Cytogenetic analysis of two related Deltochilum (Coleoptera,Scarabaeidae) species: Diploid number reduction,extensive heterochromatin addition and differentiation

Male mitotic and meiotic chromosomes of two species of the genus Deltochilum (Scarabaeidae) were analyzed through conventional staining, C-banding, base-specific fluorochromes, silver nitrate staining (AgNO₃) and FISH (45S rDNA). The two species possessed karyotypes with 2n = 14, neo-XY and meta-submetacentric chromosomes. The analysis of constitutive heterochromatin (CH) revealed mainly diphasic chromosomes in the two species, showing heterochromatic long arms. Silver nitrate staining labeled the blocks corresponding to CH in D. (Deltohyboma) aff morbillosum while in D. (Deltohyboma) calcaratum, AgNO₃ staining revealed only the CH blocks of the diphasic autosomes. The fluorochrome staining revealed in D. (D.) calcaratum the diphasic autosomes and the sex chromosomes with CMA₃⁺ blocks, and in D. (D.) aff morbillosum, the GC-rich sequences were restricted to the terminal regions of the long arms of the pairs 1 and 2 and the X. The FISH revealed 45S rDNA sites in two autosomic pairs and in the X chromosome. The analyses performed allowed for the identification of cytogenetic markers and the discussion of possible chromosome rearrangements that have been involved in the karyotypic differentiation of these species mainly related to the repetitive genome.     

The first cytogenetic characterization of the poisonous black widow spider Latrodectus gr. curacaviensis from Brazil,with chromosomal review of the family Theridiidae (Arachnida,Araneae)

In this paper we present, for the first time, cytogenetical data on Latrodectus gr. curacaviensis (Theridiidae) from Brazil, as well as the first data on meiosis and sex chromosome system of this genus. Testes were submitted to colchicine, hypotonic, and fixation treatment, and chromosomal preparations were stained with Giemsa solution. The analysis showed 2n = 26 telo/acrocentric chromosomes in spermatogonial metaphases. Metaphase I exhibited 12 autosomal bivalents and two sex chromosome univalents (12II + X₁X₂). All bivalents revealed one terminal chiasma. Metaphases II confirmed the sex chromosome system, showing 12 autosomes or 12 autosomes plus two X chromosomes, respectively. Male karyotype prevailing in theridiids is formed by 2n = 22 chromosomes, including sex chromosome system X₁X₂ in all species. The Latrodectus species of the geometricus clade analyzed until now showed smaller diploid number (2n♀ = 16 and 2n♀ = 18) than the species of the mactans clade (2n♀ = 24 and 2n♀ = 26). Thus, according to the chromosome number, the examined Latrodectus species seems to be related to the mactans clade.     

Structural chemistry and zeolitic properties of mixed oxalates with two open-framework types based on eight coordinate metals

Two families of open-framework materials have been obtained from the assembly of MO₈ polyhedra and oxalate groups as building blocks. The compounds can be formulated as [MM′(C₂O₄)₄]²⁻(M″_y)²⁺ · (4 + x)H₂O (y is 2 for monovalent M″ metals and 1 for divalent M″ metals), in which the sum of the valences of the two metals M and M′ involved in the anionic framework is six. The water molecules and counter cations, located in the voids of the structure, lead to zeolitic or cation dynamic properties.     

Mechanisms of karyotype differentiation in Cassidinae sensu lato (Coleoptera,Polyphaga, Chrysomelidae) based on seven species of the Brazilian fauna and an overview of the cytogenetic data

