Distinctive g-Factor of Moiré-Confined Excitons in van der Waals Heterostructures

We investigated the valley Zeeman splitting of excitonic peaks in the microphotoluminescence (μPL) spectra of high-quality hBN/WS₂/MoSe₂/hBN heterostructures under perpendicular magnetic fields up to 20 T. We identify two neutral exciton peaks in the μPL spectra; the lower-energy peak exhibits a reduced g-factor relative to that of the higher energy peak and much lower than the recently reported values for interlayer excitons in other van der Waals (vdW) heterostructures. We provide evidence that such a discernible g-factor stems from the spatial confinement of the exciton in the potential landscape created by the moiré pattern due to lattice mismatch or interlayer twist in heterobilayers. This renders magneto-μPL an important tool to reach a deeper understanding of the effect of moiré patterns on excitonic confinement in vdW heterostructures.

Zitterbewegung of Moiré Excitons in Twisted MoS_{2}/WSe_{2} Heterobilayers

The moiré pattern observed in stacked noncommensurate crystal lattices, such as heterobilayers of transition metal dichalcogenides, produces a periodic modulation of their band gap. Excitons subjected to this potential landscape exhibit a band structure that gives rise to a quasiparticle dubbed the moiré exciton. In the case of MoS_{2}/WSe_{2} heterobilayers, the moiré trapping potential has honeycomb symmetry and, consequently, the moiré exciton band structure is the same as that of a Dirac-Weyl fermion, whose mass can be further tuned down to zero with a perpendicularly applied field. Here we show that, analogously to other Dirac-like particles, the moiré exciton exhibits a trembling motion, also known as Zitterbewegung, whose long timescales are compatible with current experimental techniques for exciton dynamics. This promotes the study of the dynamics of moiré excitons in van der Waals heterostructures as an advantageous solid-state platform to probe Zitterbewegung, broadly tunable by gating and interlayer twist angle.

Gap opening in graphene nanoribbons by application of simple shear strain and in-plane electric field

The effects of shear strain and applied in plane electric field on the electronic properties of monolayer graphene nanoribbons (GNRs) are theoretically investigated. Band structures and the probability densities are calculated within the tight-binding model and the mechanical stresses submitted to the GNRs are taken into account by using the theory of linear elasticity with joint modifications in the elongation of the nearest-neighbor vectors and the modification of the hopping parameters. The energy gaps for specific widths of (semiconducting) armchair nanoribbons are verified also in the presence of either strain or field, whereas zigzag nanoribbons are metallic for any value of strain and exhibit a small gap for any value of field. However, our results demonstrate that when both strain and electric field are combined, a significant energy gap is always observed in the band structure, for any width or edge type of the ribbon. Moreover, the obtained total wave function is asymmetric along the ribbon width due to the applied electric field that pushes the electrons to one side of the ribbon and, under shear strain, a peak at the center of the ribbon in the spatial distribution is also observed owing to the preferable localization around the almost undeformed carbon bonds at ribbon center.

Magnetic field induced vortices in graphene quantum dots

The energy spectrum and local current patterns in graphene quantum dots (QD) are investigated for different geometries in the presence of an external perpendicular magnetic field. Our results demonstrate that, for specific geometries and edge configurations, the QD exhibits vortex and anti-vortex patterns in the local current density, in close analogy to the vortex patterns observed in the probability density current of semiconductor QD, as well as in the order parameter of mesoscopic superconductors.

