Pressure-Induced Excitations in the Out-of-Plane Optical Response of the Nodal-Line Semimetal ZrSiS.

The anisotropic optical response of the layered, nodal-line semimetal ZrSiS at ambient and high pressure is investigated by frequency-dependent reflectivity measurements for the polarization along and perpendicular to the layers. The highly anisotropic optical conductivity is in very good agreement with results from density-functional theory calculations and confirms the anisotropic character of ZrSiS. Whereas the in-plane optical conductivity shows only modest pressure-induced changes, we found strong effects on the out-of-plane optical conductivity spectrum of ZrSiS, with the appearance of two prominent excitations. These pronounced pressure-induced effects can neither be attributed to a structural phase transition according to our single-crystal x-ray diffraction measurements, nor can they be explained by electronic correlation and electron-hole pairing effects, as revealed by theoretical calculations. Our findings are discussed in the context of the recently proposed excitonic insulator phase in ZrSiS.

Cooperative Cluster Jahn-Teller Effect as a Possible Route to Antiferroelectricity.

We report the observation of an antipolar phase in cubic GaNb_{4}S_{8} driven by an unconventional microscopic mechanism, the cooperative Jahn-Teller effect of Nb_{4}S_{4} molecular clusters. The assignment of the antipolar nature is based on sudden changes in the crystal structure and a strong drop of the dielectric constant at T_{JT}=31 K, also indicating the first-order nature of the transition. In addition, we found that local symmetry lowering precedes long-range orbital ordering, implying the presence of a dynamic Jahn-Teller effect in the cubic phase above T_{JT}. Based on the variety of structural polymorphs reported in lacunar spinels, also including ferroelectric phases, we argue that GaNb_{4}S_{8} may be transformable to a ferroelectric state, which would further classify the observed antipolar phase as antiferroelectric.

Complex magnetic order from multiple Ce-sites in Ce3Pd4Sn6.

Polycrystalline [Formula: see text] [Formula: see text] [Formula: see text] samples were synthesized by arc-melting and subsequent annealing at 970 K. Specific heat, electrical resistivity and magnetic susceptibility measurements are performed over a wide range in temperature and provide hints for the presence of a complex magnetic ordering below 3 K arising from three crystallographically independent Ce sites. This behaviour is driven by a complex interplay between ferro-, ferri-, and antiferromagnetic correlations among the Ce atoms.

On the nature of superconductivity in the anisotropic dichalcogenide NbSe2{CoCp2}x.

We present a detailed study of the superconducting properties of the weakly pinned, quasi-two-dimensional superconductor 2H-NbSe2, and its intercalated variant NbSe2{CoCp2}0.26. The intercalation of 2H-NbSe2 with the organometallic donor molecule cobaltocene (CoCp2) hardly affects the superconducting properties within the layers. However, the properties perpendicular to the layers change significantly due to the large expansion of the layer spacings of the host lattice in the c-direction by a factor of about two. In particular, the superconducting anisotropy factor Γ increases from 3.3 in the parent compound 2H-NbSe2 up to 4.4 in the intercalated species. Therefore, NbSe2{CoCp2}0.26 is an excellent candidate to analyze how the anisotropy effects the superconducting mechanism in layered dichalcogenides, and to evaluate the various models proposed in the literature to account for the anisotropy in 2H-NbSe2. While a two-gap model and an anisotropic single-gap model are competing concepts to describe the almost linear T(2)-dependence of ΔC/T in low-dimensional dichalcogenides, our comparative study suggests that a single-gap model with an anisotropic Fermi-surface is sufficient to capture the ΔC/T(T) behavior in our samples qualitatively.

Experimental and theoretical charge density studies at subatomic resolution.

Analysis of accurate experimental and theoretical structure factors of diamond and silicon reveals that the contraction of the core shell due to covalent bond formation causes significant perturbations of the total charge density that cannot be ignored in precise charge density studies. We outline that the nature and origin of core contraction/expansion and core polarization phenomena can be analyzed by experimental studies employing an extended Hansen-Coppens multipolar model. Omission or insufficient treatment of these subatomic charge density phenomena might yield erroneous thermal displacement parameters and high residual densities in multipolar refinements. Our detailed studies therefore suggest that the refinement of contraction/expansion and population parameters of all atomic shells is essential to the precise reconstruction of electron density distributions by a multipolar model. Furthermore, our results imply that also the polarization of the inner shells needs to be adopted, especially in cases where second row or even heavier elements are involved in covalent bonding. These theoretical studies are supported by direct multipolar refinements of X-ray powder diffraction data of diamond obtained from a third-generation synchrotron-radiation source (SPring-8, BL02B2).

