful soil data for soil management applications. There is a potential for low‐cost spectrometers to provide useful soil data for soil management applications.Optimal signal processing, model type, and model hyperparameters are dataset specific.Error in reference values is important to consider regarding model performance.

This article focuses on the thermal management and temperature balancing of lithium-ion battery packs. As society transitions to relying more heavily on renewable energy, the need for energy storage rises considerably, as storage facilitates power regulation between these sources and the grid. Lithium-ion batteries are leading the market for energy storage options, but their properties are temperature sensitive, with thermal abuse resulting in shortened pack lifetime and possible safety issues. Current battery thermal management systems (BTMS) are implemented in a number of ways to ensure consistent and reliable operation. However, they are typically limited in architecture and restricted in ability to attend to temperature gradients. This work proposes a BTMS topology that permits control of the individual cooling received by a cell in a pack. First, an analysis is done using timescale separation to confirm that cell-level temperature control is capable of extending the lifetime of a pack as compared to pack-level control. The analysis is used to guide the gain tuning of a state feedback controller, which directs more cooling effort to cells of higher temperatures. Validation of the BTMS topology and control is performed through the simulation of a battery pack, with variations in total cooling power and resistance heterogeneity. The outcome of the validation studies indicates that the proposed BTMS configuration is better equipped to reduce temperature differences and extend pack life. This benefit increases as total input power increases, giving the controller more freedom to cool unhealthy cells while remaining within power constraints.

This paper studies the impact of battery pack parameter heterogeneity on active balancing methods. Lithium-ion battery packs are often composed of multiple individual cells connected in series and parallel to meet energy storage requirements for a given application. Due to manufacturing tolerances and environmental conditions, variations in each cell's parameters are induced, which can propagate charge and other state imbalances. This is detrimental to pack operation, as cell-to-cell variations can limit total capacity and increase degradation. While studies in the literature propose balancing methods to equalize all charge levels, there are limited studies that explore analytical relationships between parameter and state heterogeneity. This paper provides a framework to model state and parameter heterogeneity simultaneously, supporting an enhanced understanding of cell mismatch effects during pack operation and balancing. The developed heterogeneity model facilitates derivation of analytical expressions relating to system stability in the presence of cell mismatch and state heterogeneity generated by parameter heterogeneity. These expressions are validated through simulation case studies of a pack represented by interconnected equivalent circuit cell models with capacity heterogeneity. For both no balancing and state of charge (SOC) balancing, results indicate that capacity heterogeneity propagates SOC imbalance while the pack is operating with a nonzero average current. Using the heterogeneity modeling framework, a modified SOC balancing strategy is proposed to equalize cells with capacity differences.

Objective: To determine the relative frequency of abnormal cerebrospinal fluid (CSF) findings in children with Lyme disease-associated facial nerve palsy. Design: A clinical series. A prospective evaluation was undertaken of the condition of children seen between 1988 and 1996 at a single medical center in a Lyme disease endemic area. Patients: Forty children (24 boys and 16 girls, aged 3-19 years) with new onset facial nerve palsy who met the Centers for Disease Control and Prevention case definition of Lyme disease. Interventions: Neurologic examinations. Cerebrospinal fluid analyses. Main Outcome Measures: Rates of abnormal CSF findings: white blood cell count, protein level, and Borrelia burgdorferi-specific CSF assays. Results: Cerebrospinal fluid white blood cell count, protein level, or both were abnormal in 27 (68%) of the children. Thirty-six (90%) of the 40 children had a CSF abnormality consistent with central nervous system infection or immune involvement by B burgdorferi. Of the 22 children with CSF pleocytosis, only 7 (32%) had headache and none had meningeal signs. Conclusions: Most children with Lyme disease-associated facial nerve palsy have CSF abnormalities. Our studies indicate that, in endemic areas, facial nerve palsy in children may be a marker of Lyme disease and occult meningitis. When Lyme disease is suspected, CSF should be examined; in some cases, it may be helpful to expand beyond routine CSF studies to look at a battery of B burgdorferi-specific assays. Arch Pediatr Adolesc Med. 1997; 151:1224-1228, Facial nerve palsy in children may indicate Lyme disease in areas where the infection is endemic. Lyme disease is spread by ticks and can produce pain, flu-like, and neurologic symptoms. Doctors treated 40 children with facial paralysis and Lyme disease in an endemic region in New York State. Almost 70% of the children had elevated white cell or protein levels in their cerebrospinal fluid (CSF), and 90% of children had these or other abnormalities indicative of central nervous system activity by the Lyme organism. In endemic areas, CSF analysis may be superior to blood tests for Lyme disease.

Introduction Whole body concentrations of caesium-137 are closely related to dietary intake of the isotope, [1] which has a physical half life of 30 years but a biological half life [...]