P852 Cancer-associated thrombotic diathesis: one of your worst nightmares

A 34-year-old male patient was diagnosed with undifferentiated sarcoma of the right thigh, with lung metastasis. He underwent primary lesion resection surgery and initiated chemotherapy with both doxorubicin and ifosfamide. Though primary tumor burden was substantially reduced, secondary lesions were found to be irresponsive to drug therapy, leading to regimen switching to both gemcitabine and docetaxel. Three months later, patient started complaining of atypical chest pain and palpitations. Electrocardiography revealed very frequent supraventricular ectopic complexes, while a transthoracic echocardiogram unveiled a pulmonary vein thrombus, which extended into the left atrium. This finding, which was further characterized by cardiovascular magnetic resonance imaging, prompted anticoagulation initiation, under the form of enoxaparin 1mg/kg bid. At this time, chemotherapeutic scheme was, again, swapped, and a cycle of both doxorubicin and olaratumab was introduced. A combined episode of inferolateral ST-segment elevation myocardial infarction and peripheral arterial embolism followed shortly thereafter. Emergent invasive coronary angiogram revealed no signs of both epicardial atherosclerosis and thrombus, whereas subsequent transthoracic echocardiography showed a massive left heart thrombus, extending into the aortic valve annulus. Anti-thrombotic approach involved increasing enoxaparin dosage to 1.5mg/kg bid but no fibrinolytic therapy. Despite a rather uneventful immediate clinical course, with no electric or hemodynamic instability and no limb-threatening ischemia, lamentably, patient died two weeks later, before thrombus definitive imaging reassessment. As no autopsy was performed, it is unclear whether a cardiovascular acute event or neoplasm inexorable progression is to blame as the primary cause of death.

Thrombosis is a common, costly and potentially fatal cancer complication. Patients receiving systemic chemotherapy for advanced diseased are at higher risk. Despite major management developments in the past fifteen years, evidence still supports traditional low-molecular-weight heparins as the first-line therapy and prognosis remains dismal.

Abstract P852 Figure.

Valley filtering in graphene due to substrate-induced mass potential

The interaction of monolayer graphene with specific substrates may break its sublattice symmetry and results in unidirectional chiral states with opposite group velocities in the different Dirac cones (Zarenia et al 2012 Phys. Rev. B 86 085451). Taking advantage of this feature, we propose a valley filter based on a transversal mass kink for low energy electrons in graphene, which is obtained by assuming a defect region in the substrate that provides a change in the sign of the substrate-induced mass and thus creates a non-biased channel, perpendicular to the kink, for electron motion. By solving the time-dependent Schrödinger equation for the tight-binding Hamiltonian, we investigate the time evolution of a Gaussian wave packet propagating through such a system and obtain the transport properties of this graphene-based substrate-induced quantum point contact. Our results demonstrate that efficient valley filtering can be obtained, provided: (i) the electron energy is sufficiently low, i.e. with electrons belonging mostly to the lowest sub-band of the channel, and (ii) the channel length (width) is sufficiently long (narrow). Moreover, even though the transmission probabilities for each valley are significantly affected by impurities and defects in the channel region, the valley polarization in this system is shown to be robust against their presence.

Electronic properties of superlattices on quantum rings

We present a theoretical study of the one-electron states of a semiconductor-made quantum ring (QR) containing a series of piecewise-constant wells and barriers distributed along the ring circumference. The single quantum well and the superlattice cases are considered in detail. We also investigate how such confining potentials affect the Aharonov-Bohm like oscillations of the energy spectrum and current in the presence of a magnetic field. The model is simple enough so as to allow obtaining various analytical or quasi-analytical results. We show that the well-in-a-ring structure presents enhanced localization features, as well as specific geometrical resonances in its above-barrier spectrum. We stress that the superlattice-in-a-ring structure allows giving a physical meaning to the often used but usually artificial Born-von-Karman periodic conditions, and discuss in detail the formation of energy minibands and minigaps for the circumferential motion, as well as several properties of the superlattice eigenstates in the presence of the magnetic field. We obtain that the Aharonov-Bohm oscillations of below-barrier miniband states are reinforced, owing to the important tunnel coupling between neighbour wells of the superlattice, which permits the electron to move in the ring. Additionally, we analysis a superlattice-like structure made of a regular distribution of ionized impurities placed around the QR, a system that may implement the superlattice in a ring idea. Finally, we consider several random disorder models, in order to study roughness disorder and to tackle the robustness of some results against deviations from the ideally nanostructured ring system.

