High-Capacity, Cooperative CO2 Capture in a Diamine-Appended Metal-Organic Framework through a Combined Chemisorptive and Physisorptive Mechanism.

Diamine-appended Mg2(dobpdc) (dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) metal-organic frameworks are promising candidates for carbon capture that exhibit exceptional selectivities and high capacities for CO2. To date, CO2 uptake in these materials has been shown to occur predominantly via a chemisorption mechanism involving CO2 insertion at the amine-appended metal sites, a mechanism that limits the capacity of the material to ∼1 equiv of CO2 per diamine. Herein, we report a new framework, pip2-Mg2(dobpdc) (pip2 = 1-(2-aminoethyl)piperidine), that exhibits two-step CO2 uptake and achieves an unusually high CO2 capacity approaching 1.5 CO2 per diamine at saturation. Analysis of variable-pressure CO2 uptake in the material using solid-state nuclear magnetic resonance (NMR) spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveals that pip2-Mg2(dobpdc) captures CO2 via an unprecedented mechanism involving the initial insertion of CO2 to form ammonium carbamate chains at half of the sites in the material, followed by tandem cooperative chemisorption and physisorption. Powder X-ray diffraction analysis, supported by van der Waals-corrected density functional theory, reveals that physisorbed CO2 occupies a pocket formed by adjacent ammonium carbamate chains and the linker. Based on breakthrough and extended cycling experiments, pip2-Mg2(dobpdc) exhibits exceptional performance for CO2 capture under conditions relevant to the separation of CO2 from landfill gas. More broadly, these results highlight new opportunities for the fundamental design of diamine-Mg2(dobpdc) materials with even higher capacities than those predicted based on CO2 chemisorption alone.

Selective Adsorption of Oxygen from Humid Air in a Metal-Organic Framework with Trigonal Pyramidal Copper(I) Sites.

High or enriched-purity O2 is used in numerous industries and is predominantly produced from the cryogenic distillation of air, an extremely capital- and energy-intensive process. There is significant interest in the development of new approaches for O2-selective air separations, including the use of metal-organic frameworks featuring coordinatively unsaturated metal sites that can selectively bind O2 over N2 via electron transfer. However, most of these materials exhibit appreciable and/or reversible O2 uptake only at low temperatures, and their open metal sites are also potential strong binding sites for the water present in air. Here, we study the framework CuI-MFU-4l (CuxZn5-xCl4-x(btdd)3; H2btdd = bis(1H-1,2,3-triazolo[4,5-b],[4',5'-i])dibenzo[1,4]dioxin), which binds O2 reversibly at ambient temperature. We develop an optimized synthesis for the material to access a high density of trigonal pyramidal CuI sites, and we show that this material reversibly captures O2 from air at 25 °C, even in the presence of water. When exposed to air up to 100% relative humidity, CuI-MFU-4l retains a constant O2 capacity over the course of repeated cycling under dynamic breakthrough conditions. While this material simultaneously adsorbs N2, differences in O2 and N2 desorption kinetics allow for the isolation of high-purity O2 (>99%) under relatively mild regeneration conditions. Spectroscopic, magnetic, and computational analyses reveal that O2 binds to the copper(I) sites to form copper(II)-superoxide moieties that exhibit temperature-dependent side-on and end-on binding modes. Overall, these results suggest that CuI-MFU-4l is a promising material for the separation of O2 from ambient air, even without dehumidification.

Cu(II) Promoted C(sp3 )-H Activation in Unactivated Cycloalkanes: Oxo-Alkylation of Styrenes to Synthesize ß-Disubstituted Ketones.

We report the Cu(II) catalyzed synthesis of ß-disubstituted ketones from styrene via oxo-alkylation with unactivated cycloalkanes as the alkylating agent in presence of tert-butylhydroperoxide (TBHP) and 1-methylimidazole as oxidant and base respectively. ß-disubstituted ketones are known to be synthesized by using either expensive Ru/Ir complexes, or low-cost metal complexes (e. g., Fe, Mn) with activated species like aldehyde, acid, alcohol, or phthalimide derivatives as the alkylating agent, however, use of unactivated cycloalkanes directly as the alkylating agent remains challenging. A wide range of aliphatic C-H substrates as well as various olefinic arenes and heteroarene (35 substrates including 14 new substrates) are well-tolerated in this method. Hammett analysis shed more light on the substitution effect in the olefinic part on the overall mechanism. Furthermore, the controlled experiments, kinetic isotope effect study, and theoretical calculations (DFT) enable us to gain deeper insight of mechanistic intricacies of this new simple and atom-economic methodology.