Density functional theory (DFT) calculations on large clusters of indium phosphide are presented. Several quantum dot-sized models, (NH3)64(InP)117, (COOH2)45(InP)117, (InCl3)29(InP)147, and (ZnCl2)29(InP)147, were passivated with organic or inorganic ligands; in some systems, both types were used. Initial results with the PBE1PBE functional proved puzzling as many clusters were initially found to have open-shell paramagnetic ground states, which is not sensible for nanoparticles of a direct band-gap semiconductor. In the case of QDs passivated with organic ligands, implementation of a robust geometry optimization procedure demonstrated that these findings were due to localization to metastable states and that the ground states are in fact diamagnetic singlets. However, the “nonstoichiometric” inorganic-passivated clusters (InCl3)29(InP)147and (ZnCl2)29(InP)147have ground nonet and septet states, respectively. Examination of the molecular orbitals revealed non-Aufbau state filling, suggesting the potential for open-shell singlet ground states, which is supported by calculations at the more robust M06-2x level of theory. Experimental evidence for paramagnetic or open-shell singlet ground states was not realized, which may be due to a mixture of inorganic and organic passivations.

The synthesis of nanomaterials with a narrow size distribution is challenging, especially for III–V semiconductor nanoparticles (also known as quantum dots). Concerning phosphides, this issue has been largely attributed the use of overly reactive precursors. The problem is exacerbated due to the narrow range of competent reagents for III–V semiconductor syntheses. We report the use of sterically encumbered tris(triethylsilyl) phosphine and tris(tributylsilyl) phosphine for InP quantum dot (QD) synthesis among others. The hypothesis was that these reagents are less reactive than the near-ubiquitous precursor tris(trimethylsilyl) phosphine and can be used to create more homogeneous materials. It was found that the InP products’ quantum yields and emission color saturation (fwhm) were improved, but not to the levels realized in CdSe QDs. Regardless, these reagents have other positive attributes; they are less pyrophoric and can be applied toward the synthesis of II–V semiconductors and organophosphorus compounds. Concerning safe practices, we demonstrate that ammonium bifluoride is an effective replacement for highly toxic HF for the post-treatment of III–V semiconductor quantum dots.

Fungus-growing ants and their microbial symbionts have emerged as a model system for understanding antibiotic deployment in an ecological context. Here we establish that bacterial symbionts of the ant Trachymyrmex septentrionalisantagonize their most likely competitors, other strains of ant-associated bacteria, using the thiopeptide antibiotic GE37468. Genomic analysis suggests that these symbionts acquired the GE37468 gene cluster from soil bacteria. This antibiotic, with known activity against human pathogens, was previously identified in a biochemical screen but had no known ecological role. GE37468’s host-associated defense role in this insect niche intriguingly parallels the function of similar thiopeptides in the human microbiome.

Bioprospecting could offer many advantages to the National Park System if benefits sharing is addressed. IN 1997, YELLOWSTONE National Park entered into the first negotiated agreement guaranteeing that some of [...]

Semiconductor quantum dots (QDs), also known as nanocrystals, have unique photophysical properties that have allowed them to find utility in many applications, including television and display technologies. They also have significant potential as imaging agents in the biomedical field. To gain the most value from the use of QDs as health-related fluorescent probes, they must be biologically targetable and sensitive to metabolic analytes such as pH and O2, and the resulting signal must be quantifiable. To achieve these goals, QDs need to be conjugated to vectors such as antibodies or environmentally sensitive chromophores. Until recently, the functionalization of these nanomaterials required a complex fully “bottom-up” approach beginning with the synthesis of the QDs and subsequent manipulations. To simplify this process, our group set out to develop straightforward methods to prepare functionalized nanomaterials for biological imaging and sensing using low-cost, commercially available aqueous QD dispersions.

Hybridization is common in fishes and can result in a wide range of outcomes. The capture of a world record phenotypic Guadalupe Bass Micropterus treculiiraised questions about potential hybridization with Spotted Bass M. punctulatus. Subsequent, limited genetic sampling from the drainage (Colorado River) did not indicate hybridization in the world record sample or other phenotypic Guadalupe Bass, but phenotypic Spotted Bass produced unexpected genotypes. This called into question the assumed distribution of Spotted Bass in Texas. To address this disconnect, phenotypic Spotted Bass were acquired from drainages surrounding the Colorado River, ranging from central Texas to the Texas–Louisiana border, and the number of sequenced loci was expanded from one to seven. Results indicated that the westernmost extent of nonintrogressed Spotted Bass populations in Texas was the Trinity River. Phenotypic Spotted Bass west of this drainage were identified as Guadalupe Bass or hybrids. Admixed individuals identified in the San Antonio and Brazos River drainages (and previously in the Colorado River) may represent part of a hybrid zone. We also found that Spotted Bass from the Trinity River exhibited relatively large genetic divergence from Spotted Bass to the east and may represent the product of a vicariance event. Finally, we confirmed one mitochondrial and two nuclear taxa‐specific genetic markers for the efficient discrimination of these congeners and their hybrids. These markers should be useful for resource agencies attempting to enforce management regulations given the difficulty of identifying Spotted Bass by phenotype.

