Two-way NxP fertilisation experiment on barley (Hordeum vulgare) reveals shift from additive to synergistic N-P interactions at critical phosphorus fertilisation level.

In a pot experiment, we investigated synergistic interaction of N and P fertilisation on barley biomass (Hordeum vulgare) on both shoot and root level with the aim to determine whether N-P interaction would be the same for all levels of N and P fertilisation. We further aimed to determine whether there was a critical level of N and/or P fertilisation rate, above which, a decrease in resource allocation to roots (as nutrient availability increased) could be demonstrated. Barley plants were grown from seed on a nutrient poor substrate and subjected to a two-way NxP fertilisation gradient using a modified Hoagland fertilisation solution. We observed N-P interactions in shoot and root biomass, and N and P use-efficiencies. A synergistic response in biomass was observed only above a critical level of P fertilisation when P was not limiting growth. Furthermore, we found that the same incremental increase in N:P ratio of applied fertiliser elicited different responses in shoot and root biomass depending on P treatment and concluded that barley plants were less able to cope with increasing stoichiometric imbalance when P was deficient. We provide, for the first time, stoichiometric evidence that critical levels for synergistic interactions between N-P may exist in crop plants.

A giant armoured skink from Australia expands lizard morphospace and the scope of the Pleistocene extinctions.

There are more species of lizards and snakes (squamates) alive today than any other order of land vertebrates, yet their fossil record has been poorly documented compared with other groups. Here, we describe a gigantic Pleistocene skink from Australia based on extensive material that includes much of the skull and postcranial skeleton, and spans ontogenetic stages from neonate to adult. Tiliqua frangens substantially expands the known ecomorphological diversity of squamates. At approximately 2.4 kg, it was more than double the mass of any living skink, with an exceptionally broad, deep skull, squat limbs and heavy, ornamented body armour. It probably filled the armoured herbivore niche that land tortoises (testudinids), absent from Australia, occupy on other continents. Tiliqua frangens and other giant Plio-Pleistocene skinks suggest that small-bodied groups that dominate vertebrate biodiversity might have lost their largest and often most morphologically extreme representatives in the Late Pleistocene, expanding the scope of these extinctions.

A decade of invertebrate recruitment at Santa Catalina Island, California.

Marine fouling communities have long provided model systems for studying the ecology of community development, and settlement plates are the tool of choice for this purpose. Decades of plate deployments provide a baseline against which present-day trends can be interpreted, with one classic trend being the ultimate dominance of plates by colonial and encrusting taxa. Here we report the results of annual deployments of settlement plates from 2010 to 2021 in the shallow sub-tidal of southern California, where the recruitment of invertebrates and algae was recorded photographically, and resolved to functional group (solitary, encrusting, and arborescent) and the lowest taxon possible. The communities on these plates differed among years, with trends in abundances varying by functional group and taxon; solitary taxa consistently were abundant, but encrusting taxa declined in abundance. Seawater temperature and the subsurface concentration of chlorophyll a differed among years, and there was a weak inverse association between temperature and the abundances of encrusting taxa. Long-term increases in seawater temperature therefore could serve as a mechanism causing fouling communities to change. Because of the prominence of encrusting taxa in fouling communities, the shifts in abundance of this functional group reported here may portend ecologically significant changes in fouling communities exposed to warmer seawater because of an alleviation of competition for a classically limiting resource (i.e., space).

Breastfeeding Attitudes and Practices in a Rural Utah Navajo Community.

OBJECTIVES: Despite known health benefits of breastfeeding, the Navajo have low reported frequency of breastfeeding initiation and support. We evaluated breastfeeding frequencies and practices in the predominately Navajo community of rural San Juan County, Utah, to identify factors that affect breastfeeding decisions and duration. METHODS: We performed retrospective chart review for 135 infants aged 0 to 12 months, and surveys of 85 mothers of infants aged 0 to 2 years, and eight primary care providers. We characterized demographic factors using counts/percentages and medians/inter-quartile ranges, and compared mothers who breastfed for 6 months or less versus greater than 6 months. RESULTS: In 96 infants with complete feeding documentation, 86 infants (90%) received some breast milk and 36 infants (38%) were exclusively breastfed at age 2 months. In 67 infants with complete feeding documentation at ≥ 6 months, 22 infants (33%) were exclusively breastfed 6 months. Most mothers knew about breastfeeding benefits. In 56 mothers whose infants were aged ≥ 6 months at the time of the survey, breastfeeding for more than 6 months had been planned by 44 mothers (79%) but performed by only 29 mothers (52%). Mothers who breastfed for > 6 months were more likely to have been influenced by WIC and less likely to have introduced formula at an early age. Barriers to breastfeeding included maternal pain, latch difficulties, and concerns about inadequate milk supply. Primary care providers reported limited confidence in providing breastfeeding support but would support telehealth-driven interventions. CONCLUSIONS FOR PRACTICE: Practical, culturally sensitive interventions, including telehealth and improved provider education, may improve breastfeeding outcomes and community health in this underserved population.

