Ultrasmooth Epitaxial Pt Thin Films Grown by Pulsed Laser Deposition.

Platinum (Pt) thin films are useful in applications requiring high-conductivity electrodes with excellent thermal and chemical stability. Ultrasmooth and epitaxial Pt thin films with single-crystalline domains have the added benefit of providing ideal templates for the subsequent growth of heteroepitaxial structures. Here, we grow epitaxial Pt (111) electrodes (ca. 30 nm thick) on sapphire (α-Al2O3 (0001)) substrates with pulsed laser deposition. This versatile technique allows control of the growth process and fabrication of films with carefully tailored parameters. X-ray scattering, atomic-force microscopy, and electron microscopy provide structural characterization of the films. Various gaseous atmospheres and temperatures were explored to achieve epitaxial growth of films with low roughness. A two-step (500 °C/300 °C) growth process was developed, yielding films with improved epitaxy without compromising roughness. The resulting films possess ultrasmooth interfaces (<3 Å) and high electrical conductivity (6.9 × 106 S/m). Finally, Pt films were used as current collectors and templates to grow lithium manganese oxide (LiMn2O4 (111)) epitaxial thin films, a cathode material used in Li-ion batteries. Using a solid-state ionogel electrolyte, the films were highly stable when electrochemically cycled in the 3.5-4.3 V vs Li/Li+ range.

Electrolyte Reactivity on the MgV2O4 Cathode Surface.

Predictive understanding of the molecular interaction of electrolyte ions and solvent molecules and their chemical reactivity on electrodes has been a major challenge but is essential for addressing instabilities and surface passivation that occur at the electrode-electrolyte interface of multivalent magnesium batteries. In this work, the isolated intrinsic reactivities of prominent chemical species present in magnesium bis(trifluoromethanesulfonimide) (Mg(TFSI)2) in diglyme (G2) electrolytes, including ionic (TFSI-, [Mg(TFSI)]+, [Mg(TFSI):G2]+, and [Mg(TFSI):2G2]+) as well as neutral molecules (G2) on a well-defined magnesium vanadate cathode (MgV2O4) surface, have been studied using a combination of first-principles calculations and multimodal spectroscopy analysis. Our calculations show that nonsolvated [Mg(TFSI)]+ is the strongest adsorbing species on the MgV2O4 surface compared with all other ions while partially solvated [Mg(TFSI):G2]+ is the most reactive species. The cleavage of C-S bonds in TFSI- to form CF3- is predicted to be the most desired pathway for all ionic species, which is followed by the cleavage of C-O bonds of G2 to yield CH3+ or OCH3- species. The strong stabilization and electron transfer between ionic electrolyte species and MgV2O4 is found to significantly favor these decomposition reactions on the surface compared with intrinsic gas-phase dissociation. Experimentally, we used state-of-the-art ion soft landing to selectively deposit mass-selected TFSI-, [Mg(TFSI):G2]+, and [Mg(TFSI):2G2]+ on a MgV2O4 thin film to form a well-defined electrolyte-MgV2O4 interface. Analysis of the soft-landed interface using X-ray photoelectron, X-ray absorption near-edge structure, electron energy-loss spectroscopies, as well as transmission electron microscopy confirmed the presence of decomposition species (e.g., MgFx, carbonates) and the higher amount of MgFx with [Mg(TFSI):G2]+ formed in the interfacial region, which corroborates the theoretical observation. Overall, these results indicate that Mg2+ desolvation results in electrolyte decomposition facilitated by surface adsorption, charge transfer, and the formation of passivating fluorides on the MgV2O4 cathode surface. This work provides the first evidence of the primary mechanisms leading to electrolyte decomposition at high-voltage oxide surfaces in multivalent batteries and suggests that the design of new, anodically stable electrolytes must target systems that facilitate cation desolvation.

Understanding the Solid-State Electrode-Electrolyte Interface of a Model System Using First-Principles Statistical Mechanics and Thin-Film X-ray Characterization.

