Investigation of nanodispersion in polystyrene-montmorillonite nanocomposites by solid state NMR

Nanocomposites result from combinations of materials with vastly different properties in the nanometer scale. These materials exhibit many unique properties such as improved thermal stability, reduced flammability, and improved mechanical properties. Many of the properties associated with polymer–clay nanocomposites are a function of the extent of exfoliation of the individual clay sheets or the quality of the nanodispersion. This work demonstrates that solid-state NMR can be used to characterize, quantitatively, the nanodispersion of variously modified montmorillonite (MMT) clays in polystyrene (PS) matrices. The direct influence of the paramagnetic Fe3, embedded in the aluminosilicate layers of MMT, on polymer protons within about 1 nm from the clay surfaces creates relaxation sources, which, via spin diffusion, significantly shorten the overall proton longitudinal relaxation time (T1 H). Deoxygenated samples were used to avoid the particularly strong contribution to the T1 H of PS from paramagnetic molecular oxygen. We used T1 H as an indicator of the nanodispersion of the clay in PS. This approach correlated reasonably well with X-ray diffraction and transmission electron microscopy (TEM) data. A model for interpreting the saturation-recovery data is proposed such that two parameters relating to the dispersion can be extracted. The first parameter, f, is the fraction of the potentially available clay surface that has been transformed into polymer–clay interfaces. The second parameter is a relative measure of the homogeneity of the dispersion of these actual polymer–clay interfaces. Finally, a quick assay of T1 H is reported for samples equilibrated with atmospheric oxygen. Included are these samples as well as 28 PS/MMT nanocomposite samples prepared by extrusion. These measurements are related to the development of highthroughput characterization techniques. This approach gives qualitative indications about dispersion; however, the more time-consuming analysis, of a few deoxygenated samples from this latter set, offers significantly greater insight into the clay dispersion. A second, probably superior, rapid-analysis method, applicable to oxygen-containing samples, is also demonstrated that should yield a reasonable estimate of the f parameter. Thus, for PS/MMT nanocomposites, one has the choice of a less complete NMR assay of dispersion that is significantly faster than TEM analysis, versus a slower and more complete NMR analysis with sample times comparable to TEM, information rivaling that of TEM, and a substantial advantage that this is a bulk characterization method. © 2003 Wiley Periodicals, Inc.* J Polym Sci Part B: Polym Phys 41: 3188–3213, 200

On non-adaptive quantum chosen-ciphertext attacks and Learning with Errors

Large-scale quantum computing is a significant threat to classical public-key cryptography. In strong “quantum access” security models, numerous symmetric-key cryptosystems are also vulnerable. We consider classical encryption in a model which grants the adversary quantum oracle access to encryption and decryption, but where the latter is restricted to non-adaptive (i.e., pre-challenge) queries only. We define this model formally using appropriate notions of

On quantum chosen-ciphertext attacks and learning with errors

Quantum computing is a significant threat to classical public-key cryptography. In strong “quantum access” security models, numerous symmetric-key cryptosystems are also vulnerable. We consider classical encryption in a model which grants the adversary quantum oracle access to encryption and decryption, but where the latter is restricted to non-adaptive (i.e., pre-challenge) queries only. We define this model formally using appropriate notions of ciphertext indistinguishability and semantic security (which are equivalent by standard arguments) and call it QCCA1 in analogy to the classical CCA1 security model. Using a bound on quantum random-access codes, we show that the standard PRF-based encryption schemes are QCCA1-secure when instantiated with quantum-secure primitives. We then revisit standard IND-CPA-secure Learning with Errors (LWE) encryption and show that leaking just one quantum decryption query (and no other queries or leakage of any kind) allows the adversary to recover the full secret key with constant success probability. In the classical setting, by contrast, recovering the key requires a linear number of decryption queries. The algorithm at the core of our attack is a (large-modulus version of) the well-known Bernstein-Vazirani algorithm. We emphasize that our results should not be interpreted as a weakness of these cryptosystems in their stated security setting (i.e., post-quantum chosen-plaintext secrecy). Rather, our results mean that, if these cryptosystems are exposed to chosen-ciphertext attacks (e.g., as a result of deployment in an inappropriate real-world setting) then quantum attacks are even more devastating than classical ones

Laparoscopic Versus Open Nissen Fundoplication in Infants After Neonatal Laparotomy