Abstract:Close attention to the original meaning of the words κατακαλύπτω (1 Cor 11:6) and κατὰ κεφαλῆς ἔχων (1 Cor 11:4) permits a translation only of a material head covering. These words do not describe the process of letting hair hang down loosely. These words are consistently used in Classical and Hellenistic Greek to describe the action of covering the head with a textile covering of some kind. In spite of sustained efforts by advocates, the long-hair theory still has not succeeded in gaining an entry into standard reference works. The original edition of BAGD in 1957, the revised edition in 1979, and the more recent edition of BDAG in 2000 all support the view that the text of 1 Cor 11:2–16 describes an artificial textile head covering of some kind.

The recent development of time-resolved X-ray absorption spectroscopy (TR-XAS) has opened avenues for fundamental research on doped semiconductors. Reported herein are results on the successful doping of indium phosphide nanocrystals (NCs) with copper and subsequent characterization with time-resolved X-ray studies and large-scale density functional theory (DFT) calculations. The synthetic protocol that was based on the cluster seed method afforded control of both the doping level and the quantity of NCs produced in a batch. The stability of the colloidal dispersion allowed us to monitor the photophysical properties of copper guest ions with static and TR-XAS at the copper K-edge. These data reveal that copper captures a hole from the photoexcited InP NC, and relaxation to the ground state occurs via multiple timescales likely due to the presence of interior and surface-bound dopant ions as well as recombination with surface- and defect-trapped electrons. Large-scale DFT calculations reveal a striking dependence of the electronic structure on the ligand coating and other effects such as self-compensation.

Understanding the electronic structure of doped semiconductors is essential to realize advancements in electronics and in the rational design of nanoscale devices. Reported here are the results of time-resolved X-ray absorption studies on copper-doped cadmium sulfide nanoparticles that provide an explicit description of the electronic dynamics of the dopants. The interaction of a dopant ion and an excess charge carrier is unambiguously observed viamonitoring the oxidation state. The experimental data combined with DFT calculations demonstrate that dopant bonding to the host matrix is modulated by its interaction with charge carriers. Furthermore, the transient photoluminescence and the kinetics of dopant oxidation reveal the presence of two types of surface-bound ions that create midgap states.

Molecular oxygen is known to be an efficient quencher of the excited states of organic molecules. This fact has been exploited to develop fluorescent O2sensors, which is topical for cancer screening and many other applications. In this regard, our group and others have reported the development of robust, ratiometrically reporting chemosensors by conjugating O2-sensitive organic chromophores to inorganic quantum dots. Recently, an attempt was made to prepare a multifunctional sensor system by attaching the emissive poly(aromatic) hydrocarbons pyrene and perylene to magnetic nanomaterials, specifically CdSe/CdMnZnS and ZnSe/ZnMnS/ZnS quantum dots. However, the fluorescence of both dyes became invariant to oxygen levels even if the solutions were fully saturated. We ruled out any material dependency beyond the presence of Mn2+ions by studying control samples, while molecular dynamics simulations negated any possibility of spatial sequestration of O2by the magnetic fields. In the case of pyrene, the proximity of the magnetic dots induces significant singlet–triplet mixing; however, this does not explain this curious observation. As such, we believe that the exchange interaction between O2and the dyes is perturbed by both the microenvironment of the system and the inhomogeneous magnetic fields such that quenching is not observed.

Regional heterothermy is a pattern whereby different body regions are maintained at different temperatures, often to prioritize the function of certain body parts over others, or to maximize the function of organs and tissues that vary in thermal sensitivity. Regional heterothermy is relatively well understood in endotherms, where physiological mechanisms maintain heterogeneity. However, less is known about regional heterothermy in ectotherms, where behavioral mechanisms are more important for generating thermal variation. In particular, whether small and elongate ectotherms with high surface area to volume ratios such as diminutive snakes can maintain regional heterothermy, despite rapid thermal equilibration, is not yet known. We measured regional variation in body temperature and tested whether environmental heterogeneity is used to generate regional heterothermy in the ring-necked snake (Diadophis punctatus) using both field and laboratory studies. We found that ring-necked snakes have robust regional heterothermy in a variety of contexts, despite their small body size and elongate body shape. Temperature variation along the length of their bodies was not detectable when measured externally. However, snakes had higher mouth than cloacal temperatures both in the field and in laboratory thermal gradients. Further, this regional heterothermy was maintained even in ambient laboratory conditions, where the thermal environment was relatively homogeneous. Our results indicate that regional heterothermy in ring-necked snakes is not solely driven by environmental variation but is instead linked to physiological or morphological mechanisms that maintain regional variation in body temperature irrespective of environmental context.