Intermixing of atomic species at the electrode-electrolyte boundaries can impact the properties of the interfaces in solid-state batteries. Herein, this work uses first-principles statistical mechanics along with experimental characterization to understand intermixing at the electrode-electrolyte interface. For the model presented in this work, lithium manganese oxide (LiMn2O4, LMO) and lithium lanthanum titanate (Li3xLa2/3-xTiO3, LLTO) are employed as the cathode and electrolyte, respectively. The results of the computational work show that Ti-Mn intermixing at the interface is significant at synthesis temperatures. The experimental results in this work find that, at some critical temperatures between 600 and 700 °C for material preparation, the interface of LLTO-LMO becomes blurred. Calculations predict that the interface is unstable with regard to Ti-Mn intermixing starting at 0 K, suggesting that the critical temperature found in the experiment is related to kinetics. The work overall suggests that, in designing a solid-state battery, the fundamental reactions such as intermixing need to be considered.

Amorphous to Crystal Phase Change Memory Effect with Two-Fold Bandgap Difference in Semiconducting K2Bi8Se13.

Chalcogenide-based phase change memory (PCM) is a key enabling technology for optical data storage and electrical nonvolatile memory. Here, we report a new phase change chalcogenide consisting of a 3D network of ionic (K···Se) and covalent bonds (Bi-Se), K2Bi8Se13 (KBS). Thin films of amorphous KBS deposited by DC sputtering are structurally and chemically homogeneous and exhibit a surface roughness of 5 nm. The KBS film crystallizes upon heating at ∼483 K. The optical bandgap of the amorphous film is about 1.25 eV, while its crystalline phase has a bandgap of ∼0.65 eV shows 2-fold difference between the two states. The bulk electrical conductivity of the amorphous and crystalline film is ∼7.5 × 10-4 and ∼2.7 × 10-2 S/cm, respectively. We have demonstrated a phase change memory effect in KBS by Joule heating in a technologically relevant vertical memory cell architecture. Upon Joule heating, the vertical device undergoes switching from its amorphous to crystalline state of KBS at 1-1.5 V (∼50 kV/cm), increasing conductivity by a factor of ∼40. Besides the large electrical and optical contrast in the crystalline and amorphous KBS, its elemental cost-effectiveness, stoichiometry, fast crystallization kinetics, as determined by the ratio of the glass transition and melting temperature, Tg/Tm ∼ 0.5, as well as the scalable synthesis of the thin film determine that KBS is a promising PC material for next general phase change memory.

Origin of Enhanced Cyclability in Covalently Modified LiMn1.5Ni0.5O4 Cathodes.

High-voltage lithium-ion cathode materials exhibit exceptional energy densities; however, rapid capacity fade during cell cycling prohibits their widespread utilization. Surface modification of cathode-active materials by organic self-assembled monolayers (SAMs) has emerged as an approach to improve the longevity of high-voltage electrodes; however, the surface chemistry at the electrode/electrolyte interphase and its dependence on monolayer structure remains unclear. Herein, we investigate the interplay between monolayer structure, electrochemical performance, and surface chemistry of high-voltage LiMn1.5Ni0.5O4 (LMNO) electrodes by the application of silane-based SAMs of variable length and chemical composition. We demonstrate that the application of both hydrophobic and hydrophilic monolayers results in improved galvanostatic capacity retention relative to unmodified LMNO. The extent of this improvement is tied to the structure of the monolayer with fluorinated alkyl-silanes exhibiting the greatest overall capacity retention, above 96% after 100 charge/discharge cycles. Postmortem surface analysis reveals that the presence of the monolayer enhances the deposition of LiF at the electrode surface during cell cycling and that the total surface concentration correlates with the overall improvements in capacity retention. We propose that the enhanced deposition of highly insulating LiF increases the anodic stability of the interphase, contributing to the improved galvanostatic performance of modified electrodes. Moreover, this work demonstrates that the modification of the electrode surface by the selection of an appropriate monolayer is an effective approach to tune the properties and behavior of the electrode/electrolyte interphase formed during battery operation.

Understanding the Role of Overpotentials in Lithium Ion Conversion Reactions: Visualizing the Interface.

Oxide conversion reactions are known to have substantially higher specific capacities than intercalation materials used in Li-ion batteries, but universally suffer from large overpotentials associated with the formation of interfaces between the resulting nanoscale metal and Li2O products. Here we use the interfacial sensitivity of operando X-ray reflectivity to visualize the structural evolution of ultrathin NiO electrodes and their interfaces during conversion. We observe two additional reactions prior to the well-known bulk, three-dimensional conversion occurring at 0.6 V: an accumulation of lithium at the buried metal/oxide interface (at 2.2 V) followed by interfacial lithiation of the buried NiO/Ni interface at the theoretical potential for conversion (at 1.9 V). To understand the mechanisms for bulk and interfacial lithiation, we calculate interfacial energies using density functional theory to build a potential-dependent nucleation model for conversion. These calculations show that the additional space charge layer of lithium is a crucial component for reducing energy barriers for conversion in NiO.