Electronic confinement in graphene quantum rings due to substrate-induced mass radial kink

We investigate localized states of a quantum ring confinement in monolayer graphene defined by a circular mass-related potential, which can be induced e.g. by interaction with a substrate that breaks the sublattice symmetry, where a circular line defect provides a change in the sign of the induced mass term along the radial direction. Electronic properties are calculated analytically within the Dirac-Weyl approximation in the presence of an external magnetic field. Analytical results are also compared with those obtained by the tight-binding approach. Regardless of its sign, a mass term [Formula: see text] is expected to open a gap for low-energy electrons in Dirac cones in graphene. Both approaches confirm the existence of confined states with energies inside the gap, even when the width of the kink modelling the mass sign transition is infinitely thin. We observe that such energy levels are inversely proportional to the defect line ring radius and independent on the mass kink height. An external magnetic field is demonstrated to lift the valley degeneracy in this system and easily tune the valley index of the ground state in this system, which can be polarized on either K or [Formula: see text] valleys of the Brillouin zone, depending on the magnetic field intensity. Geometrical changes in the defect line shape are considered by assuming an elliptic line with different eccentricities. Our results suggest that any defect line that is closed in a loop, with any geometry, would produce the same qualitative results as the circular ones, as a manifestation of the topologically protected nature of the ring-like states investigated here.

Abstract P5-01-08: Changes induced by neoadjuvant chemotherapy (NCT) in breast cancer tumor infiltrating lymphocytes (TIL) subpopulations are associated with chemo-sensitivity and prognosis

Background: Recent data support the modulation of immune response in breast cancer microenvironment by neoadjuvant chemotherapy. This immune modulation might favor treatment response and modify post-treatment tumor immunosurveillance. The association of TIL with outcome after breast cancer (BC) NCT has also been suggested by several studies. Thereby, the differences in NCT-induced immune changes could reflect different profiles of immune modulation and translate into diverse prognosis. The objective of our study was to evaluate the predictive and prognostic value of NCT-induced TIL changes in patients with BC.

Methods: We analyzed a series of consecutive breast cancer patients treated with sequential anthracyclines and taxanes NCT (80.4% sequential AC-docetaxel). Pre- and post-chemotherapy biopsies were included in a tissue microarray and immunohistochemical (IHC) staining was performed for CD3, CD4, CD8, CD20, FOXP3 and CD68. After slide scanning and acquisition of digital images, computerized morphometric analysis (TIL count/mm2) was performed with ImageJ (NIH) software. Variations on pre- and post-NCT TIL infiltration were quantified and expressed as the absolute difference in number of cells/mm2 (postNCT TIL – preNCT TIL); median values were used as cut-point. Association of TIL changes with pCR was evaluated by logistic regression models. Kaplan-Meier analysis and Cox proportional hazard models were used for survival

Results: 121 patients with a diagnosis of invasive BC were included. Stages: IIB (28%), IIIA-C (56.4%). Phenotype was determined by immunohistochemistry: 50.4% Her2- hormone-sensitive (HS), 13.2% Her2+ HS, 10.7% Her2+ non-HS, and 21.5% triple negative. Pathologic complete response (pCR) rate was 17.4%. NCT produced a decrease in tumor infiltration by CD4 (p = 0.01), CD20 (p = 0.04) and CD68 (p = 0.03) and an increase in CD8 infiltrating lymphocytes (p = 0.0001). NCT-induced decreases of TIL infiltration above the median level of change were associated with pCR: CD3 (p = 0.01; odds ratio [OR]: 0.12, 95% confidence interval [95%CI] 0.02-0.63), CD4 (p = 0.02; OR 0.2; 95%CI 0.05-0.85) and CD20 (p = 0.01; OR 0.15; 95%CI 0.03-0.64). With a median follow-up of 60 months, median overall survival (OS) and disease free survival (DFS) has not been reached. A NCT-induced CD3 decrease higher than the median cut-off independently predicted higher DFS (hazard ratio [HR]:6.56; 95%CI 1.3-33.2; p = 0,02) and OS (HR:9.85; 95%CI 1.03-93.7, p = 0.04).

