Coherent light control of a metastable hidden state

Metastable phases present a promising route to expand the functionality of complex materials. Of particular interest are light-induced metastable phases that are inaccessible under equilibrium conditions, as they often host new, emergent properties switchable on ultrafast timescales. However, the processes governing the trajectories to such hidden phases remain largely unexplored. Here, using time- and angle-resolved photoemission spectroscopy, we investigate the ultrafast dynamics of the formation of a hidden quantum state in the layered dichalcogenide 1T-TaS2 upon photoexcitation. Our results reveal the nonthermal character of the transition governed by a collective charge-density-wave excitation. Using a double-pulse excitation of the structural mode, we show vibrational coherent control of the phase-transition efficiency. Our demonstration of exceptional control, switching speed, and stability of the hidden state are key for device applications at the nexus of electronics and photonics.

Chiral domain dynamics and transient interferences of mirrored superlattices in nonequilibrium electronic crystals

Mirror symmetry plays a major role in determining the properties of matter and is of particular interest in condensed many-body systems undergoing symmetry breaking transitions under non-equilibrium conditions. Typically, in the aftermath of such transitions, one of the two possible broken symmetry states is emergent. However, synthetic systems and those formed under non-equilibrium conditions may exhibit metastable states comprising of both left (L) and right (R) handed symmetry. Here we explore the formation of chiral charge-density wave (CDW) domains after a laser quench in 1T-TaS2 with scanning tunneling microscopy. Typically, we observed transient domains of both chiralities, separated spatially from each other by domain walls with different structure. In addition, we observe transient density of states modulations consistent with interference of L and R-handed charge density waves within the surface monolayer. Theoretical modeling of the intertwined domain structures using a classical charged lattice gas model reproduces the experimental domain wall structures. The superposition (S) state cannot be understood classically within the correlated electron model but is found to be consistent with interferences of L and R-handed charge-density waves within domains, confined by surrounding domain walls, vividly revealing an interference of Fermi electrons with opposite chirality, which is not a result of inter-layer interference, but due to the interaction between electrons within a single layer, confined by domain wall boundaries.

Crystallization of polarons through charge and spin ordering transitions in 1T-TaS2

The interaction of electrons with the lattice in metals can lead to reduction of their kinetic energy to the point where they may form heavy, dressed quasiparticles-polarons. Unfortunately, polaronic lattice distortions are difficult to distinguish from more conventional charge- and spin-ordering phenomena at low temperatures. Here we present a study of local symmetry breaking of the lattice structure on the picosecond timescale in the prototype layered dichalcogenide Mott insulator 1T-TaS2 using X-ray pair-distribution function measurements. We clearly identify symmetry-breaking polaronic lattice distortions at temperatures well above the ordered phases, and record the evolution of broken symmetry states from 915 K to 15 K. The data imply that charge ordering is driven by polaron crystallization into a Wigner crystal-like state, rather than Fermi surface nesting or conventional electron-phonon coupling. At intermediate temperatures the local lattice distortions are found to be consistent with a quantum spin liquid state.

Cavity-mediated thermal control of metal-to-insulator transition in 1T-TaS2

Placing quantum materials into optical cavities provides a unique platform for controlling quantum cooperative properties of matter, by both weak and strong light-matter coupling1,2. Here we report experimental evidence of reversible cavity control of a metal-to-insulator phase transition in a correlated solid-state material. We embed the charge density wave material 1T-TaS2 into cryogenic tunable terahertz cavities3 and show that a switch between conductive and insulating behaviours, associated with a large change in the sample temperature, is obtained by mechanically tuning the distance between the cavity mirrors and their alignment. The large thermal modification observed is indicative of a Purcell-like scenario in which the spectral profile of the cavity modifies the energy exchange between the material and the external electromagnetic field. Our findings provide opportunities for controlling the thermodynamics and macroscopic transport properties of quantum materials by engineering their electromagnetic environment.

Optical vortex induced spatio-temporally modulated superconductivity in a high-Tc cuprate

We report an experimental approach to produce spatially localized photoinduced superconducting state in a cuprate superconductor using optical vortices with ultrafast pulses. The measurements were carried out using coaxially aligned three-pulse time-resolved spectroscopy, in which an intense vortex pulse was used for coherent quenching of superconductivity and the resulting spatially modulated metastable states were analyzed by the pump-probe spectroscopy. The transient response after quenching shows a spatially localized superconducting state that remains unquenched at the dark core of the vortex beam for a few picoseconds. Because the quenching is instantaneously driven by photoexcited quasiparticles, the vortex beam profile can be transferred directly to the electron system. By using the optical vortex-induced superconductor, we demonstrate spatially resolved imaging of the superconducting response and show that the spatial resolution can be improved using the same principle as that of super-resolution microscopy for fluorescent molecules. The demonstration of spatially controlled photoinduced superconductivity is significant for establishing a new method for exploring novel photoinduced phenomena and applications in ultrafast optical devices.

