Differential Cognitive Effects of Unilateral Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease.

OBJECTIVE: The aim of this study was to investigate the cognitive effects of unilateral directional versus ring subthalamic nucleus deep brain stimulation (STN DBS) in patients with advanced Parkinson's disease. METHODS: We examined 31 participants who underwent unilateral STN DBS (left n = 17; right n = 14) as part of an National Institutes of Health (NIH)-sponsored randomized, double-blind, crossover study contrasting directional versus ring stimulation. All participants received unilateral DBS implants in the hemisphere more severely affected by motor parkinsonism. Measures of cognition included verbal fluency, auditory-verbal memory, and response inhibition. We used mixed linear models to contrast the effects of directional versus ring stimulation and implant hemisphere on longitudinal cognitive function. RESULTS: Crossover analyses showed no evidence for group-level changes in cognitive performance related to directional versus ring stimulation. Implant hemisphere, however, impacted cognition in several ways. Left STN participants had lower baseline verbal fluency than patients with right implants (t [20.66 = -2.50, p = 0.02]). Verbal fluency declined after left (p = 0.013) but increased after right STN DBS (p < 0.001), and response inhibition was faster following right STN DBS (p = 0.031). Regardless of hemisphere, delayed recall declined modestly over time versus baseline (p = 0.001), and immediate recall was unchanged. INTERPRETATION: Directional versus ring STN DBS did not differentially affect cognition. Similar to prior bilateral DBS studies, unilateral left stimulation worsened verbal fluency performance. In contrast, unilateral right STN surgery increased performance on verbal fluency and response inhibition tasks. Our findings raise the hypothesis that unilateral right STN DBS in selected patients with predominant right brain motor parkinsonism could mitigate declines in verbal fluency associated with the bilateral intervention. ANN NEUROL 2024;95:1205-1219.

The Benefit of an Umbrella Protocol: Reducing Challenges in Orthopedic Oncology Research.

Background: Orthopedic oncology research is hindered by the scarcity of musculoskeletal tumors and research administrative inefficiencies. This paper introduces observational research through an innovative institution-specific methodology-termed an umbrella protocol. This protocol outlines a comprehensive standard procedure to expedite ethical approval for future aligned studies, reducing administrative barriers to research. Methods: We developed an umbrella protocol at an academic center, involving meticulous methodological identification and coordination with the institutional review board (IRB) to adhere to local guidelines. The protocol encompasses identifying investigators, research objectives, study goals, and data and safety monitoring frameworks necessary for typical standards. Results: Implementation of the umbrella protocol took 110 days to achieve exemption status, following multiple discussions with the IRB and extensive revisions. At the authors institution, this protocol significantly reduces protocol review times from an average of six-to-eight weeks to nearly instantaneous, facilitating a streamlined research process. Additionally, we established a dedicated orthopedic oncology patient registry to enhance future research endeavors. Conclusions: The adoption of umbrella protocols represents a pioneering strategy in orthopedic oncology. This approach mitigates research administrative burdens and broadens research scope in the field. It underscores the necessity of IRB collaboration, methodological precision, and stringent data management. The article also reflects on the ethical implications and potential biases introduced by emerging technologies like artificial intelligence, advocating for diligent ethical oversight. The establishment of an umbrella protocol marks a significant step towards more efficient research methodologies, ultimately aiming to improve patient care and outcomes for individuals with rare musculoskeletal conditions.

Thermally stable Peltier controlled vacuum chamber for electrical transport measurements.