A prototype hybrid 7π quinone-fused 1,3,2-dithiazolyl radical.

Reaction of 1,4-naphthoquinone and SNSMF(6) (M = As, Sb) in SO(2) solution in a 1 : 2 molar ratio led to the naphthoquinone fused 1,3,2-dithiazolylium salts, 3MF(6) quantitatively by multinuclear NMR (87% isolated yield of 3SbF(6)) via the cycloaddition and oxidative dehydrogenation chemistry of SNS(+) with formation of NH(4)SbF(6) and S(8). The product 3SbF(6) was fully characterized by IR, Raman, multinuclear {(1)H, (13)C, (14)N} NMR, elemental analysis, cyclic voltammetry and single crystal X-ray crystallography. The reduction of 3SbF(6) with ferrocene (Cp(2)Fe) in refluxing acetonitrile (CH(3)CN) led to the first isolation of a fused quinone-thiazyl radical, 3˙ in 73% yield. The prototype hybrid quinone-thiazyl radical 3˙ was fully characterized by IR, Raman microscopy, EI-MS, elemental analysis, solution and solid state EPR, magnetic susceptibility (2-370 K) and was found to form π*-π* dimers in the solid state as determined by single crystal X-ray crystallography. Furthermore, the thermal decomposition of 3˙ led to a novel quinone-fused 1,2,3,4-tetrathiine, 10 (x = 2) and the known 1,2,5-thiadiazole, 11. The energetics of the cycloadditon and oxidative dehydrogenation chemistry of SNS(+) and 1,4-naphthoquinone leading to 3SbF(6) were estimated in the gas phase and SO(2) solution by DFT calculations (PBE0/6-311G(d)) and lattice enthalpies obtained by the volume based thermodynamic (VBT) approach in the solid state. The gas phase ion energetics (ionization potential (IP) and electron affinity (EA)) of 3˙ are compared to related 1,3,2- and 1,2,3-dithiazolyl radicals.

Evolution of quantum criticality in CeNi(9-x)Cu(x)Ge(4).

Crystal structure, specific heat, thermal expansion, magnetic susceptibility and electrical resistivity studies of the heavy fermion system CeNi(9-x)Cu(x)Ge(4) (0≤x≤1) reveal a continuous tuning of the ground state by Ni/Cu substitution from an effectively fourfold-degenerate non-magnetic Kondo ground state of CeNi(9)Ge(4) (with pronounced non-Fermi-liquid features) towards a magnetically ordered, effectively twofold-degenerate ground state in CeNi(8)CuGe(4) with T(N) = 175 ± 5 mK. Quantum critical behavior, [Formula: see text], is observed for [Formula: see text]. Hitherto, CeNi(9-x)Cu(x)Ge(4) represents the first system where a substitution-driven quantum phase transition is connected not only with changes of the relative strength of the Kondo effect and RKKY interaction, but also with a reduction of the effective crystal field ground state degeneracy.

Pseudoentanglement of spin states in the multilevel 15N@C60 system.

We have prepared combined electron and nuclear spin pseudoentangled states Psi+/-27 and Phi+/-18 out of the total number of eight quantum states in the multilevel quantum system of a nitrogen atom with electron spin 3/2 and nuclear spin 1/2 encaged in the endohedral fullerene (15)N@C(60). Density matrix tomography was applied to verify the degree of entanglement.

Entanglement between an electron and a nuclear spin 1/2.

We report on the preparation and detection of entangled states between an electron spin 1/2 and a nuclear spin 1/2 in a molecular single crystal. These were created by applying pulses at ESR (9.5 GHz) and NMR (21 MHz, 46 MHz) frequencies. Entanglement was detected by using a special entanglement detector sequence based on a unitary back transformation including phase rotation.