Charge Configuration Memory Devices: Energy Efficiency and Switching Speed

Current trends in data processing have given impetus for an intense search of new concepts of memory devices with emphasis on efficiency, speed, and scalability. A promising new approach to memory storage is based on resistance switching between charge-ordered domain states in the layered dichalcogenide 1T-TaS2. Here we investigate the energy efficiency scaling of such charge configuration memory (CCM) devices as a function of device size and data write time τW as well as other parameters that have bearing on efficient device operation. We find that switching energy efficiency scales approximately linearly with both quantities over multiple decades, departing from linearity only when τW approaches the ∼0.5 ps intrinsic switching limit. Compared to current state of the art memory devices, CCM devices are found to be much faster and significantly more energy efficient, demonstrated here with two-terminal switching using 2.2 fJ, 16 ps electrical pulses.

A time-domain phase diagram of metastable states in a charge ordered quantum material

Metastable self-organized electronic states in quantum materials are of fundamental importance, displaying emergent dynamical properties that may be used in new generations of sensors and memory devices. Such states are typically formed through phase transitions under non-equilibrium conditions and the final state is reached through processes that span a large range of timescales. Conventionally, phase diagrams of materials are thought of as static, without temporal evolution. However, many functional properties of materials arise as a result of complex temporal changes in the material occurring on different timescales. Hitherto, such properties were not considered within the context of a temporally-evolving phase diagram, even though, under non-equilibrium conditions, different phases typically evolve on different timescales. Here, by using time-resolved optical techniques and femtosecond-pulse-excited scanning tunneling microscopy (STM), we track the evolution of the metastable states in a material that has been of wide recent interest, the quasi-two-dimensional dichalcogenide 1T-TaS₂. We map out its temporal phase diagram using the photon density and temperature as control parameters on timescales ranging from 10⁻¹² to 10³ s. The introduction of a time-domain axis in the phase diagram enables us to follow the evolution of metastable emergent states created by different phase transition mechanisms on different timescales, thus enabling comparison with theoretical predictions of the phase diagram, and opening the way to understanding of the complex ordering processes in metastable materials.

Tracking the evolution of non-equilibrium phases requires measurements over a wide range of timescales. Here, using a combination of femtosecond spectroscopy and scanning tunneling microscopy, the authors map out a temporal phase diagram of metastable states in a charge-ordered material 1T-TaS₂.

Unveiling the electronic transformations in the semi-metallic correlated-electron transitional oxide Mo8O23

Mo₈O₂₃ is a low-dimensional chemically robust transition metal oxide coming from a prospective family of functional materials, MoO_3−x, ranging from a wide gap insulator (x = 0) to a metal (x = 1). The large number of stoichometric compounds with intermediate x have widely different properties. In Mo₈O₂₃, an unusual charge density wave transition has been suggested to occur above room temperature, but its low temperature behaviour is particularly enigmatic. We present a comprehensive experimental study of the electronic structure associated with various ordering phenomena in this compound, complemented by theory. Density-functional theory (DFT) calculations reveal a cross-over from a semi-metal with vanishing band overlap to narrow-gap semiconductor behaviour with decreasing temperature. A buried Dirac crossing at the zone boundary is confirmed by angle-resolved photoemission spectroscopy (ARPES). Tunnelling spectroscopy (STS) reveals a gradual gap opening corresponding to a metal-to-insulator transition at 343 K in resistivity, consistent with CDW formation and DFT results, but with large non-thermal smearing of the spectra implying strong carrier scattering. At low temperatures, the CDW picture is negated by the observation of a metallic Hall contribution, a non-trivial gap structure in STS below ∼170 K and ARPES spectra, that together represent evidence for the onset of the correlated state at 70 K and the rapid increase of gap size below ∼30 K. The intricate interplay between electronic correlations and the presence of multiple narrow bands near the Fermi level set the stage for metastability and suggest suitability for memristor applications.

Quantum jamming transition to a correlated electron glass in 1T-TaS2

Distinct many-body states may be created under non-equilibrium conditions through different ordering paths, even when their constituents are subjected to the same fundamental interactions. The phase-transition mechanism to such states remains poorly understood. Here, we show that controlled optical or electromagnetic perturbations can lead to an amorphous metastable state of strongly correlated electrons in a quasi-two-dimensional dichalcogenide. Scanning tunnelling microscopy reveals a hyperuniform pattern of localized charges, whereas multitip surface nanoscale conductivity measurements and tunnelling spectroscopy show an electronically gapless conducting state that is different from conventional Coulomb glasses and many-body localized systems. The state is stable up to room temperature and shows no signs of either local charge order or phase separation. The mechanism for its formation is attributed to a dynamical localization of electrons through mutual interactions. Theoretical calculations confirm the correlations between localized charges to be crucial for the state's unusual stability.

Significance of the Ki-67 proliferation index in the assessment of the therapeutic response to cisplatin-based chemotherapy in patients with advanced cervical cancer

OBJECTIVE

The purposes of this study were to examine the therapeutic response of advanced cervical cancer to Ki-67 proliferative index (Ki-67 PI) dependent cisplatin chemotherapy, and to determine Ki-67 PI referential value that is expected to provide a satisfactory therapeutic response of cervical cancer to cisplatin chemotherapy.

