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STARDOM2 is a randomized, double-blind, phase 3 trial evaluating the efficacy and safety of co-crystal of tramadol-celecoxib (CTC)-a first-in-class analgesic co-crystal comprising racemic tramadol hydrochloride and celecoxib in a supramolecular network that modifies their pharmacokinetic properties-for the management of acute postoperative pain (NCT03062644; EudraCT:2016-000593-38).Patients with moderate-to-severe pain following abdominal hysterectomy were randomized 2:2:2:2:2:1 to oral CTC 100 mg (rac-tramadol hydrochloride 44 mg/celecoxib 56 mg) twice daily (BID); CTC 150 mg (66/84 mg) BID; CTC 200 mg (88/112 mg) BID; immediate-release tramadol 100 mg four times daily (QID); celecoxib 100 mg BID; or placebo, for 5 days. The primary endpoint was the sum of pain intensity differences over 0-4 h (SPIDsub0-4/sub). Key secondary endpoints were rescue medication use within 4 h, 50% response rate at 4 h, and safety/tolerability.Of 1355 patients enrolled, 1138 were randomized (full analysis set) and 1136 treated (safety analysis set). In the prespecified gatekeeping analysis of SPIDsub0-4/sub, CTC 200 mg was not superior to tramadol but showed non-inferior efficacy (p lt; 0.001) that was sustained throughout the 120-h period, despite a 5-day cumulative tramadol administration of 880 mg with CTC 200 mg BID versus 2000 mg with tramadol 100 mg QID. Treatment-emergent adverse events (TEAEs) and severe TEAEs were less common with CTC 200 mg versus tramadol. Treatment-related TEAEs were 14.4% with CTC 200 mg and 23.6% with tramadol.Although the study did not meet its primary endpoint, CTC 200 mg showed a clinically relevant improvement in overall benefit/risk profile versus tramadol alone, with considerably lower cumulative opioid exposure.In the randomized, double-blind, phase 3 STARDOM2 trial-in acute moderate-to-severe pain after abdominal hysterectomy-the novel co-crystal of tramadol-celecoxib (CTC) 200 mg BID was superior to placebo and non-inferior to tramadol 100 mg QID. Although superiority to tramadol was not reached, CTC 200 mg BID exposed patients to lower cumulative opioid (tramadol) doses than tramadol (100 mg QID) alone, with fewer treatment-emergent adverse events. CTC 200 mg thus has a clinically relevant improved benefit/risk profile compared with tramadol alone.

Endogenous opioid peptides and exogenous opioids modulate immune function, and animal and human studies have shown that some have a depressant immunomodulatory effect. This is potentially of high clinical significance, eg, in cancer patients and surgery. The primary objective of this pilot study was to evaluate the effect of morphine and oxycodone on immune pathways associated with immunosuppression in gynecological laparotomy patients. Gene expression was analyzed in CD4, CD8, and natural killer (NK) cells using the 3' Affymetrix microarray. Patients were randomized to receive morphine, oxycodone, or nonopioid "control" analgesia during and after surgery. Genes demonstrating differential expression were those with a ≥±2-fold difference and P-value ≤0.05 after analysis of variance. Cytometric bead array and NK cell degranulation assay were used to investigate changes in serum cytokine concentration and in NK cell cytotoxicity, respectively. Forty patients had satisfactory RNA which was hybridized to gene chips. Genes were identified (Partek Genomics Suite 6.6) at baseline, 2, 6, and 24 hours and were either ≥2-fold upregulated or downregulated from baseline. At 2 hours, a large number of genes were downregulated with morphine but not with control analgesia or oxycodone. Statistically significant increases in IL-6 concentrations were induced by morphine only; NK cell activity was suppressed with morphine, but maintained with oxycodone and epidural analgesia. Gene expression profiles suggest that at 2 hours, post incision morphine appeared to be immunosuppressive as compared to oxycodone and nonopioid control analgesia.