A systematic effort has been described to grow ternary Ge1–x–ySixSnysemiconductors on silicon with high Sn concentrations spanning the 9.5–21.2% range. The ultimate goal is not only to produce direct band gap materials well into the infrared region of the spectrum but also to approach a critical concentration (yc) for which further additions of Si would decrease─rather than increase─the band gap. This counterintuitive behavior is expected as a result of the giant bowing parameter in the compositional dependence of the band gap associated with the presence of Si–Sn pairs. The growth approach in this study was based on a chemical vacuum deposition method that uses Si4H10, Ge3H8, and SnD4or SnH4as the sources of Si, Ge, and Sn, respectively. A fixed Si concentration near x= 0.05–0.07 was chosen to focus the exploration of the compositional space. A first family of samples was grown of Ge-buffered Si substrates. For Sn concentrations y< 0.12, it was found that the samples relaxed their mismatch strain in situ during growth, resulting in high Sn content films that had relatively low levels of strain and exhibited photoluminescence signals that demonstrated direct band gap behavior for the first time. The device potential of these materials was also demonstrated by fabricating a prototype photodiode with low dark currents. The optical studies suggest that the above-mentioned critical concentration is close to yc= 0.2. As the growth temperature was lowered in an effort to reach such values, Sn concentrations as high as y= 0.15 were obtained, but the films grew fully strained with compressive levels as high as 1.7%. To increase the Sn concentration beyond y= 0.15, a new strategy was adopted, in which the Ge buffer layer was eliminated, and the ternary alloy was grown directly on Si. The much higher lattice mismatch between the Ge1–x–ySixSnylayer and the Si substrate caused strain relaxation right at the film/substrate interface, and the subsequent films grew with much lower levels of strain. This made it possible to lower the growth temperatures even further and achieve a comprehensive series of strained relaxed samples with tunable Sn concentrations as high as y= 0.21 (and beyond). The latter represent the highest Sn contents in crystalline Ge1–x–ySixSnyattained to date and reach the desired yc= 0.2 range. The synthesized films exhibited significant thickness, allowing a thorough determination of composition, crystallinity, morphology, and bonding properties, indicating the formation of single-phase single-crystal alloys with random cubic structures. Further work will focus on optimizing the latter samples to explore the optical and electronic properties.

While traveling north on Interstate 5, six miles north of Dunnigan, Calif., I experienced a loss of steering while driving our 2005 Newmar Kountry Star 35-foot motorhome. Luckily, I was [...]

Background/Objectives:Adequate protein intake is essential to retaining muscle and maintaining physical function, especially in the elderly, and L-Leucine has received attention as an essential amino acid (EAA) that enhances protein retention. The study’s aim was to compare the efficacy of EAA mixtures on lean tissue mass (LTM) and functional performance (FP) in a healthy elderly population.Subjects/Methods:Thirty-six subjects (65–75 years) volunteered to receive capsules with EAAs (Groups A and B containing 20% and 40% L-Leucine, respectively) or placebo (lactose containing 0% L-Leucine, Group C) for 12 weeks. The daily amount ranged from 11 to 21 g (0.21 g/ kg/day) and was taken in two equal dosages alongside food, morning and evening. Main outcomes measured before and after intervention were LTM and FP (30-s arm-curl test; 30-s chair-stand test (30-CST); 6-min walk test (6-WT); and handgrip strength). Secondary outcomes included dietary intakes and physical activity.Results:Twenty-five subjects (11 male and 14 female) completed the study (Group A, n=8; Group B, n=8; Group C, n=9). Gains associated with medium effect sizes were noted in LTM (Group B, 1.1 ±1.1%, P=0.003) and FP (Group A in 30-CST (11.0±11.5%, P=0.02) and 6-WT (8.8±10.0%, P=0.02); Group B in 6-WT (5.8±6.6%, P=0.03) and a trend in 30-CST (13.2±16.0, P=0.06)). Significant differences between groups were not observed in secondary outcomes.Conclusions:Twice-daily supplementation of EAAs containing 20% or 40% L-Leucine improved aspects of functional status and at the higher level improved LTM. Further work to establish change in a larger sample and palatable supplemental format is now required.

The stocking of fishes outside of their native range for the purpose of sport fisheries can lead to secondary contact and introgression between species that were historically allopatrically distributed. Smallmouth Bass Micropterus dolomieuwere introduced within the range of Guadalupe Bass M. treculiiin central Texas and introgressive hybridization subsequently occurred. One recent survey of temporal changes in introgression in the Blanco River found that introgression had increased and that Guadalupe Bass had been extirpated. Thus, a survey of changes in introgression across the range of the Guadalupe Bass was conducted in 12 subbasins in the Brazos, Colorado, Guadalupe–San Antonio, and Nueces drainages in Texas using 15 microsatellite loci. The results indicate that introgression is now occurring in four subbasins but no longer occurring in the Lampasas and San Gabriel rivers, where rates were previously 6% and 46%, respectively. Additionally, we found no evidence that stocking of hatchery-reared individuals in the Guadalupe and Nueces rivers has led to severely depressed genetic variation. The variable success of restoration efforts to prevent extirpation of the Guadalupe Bass suggests that protection of the remaining nonintrogressed populations should be a priority for the conservation of this species.

