Toward Self-Healing Concrete Infrastructure: Review of Experiments and Simulations across Scales.

Cement and concrete are vital materials used to construct durable habitats and infrastructure that withstand natural and human-caused disasters. Still, concrete cracking imposes enormous repair costs on societies, and excessive cement consumption for repairs contributes to climate change. Therefore, the need for more durable cementitious materials, such as those with self-healing capabilities, has become more urgent. In this review, we present the functioning mechanisms of five different strategies for implementing self-healing capability into cement based materials: (1) autogenous self-healing from ordinary portland cement and supplementary cementitious materials and geopolymers in which defects and cracks are repaired through intrinsic carbonation and crystallization; (2) autonomous self-healing by (a) biomineralization wherein bacteria within the cement produce carbonates, silicates, or phosphates to heal damage, (b) polymer-cement composites in which autonomous self-healing occurs both within the polymer and at the polymer-cement interface, and (c) fibers that inhibit crack propagation, thus allowing autogenous healing mechanisms to be more effective. In all cases, we discuss the self-healing agent and synthesize the state of knowledge on the self-healing mechanism(s). In this review article, the state of computational modeling across nano- to macroscales developed based on experimental data is presented for each self-healing approach. We conclude the review by noting that, although autogenous reactions help repair small cracks, the most fruitful opportunities lay within design strategies for additional components that can migrate into cracks and initiate chemistries that retard crack propagation and generate repair of the cement matrix.

Achieving Decentralized, Electrified, and Decarbonized Ammonia Production.

The rapid reduction in the cost of renewable energy has motivated the transition from carbon-intensive chemical manufacturing to renewable, electrified, and decarbonized technologies. Although electrified chemical manufacturing technologies differ greatly, the feasibility of each electrified approach is largely related to the energy efficiency and capital cost of the system. Here, we examine the feasibility of ammonia production systems driven by wind and photovoltaic energy. We identify the optimal regions where wind and photovoltaic electricity production may be able to meet the local demand for ammonia-based fertilizers and set technology targets for electrified ammonia production. To compete with the methane-fed Haber-Bosch process, electrified ammonia production must reach energy efficiencies of above 20% for high natural gas prices and 70% for low natural gas prices. To account for growing concerns regarding access to water, geospatial optimization considers water stress caused by new ammonia facilities, and recommendations ensure that the identified regions do not experience an increase in water stress. Reducing water stress by 99% increases costs by only 1.4%. Furthermore, a movement toward a more decentralized ammonia supply chain driven by wind and photovoltaic electricity can reduce the transportation distance for ammonia by up to 76% while increasing production costs by 18%.

The Sex or Race of Program Directors May Not Play a Significant Role in Impacting Diversity Among Orthopaedic Surgery Residents.

PURPOSE: To identify the influence of residency program characteristics, including the presence of under-represented minorities in medicine (URiM) and/or female program directors (PDs), on the race and sex distribution of orthopaedic surgery residency trainees. METHODS: All active and Accreditation Council for Graduate Medical Education-accredited orthopaedic surgery residency programs from 2017-2021 that reported usable information in the Residency Explorer Tool were included. Data collected included program characteristics, as well as faculty and resident sex distribution, ethnicity, race, and demographic characteristics. The PDs' specific sex, ethnicity, race, and demographic characteristics were collected using residency program websites. The prevalence of factors in programs with the top quartile of female and URiM residents was compared with that in programs with the bottom 3 quartiles. RESULTS: Data were obtained from 148 of 200 Accreditation Council for Graduate Medical Education-accredited programs (3,694 residents). The 52 excluded programs had no usable information in the Residency Explorer Tool or on an identifiable program website. Overall, 15.9% of residents in orthopaedic surgery residency programs were women and 14% were under-represented minorities. The rates of female PDs and chairs were 12.4% and 6.9%, respectively, whereas those of URiM PDs and chairs were 8.3% and 4.6%, respectively. Programs with more female residents were not associated with female PDs (P = .79) or URiM PDs (P = .48). Programs with a greater percentage of URiM residents were not associated with URiM PDs (P = .16). Larger programs (P = .021) and university-based programs (P = .048) had a greater percentage of female residents. Orthopaedic residency programs with visa sponsorship had a greater percentage of URiM residents (P = .017). CONCLUSIONS: Programs with a higher percentage of female or URiM residents did not show a significant association with having female or URiM PDs. Larger programs and university-affiliated programs were more likely to have a larger percentage of female residents, whereas programs that offered visa sponsorship had a higher percentage of URiM residents. CLINICAL RELEVANCE: This study highlights factors influencing diversity among orthopaedic surgery residents. Although the presence of female or URiM PDs does not influence the percentage of female or URiM residents, other program characteristics such as size, affiliation, and visa sponsorship offer potentially actionable insights for promoting greater diversity in orthopaedic training. Doing so may increase under-represented groups within the field and could ultimately impact patient care and improve health care equity.