The design, manufacture, and characterization of an inexpensive, temperature-controlled vacuum chamber with millikelvin stability for electrical transport measurements at and near room temperature is reported. A commercially available Peltier device and a high-precision temperature controller are used to actively heat and cool the sample space. The system was designed to minimize thermal fluctuations in spintronic and semiconductor transport measurements, but the general principle is relevant to a wide range of electrical measurement applications. The main issues overcome are the mounting of a sample with a path of high thermal conductivity through to the Peltier device and the heat sinking of the said Peltier device inside a vacuum. A copper slug is used as the mount for a sample, and a large copper block is used as a thermal feedthrough before a passive heat sink is used to cool this block. The Peltier device provides 20 W of heating and cooling power, achieving a maximum range of 30 K below and 40 K above the ambient temperature. The temperature stability is within 5 mK at all set points with an even better performance above the ambient temperature. A vacuum pressure of 10-8 hPa is achievable. As a demonstration, we present experimental results from current-induced electrical switching of a CuMnAs thin film. Transport measurements with and without the Peltier control emphasize the importance of a constant temperature in these applications. The thermal lag between the sample space measurement and the sample itself is observed through magnetoresistance values measured during a temperature sweep.

Where do the hypotheses come from? Data-driven learning in science and the brain.

Everyone agrees that testing hypotheses is important, but Bowers et al. provide scant details about where hypotheses about perception and brain function should come from. We suggest that the answer lies in considering how information about the outside world could be acquired - that is, learned - over the course of evolution and development. Deep neural networks (DNNs) provide one tool to address this question.

Coccidioidomycosis Osteoarticular Dissemination.

Valley fever or coccidioidomycosis is a pulmonary infection caused by species of Coccidioides fungi that are endemic to California and Arizona. Skeletal coccidioidomycosis accounts for about half of disseminated infections, with the vertebral spine being the preferred site of dissemination. Most cases of skeletal coccidioidomycosis progress to bone destruction or spread to adjacent structures such as joints, tendons, and other soft tissues, causing significant pain and restricting mobility. Manifestations of such cases are usually nonspecific, making diagnosis very challenging, especially in non-endemic areas. The lack of basic knowledge and research data on the mechanisms defining susceptibility to extrapulmonary infection, especially when it involves bones and joints, prompted us to survey available clinical and animal data to establish specific research questions that remain to be investigated. In this review, we explore published literature reviews, case reports, and case series on the dissemination of coccidioidomycosis to bones and/or joints. We highlight key differential features with other conditions and opportunities for mechanistic and basic research studies that can help develop novel diagnostic, prognostic, and treatment strategies.

Illusory optical defocus generated by shaded surface texture.

The human visual system is tasked with the problem of extracting information about the world from images that contain a conflated mixture of environmental sources and optical artifacts generated by the focal properties of our eyes. In most contexts, our brains manage to distinguish these sources, but this is not always the case. Recent work showed that shading gradients generated by smooth three-dimensional (3D) surfaces can elicit strong illusory percepts of optical defocus1,2 - the perception of illusory blur is only eliminated when the surface appears attached to self-occluding contours3, surface discontinuities1, or sharp specular reflections1,2, which all generate sharp ('high spatial frequency') image structure. This suggests that it should also be possible to eliminate the illusory blur elicited by shaded surfaces by altering the surface geometry to include small-scale surface relief, which would also generate high-frequency image structure. We report the surprising result here that this manipulation fails to eliminate the perception of blur; the fine texture fails to perceptually 'bind' to the low-frequency image structure when there is a sufficient gap between the spatial scales of the fine and coarse surface structure. These findings suggest that discontinuous 'gaps' in the spatial scale of textures are a segmentation cue the visual system uses to extract multiple causes of image structure.

Association of Parity and Previous Birth Outcome With Brachial Plexus Birth Injury Risk.