PATIENTS AND METHODS

This prospective study enrolled 59 patients treated for cervical cancer at Clinic for Oncology, Clinical Center Nis, Serbia. According to the obtained Ki-67 PI values, patients were divided into three groups, and all the patients received the same cytostatic, cisplatin. Therapeutic response to chemotherapy was evaluated in relation to disease progression presence or absence and progression-free survival after a year follow-up since the first chemotherapy.

RESULTS

Survival rate increases with an increase of Ki-67 PI by Kaplan-Meier survival analysis, meaning that survival rate is statistically significantly shorter in the group of patients with Ki-67 PI < 40% in comparison to patients from other two groups (p=0.010). Mann-Whitney test confirmed a statistically significant increase in survival rate among the groups of patients formed according to Ki-67 PI (p<0.05). Kaplan-Meier survival analysis confirmed that the mean survival rate in the group of patients with Ki-67 PI values over 60% is statistically significantly longer in comparison to patients with Ki-67 PI values below or equal 60% (p<0.001).

CONCLUSIONS

Advanced cervical cancer with a high Ki-67 PI expression responds better to cisplatin-based chemotherapy, thus resulting in a longer survival rate. The values of Ki-67 PI were determined: high Ki-67 PI (≥ 60%), moderate Ki-67 PI (40-60%), and low Ki-67 PI (≤ 40%).

Large retroperitoneal schwannoma: a rare cause of chronic back pain

Schwannomas are tumours that arise from Schwann cells of the peripheral nerve sheath and rarely occur in the retroperitoneum. We report a 45-year-old woman who presented with a 2-year history of continuous progressive right-sided lower back and dull flank pain radiating into her posterolateral thigh. Abdominal magnetic resonance imaging showed a homogenous soft-tissue tumour with thick capsular lining, which lay in the right retroperitoneum. The tumour was removed at surgery. A histological examination confirmed the diagnosis of benign encapsulated cellular schwannoma. Complete tumour excision should be regarded as the treatment of choice for benign retroperitoneal schwannomas. Successful treatment of these tumours requires thorough preoperative planning and a multidisciplinary approach.

Histopathologic differentiation as a prognostic factor in patients with carcinoma of the hepatopancreatic ampulla of Vater

Objective

Periampullary carcinomas are a group of neoplasms with variable histopathology that originate from the anatomical junction of different epithelial types including the bile duct, pancreatic duct, and duodenal mucosa. This study was performed to determine whether the histopathologic type of these tumors should be considered an independent prognostic factor.

Methods

We analyzed the specimen histopathology of 37 patients who underwent radical cephalic pancreatoduodenectomy for carcinoma of the ampulla of Vater during a 5-year period. We excluded patients with other tumors with an indication for Whipple’s procedure and those in whom R0 resection was not achieved.

Results

The carcinomas of the hepatopancreatic ampulla were intestinal in 23 (62%) patients, pancreatobiliary in 13 (35%), and mixed type in 1 (3%). The analysis demonstrated significantly more advanced local tumor spread, a more aggressive lymph node metastasizing pattern, and more frequent lymphatic and perineural invasion in patients with pancreatobiliary than intestinal and mixed type tumors.

Conclusion

Pancreatobiliary type of ampullary carcinoma is associated with a poorer prognosis than intestinal and mixed types because of its more aggressive behavior. Histopathology should be regarded as an independent predictor of survival and may have therapeutic and prognostic implications for patients.

Nonequilibrium optical control of dynamical states in superconducting nanowire circuits

Optical control of states exhibiting macroscopic phase coherence in condensed matter systems opens intriguing possibilities for materials and device engineering, including optically controlled qubits and photoinduced superconductivity. Metastable states, which in bulk materials are often associated with the formation of topological defects, are of more practical interest. Scaling to nanosize leads to reduced dimensionality, fundamentally changing the system's properties. In one-dimensional superconducting nanowires, vortices that are present in three-dimensional systems are replaced by fluctuating topological defects of the phase. These drastically change the dynamical behavior of the superconductor and introduce dynamical periodic long-range ordered states when the current is driven through the wire. We report the control and manipulation of transitions between different dynamically stable states in superconducting δ₃-MoN nanowire circuits by ultrashort laser pulses. Not only can the transitions between different dynamically stable states be precisely controlled by light, but we also discovered new photoinduced hidden states that cannot be reached under near-equilibrium conditions, created while laser photoexcited quasi-particles are outside the equilibrium condition. The observed switching behavior can be understood in terms of dynamical stabilization of various spatiotemporal periodic trajectories of the order parameter in the superconductor nanowire, providing means for the optical control of the superconducting phase with subpicosecond control of timing.