A systematic review of penetrating extracranial vertebral artery injuries.

BACKGROUND: Penetrating vertebral artery injuries (VAIs) are rare. Because of their rarity, complex anatomy, and difficult surgical exposures, few surgeons and trauma centers have developed significant experience with their management. The objectives of this study were to review their incidence, clinical presentation, radiologic identification, management, complications, and outcomes and to provide a review of anatomic exposures and surgical techniques for their management. METHODS: A literature search on MEDLINE Complete-PubMed, Cochrane, Ovid, and Embase for the period of 1893 to 2018 was conducted. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used. Our literature search yielded a total of 181 potentially eligible articles with 71 confirmed articles, consisting of 21 penetrating neck injury series, 13 VAI-specific series, and 37 case reports. Operative procedures and outcomes were recorded along with methods of angiographic imaging and operative management. All articles were reviewed by at least two independent authors, and data were analyzed collectively. RESULTS: There were a total of 462 patients with penetrating VAIs. The incidence of VAI in the civilian population was 3.1% vs 0.3% in the military population. More complete data were available from 13 collected VAI-specific series and 37 case reports for a total of 362 patients. Mechanism of injury data were available for 341 patients (94.2%). There were gunshot wounds (178 patients [49.2%]), stab wounds (131 [73.6%]), and miscellaneous mechanisms of injury (32 [8.8%]). Anatomic site of injury data were available for 177 (49%) patients: 92 (25.4%) left, 84 (23.2%) right, and 1 (0.3%) bilateral. Anatomic segment of injury data were available for 204 patients (56.4%): 28 (7.7%) V1, 125 (34.5%) V2, and 51 (14.1%) V3. Treatment data were available for 212 patients. Computed tomography angiography was the most common imaging modality (163 patients [77%]). Injuries were addressed by operative management (94 [44.3%]), angiography and angioembolization (72 [34%]), combined approaches (11 [5.2%]), and observation (58 [27.4%]). Stenting and repair were less frequently employed (10 [4.7%]). The incidence of aneurysms or pseudoaneurysms was 18.5% (67); the incidence of arteriovenous fistula was 16.9% (61). The calculated mortality in VAI-specific series was 15.1%; in the individual case report group, it was 10.5%. CONCLUSIONS: The majority of VAIs present without neurologic symptoms, although some may present with exsanguinating hemorrhage. Computed tomography angiography should be considered first line to establish diagnosis. Gunshot wounds account for most injuries. The most frequently injured segment is V2. Surgical ligation is the most common intervention, followed by angioembolization, both of which constitute important management approaches.

The Role of miR-126 in Critical Limb Ischemia Treatment Using Adipose-Derived Stem Cell Therapeutic Factor Concentrate and Extracellular Matrix Microparticles.