Cooperative Carbon Dioxide Capture in Diamine-Appended Magnesium-Olsalazine Frameworks.

Diamine-appended Mg2(dobpdc) (dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) metal-organic frameworks have emerged as promising candidates for carbon capture owing to their exceptional CO2 selectivities, high separation capacities, and step-shaped adsorption profiles, which arise from a unique cooperative adsorption mechanism resulting in the formation of ammonium carbamate chains. Materials appended with primary,secondary-diamines featuring bulky substituents, in particular, exhibit excellent stabilities and CO2 adsorption properties. However, these frameworks display double-step adsorption behavior arising from steric repulsion between ammonium carbamates, which ultimately results in increased regeneration energies. Herein, we report frameworks of the type diamine-Mg2(olz) (olz4- = (E)-5,5'-(diazene-1,2-diyl)bis(2-oxidobenzoate)) that feature diverse diamines with bulky substituents and display desirable single-step CO2 adsorption across a wide range of pressures and temperatures. Analysis of CO2 adsorption data reveals that the basicity of the pore-dwelling amine─in addition to its steric bulk─is an important factor influencing adsorption step pressure; furthermore, the amine steric bulk is found to be inversely correlated with the degree of cooperativity in CO2 uptake. One material, ee-2-Mg2(olz) (ee-2 = N,N-diethylethylenediamine), adsorbs >90% of the CO2 from a simulated coal flue stream and exhibits exceptional thermal and oxidative stability over the course of extensive adsorption/desorption cycling, placing it among top-performing adsorbents to date for CO2 capture from a coal flue gas. Spectroscopic characterization and van der Waals-corrected density functional theory calculations indicate that diamine-Mg2(olz) materials capture CO2 via the formation of ammonium carbamate chains. These results point more broadly to the opportunity for fundamentally advancing materials in this class through judicious design.

Evaluation of the Stability of Diamine-Appended Mg2(dobpdc) Frameworks to Sulfur Dioxide.

Diamine-appended Mg2(dobpdc) (dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) metal-organic frameworks are a promising class of CO2 adsorbents, although their stability to SO2─a trace component of industrially relevant exhaust streams─remains largely untested. Here, we investigate the impact of SO2 on the stability and CO2 capture performance of dmpn-Mg2(dobpdc) (dmpn = 2,2-dimethyl-1,3-propanediamine), a candidate material for carbon capture from coal flue gas. Using SO2 breakthrough experiments and CO2 isobar measurements, we find that the material retains 91% of its CO2 capacity after saturation with a wet simulated flue gas containing representative levels of CO2 and SO2, highlighting the robustness of this framework to SO2 under realistic CO2 capture conditions. Initial SO2 cycling experiments suggest dmpn-Mg2(dobpdc) may achieve a stable operating capacity in the presence of SO2 after initial passivation. Evaluation of several other diamine-Mg2(dobpdc) variants reveals that those with primary,primary (1°,1°) diamines, including dmpn-Mg2(dobpdc), are more robust to humid SO2 than those featuring primary,secondary (1°,2°) or primary,tertiary (1°,3°) diamines. Based on the solid-state 15N NMR spectra and density functional theory calculations, we find that under humid conditions, SO2 reacts with the metal-bound primary amine in 1°,2° and 1°,3° diamine-appended Mg2(dobpdc) to form a metal-bound bisulfite species that is charge balanced by a primary ammonium cation, thereby facilitating material degradation. In contrast, humid SO2 reacts with the free end of 1°,1° diamines to form ammonium bisulfite, leaving the metal-diamine bond intact. This structure-property relationship can be used to guide further optimization of these materials for CO2 capture applications.

Overcoming Metastable CO2 Adsorption in a Bulky Diamine-Appended Metal-Organic Framework.

