Colloidal Nanocrystals of Lithiated Group 14 Elements

The synthesis of colloidal nanocrystals (NCs) of lithiated group 14 elements (Z=Si, Ge, and Sn) is reported, which are Li_4.4Si, Li_3.75Si, Li_4.4Ge, and Li_4.4Sn. Li_xZ compounds are highly reactive and cannot be synthesized by existing methods. The success relied on separating the surface protection from the crystal formation and using a unique passivating ligand. Bare Li_xZ crystals were first produced by milling elemental Li and Z in an argon‐filled jar. Then, under the assistance of additional milling, hexyllithium was added to passivate the freshly generated Li_xZ NCs. This ball‐milling‐assisted surface protection method may be generalized to similar systems, such as Na_xZ and K_xZ. Moreover, Li_4.4Si and Li_4.4Ge NCs were conformally encapsulated in carbon fibers, providing great opportunities for studying the potential of using Li_xZ to mitigate the volume‐fluctuation‐induced poor cyclability problem confronted by Z anodes in lithium‐ion batteries.     

D3R grand challenge 4: blind prediction of protein–ligand poses,affinity rankings,and relative binding free energies

Journal of Computer-Aided Molecular Design - The Drug Design Data Resource (D3R) aims to identify best practice methods for computer aided drug design through blinded ligand pose prediction and...     

Multiquadratic Extensions, Rigid Fields and Pythagorean Fields

Let F be a field of characteristic other than 2. Let F⁽²⁾ denotethe compositum over F of all quadratic extensions of F, letF⁽³⁾ denote the compositum over F⁽²⁾ of all quadratic extensionsof F⁽²⁾ that are Galois over F, and let F^{3} denote the compositumover F⁽²⁾ of all quadratic extensions of F⁽²⁾. This paper showsthat F⁽³⁾ = F^{3} if and only if F is a rigid field, and thatF⁽³⁾ = K⁽³⁾ for some extension K of F if and only if F is Pythagoreanand . The proofs depend mainly on the behavior of quadratic forms over quadratic extensions,and the corresponding norm maps.     

Long-term carrier-envelope phase coherence

The carrier-envelope phase of the pulse train emitted by a 10-fs mode-locked laser has been stabilized such that carrier-envelope phase coherence is maintained for at least 150 s (measurement limited). The phase coherence time was measured independently of the feedback loop.     

Imaging the neural circuitry and chemical control of aggressive motivation

Background  

With the advent of functional magnetic resonance imaging (fMRI) in awake animals it is possible to resolve patterns of neuronal activity across the entire brain with high spatial and temporal resolution. Synchronized changes in neuronal activity across multiple brain areas can be viewed as functional neuroanatomical circuits coordinating the thoughts, memories and emotions for particular behaviors. To this end, fMRI in conscious rats combined with 3D computational analysis was used to identifying the putative distributed neural circuit involved in aggressive motivation and how this circuit is affected by drugs that block aggressive behavior.     

Voice responses to changes in pitch of voice or tone auditory feedback

The present study was undertaken to examine if a subject's voice F0 responded not only to perturbations in pitch of voice feedback but also to changes in pitch of a side tone presented congruent with voice feedback. Small magnitude brief duration perturbations in pitch of voice or tone auditory feedback were randomly introduced during sustained vowel phonations. Results demonstrated a higher rate and larger magnitude of voice F0 responses to changes in pitch of the voice compared with a triangular-shaped tone (experiment 1) or a pure tone (experiment 2). However, response latencies did not differ across voice or tone conditions. Data suggest that subjects responded to the change in F0 rather than harmonic frequencies of auditory feedback because voice F0 response prevalence, magnitude, or latency did not statistically differ across triangular-shaped tone or pure-tone feedback. Results indicate the audio-vocal system is sensitive to the change in pitch of a variety of sounds, which may represent a flexible system capable of adapting to changes in the subject's voice. However, lower prevalence and smaller responses to tone pitch-shifted signals suggest that the audio-vocal system may resist changes to the pitch of other environmental sounds when voice feedback is present.     

Abdominal imaging studies: comparison of diagnostic accuracies resulting from ultrasound, computed tomography, and magnetic resonance imaging in the same individual

