Supported Platinum Nanoparticles Catalyzed Carbon-Carbon Bond Cleavage of Polyolefins: Role of the Oxide Support Acidity

Supported platinum nanoparticle catalysts are known to convert polyolefins to high-quality liquid hydrocarbons using hydrogen under relatively mild conditions. To date, few studies using platinum grafted onto various metal oxide (MxOy) supports have been undertaken to understand the role of the acidity of the oxide support in the carbon-carbon bond cleavage of polyethylene under consistent catalytic conditions. Specifically, two Pt/MxOy catalysts (MxOy = SrTiO3 and SiO2-Al2O3; Al = 3.0 wt %, target Pt loading 2 wt % Pt ∼1.5 nm), under identical catalytic polyethylene hydrogenolysis conditions (T = 300 °C, P(H2) = 170 psi, t = 24 h; Mw = ∼3,800 g/mol, Mn = ∼1,100 g/mol, Đ = 3.45, Nbranch/100C = 1.0), yielded a narrow distribution of hydrocarbons with molecular weights in the range of lubricants (Mw = < 600 g/mol; Mn < 400 g/mol; Đ = 1.5). While Pt/SrTiO3 formed saturated hydrocarbons with negligible branching, Pt/SiO2-Al2O3 formed partially unsaturated hydrocarbons (<1 mol % alkenes and ∼4 mol % alkyl aromatics) with increased branch density (Nbranch/100C = 5.5). Further investigations suggest evidence for a competitive hydrocracking mechanism occurring alongside hydrogenolysis, stemming from the increased acidity of Pt/SiO2-Al2O3 compared to Pt/SrTiO3. Additionally, the products of these polymer deconstruction reactions were found to be independent of the polyethylene feedstock, allowing the potential to upcycle polyethylenes with various properties into a value-added product.

Scalable Synthesis of Pt/SrTiO3 Hydrogenolysis Catalysts in Pursuit of Manufacturing-Relevant Waste Plastic Solutions

An improved hydrothermal synthesis of shape-controlled, size-controlled 60 nm SrTiO₃ nanocuboid (STO NC) supports, which facilitates the scalable creation of platinum nanoparticle catalysts supported on STO (Pt/STO) for the chemical conversion of waste polyolefins, is reported herein. This synthetic method (1) establishes that STO nucleation prior to the hydrothermal treatment favors nanocuboid formation, (2) produces STO NC supports with average sizes ranging from 25 to 80 nm with narrow size distributions, and (3) demonstrates how SrCO₃ formation and variation in solution pH prevent the formation of STO NCs. The STO synthesis was scaled-up and conducted in a 4 L batch reactor, resulting in STO NCs of comparable size and morphology (m = 22.5 g, d_avg = 58.6 ± 16.2 nm) to those synthesized under standard hydrothermal conditions in a lab-scale 125 mL autoclave reactor. Size-controlled STO NCs, ranging in roughly 10 nm increments from 25 to 80 nm, were used to support Pt deposited through strong electrostatic adsorption (SEA), a practical and scalable solution-based method. Using SEA techniques and an STO support with an average size of 39.3 ± 6.3 nm, a Pt/STO catalyst with 3.6 wt % Pt was produced and used for high-density polyethylene hydrogenolysis under previously reported conditions (170 psi H₂, 300 °C, 96 h; final product: M_w = 2400, Đ = 1.03). As a well-established model system for studying the behavior of heterogeneous catalysts and their supports, the Pt/STO system detailed in this work presents a unique opportunity to simultaneously convert waste plastic into commercially viable products while gaining insight into how scalable inorganic synthesis can support transformative manufacturing.