Conclusions: TIL variations induced by chemotherapy are related to pRC and prognosis in patients with invasive BC receiving anthracyclines and taxanes. These results suggest that the degree of immune modulation by NCT has an impact on survival and might be useful for prognostic classification in the setting of BC treated with NCT [Supported by GEICAM-Beca Ana Balil].

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-01-08.

Conductance maps of quantum rings due to a local potential perturbation

We performed a numerical simulation of the dynamics of a Gaussian shaped wavepacket inside a small sized quantum ring, smoothly connected to two leads and exposed to a perturbing potential of a biased atomic force microscope tip. Using the Landauer formalism, we calculated conductance maps of this system in the case of single and two subband transport. We explain the main features in the conductance maps as due to the AFM tip influence on the wavepacket phase and amplitude. In the presence of an external magnetic field, the tip modifies the ϕ0 periodic Aharonov-Bohm oscillation pattern into a ϕ0/2 periodic Al'tshuler-Aronov-Spivak oscillation pattern. Our results in the case of multiband transport suggest tip selectivity to higher subbands, making them more observable in the total conductance map.

Identification of Waitea circinata as a Pathogen of the Moss Bryum argenteum var. argenteum on a Golf Course Fairway

Waitea circinata Warcup and Talbot (also referred to as W. circinata var. circinata) is an important fungal pathogen of amenity turfgrasses and is especially problematic on Poa annua in putting greens in the late spring or early summer. The pathogen was first identified in 2005 from Japan and has since been seen widely throughout the United States (1,2). On occasion, the pathogen has been observed attacking creeping bentgrass (Agrostis stolonifera) but is typically less virulent. Disease symptoms include prominent yellow rings appearing throughout established turf and moderate leaf necrosis. In the summer of 2012, moss from a section of fairway on a golf course in Edwards, CO was observed to be rapidly killed by a fungal pathogen producing copious amounts of aerial mycelium and appearing similar to Waitea microscopically. Aerial mycelium was transferred to acidified potato dextrose agar (PDA) (1 ml lactic/L). After 1 day at 25°C, mycelia were transferred to PDA. After 2 weeks, plates were covered with white aerial mycelium and separate, spherical, 0.5-mm diameter, salmon-colored sclerotia, which turned dark brown within a few days and were produced submerged throughout the media. Spores were never produced and right-angled branching of mycelia, characteristic of Waitea, was observed in mature cultures. Mycelial plugs were incubated in nutrient broth and DNA was extracted using a MoBio Power Plant DNA extraction kit. Amplification of ribosomal ITS sequences with ITS4 and ITS5 resulted in a 100% identity match with GenBank sequence HM807352, W. circinata var. circinta (3). To demonstrate pathogenicity on Bryum argenteum, unaffected moss from the submitted sample (identified as B. argenteum var. argenteum via 100% sequence identity with the published GenBank sequence GU907062) was removed from the originally submitted sample and placed in separate growth chambers at 95% humidity and 21, 26, and 31°C. An additional experiment employed local B. agenteum plants collected from the URI Kingston, RI campus. Agar plugs from the isolated W. circinata were placed on top of the moss and within 2 days the fungus had caused complete mortality at all three temperatures. The experiment was also undertaken using the same environmental conditions with 5-week-old annual bluegrass (P. annua) and creeping bentgrass cv. A4 grown from seed. Plants were inoculated with infected rye grains at 31, 26, and 21°C. After 1 week, the P. annua plants showed significant mortality at 26 and 31°C with little infection at 21°C and the A. stolonifera plants showed moderate mortality at 26°C and little infection at the other two temperatures. All experiments utilized an additional uninoculated control treatment that showed no moss/turf necrosis or mortality. Experiments were all repeated once and used three replicates per experiment. While moss is not intentionally cultivated on golf courses, it does occur with regularity and often presents itself as a difficult pest to manage. This particular isolate of W. circinata has identical ribosomal and physiological characteristics of the reported P. annua pathogen but can attack one moss species and may be a possible candidate for selective biological control of moss in golf course settings. It is unclear how widespread moss pathogenicity is within W. circinata. References: (1) E. N. Njambere et al. Plant Dis. 95:78 2011. (2) T. Toda et al. Plant Dis. 89:536, 2005. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications, 1990.

