Disparities of Single-Particle Growth Rates in Buried Versus Exposed Ritonavir Crystals within Amorphous Solid Dispersions.

Seeded growth rates of ritonavir in copovidone at 75% relative humidity (RH) and 50 °C were evaluated by single-particle tracking second harmonic generation (SHG) microscopy and found to be ∼3-fold slower for crystallites at the surface compared to the bulk. The shelf lives of final dosage forms containing amorphous solid dispersions (ASDs) are often dictated by the rates of active pharmaceutical ingredient crystallization. Upon exposure to elevated RH, the higher anticipated water content near the surfaces of ASDs has the potential to substantially impact nucleation and growth kinetics relative to the bulk. However, quantitative assessment of these differences in growth rates is complicated by challenges associated with discrimination of the two contributions (supersaturation and molecular mobility) in ensemble-averaged measurements. In the present study, "sandwich" materials were prepared, in which sparse populations of ritonavir single-crystalline seeds were pressed between two similar ASD films to assess bulk crystallization rates. These sandwich materials were compared and contrasted with analogously prepared "open-faced" samples, without the capping film, to assess the surface crystallization rates. Single-particle analysis by SHG microscopy time-series during in situ crystallization produced average growth rates of 3.8 µm/h for bulk columnar crystals with a particle-to-particle standard deviation of 0.9 µm/h. In addition, columnar crystal growth rates for surface particles were measured to be 1.3 µm/h and radiating crystal growth rates for surface particles were measured to be 1.0 µm/h, both with a particle-to-particle deviation of 0.4 µm/h. The observed appearance of radiating crystals upon surface seeding is attributed to reduced ritonavir solubility upon water adsorption at the interface, leading to higher defect densities in crystal growth. Despite substantial differences in crystal habit, correction of the surface growth rates by a factor of 4 from geometric effects resulted in relatively minor but statistically significant differences in the growth kinetics for the two local environments. These results are consistent, with viscosity being a relatively weak function of water absorption coupled with primarily diffusion-limited growth kinetics.

In Situ Crystal Growth Rate Distributions of Active Pharmaceutical Ingredients.

Single-particle tracking of crystal growth performed in situ enables substantial improvements in the signal-to-noise ratio (SNR) for recovered crystal nucleation and growth rates by nonlinear optical microscopy. Second harmonic generation (SHG) is exquisitely sensitive to noncentrosymmetric crystals, including those produced by many homochiral active pharmaceutical ingredients (APIs). Accelerated stability testing at elevated temperatures and relative humidity informs design of pharmaceutical formulations. In the present work, we demonstrate reduction in the Poisson noise associated with the finite number of particles present in a given field of view through continuous monitoring during stability testing. Single-particle tracking enables recovery of crystal growth rates of individual crystallites and enables unambiguous direct detection of nucleation events. Collectively, these capabilities provide significant improvements in the signal-to-noise for nucleation and crystal growth measurements, corresponding to approximately an order of magnitude reduction in anticipated measurement time for recovery of kinetics parameters.

Iterative Non-Negative Matrix Factorization Filter for Blind Deconvolution in Photon/Ion Counting.

A digital filter based on non-negative matrix factorization (NMF) enables blind deconvolution of temporal information from large data sets, simultaneously recovering both photon arrival times and the instrument impulse response function (IRF). In general, the measured digital signals produced by modern analytical instrumentation are convolved by the corresponding IRFs, which can complicate quantitative analyses. Common examples include photon counting (PC), chromatography, super resolution imaging, fluorescence imaging, and mass spectrometry. Scintillation counting, in particular, provides a signal-to-noise advantage in measurements of low intensity signals, but has a limited dynamic range due to pulse overlap. This limitation can complicate the interpretation of data by masking temporal and amplitude information on the underlying detected signal. Typical methods for deconvolution of the photon events require advanced knowledge of the IRF, which is not generally trivial to obtain. In this work, a sliding window approach was developed to perform NMF one pixel at a time on short segments of large (e.g., 25 million point) data sets. Using random initial guesses for the IRF, the NMF filter simultaneously recovered both the deconvolved photon arrival times and the IRF. Applying the NMF filter to the analysis of triboluminescence (TL) data traces of active pharmaceutical ingredients enabled discrimination between different hypothesized physical origins of the signal.

Crystallographic Insights into the Behavior of Highly Acidic Metal Cations in Ionic Liquids from Reactions of Titanium Tetrachloride with [1-Butyl-3-Methylimidazolium][X] Ionic Liquids (X = Chloride, Bromide, Tetrafluoroborate).