Among the subfamilies of Chrysomelidae, Cassidinae sensu lato (s.l.) includes 6000 species distributed in 43 tribes. Approximately 100 of these species were cytogenetically analyzed and most of them presented 2n = 18 = 16 + Xy_p, which was smaller than 2n = 20 = 18 + Xy_p considered basal for Polyphaga. However, some groups of species presented maintenance of the basal diploid number and others showed increase in this number. Certain species of the latter group also exhibited variation in the type of sex chromosome system (SCS). Considering the recent taxonomic revision accomplished for the Cassidinae s.l. species, the existence of phylogenetic relationship for some species of this subfamily, the high diversity of species of this group in the Neotropical region, and the low number of Cassidinae s.l. species karyotyped so far, the aim of the present work was to establish the main mechanisms involved in the karyotype evolution of this subfamily through the study of seven species of the Brazilian fauna and overview of the cytogenetic data. The individuals were collected in southeast and south of Brazil. The chromosomal preparations obtained from embryo and testes of adult males were stained with Giemsa solution. The species Agroiconota inedita (2n = 42 = 40 + Xy_p), Charidotella (s.str.) immaculata (2n = 22 = 20 + Xy_p), Charidotella (s.str.) sexpunctata (2n = 22 = 20 + Xy_p), and Stolas chalybaea (2n = 24 = 22 + Xy_p) revealed diploid number higher than that established as basal for Polyphaga and biarmed chromosomes. The karyotype of Cteisella confusa, Deloyala cruciata, and Metriona elatior showed the chromosomal formulae 2n = 18 = 16 + Xy_p considered modal for Cassidinae s.l. and biarmed chromosomes. The seven species exhibited easily identified sex chromosomes due to their size and/or morphology. The analysis of meiotic cells of all the species showed pachytenes with a positively heteropycnotic block probably corresponding to the sex chromosomes; diplotenes with a high number of bivalents with two chiasmata and sex chromosomes in a parachute configuration, and metaphases II that confirmed the chromosomal morphology, the type of SCS, and the regular segregation of all chromosomes. The data regarding to the number and morphology of the chromosomes, their behaviour during meiosis, and type of SCS were inedit for the majority of these species. In relation to the all Cassidinae s.l. species that presented SCS of the Xy_p type, A. inedita was that with the highest diploid number. Furthermore, this work reported for the first time the cytogenetic information of representatives of the genera Cteisella and Metriona. Taking into account the phylogenetic and cytogenetic data of Cassidinae s.l. species, the karyotype differentiation of this group seems to have occurred from the basal karyotype of Polyphaga by decrease in the chromosome number and subsequent increase in this number. Pericentric inversion, centric fusion and fission seem to have been the main mechanisms that promoted the evolution of the autosomes. However, in the sex chromosome evolution, the mechanisms involved were centric fission and/or chromosomal translocation.     

Electrical properties of yttrium doped strontium titanate with A-site deficiency as potential anode materials for solid oxide fuel cells

Yttrium doped strontium titanate with A-site deficiency ((Y_0.08Sr_0.92)_1 ? xTiO_3 ? δ) was synthesized by conventional solid state reaction. The deficiency limit of A-site in (Y_0.08Sr_0.92)_1 ? xTiO_3 ? δ is below 6 mol% in Ar/H₂ (5%) at 1500 °C. The sinterability of (Y_0.08Sr_0.92)_1 ? xTiO_3 ? δ samples decreases slightly with increasing A-site deficiency level (x). The ionic conductivity of (Y_0.08Sr_0.92)_1 ? xTiO_3 ? δ samples increases while the electronic conductivity decreases with increasing A-site deficient amount. The defect chemistry analysis indicates that the introduction of A-site deficiency results in not only the increase of oxygen vacancy concentration but also the decrease of Ti³⁺-ion concentration. The latter plays the main role in the electrical conduction. (Y_0.08Sr_0.92)_1 ? xTiO_3 ? δ shows good thermal-cyclic performance in electrical conductivity and has an excellent chemical compatibility with YSZ electrolyte below 1500 °C.     

Experimental study on the influence of low-frequency and low-intensity ultrasound on the permeability of the Mycobacterium smegmatis cytoderm and potentiation with levofloxacin

Tuberculosis is an infectious disease caused by the bacterium M. tuberculosis. The aim of this study was to investigate the bactericidal effect and underlying mechanisms of low-frequency and low-intensity ultrasound combined with levofloxacin treatment against M. smegmatis (a surrogate of M. tuberculosis). As part of this study, M. smegmatis was continuously irradiated with low frequency ultrasound (42 kHz) using several different doses whereby both intensity (0.138, 0.190 and 0.329 W/cm²) and exposure time (5, 15 and 20 min) were varied. Flow cytometric analyses revealed that the permeability of M. smegmatis increased following ultrasound exposure. The survival rate, structure and morphology of bacteria in the lower-dose (I_SATA = 0.138 W/cm² for 5 min) ultrasound group displayed no significant differences upon comparison with the untreated group. However, the survival rate of bacteria was significantly reduced and the bacterial structure was damaged in the higher-dose (I_SATA = 0.329 W/cm² for 20 min) ultrasound group. Ultrasound irradiation (0.138 W/cm²) was subsequently applied to M. smegmatis in combination with levofloxacin treatment for 5 min. The results demonstrated that the bactericidal effect of ultrasonic irradiation combined with levofloxacin is higher compared to ultrasound alone or levofloxacin alone.     