Structural analysis of the initial lithiation of NiO thin film electrodes.

Observations of the initial lithiation of NiO electrodes demonstrate how to seed conversion reactions using interfaces in a thin film Ni/NiO bilayer architecture. Operando X-ray reflectivity (XRR) reveals that structural changes in a NiO film begin at potentials near the theoretical reduction potential (1.8-2.0 V) with detectable lithiation of both the buried Ni/NiO interface and the outer NiO surface that occur prior to the reaction of the NiO film. This initial conversion reaction is most pronounced in ultrathin NiO films (∼20 Å) with only small changes to the NiO film surface for thicker films (∼67 Å). The limited reactivity of thicker NiO films probed using operando grazing incidence small-angle X-ray scattering (GISAXS) shows the growth of nanoparticles at the electrode/electrolyte interface during initial lithium ion insertion, with a 16-20 Å average radius. Ex situ X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and scanning transmission electron microscopy/electron energy loss spectroscopy (STEM/EELS) confirm our conclusions about the morphological changes accompanying initial stage of lithiation in these conversion reaction electrodes. The present study reveals the interconnected challenges of solid-solid transitions, overpotentials, interfacial nucleation and kinetics, and transition metal dissolution in conversion-type electrodes that are critical for their use as electrodes in lithium-ion batteries.

Multistates and Polyamorphism in Phase-Change K2Sb8Se13.

The phase-change (PC) materials in the majority of optical data storage media in use today exhibit a fast, reversible crystal → amorphous phase transition that allows them to be switched between on (1) and off (0) binary states. Solid-state inorganic materials with this property are relatively common, but those exhibiting an amorphous → amorphous transition called polyamorphism are exceptionally rare. K2Sb8Se13 (KSS) reported here is the first example of a material that has both amorphous → amorphous polyamorphic transition and amorphous → crystal transition at easily accessible temperatures (227 and 263 °C, respectively). The transitions are associated with the atomic coordinative preferences of the atoms, and all three states of K2Sb8Se13 are stable in air at 25 °C and 1 atm. All three states of K2Sb8Se13 exhibit distinct optical bandgaps, Eg = 1.25, 1.0, and 0.74 eV, for the amorphous-II, amorphous-I, and crystalline versions, respectively. The room-temperature electrical conductivity increases by more than 2 orders of magnitude from amorphous-I to -II and by another 2 orders of magnitude from amorphous-II to the crystalline state. This extraordinary behavior suggests that a new class of materials exist which could provide multistate level systems to enable higher-order computing logic circuits, reconfigurable logic devices, and optical switches.

Nutrition care of cancer patients-A survey among physicians and nurses.

In order to quantify gaps in the provision of medical nutrition care in Germany and pinpoint specific areas of need, we collected data from patients, nurses and physicians. The results from the patient survey were published separately. A total of 506 participants from 69 certified centers answered the questions developed in cooperation with representatives from different professional groups (physicians, nurses and dietitians). Only about a third of participants reported that their institution provides structured pathways to nutritional counseling. 70.1% of those physicians reported that there was a specialist in nutrition available at their center while only 55.8% of nurses agreed. Only a quarter (24.2% and 26.9%) of physicians and nurses reported that their institution provided continuation of nutrition care after dismissal. A gap exists between need and consistent delivery of nutrition care services. Structured nutrition care pathways provided by legally certified nutrition professionals pathways are lacking. Cancer organizations may support this process by requiring documented nutrition care pathways and provision of services on a need based system into guidelines and certification criteria.

Lithiation of multilayer Ni/NiO electrodes: criticality of nickel layer thicknesses on conversion reaction kinetics.