Assessing the Single and Combined Toxicity of the Bioinsecticide Spear and Cry3Bb1 Protein Against Susceptible and Resistant Western Corn Rootworm Larvae (Coleoptera: Chrysomelidae)

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), poses a serious threat to maize (Zea mays L.) growers in the U.S. Corn Belt. Transgenic corn expressing Bacillus thuringiensis (Bt) Berliner is the major management tactic along with crop rotation. Bt crops targeting WCR populations have been widely planted throughout the Corn Belt. Rootworms have developed resistance to nearly all management strategies including Bt corn. Therefore, there is a need for new products that are not cross-resistant with the current Bt proteins. In this study, we evaluated the susceptibility of WCR strains resistant and susceptible to Cry3Bb1 to the biological insecticide Spear-T (GS-omega/kappa-Hexatoxin-Hv1a) alone and combined with Cry3Bb1 protein. The activity of Hv1a alone was similar between Cry3Bb1-resistant and susceptible strains (LC50s = 0.95 mg/cm2 and 1.50 mg/cm2, respectively), suggesting that there is no cross-resistance with Cry3Bb1 protein. Effective concentration (EC50), molt inhibition concentration (MIC50), and inhibition concentration (IC50) values of Hv1a alone were also similar between both strains, based on non-overlapping confidence intervals. Increased mortality (64%) was observed on resistant larvae exposed to Hv1a (0.6 mg/cm2) + Cry3Bb1 protein (170.8 µg/cm2) compared to 0% mortality when exposed to Cry3Bb1 alone and 34% mortality to Hv1a alone (0.3 mg/cm2). The time of larval death was not significantly different between Hv1a alone (3.79 mg/cm2) and Hv1a (0.6 mg/cm2) + Cry3Bb1 (170.8 µg/cm2). New control strategies that are not cross-resistant with current insecticides and Bt proteins are needed to better manage the WCR, and Hv1a together with Cry3Bb1 may fit this role.

Synthetic Lubricants Derived from Plastic Waste and their Tribological Performance

The energy efficiency, mechanical durability, and environmental compatibility of all moving machine components rely heavily on advanced lubricants for smooth and safe operation. Herein an alternative family of high-quality liquid (HQL) lubricants was derived by the catalytic conversion of pre- and post-consumer polyolefin waste. The plastic-derived lubricants performed comparably to synthetic base oils such as polyalphaolefins (PAOs), both with a wear scar volume (WSV) of 7.5×10^-5  mm^-3 . HQLs also performed superior to petroleum-based lubricants such as Group III mineral oil with a WSV of 1.7×10^-4  mm^-3 , showcasing a 44 % reduction in wear. Furthermore, a synergistic reduction in friction and wear was observed when combining the upcycled plastic lubricant with synthetic oils. Life cycle and techno-economic analyses also showed this process to be energetically efficient and economically feasible. This novel technology offers a cost-effective opportunity to reduce the harmful environmental impact of plastic waste on our planet and to save energy through reduction of friction and wear-related degradations in transportation applications akin to synthetic oils.

Upcycling Single-Use Polyethylene into High-Quality Liquid Products

Our civilization relies on synthetic polymers for all aspects of modern life; yet, inefficient recycling and extremely slow environmental degradation of plastics are causing increasing concern about their widespread use. After a single use, many of these materials are currently treated as waste, underutilizing their inherent chemical and energy value. In this study, energy-rich polyethylene (PE) macromolecules are catalytically transformed into value-added products by hydrogenolysis using well-dispersed Pt nanoparticles (NPs) supported on SrTiO₃ perovskite nanocuboids by atomic layer deposition. Pt/SrTiO₃ completely converts PE (M _n = 8000-158,000 Da) or a single-use plastic bag (M _n = 31,000 Da) into high-quality liquid products, such as lubricants and waxes, characterized by a narrow distribution of oligomeric chains, at 170 psi H₂ and 300 °C under solvent-free conditions for reaction durations up to 96 h. The binding of PE onto the catalyst surface contributes to the number averaged molecular weight (M _n) and the narrow polydispersity (Đ) of the final liquid product. Solid-state nuclear magnetic resonance of ¹³C-enriched PE adsorption studies and density functional theory computations suggest that PE adsorption is more favorable on Pt sites than that on the SrTiO₃ support. Smaller Pt NPs with higher concentrations of undercoordinated Pt sites over-hydrogenolyzed PE to undesired light hydrocarbons.