Stacking order dynamics in the quasi-two-dimensional dichalcogenide 1T-TaS2 probed with MeV ultrafast electron diffraction

Transitions between different charge density wave (CDW) states in quasi-two-dimensional materials may be accompanied also by changes in the inter-layer stacking of the CDW. Using MeV ultrafast electron diffraction, the out-of-plane stacking order dynamics in the quasi-two-dimensional dichalcogenide 1T-TaS₂ is investigated for the first time. From the intensity of the CDW satellites aligned around the commensurate l = 1/6 characteristic stacking order, it is found out that this phase disappears with a 0.3 ps time constant. Simultaneously, in the same experiment, the emergence of the incommensurate phase, with a slightly slower 2.0 ps time constant, is determined from the intensity of the CDW satellites aligned around the incommensurate l = 1/3 characteristic stacking order. These results might be of relevance in understanding the metallic character of the laser-induced metastable "hidden" state recently discovered in this compound.

Exciton and charge carrier dynamics in few-layer WS2

Semiconducting transition metal dichalcogenides (TMDs) have been applied as the active layer in photodetectors and solar cells, displaying substantial charge photogeneration yields. However, their large exciton binding energy, which increases with decreasing thickness (number of layers), as well as the strong resonance peaks in the absorption spectra suggest that excitons are the primary photoexcited states. Detailed time-domain studies of the photoexcitation dynamics in TMDs exist mostly for MoS2. Here, we use femtosecond optical spectroscopy to study the exciton and charge dynamics following impulsive photoexcitation in few-layer WS2. We confirm excitons as the primary photoexcitation species and find that they dissociate into charge pairs with a time constant of about 1.3 ps. The better separation of the spectral features compared to MoS2 allows us to resolve a previously undetected process: these charges diffuse through the samples and get trapped at defects, such as flake edges or grain boundaries, causing an appreciable change of their transient absorption spectra. This finding opens the way to further studies of traps in TMD samples with different defect contents.

Controlling the metal-to-insulator relaxation of the metastable hidden quantum state in 1T-TaS2

Controllable switching between metastable macroscopic quantum states under nonequilibrium conditions induced either by light or with an external electric field is rapidly becoming of great fundamental interest. We investigate the relaxation properties of a "hidden" (H) charge density wave (CDW) state in thin single crystals of the layered dichalcogenide 1T-TaS2, which can be reached by either a single 35-fs optical laser pulse or an ~30-ps electrical pulse. From measurements of the temperature dependence of the resistivity under different excitation conditions, we find that the metallic H state relaxes to the insulating Mott ground state through a sequence of intermediate metastable states via discrete jumps over a "Devil's staircase." In between the discrete steps, an underlying glassy relaxation process is observed, which arises because of reciprocal-space commensurability frustration between the CDW and the underlying lattice. We show that the metastable state relaxation rate may be externally stabilized by substrate strain, thus opening the way to the design of nonvolatile ultrafast high-temperature memory devices based on switching between CDW states with large intrinsic differences in electrical resistance.

Evidence for carrier localization in the pseudogap state of cuprate superconductors from coherent quench experiments

A 'pseudogap' was introduced by Mott to describe a state of matter that has a minimum in the density of states at the Fermi level, deep enough for states to become localized. It can arise either from Coulomb repulsion between electrons, and/or incipient charge or spin order. Here we employ ultrafast spectroscopy to study dynamical properties of the normal to pseudogap state transition in the prototype high-temperature superconductor Bi2Sr2CaCu2O8+δ. We perform a systematic temperature and doping dependence study of the pseudogap photodestruction and recovery in coherent quench experiments, revealing marked absence of critical behaviour of the elementary excitations, which implies an absence of collective electronic ordering beyond a few coherence lengths on short timescales. The data imply ultrafast carrier localization into a textured polaronic state arising from a competing Coulomb interaction and lattice strain, enhanced by a Fermi surface instability.

Alternaria-Associated Fungus Ball of Orbit Nose and Paranasal Sinuses: Case Report of a Rare Clinical Entity

Alternaria-associated fungus ball of maxillar, ethmoidal paranasal sinuses, nasal cavity and orbit with bone erosion is extremely rare. Till recently, only two cases of this infection in immune competitive patients have been reported. We are herein describing the case of immune-competent woman who suffered of nasal congestion for 10 years. Patient was treated for tumor-like lesion in right maxillar sinus, where propagation in right nose cavity, right ethmoidal cells and right orbita was present. The organism that was seen in surgical removal of fungal debris by histological study, in using mycological testing, was proven as Alternaria alternata. Combination of surgical intervention and treatment with itraconazole eradicated fungal infection, and the disease was not relapsed in follow-up period of 2 years.

Unlocking the functional properties in one-dimensional MoSI cluster polymers by doping and photoinduced charge transfer

To improve functionalization of MoSI cluster polymers we have studied the effects of adsorption doping on the electrical transport, bundling, and optical absorption spectra. Doping results both in enhanced conductivity and aggregated bundles in dispersion. The different electronic properties of different bundle diameters can be ascribed to self-doping during the synthesis. Furthermore, doping shifts the characteristic absorption peaks and transfers oscillator strength to lower energies. Femtosecond optical spectroscopy shows that the spectral signature of adsorption and self-doping indeed originates from the population of electronic levels that are empty or absent in the undoped sample. The large spectral shifts and long lifetimes of photoinduced charges suggest efficient localization.