Reproducability and transferability of topological properties; experimental charge density of the hexapeptide cyclo-(D,L-Pro)2-(L-Ala)4 monohydrate.

The charge density of a hexapeptide was determined from high-resolution CCD area-detector experiments at 100 K. Two datasets, one from a rotating anode and a second one from synchrotron radiation, were measured and the results are compared. The data are interpreted in terms of the 'rigid pseudoatom' model. The topology of the experimental density is analyzed and compared with the topology of the constituting amino acids, and shows good agreement. All critical points of the electron density at the covalent and hydrogen bonds, as well as those of the Laplacian, were located. With respect to the transferability of electronic and bond topological properties the six peptide bonds were compared with values given in the literature.

The diagnosis of onychomycosis in a geriatric population: a study of 450 cases in South Florida.

An investigative study was performed to determine the diagnosis of onychomycosis in a South Florida geriatric population. In this study, 450 cases of suspected onychomycosis involving men and women 65 years of age and older from a private practice office and two nursing home settings were used. Samples were taken from the hallux toenail and sent to a mycology laboratory for fluorescent potassium hydroxide (KOH) preparation and microscopic examination of a fungal culture. Of the 450 cases studied, 46.4% of the patients had a single fungal organism cultured, 30.4% had a mixed fungal infection cultured, and 23.1% had no fungal growth. Saprophytes were found in 59.9% of the 526 total fungal organisms cultured while dermatophytes were found in only 23.8%. The results of this investigation demonstrate that there may be a shift from isolated dermatophyte infection to mixed saprophyte infections in a geriatric population with onychomycosis.

Surgical outcomes in adult patients after repair of anterior segment trauma sustained during childhood.

PURPOSE: To evaluate the outcomes and possible benefit of surgery performed on adults for anterior segment trauma sustained during childhood. SETTING: Private practice. METHODS: A retrospective review of patient records was performed. Adult patients who had anterior segment surgery for injuries that occurred during childhood were identified. The surgical outcomes were evaluated to determine whether intervention was beneficial in this subgroup of patients. RESULTS: Six patients were identified. Preoperative best corrected visual acuity (BCVA) was 20/200 or worse in all patients. After surgery, the BCVA in 3 patients had improved to 20/30 or better and in 1 patient, to 20/60. The other 2 patients had less improvement; however, each noted subjective improvement in vision. No major intraoperative or postoperative complications occurred. CONCLUSION: In the absence of evidence of accompanying posterior segment trauma, surgery in adults to correct anterior segment damage from childhood trauma was safe and often beneficial.

Agostic deformations based on electron delocalization in the alkyllithium-complex [(2-(Me3Si)2CLiC5H4N)2.

Topological analysis of experimental and theoretical charge densities in the title complex [(2-(Me3Si)2CLiC5H4N)2] 1 reveals the nature of the agostic deformation postulated for this complex: delocalization of the Li-C bonding electrons over the entire agostic alkyl group controls the formation of an acute Li-C-Si angle and thus a sufficient electronic saturation of the electron deficient lithium atom via secondary interactions.

The antimicrobial properties of a urea-based handwash lotion with triclosan.

The purpose of this study was to determine and compare the antimicrobial action of a urea-based handwash lotion with triclosan with a lipid-depleting detergent-based handwash product with 4% chlorhexidine gluconate. The zones of inhibition produced by the two handwash lotions and the one produced by the positive control were similar against all strains of bacteria tested, indicating that a urea-based handwash lotion with triclosan is as effective as a lipid-depleting handwash lotion in inhibiting bacterial activity.

Dermatophyte test medium culture versus mycology laboratory analysis for suspected onychomycosis. A study of 100 cases in a geriatric population.