We report here a method for synthesizing CdSe quantum dots (QDs) containing copper such that each QD is doped with four copper ions. The synthesis is a derivative of the cluster-seed method, whereby organometallic clusters act as nucleation centers for quantum dots. The method is tolerant of the chemical identity of the seed; as such, we have doped four copper ions into CdSe QDs using [Na(H2O)3]2[Cu4(SPh)6] as a cluster seed. The controlled doping allows us to monitor the photophysical properties of guest ions with X-ray spectroscopy, specifically XANES and EXAFS at the copper K-edge. These data reveal that copper can capture both electrons and holes from photoexcited CdSe QDs. When the dopant is oxidized, photoluminescence is quenched and the copper ions translocate within the CdSe matrix, which slows the return to an emissive state.

Semiconductor nanocrystals (NCs or quantum dots) have significant potential for use in a variety of applications from renewable energy generation to biological imaging. Modern methods of colloidal synthesis can be used to create crystalline materials with tight size distributions; this assures high quantum yields and narrow emission profiles in the case of direct-bandgap semiconductors. The optical properties of NCs may also be tuned with size due to quantum confinement effects. Quantum confinement also creates problems when characterizing nanomaterials; specifically, the absorptivity of a sample is a function of the size and structure of the quantum dots. We demonstrate here a simple method for determining the molar absorptivity of aqueous CdSe/CdZnS NCs through Förster resonant energy transfer. Energy transfer from NC donors to dye acceptors was measured and modeled using standard Förster theory incorporating Poissonian statistics to calculate the acceptor/donor ratio leading to a direct determination of the NC concentration. This process is significantly more simple than standard methods for calculating the size-dependent Beer’s law coefficient of nanomaterials and can be applied to heterogeneous quantum confined systems. The results also yield surprising insight into the internal structure of water-soluble polymer-coated core/shell quantum dots.

Developing simple synthetic methods to control the size and morphology of nanocrystals is an active area of research as these parameters control the material’s electronic and optical properties. For a semiconductor with a symmetrical crystal structure such as lead selenide, anisotropic colloidal growth has been previously accomplished viathe use of templates, seeds, or by block assembly of smaller, symmetrical subunits. Here, we present a simple method to create monodisperse lead selenide nanorods and multipods at low temperatures. The size distribution and the observed morphologies are consistent with a continuous, anisotropic growth of material. The syntheses of these anisotropic shapes are due to the nature of the nuclei that form upon injection of precursors into partially oxidized alkene solvents that may contain lactone and carbonate-functional derivatives.

Oleic acid capped lead sulfide (PbSe) cubes, spheres, rods and star-shaped nanocrystals with sizes ranging from 5 to 20 nm were synthesized, then subjected to a post-synthesis washing in a 1:1 ethanol/hexane solution. The relationship of third order nonlinear optical properties to nanocrystal surface chemistry as affected by this washing was analyzed using nanosecond 532 nm Z-scan. The results indicated a significant change in optical properties emerged only after the nanocrystals, regardless of shape, were washed in the ethanol/hexane mixture. The "as grown" nanocrystals displayed high emission efficiency with no nonlinear absorption, which converted to a highly-absorbing and strongly scattering media with quenching of optical emission following washing. Transmission electron microscopy showed that neither the size nor shape of the nanocrystals was changed by washing, indicating that all differences were related to changes in surface chemistry. Finally, the Z-scan of washed nanocrystals displayed a strong correlation between nonlinear scattering and nonlinear transmittance which was also not dependent upon shape. It is postulated that the washing allowed formation of deep trap states that permitted nonlinear optical absorption.

We have developed colloidal synthesis methods to create nanoparticles (NPs) of tantalum nitride. The particle sizes and crystallinity can be controlled through the use of different organic solvents and reaction times; we demonstrate here NPs ranging in size from 2 to 23 nm. While electron microscopy and selected area diffraction demonstrate the synthesis of NPs of tantalum nitride (which may be partially oxidized), results from X-ray photoelectron spectroscopy reveal that the majority of the tantalum in our sample is present as an unidentified molecular-scale oxide species.

We report a novel method for cap exchange of emissive semidondutor nanocrystals (NCs) using thiol functional ligands metalated with zinc. Utilizing this method, the NCs can be several times brighter and much more resistant to precipitation compared to control samples. This method has been applied using a variety of caps such as dihydrolipoic acid and cysteine. Our data suggest that the improved properties of the metalated cap exchanged NCs are due to a ligand metathesis process occurring at the NC surface where the zinc complex reacts with NC surface bound ligands, gently removing them and replacing them with another cap. Overall, the use of metalated ligands helps resolve many long-standing issues concerning the application of small cap exchanged NCs for biological imaging.

Emissive semiconductor nanocrystals can be efficient FRET donors to chemically responsive organic fluorophores; conjugating the two creates a ratiometric (or self-calibrating) sensor. Given that the organic component engenders chemical and/or biological sensitivity, it is natural to assume that the NC−dye response is reflective of the photochemical properties of the neat dye. In the case of a pH sensor like fluorescein, the dye emission can be analytically described by the Henderson−Hasselbalch equation. Our research demonstrates that the ratiometric sensing response of CdS/ZnS−fluorescein pH sensors, however, does not directly reflect the Henderson−Hasselbalch relationship and is difficult to predict. The reasons for this complexity are the alternations of the dye microenvironment within the nanoscale architecture and the nature of energy transfer from the NC donor to the acceptor dye.