Highly charged metal ions are difficult to investigate in weakly coordinating ionic liquids (ILs) because of the insolubility of their solid forms, but the molecular liquid TiCl4 offers a way to react tetravalent metal ions in an IL. Reactions of TiCl4 with 1-butyl-3-methylimidazolium ([C4mim]+)-based ILs containing chloride or bromide lead to mixtures of highly metastable amorphous solids and small amounts of crystalline chlorotitanate salts including [C4mim]2[TiCl6] and two polymorphs of [C4mim]2[Ti2Cl10] in a manner not well correlated with stoichiometry or anion identity. The reaction of TiCl4 with [C4mim][BF4] yields crystals of the mixed fluoro-chloro complex [C4mim]2[Ti4F6Cl12], indicating spontaneous reaction of the IL ions to generate HF in situ. These unusual behaviors are explained in terms of the exceptionally high acidity of Ti4+ and the unusual behavior of TiCl4 among metal halides as a nonpolar molecular compound.

Triboluminescence from Pharmaceutical Formulations.

Triboluminescence (TL) is shown to enable selective detection of trace crystallinity within nominally amorphous solid dispersions (ASDs). ASDs are increasingly used for the preparation of pharmaceutical formulations, the physical stability of which can be negatively impacted by trace crystallinity introduced during manufacturing or storage. In the present study, TL measurements of a model ASD consisting of griseofulvin in polyethylene glycol produced limits of detection of 140 ppm. Separate studies of the particle size dependence of sucrose crystals and the dependence on polymorphism in clopidogrel bisulfate particles are both consistent with a mechanism for TL closely linked to the piezoelectric response of the crystalline fraction. Whereas disordered polymeric materials cannot support piezoelectric activity, molecular crystals produced from homochiral molecules adopt crystal structures that are overwhelmingly symmetry-allowed for piezoelectricity. Consequently, TL may provide a broadly applicable and simple experimental route for sensitive detection of trace crystallinity within nominally amorphous materials.

Impact and educational outcomes of a small group self-directed teaching strategy in a clinical neuroscience curriculum.

The complexity of the material being taught in clinical neuroscience within the medical school curriculum requires creative pedagogies to teach medical students effectively. Many clinical teaching strategies have been developed and are well described to address these challenges. However, only a few have been evaluated to determine their impact on the performance of students studying clinical neuroscience. Interactive, 2-hour, self-directed small-group interactive clinical case-based learning sessions were conducted weekly for 4 weeks to integrate concepts learned in the corresponding didactic lectures. Students in the small groups analyzed cases of patients suffering from neurological disease that were based on eight learning objectives that allowed them to evaluate neuroanatomical data and clinical findings before presenting their case analysis to the larger group. Students' performances on the formative quizzes and summative tests were compared to those of first-year medical students in the previous year for whom the self-directed, small-group interactive clinical sessions were not available. There was a significant improvement in the summative performance of first-year medical students with self-directed clinical case learning in the second year (Y2) of teaching clinical neuroscience (P < 0.05) when compared with first-year students in the first year (Y1) for whom the self-directed learning approach was not available. Student performance in the formative assessments between Y1 and Y2 was not significantly different (P = 0.803). A target of ≥70% student scoring above 80% in the final summative examination was met. The current study revealed evidence for the impact and educational outcomes of a self-directed, clinical teaching strategy in a clinical neuroscience curriculum for first-year medical students. Anat Sci Educ 11: 478-487. © 2017 American Association of Anatomists.

Crystal structure of Zn(ZnCl4)2(Cho)2: the transformation of ions to neutral species in a deep eutectic system.

A neutral molecular complex, Zn(ZnCl4)2(Cho)2, has been isolated from the well-known choline chloride/ZnCl2 deep eutectic system (DES) and its crystal structure has been determined. The structure demonstrates the possibility of isolating unusual coordination complexes from DES which departs from the well-established observation of such systems being formed from large, ionic metal complexes or oligomers.

Road map to esophagectomy for nurses.