Complex surface structure of (110) terminated strontium titanate nanododecahedra

The surface structure of (110) faceted strontium titanate nanoparticles synthesized via solvothermal method has been resolved using high-resolution electron microscopy (HREM). We demonstrate that the surface is a titania-rich structure containing tetrahedrally coordinated TiO₄ units similar to the family of (n × 1) reconstructions observed on (110) surfaces of bulk crystalline strontium titanate. When compared with prior results for (001) terminated strontium titanate single crystals made with traditional transmission electron microscopy (TEM) sample preparation techniques, the results demonstrate that many models for oxide nanoparticles need to be revisited. This work serves as a reminder that attention must be paid to the surface of nanoparticles. Even with a simple perovskite as the starting point the end result can be very complex. As more materials are synthesized on the nanoscale, this will become increasingly important to take into consideration.

Synthesis-dependent atomic surface structures of oxide nanoparticles

Using SrTiO3 nanocuboids as a model system, we show with aberration-corrected high resolution electron microscopy at sub-Å resolution that surface relaxations or reconstructions are present on the nanocuboids, depending on the synthetic process. Oleic acid synthesis, acetic acid synthesis, and microwave-assisted acetic acid synthesis result in a SrO termination, TiO2-rich reconstruction, and mixed termination, respectively. The experimental atomic positions are in better agreement with density functional theory calculations using an exact-exchange corrected PBEsol functional than the Perdew-Burke-Ernzerhof (PBE) functional.

Clinical implications of unmanaged needle-insertion pain and distress in children

Increasing evidence has demonstrated that pain from venipuncture and intravenous cannulation is an important source of pediatric pain and has a lasting impact. Ascending sensory neural pain pathways are functioning in preterm and term infants, yet descending inhibitory pathways seem to mature postnatally. Consequently, infants may experience pain from the same stimulus more intensely than older children. In addition, painful perinatal procedures such as heel lancing or circumcision have been found to correlate with stronger negative responses to venipuncture and intramuscular vaccinations weeks to months later. Similarly, older children have reported greater pain during follow-up cancer-related procedures if the pain of the initial procedure was poorly controlled, despite improved analgesia during the subsequent procedures. Fortunately, both pharmacologic and nonpharmacologic techniques have been found to reduce children's acute pain and distress and subsequent negative behaviors during venipuncture and intravenous catheter insertion. This review summarizes the evidence for the importance of managing pediatric procedural pain and methods for reducing venous access pain.

On the front lines: lessons learned in implementing multidisciplinary peripheral venous access pain-management programs in pediatric hospitals

Venipuncture and intravenous cannulation are among the most common and widespread medical procedures performed on children today. Therefore, effective treatment of venous access pain can benefit from an integrated systems approach that enlists multiple players in the health care system. By using case studies that analyze this issue from the perspective of the nurse, the physician, the pharmacist, and the child life specialist, this article illustrates how multidisciplinary programs designed to manage needle pain have been developed successfully in several institutions. Common themes that arise from these case studies include the importance of a multidisciplinary evidence-based approach to advocate change; a system-wide protocol for the administration of local anesthetics; convenient access to topical local anesthetics; department and hospital-wide support for educational efforts, including training in nonpharmacologic techniques used by child life specialists; and ongoing quantification of the overall success of any program. Implementation of these strategies can result in significant improvements in the pediatric venous access experience.

Thermodynamic and structure guided design of statin based inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase

Clinical studies have demonstrated that statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) inhibitors, are effective at lowering mortality levels associated with cardiovascular disease; however, 2-7% of patients may experience statin-induced myalgia that limits compliance with a treatment regimen. High resolution crystal structures, thermodynamic binding parameters, and biochemical data were used to design statin inhibitors with improved HMGR affinity and therapeutic index relative to statin-induced myalgia. These studies facilitated the identification of imidazole 1 as a potent (IC 50 = 7.9 nM) inhibitor with excellent hepatoselectivity (>1000-fold) and good in vivo efficacy. The binding of 1 to HMGR was found to be enthalpically driven with a Delta H of -17.7 kcal/M. Additionally, a second novel series of bicyclic pyrrole-based inhibitors was identified that induced order in a protein flap of HMGR. Similar ordering was detected in a substrate complex, but has not been reported in previous statin inhibitor complexes with HMGR.