OBJECTIVE: To evaluate the association of maternal delivery history with a brachial plexus birth injury risk in subsequent deliveries and to estimate the effect of subsequent delivery method on brachial plexus birth injury risk. METHODS: We conducted a retrospective cohort study of all live-birth deliveries occurring in California-licensed hospitals from 1996 to 2012. The primary outcome was recurrent brachial plexus birth injury in a subsequent pregnancy. The exposure was delivery history (parity, shoulder dystocia in a previous delivery, or previously delivering a neonate with brachial plexus birth injury). Multiple logistic regression was used to model adjusted associations of delivery history with brachial plexus birth injury in a subsequent pregnancy. The adjusted risk and adjusted risk difference for brachial plexus birth injury between vaginal and cesarean deliveries in subsequent pregnancies were determined, stratified by delivery history, and the number of cesarean deliveries needed to prevent one brachial plexus birth injury was determined. RESULTS: Of 6,286,324 neonates delivered by 4,104,825 individuals, 7,762 (0.12%) were diagnosed with a brachial plexus birth injury. Higher parity was associated with a 5.7% decrease in brachial plexus birth injury risk with each subsequent delivery (adjusted odds ratio [aOR] 0.94, 95% CI 0.92-0.97). Shoulder dystocia or brachial plexus birth injury in a previous delivery was associated with fivefold (0.58% vs 0.11%, aOR 5.39, 95% CI 4.10-7.08) and 17-fold (1.58% vs 0.11%, aOR 17.22, 95% CI 13.31-22.27) increases in brachial plexus birth injury risk, respectively. Among individuals with a history of delivering a neonate with a brachial plexus birth injury, cesarean delivery was associated with a 73.0% decrease in brachial plexus birth injury risk (0.60% vs 2.21%, aOR 0.27, 95% CI 0.13-0.55) compared with an 87.9% decrease in brachial plexus birth injury risk (0.02% vs 0.15%, aOR 0.12, 95% CI 0.10-0.15) in individuals without this history. Among individuals with a history of brachial plexus birth injury, 48.1 cesarean deliveries are needed to prevent one brachial plexus birth injury. CONCLUSIONS: Parity, previous shoulder dystocia, and previously delivering a neonate with brachial plexus birth injury are associated with future brachial plexus birth injury risk. These factors are identifiable prenatally and can inform discussions with pregnant individuals regarding brachial plexus birth injury risk and planned mode of delivery.

Impact of COVID-19 pandemic on pharmacologic treatment of patients newly diagnosed with osteoporosis.

PURPOSE: This study determined whether initiation of pharmacologic treatment was delayed for newly diagnosed osteoporosis patients during the COVID-19 pandemic. METHODS: 1,189 patients ≥50 years with newly diagnosed osteoporosis using dual-energy x-ray absorptiometry (DXA) screening at a single academic institution were included. Patients with previous osteoporosis were excluded. Patients diagnosed between March 1, 2018-January 31, 2020 (pre-pandemic cohort, n = 576) were compared to those diagnosed between March 1, 2020-January 31, 2022 (pandemic cohort, n = 613). Age, sex, race, ethnicity, ordering providers (primary vs specialty), and pharmacological agents were evaluated. Primary outcomes included proportion of patients prescribed therapy within 3 and 6-months of diagnosis, and mean time from diagnosis to treatment initiation. RESULTS: The pre-pandemic cohort had more White patients (74.3 vs 68.4%, p = .02) and no differences between remaining demographic variables. Only 40.5% of newly diagnosed patients initiated pharmacologic therapy within 6 months. Patients treated at 3-months (31.8 vs 35.4%, p = 0.19) and 6-months (37.8 vs 42.9, p = 0.08) were comparable between cohorts (47.2 vs 50.2% p = 0.30). Mean time from diagnosis to treatment initiation was similar (46 vs 45 days, p = 0.72). There were no treatment differences based on gender, race, or ethnicity or between ordering providers (65.1 vs 57.4% primary care, p = 0.08). Bisphosphonates were most often prescribed in both cohorts (89% vs 82.1%). CONCLUSIONS: This is the first study assessing COVID-19's impact on pharmacologic treatment of newly diagnosed osteoporosis. 40.5% of newly diagnosed patients were treated pharmacologically within six months of diagnosis, and the pandemic did not significantly affect treatment rates.

The role of self-occluding contours in material perception.