Esophageal cancer, although considered uncommon in the United States, continues to exhibit increased incidence. Esophageal cancer now ranks seventh among cancers in mortality for men in the United States. Even as treatment continues to advance, the mortality rate remains high, with a 5-year survival rate less than 35%. Esophageal cancer typically is discovered in advanced stages, which reduces the treatment options. When disease is locally advanced, esophagectomy remains the standard for treatment. Surgery remains challenging and complicated. Multiple surgical approaches are available, with the choice determined by tumor location and stage of disease. Recovery is often fraught with complications-both physical and emotional. Nursing care revolves around complex care managing multiple body systems and providing effective education and emotional support for both patients and patients' families. Even after recovery, local recurrence and distant metastases are common. Early diagnosis, surgical advancement, and improvements in postoperative care continue to improve outcomes.

Synthesis and X-ray structure determination of highly active Pd(II), Pd(I), and Pd(0) complexes of di(tert-butyl)neopentylphosphine (DTBNpP) in the arylation of amines and ketones.

The air-stable complex Pd(η(3)-allyl)(DTBNpP)Cl (DTBNpP = di(tert-butyl)neopentylphosphine) serves as a highly efficient precatalyst for the arylation of amines and enolates using aryl bromides and chlorides under mild conditions with yields ranging from 74% to 98%. Amination reactions of aryl bromides were carried out using 1-2 mol % Pd(η(3)-allyl)(DTBNpP)Cl at 23-50 °C without the need to exclude oxygen or moisture. The C-N coupling of the aryl chlorides occurred at relatively lower temperature (80-100 °C) and catalyst loading (1 mol %) using the Pd(η(3)-allyl)(DTBNpP)Cl precatalyst than the catalyst generated in situ from DTBNpP and Pd(2)(dba)(3) (100-140 °C, 2-5 mol % Pd). Other Pd(DTBNpP)(2)-based complexes, (Pd(DTBNpP)(2) and Pd(DTBNpP)(2)Cl(2)) were ineffective precatalysts under identical conditions for the amination reactions. Both Pd(DTBNpP)(2) and Pd(DTBNpP)(2)Cl(2) precatalysts gave nearly quantitative conversions to the product in the α-arylation of propiophenone with p-chlorotoluene and p-bromoanisole at a substrate/catalyst loading of 100/1. At lower substrate/catalyst loading (1000/1), the conversions were lower but comparable to that of Pd(t-Bu(3)P)(2). In many cases, the tri-tert-butylphosphine (TTBP) based Pd(I) dimer, [Pd(µ-Br)(TTBP)](2), stood out to be the most reactive catalyst under identical conditions for the enolate arylation. Interestingly, the air-stable Pd(I) dimer, Pd(2)(DTBNpP)(2)(µ-Cl)(µ-allyl), was less active in comparison to [Pd(µ-Br)(TTBP)](2) and Pd(η(3)-allyl)(DTBNpP)Cl. The X-ray crystal structures of Pd(η(3)-allyl)(DTBNpP)Cl, Pd(DTBNpP)(2)Cl(2), Pd(DTBNpP)(2), and Pd(2)(DTBNpP)(2)(µ-Cl)(µ-allyl) are reported in this paper along with initial studies on the catalyst activation of the Pd(η(3)-allyl)(DTBNpP)Cl precatalyst.

A comparison of manual guidance and knowledge of results in the learning of a weight-bearing skill.

BACKGROUND AND PURPOSE: Patients with certain neurological or orthopedic conditions often present with asymmetrical weight-bearing in stance. In the treatment of such patients, physical therapists often use manual guidance to promote symmetrical weight-bearing. Research investigating the efficacy of manual guidance to effect a change in weight-bearing status however, is lacking. As a first step in assessing the utility of such guidance, the present study compared the effect of providing two frequencies of manual guidance and of knowledge of results (KR) in the learning of a weight-bearing skill in healthy subjects. SUBJECTS AND METHODS: Forty healthy subjects (20 males and 20 females) with a mean age of 21.8 years (SD = 4.9 years) were randomly assigned to one of four groups differentiated on the basis of the type and frequency of information provided for learning. Subjects were required to learn to distribute their weight on their feet at a 70:30 ratio. Following a pretest, one group of subjects was positioned by experimenter-provided manual guidance at the hips until 70% of their weight was on one foot, as determined by a bathroom scale. This guidance was provided on every trial for 10 blocks of 12 trials (GD100%). A second group was provided with guidance on every third trial (GD33%), with the other two trials being performed without any assistance. A third group was verbally provided with KR regarding the percentage of body weight on the test foot after every trial (KR100%) while the final group was given KR after every third trial (KR33%). Following acquisition, retention tests were performed 10 minutes, one day, and one week later during which no feedback or guidance was given. RESULTS: No difference between groups was found at the pretest, but an analysis of variance performed on the accuracy of achieving the 70% goal in retention revealed main effects for technique and frequency. These effects were overshadowed by a significant interaction of these variables with retention test. Analysis of this interaction revealed that the most accurate performance was exhibited by the KR33% group while the GD100% group consistently exhibited the poorest learning. The GD33% and KR100% groups showed a decrease in performance accuracy with time following practice. DISCUSSION AND CONCLUSION: These results indicate that infrequent KR was the most effective technique in learning to modify weight-bearing status and that frequent manual guidance during practice is ineffective for learning this task. The next step is to determine whether these findings hold in subjects with various orthopedic and neurological conditions.