Novel Monetite nanorods were successfully prepared for fluoride removal for the first time. The fluoride adsorption on the Monetite nanorods was studied by the batch adsorption technique. The Monetite nanorods were characterized by transmission electron microscope (TEM), X-ray powder diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), and the point of zero charge (pHPZC) measurement. The results revealed that the Monetite nanorods transformed to fluorapatite after adsorbing fluoride. The adsorption kinetics followed the pseudo-second-order model, and the adsorption isotherms could be well described by the Sips model. The maximum adsorption capacity was 222.88 mg g−1 at pH 7, 328 K when the initial fluoride concentration was 300 mg L−1 and the Monetite dose was 1 g L−1. The thermodynamic parameters revealed that the adsorption of fluoride onto Monetite nanorods was spontaneous and endothermic. The effects of different parameters including adsorbent dosage, pH, initial fluoride concentration and co-existing anions were investigated to understand the adsorption behaviour of Monetite nanorods under various conditions. Their adsorption capacities decreased with the increase of adsorbent dosage, and also decreased with the increase of pH. Electrostatic attraction and ion exchange were found to be the major mechanisms governing the adsorption of fluoride onto Monetite nanorods. Furthermore, a field study was conducted with the water from a fluoride endemic area in Tanzania. This study demonstrated that the synthesized Monetite nanorods were very effective adsorbents for defluoridation applications.

Tapentadol is a single molecule able to deliver analgesia by two distinct mechanisms, a feature which differentiates it from many other analgesics. Pre-clinical data demonstrate two mechanisms of action: mu-opioid receptor agonist activity and noradrenaline re-uptake inhibition. From these, one may predict that tapentadol would be applicable across a broad spectrum of pain from nociceptive to neuropathic. The evidence in animal models suggests that norepinephrine re-uptake inhibition (NRI) is a key mechanism and may even predominate over opioid actions in chronic (and especially neuropathic) pain states, reinforcing that tapentadol is different to classical opioids and may, therefore, be an a priori choice for the treatment of neuropathic and mixed pain. The clinical studies and subsequent practice experience and surveillance support the concept of opioid and non-opioid mechanisms of action. The reduced incidence of some of the typical opioid-induced side effects, compared to equianalgesic doses of classical opioids, supports the hypothesis that tapentadol analgesia is only partially mediated by opioid agonist mechanisms. Both the pre-clinical and clinical profiles appear to be differentiated from those of classical opioids.

Radiofrequency neurotomy (RFN) is a therapy aimed at providing lasting back pain relief for sacroiliac joint (SIJ) pain. A recent advancement in RFN is a strip lesioning technique that involves placement of a single curved electrode and a 3-pole design that facilitates the creation of 5 overlapping lesions. These lesions form one long strip lesion accessible through a single entry point, without the need for multiple punctures. Although the early case series data looks promising, there is lack of long-term, randomized, controlled study evaluating the strip-lesioning system for SIJ pain.The purpose of this study was to examine the safety and effectiveness of RFN using a strip lesioning device for reduction of SIJ pain.Prospective, double-blind, randomized, sham-controlled trial with 6-month follow-upSETTING: A tertiary care interventional pain management center in the UK METHODS: Patients with SIJ pain with positive diagnostic local anesthetic blocks were randomly assigned (2:1) to either the sham (no RF lesions performed) or the active group (RF lesions performed). The primary endpoint was improvement of pain using the Numeric Rating Scale (NRS-11) at 3 months. Results were analyzed using nonparametric tests. Safety, secondary, and long-term outcome data were also collected.Seventeen of 30 enrolled patients were randomly assigned to active treatment (n = 11) or sham treatment (n = 6). At 3 months, the mean NRS-11 score for the active group had decreased significantly, from 8.1 (± 0.8) at baseline to 3.4 (± 2.0) (P0.001). The sham group did not experience a statistically or clinically meaningful decrease in mean NRS-11 score from baseline (7.3 ± 0.8) to 3 months (7.0 ± 1.7). On average, patients in the active group moved from borderline anxiety at baseline (9.4 ± 5.9) to no anxiety (6.6 ± 6.3) at 3 months. Results were similar at 6 months.Recruitment was stopped at 30 enrolled patients, only 17 of whom were randomly assigned to active or sham treatment, after the interim analysis indicated a statistically significant (P0.001) difference in the pain outcome between the treatment and the sham groups.This study demonstrated that radiofrequency neurotomy using a strip lesioning device is an appropriate therapy to treat SIJ pain.Radiofrequency, sacroiliac joint pain, low back pain, neurotomy, randomized controlled trial, simplicity.