BACKGROUND Paracrine factors secreted by adipose-derived stem cells can be captured, fractionated, and concentrated to produce therapeutic factor concentrate (TFC). The present study examined whether TFC effects could be enhanced by combining TFC with a biological matrix to provide sustained release of factors in the target region. MATERIAL AND METHODS Unilateral hind limb ischemia was induced in rabbits. Ischemic limbs were injected with either placebo control, TFC, micronized small intestinal submucosa tissue (SIS), or TFC absorbed to SIS. Blood flow in both limbs was assessed with laser Doppler perfusion imaging. Tissues harvested at Day 48 were assessed immunohistochemically for vessel density; in situ hybridization and quantitative real-time PCR were employed to determine miR-126 expression. RESULTS LDP ratios were significantly elevated, compared to placebo control, on day 28 in all treatment groups (p=0.0816, p=0.0543, p=0.0639, for groups 2-4, respectively) and on day 36 in the TFC group (p=0.0866). This effect correlated with capillary density in the SIS and TFC+SIS groups (p=0.0093 and p=0.0054, respectively, compared to placebo). A correlation was observed between miR-126 levels and LDP levels at 48 days in SIS and TFC+SIS groups. CONCLUSIONS A single bolus administration of TFC and SIS had early, transient effects on reperfusion and promotion of ischemia repair. The effects were not additive. We also discovered that TFC modulated miR-126 levels that were expressed in cell types other than endothelial cells. These data suggested that TFC, alone or in combination with SIS, may be a potent therapy for patients with CLI that are at risk of amputation.

Liver-Directed Embolization for the Long-Term Control of Hypercalcemia of Malignancy in Metastatic Breast Cancer.

Hypercalcemia of malignancy is a common complication of certain types of cancers. No standard therapies exist for the treatment of hypercalcemia secondary to paraneoplastic syndromes that result in the long-term control of serum calcium levels. We report a case of metastatic breast cancer with parathyroid hormone-related protein associated with hypercalcemia of malignancy that was treated with transarterial embolization of the hepatic metastatic lesions.

Potential of metal-organic frameworks for separation of xenon and krypton.

CONSPECTUS: The total world energy demand is predicted to rise significantly over the next few decades, primarily driven by the continuous growth of the developing world. With rapid depletion of nonrenewable traditional fossil fuels, which currently account for almost 86% of the worldwide energy output, the search for viable alternative energy resources is becoming more important from a national security and economic development standpoint. Nuclear energy, an emission-free, high-energy-density source produced by means of controlled nuclear fission, is often considered as a clean, affordable alternative to fossil fuel. However, the successful installation of an efficient and economically viable industrial-scale process to properly sequester and mitigate the nuclear-fission-related, highly radioactive waste (e.g., used nuclear fuel (UNF)) is a prerequisite for any further development of nuclear energy in the near future. Reprocessing of UNF is often considered to be a logical way to minimize the volume of high-level radioactive waste, though the generation of volatile radionuclides during reprocessing raises a significant engineering challenge for its successful implementation. The volatile radionuclides include but are not limited to noble gases (predominately isotopes of Xe and Kr) and must be captured during the process to avoid being released into the environment. Currently, energy-intensive cryogenic distillation is the primary means to capture and separate radioactive noble gas isotopes during UNF reprocessing. A similar cryogenic process is implemented during commercial production of noble gases though removal from air. In light of their high commercial values, particularly in lighting and medical industries, and associated high production costs, alternate approaches for Xe/Kr capture and storage are of contemporary research interest. The proposed pathways for Xe/Kr removal and capture can essentially be divided in two categories: selective absorption by dissolution in solvents and physisorption on porous materials. Physisorption-based separation and adsorption on highly functional porous materials are promising alternatives to the energy-intensive cryogenic distillation process, where the adsorbents are characterized by high surface areas and thus high removal capacities and often can be chemically fine-tuned to enhance the adsorbate-adsorbent interactions for optimum selectivity. Several traditional porous adsorbents such as zeolites and activated carbon have been tested for noble gas capture but have shown low capacity, selectivity, and lack of modularity. Metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) are an emerging class of solid-state adsorbents that can be tailor-made for applications ranging from gas adsorption and separation to catalysis and sensing. Herein we give a concise summary of the background and development of Xe/Kr separation technologies with a focus on UNF reprocessing and the prospects of MOF-based adsorbents for that particular application.

Numerical Simulation of Permeability Change in Wellbore Cement Fractures after Geomechanical Stress and Geochemical Reactions Using X-ray Computed Tomography Imaging.