Band diagram for chemical vapor deposition diamond surface conductive layer: Presence of downward band bending due to shallow acceptors

The properties of surface conductivity (SC) of impurity-non-doped CVD diamond (001) samples were studied by various methods of sheet-resistance (R_S) measurement, Hall-effect measurement, XPS, UPS, SES, SR-PES, PEEM and 1D band simulation taking into account special emphases on deriving the information about the surface band diagram (SBD). The R_S values in UHV conditions were determined after no-annealing or 200 ～ 300 °C annealing in UHV. C 1 s XPS profiles were measured in detail in bulk-sensitive and surface-sensitive modes of photoelectron detection. The energy positions of valence band top (E_V) relative to the Fermi level (E_F) in UHV conditions after no-annealing or 200 ～ 300 °C annealing in UHV were determined. One of the samples was subjected to SR-PES, PEEM measurements. The SBDs were simulated by a band simulator from the determined R_S and E_V ? E_F values for three samples based on the two models of surface conductivity, namely, so-called surface transfer doping (STD) model and downward band bending with shallow acceptor (DBB/SA) model. For the DBB/SA model, there appeared downward bends of SBDs toward the surface at a depth range of ～ 1 nm. C 1 s XPS profiles were then simulated from the simulated SBDs. Comparison of simulated C 1 s XPS profiles to the experimental ones showed that DBB/SA model reproduces the C 1 s XPS profiles properly. PEEM observation of a sample can be explained by the SBD based on the DBB/SA model. Mechanism of SC of CVD diamonds is discussed on the basis of these findings. It is suggested that the STD model combined with SBD of DBB/SA model explains the surface conductivity change due to environmental changes in actual cases of CVD diamond SC with the presence of surface E_F controlling defects.     

Enhancement microwave dielectric properties of La(Mg0.5Sn0.5)O3 ceramics by substituting La3+ with Sm3+

The microwave dielectric properties of La_1?xSm_x(Mg_0.5Sn_0.5)O₃ ceramics were examined with a view to their exploitation for mobile communication. The La_1?xSm_x(Mg_0.5Sn_0.5)O₃ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the La_0.97Sm_0.03(Mg_0.5Sn_0.5)O₃ ceramics revealed no significant variation of phase with sintering temperatures. Apparent density of 6.59 g/cm³, dielectric constant (ε_r) of 19.9, quality factor (Q×f) of 70,200 GHz, and temperature coefficient of resonant frequency (τ_f) of ?77 ppm/°C were obtained for La_0.97Sm_0.03(Mg_0.5Sn_0.5)O₃ ceramics that were sintered at 1500 °C for 4 h. The dielectric constant, and τ_f of La_0.97Sm_0.03(Mg_0.5Sn_0.5)O₃ ceramics were almost independent with the sintering temperature as the sintering temperature varied from 1450 to 1600 °C.     

The improvement in dielectric and ferroelectric performance of PZT–PZN ceramics by thermal treatment

Pyrochlore-free lead zirconate titanate – lead zinc niobate ceramics have been systematically investigated in the as-sintered condition as well as after annealing. The ceramics were characterized by dielectric spectroscopy and Sawyer–Tower polarization (P–E) measurements. The powders of Pb[(Zr_1/2Ti_1/2)_(1−x)–(Zn_1/3Nb_2/3)_x]O₃, where x = 0.1, 0.3 and 0.5 were prepared using the columbite–(wolframite) precursor method. The general trend seems to indicate that the annealed samples become more normal-ferroelectric-like behavior as opposed to the relaxor-ferroelectric-like behavior observed in the as-sintered state. The as-sintered 0.9PZT–0.1PZN ceramic exhibited weak relaxor-ferroelectric behavior, with a relatively low dielectric constant maximum of 14,000 measured at 1 kHz. Annealing resulted in a transition to normal-ferroelectric-like behavior, a shift in the dielectric maximum temperature from 360 °C to 350 °C, and a dramatic increase in the dielectric constant at 1 kHz to a maximum value of 35,000 for the longer anneal. After thermal annealing at 900 °C for one week a strong enhancement of remanent polarization (P_r) was observed.     