BACKGROUND: Nissen fundoplication is an effective treatment of gastroesophageal reflux in infants. Laparoscopic procedures after previous laparotomy are technically more challenging. The role of laparoscopic Nissen fundoplication after neonatal laparotomy for diseases unrelated to reflux is poorly described. METHODS: This was a retrospective review of open vs laparoscopic Nissen fundoplication in infants after neonatal laparotomy. Of 32 infants who underwent neonatal laparotomy, 26 required a surgical antireflux operation within the first year of life. Twelve infants underwent laparoscopic Nissen fundoplication versus 14 infants who underwent open Nissen fundoplication. Parameters like age, weight, operative time, number of previous operations, length of stay following fundoplication, time to feedings, and complications were compared between the 2 groups. RESULTS: No statistically significant differences existed between most of the parameters compared following laparoscopic vs open Nissen fundoplication. No conversions to open procedures were necessary in infants undergoing laparoscopic fundoplication, and these infants resumed enteral feeds earlier than those who underwent the open procedure. CONCLUSION: Laparoscopic compared with open Nissen fundoplication performed in infants after a neonatal laparotomy were comparable procedures across most data points studied. However, a laparoscopic fundoplication did allow for earlier return to enteral feeds compared with the open approach. Laparoscopic Nissen fundoplication is technically feasible, safe, and effective in the treatment of gastroesophageal reflux in infants with a previous neonatal laparotomy

Thrombospondin-3 augments injury-induced cardiomyopathy by intracellular integrin inhibition and sarcolemmal instability.

Thrombospondins (Thbs) are a family of five secreted matricellular glycoproteins in vertebrates that broadly affect cell-matrix interaction. While Thbs4 is known to protect striated muscle from disease by enhancing sarcolemmal stability through increased integrin and dystroglycan attachment complexes, here we show that Thbs3 antithetically promotes sarcolemmal destabilization by reducing integrin function, augmenting disease-induced decompensation. Deletion of Thbs3 in mice enhances integrin membrane expression and membrane stability, protecting the heart from disease stimuli. Transgene-mediated overexpression of α7β1D integrin in the heart ameliorates the disease predisposing effects of Thbs3 by augmenting sarcolemmal stability. Mechanistically, we show that mutating Thbs3 to contain the conserved RGD integrin binding domain normally found in Thbs4 and Thbs5 now rescues the defective expression of integrins on the sarcolemma. Thus, Thbs proteins mediate the intracellular processing of integrin plasma membrane attachment complexes to regulate the dynamics of cellular remodeling and membrane stability

Scalable Production of Highly-Sensitive Nanosensors Based on Graphene Functionalized with a Designed G Protein-Coupled Receptor

We have developed a novel, all-electronic biosensor for opioids that consists of an engineered mu opioid receptor protein, with high binding affinity for opioids, chemically bonded to a graphene field-effect transistor to read out ligand binding. A variant of the receptor protein that provided chemical recognition was computationally redesigned to enhance its solubility and stability in an aqueous environment. A shadow mask process was developed to fabricate arrays of hundreds of graphene transistors with average mobility of ~1500 cm2 V-1 s-1 and yield exceeding 98%. The biosensor exhibits high sensitivity and selectivity for the target naltrexone, an opioid receptor antagonist, with a detection limit of 10 pg/mL.Comment: Nano Letters 201

The State of Accreditation Readiness in Georgia: A Case Study

Background: Georgia’s public health districts first began exploring the idea of national public health accreditation in 2008 when Cobb & Douglas Public Health included accreditation in their strategic plan. In May 2015, Cobb & Douglas Public Health was the first Georgia public health district to achieve national accreditation status. This article discusses the current state of accreditation readiness in Georgia and explores strengths and barriers to accreditation. Methods: This study utilized a case study approach in order to examine PHAB accreditation efforts in Georgia within a real life context. Data came from three sources: nine Accreditation Readiness Assessments, a PHAB Pre-Application Technical Assistance Survey, and state-wide Accreditation Readiness Survey. Results: The Accreditation Readiness Assessments resulted in several lessons learned about common strengths and barriers to accreditation. Strengths included a dedicated staff and supportive Boards of Health. Barriers included accreditation fees and a lack of personnel time. The PHAB Pre-application TA Survey revealed that the majority of those surveyed would recommend TA to other agencies pursuing PHAB accreditation (91%). The Accreditation Readiness Survey revealed that 14 of 18 GA public health districts are either PHAB accredited (1 district), actively pursuing PHAB accreditation (2 districts), or planning to apply (11 districts). This includes 116 of the 159 Georgia counties (73%). Conclusions: The results of this case study show that 72% of Georgia’s public health districts are engaged in accreditationrelated activities. This includes activities such as accreditation readiness assessment, community health assessment, QI council and plan development, strategic planning, and policy review

science

Research article Fostering implementation of health services research findings into practice: a consolidated framework for advancing implementatio