Dressed Rabi Oscillation in a Crystalline Organic Radical.

Free electron laser-powered pulsed electron paramagnetic resonance experiments performed at 240 GHz/8.56 T on the crystalline organic radical 1,3-bisdiphenylene-2-phenylallyl reveal a tip-angle dependent resonant frequency. Frequency shifts as large as 11 MHz (45 ppm) are observed during a single Rabi oscillation. We attribute the frequency shifts to a "dressing" of the nutation by spin-spin interactions. A nonlinear semiclassical model which includes a temperature- and sample-geometry-dependent demagnetizing field reproduces experimental results. Because experiments are performed without a cavity, radiation damping, the most common nonlinear interaction in magnetic resonance, is negligible in our experiments.

Multi-step phase-cycling in a free-electron laser-powered pulsed electron paramagnetic resonance spectrometer.

Electron paramagnetic resonance (EPR) is a powerful tool for research in chemistry, biology, physics and materials science, which can benefit significantly from moving to frequencies above 100 GHz. In pulsed EPR spectrometers driven by powerful sub-THz oscillators, such as the free electron laser (FEL)-powered EPR spectrometer at UCSB, control of the duration, power and relative phases of the pulses in a sequence must be performed at the frequency and power level of the oscillator. Here we report on the implementation of an all-quasioptical four-step phase cycling procedure carried out directly at the kW power level of the 240 GHz pulses used in the FEL-powered EPR spectrometer. Phase shifts are introduced by modifying the optical path length of a 240 GHz pulse with precision-machined dielectric plates in a procedure we call phase cycling with optomechanical phase shifters (POPS), while numerical receiver phase cycling is implemented in post-processing. The POPS scheme was successfully used to reduce experimental dead times, enabling pulsed EPR of fast-relaxing spin systems such as gadolinium complexes at temperatures above 190 K. Coherence transfer pathway selection with POPS was used to perform spin echo relaxation experiments to measure the phase memory time of P1 centers in diamond in the presence of a strong unwanted FID signal in the background. The large excitation bandwidth of FEL-EPR, together with phase cycling, enabled the quantitative measurement of instantaneous electron spectral diffusion, from which the P1 center concentration was estimated to within 10%. Finally, phase cycling enabled saturation-recovery measurements of T1 in a trityl-water solution at room temperature - the first FEL-EPR measurement of electron T1.

Small Gd(III) Tags for Gd(III)-Gd(III) Distance Measurements in Proteins by EPR Spectroscopy.

The C7-Gd and C8-Gd tags are compact hydrophilic cyclen-based lanthanide tags for conjugation to cysteine residues in proteins. The tags are enantiomers, which differ in the configuration of the 2-hydroxylpropyl pendant arms coordinating the lanthanide ion. Here, we report the electron paramagnetic resonance (EPR) performance of the C7-Gd ( S configuration) and C8-Gd ( R configuration) tags loaded with Gd(III) on two mutants of the homodimeric ERp29 protein. The W-band EPR spectra were found to differ between the tags in the free state and after conjugation to the protein. In addition, the spectra were sensitive to the labeling position, which may originate from an environment-dependent charge density on the Gd(III)-coordinating oxygens. This is in agreement with previous NMR experiments with different lanthanide ions, which suggested sensitivity to H-bonding. W-band 1H-ENDOR (electron-electron double resonance) experiments detected effects from orientation selection in the central transition, due to a relatively narrow distribution in the ZFS parameters as indicated by simulations. In contrast, the distance distributions derived from DEER (double electron-electron resonance) measurements were insensitive to the R or S configuration of the tags and did not exhibit any orientation selection effects. The DEER measurements faithfully reflected the different widths of the distance distributions at the different protein sites in agreement with previous DEER measurements using other Gd(III) tags. Due to their small size, short tether to the protein, and a broad central EPR transition, the C7-Gd and C8-Gd tags are attractive Gd(III) tags for measurements of relatively short (<4 nm) distances by EPR spectroscopy.

Quantitative analysis of zero-field splitting parameter distributions in Gd(iii) complexes.