X-ray reflectivity and transmission electron microscopy (TEM) were used to characterize the morphological changes in thin film electrodes with alternating Ni and NiO layers during lithiation as a function of the Ni buffer layer thickness. Complete lithiation of the active NiO layers occurs only when the thickness of the Ni/NiO bilayers are less than 75 Å - a threshold value that is determined by the sum of the Ni quantity in the Ni/NiO bilayer of the multilayer stack. Thicker Ni/NiO bilayers present a kinetic barrier for lithium ion diffusion inside the stack resulting in partial lithiation of the multilayer electrodes in which only the top NiO layer lithiates. Lithiation of NiO layers in a multilayer stack also leads to an interface-specific reaction that is observed to increase the thicknesses of adjacent Ni layers by 3-4 Å and is associated with the formation of a low-density Li2O layer, corresponding to an interfacially-driven phase separation of the NiO. Rate dependent cyclic voltammetry studies reveal a linear relation between the peak current and scan rate suggesting that the lithiation kinetics are controlled by charge transfer resistance at the liquid-solid interface.

Nutritional care of cancer patients: a survey on patients' needs and medical care in reality.

PURPOSE: Cancer patients represent a patient group with a wide-range of nutrition related problems which are often under-recognized and undertreated. In order to assess the status quo of nutritional care in Germany, we conducted a survey among patients with different types of cancer. METHODS: A standardized questionnaire was distributed online by two national umbrella organizations for self-help groups. RESULTS: 1335 participants completed the questionnaire. 69 % of the participants reported having received information on nutrition and/or specific nutrition-related symptoms. Most often this information was derived from print media (68.5 %) or from within self-help groups (58.7 %). 57.0 % of participants reported having had questions concerning nutrition and/or problems with food intake. most frequently named topics of interest were "healthy diet" (35.0 %) weakness/fatigue (24.3 %), dietary supplements (21.3 %) and taste changes (19.8 %). Nutrition information was most often provided by dietitians (38.7 %) followed by physicians (9.8 %). Women reported receiving nutrition counseling in the hospital nearly twice as often as men (12.5 % versus 5.7 %; p < 0.001). A quarter of the patients (24.1 %) reported using dietary supplements and patients who had received some sort of nutrition information more often reported using supplements (p < 0.001). CONCLUSION: Nutrition is an essential element in cancer care and patients report a high interest and need: Yet, many patients do not have access to high quality nutrition therapy during and after cancer therapy. IMPLICATIONS FOR CANCER SURVIVORS: With respect to survival and quality of life, increasing the availability and resources for provision of evidence based nutrition information seems mandatory.

Liquid Water- and Heat-Resistant Hybrid Perovskite Photovoltaics via an Inverted ALD Oxide Electron Extraction Layer Design.

Despite rapid advances in conversion efficiency (>22%), the environmental stability of perovskite solar cells remains a substantial barrier to commercialization. Here, we show a significant improvement in the stability of inverted perovskite solar cells against liquid water and high operating temperature (100 °C) by integrating an ultrathin amorphous oxide electron extraction layer via atomic layer deposition (ALD). These unencapsulated inverted devices exhibit a stable operation over at least 10 h when subjected to high thermal stress (100 °C) in ambient environments, as well as upon direct contact with a droplet of water without further encapsulation.

Improved nutrition in adolescents and young adults after childhood cancer - INAYA study.

BACKGROUND: Multimodality treatment improves the chance of survival but increases the risk for long-term side effects in young cancer survivors, so-called" Adolescents and Young Adults"(AYAs). Compared to the general population AYAs have a 5 to 15-fold increased risk of cardiovascular morbidity. Thus, improving modifiable lifestyle risk factors is of particular importance. METHODS: The INAYA trial included AYAs between 18 and 39 years receiving an intensified individual nutrition counseling at four time points in a 3-month period based on a 3-day dietary record. At week 0 and 12 AYAs got a face-to-face counseling, at week 2 and 6 by telephone. Primary endpoint was change in nutritional behavior measured by Healthy Eating Index - European Prospective Investigation into Cancer and Nutrition (HEI-EPIC). RESULTS: Twenty-three AYAs (11 female, 12 male, median age 20 years (range 19-23 years), median BMI: 21.4 kg/m2 (range: 19.7-23.9 kg/m2) after completion of cancer treatment for sarcoma (n = 2), carcinoma (n = 2), blastoma (n = 1), hodgkin lymphoma (n = 12), or leukemia (n = 6) were included (median time between diagnosis and study inclusion was 44 month). The primary endpoint was met, with an improvement of 20 points in HEI-EPIC score in 52.2 % (n = 12) of AYAs. At baseline, median HEI-EPIC score was 47.0 points (range from 40.0 to 55.0 points) and a good, moderate and bad nutritional intake was seen in 4.3, 73.9 and 21.7 % of AYAs. At week 12, median HEI-EPIC improved significantly to 65.0 points (range from 55.0 to 76.0 points) (p ≤ 0.001) and a good, moderate and bad nutritional intake was seen in 47.8, 52.2 and 0 % of AYAs. No change was seen in quality of life, waist-hip ratio and blood pressure. CONCLUSION: Intensified nutrition counseling is feasible and seem to improve nutritional behavior of AYAs. Further studies will be required to demonstrate long-term sustainability and confirm the results in a randomized design in larger cohorts. TRIAL REGISTRATION: Clinical trial identifier DRKS00009883 on DRKS.