We retrospectively compared the diagnostic accuracy of abdominal ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) studies performed on the same individual to determine the relative performance of these modalities in the evaluation of disease processes, arising from different intra-abdominal organ systems. We retrospectively reviewed all procedure codes accrued by our abdominal imaging section during a 1-year period to determine how many patients underwent all three imaging procedures in our institution within a 2-week interval. These cases were then further evaluated to determine: (1) the primary organ system of disease involvement, (2) the final diagnosis, and (3) the imaging modality that provided the most accurate information upon which appropriate medical management was based. Imaging findings were determined by review of diagnostic reports, and medical management was determined by chart review. Two thousand six hundred-ninety five patients underwent ultrasound, 4,394 patients underwent CT, and 872 patients underwent MRI for the investigation of abdominal disease. Among these 5,126 patients, 26 underwent sequential US, CT, and MRI evaluation within a two-week interval. Appropriate clinical management was based on the US findings in 12/26 cases (46%; 95% CI: 27-67%), CT findings in 16/26 cases (62%; 95% CI: 41-80%), and MRI findings in 24 cases (92%; 95% CI: 75-99%). Significant differences in directing appropriate clinical management were found when comparing the relative diagnostic accuracies of MRI to US (p = 0.0003) and MRI to CT (p = 0.009). However, differences were not significant when comparing CT to US (p = 0.27). All final diagnoses in a given patient were accurately determined by US in 7/26 cases (27%), by CT in 10/26 cases (38%), and by MRI in 23/26 cases (88%). When analyzed according to individual diagnoses (61 total), US detected 33 of 61 (54%) abnormalities, CT detected 41 (67%) abnormalities, and MRI detected 51 (84%) abnormalities. US correctly characterized 32 (52%) abnormalities, CT correctly characterized 36 (59%) abnormalities, and MRI correctly characterized 49 (80%) abnormalities. Ultrasound, CT, and MR imaging correctly diagnosed the disease process in 3 of 12 (25%), 3 of 12 (25%), and 10 of 12 (83%) patients, respectively, with liver disease; 2 of 9 (22%), 6 of 9 (66%), and 9 of 9 (100%) patients, respectively, with pancreatic disease; 17 of 17 (100%), 8 of 17 (47%), and 10 of 17 (58%) patients, respectively, with gallbladder and biliary disease; 2 of 8 (25%), 5 of 8 (63%), and 5 of 8 (63%) patients, respectively, with renal disease; 0 of 3 (0%), 2 of 3 (66%), and 3 of 3 (100%) patients, respectively, with adrenal disease; and 8 of 12 (75%), 12 of 12 (100%), and 12 of 12 (100%) patients with free intraperitoneal fluid. Our results provide new information, regarding the relative benefits of ultrasound, CT, and MRI for the investigation of abdominal diseases at our institution. This initial data suggests that ultrasound provides the most accurate diagnoses in the investigation of gallbladder disease; MRI provides the most accurate diagnoses in the investigation of hepatic, adrenal, and pancreatic disease; and either CT or MRI may be the most appropriate first imaging study for the detection of renal disease.     

Synthesis of repeating sequence copolymers of lactic,glycolic, and caprolactic acids

Repeating sequence copolymers of poly(lactic‐co‐caprolactic acid) (PLCA), poly(glycolic‐co‐caprolactic acid) (PGCA), and poly(lactic‐co‐glycolic‐co‐caprolactic acid) (PLGCA) have been synthesized by polymerizing segmers with a known sequence in yields of 50–85% with M_ns ranging from 18–49 kDa. The copolymers exhibited well‐resolved NMR resonances indicating that the sequence encoded in the segmers used in their preparation is retained and that transesterification is minimal. The exact sequences allowed for unambiguous assignment of the NMR spectra, and these standards were compared with the data previously reported for random copolymers. The glass transition temperatures (T_gs) of the PLCA and PGCA copolymers were found to depend primarily on monomer ratio rather than sequence. Sequence dependent T_gs were, however, noted for the PLGCA polymers with 1:1:1 L:G:C ratios; poly LGC and poly GLC exhibited T_gs that differed by nearly 8 °C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Pre-Validation and Performance Prediction Using Pressure Monitoring to Evaluate HPLC Method Development Changes

HPLC methods for pharmaceutical analysis evolve from method development to commercial product testing. The majority of development and validation takes place in an R&D setting, followed by transfer to commercial sites that execute test methods on a routine basis. There is a growing need to increase confidence and probability that developed methods will be successful both during validation and long-term use with products, particularly when introducing new or unfamiliar technologies. An HPLC method pre-validation and performance prediction plan is presented using model pharmaceutical ingredients in prototype liquid formulations. The pre-validation includes limited linearity, repeatability in sample matrix, precision, carry-over, and selectivity. The performance prediction involves injecting large numbers of worst-case samples and monitoring five critical parameters: retention time, tailing factor, resolution, efficiency, and system pressure. Parameter results are assessed with respect to precision and/or system performance. In a proof of principle model, the performance prediction data demonstrate that system suitability parameters remain constant during injections of prepared samples; however, the system pressure increases over time. These underlying data indicate a potential trend prior to method validation. As a result, sample preparation and HPLC condition modifications are evaluated using pressure plots as a key performance metric.

     

Fluoridolysis of 5,6-epoxy carbohydrates: application to the synthesis of 5-fluoro lactosamine and isolactosamine glycosides

The synthesis of 6-selenophenyl derivatives of β-1,3 and β-1,4 disaccharides has been explored for the purpose of extending our epoxide fluoridolysis methodology to the synthesis of 5-fluoro analogues of N-acetyl isolactosamine (isoLacNAc, lacto-N-biose) and N-acetyl lactosamine (LacNAc) glycosides. Successful synthesis of the C-6 selenium-containing disaccharides was achieved via Lewis acid-mediated donor and acceptor substrates, the latter containing a selectively protected C-6 hydroxyl group for ultimate conversion to the desired 6-selenophenyl disaccharides. In contrast, the use of selenium-containing acceptor substrates under a variety of conditions failed to yield the desired selenium-containing disaccharides. Oxidation of the 6-selenophenyl derivatives to the corresponding selenoxides followed by thermal elimination yielded the exocyclic olefins, which were converted to the 5,6-epoxides. Epoxide fluoridolysis yielded the desired target compounds, 5-fluoro β-octyl glycoside analogues of type 1 and type 2 glycans. The newly synthesized fluorine-containing disaccharides have potential application as fucosyltransferase substrates, both for mechanistic studies and in the chemoenzymatic synthesis of fluorine-containing oligosaccharides.