Carbon capture at fossil fuel-fired power plants is a critical strategy to mitigate anthropogenic contributions to global warming, but widespread deployment of this technology is hindered by a lack of energy-efficient materials that can be optimized for CO2 capture from a specific flue gas. As a result of their tunable, step-shaped CO2 adsorption profiles, diamine-functionalized metal-organic frameworks (MOFs) of the form diamine-Mg2(dobpdc) (dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) are among the most promising materials for carbon capture applications. Here, we present a detailed investigation of dmen-Mg2(dobpdc) (dmen = 1,2-diamino-2-methylpropane), one of only two MOFs with an adsorption step near the optimal pressure for CO2 capture from coal flue gas. While prior characterization suggested that this material only adsorbs CO2 to half capacity (0.5 CO2 per diamine) at 1 bar, we show that the half-capacity state is actually a metastable intermediate. Under appropriate conditions, the MOF adsorbs CO2 to full capacity, but conversion from the half-capacity structure happens on a very slow time scale, rendering it inaccessible in traditional adsorption measurements. Data from solid-state magic angle spinning nuclear magnetic resonance spectroscopy, coupled with van der Waals-corrected density functional theory, indicate that ammonium carbamate chains formed at half capacity and full capacity adopt opposing configurations, and the need to convert between these states likely dictates the sluggish post-half-capacity uptake. By use of the more symmetric parent framework Mg2(pc-dobpdc) (pc-dobpdc4- = 3,3'-dioxidobiphenyl-4,4'-dicarboxylate), the metastable trap can be avoided and the full CO2 capacity of dmen-Mg2(pc-dobpdc) accessed under conditions relevant for carbon capture from coal-fired power plants.

Genomic diversity and selection sweeps identified in Indian swamp buffaloes reveals it's uniqueness with riverine buffaloes.

The present investigation was focused to study genomic diversity of Indian swamp buffalo populations through reduced representation approach (ddRAD). The heterozygosity (FST) among the swamp buffaloes was 0.11 between Assam and Manipuri; 0.20 between swamp (Manipuri) and riverine buffaloes; 0.30 between swamp (Manipuri) and cattle. The average observed and expected heterozygosity in swamp buffalo populations was 0.254 and 0.221 respectively. The Inbreeding coefficient (FIS) value was 0.02 among the swamp buffaloes. PCA and structure analysis revealed Manipuri swamp buffalo was genetically distinct and closely related to Nagaland swamp buffalo and least to Assam swamp buffalo. Identification of selective sweeps revealed 1087 regions to have undergone selection related to immune response, adaptation and nervous system. A total of 3451 SSRs were identified in the genome of swamp buffaloes. The study evidenced the genomic diversity in the swamp buffalo populations and its uniqueness in comparison with riverine buffalo and cattle.

Genomewide identification and annotation of SNPs in Bubalus bubalis.

The present study was carried out to identify and annotate the genome wide SNPs in Murrah buffalo genome. A total of 21.2 million raw reads from 4 pooled female Murrah buffalo samples were obtained using restriction enzyme digestion followed by sequencing with Illumina Hiseq 2000. After quality filtration, the reads were aligned to Murrah buffalo genome (ICAR-NBAGR) and Water buffalo genome (UMD_CASPUR_WB_2.0) which resulted in 99.37% and 99.67% of the reads aligning, respectively. A total of 130,688 high quality SNPs along with 35,110 indels were identified versus the Murrah bufffalo genome. Similarly 219,856 high quality SNPs along with 15,201 indels were identified versus the Water buffalo genome. We report 483 SNPs in 66 genes affecting Milk Production, 436 SNPs in 38 genes affecting fertility and 559 SNPs in 72 genes affecting other major traits. The average genome coverage was 13.4% and 14.8% versus the Murrah and Water buffalo genomes, respectively.

Genome-wide discovery of SNPs in candidate genes related to production and fertility traits in Sahiwal cattle.

The present study was carried out to identify genome-wide genetic markers and variants in candidate genes for production and reproduction traits in Sahiwal cattle using a cost-effective reduced representation sequencing method. A total of 258,231 genome-wide SNPs were identified in Sahiwal cattle with reference to Bos indicus genome, of which 150,231 were novel SNPs. Among the high-confidence SNPs identified, 91.86% and 27.30% were genotyped in 50% and 100% of the samples. Mapping of the identified SNPs revealed 525 SNPs in candidate genes related to production traits while 333 SNPs were mapped to candidate genes related to reproduction traits. The SNPs identified in this study will facilitate further insights on tropical adaptation, domestication history and population structure of indigenous cattle. The variants in candidate genes identified in this study will serve as useful genetic tools, in the quest for phenotype modifying nucleotide change and help in designing appropriate genetic improvement programs.

Thermodynamic Separation of 1-Butene from 2-Butene in Metal-Organic Frameworks with Open Metal Sites.