X-ray microtomography (XMT) imaging combined with three-dimensional (3D) computational fluid dynamics (CFD) modeling technique was used to study the effect of geochemical and geomechanical processes on fracture permeability in composite Portland cement-basalt caprock core samples. The effect of fluid density and viscosity and two different pressure gradient conditions on fracture permeability was numerically studied by using fluids with varying density and viscosity and simulating two different pressure gradient conditions. After the application of geomechanical stress but before CO2-reaction, CFD revealed fluid flow increase, which resulted in increased fracture permeability. After CO2-reaction, XMT images displayed preferential precipitation of calcium carbonate within the fractures in the cement matrix and less precipitation in fractures located at the cement-basalt interface. CFD estimated changes in flow profile and differences in absolute values of flow velocity due to different pressure gradients. CFD was able to highlight the profound effect of fluid viscosity on velocity profile and fracture permeability. This study demonstrates the applicability of XMT imaging and CFD as powerful tools for characterizing the hydraulic properties of fractures in a number of applications like geologic carbon sequestration and storage, hydraulic fracturing for shale gas production, and enhanced geothermal systems.

Damage Control Surgery and Transfer in Emergency General Surgery.

Selective non traumatic emergency surgery patients are targets for damage control surgery (DCS) to prevent or treat abdominal compartment syndrome and the lethal triad. However, DCS is still a subject of controversy. As a concept, DCS describes a series of abbreviated surgical procedures to allow rapid source control of hemorrhage and contamination in patients with circulatory shock to allow resuscitation and stabilization in the intensive care unit followed by delayed return to the operating room for definitive surgical management once the patient becomes physiologic stable. If appropriately applied, the DCS morbidity and mortality can be significantly reduced.

Energy Management and Economic Considerations of Intermittent Photovoltaic-Driven Electrochemical Ammonia Production.

As the energy sector shifts from fossil fuels to renewable energy, there is a need for long-duration energy storage solutions to handle the intermittency of renewable electricity. Electrofuels, or fuels synthesized from excess electricity, are an emerging medium poised to meet long-duration energy storage requirements. Ammonia as an electrofuel is potentially ideal because ammonia has a relatively low liquefaction pressure, indicating that ammonia can be easily stored and transported. Here, we develop a framework to optimize the electrochemical production of ammonia powered by intermittent photovoltaic power. We also explore various buyback policies to understand the impact that policy has on the cost of intermittent ammonia and optimal sizing ratios. The optimal ratio of the photovoltaic to the electrolyzer is ∼3.7 MWPV/MWELEC for a system that is completely powered by renewable photovoltaic power and operates intermittently. The optimal ratio of the photovoltaic to the electrolyzer is ∼3.3 MWPV/MWELEC for a system that uses photovoltaics in conjunction with grid electricity and operates continuously. For the purchase price at the avoided cost of electricity, the optimal ratio of the solar panel to the electrolyzer increases to ∼4 MWPV/MWELEC for a system that can only sell to the grid and ∼5 MWPV/MWELEC for a system that can buy and sell electricity to the grid at the avoided cost. Optimizing energy management by setting auxiliary battery size limits is essential to reducing ammonia costs, and the optimal battery size decreases as the buyback price of electricity increases. Finally, we find that systems connected to the grid and operating continuously have emissions comparable to the Haber-Bosch process because of the current emissions tied to the United States electricity generation. Thus, unless the grid is completely decarbonized, it is essential to create electrofuels that rely minimally on grid electricity.

Access to Total Knee Arthroplasty for Military Insured Patients.

Background: Rigorous training may lead to increased rates of knee osteoarthritis and arthroplasties in military service members. Given the large numbers of arthritis and the increasing need for total joint replacements, access to appropriate care can be difficult for this population based on insurance restrictions. The aim of this study was to evaluate access to total knee arthroplasty for TRICARE patients in contracted civilian medical facilities. Methods: Orthopedic surgeons contracted to perform total knee replacements in the state of Florida were identified via TRICARE's website. Investigators used a secret shopper methodology with a standardized script to request an appointment for their family member for a total knee arthroplasty using either TRICARE Select or BlueCross preferred provider organization. The appointment acceptance rates, wait times, call duration, and accuracy of the physician listing were collected. Results: A total of 228 offices that perform total knee arthroplasties in Florida were successfully contacted. Overall, 43.1% of the clinics had an inaccurate online listing, and 207 (91%) were able to schedule an appointment with TRICARE, compared to 93% for BlueCross Blue Shield (P = .06). The average wait for TRICARE patients was 24 days and 18 days for BlueCross (P < .01). Call times for TRICARE patients averaged 7.2 minutes, compared to 5.2 minutes for BlueCross (P < .01). Conclusions: TRICARE patients encountered longer waiting periods and inaccurate provider listings when accessing orthopedic care. Our results suggest a disparity in healthcare access for patients using TRICARE, which may result in negative health outcomes from receiving delayed care.