Hepatoselectivity of statins: design and synthesis of 4-sulfamoyl pyrroles as HMG-CoA reductase inhibitors

4-Sulfamoyl pyrroles were designed as novel hepatoselective HMG-CoA reductase inhibitors (statins) to reduce myalgia, a statin-induced adverse effect. The compounds were prepared via a [3+2] cycloaddition of a Münchnone with a sulfonamide-substituted alkyne. We identified compounds with greater selectivity for hepatocytes compared to L6-myocytes than rosuvastatin and atorvastatin. There was an inverse correlation of myocyte potencies and ClogP values. A number of analogs were effective at reducing cholesterol in acute and chronic in vivo models but they lacked sufficient chronic in vivo activity to warrant further development.

A randomized comparison of nitrous oxide plus hematoma block versus ketamine plus midazolam for emergency department forearm fracture reduction in children

OBJECTIVES

Ketamine provides effective and relatively safe sedation analgesia for reduction of fractures in children in the emergency department. However, prolonged recovery and adverse effects suggest the opportunity to develop alternative strategies. We compared the efficacy and adverse effects of ketamine/midazolam to those of nitrous oxide/hematoma block for analgesia and anxiolysis during forearm fracture reduction in children.

METHODS

Children 5 to 17 years of age were randomly assigned to receive intravenous ketamine (1 mg/kg)/midazolam (0.1 mg/kg; max: 2.5 mg) or 50% nitrous oxide/50% oxygen and a hematoma block (2.5 mg/kg of 1% buffered lidocaine). All of the children received oral oxycodone 0.2 mg/kg (max: 15 mg) at triage > or = 45 minutes before reduction. Videotapes were obtained before (baseline), during (procedure), and after (recovery) reduction and scored using the Procedure Behavioral Checklist by an observer blinded to study purpose. The primary outcome measure was the mean change in Procedure Behavioral Checklist score from baseline to procedure, with greater change indicating greater procedure distress. Other outcome measures of efficacy included recovery times and visual analog scale scores to assess patient distress, parent report of child distress, and orthopedic surgeon satisfaction with sedation. Adverse effects were assessed during the emergency visit and by telephone 1 day after reduction. Data were analyzed using repeated measures, that is, analysis of variance, chi2, and t tests.

RESULTS

There were 102 children (mean age: 9.0 +/- 3.0 years) who were randomly assigned. There was no difference in age, race, gender, and baseline Procedure Behavioral Checklist scores between ketamine/midazolam (55 subjects) and nitrous oxide/hematoma block (47 subjects). Mean changes in Procedure Behavioral Checklist scores were very small for both groups. The mean change in Procedure Behavioral Checklist was less for nitrous oxide/hematoma block, and patients and parents reported less pain during fracture reduction with nitrous oxide/hematoma block. Recovery times were markedly shorter for nitrous oxide/hematoma block compared with ketamine/midazolam. Orthopedic surgeons were similarly satisfied with the 2 regimens. Of the ketamine/midazolam subjects, 11% had O2 saturations < 94%. Other adverse effects occurred in both groups, but more often in ketamine/midazolam both during the emergency visit and at 1-day follow-up.

CONCLUSIONS

In children who had received oral oxycodone, both nitrous oxide/hematoma block and ketamine/midazolam resulted in minimal increases in distress during forearm fracture reduction at the doses studied. The nitrous oxide/hematoma block regimen had fewer adverse effects and significantly less recovery time.

Emergency department management of pain and anxiety related to orthopedic fracture care: a guide to analgesic techniques and procedural sedation in children

Orthopedic fractures and joint dislocations are among the most painful pediatric emergencies. Safe and effective management of fracture-related pain and anxiety in the emergency department reduces patient distress during initial evaluation and often allows definitive management of the fracture. No consensus exists on which pharmacologic regimens for procedural sedation/analgesia are safest and most effective. For some children, control of fracture pain is the primary goal, whereas for others, relief from anxiety is an additionally important objective. Furthermore, strategies for the management of fracture pain may vary by fracture location and patient characteristics; thus, no single regimen is likely to provide the best means of analgesia and anxiolysis for all patients. Effective analgesia can be provided by local or regional anesthesia, such as hematoma, Bier, or nerve blocks. Alternatively, induction of deep sedation with analgesic agents such as ketamine or fentanyl, often combined with sedative-anxiolytic agents such as midazolam, may be used to manage distress associated with fracture reduction. A combination of local anesthesia with moderate sedation, for example nitrous oxide, is another attractive option.