Experimental investigation of flame spreading over pure methane hydrate in a laminar boundary layer

Flame spreading over pure methane hydrate in a laminar boundary layer is investigated experimentally. The free stream velocity (U_∞) was set constant at 0.4 m/s and the surface temperature of the hydrate at the ignition (T_s) was varied between ?10 and ?80 °C. Hydrate particle sizes were smaller than 0.5 mm. Two types of flame spreading were observed; “low speed flame spreading” and “high speed flame spreading”. The low speed flame spreading was observed at low temperature conditions (T_s = ?80 to ?60 °C) and temperatures in which anomalous self-preservation took place (T_s = ?30 to ?10 °C). In this case, the heat transfer from the leading flame edge to the hydrate surface plays a key role for flame spreading. The high speed flame spreading was observed when T_s = ?50 and ?40 °C. At these temperatures, the dissociation of hydrate took place and the methane gas was released from the hydrate to form a thin mixed layer of methane and air with a high concentration gradient over the hydrate. The leading flame edge spread in this premixed gas at a spread speed much higher than laminar burning velocity, mainly due to the effect of burnt gas expansion.     

Continuous measurements of stable carbon isotopes in CO2 with a near-IR laser absorption spectrometer

A near-IR laser absorption spectrometer using a technique of wavelength modulation spectroscopy is used to measure stable carbon isotope ratios of ambient CO₂ (δ¹³C) via the absorption lines ¹²CO₂ R(17) (2ν₁ + ν¹₂ − ν¹₂ + ν₃) at 4978.205 cm⁻¹ and ¹³CO₂ P(16) (ν₁ + 2ν₂ + ν₃) at 4978.023 cm⁻¹. The isotope ratios are measured with a reproducibility of 0.02‰ (1σ) in a 130-s integration time over a 12-h period. The humidity effect on δ¹³C values has been evaluated in laboratory experiments. The δ¹³C values of CO₂ in ambient air were measured continuously over 8 days and agreed well with those from isotope ratio mass spectrometry of canister samples. The spectrometer is thus capable of real-time, in situ measurements of stable carbon isotope ratios of CO₂ under ambient conditions.     

Characterization of Young’s modulus of silicon versus temperature using a “beam deflection” method with a four-point bending fixture

Young’s modulus (E) and Poisson’s ratio (ν) are dependent upon the direction on the silicon surface. In this work, E and ν of silicon have been calculated analytically for any crystallographic direction of silicon by using compliance coefficients (s₁₁, s₁₂, and s₄₄), and the values of E are confirmed experimentally by using a “beam deflection” method with a four-point bending fixture. Experimental results for E as a function of temperature from −150 °C to +150 °C are presented for (0 0 1) and (1 1 1) silicon wafers.     

Thermal and sonochemical synthesis of porous (Ce,Zr)O2 mixed oxides from metal β-diketonate precursors and their catalytic activity in wet air oxidation process of formic acid

Porous (Ce_0.5Zr_0.5)O₂ solid solutions were prepared by thermolysis (T = 285 °C) or sonolysis (20 kHz, I = 32 W cm⁻², P_ac = 0.46 W mL⁻¹, T = 200 °C) of Ce(III) and Zr(IV) acetylacetonates in oleylamine or hexadecylamine under argon followed by heat treatment of the precipitates obtained in air at 450 °C. Transmission Electron Microscopy images of the samples show nanoparticles of ca. 4–6 nm for the two synthetic approaches. The powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and μ-Raman spectroscopy of solids obtained after heat treatment indicate the formation of (Ce_0.5Zr_0.5)O₂ solid solutions with a metastable tetragonal crystal structure for the two synthetic routes. The specific surface area of the samples varies between 78 and 149 m² g⁻¹ depending on synthesis conditions. The use of Barrett–Joyner–Halenda and t-plot methods reveal the formation of mixed oxides with a hybrid morphology that combines mesoporosity and microporosity regardless of the method of preparation. Platinum nanoparticles were deposited on the surface of the mixed oxides by sonochemical reduction of Pt(IV). It was found that the materials prepared by sonochemistry exhibit better resistance to dissolution during the deposition process of platinum. X-ray photoelectron spectroscopy analysis shows the presence of Pt(0) and Pt(II) on the surface of mixed oxides. Porous (Ce_0.5Zr_0.5)O₂ mixed oxides loaded with 1.5 %wt. platinum exhibit high activity in catalytic wet air oxidation of formic acid at 40 °C.     