Coexistence of ferromagnetism and superconductivity in iron based pnictides: a time resolved magnetooptical study

Ferromagnetism and superconductivity are antagonistic phenomena. Their coexistence implies either a modulated ferromagnetic order parameter on a lengthscale shorter than the superconducting coherence length or a weak exchange coupling between the itinerant superconducting electrons and the localized ordered spins. In some iron based pnictide superconductors the coexistence of ferromagnetism and superconductivity has been clearly demonstrated. The nature of the coexistence, however, remains elusive since no clear understanding of the spin structure in the superconducting state has been reached and the reports on the coupling strength are controversial. We show, by a direct optical pump-probe experiment, that the coupling is weak, since the transfer of the excess energy from the itinerant electrons to ordered localized spins is much slower than the electron-phonon relaxation, implying the coexistence without the short-lengthscale ferromagnetic order parameter modulation. Remarkably, the polarization analysis of the coherently excited spin wave response points towards a simple ferromagnetic ordering of spins with two distinct types of ferromagnetic domains.

Multichannel photodiode detector for ultrafast optical spectroscopy

Construction and characterization of a multichannel photodiode detector based on commercially available components with high signal to noise of ∼10(6) and a rapid frame rate, suitable for time resolved femtosecond spectroscopy with high repetition femtosecond sources, is presented.

Ultrafast switching to a stable hidden quantum state in an electronic crystal

Hidden states of matter may be created if a system out of equilibrium follows a trajectory to a state that is inaccessible or does not exist under normal equilibrium conditions. We found such a hidden (H) electronic state in a layered dichalcogenide crystal of 1T-TaS2 (the trigonal phase of tantalum disulfide) reached as a result of a quench caused by a single 35-femtosecond laser pulse. In comparison to other states of the system, the H state exhibits a large drop of electrical resistance, strongly modified single-particle and collective-mode spectra, and a marked change of optical reflectivity. The H state is stable until a laser pulse, electrical current, or thermal erase procedure is applied, causing it to revert to the thermodynamic ground state.

Template synthesis of single-phase δ(3)-MoN superconducting nanowires

We demonstrate a new and effective method of producing single-phase superconducting δ3-MoN nanowires from bundled Mo6SyIz (8.2 ≤ y + z ≤ 10) nanowire templates in the presence of ammonia gas. Magnetic susceptibility and electrical resistance measurements confirm single-phase material synthesis. Measurements of four-contact resistance on single wires with diameters above 100 nm in a magnetic field are used to determine the critical field, while diameter dependence and magnetization measurements are used to investigate the homogeneity of the nanowires.

Coherent topological defect dynamics and collective modes in superconductors and electronic crystals

The control of condensed matter systems out of equilibrium by laser pulses allows us to investigate the system trajectories through symmetry-breaking phase transitions. Thus the evolution of both collective modes and single-particle excitations can be followed through diverse phase transitions with femtosecond resolution. Here we present experimental observations of the order parameter trajectory in the normal → superconductor transition and charge density wave ordering transitions. Of particular interest is the coherent evolution of topological defects forming during the transition via the Kibble-Zurek mechanism, which appears to be measurable in optical pump-probe experiments. Experiments on CDW systems reveal some new phenomena, such as coherent oscillations of the order parameter, the creation and emission of dispersive amplitude modes upon the annihilation of topological defects, and mixing with weakly coupled finite frequency (massive) bosons.

Incoherent topological defect recombination dynamics in TbTe3

We study the incoherent recombination of topological defects created during a rapid quench of a charge-density-wave system through the electronic ordering transition. Using a specially devised three-pulse femtosecond optical spectroscopy technique we follow the evolution of the order parameter over a wide range of time scales. By careful consideration of thermal processes we can clearly identify intrinsic topological defect annihilation processes on a time scale ∼30  ps and find a possible signature of extrinsic defect-dominated relaxation dynamics occurring on longer time scales.

Correlation of nuclear morphometry of primary melanoma of the skin with clinicopathological parameters and expression of tumor suppressor proteins (p53 and p16(INK4a)) and bcl-2 oncoprotein

PURPOSE

To determine the correlation of nuclear morphometry of primary cutaneous malignant melanoma (CMM) with clinicopathological parameters and the expression of p53, p16INK4a, and bcl-2.

METHODS

Image analysis and computerized nuclear morphometry were used in a series of 53 primary CMM (nodular melanoma/NM, N=33, and superficially spreading melanoma/SSM, N=20). The clinicopathological parameters determined for each tumor were histological type, maximal tumor diameter, Breslow thickness, Clark level, ulceration, mitotic index (MI) and pathological disease stage. Measured nuclear features included size, shape and optical density (OD). The results were correlated with the expression of p53, p16INK4a and bcl-2.