Modified surgical approach for removal of an ivory osteoma in the paranasal sinus. A case report

Osteomas are benign tumors that consist mainly of mature compact or cancellous bone. The most common site in maxillofacial complex is the mandible, particularly the angle, followed by sinuses. The authors report a case of an ivory osteoma of the paranasal sinus in a 16 year-old male patient. The lesion was located in the left paranasal sinus (frontal, ethmoidal and maxillary), obstructing the nasolacrimal duct, resulting in dacryocystitis and frontal mucocele. The ethmoid and orbital portions were approached and excised through a Weber-Ferguson incision and maxillary osteotomy was carried out to remove the ivory osteoma, considering its location in the central and deep region of the face. After tumor removal and drainage of frontal and ethmoidal sinuses, the bone flap was repositioned using titanium microplates and screws. Soft tissue was then sutured. The patient was seen again at 3 weeks, 3 months and 2 years after surgery. Overall, he showed a good recovery and wound healing. A multispeciality team approach is advisable in such cases if radical excision is necessary. A craniofacial approach made radical single stage excision of this multicompartmental ivory osteoma possible with an uneventful postoperative period.

A dosimetric calibration method for a double-focused multileaf collimator

A method based on penumbra measurements and not on light field, is proposed for the calibration of the Siemens 82-leaf Optifocus multileaf collimator (MLC). The measurements were performed using MLCSoft version 1.2.0.4. (PTW-Freiburg, Germany), which is a software tool based on the LA48 measuring system (a linear array of 47 liquid-ionization chambers). The new leaf positions for each of the leaf banks are calculated from the MLCSoft results using an external spreadsheet. Using the proposed method the MLC calibration is directly performed in terms of dosimetry settings with improved precision. The nominal resulting accuracy of 0.5 mm is highly imposed by the limitations of the moving mechanism of the leaves and not by the method itself. To test the results of the MLC calibration, in-water measurements of off-axis dose profiles have been measured in order to verify different field sizes.

[Cost-effectiveness analysis comparing methotrexate with PUVA therapy for moderate-severe psoriasis in the sanitary area of Badajoz]

OBJECTIVE

To perform a cost-effectiveness analysis, by using a decision tree model, comparing methotrexate with PUVA therapy for moderate to severe chronic plaque psoriasis in the sanitary area of Badajoz (south-western Spain) over a one-year period.

MATERIAL AND METHODS

The following variables and data sources were included: efficacy (a 50 % reduction in the PASI) and safety (adverse reactions). Data were retrieved from the dermatologic medical literature, mainly general reviews, systematic reviews and randomized clinical trials. Therapy schedules followed current guidelines from work task teams and consensus documents. Direct costs included unitary costs of medical consults, costs of laboratory tests, pharmacy, phototherapy sessions and costs derived from adverse reactions. Indirect costs included travel expenses and costs of lost productive work time.

RESULTS

Unitary cost of methotrexate therapy would be 952.79 euros per treatment (direct cost: 796.48; indirect cost: 156.31). Unitary cost of PUVA therapy would be 899.70 euros per treatment (direct cost: 383.36; indirect cost: 516.34). Total cost of a one-year treatment with methotrexate would be 255,202.73 euros. Total cost of a one-year treatment with PUVA would be 266,406.88 euros. The average cost-effectiveness ratios per case effectively treated would be 1,519.06 euros for methotrexate therapy, and 1,085.18 euros for PUVA therapy. The incremental cost-effectiveness ratio of PUVA/methotrexate would be 150.65 euros for each additional case effectively treated.

CONCLUSIONS

One-year treatment for moderate to severe psoriasis in the sanitary area of Badajoz would be more expensive but also more cost-effective with PUVA than with methotrexate. However, indirect costs (borne by patients), are higher for PUVA therapy, a fact that raises an issue of equity. The results should be interpreted taking into account the methodological limitations of a modelling study.