Synthesis and characterisation of Cr3+-containing NASICON-related phases

Chromium-containing NASICON-related phosphates of the type Na_(1+x)Cr_xM_(2−x)P₃O₁₂) (M = Ti, Hf, Zr) have been synthesised by solid state reaction and structurally characterised by Rietveld refinement of the powder X-ray diffraction data. Materials of composition A_(1+x)/2Cr_xZr_(2−x)P₃O₁₂ (A = Cd, Ca, Sr), have also been prepared and characterised. The crystal structure of Na_(1+x)Cr_xM_(2−x)P₃O₁₂ corresponds to R-3c symmetry for x values ranging from 0.15 to 2.00, whereas compounds of composition A_(1+x)/2Cr_xZr_(2−x)P₃O₁₂ corresponding to R-3c are obtained when x ≤ 1.00 for Sr²⁺ and Ca²⁺, and x ≤ 1.50 for Cd²⁺. The polarizing effect of the two different metal ions A and M on the phosphorus atom and the P–O bond was studied by both ³¹P MAS NMR and infrared spectroscopy and shows that the electron density on the phosphorus, and thus the strength of the P–O bonds, are affected by both the interstitial (A) and the structural (M) metal ions.     

Synthesis of smooth and superconducting (Cu, C)–Ba–O/CaCuO2/(Cu, C)–Ba–O films using SrCuO2 buffer

Artificially stacked structures of [(infinite layer CaCuO₂)_k/(superconducting (Cu, C)Ba₂CuO_x:(Cu, C)-1201)_l]_m were fabricated on SrCuO₂ buffer layer by means of sequential deposition of each block using pulsed laser deposition. Smooth and epitaxial growth all over the deposition cycles of (Cu, C)-1201 and CaCuO₂ were confirmed by streak patterns of in situ RHEED. In comparison with (Cu, C)-1201 single layer films, the artificial stacking resulted in a rise of superconducting properties, T_c-onset and T_c(ρ=0) up to 95 K and 65 K, respectively.     

Dielectric properties of PIN–PT ceramics under compressive stress

Lead indium niobate, Pb(In_1/2Nb_1/2)O₃ or (PIN), is an interesting ferroelectric material, because it can be changed from a disordered state to ordered state by long-time thermal annealing. However, the temperature related to the maximum dielectric constant (T_max) of PIN in relaxor phase is low (at 1 kHz, T_max = 66 °C). In this study, to increasing T_max of PIN, lead titanate, PbTiO₃(PT) was thus added to PIN with compositions (1 − x)PIN–xPT (for x = 0.1–0.5). The influence of stress on the dielectric properties of (1 − x)PIN–xPT ceramics was then investigated. The dielectric properties were measured under various uniaxial compressive stress up to 400 MPa. The results showed that the superimposed compression load reduced the dielectric constant in 0.9PIN–0.1PT. For the other compositions, the dielectric constants first increased with the compressive stress, and then decreased when the stress was further increased up to 400 MPa. The dielectric loss tangent of all composition was found to decrease with increasing compressive stress.     

The in-situ solid-state NMR spectroscopy investigation of alcoholic lactose suspensions

The polymorphic forms of lactose in alcoholic suspensions have been determined by ¹³C CP-MAS NMR spectroscopy, employing hand-made glass inserts. Suspensions of alpha lactose monohydrate (Lα·H₂O) with particle size between 2 and 200 μm were prepared by 24 h reflux or by storage for 28 d in anhydrous ethanol without agitation. These suspensions were compared to an ethanolic sub-micron lactose suspension provided by a 3 M Health Care (Loughborough). The ¹³C CP-MAS NMR spectra indicated that Lα·H₂O dehydrated to stable anhydrous alpha lactose polymorph (Lα_S) whilst suspended in ethanol. In addition, strong ethanol ¹³C resonances were observed for some samples, indicating a liquid–solid interaction between the ethanol and lactose surface. Replacement of ethanol with anhydrous methanol, n-butanol and 3-methylbutan-2-ol implied that the solvent mediated dehydration of Lα·H₂O to Lα_S occurs as a result of sterically controlled interactions.     