RESULTS

Significant differences between NM and SSM were found for the nuclear area, OD, and perimeter (p<0.05). MI showed significant correlations with nuclear area, perimeter and Feret diameter (p<0.05). In relation to the Clark level, significant differences were found for OD (p<0.01) and circularity of nuclei (p<0.05) between levels II and IV, while the Breslow thickness was not significantly correlated with nuclear morphometric variables. Significantly negative correlations were observed between OD and the expression of p53 and bcl-2, while significant positive correlation was found between the nuclear circularity and p53 immunoreaction intensity. There was no significant correlation between the expression of p16INK4a protein and karyometric variables.

CONCLUSION

OD and circularity are significantly correlated with p53 and bcl-2, and nuclear area with MI. These karyometric variables may determine a more aggressive phenotype of melanoma cells.

Comparative analysis of smoking influence on periodontal tissue in subjects with periodontal disease

THE AIM OF THE STUDY

The aim of the study was clinical and cytological examination of gingival changes in smokers and non-smokers. Further, specific goals of this study were health promotion in patient, particularly in smokers.

METHODS

The anamnesis was taken and clinical examination was conducted on the patients who came on Dental Clinic. During the clinical examination, plaque index (Pl)(16), gingival index Löe-Silness (Gi) and the community periodontal index of treatment needs (CPITN)(17) were done. After diagnosis was established, participants divided into group I -smokers, and group II - non-smokers. The gingival smears were taken for cytological analysis, dried on air, and stained by haematoxylin-eosin method.

RESULTS

The values of gingival index (GI)- Löe-Silness and periodontal index (CPITN) were higher in the group of smokers, but plaque index was also higher with statistically significant difference of their values between examined group, with maximum level of significance (p<0,001). The size of nucleus (area, Ferret's diameter and perimeter) was higher in the group of smokers, but differences were not statistically significant. In the group of non-smokers density of nucleus was higher than in non-smokers group, but difference was not statistically significant.

CONCLUSION

The values of examined indices showed higher values in smokers group. This finding could show that the level of oral hygiene is higher in the non smokers group. The size of nucleus (area, Ferret's diameter and perimeter) was higher in the group of smokers, but differences were not statistically significant. Teamwork of many different speciality experts is required for better periodontal health of smokers.

Primary leptomeningeal melanocytosis: A case report with an autopsy diagnosis

Introduction. Primary melanocytosis of the leptomeninges is a rare tumor, most likely originating from the melanocytes in the leptomeninges. The average survival is only about 5 months. Case report. A 61- years-old woman presented with headache, amaurosis and hallucinations lasted for two months, and she had been treated at the Clinic for Psychiatry and Clinic for Infectious Diseases. The cerebrospinal fluid analysis showed a lower level of glucose and a higher level of proteins. Small shaded areas of basal leptomeninges and hydrocephalus were found by computed tomography and magnetic resonance imaging. The autopsy showed a dark brown mass on basal leptomeninges with blurred boundaries. No pigmented skin lesions were found. Histopathological analysis revealed a primary leptomeningeal melanocytosis. Conclusion. Primary leptomeningeal melanocytosis is a rare tumor, difficult to diagnose. This case is being presented for its specificity, since this diagnosis is not frequently seen in practice.

Femtosecond carrier relaxation dynamics and photoinduced phase separation in κ-(BEDT-TTF)2Cu[N(CN)2]X (X=Br,Cl)

We investigate the relaxation dynamics of nonequilibrium carriers in organic conductors κ-(BEDT-TTF)(2)Cu[N(CN)(2)]X (X=Br and Cl) using ultrafast time-resolved optical spectroscopy. The dynamics for both salts show similar temperature dependences, which is well characterized by the carrier relaxation across the pseudogap (PG) of the magnitude Δ(PG) ≈ 16 meV for Br salt and 7.0 meV for Cl salt. On the other hand, only the Br salt shows an abrupt increase of the decay time at low temperature, indicating an additional decay component associated with the superconducting (SC) gap below T(c). The fluence dependent dynamics at low temperature evidences the superposition of the SC component onto the PG component. These results indicate a metallic-insulating phase separation in the Br salt triggered by photoexcited nonequilibrium carriers.

Ionization energy and energy gap structure of MoSI molecular wires: Kelvin probe, ultraviolet photoelectron spectroscopy, and cyclic voltammetry measurements

The work function W of Mo(6)S(3)I(6) molecular nanowires is determined by Kelvin probe (KP) measurements, UV photoelectron spectroscopy (UPS), and cyclic voltammetry (CV). The values obtained by all three methods agree well, giving W = 4.8 ± 0.1 eV. CV measurements also give a gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of E(g) = 1.2 ± 0.1 eV, in agreement with recent optical measurements, but in disagreement with theoretical calculations, which predict the material to be a metal. The electronic structure of Mo(6)S(3)I(6) suggests use of the material in applications such as bulk heterostructure photovoltaics and transparent electrodes and for molecular electronics devices.