The human visual system extracts both the three-dimensional (3D) shape and the material properties of surfaces from single images.1,2,3,4,5,6,7,8,9,10,11,12,13,14 Understanding this remarkable ability is difficult because the problem of extracting both shape and material is formally ill posed: information about one appears to be needed to recover the other.14,15,16,17 Recent work has suggested that a particular class of image contours formed by a surface curving smoothly out of sight (self-occluding contours) contains information that co-specifies both surface shape and material for opaque surfaces.18 However, many natural materials are light permeable (translucent); it is unknown whether there is information along self-occluding contours that can be used to distinguish opaque and translucent materials. Here, we present physical simulations, which demonstrate that variations in intensity generated by opaque and translucent materials are linked to different shape attributes of self-occluding contours. Psychophysical experiments demonstrate that the human visual system exploits the different forms of intensity-shape covariation along self-occluding contours to distinguish opaque and translucent materials. These results provide insight into how the visual system manages to solve the putatively ill-posed problem of extracting both the shape and material properties of 3D surfaces from images.

Antiferromagnetic half-skyrmions electrically generated and controlled at room temperature.

Topologically protected magnetic textures are promising candidates for information carriers in future memory devices, as they can be efficiently propelled at very high velocities using current-induced spin torques. These textures-nanoscale whirls in the magnetic order-include skyrmions, half-skyrmions (merons) and their antiparticles. Antiferromagnets have been shown to host versions of these textures that have high potential for terahertz dynamics, deflection-free motion and improved size scaling due to the absence of stray field. Here we show that topological spin textures, merons and antimerons, can be generated at room temperature and reversibly moved using electrical pulses in thin-film CuMnAs, a semimetallic antiferromagnet that is a testbed system for spintronic applications. The merons and antimerons are localized on 180° domain walls, and move in the direction of the current pulses. The electrical generation and manipulation of antiferromagnetic merons is a crucial step towards realizing the full potential of antiferromagnetic thin films as active components in high-density, high-speed magnetic memory devices.

Maternal Epidemiology of Brachial Plexus Birth Injuries in California: 1996 to 2012.

OBJECTIVE: This study aimed to evaluate the incidence of brachial plexus birth injury (BPBI) and its associations with maternal demographic factors. Additionally, we sought to determine whether longitudinal changes in BPBI incidence differed by maternal demographics. STUDY DESIGN: We conducted a retrospective cohort study of over 8 million maternal-infant pairs using California's Office of Statewide Health Planning and Development Linked Birth Files from 1991 to 2012. Descriptive statistics were used to determine BPBI incidence and the prevalence of maternal demographic factors (race, ethnicity, age). Multivariable logistic regression was used to determine associations of year, maternal race, ethnicity, and age with BPBI. Excess population-level risk associated with these characteristics was determined by calculating population attributable fractions. RESULTS: The incidence of BPBI between 1991 and 2012 was 1.28 per 1,000 live births, with peak incidence of 1.84 per 1,000 in 1998 and low of 0.9 per 1,000 in 2008. Incidence varied by demographic group, with infants of Black (1.78 per 1,000) and Hispanic (1.34 per 1,000) mothers having higher incidences compared with White (1.25 per 1,000), Asian (0.8 per 1,000), Native American (1.29 per 1,000), other race (1.35 per 1,000), and non-Hispanic (1.15 per 1,000) mothers. After controlling for delivery method, macrosomia, shoulder dystocia, and year, infants of Black (adjusted odds ratio [AOR] = 1.88, 95% confidence interval [CI] = 1.70, 2.08), Hispanic (AOR = 1.25, 95% CI = 1.18, 1.32), and advanced-age mothers (AOR = 1.16, 95% CI = 1.09, 1.25) were at increased risk. Disparities in risk experienced by Black, Hispanic, and advanced-age mothers contributed to a 5, 10, and 2% excess risk at the population level, respectively. Longitudinal trends in incidence did not vary among demographic groups. Population-level changes in maternal demographics did not explain changes in incidence over time. CONCLUSION: Although BPBI incidence has decreased in California, demographic disparities exist. Infants of Black, Hispanic, and advanced-age mothers are at increased BPBI risk compared with White, non-Hispanic, and younger mothers. KEY POINTS: · The incidence of BPBI has decreased over time.. · Demographic disparities in BPBI incidence and risk exist.. · Infants of Black, Hispanic, and advanced age mothers are at greatest risk of BPBI..