Bulk flow in ferrofluids in a uniform rotating magnetic field

Direct measurements of the bulk flow of a ferrofluid in a uniform rotating magnetic field were obtained using the ultrasonic velocity profile method. The fluid was observed to corotate with the field in a rigid-body-like fashion throughout the bulk of the container, except near the air-fluid interface, where it was observed to counterrotate. The results were found in qualitative agreement with the spin diffusion theory of Zaitsev and Shliomis [J. Appl. Mech. Tech. Phys. 10, 696 (1969)]10.1007/BF00907424.

A Monte Carlo multiple source model applied to radiosurgery narrow photon beams

Monte Carlo (MC) methods are nowadays often used in the field of radiotherapy. Through successive steps, radiation fields are simulated, producing source Phase Space Data (PSD) that enable a dose calculation with good accuracy. Narrow photon beams used in radiosurgery can also be simulated by MC codes. However, the poor efficiency in simulating these narrow photon beams produces PSD whose quality prevents calculating dose with the required accuracy. To overcome this difficulty, a multiple source model was developed that enhances the quality of the reconstructed PSD, reducing also the time and storage capacities. This multiple source model was based on the full MC simulation, performed with the MC code MCNP4C, of the Siemens Mevatron KD2 (6 MV mode) linear accelerator head and additional collimators. The full simulation allowed the characterization of the particles coming from the accelerator head and from the additional collimators that shape the narrow photon beams used in radiosurgery treatments. Eight relevant photon virtual sources were identified from the full characterization analysis. Spatial and energy distributions were stored in histograms for the virtual sources representing the accelerator head components and the additional collimators. The photon directions were calculated for virtual sources representing the accelerator head components whereas, for the virtual sources representing the additional collimators, they were recorded into histograms. All these histograms were included in the MC code, DPM code and using a sampling procedure that reconstructed the PSDs, dose distributions were calculated in a water phantom divided in 20000 voxels of 1 x 1 x 5 mm3. The model accurately calculates dose distributions in the water phantom for all the additional collimators; for depth dose curves, associated errors at 2sigma were lower than 2.5% until a depth of 202.5 mm for all the additional collimators and for profiles at various depths, deviations between measured and calculated values were less than 2.5% or 1 mm.

Application of GEANT4radiation transport toolkit to dose calculations in anthropomorphic phantoms

In this paper, we present a novel implementation of a dose calculation application, based on the GEANT4 Monte Carlo toolkit. Validation studies were performed with an homogeneous water phantom and an Alderson-Rando anthropomorphic phantom both irradiated with high-energy photon beams produced by a clinical linear accelerator. As input, this tool requires computer tomography images for automatic codification of voxel-based geometries and phase-space distributions to characterize the incident radiation field. Simulation results were compared with ionization chamber, thermoluminescent dosimetry data and commercial treatment planning system calculations. In homogeneous water phantom, overall agreement with measurements were within 1-2%. For anthropomorphic simulated setups (thorax and head irradiation) mean differences between GEANT4 and TLD measurements were less than 2%. Significant differences between GEANT4 and a semi-analytical algorithm implemented in the treatment planning system, were found in low-density regions, such as air cavities with strong electronic disequilibrium.

Erbium:Yag laser therapy of lichenoid red tattoo reaction

Delayed reactions caused by red tattoo pigments are often difficult to treat. We report a 31-year-old female patient with a lichenoid reaction to a red tattoo on the right ankle who was successfully treated with five sessions of a surgical Erbium:Yag laser, using several passes in each session. Our work leads us to consider that Er:Yag laser therapy may be an effective and safe treatment for these therapeutically challenging reactions.

Cheilitis granulomatosa of Melkersson-Rosenthal syndrome: Treatment with intralesional corticosteroid injections

BACKGROUND

Melkersson-Rosenthal syndrome may manifest as the classical triad (orofacial edema, facial nerve palsy and stable lingua plicata) but monosymptomatic manifestations or combinations of typical symptoms are not infrequent. The available therapeutic options provide only limited success or temporary benefit.