Modular time division multiplexer: Efficient simultaneous characterization of fast and slow transients in multiple samples.

A modular time division multiplexer (MTDM) device is introduced to enable parallel measurement of multiple samples with both fast and slow decay transients spanning from millisecond to month-long time scales. This is achieved by dedicating a single high-speed measurement instrument for rapid data collection at the start of a transient, and by multiplexing a second low-speed measurement instrument for slow data collection of several samples in parallel for the later transients. The MTDM is a high-level design concept that can in principle measure an arbitrary number of samples, and the low cost implementation here allows up to 16 samples to be measured in parallel over several months, reducing the total ensemble measurement duration and equipment usage by as much as an order of magnitude without sacrificing fidelity. The MTDM was successfully demonstrated by simultaneously measuring the photoconductivity of three amorphous indium-gallium-zinc-oxide thin films with 20 ms data resolution for fast transients and an uninterrupted parallel run time of over 20 days. The MTDM has potential applications in many areas of research that manifest response times spanning many orders of magnitude, such as photovoltaics, rechargeable batteries, amorphous semiconductors such as silicon and amorphous indium-gallium-zinc-oxide.

Morphological Evolution of Multilayer Ni/NiO Thin Film Electrodes during Lithiation.

Oxide conversion reactions in lithium ion batteries are challenged by substantial irreversibility associated with significant volume change during the phase separation of an oxide into lithia and metal species (e.g., NiO + 2Li(+) + 2e(-) → Ni + Li2O). We demonstrate that the confinement of nanometer-scale NiO layers within a Ni/NiO multilayer electrode can direct lithium transport and reactivity, leading to coherent expansion of the multilayer. The morphological changes accompanying lithiation were tracked in real-time by in-operando X-ray reflectivity (XRR) and ex-situ cross-sectional transmission electron microscopy on well-defined periodic Ni/NiO multilayers grown by pulsed-laser deposition. Comparison of pristine and lithiated structures reveals that the nm-thick nickel layers help initiate the conversion process at the interface and then provide an architecture that confines the lithiation to the individual oxide layers. XRR data reveal that the lithiation process starts at the top and progressed through the electrode stack, layer by layer resulting in a purely vertical expansion. Longer term cycling showed significant reversible capacity (∼800 mA h g(-1) after ∼100 cycles), which we attribute to a combination of the intrinsic bulk lithiation capacity of the NiO and additional interfacial lithiation capacity. These observations provide new insight into the role of metal/metal oxide interfaces in controlling lithium ion conversion reactions by defining the relationships between morphological changes and film architecture during reaction.

[Interventional pain therapy. Results of a survey among specialized pain physicians in Germany]. / Interventionelle Schmerztherapie. Ergebnisse einer bundesweiten Umfrage unter speziellen Schmerztherapeuten.

BACKGROUND: Interventional pain therapy aims to treat pain which is refractory to pharmacologic and noninterventional treatment. Due to the partly lacking evidence and recommendations it remains unclear when interventional methods should be applied within the treatment pathway. This study assesses the current state of interventional methods in Germany and their leading indications comparing with the recommendations found in the literature. METHODS: An online survey was conducted among German physicians specialized in pain therapy concerning the number of interventions they perform per quarter, which supporting measures they use, and their indications for sympathetic blocks, sensory blocks, intrathecal administration, and spinal cord stimulation. RESULTS: A total of 109 physicians (23.5 %) participated in the survey. Blocks are most often performed on the stellate ganglion (94 %) and on the superior cervical ganglion (82 %). They are supported by anatomical landmarks and less often by imaging control. Both classic neuropathic pain diagnoses (e.g., complex regional pain syndrome) and diagnoses with a neuropathic pain component (e.g., peripheral arterial disease, tumor pain, and back pain) were considered as indications to perform interventional procedures. CONCLUSION: Although there is no clear evidence on interventional procedures in the current literature, these methods are often performed by the respondents. Anatomic landmarks are most frequently used for orientation. The German pain physicians who responded consider especially neuropathic pain as an indication to perform interventional procedures for pain therapy.