Sedation for peritonsillar abscess drainage in the pediatric emergency department

OBJECTIVE

To evaluate the use of intravenous (IV) sedation in children during peritonsillar abscess (PTA) incision and drainage in the emergency department (ED).

DESIGN

Retrospective review of medical records of children with a diagnosis of PTA.

SETTING

The ED of a large, urban, academic children's hospital.

PATIENTS

Consecutive patients 18 years or younger presenting from April 1995 to November 1998.

METHODS

Information was retrieved from a time-based sedation record that included age, sex, ASA classification, time since last liquid or solid, agent and dose, level of sedation (A=alert, V=response to voice, P=purposeful response to pain, U=unresponsive), vital signs, complications, recovery time, and disposition.

RESULTS

Forty-two patients had incision and drainage performed with IV sedation in the ED. Mean age was 11.3 +/- 4.3 years (range 4-18 years); 57% were African-American, and 64% were female. Agents used included ketamine plus midazolam (K/M) (n = 36, 86%), morphine plus midazolam (n = 3, 7%), meperidine plus midazolam (n = 2, 5%), and nitrous oxide plus midazolam (n = 1, 2%). No cardiorespiratory complications, including laryngospasm, occurred. Vomiting occurred in 1 patient who received meperidine and midazolam. The deepest level of sedation reached included: 12% A, 64% V, and 24% P. No patient who had an abscess drained in the ED with IV sedation was admitted, and mean recovery time was 81.0 +/- 30.1 minutes.

CONCLUSIONS

IV sedation in children for incision and drainage of PTA by skilled personnel in the ED may eliminate the need for admission and surgical drainage in the operating room. K/M was used most frequently, without adverse effect, and all patients were discharged from the ED. Because K/M may result in deep sedation, appropriate personnel and equipment must be present.

Maintenance of column performance at scale

Pack-in-place column packing methods were developed for Q Sepharose Big Beads at 40 cm I.D. and scaled up to 200 cm I.D. in Chromaflow columns. The efficiency and asymmetry of the packed bed were evaluated as a function of test velocity and sample volume. The performance of the packed beds at both scales approached the theoretical limits of column performance (Hred =2 and Af=1) expected in small analytical columns. The packing strategy was effective for scale up and the stability of the packed beds, the effectiveness of the column design with respect to the mobile phase distribution system and the stability of the media to the pack-in-place technology, are presented.

Pharmacological management of pain and anxiety during emergency procedures in children

Painful procedures are frequently required during treatment of children in the emergency department and are very stressful for the children, their parents and healthcare providers. Pharmacological methods to safely provide almost painless local anaesthesia, analgesia and anxiolysis have been increasingly studied in children. With knowledge of these methods, and patience, the emergency care provider can greatly reduce the distress often associated with emergency care of children. Topical local anaesthetics such as LET [lidocaine (lignocaine), epinephrine (adrenaline), tetracaine] or buffered lidocaine injected through the wound with fine needles can almost painlessly anaesthetise lacerations for suturing. Topical creams such as lidocaine/ prilocaine (EMLA) or tetracaine, iontophoresed lidocaine, or buffered lidocaine subcutaneously injected with fine needles can make intravenous catheter placement virtually 'painless'. When anxiety is significant, and mild to moderate analgesia/ anxiolysis/amnesia is needed, nitrous oxide can be administered if the proper delivery devices are available. Alternatively, when intensely painful fracture reduction, burn debridement, or abscess drainage is necessary, well tolerated and effective deep sedation can be achieved with careful use of midazolam and either ketamine or fentanyl.

A randomized clinical trial of continuous-flow nitrous oxide and midazolam for sedation of young children during laceration repair

STUDY OBJECTIVE

To compare the efficacy and complication profile of oral midazolam therapy and continuous-flow 50% nitrous oxide in alleviating anxiety during laceration repair in children 2 to 6 years old.

METHODS

We conducted a prospective, randomized clinical trial using 4 study groups who required laceration repair: (1) children who received standard care alone, which included comforting and topical anesthesia augmented with injected lidocaine if needed; (2) children who received standard care and oral midazolam; (3) children who received standard care and nitrous oxide; and (4) children who received standard care, oral midazolam, and nitrous oxide. Videotapes were blindly scored using the Observational Scale of Behavioral Distress-Revised (OSBD-R) to assess distress during baseline, wound cleaning, lidocaine injecting, suturing, and recovery. Adverse effects were noted during suturing and by parent questionnaires completed 24 hours after suturing and at suture removal. OSBD-R data were analyzed using repeated-measures analysis of variance. Adverse effect data were analyzed using categorical models.