CASE REPORT

A 20-year-old man presented with a 7-month history of recurrent episodes of swelling of the upper lip without pain, burning or local pruritus. No causative factors, such as food, drugs or latex, or physical, chemical or emotional conditions could be identified. The patient had been treated with oral antihistamines and corticosteroids with no clinical improvement. Physical examination showed firm edema without fovea, limited to the central area of the upper lip without epidermal changes or symptoms on palpation. The patient had a previous history of facial palsy 6 years previously and recurrent episodes of herpes simplex labialis. Skin prick tests with inhalant aeroallergens, food, latex and Anisakis allergens were negative. Laboratory investigation revealed normal complete blood count, erythrocyte sedimentation rate, thyroid hormones, biochemistry, complement components (C3, C4 and C1-esterase inhibitor) and CH50, rheumatoid factor, antinuclear antibodies, immune complexes, protein electrophoresis and immunoglobulins. Thorax and paranasal sinus radiographs were clear. Biopsy of the involved area of the lip showed edema with lymphocytic and plasma cell infiltration and mononuclear perivascular infiltrates without granulomas, suggesting initial granulomatous cheilitis. Because the patient showed lack of response and/or poor tolerance to prior treatments (deflazacort, clofazimine and metronidazole), intralesional triamcinolone injections were administered with satisfactory response from the first session.

CONCLUSIONS

Response to available treatments for Melkersson-Rosenthal syndrome is highly variable. In the present case, intralesional triamcinolone injections were effective.

Basic dosimetry of radiosurgery narrow beams using Monte Carlo simulations: A detailed study of depth of maximum dose

In radiosurgery narrow photon beams, the depth of maximum dose d(max), in the beam central axis increases as the size of the additional collimator increases. This behavior is the opposite of what is observed in radiotherapy conventional beams. To understand this effect, experimental depth dose curves of the additional collimators were obtained for a Siemens KD2 linear accelerator in 6 MV photon mode and the shift of d(max) varied from 11.0 +/- 0.6 mm for the 5 mm collimator to 14.5 +/- 0.6 mm for the 23 mm collimator. Monte Carlo simulations showed that the photons that had no interactions in the additional collimators, contributing more than 90% to the total dose in water, were responsible for the shift in d(max). Monte Carlo simulations also showed that electrons originated from these photons and contributing to the dose deposit in water in the beam central axis could be divided in two groups: those that deposit energy far away from their point of origin (the point of the first photon collision in water) and those that deposit energy locally (originated at more than one photon collision in water). Applying a simplified model based on the fact that the photons originating Compton electrons (at the first and subsequent collisions) have similar characteristics in air for all the additional collimators, it was shown that these electrons were also responsible for the shift of d(max) in the beam central axis. Finally, it was shown that the changes in the initial gradients of the depth dose curves of the additional collimators were mainly due to electrons originated from the first photon collision in water.

Subcellular localization of beta-catenin in malignant cell lines and squamous cell carcinomas of the oral cavity

BACKGROUND

Beta-catenin, an E-cadherin-associated protein involved in cell-cell adhesion and signaling, has been hypothesized to translocate to the nucleus and activate transcription in several human cancers, including oral squamous cell carcinomas (OSCC).

METHODS

In the present study, we analyzed the subcellular localization of beta-catenin in cultures of human oral normal and malignant (cell lines SCC15 and SCC25) keratinocytes and in 24 frozen samples of oral squamous cell carcinomas by a double-staining technique for nucleic acids and beta-catenin. Growth potential, as assessed by cell count at different time periods, was established for normal, SCC15 and SCC25 cell lines; oral squamous cell carcinomas were classified according to the histopathological and malignancy indexes.

RESULTS

Beta-catenin localized at the plasma membrane in the normal and SCC15 cells, not in the SCC25 cells, where it localized mostly in the perinuclear and nuclear areas. In the growth assays, SCC25 cell lines proliferated faster than in normal and SCC15 cells over a period of 6 days (cell numbers were significantly different, P < 0.0001). Carcinoma sections showed a combination of membranous, cytoplasmic and, in few invading epithelial islands of two tumors, nuclear localization of beta-catenin.