Advanced materials 30(19), 1702057 (2017). doi:10.1002/adma.201702057, Most studies of structural color in nature concern periodic arrays, which through the interference of light create color. The “color” white however relies on the multiple scattering of light within a randomly structured medium, which randomizes the direction and phase of incident light. Opaque white materials therefore must be much thicker than periodic structures. It is known that flying insects create “white” in extremely thin layers. This raises the question, whether evolution has optimized the wing scale morphology for white reflection at a minimum material use. This hypothesis is difficult to prove, since this requires the detailed knowledge of the scattering morphology combined with a suitable theoretical model. Here, a cryoptychographic X‐ray tomography method is employed to obtain a full 3D structural dataset of the network morphology within a white beetle wing scale. By digitally manipulating this 3D representation, this study demonstrates that this morphology indeed provides the highest white retroreflection at the minimum use of material, and hence weight for the organism. Changing any of the network parameters (within the parameter space accessible by biological materials) either increases the weight, increases the thickness, or reduces reflectivity, providing clear evidence for the evolutionary optimization of this morphology., Published by Wiley-VCH, Weinheim

The particle impact behavior of Stellite 6 on steel substrate in the supersonic laser deposition (SLD) process is studied using numerical simulation, compared with experimental data. The impact characteristics of Stellite 6 are analyzed with respect to particle size and deposition temperature. The simulation results show that laser deposition temperature of 1000 °C for the substrate is the optimal in terms of the interface bonding between the particles and substrate. The particle size of 40 μm exhibits the best deposition interface. The simulation results agree well with the experimental measurements. The depths of impact indentation with different particle sizes and at different temperatures are investigated to obtain the relationships between process parameters such as particle diameter, indentation depth, and deposition temperature. To further understand the effects of collisional behavior of multi-particles on the stress-strain distributions and the micro-zone in the particle and substrate system, different micro-zones of the impact particle are analyzed; the variations of the stress and strain with time for the substrate and particle are obtained from the simulation results. The impact characteristics of Stellite 6 deposited on steel substrate are discussed.

The control of semi-crystalline polymers in thin films and in micrometer-sized patterns is attractive for (opto-)electronic applications. Electro-hydrodynamic lithography (EHL) enables the structure formation of organic crystalline materials on the micrometer length scale while at the same time exerting control over crystal orientation. This gives rise to well-defined micro-patterned arrays of uniaxially aligned polymer crystals. This study explores the interplay of EHL structure formation with crystal alignment and studies the mechanisms that give rise to crystal orientation in EHL-generated structures.

Mesoporous distributed Bragg reflectors (MDBRs) exhibit porosity on the sub-wavelength scale. They are promising device components for biological and chemisal sensing as well as for light management in optoelectronic devices. In this chapter a new route for the fabrication of MDBRs is presented which relies on the structure directing properties of the block copolymer poly(isoprene-block-ethylene oxide) in combination with sol-gel chemistry. The interplay between structure directing organic host and coassembled inorganic guest allows the fine tuning of refractive index in the outcome material. Stacking high and low refractive index films in sequential order enables the fast and reliable construction of MDBRs which exhibit a continuous TiO2 network with large accessible pores and high optical quality.