Oleic acid capped lead sulfide (PbS) and lead selenide (PbSe) were synthesized, then subjected to a postsynthesis washing in a 1:1 ethanol/hexane solution. The relationship of third order nonlinear optical properties to nanocrystal surface chemistry as affected by washing was analyzed using nanosecond 532 nm Z-scan and measurement of near-IR radiative emission. The results indicated a significant change in optical nonlinearities which emerged only after the nanocrystals were washed in the ethanol/hexane mixture. Transmission electron microscopy of the oleic acid capped PbSe and PbS nanocrystals showed a cubic shape, narrow size distribution and an average size of ∼10 nm. Neither size nor shape of the nanocrystals were modified by the washing process, indicating that all optical differences were related to changes in surface chemistry and the formation of deep trap states. The “as grown” nanocrystals showed high emission efficiency, weak saturable absorption, and a self-defocusing refractive index, n2, determined to be −(3.0 ± 0.9) × 10−14and −(2.9 ± 0.6) × 10−14cm2/W for PbS and PbSe nanocrystals, respectively. After post-synthesis washing, the nanocrystals were converted to a reverse saturable absorbing and strongly scattering media with a self-focusing refractive index of (11.4 ± 2.0) × 10−14and (12.7 ± 0.9) × 10−14cm2/W for PbS and PbSe nanocrystals, respectively. The fitted experimental Z-scan data for the samples after washing gave high values for the nonlinear absorption coefficient, βeff, in the range of 130−150 cm/GW. The appearance of reverse saturable absorption in the nanocrystals was due to the presence of trap states at the nanocrystal surface that were not present in the as-grown nanocrystals and did not show similar optical nonlinearity.

The Guadalupe bass Micropterus treculiiis endemic to Texas and is threatened by introgression with introduced smallmouth bass M. dolomieuas well as habitat degradation. This study described and quantified the movements and habitat associations of Guadalupe bass to assess the factors that may influence current populations. Radio-tagged adult Guadalupe bass were tracked in the Pedernales River (n= 12) and South Llano River (n= 12) from January through August 2008. Available microhabitats were measured and modeled in terms of depth, velocity, substrate, and cover for about 1.5 km in the Pedernales River and 1.2 km in the South Llano River. Rates of movement were greatest during the reproductive season, ranging from less than 1 to 9 m/d. Instream cover (such as undercut banks and woody debris) was preferred during daylight hours throughout the study period, although the distances from cover increased from January to August. Habitat shifts from cover to open water occurred at night and from woody structures to boulders and ledges during a large flood pulse. The habitats most suitable for adult Guadalupe bass had a depth of 1.0 m and a current velocity of 0.05 m/s, and habitat selection was strongest for eddy mesohabitats with smaller substrates. By July, the Guadalupe bass in the South Llano River were associated with runs with greater current velocities, whereas those in the Pedernales River were associated with pools with greater depths, largely owing to the low flows and reduced habitat availability in the Pedernales River. Environmental factors, including the availability and suitability of instream cover, are probably the strongest influences on the distribution and abundance of Guadalupe bass.

Many types of metal and semiconductor nanoparticles (NPs) are created viacolloidal synthetic methods, which renders the materials hydrophobic. Such NPs are dispersed in water through surface organic cap exchange or by amphiphilic polymer encapsulation; often, water solubility is achieved viathe presence of carboxylic acid functionalities on the solubilizing agents. While this renders the material water-soluble, subsequent functionalization of the systems can be very difficult. The most obvious method to derivatize carboxylic acid coated NPs is to conjugate chemical and biological moieties containing amine functionality to the NP surface using the water-soluble activator 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). However, the excess use of this reagent appears to cause complete and permanent precipitation of the NPs. We report here our method on the chemical and biological functionalization of a variety of semiconductor nanoparticle systems using novel carbodiimide reagents. These reagents do not cause precipitation even at high loading levels and can be used to efficiently functionalize carboxylic acid coated NPs.

Materials for studying biological interactions and for alternative energy applications are continuously under development. Semiconductor quantum dots are a major part of this landscape due to their tunable optoelectronic properties. Size-dependent quantum confinement effects have been utilized to create materials with tunable bandgaps and Auger recombination rates. Other mechanisms of electronic structural control are under investigation as not all of a material’s characteristics are affected by quantum confinement. Demonstrated here is a new structure–property concept that imparts the ability to spatially localize electrons or holes within a core/shell heterostructure by tuning the charge carrier’s kinetic energy on a parabolic potential energy surface. This charge carrier separation results in extended radiative lifetimes and in continuous emission at the single-nanoparticle level. These properties enable new applications for optics, facilitate novel approaches such as time-gated single-particle imaging, and create inroads for the development of other new advanced materials.

