Spin-Vibronic Intersystem Crossing and Molecular Packing Effects in Heavy Atom Free Organic Phosphor.

We present a detailed investigation into the excited state properties of a planar symmetric azatriangulenetrione, HTANGO, which has received significant interest due to its high solid-state phosphorescence quantum yield and therefore potential as an organic room temperature phosphorescent (ORTP) dye. Using a model linear vibronic coupling Hamiltonian in combination with quantum dynamics simulations, we observe that intersystem crossing (ISC) in HTANGO occurs with a rate of ∼10 s, comparable to benzophenone, an archetypal molecule for fast ISC in heavy metal free molecules. Our simulations demonstrate that the mechanism for fast ISC is associated with the high density of excited triplet states which lie in close proximity to the lowest singlet states, offering multiple channels into the triplet manifold facilitating rapid population transfer.

Disentangling the evolution of electrons and holes in photoexcited ZnO nanoparticles.

The evolution of charge carriers in photoexcited room temperature ZnO nanoparticles in solution is investigated using ultrafast ultraviolet photoluminescence spectroscopy, ultrafast Zn K-edge absorption spectroscopy, and molecular dynamics (MD) simulations. The photoluminescence is excited at 4.66 eV, well above the band edge, and shows that electron cooling in the conduction band and exciton formation occur in <500 fs, in excellent agreement with theoretical predictions.

A Δ-learning strategy for interpretation of spectroscopic observables.

Accurate computations of experimental observables are essential for interpreting the high information content held within x-ray spectra. However, for complicated systems this can be difficult, a challenge compounded when dynamics becomes important owing to the large number of calculations required to capture the time-evolving observable. While machine learning architectures have been shown to represent a promising approach for rapidly predicting spectral lineshapes, achieving simultaneously accurate and sufficiently comprehensive training data is challenging.

Circularly polarised luminescence in an RNA-based homochiral, self-repairing, coordination polymer hydrogel.

The aqueous equimolar reaction of Ag(i) ions with the thionucleoside enantiomer (-)6-thioguanosine, ((-)6tGH), yields a one-dimensional coordination polymer {Ag(-)tG} , the self-assembly of which generates left-handed helical chains. The resulting helicity induces an enhanced chiro-optical response compared to the parent ligand. DFT calculations indicate that this enhancement is due to delocalisation of the excited state along the helical chains, with 7 units being required to converge the calculated CD spectra.

Tunable giant magnetoresistance in a single-molecule junction.

Controlling electronic transport through a single-molecule junction is crucial for molecular electronics or spintronics. In magnetic molecular devices, the spin degree-of-freedom can be used to this end since the magnetic properties of the magnetic ion centers fundamentally impact the transport through the molecules. Here we demonstrate that the electron pathway in a single-molecule device can be selected between two molecular orbitals by varying a magnetic field, giving rise to a tunable anisotropic magnetoresistance up to 93%.

Addressing the properties of "Metallo-DNA" with a Ag(i)-mediated supramolecular duplex.

The silver-nucleoside complex [Ag(i)-(3-cytidine)], , self-assembles to form a supramolecular metal-mediated base-pair array highly analogous to those seen in metallo-DNA. A combination of complementary hydrogen-bonding, hydrophobic and argentophilic interactions drive the formation of a double-helix with a continuous silver core. Electrical measurements on show that despite having Ag···Ag distances within <5% of the metallic radii, the material is electrically insulating.

Electronic effects and fundamental physics studied in molecular interfaces.

Scanning probe instruments in conjunction with a very low temperature environment have revolutionized the ability of building, functionalizing, and analysing two dimensional interfaces in the last twenty years. In addition, the availability of fast, reliable, and increasingly sophisticated methods to simulate the structure and dynamics of these interfaces allow us to capture even very small effects at the atomic and molecular level. In this review we shall focus largely on metal surfaces and organic molecular compounds and show that building systems from the bottom up and controlling the physical properties of such systems is no longer within the realm of the desirable, but has become day to day reality in our best laboratories.

Evidence for Ultralow-Energy Vibrations in Large Organic Molecules.

The quantum efficiency or the rate of conversion of incident photon to free electron in photosynthesis is known to be extremely high. It has long been thought that the origin of this efficiency are molecular vibrations leading to a very fast separation of electrons and holes within the involved molecules. However, molecular vibrations are commonly in the range above 100 meV, which is too high for excitations in an ambient environment.