Differential cognitive effects of unilateral left and right subthalamic nucleus deep brain stimulation for Parkinson disease.

Objective: To investigate hemispheric effects of directional versus ring subthalamic nucleus (STN) deep brain stimulation (DBS) surgery on cognitive function in patients with advanced Parkinson's disease (PD). Methods: We examined 31 PD patients (Left STN n = 17; Right STN n = 14) who underwent unilateral subthalamic nucleus (STN) DBS as part of a NIH-sponsored randomized, cross-over, double-blind (ring vs directional) clinical trial. Outcome measures were tests of verbal fluency, auditory-verbal memory, and response inhibition. First, all participants were pooled together to study the effects of directional versus ring stimulation. Then, we stratified the groups by surgery hemisphere and studied the longitudinal changes in cognition post-unilateral STN DBS. Results: Relative to pre-DBS cognitive baseline performances, there were no group changes in cognition following unilateral DBS for either directional or ring stimulation. However, assessment of unilateral DBS by hemisphere revealed a different pattern. The left STN DBS group had lower verbal fluency than the right STN group (t(20.66 = -2.50, p = 0.02). Over a period of eight months post-DBS, verbal fluency declined in the left STN DBS group (p = 0.013) and improved in the right STN DBS group over time (p < .001). Similarly, response inhibition improved following right STN DBS (p = 0.031). Immediate recall did not significantly differ over time, nor was it affected by implant hemisphere, but delayed recall equivalently declined over time for both left and right STN DBS groups (left STN DBS p = 0.001, right STN DBS differ from left STN DBS p = 0.794). Conclusions: Directional and ring DBS did not differentially or adversely affect cognition over time. Regarding hemisphere effects, verbal fluency decline was observed in those who received left STN DBS, along with the left and right STN DBS declines in delayed memory. The left STN DBS verbal fluency decrement is consistent with prior bilateral DBS research, likely reflecting disruption of the basal-ganglia-thalamocortical network connecting STN and inferior frontal gyrus. Interestingly, we found an improvement in verbal fluency and response inhibition following right STN DBS. It is possible that unilateral STN DBS, particularly in the right hemisphere, may mitigate cognitive decline.

First Organoid Intelligence (OI) workshop to form an OI community.

The brain is arguably the most powerful computation system known. It is extremely efficient in processing large amounts of information and can discern signals from noise, adapt, and filter faulty information all while running on only 20 watts of power. The human brain's processing efficiency, progressive learning, and plasticity are unmatched by any computer system. Recent advances in stem cell technology have elevated the field of cell culture to higher levels of complexity, such as the development of three-dimensional (3D) brain organoids that recapitulate human brain functionality better than traditional monolayer cell systems. Organoid Intelligence (OI) aims to harness the innate biological capabilities of brain organoids for biocomputing and synthetic intelligence by interfacing them with computer technology. With the latest strides in stem cell technology, bioengineering, and machine learning, we can explore the ability of brain organoids to compute, and store given information (input), execute a task (output), and study how this affects the structural and functional connections in the organoids themselves. Furthermore, understanding how learning generates and changes patterns of connectivity in organoids can shed light on the early stages of cognition in the human brain. Investigating and understanding these concepts is an enormous, multidisciplinary endeavor that necessitates the engagement of both the scientific community and the public. Thus, on Feb 22-24 of 2022, the Johns Hopkins University held the first Organoid Intelligence Workshop to form an OI Community and to lay out the groundwork for the establishment of OI as a new scientific discipline. The potential of OI to revolutionize computing, neurological research, and drug development was discussed, along with a vision and roadmap for its development over the coming decade.