Dendritic cells (DCs) can infiltrate tight junctions of the epithelium to collect remote antigens during immune surveillance. While elongated membrane structures represent a plausible structure to perform this task, their functional mechanisms remain elusive owing to the lack of high-resolution characterizations in live DCs. Here, we developed fluorescent artificial antigens (FAAs) based on quantum dots coated with polyacrylic acid. Single-particle tracking of FAAs enables us to superresolve the membrane fiber network responsible for the antigen uptake. Using the DC2.4 cell line as a model system, we discovered the extensive membrane network approaching 200 μm in length with tunnel-like cavities about 150 nm in width. The membrane fiber network also contained heterogeneous circular migrasomes. Disconnecting the membrane network from the cell body decreased the intracellular FAA density. Our study enables mechanistic investigations of DC membrane networks and nanocarriers that target this mechanism.

To examine cognitive functioning in children with multiple sclerosis (MS).

As the function of optically-based chemobiosensors CBsensors evolves towards micro- and nanoscale dimensions, the sensitivity of the device is compromised because there are simply too few reporting active sites. We see this issue as the fundamental challenge confronting the design of small length scale CBsensors, providing an imperative for the development of new optical transduction strategies. To address this challenge, we are currently fabricating: i new materials that will amplify the primary optical signal from the CBsensing active site in micro- and nano-environments and ii new sensing elements and devices to achieve high gain from a non-linear optical response. We present here the synthesis and characterization of two platforms poised for sensing by non-linear transduction.

The 13C‐octanoic acid breath test (OABT) may be a useful non‐invasive method for assessing the rate of gastric emptying in dogs. The aim of this study was to determine whether an association exists between body size and rate of gastric emptying in dogs. Fifty‐five dogs ranging from 6 to 39 kg were recruited and rate of gastric emptying was assessed using the OABT. The time to peak 13CO2excretion (tmax) and half‐dose recovery time (t1/2) were calculated. The OABT was simple to perform and well tolerated by the dogs. Mean (sd) tmaxwas 2.67 hours (0.6) and mean t1/2was 3.38 hours (0.79). Inter‐individual variation in the rate of gastric emptying was 23.3 per cent for t1/2and 22.5 per cent for tmaxNo association was detected between the rate of gastric emptying and body surface area, mass, age, sex or test operator. The OABT may be a useful non‐invasive and non‐radioactive test for assessment of the rate of gastric emptying in dogs in clinical practice.

Gastric emptying is the process by which food is delivered to the small intestine at a rate and in a form that optimizes intestinal absorption of nutrients. The rate of gastric emptying is subject to alteration by physiological, pharmacological, and pathological conditions. Gastric emptying of solids is of greater clinical significance because disordered gastric emptying rarely is detectable in the liquid phase. Imaging techniques have the disadvantage of requiring restraint of the animal and access to expensive equipment. Radiographic methods require administration of test meals that are not similar to food. Scintigraphy is the gold standard method for assessment of gastric emptying but requires administration of a radioisotope. Magnetic resonance imaging has not yet been applied for assessment of gastric emptying in small animals. Ultrasonography is a potentially useful, but subjective, method for assessment of gastric emptying in dogs. Gastric tracer methods require insertion of gastric or intestinal cannulae and are rarely applied outside of the research laboratory. The paracetamol absorption test has been applied for assessment of liquid phase gastric emptying in the dog, but requires IV cannulation. The gastric emptying breath test is a noninvasive method for assessment of gastric emptying that has been applied in dogs and cats. This method can be carried out away from the veterinary hospital, but the effects of physiological and pathological abnormalities on the test are not known. Advances in technology will facilitate the development of reliable methods for assessment of gastric emptying in small animals.

The objective of this study was to compare restricted suckling of tropical cows by their own or another cow's calf with artificial rearing of the calves and no suckling. In Exp. 1, cows were mechanically milked twice daily, after which for 15 min they were either suckled by their own calf (Treatment O) or multiple-suckled by other cows' calves (Treatment M) or unsuckled, with the calves reared artificially (Treatment A). Machine milk yield was similar for the three treatments, but in the two suckling treatments the additional milk consumed by the calf increased (P = 0.02) total production (2,682, 2,634, and 2,336 kg/lactation for Treatments O, M, and A, respectively). Machine milk fat concentration was reduced (P = 0.05) by suckling (2.90, 3.07, and 3.20% for Treatments 0, M, and A, respectively), but the milk sampled just before suckling (to represent that taken by the calves) had a high fat concentration (mean 7.9%). Machine milk somatic cell count was also reduced (P = 0.05) by suckling, from 106,000/mL (Treatment A) to 85,000/mL (Treatment M) and 95,000 (Treatment O). Cows suckling their own calf lost more weight and body condition than cows whose calves were reared artificially, with multiple-suckled calves intermediate. Cows suckling their own calf had postpartum interval to first estrus increased (P = 0.01) by 31 d and conception rates to first service of 44% compared to 77% for the other two treatments (P = 0.01). The growth of the suckled calves was compared with that of the artificially reared calves, which were given recommended milk allowances. The artificially reared calves consumed more milk and concentrates, which were available ad libitum to all calves, and gained (P = 0.03) 0.07 kg/d more weight than suckled calves. A second experiment determined that suckling once daily did not reduce reproductive performance compared to artificial rearing. We conclude that suckling cows twice daily increases total milk production but reduces body weight in early lactation. Cows suckling their own calves have reduced reproductive performance compared to those suckling other calves or reared artificially.