Correlation of breaking forces, conductances and geometries of molecular junctions.

Electrical and mechanical properties of elongated gold-molecule-gold junctions formed by tolane-type molecules with different anchoring groups (pyridyl, thiol, amine, nitrile and dihydrobenzothiophene) were studied in current-sensing force spectroscopy experiments and density functional simulations. Correlations between forces, conductances and junction geometries demonstrate that aromatic tolanes bind between electrodes as single molecules or as weakly-conductive dimers held by mechanically-weak π - π stacking. In contrast with the other anchors that form only S-Au or N-Au bonds, the pyridyl ring also forms a highly-conductive cofacial link to the gold surface.

Highly-effective gating of single-molecule junctions: an electrochemical approach.

We report an electrochemical gating approach with ∼100% efficiency to tune the conductance of single-molecule 4,4'-bipyridine junctions using scanning-tunnelling-microscopy break junction technique. Density functional theory calculation suggests that electrochemical gating aligns molecular frontier orbitals relative to the electrode Fermi-level, switching the molecule from an off resonance state to "partial" resonance.

Single-molecule conductance of functionalized oligoynes: length dependence and junction evolution.

We report a combined experimental and theoretical investigation of the length dependence and anchor group dependence of the electrical conductance of a series of oligoyne molecular wires in single-molecule junctions with gold contacts. Experimentally, we focus on the synthesis and properties of diaryloligoynes with n = 1, 2, and 4 triple bonds and the anchor dihydrobenzo[b]thiophene (BT). For comparison, we also explored the aurophilic anchor group cyano (CN), amino (NH2), thiol (SH), and 4-pyridyl (PY).

Correlation of sonographic features of invasive ductal mammary carcinoma with age, tumor grade, and hormone-receptor status.

Purpose: To determine whether presenting sonographic features of invasive ductal carcinomas (IDC) are associated with patient age, tumor histologic grade, and hormonal receptor status.

Methods: Sonographic features of 101 consecutive cases of IDC seen at ultrasound were retrospectively assessed based on the BI-RADS criteria of posterior acoustic appearance, tumor margins, and echogenicity. Associations between sonographic features and tumor characteristics were statistically evaluated with attention to patient age.

Rare breast lesions: correlation of imaging and histologic features with WHO classification.

Mammographers occasionally are surprised by the diagnosis of a rare lesion at breast biopsy. The imaging features of some breast lesions are unfamiliar because they are rarely seen in routine mammographic practice and they are not well described or well documented in the radiologic literature. Moreover, there may be wide variation in the appearances of rare breast lesions at mammography and ultrasonography (US).

Characterization of sonographic and mammographic features of granular cell tumors of the breast and estimation of their incidence.

Objective: The purpose of this series was to review the spectrum of sonographic and mammographic features of granular cell tumors (GCTs) of the breast and to compare their frequency relative to breast carcinoma.

Methods: Ten cases of a breast GCT diagnosed during the last 13 years were analyzed for the imaging characteristics and clinical features. Sonographic images were reviewed for location, size, echogenicity, margins, height-width ratio, and sound transmission.

Mammographic surveillance after MammoSite breast brachytherapy: analysis of architectural patterns and additional interventions.

Purpose: To report the post-treatment mammographic findings of patients who received MammoSite brachytherapy at the Medical University of South Carolina (MUSC).

Materials And Methods: A total of 126 mammograms from a cohort of 38 patients who underwent MammoSite breast brachytherapy and post-treatment mammographic follow-up exclusively at MUSC are the subject of this analysis. Surveillance mammography commenced at 6 months after completion of brachytherapy and was repeated every 6 to 12 months thereafter, depending on Breast Imaging Reporting and Data System (BI-RADS) classification and further testing recommendations.

Gap-based estimation: choosing the smoothing parameters for probabilistic and general regression neural networks.

Probabilistic neural networks (PNN) and general regression neural networks (GRNN) represent knowledge by simple but interpretable models that approximate the optimal classifier or predictor in the sense of expected value of the accuracy. These models require the specification of an important smoothing parameter, which is usually chosen by cross-validation or clustering. In this article, we demonstrate the problems with the cross-validation and clustering approaches to specify the smoothing parameter, discuss the relationship between this parameter and some of the data statistics, and attempt to develop a fast approach to determine the optimal value of this parameter.