RESULTS

Two hundred four subjects were enrolled (midazolam plus nitrous oxide 52, midazolam 51, nitrous oxide 51, standard care 50; mean patient age was 4.1 years; 66% were boys). Mean OSBD-R scores were lower for groups that received nitrous oxide during wound cleaning by 2.2 points (95% confidence interval [CI] 1.1 to 3.2), lidocaine injecting by 2.5 points (95% CI 1.4 to 3.5), and suturing by 2.9 (95% CI 1.8 to 3.9). Adverse effects occurred more frequently, and recovery times were longer for groups that received midazolam.

CONCLUSION

For facial suturing in 2- to 6-year-old children, regimens including continuous-flow nitrous oxide were more effective in reducing distress, and had fewer adverse effects and shorter recovery times than midazolam.

The "ouchless emergency department". Getting closer: advances in decreasing distress during painful procedures in the emergency department

Painful and frightening injuries and illnesses are frequent reasons for children to seek care in an emergency department. Painful therapeutic procedures are often a necessary part of emergency care and are very distressful for the children, their parents, and healthcare providers. Inadequately relieved pain and distress have acute and long-term consequences, yet methods for pain and anxiety reduction during frightening minor and major procedures are often not used because of lack of detailed knowledge of techniques and fear of adverse effects. This article reviews psychologic and pharmacologic means of safe and effective reduction of anxiety and pain during emergency department procedures.

Continuous-flow delivery of nitrous oxide and oxygen: a safe and cost-effective technique for inhalation analgesia and sedation of pediatric patients

Nitrous oxide (N2O) safely and rapidly alleviates the pain and distress of minor procedures in the emergency department (ED). We have found self-administration in children does not consistently achieve acceptable analgesia and sedation. The equipment generally available for ED use is designed for adults and delivers 50% N2O through a demand valve that requires an inspiratory effort of -3 to -5 cm of water to activate gas flow. This is difficult for young children who are crying, have more shallow respirations than adults, or cannot follow instructions. In collaboration with the Departments of Anesthesiology, Dentistry, and Respiratory Therapy, we constructed a continuous-flow system for delivering N2O and oxygen (O2). The following is a description of the components, assembly, and use of a continuous-flow machine that safely and inexpensively delivers N2O and O2 to children.

Comparison of fentanyl/midazolam with ketamine/midazolam for pediatric orthopedic emergencies

OBJECTIVE

Emergency management of pediatric fractures and dislocations requires effective analgesia, yet children's pain is often undertreated. We compared the safety and efficacy of fentanyl- versus ketamine- based protocols.

METHODOLOGY

Patients 5 to 15 years of age needing emergency fracture or joint reduction (FR) were randomized to receive intravenous midazolam plus either fentanyl (F/M) or ketamine (K/M). Measures of efficacy were observational distress scores and self- and parental-report. Measures of safety were frequency of abnormalities in and need for support of cardiopulmonary function and other adverse effects.

RESULTS

During FR, K/M subjects (n = 130) had lower distress scores and parental ratings of pain and anxiety than did F/M subjects (n = 130). Although both regimens equally facilitated reductions, deep sedation, and procedural amnesia, orthopedists favored K/M. Recovery was 14 minutes longer for K/M. Fewer K/M subjects had hypoxia (6% vs 25%), needed breathing cues (1% vs 12%), or required oxygen (10% vs 20%) than did F/M subjects. Two K/M subjects required assisted ventilation briefly. More K/M subjects vomited. Adverse emergence reactions were rare but equivalent between regimens.

CONCLUSIONS

During emergency pediatric orthopedic procedures, K/M is more effective than F/M for pain and anxiety relief. Respiratory complications occurred less frequently with K/M, but respiratory support may be needed with either regimen. Both regimens facilitate reduction, produce amnesia, and rarely cause emergence delirium. Vomiting is more frequent and recovery more prolonged with K/M.