The Relationship Between an Individual's Birthday and Admission for Traumatic Injury.

BACKGROUND: Birthdays provide an opportunity to celebrate; however, they can also be associated with various adverse medical events. This is the first study to examine the association between birthdays and in-hospital trauma team evaluation. METHODS: This retrospective study analyzed trauma registry patients 19-89 years of age, who were evaluated by in-hospital trauma services from 1/1/2011 to 12/31/2021. RESULTS: 14,796 patients were analyzed and an association between trauma evaluation and birthdays was found. The strongest incidence rate ratios (IRRs) were on the day of birth (IRR: 1.78; P < .001) followed by ±3 days of the birthday (IRR: 1.21; P = .003). When incidence was analyzed by age groups, 19-36 years of age had the strongest IRR (2.30; P < .001) on their birthday, followed by the >65 groups (IRR: 1.34; P = .008) within ±3 days. Non-significant associations were seen in the 37-55 (IRR: 1.41; P = .209) and 56-65 groups (IRR: 1.60; P = .172) on their birthday. Patient-level characteristics were only significant for the presence of ethanol at trauma evaluation (risk ratio: 1.83; P = .017). DISCUSSION: Birthdays and trauma evaluations were found to have a group-dependent association, with the greatest incidence for the youngest age group being on their birthday, and the oldest age group within ±3 days. The presence of alcohol was found to be the best patient-level predictor of trauma evaluation.

Switching Kr/Xe selectivity with temperature in a metal-organic framework.

Krypton (Kr) and xenon (Xe) adsorption on two partially fluorinated metal-organic frameworks (FMOFCu and FMOFZn) with different cavity size and topologies are reported. FMOFCu shows an inversion in sorption selectivity toward Kr at temperatures below 0 °C while FMOFZn does not. The 1D microtubes packed along the (101) direction connected through small bottleneck windows in FMOFCu appear to be the reason for this peculiar behavior. The FMOFCu shows an estimated Kr/Xe selectivity of 36 at 0.1 bar and 203 K.

Insights into the temperature-dependent "breathing" of a flexible fluorinated metal-organic framework.

The framework expansion and contraction upon carbon dioxide uptake was studied in a partially fluorinated metal-organic framework, FMOF-2. The results show framework expansion and contraction (breathing) as a function of pressure and temperature. Even at temperatures as low as -30 °C, two phase transitions seem to take place with a pressure step (corresponding to the second transition) that is greatly dependent on temperature. This behavior is described by the model proposed by Coudert and co-workers showing that the material seems to undergo two phase transitions that are temperature-dependent. The isosteric heats of adsorption at high pressures show a minimum that is concurrent with the region of CO(2) loadings where the second pressure step occurs. It was deduced that these lower enthalpy values are a consequence of the energy cost related to the expansion or reopening of the framework. Lastly, the large and reversible breathing behavior may be a product of the combination of the high elasticity of zinc (II) coordination and the apparent high flexibility of the V-shaped organic building block.

In-hospital outcomes of intercostal nerve cryoablation and surgical stabilization of rib fractures.