Chondrocalcinosis and Osteoarthritis: A Literature Review.

OBJECTIVE: The objective of this study was to review the literature on associations between chondrocalcinosis (CC) and osteoarthritis (OA) and to examine the role of colchicine, previously established as effective for calcium pyrophosphate deposition disease, in the treatment of OA. METHODS: A literature search for mechanistic and clinical studies published between 1990 and 2021 listed in PubMed was performed and studies were included if they examined the associations between OA and CC or colchicine using relevant search terms. RESULTS: Published evidence suggests significant radiographic and mechanistic associations between knee OA and knee CC, but there are only a limited number of studies demonstrating associations between OA and CC in the hips, hands, and ankles. We examined three studies testing the efficacy of colchicine on treatment of pain in OA and found insufficient evidence to definitively establish that colchicine is effective to ameliorate symptoms of OA, although differences in study methodologies and inclusion criteria may explain inconsistent study findings. CONCLUSION: An association between CC and OA is supported at the knee joint in both radiographic and in-vitro studies, but is less definite when the relationship is evaluated at other joints, including at the hips, hands, and ankles. Further research is required to ascertain whether CC modifies symptoms in patients with osteoarthritis or is associated with OA progression. It may be worthwhile to further evaluate colchicine or other agents for potential symptom modifying roles in OA or in OA with CC.

Macular Findings of Patients on Pentosan Polysulfate Sodium.

INTRODUCTION: In 2018, a unique maculopathy associated with chronic pentosan polysulfate sodium (PPS) use for the treatment of interstitial cystitis (IC) was described, where the authors detailed macular retinal pigment epithelial abnormalities in six patients. In this paper, a retrospective study of a larger patient pool at one large tertiary retina practice was undertaken to evaluate patients taking PPS and their macular findings. MATERIALS AND METHODS: A retrospective chart review was performed on all patients presenting to a single large retina practice between 2011 and 2019. Patient's macular diagnosis, findings, optical coherence tomography scans, and macular auto-fluorescent scans were assessed. This project was Institutional Review Board (IRB) approved by the St Luke's Hospital IRB board (St Louis, MO, USA). RESULTS: Fifty-five patients were identified as taking PPS for IC. Fifty-three patients were found to have a diagnosis consistent with changes attributable to known macular diseases to include macular degeneration and pattern dystrophies. Two (4%) of fifty-five patients had macular findings suggestive of PPS toxicity. The first was a 58-year-old female with subtle retinal pigment epithelium (RPE) deposits on optical coherence tomography that exhibited hyper-autofluorescence. The second was a 72-year-old female with 14 years of PPS use who exhibited RPE excrescences and parafoveal areas of atrophy. CONCLUSIONS: Pentosan polysulfate sodium may be the cause of macular findings in a small percentage of patients referred to a tertiary retina practice. Although causation of macular changes with PPS use has yet to be elucidated, clinicians should be aware of this possibility when assessing patients with atypical macular findings. Future longitudinal studies are necessary to evaluate a definitive relationship. This paper should remind all clinicians of the importance of a throughout review of the patient's medication list as novel toxicities may become apparent years after initial FDA trials. The strength of this study is the larger patient population compared to earlier studies, and the main weaknesses include the retrospective nature of the study, lack of family and genetic testing, and lack of multimodal imaging for all patients.

Perceiving the shape and material properties of 3D surfaces.

Our visual experience of the world relies on the interaction of light with the different substances, surfaces, and objects in our environment. These optical interactions generate images that contain a conflated mixture of different scene variables, which our visual system must somehow disentangle to extract information about the shape and material properties of the world. Such problems have historically been considered to be ill-posed, but recent work suggests that there are complex patterns of covariation in light that co-specify the 3D shape and material properties of surfaces. This work provides new insights into how the visual system acquired the ability to solve problems that have historically been considered intractable.