Electron-phonon coupling in high-temperature cuprate superconductors determined from electron relaxation rates

We determined electronic relaxation times via pump-probe optical spectroscopy using sub-15 fs pulses for the normal state of two different cuprate superconductors. We show that the primary relaxation process is the electron-phonon interaction and extract a measure of its strength, the second moment of the Eliashberg function λ[ω2] = 800 ± 200 meV2 for La(1.85)Sr(0.15)CuO4 and λ[ω2] = 400 ± 100 meV2 for YBa(2)Cu(3)O(6.5). These values suggest a possible fundamental role of the electron-phonon interaction in the superconducting pairing mechanism.

Nanowire transformation and annealing by Joule heating

Joule heating of bundles of Mo(6)S(3)I(6) nanowires, in real time, was studied using in situ TEM probing. TEM imaging, electron diffraction, and conductivity measurements showed a complete transformation of Mo(6)S(3)I(6) into Mo via thermal decomposition. The resulting Mo nanowires had a conductivity that was 2-3 orders higher than the starting material. The conductivity increased even further, up to 1.8 x 10(6) S m( - 1), when the Mo nanowires went through annealing phases. These results suggest that Joule heating might be a general way to transform or anneal nanowires, pointing to applications such as metal nanowire fabrication, novel memory elements based on material transformation, or in situ improvement of field emitters.

Two-terminal nanoelectromechanical bistable switches based on molybdenum-sulfur-iodine molecular wire bundles

We demonstrate the application of Mo(6)S(3)I(6) molecular wire bundles for electrically controllable two-terminal on-off switches. We investigate how changes in the contact electrode material and geometry influence the device characteristics, hysteretic switching behavior and device stability. We also determine the device operating parameters, particularly the Young's moduli (40-270 GPa), operating current densities (3.2 x 10(5)-7 x 10(6) A m(-2)) and force constants. Although qualitatively, the properties of Mo(6)S(3)I(6) nanowires in nanoelectromechanical (NEM) switches are similar to those of carbon nanotubes (CNTs), their lower friction coefficient, higher mechanical stability and higher operation voltages give specific advantages in terms of smaller differences in on-off operating potentials, higher switching speeds and lower energy consumption than CNTs, which are critical for applications in NEM devices.

Aptamer conjugated Mo(6)S(9-x)I(x) nanowires for direct and highly sensitive electrochemical sensing of thrombin

We demonstrate the use of a novel electrochemical sensing platform based on aptamer conjugated Mo(6)S(9-x)I(x) nanowires (MoSI NWs) for the highly sensitive detection of the blood clotting enzyme thrombin. MoSI NWs nanowires were self-assembled on a gold electrode to which thrombin binding aptamers were covalently attached. The modification and immobilization steps of the electrodes were characterised by cyclic voltammetry along with high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The platform is based on the creation of a self-assembled MoSI MW layer via the sulfur-gold affinity followed by the creation of MoSI-thiolated aptamer conjugates via the sulfur-sulfur affinity. Using this system, sensitive quantitative detection of thrombin is realized by monitoring differences of differential pulse voltammetric responses of electrostatically trapped [Ru(NH(3))(6)](3+) cations to the aptamer before and after thrombin binding. The sensitivity limit for the detection of thrombin is 10 pM. This value is 10-fold better than all currently reported one step label free electrochemical strategies. Given the direct label free nature of the approach and the simplicity of the electronic detection, the aptamer conjugated MoSI NWs biosensor appears well suited for implementation in portable point of care microdevices directed at the rapid and sensitive detection of proteins and pathogens.

Processing and characterisation of Mo6S2I8 nanowires

One-dimensional nanostructures based on the Mo-S-I system have recently aroused a lot of interest as a viable alternative to the ubiquitous carbon nanotube due to their uniform structure and electronic properties for a given composition. Previous research on the Mo(6)S(3)I(6) and Mo(6)S(4.5)I(4.5) stoichiometries has also shown them to be soluble in common solvents like water, acetone or isopropyl alcohol, and to debundle on dilution. Here, the solubility, debundling and composition of Mo(6)S(2)I(8) nanowires are presented. They were found to be most soluble in dimethylformamide, which retained 47 wt% of a 0.08 gl(-1) nanowire (NW) material dispersion as thin NW bundles after one week. Dispersions of 0.8 gl(-1) and 5 gl(-1) even retained 54 wt% and 66 wt%, respectively. However the NW material was completely insoluble in water, and the surface energy of Mo(6)S(2)I(8) NWs was deduced as 67 mJ m(-2), higher than for other Mo-S-I NWs. UV-vis-NIR spectroscopy showed nanowire peaks familiar from Mo(6)S(3)I(6) and Mo(6)S(4.5)I(4.5) spectra around 1.8 and 2.8 eV, as well as unforeseen ultraviolet peaks at 3.5 and 4.4 eV. These chemical differences suggest an alternate, more strongly bonded structure to that seen for Mo(6)S(3)I(6) and Mo(6)S(4.5)I(4.5) NWs. Films deposited from a range of concentrations were investigated using atomic force microscopy (AFM) to determine bundle diameter distributions. The average diameter and the spread in diameters were found to decrease somewhat with decreasing concentration. However extrapolation gave a finite bundle size at infinite dilution, and an extension of the existing debundling model is proposed to take this into account. To confirm the nominal stoichiometry of Mo(6)S(2)I(8), which does not follow the generic Mo(6)S(x)I(9-x) formula of previous stoichiometries, EDX was carried out. The composition of nanowire bundles was found to be Mo(6)S(2.3)I(8.6), supporting the nominal composition.