Three dimensional indium-tin-oxide nanorod array for charge collection in dye-sensitized solar cells.

In this article, we report the design, fabrication, characterization, and simulation of three-dimensional (3D) dye-sensitized solar cells (DSSCs), using ordered indium-tin-oxide (ITO) nanorod (NR) arrays as the photoanode, and compare them with conventional planar (2D) DSSCs. The ITO NR array used in the 3D cell greatly improves its performance by providing shorter electron pathways and reducing the recombination rate of the photogenerated electrons. We observed a 10-20% enhancement of the energy conversion efficiency, primarily due to an increased short circuit current. This finding supports the concept of using 3D photoanodes with optically transparent and conducting nanorods for the enhancement of the energy-harvesting devices that require short charge collection distance without sacrificing the optical thickness. Thus, unlike the conventional solar cell structure, the functions for photon collection and charge transport are decoupled to allow for improved cell designs.

Ultrafast modulation of the plasma frequency of vertically aligned indium tin oxide rods.

Light-matter interaction at the nanoscale is of particular interest for future photonic integrated circuits and devices with applications ranging from communication to sensing and imaging. In this Letter a combination of transient absorption (TA) and the use of third harmonic generation as a probe (THG-probe) has been adopted to investigate the response of the localized surface plasmon resonances (LSPRs) of vertically aligned indium tin oxide rods (ITORs) upon ultraviolet light (UV) excitation. TA experiments, which are sensitive to the extinction of the LSPR, show a fluence-dependent increase in the frequency and intensity of the LSPR. The THG-probe experiments show a fluence-dependent decrease of the LSPR-enhanced local electric field intensity within the rod, consistent with a shift of the LSPR to higher frequency. The kinetics from both TA and THG-probe experiments are found to be independent of the fluence of the pump. These results indicate that UV excitation modulates the plasma frequency of ITO on the ultrafast time scale by the injection of electrons into, and their subsequent decay from, the conduction band of the rods. Increases to the electron concentration in the conduction band of ∼13% were achieved in these experiments. Computer simulation and modeling have been used throughout the investigation to guide the design of the experiments and to map the electric field distribution around the rods for interpreting far-field measurement results.

The Structure and Properties of Amorphous Indium Oxide.

A series of In2O3 thin films, ranging from X-ray diffraction amorphous to highly crystalline, were grown on amorphous silica substrates using pulsed laser deposition by varying the film growth temperature. The amorphous-to-crystalline transition and the structure of amorphous In2O3 were investigated by grazing angle X-ray diffraction (GIXRD), Hall transport measurement, high resolution transmission electron microscopy (HRTEM), electron diffraction, extended X-ray absorption fine structure (EXAFS), and ab initio molecular dynamics (MD) liquid-quench simulation. On the basis of excellent agreement between the EXAFS and MD results, a model of the amorphous oxide structure as a network of InO x polyhedra was constructed. Mechanisms for the transport properties observed in the crystalline, amorphous-to-crystalline, and amorphous deposition regions are presented, highlighting a unique structure-property relationship.

Evolutionary reduction of developmental plasticity in desert spadefoot toads.

Organisms vary their rates of growth and development in response to environmental inputs. Such developmental plasticity may be adaptive and positively correlate with environmental heterogeneity. However, the evolution of developmental plasticity among closely related taxa is not well understood. To determine the evolutionary pattern of plasticity, we compared plasticity in time to and size at metamorphosis in response to water desiccation in tadpoles among spadefoot species that differ in breeding pond and larval period durations. Like most tadpoles, spadefoot tadpoles possess the remarkable ability to accelerate development in response to pond drying to avoid desiccation. Here, we hypothesize that desert spadefoot tadpoles have evolved reduced plasticity to avoid desiccation in ephemeral desert pools compared to their nondesert relatives that breed in long-duration ponds. We recorded time to and size at metamorphosis following experimental manipulation of water levels and found that desert-adapted species had much less plasticity in larval period and size at metamorphosis than nondesert species, which retain the hypothetical ancestral state of plasticity. Furthermore, we observed a correlation between degree of plasticity and fat body content that may provide mechanistic insights into the evolution of developmental plasticity in amphibians.