Stable isotope breath tests offer a new approach to the study of digestion and fermentation of carbohydrates in man. In this study, 13C labelled peas were grown by pulsing 250ml 13CO2 into a sealed growth chamber. A second pulse was added to a portion of the peas to increase the 13C enrichment. This generated pea flour with an enrichment of 2.36 at.% excess (range 2.09-2.71 n = 3) and 8.64 atom % excess (range 7.37-9.78 n = 3) respectively. This represented incorporation of an absolute yield of 3.8% of the 13CO2 into peas in the 'once-labelled' treatment and 7.5% in the 'twice-labelled' treatment. Ingestion of a mixture of the labelled pea flour (300 mg) by two volunteers generated measurable 13CO2 excretion for breath test analysis. The profile of breath 13CO2 enrichment increased to a maximum within three hours after consuming the pea flour followed by a decrease almost back to baseline by 13 hours. Breath 13CO2 appeared to rise again after this apparent nadir at 13 hours until the end of the sampling period. Mathematical analysis of the data suggested that two peaks best described the profile of breath 13CO2 up to 13 hours. A third peak was necessary to describe the late rise in breath 13CO2 enrichment. This use of 13C enriched pea flour may provide a useful non invasive method for measurement of digestion and fermentation in vivo.

This paper was presented in poster form at the 17th International Congress of Nutrition, August 27-31, Vienna. Austria (Annals of Nutrition & Metabolism 2001; 45(Suppl.1):349). Some of the data were also presented in poster form at the British Society of Gastroenterology Meeting, March 18-21, Glasgow, UK (Gut 2001; 48(Suppl.1):A91).The 13C-mixed triacylglycerol (MTG) breath test is used to measure intraluminal fat digestion. In normal digestion. 20-40% of the ingested 13C label is recovered in breath CO2. We aimed to identify the proportions of ingested label excreted in stool, as well as breath following ingestion of 13C-MTG by children with impaired exocrine pancreatic function and healthy controls. 13C enrichment of breath samples was measured by continuous flow isotope ratio mass spectrometry (IRMS) and cumulative percent dose recovered (cPDR) in 10 h was calculated. Total 13C of a faecal fat extract from each stool was measured by elemental analyser-IRMS, and 13C enrichment and concentration of the TBDMS derivative of octanoic acid was measured by GC/MS after hydrolysis of the fat extract. Stool 5-day cPDR was calculated. Mean breath cPDR was 35%. Mean cPDR in stool by combustion-IRMS and GC/ MS, respectively, was 0.8% and 1.0%. Therefore, the remaining 64% of the 13C label must remain in the body and variability in breath cPDR is due to postabsorptive rather than predigestive factors.

Background and Aims: Metabolic measurements (e.g. resting energy expenditure) are adjusted to lean body mass to account for body composition differences. Usually lean body mass is estimated from total body water. However, this may be compromised in weight-losing cancer patients owing to alterations in the degree of hydration of the lean body mass. This study examined the relationship between two independent estimates of lean body mass in healthy subjects and cancer patients with weight loss. Methods and Results: Height, weight, total body water and total body potassium were measured in healthy subjects (n=9) and weight losing cancer patients (n=13). They were similar in terms of age and gender. However, the cancer group had a significantly lower percentage ideal body weight (P&lt;0.001). The measured total body water values in both groups were similar to those predicted. In contrast, measured total body potassium values in the cancer group were significantly lower than predicted (P&lt;0.001). There was a correlation between the ratio of measured lean body mass (water/lean bodymass (potassium) and the percentage weight loss (r=0.698, P&lt;0.001). Conclusions: These results suggest that total body water significantly overestimates metabolically active tissue in weight-losing cancer patients and therefore its use as the basis for metabolic requirements in this group of patients is questionable. Copyright 2000 Harcourt Publishers Ltd

AbstractHigh-energy and high-intensity lasers are essential for pushing the boundaries of science. Their development has allowed leaps forward in basic research areas, including laser–plasma interaction, high-energy density science, metrology, biology and medical technology. The Helmholtz International Beamline for Extreme Fields user consortium contributes and operates two high-peak-power optical lasers using the high energy density instrument at the European X-ray free electron laser (EuXFEL) facility. These lasers will be used to generate transient extreme states of density and temperature to be probed by the X-ray beam. This paper introduces the ReLaX laser, a short-pulse high-intensity Ti:Sa laser system, and discusses its characteristics as available for user experiments. It will also present the first experimental commissioning results validating its successful integration into the EuXFEL infrastructure and viability as a relativistic-intensity laser driver.