Tumor size and karyometric variables in brain astrocytoma

PURPOSE

To show any possible correlation of some karyometric variables with tumor size in patients with brain astrocytoma, in order to confirm karyometry as an objective histological method.

PATIENTS AND METHODS

The study included 63 patients of different ages and both genders with brain astrocytoma histologically confirmed on the surgically removed material. In all patients maximal tumor excision was done, and all were postoperatively treated according to different therapeutic protocols. Tumor size (preoperative CT scan) was correlated with the duration of survival and the values of some karyometric tumor variables: area, density, maximal axis, mean axis, minimal axis, circumference, roundness, integrated optical density (IOD) and number of nuclei.

RESULTS

Patients were separated into 3 groups according to the average tumor diameter. There were 34 cases of medium-sized tumors, 12 of small and 17 of large-sized tumors, and their respective survival was 83, 97 and 24 weeks. Patients with large tumors had statistically shorter survival compared to those with medium and small tumors (log-rank test, p=0.0122). Seven out of 9 examined karyometric variables were significantly related (p<0.05) to the tumor size: area, maximal axis, mean axis, minimal axis, circumference, roundness and IOD.

CONCLUSION

Patients with larger tumors have shorter survival. The results of our morphometric analysis of the tumor cell nuclei, after correlation with CT findings, revealed that nuclear pleomorphism and larger nuclear size are associated with larger brain astrocytomas.

Mandible schwannoma (neurilemmoma) presenting as periapical lesion

Schwannoma is a benign nerve tumour that originates from Schwann cells, which cover peripheral nerves. Intraosseous schwannoma of the jaw is rare. Primary schwannoma of the mandible presenting as a periapical radiolucency on a non-vital endodontically treated tooth has rarely been referred to in the English medical literature. A rare case of intraosseous schwannoma is reported in a 23-year-old woman. The patient presented clinically with a painful swelling on the right side of the mandible and with a radiologically ill-defined unilocular periapical lesion around the mesial root of the endodontically treated first molar. Surgical treatment involved complete excision of the lesion with a mesial and distal root resection. Histological and immunohistochemical examination showed that the lesion was a primary intraosseous schwannoma of the mandible. Immunohistochemical examination showed a positive and strong reaction for S-100 protein, characteristic of neural tumours. 1 year following surgery, there were no regional recurrences. Radiographically, mandibular intraosseous schwannoma is difficult to differentiate from bone tumours such as ameloblastoma, myxoma, fibrous dysplasia, neurofibroma, central giant cell lesion or periapical lesion, so it should be included in the list of possible periapical pathoses.

Distinct pseudogap and quasiparticle relaxation dynamics in the superconducting state of nearly optimally doped SmFeAsO0.8F0.2 single crystals

We use femtosecond spectroscopy to investigate the quasiparticle relaxation and low-energy electronic structure in a nearly optimally doped pnictide superconductor with T{c}=49.5 K. Multiple relaxation processes are evident, with distinct superconducting state quasiparticle recombination dynamics exhibiting a T-dependent superconducting gap, and a clear "pseudogaplike" feature with an onset above 180 K indicating the existence of a temperature-independent gap of magnitude Delta{PG}=61+/-9 meV above T{c}. Both the superconducting and pseudogap components show saturation as a function of fluence with distinct saturation fluences 4 and 40 microJ/cm{2}, respectively.

Inorganic molecular-scale MoSI nanowire-gold nanoparticle networks exhibit self-organized critical self-assembly

We investigate for the first time the topological characteristics of large molecular-scale inorganic networks self-assembled in solution using the unique sulfur-bonding chemistry of conducting MoSI molecular wires and gold nanoparticles (GNPs). The network self-assembly is shown to display power-law distribution of graph edges, indicating an intrinsic tendency to self-organize into scale-invariant critical state, without any external control parameter. We discuss the electronic transport properties of such networks particularly with regard to the possibility of data processing.

Fine structure in the electronic density of states near the Fermi energy of Al-Ni-Co decagonal quasicrystal from ultrafast time-resolved optical reflectivity

We measured the temperature and fluence dependence of the time-resolved photoinduced optical reflectivity in a decagonal Al71.9Ni11.1Co17.0 quasicrystal. We find no evidence for the relaxation of a hot thermalized electron gas as observed in metals. Instead, a quick diffusion of the hot nonthermal carriers approximately 40 nm into the bulk is detected, enhanced by the presence of a broad pseudogap. From the relaxation dynamics we find evidence for the suppression of the electronic density of states (DOS) at the Fermi energy with respect to the electronic DOS at approximately 13 meV away from the Fermi energy which is consistent with recent theoretical calculations.