Choline-derivative-based ionic liquids.

A total of sixty-three choline derivative-based ionic liquids in the forms of chlorides, acesulfamates, and bis(trifluoromethylsulfonyl)imides have been prepared and their physical properties (density, viscosity, solubility, and thermal stability) have been determined. Thirteen of these salts are known chlorides: precursors to the 26 water-soluble acesulfamates, 12 acesulfamates only partially miscible with water, and 12 water-insoluble imides. The crystal structures for two of the chloride salts-(2-hydroxyethyl)dimethylundecyloxymethylammonium chloride and cyclododecyloxymethyl(2-hydroxyethyl)dimethylammonium chloride-were determined. The antimicrobial (cocci, rods, and fungi) activities of the new hydrophilic acesulfamate-based ILs were measured and 12 were found to be active. The alkoxymethyl(2-hydroxyethyl)dimethylammonium acesulfamates have been shown to be insect feeding deterrents and thus open up a new generation of synthetic deterrents based on ionic liquids. The alkoxymethyl(2-decanoyloxyethyl)dimethylammonium bis(trifluoromethylsulfonyl)imides have also been shown to act as fixatives for soft tissues and can furthermore be used as substitutes for formalin and also preservatives for blood.

Interactions of 1-methylimidazole with UO2(CH3CO2)2 and UO2(NO3)2: structural, spectroscopic, and theoretical evidence for imidazole binding to the uranyl ion.

The first definitive high-resolution single-crystal X-ray structure for the coordination of the 1-methylimidazole (Meimid) ligand to UO2(Ac)2 (Ac = CH3CO2) is reported. The crystal structure evidence is confirmed by IR, Raman, and UV-vis spectroscopic data. Direct participation of the nitrogen atom of the Meimid ligand in binding to the uranium center is confirmed. Structural analysis at the DFT (B3LYP) level of theory showed a conformational difference of the Meimid ligand in the free gas-phase complex versus the solid state due to small energetic differences and crystal packing effects. Energetic analysis at the MP2 level in the gas phase supported stronger Meimid binding over H2O binding to both UO2(Ac)2 and UO2(NO3)2. In addition, self-consistent reaction field COSMO calculations were used to assess the aqueous phase energetics of combination and displacement reactions involving H2O and Meimid ligands to UO2R2 (R = Ac, NO3). For both UO2(NO3)2 and UO2(Ac)2, the displacement of H2O by Meimid was predicted to be energetically favorable, consistent with experimental results that suggest Meimid may bind uranyl at physiological pH. Also, log(Knitrate/KAc) calculations supported experimental evidence that the binding stoichiometry of the Meimid ligand is dependent upon the nature of the reactant uranyl complex. These results clearly demonstrate that imidazole binds to uranyl and suggest that binding of histidine residues to uranyl could occur under normal biological conditions.

The opposite effect of temperature on polyethylene glycol-based aqueous biphasic systems versus aqueous biphasic extraction chromatographic resins.

Variation in operational temperatures has revealed differences in the partitioning behavior of probe solutes between the phases in aqueous biphasic systems (ABS) and the related aqueous biphasic extraction chromatographic resin (ABEC). This difference has been studied using the hydrophobic anion, 99TcO4-, as a probe and (NH4)2SO4 as the kosmotropic salt. Distribution of the hydrophobic anion 99TcO4- to the PEG-rich phase in a MePEG-5000/(NH4)2SO4 ABS increases with increasing temperature, but decreases are observed in batch uptakes of this anion to ABEC resins from (NH4)2SO4 solutions. Phase diagrams were constructed at five different temperatures from 10 to 50 degreesC using cloud point titration for the ABS and a correlation between the phase divergence, measured in terms of tie line length (TLL), and the temperature of the partitioning system was verified. Thermodynamic parameters (deltaHdegrees,deltaSdegrees, deltaGdegrees, ) as a function of temperature were calculated for the various systems studied and the results imply thermodynamic differences between partitioning in ABS versus ABEC.