BACKGROUND: Severe pain and pulmonary complications commonly follow rib fractures, both of which may be improved by surgical stabilization of rib fractures (SSRFs). However, significant postoperative pain still persists which may negatively impact in-hospital outcomes. Combining intercostal nerve cryoablation (INCA) with SSRF may improve those outcomes by further decreasing postoperative pain, opioid consumption, and pulmonary complications. The hypothesis is that INCA plus SSRF reduces opioids consumption compared with SSRF alone. METHODS: The retrospective analysis included trauma patients 18 years or older who underwent SSRF, with or without INCA, in a Level I trauma center between 2015 and 2021. Patients received INCA at the surgeons' discretion based on familiarity with the procedure and absence of contraindications. Patients without INCA were the historical control group. Reported data include demographics, mechanism and severity of injury, number of ribs stabilized, cryoablated nerves, intubation rates and duration of mechanical ventilation. The primary outcome was total morphine milligrams equivalent consumption. Secondary outcomes were intensive care unit length of stay, hospital length of stay, incidence of pneumonia, and tracheostomy rates, and discharge disposition. Long-term outcomes were examined up to 6 months for adverse events. RESULTS: Sixty-eight patients were included, with 44 receiving INCA. There were no differences in rates of pneumonia ( p = 0.106) or duration of mechanical ventilation ( p = 0.687), and hospital length of stay was similar between groups ( p = 0.059). However, the INCA group demonstrated lower total morphine milligrams equivalent ( p = 0.002), shorter intensive care unit length of stay ( p = 0.021), higher likelihood of home discharge ( p = 0.044), and lower rate of intubation ( p = 0.002) and tracheostomy ( p = 0.032). CONCLUSION: Combining INCA with SSRF may further improve in-hospital outcomes for patients with traumatic rib fractures. LEVEL OF EVIDENCE: Therapeutic/Care Management; Level III.

The Impact of Relocating a Trauma Center: Observations on Patient Injury Demographics and Resident Volumes.

Introduction Changing the physical zip code location of an academic trauma center may affect the distribution and surgical volume of its trauma patients. General surgical residency case log requirements may also be affected. This study describes the impact of moving a level I trauma center to a different zip code location, on the hospital and resident trauma case volumes. Methods This retrospective analysis included all patients within the local trauma registry across two fiscal years representing the pre- and post-move timeframes. Variables collected included patient basic sociodemographic and injury information, trauma activation level and transfer status, management (operative management [OPM] versus non-operative management [NOPM]), and resident case logs. Results During fiscal years 2016-2017 and 2017-2018, 3,025 patients were included. Pre-move and post-move trauma volumes were 1,208 and 1,817 respectively. Post-move changes demonstrated differences in basic sociodemographics, with differences in age (six years older), a shift toward white and away from black (12.89%), and males being seen more frequently (11.87%). Injury severity score distribution shifted (7.72%) towards less severe trauma scores (<15), the percentage of patients with blunt trauma (4.19%) and falls increased (ground level and greater than 1 meter, 9.78%) while the number of patients considered full activations were decreased (15.67%). Proportions of OPM and NOPM trauma cases remained unchanged with the exception of a reduction in emergent operative trauma (3.1%). Resident case logs requirements were met both pre- and post-move. Conclusion Relocating the trauma center to a different zip code location did not negatively impact our resident case volumes. Total trauma volumes were increased, with a shift in the demographics and severity distribution of injuries.

Takotsubo Cardiomyopathy and Trauma: The Role of Injuries as Physical Stressors.

INTRODUCTION: Physical stressors are common predisposing factors for takotsubo cardiomyopathy (TTC). However, the role of traumatic injuries in TTC has not been well defined. This study describes the characteristics of TTC in the broad spectrum of traumatic injuries using the information available in the National Trauma Data Bank (NTDB). MATERIALS AND METHODS: This retrospective study analyzed trauma patients ≥ 18 years old in the NTDB, from 2007 to 2018, with a diagnosis of TTC. RESULTS: A total of 95 TTC diagnoses were found. The median age was 68 years old (interquartile range: 55-80). Patients were predominantly female (67.4%), white (88.4%), and sustained blunt mechanisms of injury (90.5%). Penetrating trauma was most common in males (16%). Most diagnoses were related to extremity trauma (53.7%), followed by head injury (26.3%). The most common severity scores were Glasgow Coma Scale (GCS) > 13 or < 8, and Injury Severity Score (ISS) < 15 or > 25. Males more commonly presented with GCS < 8 (68%), ISS > 25 (33%), high intensive care unit (ICU) admission rate (77.4%), and mechanical ventilation (51.6%). The median duration of the mechanical ventilation was eight days for both sexes. The ICU length of stay (LOS) was six days with a hospital LOS of nine days and a trend toward a longer LOS in males. The in-hospital mortality rate was 11.7% for both sexes. CONCLUSIONS: TTC in traumatic injuries is common at both ends of the severity spectrum and has different sex distribution. TTC patients are predominantly females and have more commonly extremity trauma than head injury. Males are more severely injured and under mechanical ventilation.