Most C4 hydrocarbons are obtained as byproducts of ethylene production or oil refining, and complex and energy-intensive separation schemes are required for their isolation. Substantial industrial and academic effort has been expended to develop more cost-effective adsorbent- or membrane-based approaches to purify commodity chemicals such as 1,3-butadiene, isobutene, and 1-butene, but the very similar physical properties of these C4 hydrocarbons make this a challenging task. Here, we examine the adsorption behavior of 1-butene, cis-2-butene, and trans-2-butene in the metal-organic frameworks M2(dobdc) (M = Mn, Fe, Co, Ni; dobdc4- = 2,5-dioxidobenzene-1,4-dicarboxylate) and M2(m-dobdc) (m-dobdc4- = 4,6-dioxidobenzene-1,3-dicarboxylate), which all contain a high density of coordinatively unsaturated M2+ sites. We find that both Co2(m-dobdc) and Ni2(m-dobdc) are able to separate 1-butene from the 2-butene isomers, a critical industrial process that relies largely on energetically demanding cryogenic distillation. The origin of 1-butene selectivity is traced to the high charge density retained by the M2+ metal centers exposed within the M2(m-dobdc) structures, which results in a reversal of the cis-2-butene selectivity typically observed at framework open metal sites. Selectivity for 1-butene adsorption under multicomponent conditions is demonstrated for Ni2(m-dobdc) in both the gaseous and the liquid phases via breakthrough and batch adsorption experiments.

Visual abilities distinguish pitchers from hitters in professional baseball.

This study aimed to evaluate the possibility that differences in sensorimotor abilities exist between hitters and pitchers in a large cohort of baseball players of varying levels of experience. Secondary data analysis was performed on 9 sensorimotor tasks comprising the Nike Sensory Station assessment battery. Bayesian hierarchical regression modelling was applied to test for differences between pitchers and hitters in data from 566 baseball players (112 high school, 85 college, 369 professional) collected at 20 testing centres. Explanatory variables including height, handedness, eye dominance, concussion history, and player position were modelled along with age curves using basis regression splines. Regression analyses revealed better performance for hitters relative to pitchers at the professional level in the visual clarity and depth perception tasks, but these differences did not exist at the high school or college levels. No significant differences were observed in the other 7 measures of sensorimotor capabilities included in the test battery, and no systematic biases were found between the testing centres. These findings, indicating that professional-level hitters have better visual acuity and depth perception than professional-level pitchers, affirm the notion that highly experienced athletes have differing perceptual skills. Findings are discussed in relation to deliberate practice theory.

Parental Satisfaction with Pediatric Day-Care Surgery and its Determinants in a Tertiary Care Hospital.

OBJECTIVE: The objective is to assess the level of parental satisfaction of pediatric day-care surgery and its different determinants. MATERIALS AND METHODS: This is a descriptive study performed in a tertiary care hospital in India among parents of pediatric day-care surgery patients from June 2013 to March 2015. The core questionnaire for the assessment of patient satisfaction for general day care (COPS-D) was used. Variables related to surgery, overall satisfaction, one open-ended question, and socio-demographic data were also collected. Calculated sample size was 121. RESULTS: The mean and standard deviation of parental satisfaction were estimated in eight domains of day care (COPS-D) using Likert scale 1-5. Preadmission visit had a mean of 4.63 (0.52), day of surgery 4.65 (0.58), operating room 4.76 (0.51), nursing care 4.46 (0.79), medical care 4.89 (0.48), information 4.51 (0.68), autonomy 4.64 (0.56), and discharge 4.50 (0.72). In elder children, there was less satisfaction on the information and discharge domains. Overall satisfaction was good in 88% of patients and was less than satisfactory when they had significant pain. CONCLUSION: Perception of quality of pediatric day-care surgery was assessed with a questionnaire and was found to be good. Variables related to surgery such as pain may be included in the questionnaire for assessing satisfaction in the day-care surgery.

Acute modification in plasma lipid levels in ultramarathon runners.