Residual stresses in crystalline or glassy materials often play a key role in the performance of advanced devices and components. However, stresses in amorphous materials cannot easily be determined at the micron scale by diffraction, or by other conventional laboratory methods. In this article, a technique for mapping residual stress profiles in amorphous materials with high spatial definition is presented. By applying a focused ion beam (FIB)–based semidestructive mechanical relaxation method, the stresses are mapped in a peened and fatigued bulk metallic glass (BMG) (Zr50Cu40Al10 at. pct). The residual stresses are inferred using finite element analysis (FEA) of the surface relaxations, as measured by digital image correlation (DIC), that occur when a microslot is micromachined by FIB. Further, we have shown that acceptable accuracy can in most cases be achieved using a simple analytical model of the slot. It was found that the fatigue cycling significantly changes the distribution of compressive residual stresses with depth in the plastically deformed surface layer. Our observations point to the scalability of this method to map residual stresses in volumes as small as 1 × 1 × 0.2 μm3 or less.

This edition of the British Journal of Pain (BJP) marks a momentous development in the evolution of our Society’s journal. Back in 2007, its predecessor, Reviews in Pain, was launched with the aim of providing concise summaries of basic sciences and clinical practice relevant to contemporary pain management. Initially, each issue contained a mixture of topics with the aim of interesting the multidisciplinary membership of the British Pain Society. Each article was accompanied by summary points and multiple-choice questions for those readers wishing to demonstrate continuing professional development. More recently, the focus changed to commissioning themed issues on topics as diverse as neuropathic pain, failed back surgery syndrome, pain education, trauma, orofacial pain and visceral pain. Since 2012 the team at SAGE Publications has supported the editorial board by enhancing the professional nature of the publication. Last year, we introduced the publication of abstracts from the British Pain Society’s Annual Scientific Meeting in the first supplement to the BJP. In order to increase the scope of the journal, an editorial decision (endorsed by Council) was taken to accept original research submissions, and the preceding issue contained the first two original papers. It is exciting that we now have a sufficient number of manuscripts that have been through the peer-review process to allow a whole edition to be dedicated to publication of original research. Research requires two things. First, knowing what has already been discovered and having a background knowledge of the subject; second, formulation of appropriate methodologies that will help provide evidence to answer identified gaps in the literature. Although the thought of research may seem daunting to many, particularly for already time-pressed clinicians, most are inquisitive and have questions about their practice. Research and evaluation projects do not always have to be costly and time consuming. Think about how your questions might be turned into small-scale research projects and do consider the BJP when submitting your work for publication. Although reviews are important in keeping informed as to the latest developments in a particular field, it is only by original thought and research that our knowledge will advance in order to improve outcomes for patients who experience pain. The journal does not stand still, however, and it is hoped that each edition from 2014 will include at least one systematic review in addition to topical reviews and primary research. Over the years Reviews in Pain and the BJP have been fortunate to have several inspirational and visionary editors: Professor Jon Raphael; Dr Michael Platt and Felicia Cox jointly; and, more recently, Felicia alone. The inclusion of primary research in the BJP develops and strengthens its position in our field.

Gender differences in suicide-related behaviorswere examined in an older adolescent and a young adultsample (primarily Caucasian). Suicide-related behaviorswere assessed by the Life Attitudes Schedule (LAS) as well as by measures of depressivesymptomatology and hopelessness. The LAS measures a broadcontinuum of potentially life-diminishing orlife-enhancing behaviors. There are four LAScontent-category subscales: overtly suicidal and death-related,self-related, risk and injury-related, and health-relatedbehaviors. As hypothesized, in both samples, genderdifferences in the expression of suicide-related behaviors were obtained. Males from both samplesendorsed substantially more risk-taking andinjury-producing behaviors than females. Males in bothsamples also reported more negative health-relatedbehaviors than females. In contrast, females reported moresymptoms of depression than males. Hopelessness scoresonly differentiated male and female young adults; maleand female adolescents did not differ significantly on the hopelessness measure. These findings areprimarily discussed in terms of gender-role socializationtheory. Implications for the treatment of suicidality aredrawn.