Socioeconomic and insurance-related disparities in disease-specific survival among patients with metastatic bone disease.

BACKGROUND: Approximately 5% of cancer patients in the United States presented with metastatic bone disease (MBD) at diagnosis. Current study explores the disparities in survival for patients with MBD. METHODS: Patients with the diagnosis of MBD at presentation for the five most common primary anatomical sites were extracted from Surveillance, Epidemiology, and End Results Census tract-level dataset (2010-2016). Kaplan-Meier and Cox Proportional Hazard models were used to evaluate survival, and prognostic factors for each cohort. Prognostic significance of socioeconomic status (SES) and insurance status were ascertained. RESULTS: The five most common anatomical-sites with MBD at presentation included "lung" (n = 59 739), "prostate" (n = 19 732), "breast" (n = 16 244), "renal and urothelium" (n = 7718) and "colon" (n= 3068). Lower SES was an independent risk factor for worse disease-specific survival (DSS) for patients with MBD originating from lung, prostate, breast and colon. Lack of insurance was an independent risk factor for worse DSS for MBD patients with primary tumors in lung and breast. CONCLUSIONS: MBD patients from the five most common primary sites demonstrated SES and insurance-related disparities in disease-specific survival. This is the first and largest study to explore SES and insurance-related disparities among patients specifically afflicted with MBD. Our findings highlight vulnerability of patients with MBD across multiple primary sites to financial toxicity.

Seasonal dynamics of ammonia-oxidizing bacteria but not archaea influence soil nitrogen cycling in a semi-arid agricultural soil.

Nitrification, a key pathway of nitrogen (N) loss from agricultural soils, is performed by ammonia-oxidizing bacteria (AOB) and archaea (AOA). We examined the seasonal dynamics (2 years) of ammonia oxidizer gene abundances across a gradient of soil carbon (C) and N in a semi-arid soil after 8 years of tillage and crop residue treatments. AOB was more dominant than AOA in the surface soil, as AOA were undetected in 96% of samples. Seasonal variation in AOB abundance was related to substrate availability; AOB gene copy numbers increased at the end of the growing season (during summer fallow) following higher concentrations in dissolved organic matter soil water. This suggests increased co-location between AOB and substrate resources in pores still filled with water as the soils dried. AOB was however not statistically related to soil ammonium concentrations, soil water content, rainfall or temperature. Organic matter inputs enhanced AOB abundance independent of seasonal variation. AOB abundance was greatest in autumn and immediately preceding the start of the growing season, and coincided with elevated soil nitrate concentrations. The growth of the AOB population is likely to contribute to increased risk of N loss through leaching and/or denitrification at the start of the crop growing season following summer fallow.

The role of color in the perception of three-dimensional shape.

The human visual system can derive information about three-dimensional (3D) shape from the structure of light reflected by surfaces. Most research on single static images has focused on the 3D shape information contained in variations of brightness caused by interactions between the illumination and local surface orientation ("shading").1-6 Although color can enhance the recovery of surface shading when color and brightness vary independently,7-9 there is no evidence that color alone provides any information about 3D shape. Here, we show that the wavelength-dependent reflectance of chromatic materials provides information about the 3D shape of translucent materials. We show that different wavelengths of light undergo varying degrees of subsurface light transport, which generates multiple forms of spatial structure: wavelengths that are weakly reflected generate shading-like image structure, linked to 3D surface orientation, whereas wavelengths that penetrate more deeply into the material are primarily constrained by the direction of surface curvature (convexities and concavities).10 Psychophysical experiments demonstrate that the enhanced perception of 3D shape in chromatic translucent surfaces arises from the shading structure generated by weakly reflected wavelengths, which, in turn, generates correlated spatial variations in saturation. These results demonstrate a new functional role for color in the perception of the 3D shape of translucent materials.