CONCLUSIONS

In oral squamous cell carcinomas, nuclear beta-catenin staining was observed only within invading islands of two carcinomas deep in the underlying connective tissue. On the basis of this study, we conclude that intranuclear beta-catenin does not appear to be a common finding in oral squamous cell carcinomas and that a clear association between intranuclear beta-catenin and histopathological and malignancy indexes in vivo could not be established.

Quantitative analysis of herpesvirus sequences from normal tissue and fibropapillomas of marine turtles with real-time PCR

Quantitative real-time PCR has been used to measure fibropapilloma-associated turtle herpesvirus (FPTHV) pol DNA loads in fibropapillomas, fibromas, and uninvolved tissues of green, loggerhead, and olive ridley turtles from Hawaii, Florida, Costa Rica, Australia, Mexico, and the West Indies. The viral DNA loads from tumors obtained from terminal animals were relatively homogeneous (range 2-20 copies/cell), whereas DNA copy numbers from biopsied tumors and skin of otherwise healthy turtles displayed a wide variation (range 0.001-170 copies/cell) and may reflect the stage of tumor development. FPTHV DNA loads in tumors were 2.5-4.5 logs higher than in uninvolved skin from the same animal regardless of geographic location, further implying a role for FPTHV in the etiology of fibropapillomatosis. Although FPTHV pol sequences amplified from tumors are highly related to each other, single signature amino acid substitutions distinguish the Australia/Hawaii, Mexico/Costa Rica, and Florida/Caribbean groups.

Transgenic mice with cardiac-specific expression of activating transcription factor 3, a stress-inducible gene, have conduction abnormalities and contractile dysfunction

Activating transcription factor 3 (ATF3) is a member of the CREB/ATF family of transcription factors. Previously, we demonstrated that the expression of the ATF3 gene is induced by many stress signals. In this report, we demonstrate that expression of ATF3 is induced by cardiac ischemia coupled with reperfusion (ischemia-reperfusion) in both cultured cells and an animal model. Transgenic mice expressing ATF3 under the control of the alpha-myosin heavy chain promoter have atrial enlargement, and atrial and ventricular hypertrophy. Microscopic examination showed myocyte degeneration and fibrosis. Functionally, the transgenic heart has reduced contractility and aberrant conduction. Interestingly, expression of sorcin, a gene whose product inhibits the release of calcium from sarcoplasmic reticulum, is increased in these transgenic hearts. Taken together, our results indicate that expression of ATF3, a stress-inducible gene, in the heart leads to altered gene expression and impaired cardiac function.

Bond strength of dual-cured resin cements to human teeth

PURPOSE

This study evaluated the bond strength of four commercial resin luting cements to enamel and superficial dentin, using a second-generation laboratory composite.

MATERIALS AND METHODS

Forty teeth were embedded in acrylic: 20 had superficial dentin exposed; 20 had enamel exposed. Each group was divided into four subgroups (n = 5) to be bonded with Variolink II, Dual Cement, 2-bond-2, and Permalute System, using an inverted, truncated cone of pre-cured Artglass that was placed over the resin cement with a load of 2 N for 2 seconds. Specimens were stored at 37 degrees C in 100% relative humidity for 24 hours before being tested for tensile bond strength (MPa). Data were analyzed using a two-way analysis of variance. Tukey-Kramer intervals for comparisons among resin cements and bonding substrates were calculated at a .05 significance level.

RESULTS

Significant differences were found among resin cements. Variolink II had statistically higher bond strength values for both substrates than the rest of the cements evaluated. When bonding was to enamel, all failures were cohesive in the composite, and when bonding was to dentin, some adhesive failures occurred at the resin cement-dentin interface. Permalute System had higher bond strengths than 2-bond-2 and Dual Cement when bonded to enamel.

CONCLUSIONS

Variolink II and Permalute had statistically different bond strengths to enamel and dentin. Variolink II showed statistically higher values for dentin bonding than the other cements. Use of Variolink II and Permalute resulted in statistically higher bond strengths than the other two cements.