Dentin hypersensitivity (DH) is a prevalent problem. This study aimed to formulate a paste using fluorhydroxyapatite (FA) crystals dispersed in different carriers to treat DH. The ability to occlude patent dentinal tubules and to release ions was investigated.Twenty percent FA/sodium alginate, 40% FA/poly(hydroxyethyl methacylate(HEMA)), and 40% FA/poly(DMA-co-MEA) were applied to etched dentin samples and examined with scanning electron microscopy (SEM) to determine the degree of tubule occlusion. Fluoride electrode was used to measure F release and spectroscopy to evaluate Ca and PO4 release. The cytotoxicity of the synthesized poly(DMA-co-MEA) gel was tested. Kruskall-Wallis test was used to test the differences in ion release between the groups.FA/poly(DMA-co-MEA) paste obstructed up to 80% of the dentinal tubules, while the coverage was up to 70% for FA/poly(HEMA) and less than 50% for FA/sodium alginate. Fluoride and Ca release was the highest for FA/P(HEMA), 7.2 ± 0.7 and 139.8 ± 32.5 ppm, respectively. The highest concentration of PO4 was 46.2 ± 16.4 ppm for FA/Sodium alginate. No statistical significance was found.FA/Poly(DMA-co-MEA) and FA/poly(HEMA) pastes may offer immediate short-term relief of DH because of their ability to occlude the tubules and adhere to wet dentin surfaces. The release of the F, Ca, and PO4 ions may offer long-term relief by forming a mineral barrier both within the dentinal tubules and on the dentin surface.The tested materials may offer a long-term treatment for DH.

In this work we report the thermal oxidation of amorphous germanium (a-Ge) thin films (140 nm thickness) in air. Following fabrication by conventional thermal evaporation on SiO2 substrates, the samples were annealed in air at different temperatures ranging from 300 to 1000 °C. By means of x-ray diffraction, x-ray reflectivity, synchrotron grazing-incidence wide-angle x-ray scattering and cross-sectional transmission electron microscopy analysis it is found that the a-Ge films abruptly crystallize at 475 °C, while simultaneously increasing the thickness of the oxide (GeO2) in a layer by layer fashion. X-ray photoemission spectroscopy reveals that the oxidation state of the Ge atoms in the GeO2 layer is 4+. However, a reaction at the GeO2/Ge interface occurs between 500 and 550 °C reducing the oxide layer to GeO x (x < 2) and containing Ge2+ and Ge+. The thickness of the oxide layer grows with the annealing temperature following an Arrhenius behavior with an activation energy of 0.82 ± 0.09 eV up to 500 °C. Remarkably, we observed simultaneous enhancement of the oxidation and crystallization of the a-Ge in the temperature interval 450 °C–500 °C, in which the oxidation rate reaches a maximum of around 0.8 nm °C−1 at around 500 °C.

Acute and chronic pain has a major impact on the individual, the family, the National Health Service and society. Acute pain is common following surgical procedures and often only partially controlled. Chronic pain currently affects around 7–8 million people in the UK, and in the USA, estimates suggest that more than 75 million people live with chronic pain.1 It is likely that the number of people with chronic pain will continue to grow as a result of increasing longevity, rising prevalence of co-morbidities such as diabetes mellitus and obesity, and improving survival rates for cancer and trauma patients. Rather than solely being a normal adaptive response following tissue injury, we now understand pain as an evolving plastic phenomenon that can be influenced by a variety of physiological, pharmacological, psychological and environmental factors. Until recently, acute and cancer pain management predominantly consisted of opioids and compassionate care.2 3 Treatment of chronic non-cancer pain may be regarded as even more of a challenge, given the complex interaction between physiological, cognitive and social factors and the need for sustainable and safe long-term management. Novel therapies and techniques, combined with our improved understanding of the pathophysiological processes of pain and the complications associated with current management strategies, offer hope to patients. In this issue, Snidvongs and Mehta provide an overview of the current guidelines and trends in opioid prescribing for chronic non-cancer pain (see page 66) .4 The rise in opioid prescriptions is highlighted and the potential implications for both the individual and society are discussed in relation to the unmet need in pain management. The latter is well documented, …