The magnetic properties of paramagnetic species with spin S > 1/2 are parameterized by the familiar g tensor as well as "zero-field splitting" (ZFS) terms that break the degeneracy between spin states even in the absence of a magnetic field. In this work, we determine the mean values and distributions of the ZFS parameters D and E for six Gd(iii) complexes (S = 7/2) and critically discuss the accuracy of such determination. EPR spectra of the Gd(iii) complexes were recorded in glassy frozen solutions at 10 K or below at Q-band (∼34 GHz), W-band (∼94 GHz) and G-band (240 GHz) frequencies, and simulated with two widely used models for the form of the distributions of the ZFS parameters D and E. We find that the form of the distribution of the ZFS parameter D is bimodal, consisting roughly of two Gaussians centered at D and -D with unequal amplitudes. The extracted values of D (σD) for the six complexes are, in MHz: Gd-NO3Pic, 485 ± 20 (155 ± 37); Gd-DOTA/Gd-maleimide-DOTA, -714 ± 43 (328 ± 99); iodo-(Gd-PyMTA)/MOMethynyl-(Gd-PyMTA), 1213 ± 60 (418 ± 141); Gd-TAHA, 1361 ± 69 (457 ± 178); iodo-Gd-PCTA-[12], 1861 ± 135 (467 ± 292); and Gd-PyDTTA, 1830 ± 105 (390 ± 242). The sign of D was adjusted based on the Gaussian component with larger amplitude. We relate the extracted P(D) distributions to the structure of the individual Gd(iii) complexes by fitting them to a model that superposes the contribution to the D tensor from each coordinating atom of the ligand. Using this model, we predict D, σD, and E values for several additional Gd(iii) complexes that were not measured in this work. The results of this paper may be useful as benchmarks for the verification of quantum chemical calculations of ZFS parameters, and point the way to designing Gd(iii) complexes for particular applications and estimating their magnetic properties a priori.

Gd3+-Gd3+ distances exceeding 3 nm determined by very high frequency continuous wave electron paramagnetic resonance.

Electron paramagnetic resonance spectroscopy in combination with site-directed spin labeling is a very powerful tool for elucidating the structure and organization of biomolecules. Gd3+ complexes have recently emerged as a new class of spin labels for distance determination by pulsed EPR spectroscopy at Q- and W-band. We present CW EPR measurements at 240 GHz (8.6 Tesla) on a series of Gd-rulers of the type Gd-PyMTA-spacer-Gd-PyMTA, with Gd-Gd distances ranging from 1.2 nm to 4.3 nm. CW EPR measurements of these Gd-rulers show that significant dipolar broadening of the central |-1/2〉 → |1/2〉 transition occurs at 30 K for Gd-Gd distances up to ∼3.4 nm with Gd-PyMTA as the spin label. This represents a significant extension for distances accessible by CW EPR, as nitroxide-based spin labels at X-band frequencies can typically only access distances up to ∼2 nm. We show that this broadening persists at biologically relevant temperatures above 200 K, and that this method is further extendable up to room temperature by immobilizing the sample in glassy trehalose. We show that the peak-to-peak broadening of the central transition follows the expected 1/r3 dependence for the electron-electron dipolar interaction, from cryogenic temperatures up to room temperature. A simple procedure for simulating the dependence of the lineshape on interspin distance is presented, in which the broadening of the central transition is modeled as an S = 1/2 spin whose CW EPR lineshape is broadened through electron-electron dipolar interactions with a neighboring S = 7/2 spin.

Utility of history and physical updates for ambulatory otolaryngic surgery.

OBJECTIVES/HYPOTHESIS: Preoperative assessment is intended to identify anesthetic risk and a patient's appropriateness to undergo a proposed surgery. The timing of these assessments varies among institutions. In our ambulatory surgery center, preoperative reassessments were initially performed within 30 days of surgery (group A). Recently, this changed to require reassessments within 7 days of surgery (group B). Now, the policy mandates a preoperative reassessment within 24 hours (group C). We evaluate whether there are differences in surgical cancellations based on these new reassessment intervals. STUDY DESIGN: Retrospective operative log and chart review. METHODS: We identified 1,108 cases representative of group A. The rate of surgical cancellations for this group was compared with that of the 3,705 cases in group B and the 1,060 cases in group C. Differences were evaluated with a chi test. RESULTS: Total cancellation rates for groups A, B, and C were 3.0%, 3.3%, and 3.9%, respectively (P = .51). Cancellations secondary to a history and physical examination findings during these preoperative reassessment periods were 0.81%, 0.38%, and 0.66% for groups A, B, and C, respectively (P = .15). CONCLUSIONS: Cancellation rates for patients undergoing ambulatory otolaryngic surgery based on preoperative reassessment intervals of 30 days, 7 days, and 24 hours were similar.