Factors controlling metal-ion selectivity in the binding sites of calcium-binding proteins. The metal-binding properties of amide donors. A crystallographic and thermodynamic study.

The metal-ion complexing properties of the ligand EDTAM (ethylenediamine-N,N,N',N'-tetraacetamide) are investigated as a model for the role of amide oxygen donors in the binding sites of Ca-binding proteins. The structures of the complexes [Ca(EDTAM)NO3]NO3 (1), [La(EDTAM)(H2O)4](NO3)3.H2O (2), and [Cd(EDTAM)(NO3)]NO3 (3) are reported: 1 monoclinic, P2(1)/c, a = 10.853(2) angstroms, b = 12.893(3) angstroms, c = 13.407(3) angstroms, beta = 103.28(3) degrees, Z = 4, R = 0.0281; 2 triclinic, P, a = 8.695(2) angstroms, b = 9.960(2) angstroms, c = 16.136(3) angstroms, alpha = 95.57(3) degrees, beta = 94.84(3) degrees, gamma = 98.72(3) degrees, Z = 2, R = 0.0394; 3 monoclinic, P2(1)/c, a = 10.767(2) angstroms, b = 12.952(2) angstroms, c = 13.273(2) angstroms, beta = 103.572(3) degrees, Z = 4, R = 0.0167. Compounds 1 and 3 are isostructural, and the EDTAM binds to the metal ion through its two N-donors and four O-donors from the amide groups. Ca(II) in 1 is 8-coordinate with a chelating NO3- group, while Cd(II) in 3 may possibly be 7-coordinate, with an asymmetrically coordinated NO3- that is best regarded as unidentate. The La(III) in 2 is coordinated to the EDTAM in a manner similar to that of 1 and 3, but it is 10-coordinate with four water molecules coordinated to the La(III). The formation constants (log K1) for complexes of a variety of metal ions with EDTAM are reported in 0.1 M NaNO3 at 25.0 +/- 0.1 degrees C. These are compared to the log K1 values for en (ethylenediamine) and THPED (N,N,N',N'-tetrakis(2-hydroxypropyl)-ethylenediamine). For large metal ions, such as Ca2+ or La3+, log K1 increases strongly when the four acetamide groups are added to en to give EDTAM, whereas for a small metal ion, such as Mg2+, this increase is small. The log K1 values for EDTAM compared to THPED suggest that the amide oxygen is a much stronger base than the alcoholic oxygen. Structures of binding sites in 40 Ca-binding proteins are examined. It is shown that the Ca-O=C bond angles involving coordinated amides in these sites are large, commonly being in the 150-180 degrees range. This is discussed in terms of the idea that for purely ionic bonding the M-O=C bond angle will approach 180 degrees, while for covalent bonding the angle should be closer to 120 degrees. How this fact might be used by the proteins to control selectivity for different metal ions is discussed.

Exploiting isolobal relationships to create new ionic liquids: novel room-temperature ionic liquids based upon (N-alkylimidazole)(amine)BH2+"boronium" ions.

Readily prepared imidazole-based boronium ions form stable, hydrophobic, room-temperature ionic liquids (RTIL) with unique electronic and spectroscopic characteristics.

Effects of speciation on partitioning of iodine in aqueous biphasic systems and onto ABEC resins.

Polyethylene glycol (PEG)-aqueous biphasic systems (ABS) and PEG-grafted aqueous biphasic extraction chromatographic (ABEC) resins have been shown to remove inorganic species from environmental and nuclear wastes. The partitioning behavior of several iodide species (iodide, iodine, triiodide, iodate, and 4-iodo-2,6-dimethylphenol (I-DMP)) have been studied for PEG (MW 2000)-salt systems and ABEC resins. Iodide partitioning to PEG-rich phases or onto ABEC resins can be enhanced by derivatization with 2,6-dimethylphenol to form 4-iodo-2,6-dimethylphenol or by addition of I(2) to form triiodide. Conversely, iodide partitioning to the PEG-rich phase or onto ABEC resins is reduced by oxidation of iodide to IO(3)(-). Partitioning studies of iodide, iodate, and iodine in a PEG-ABS are compared to results using ABEC resins.