Soft-tissue tumors: value of static and dynamic gadopentetate dimeglumine-enhanced MR imaging in prediction of malignancy.

Purpose: To prospectively evaluate static and dynamic gadopentetate dimeglumine-enhanced magnetic resonance (MR) imaging relative to nonenhanced MR imaging in differentiation of benign from malignant soft-tissue lesions and to evaluate which MR imaging parameters are most predictive of malignancy, with associated interobserver variability.

Materials And Methods: One hundred forty consecutive patients (78 male patients [median age, 51 years], 62 female patients [median age, 53 years]) with a soft-tissue mass underwent nonenhanced static and dynamic contrast material-enhanced MR imaging. Diagnosis was based on histologic findings in surgical specimens (86 of 140), findings at core-needle biopsy (43 of 140), or results of all imaging procedures with clinical follow-up (11 of 140).

From the archives of the AFIP: benign musculoskeletal lipomatous lesions.

Benign lipomatous lesions involving soft tissue are common musculoskeletal masses that are classified into nine distinct diagnoses: lipoma, lipomatosis, lipomatosis of nerve, lipoblastoma or lipoblastomatosis, angiolipoma, myolipoma of soft tissue, chondroid lipoma, spindle cell lipoma and pleomorphic lipoma, and hibernoma. Soft-tissue lipoma accounts for almost 50% of all soft-tissue tumors. Radiologic evaluation is diagnostic in up to 71% of cases.

Pigmented villonodular synovitis: a disease in evolution.

Pigmented villonodular synovitis (PVNS) is a rare, benign, proliferative disease of the synovial membrane of joints, tendon sheaths, and bursas. Joint aspiration typically yields hemorrhagic or xanthochromic/serosanguinous (brown, murky) fluid. We describe a case of PVNS that presented as an acute, painless, nontraumatic right knee effusion with clear synovial fluid on arthrocentesis.

The positive predictive value of the breast imaging reporting and data system (BI-RADS) as a method of quality assessment in breast imaging in a hospital population.

Evaluation of the diagnostic performance of mammography and US in our hospital, based upon the positive predictive value (PPV) for breast cancer of the breast imaging reporting and data system (BI-RADS) final assessment categories, has been performed. A follow-up study of 2,762 mammograms was performed, along with 955 diagnostic exams and 1,807 screening exams. Additional US was performed in 655 patients (23.

Gout: a clinical and radiologic review.

Gout is a group of diseases characterized by arthritis and results from a disturbance of urate metabolism with the deposition of monosodium urate crystals in the joints and soft tissues. Often, but not invariably, the serum urate levels are elevated as a result of overproduction or underexcretion of uric acid. Clinical manifestations include acute and chronic arthritis, tophaceous deposits, interstitial renal disease, and uric acid nephrolithiasis.

FDG-PET uptake in occult acute pelvic fracture.

The role of FDG-PET in the diagnosis of bone metastases remains unsettled, although it is hoped that PET scans will add specificity to or replace bone scintigraphy. We report a case in which an acute traumatic fracture presented with a level of uptake generally considered indicative of neoplasm. It is important to recognize that increased FDG-PET activity in bone should not be accepted as definitive evidence of metastatic disease.

Musculoskeletal magnetic resonance imaging: importance of radiography.

Objective: To determine the usefulness of radiography for interpretation of musculoskeletal (MSK) magnetic resonance imaging (MRI) studies. DESIGNS AND PATIENTS: In a 1-year period, 1,030 MSK MRI studies were performed in 1,002 patients in our institution. For each study, the interpreting radiologist completed a questionnaire regarding the availability and utility of radiographs, radiological reports and clinical information for the interpretation of the MRI study.

Tax planning strategies for physicians.

The development of tax reduction strategies is a critical aspect of both corporate and personal financial planning because taxes represent the largest annual expenditure for the majority of Americans. The categories of tax reduction strategies discussed include charitable-giving techniques, ways to maximize business deductions, shifting income to family members, education tax incentives, retirement planning, and small business tax considerations. One use for these tax savings is the enhancement of a corporation's capabilities to provide services to patients.