Synthesis, characterization, and application of metal organic framework nanostructures.

The considerable number of important physical properties, including optical, electronic, and magnetic properties, of Prussian blue (PB) analogues have attracted fundamental and industrial interest. Nevertheless, the gas sorption properties of PB coordination compounds were only investigated very recently. In this work, we report the synthesis and gas sorption properties of PB nanocomposites with different size and shape obtained by using poly(vinylpyrrolidone) (PVP), chitosan, and dioctyl sodium sulfosuccinate (AOT) as stabilizers and structure directing agents. All three porous nanocrystals show high and selective CO(2) adsorption over CH(4) or N(2). No distinct relationship was found between the size (or shape) of the nanosorbents and their gas uptake capacities. To our knowledge, this is the first report on the use of PB nanocomposites for CO(2) capture applications.

Prussian blue analogues for CO(2) and SO(2) capture and separation applications.

Adsorption isotherms of pure gases present in flue gas including CO(2), N(2), SO(2), NO, H(2)S, and water were studied using prussian blues of chemical formula M(3)[Co(CN)(6)](2).nH(2)O (M = Co, Zn) using an HPVA-100 volumetric gas analyzer and other spectroscopic methods. All the samples were characterized, and the microporous nature of the samples was studied using the BET isotherm. These materials adsorbed 8-10 wt % of CO(2) at room temperature and 1 bar of pressure with heats of adsorption ranging from 200 to 300 Btu/lb of CO(2), which is lower than monoethanolamine (750 Btu/lb of CO(2)) at the same mass loading. At high pressures (30 bar and 298 K), these materials adsorbed approximately 20-30 wt % of CO(2), which corresponds to 3 to 5 molecules of CO(2) per formula unit. Similar gas adsorption isotherms for SO(2), H(2)S, and NO were collected using a specially constructed volumetric gas analyzer. At close to 1 bar of equilibrium pressure, these materials sorb around 2.5, 2.7, and 1.2 mmol/g of SO(2), H(2)S, and NO. In particular, the uptake of SO(2) and H(2)S in Co(3)[Co(CN)(6)](2) is quite significant since it sorbs around 10 and 4.5 wt % at 0.1 bar of pressure. The stability of prussian blues before and after trace gases was studied using a powder X-ray diffraction instrument, which confirms these materials do not decompose after exposure to trace gases.

Advancements toward the greener processing of engineered nanomaterials--effect of core size on the dispersibility and transport of gold nanocrystals in near-critical solvents.

The ability to process and purify engineered nanomaterials using near critical or supercritical fluids (NcFs or ScFs) has enormous potential for the application at various stages of the development of green nanomaterials. The dispersibility of octanethiol-stabilized gold nanocrystals of different core sizes is explored, which were chosen to serve as model nanomaterials of general interest in compressed ethane and propane over a wide range of fluid conditions. Both solvents have enormous potential for the environmentally benign processing and transport of engineered nanomaterials due to their nominal toxicity and high degree of tunability and processability that can essentially eliminate solvent waste. The dispersibility is determined by measuring the absorption spectra of dispersions of various sizes of nanocrystals in NcFs. To better understand the obtained results three models, the total interaction theory, the sedimentation coefficient equation, and the Chrastil method, are discussed. Nanoparticle dispersibility versus density plots are strongly dependent on nanoparticle size and solvent conditions, with the dispersion of larger nanocrystals more dependent on changes of pressure or density at a given temperature. For the range of nanoparticle sizes studied, compressed ethane at 25 degrees C leads to a greater tunability of nanoparticle dispersion when compared with compressed propane at 65 degrees C. For equivalent pressures, compressed propane is found to provide better solubility than ethane due to its higher density. The results quantitatively demonstrate that NcFs can offer pressure-tunable, size-selective control of nanoparticle solvation and transport at easily obtainable temperature and pressure conditions. These capabilities provide clear advantages over conventional solvents and direct application to various nanomaterials processes, such as synthesis, separation, transport, and purification of nanocrystals.