Onychomycosis is the most frequently encountered condition in podiatric practice in the United States. A variety of modalities are available to confirm the presumptive diagnosis of onychomycosis. This study was conducted to compare the results of in-office dermatophyte test medium cultures with those of mycology laboratory analysis for 100 cases of suspected onychomycosis in a geriatric population. The results demonstrated that 20% of the patients had dermatophyte involvement, 56% had saprophyte involvement, and 19% had yeast involvement. Only 50% of positive dermatophyte test medium cultures correlated with a positive microscopic fungal culture for dermatophytes. Given these results, it is questionable whether in-office dermatophyte test medium cultures should be routinely used in geriatric patients for the diagnosis of onychomycosis. The authors believe mycology laboratory testing with fluorescent potassium hydroxide preparations and microscopic fungal cultures to be superior to in-office dermatophyte test medium cultures for the diagnosis of onychomycosis in geriatric patients.

Effect of latanoprost on intraocular pressure in steroid-induced glaucoma.

PURPOSE: To study the effect of monotherapy with latanoprost 0.005% on intraocular pressure (IOP) in a prospective nonrandomized clinical trial of patients newly diagnosed with steroid-induced secondary open-angle glaucoma. PATIENTS AND METHODS: Eight patients (16 eyes) with newly diagnosed steroid-associated secondary open-angle glaucoma were prescribed latanoprost 0.005% once a day in each eye. The initial IOP before treatment served as an internal control for each eye. Intraocular pressure was remeasured after 1 month of monotherapy with latanoprost. Investigators (WJS) were blinded to initial IOP at the time of remeasurement. After discontinuation of steroids, IOP was rechecked. If IOP was stable, latanoprost was discontinued. Intraocular pressure was rechecked 2 to 4 weeks later to confirm an association with steroid use. RESULTS: Intraocular pressure was significantly decreased after treatment with latanoprost (18.3 +/- 2.8 mm Hg) compared with initial IOP (25.3 +/- 9.1 mm Hg). This change represented a 28% decrease in IOP compared with baseline levels. Average IOP after discontinuation of steroids and latanoprost (17.3 +/- 1.4 mm Hg) did not differ from IOP measured during treatment with latanoprost, but it was significantly less than the initial IOP before treatment. No adverse effects were noted. CONCLUSIONS: Monotherapy with latanoprost is safe and effective in patients with steroid-induced glaucoma. Advantages include lack of systemic side effects and convenient once-daily dosing.

Yttrium calix[4]arene complexes. Silylation and silylamine elimination reactions on model oxo surfaces.

The synthesis and the spectroscopic and structural characterization of lower-rim-silylated and rare-earth-metalated calix[4]arenes are presented. Hexamethyldisilazane, HN(SiMe3)2, reacted in a selective manner with [p-tert-buttylcalix[4]arene]H4 (1) in refluxing mesitylene to give the 1,3-silylated product [p-tert-butylcalix[4]arene(SiMe3)2]H2 (2) in high yield. The molecular structure of compound 2, as revealed by X-ray crystallography, shows the pinched cone conformation of the calixarene bowl, featuring hydrogen bonding between the phenylsilyl ether and phenolic oxygen atoms (O...O, 2.838 A). From the reaction of the sterically more crowded tetraphenyldimethyldisilazane, HN(SiMePh2)2, only starting material could be recovered. In contrast, tetramethyldisilazane, HN(SiHMe2)2, afforded the tetrakis-silylated product [p-tert-butylcalix[4]arene(SiHMe2)4] (3) in hexane solution at ambient temperature. A single-crystal X-ray diffraction study of compound 3 established the 1,2-alternate conformation, which is also present in solution, as indicated by 1H NMR spectroscopy. The yttrium complex Y[N(SiHMe2)2]3(THF)2 (4) exchanged all of its silylamide ligands when treated with an equimolar amount of 1 in toluene at ambient temperature to yield compound 5, as indicated by IR and NMR spectroscopy. The molecular structure of 5 revealed a centrosymmetric dimer of composition [Y(p-tert-butylcalix[4]arene(SiHMe2)(THF)]2. Three of the deprotonated phenolic oxygen atoms of the calixarene bowl bind to the metal center, two as terminal ligands and one in a bridging mode, while the fourth undergoes in situ silylation (nu(SiH) 2127 cm-1). The distorted-trigonal-bipyramidal coordination geometry is completed by a THF molecule. Bis-silylated 2 reacted with 4 to form the heteroleptic complex (Y[p-tert-butylcalix[4]arene(SiMe3)2][N(SiHMe2)2]) (6). Crystal data: C50H72O4Si2 (2), triclinic, P1, a = 12.8914(3) A, b = 14.9270(5) A, c = 15.1652(4) A, alpha = 77.293(2) degrees, beta = 65.019(2) degrees, gamma = 72.234(2) degrees, Z = 2; C52H80O4Si4 (3), triclinic, P1, a = 10.1774(2) A, b = 14.1680(2) A, c = 18.7206(2) A, alpha = 95.8195(8) degrees, beta = 95.5294(8) degrees, gamma = 98.1098(7) degrees, Z = 2; C100H132O10Si2Y2, 2(C6H6) (5), triclinic, P1, a = 13.2625(4) A, b = 14.5894(3) A, c = 17.0458(5) A, alpha = 65.0986(14) degrees, beta = 77.8786(8) degrees, gamma = 85.5125(13) degrees, Z = 1.