Ionic conductivity of polymer electrolyte membranes based on polyphosphazene with oligo(propylene oxide) side chains

A polyphosphazene [NP(NHR)₂]_n with oligo[propylene oxide] side chains − R = –[CH(CH₃)–CH₂O]_m–CH₃ (m = 6 – 10) was synthesized by living cationic polymerisation and polymer-analogue substitution of chlorine from the intermediate precursor [NPCl₂]_n using the corresponding primary amine RNH₂. The polymer had an average molecular weight of 3.3 × 10⁵ D. Polymer electrolytes with different concentrations of dissolved lithium triflate (LiCF₃SO₃) were prepared. Mechanically stable polymer electrolyte membranes were formed using UV radiation induced crosslinking of the polymer salt mixture in the presence of benzophenone as photoinitiator. The glass transition temperature of the parent polymer was found to be − 75 °C before cross linking. It increases after crosslinking and with increasing amounts of salt to a maximum of − 55 °C for 20 wt.% LiCF₃SO₃. The ionic conductivity was determined by impedance spectroscopy in the temperature range 0–80 °C. The highest conductivity was found for a salt concentration of 20 wt.% LiCF₃SO₃: 6.5 × 10^− 6 S·cm^− 1 at 20 °C and 2.8 × 10^− 4 S cm^− 1 at 80 °C. The temperature dependence of the conductivities was well described by the MIGRATION concept.     

Oxygen diffusion and surface exchange studies on (La0.75Sr0.25)0.95Cr0.5Mn0.5O3−δ

Oxygen tracer diffusion coefficient (D^⁎) and surface exchange coefficient (k^⁎) have been measured for (La_0.75Sr_0.25)_0.95Cr_0.5Mn_0.5O_3−δ using isotopic exchange and depth profiling by secondary ion mass spectrometry technique as a function of temperature (700–1000 °C) in dry oxygen and in a water vapour-forming gas mixture. The typical values of D^⁎ under oxidising and reducing conditions at ∼ 1000 °C are 4 × 10^− 10 cm² s^− 1 and 3 × 10^− 8 cm² s^− 1 respectively, whereas the values of k^⁎ under oxidising and reducing conditions at ∼ 1000 °C are 5 × 10^− 8 cm s^− 1 and 4 × 10^− 8 cm s^− 1 respectively. The apparent activation energies for D^⁎ in oxidising and reducing conditions are 0.8 eV and 1.9 eV respectively.     

Neutron diffraction study of the CeFeSi-type RTiGe compounds (R=Pr,Nd, Tb–Er)

Neutron diffraction experiments were carried out on polycrystalline RTiGe (R=Pr, Nd, Tb–Er) samples. These compounds crystallise with the tetragonal CeFeSi-type structure (space group P4/nmm). This structure is closely related to the ThCr₂Si₂-type and can be described as “BaAl₄ blocks” connected via R–R contacts (“W blocks”). All the compounds are antiferromagnetic. PrTiGe and NdTiGe are characterised by an easy-plane sine-modulated structure characterised by a wave vector k=0,0,q_z=0.242 and 0.334 below 62 and 128 K, respectively. Below 80 K, NdTiGe exhibits a commensurate arrangement, which consists on ferromagnetic (0 0 1) Nd layers coupled antiferromagnetically along the c direction with the sequence ++−−. This commensurate magnetic ordering also occurs in TbTiGe, DyTiGe, HoTiGe and ErTiGe below 312, 185, 124 and 36 K, respectively. In the first three compounds (R=Tb−Ho), the magnetic moment is aligned along the c-axis whereas it is localised in the basal plane in ErTiGe. In all the RTiGe compounds, the magnitude of the ordered moments at 2 K amounts nearly to the free ion magnetic moment (gJ) values for the respective R³⁺ ions.