We aimed to evaluate the effects of a 24-h ultramarathon, an aerobic test of high physical load, on lipid profile and apolipoproteins B (ApoB) and A1 (ApoA1) levels, minimally modified low-density lipoprotein (LDL), and oxidised LDL. Prospective evaluation of 16 male athletes who participated in an ultramarathon run, where the objective was to run the greatest distance possible in 24 h. Fourteen participants completed the run. The mean distance achieved was 133.1 km (maximum of 169.6 km). There was a trend in reduction of triglycerides and total cholesterol (P = 0.06 and 0.05, respectively), without significant modifications in high-density lipoprotein, LDL and ApoA1 levels (P = 0.16; 0.55 and 0.67). There was a marked reduction in ApoB levels (P < 0.001), correlated directly to the distance covered (Pearson R = 0.68). Accordingly, an increase in the LDL/ApoB ratio was observed. The stress of this physical activity was not associated to an increase in minimally modified LDL or oxidised LDL. Lipid profile levels were not acutely altered by prolonged physical activity. Similarly, there was no evidence of greater oxidation of LDL over a 24-h period of physical activity. The reduction in ApoB was directly proportional to the distance covered, suggesting an acute positive change in phenotype of LDL molecules.

Spike Count Analysis for MultiPlexing Inference (SCAMPI).

Understanding how neurons encode multiple simultaneous stimuli is a fundamental question in neuroscience. We have previously introduced a novel theory of stochastic encoding patterns wherein a neuron's spiking activity dynamically switches among its constituent single-stimulus activity patterns when presented with multiple stimuli (Groh et al., 2024). Here, we present an enhanced, comprehensive statistical testing framework for such "multiplexing" or "code juggling". Our new approach evaluates whether dual-stimulus responses can be accounted for as mixtures of Poissons either anchored to or bounded by single-stimulus benchmarks. Our enhanced framework improves upon previous methods in two key ways. First, it introduces a stronger set of foils for multiplexing, including an "overreaching" category that captures overdispersed activity patterns unrelated to the single-stimulus benchmarks, reducing false detection of multiplexing/code-juggling. Second, it detects faster fluctuations - i.e. at sub-trial timescales - that would have been overlooked before. We utilize a Bayesian inference framework, considering the hypothesis with the highest posterior probability as the winner, and employ predictive recursion marginal likelihood method for the involving nonparametric density estimation. Reanalysis of previous findings confirms the general observation of "code juggling" and indicates that such juggling may well occur on faster timescales than previously suggested. We further confirm that juggling is more prevalent in (a) the inferotemporal face patch system for combinations of face stimuli than for faces and non-face objects; and (b) the primary visual cortex for distinct vs fused objects.

Signal switching may enhance processing power of the brain.

Our ability to perceive multiple objects is mysterious. Sensory neurons are broadly tuned, producing potential overlap in the populations of neurons activated by each object in a scene. This overlap raises questions about how distinct information is retained about each item. We present a novel signal switching theory of neural representation, which posits that neural signals may interleave representations of individual items across time. Evidence for this theory comes from new statistical tools that overcome the limitations inherent to standard time-and-trial-pooled assessments of neural signals. Our theory has implications for diverse domains of neuroscience, including attention, figure binding/scene segregation, oscillations, and divisive normalization. The general concept of switching between functions could also lend explanatory power to theories of grounded cognition.

Multiple objects evoke fluctuating responses in several regions of the visual pathway.

How neural representations preserve information about multiple stimuli is mysterious. Because tuning of individual neurons is coarse (e.g., visual receptive field diameters can exceed perceptual resolution), the populations of neurons potentially responsive to each individual stimulus can overlap, raising the question of how information about each item might be segregated and preserved in the population. We recently reported evidence for a potential solution to this problem: when two stimuli were present, some neurons in the macaque visual cortical areas V1 and V4 exhibited fluctuating firing patterns, as if they responded to only one individual stimulus at a time (Jun et al., 2022). However, whether such an information encoding strategy is ubiquitous in the visual pathway and thus could constitute a general phenomenon remains unknown. Here, we provide new evidence that such fluctuating activity is also evoked by multiple stimuli in visual areas responsible for processing visual motion (middle temporal visual area, MT), and faces (middle fundus and anterolateral face patches in inferotemporal cortex - areas MF and AL), thus extending the scope of circumstances in which fluctuating activity is observed. Furthermore, consistent with our previous results in the early visual area V1, MT exhibits fluctuations between the representations of two stimuli when these form distinguishable objects but not when they fuse into one perceived object, suggesting that fluctuating activity patterns may underlie visual object formation. Taken together, these findings point toward an updated model of how the brain preserves sensory information about multiple stimuli for subsequent processing and behavioral action.

A nonparametric empirical Bayes framework for large-scale multiple testing.