Evaluations of the interface between amalgam and dentin with a single component dentin bonding system.

The purpose of this scanning electron microscope study was to observe the dentin-amalgam interface after utilizing a standard restorative liner and a single-component dentin adhesive. Continuous interface gaps of over 15 mu were observed in specimens containing no lining and Copal varnish. Discontinuous 5 microns gaps were observed in specimens treated with PQ1. Additionally, specimens treated with PQ1 exhibited resin interpenetration into the dentin surfaces.

Microleakage of a condensable resin composite: an in vitro investigation.

OBJECTIVE: The purpose of this investigation was to evaluate microleakage in Class II cavities restored with the condensable resin composite SureFil, placed with or without a liner and 1 of 2 different dentin bonding agents. METHOD AND MATERIALS: Extracted noncarious human teeth were randomly divided into 4 groups of 15 each and restored according to manufacturer's instructions: group 1, SureFil and Prime & Bond NT; group 2, SureFil and PQ1; group 3, SureFil, PermaFlow, and PQ1; group 4, Heliomolar and Syntac Single-Component (control). Specimens were stored in 37 degrees C water for 24 hours. All specimens were thermocycled between 5 degrees C and 55 degrees C for 500 cycles. Each specimen was immersed in 0.2% basic fuchsin dye for 24 hours and then sectioned longitudinally and horizontally. Dye penetration at enamel and cementum margins were viewed at x30 magnification by 2 independent, calibrated evaluators. Specimens exhibiting dye penetration > or = 0.1 mm beyond the cavosurface margin were considered to have leakage. RESULTS: Chi-square tests revealed no statistically significant differences in the presence of microleakage when all groups were analyzed together. However, 2 by 2 comparisons revealed that group 3 had significantly fewer specimens with microleakage than did group 1, 2, or 4. CONCLUSION: To limit microleakage, a flowable composite should be used as a liner when a condensable composite material is used.

Use of a compomer in Class V restoration: a microleakage study.

OBJECTIVE: The purpose of this investigation was to evaluate the microleakage of Class V lesions restored with a compomer material (Dyractflow) using 2 single-bottle bonding systems. METHOD AND MATERIALS: Sixty-four Class V cavity preparations were made on 32 sound, extracted human premolars, 1 preparation on the facial surface and 1 on the lingual surface. Teeth were then randomly divided into 2 groups. Group 1, which served as the control group, was restored as follows: group 1a, facial surface with PQ1 single-bottle bonding system plus TPH resin composite; group 1b, lingual surface with Prime & Bond NT single-bottle bonding system plus TPH. Group 2 was restored as follows: group 2a, facial surface with PQ1 plus Dyractflow compomer material; group 2b, lingual surface with Prime & Bond NT plus Dyractflow. After 24 hours of storage in water and subsequent thermocycling, each specimen was immersed in 0.2% basic fuchsin dye for 24 hours. The teeth were sectioned longitudinally and horizontally, and dye penetration at enamel and cementum margins was viewed at x30 magnification by 2 independently calibrated evaluators. Specimens were evaluated as either having leaked or not having leaked. RESULTS: No statistically significant differences in microleakage were noted between group 1 and group 2 specimens. CONCLUSION: Both single-bottle bonding systems, PQ1 and Prime & Bond NT, demonstrated equal effectiveness in reducing microleakage beneath compomer and composite restorations.