Titanium and its alloys have been employed in bone plates/screws, and these are often designed to be removed after recovery. Bone is known to bond to the surface of Ti alloys. This can lead to re-fracture of newly repaired bone during operations to remove the implants, however bone does not bond to Zr-based alloys. The inhibition of bone conduction on the surface of Zr-based alloys is thought to be due to the presence of a thin layer of zirconia (ZrO2) on the surface. The purpose of the present study was to synthesize bioinert films, including ZrO2 on pure Ti surfaces. In vitro apatite (HAp) formation and in vivo bone conduction in the tibiae of rats on the films were also investigated.Commercial purity Ti was chemically treated with aqueous H2O2/HNO3 at 353 K for 20 min. The disks were hydrothermally treated with aqueous ZrOCl2/NH3/C6H8O7 (citric acid) in an autoclave at 453 K for 12 h. Simulated body fluid (SBF) immersion test and implantation into tibiae of rats were carried out.In the hydrothermal treatment with aqueous ZrOCl2/NH3, the surface product was anatase-type TiO2. On the other hand, when citric acid was added the surface of Ti was covered homogeneously with a TiO2–ZrO2 composite film though the amount of ZrO2 was very small. HAp began to form on the non-modified Ti and TiO2 surfaces after 6 days and 4 days immersion in Hank’s solution, respectively. On the surfaces of TiO2–ZrO2, the presence of precipitates was confirmed after 6-8 days. The HAp formation was suppressed on the surfaces of TiO2–ZrO2.The present TiO2-ZrO2 surface also showed significantly lower bone-implant contact ratio in cortical bone compared with TiO2.

We introduce a new approach towards the flow control and detection of colloids in microfluidic specimens. We fabricate hybrid polydimethylsiloxane (PDMS)/glass microfluidic chips equipped with parallel micrometer and sub-micrometer channels with different width and thickness. We image and detect the colloid flow direction through the microchannels by coupling laser-light-scattering in a restricted region of a single channel. We control single polymer colloids by means of a computerized pressure-based flow control system and study the Poiseuille flow through channels with different square cross section. We demonstrate the possibility of in situ sensing populations of colloids with different dimensions down to the sub-100 nm scale.

Introduction Focused ion beam (FIB) and focused ion beam/scanning electron microscope (FIB/SEM) systems are invaluable tools for the preparation of specimens for physical and chemical analysis. Both systems are routinely used to prepare site-specific specimens for transmission electron microscopy (TEM), SEM and FIB microscopy of a wide range of materials including polymers [1], steels [2, 3], surface coatings [4, 5], catalysts [6], and semiconductors [7–11]. These systems are also used for the preparation of specimens for other analytical techniques such as Auger [12] and atom probe (AP) field ion microscopy [13]. The increase in use of FIB and FIB/SEM systems during the 1990s for the preparation of specimens for material analysis is due to the significant advantages they offer over other methods such as broad ion beam (BIB) milling, electro-polishing, or mechanical polishing. The main advantage is that the cross sections and TEM lamellae can be prepared to within 50 nm of a feature or region of interest (ROI), making it possible to analyze specific defects, phases, or interfaces. Such positional accuracy is very difficult to achieve using other sample preparation techniques. Although polishing can be used to prepare SEM cross sections to within 500 nm of a feature, this is a time consuming process in which the sample has to be repeatedly imaged (either using an optical microscope or an SEM) to ensure the feature is not polished through.