We propose a flexible and identifiable version of the 2-groups model, motivated by hierarchical Bayes considerations, that features an empirical null and a semiparametric mixture model for the nonnull cases. We use a computationally efficient predictive recursion (PR) marginal likelihood procedure to estimate the model parameters, even the nonparametric mixing distribution. This leads to a nonparametric empirical Bayes testing procedure, which we call PRtest, based on thresholding the estimated local false discovery rates. Simulations and real data examples demonstrate that, compared to existing approaches, PRtest's careful handling of the nonnull density can give a much better fit in the tails of the mixture distribution which, in turn, can lead to more realistic conclusions.

Multiple objects evoke fluctuating responses in several regions of the visual pathway.

How neural representations preserve information about multiple stimuli is mysterious. Because tuning of individual neurons is coarse (for example, visual receptive field diameters can exceed perceptual resolution), the populations of neurons potentially responsive to each individual stimulus can overlap, raising the question of how information about each item might be segregated and preserved in the population. We recently reported evidence for a potential solution to this problem: when two stimuli were present, some neurons in the macaque visual cortical areas V1 and V4 exhibited fluctuating firing patterns, as if they responded to only one individual stimulus at a time. However, whether such an information encoding strategy is ubiquitous in the visual pathway and thus could constitute a general phenomenon remains unknown. Here we provide new evidence that such fluctuating activity is also evoked by multiple stimuli in visual areas responsible for processing visual motion (middle temporal visual area, MT), and faces (middle fundus and anterolateral face patches in inferotemporal cortex - areas MF and AL), thus extending the scope of circumstances in which fluctuating activity is observed. Furthermore, consistent with our previous results in the early visual area V1, MT exhibits fluctuations between the representations of two stimuli when these form distinguishable objects but not when they fuse into one perceived object, suggesting that fluctuating activity patterns may underlie visual object formation. Taken together, these findings point toward an updated model of how the brain preserves sensory information about multiple stimuli for subsequent processing and behavioral action. Impact Statement: We find neural fluctuations in multiple areas along the visual cortical hierarchy that could allow the brain to represent distinct co-occurring visual stimuli.

Bayesian latent factor regression for functional and longitudinal data.

In studies involving functional data, it is commonly of interest to model the impact of predictors on the distribution of the curves, allowing flexible effects on not only the mean curve but also the distribution about the mean. Characterizing the curve for each subject as a linear combination of a high-dimensional set of potential basis functions, we place a sparse latent factor regression model on the basis coefficients. We induce basis selection by choosing a shrinkage prior that allows many of the loadings to be close to zero. The number of latent factors is treated as unknown through a highly-efficient, adaptive-blocked Gibbs sampler. Predictors are included on the latent variables level, while allowing different predictors to impact different latent factors. This model induces a framework for functional response regression in which the distribution of the curves is allowed to change flexibly with predictors. The performance is assessed through simulation studies and the methods are applied to data on blood pressure trajectories during pregnancy.

Coordinated multiplexing of information about separate objects in visual cortex.

Sensory receptive fields are large enough that they can contain more than one perceptible stimulus. How, then, can the brain encode information about each of the stimuli that may be present at a given moment? We recently showed that when more than one stimulus is present, single neurons can fluctuate between coding one vs. the other(s) across some time period, suggesting a form of neural multiplexing of different stimuli (Caruso et al., 2018). Here, we investigate (a) whether such coding fluctuations occur in early visual cortical areas; (b) how coding fluctuations are coordinated across the neural population; and (c) how coordinated coding fluctuations depend on the parsing of stimuli into separate vs. fused objects. We found coding fluctuations do occur in macaque V1 but only when the two stimuli form separate objects. Such separate objects evoked a novel pattern of V1 spike count ('noise') correlations involving distinct distributions of positive and negative values. This bimodal correlation pattern was most pronounced among pairs of neurons showing the strongest evidence for coding fluctuations or multiplexing. Whether a given pair of neurons exhibited positive or negative correlations depended on whether the two neurons both responded better to the same object or had different object preferences. Distinct distributions of spike count correlations based on stimulus preferences were also seen in V4 for separate objects but not when two stimuli fused to form one object. These findings suggest multiple objects evoke different response dynamics than those evoked by single stimuli, lending support to the multiplexing hypothesis and suggesting a means by which information about multiple objects can be preserved despite the apparent coarseness of sensory coding.