Interventional neuroradiology is relatively safe in most of its applications. However, there is some risk of producing new neurological deficits. These may result from the unintentional occlusion of arterial branches to functional nervous tissue or haemorrhage, either from vessel penetration during the procedure itself or associated with disturbances of regional cerebral haemodynamics.

A novel and simple approach for the realization of polymer sub-micrometre channels is introduced by exploiting replica molding of Pt wires deposited by focused ion beam. We fabricate arrays of parallel channels with typical dimensions down to 600 nm and with variable height. We characterize the pressure-driven transport of polymer colloids through the channels in terms of the translocation frequency, amplitude and duration by implementing a laser scattering detection technique. We propose a prototype application of the presented platform such as the in situ sizing and sensing of populations of particles with different dimensions down to 50 nm.

Areally extensive erosion surfaces in eolian deposits have been interpreted as long hiatuses in eolian deposition. Such erosion surfaces form during deflationary episodes or during periods of erg stabilization or contraction. They are called "super surfaces" and can be useful for stratigraphic correlation because of their regional extent. The Permian Cedar Mesa Sandstone and Cutler Formation contain a type off super surface (herein termed "flood surfaces"), ∼10-400+ km2. Flood surfaces form as a result of fluvial floods into active dune seas. The surfaces may expand through nonclimbing migration of eolian dunes but do not imply long hiatuses in eolian deposition as do other types of super surfaces. Cutler and Cedar Mesa flood surfaces are overlain by shales and sandstones which thicken laterally and merge with fluvial channel-fill deposits. Flooding of active dune fields in the Cedar Mesa Sandstone is suggested by intertonguing of eolian dune and fluvial deposits. Flood surfaces can easily be mistaken for deflationary super surfaces but are distinguished by evidence of dune migration coincident with flood events and by an increase in the number of surfaces adjacent to associated aqueous deposits.

Five experiments studied practice effects for 4, 7, 11 subjects on visual backward masking using a signal-detection procedure under various conditions. Exp. I determined the minimum perceptible critical stimulus duration (CSD) for criterion identification of a target stimulus, the letter T or A. In Exp. II, the stimulus was presented at the critical stimulus duration (CSD) followed by a pattern mask at intervals of 20 to 120 msec. for 15 separate sessions. In Exp. III (N = 4) the mask followed the CSD in intervals of 2-msec. increments until subjects reached criterion accuracy. Exps. IV and V (Ns = 4, 7) provided partial replications of Exps. II and III. Naive subjects were used, and the stimulus duration was constant for all subjects. When masking functions were obtained at a threshold, considerable variability was found and subjects improve slowly or not at all over sessions. With a fixed supra-threshold stimulus, all subjects improve with practice. The inportance of these findings is discussed as they relate to common (and largely untested) assumptions made in the backward masking and perception literature.

Medano Creek in Colorado provides a unique opportunity to study upper-flow-regime deposition. It is a steep, aggrading fluvial system in which antidunes are the dominant bedform. Medano Creek is a straight, single-channel stream where flow is largely confined to a sequence of upstream-migrating topographic steps (pools and riffles), a stable channel geometry. Antidunes and upperflow-regime plane beds are arranged in an organized pattern on the surface of pool and riffle sequences as a response to spatially varied flow conditions. In the creek, antidunes form sedimentary structures consisting of low-angle backset and foreset beds and subhorizontal laminae grouped into lenses. Laminae in a lens are often subparallel to the lens-bounding surfaces on the downcurrent end and are truncated y the upper bounding surface on the upcurrent end. Upper-flow-regime plane bed and rhomboid ripples produce planar laminae. Through lateral shifting of the active channel and upstream migration of pools and riffles, Medano Creek produces a facies sequence consisting of alternating 10-40-cm-thick layers of (planar) laminae and low-angle, cross-stratified, lenticular bedding.

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