The disinfection effect of a novel continuous-flow water sterilizing system coupling dual-frequency ultrasound with sodium hypochlorite in pilot scale

In this paper, a self-designed novel continuous-flow water disinfection system coupling dual-frequency ultrasound (US) with chemical disinfectant sodium hypochlorite (NaClO) was tested in a pilot scale using a simulated effluent containing Bacillus subtilis (B. subtilis), one of the indicators of water treatment efficiency. A suspension having a B. subtilis concentration of approximately 10⁴ CFU/mL was introduced into the system to (1) investigate disinfection efficiency of US pretreatment with NaClO (US + NaClO) and simultaneous US and NaClO (US/NaClO) disinfection under different single frequencies; (2) further examine the disinfection efficiency of these two processes with dual-frequency US; and (3) identify dosage reduction of chlorine in this disinfection system. The results demonstrated that lower dual-frequency (17 kHz + 33 kHz) US pretreatment with NaClO disinfection and simultaneous higher dual-frequency (70 kHz + 100 kHz) US and NaClO were beneficial to bacterial inactivation in terms of sterilizing efficiency. It has also been observed that US pretreatment with lower combination of 17 + 33 kHz frequencies showed better enhancement in which log reduction reached to 3.82 after 10 min chlorine reaction (chlorine alone was 0.22 log reduction), nearly 1 log reduction higher than single frequencies at the same constant power. Consequently, at equivalent power dissipation levels, US of lower frequencies combination pretreatment with NaClO disinfection performed such a promising process that one-thirds (from 12 mg/L NaClO reduced to 8 mg/L NaClO) of the required NaClO dosage was reduced for the ideal disinfection efficiency of 4 log reduction, namely 100% disinfection. And the utilization efficiency of NaClO was increased from 37.67% to 85.25% in 30 min of treatment time using an optimized combination of pretreatment and chlorination.     

A novel approach to quantitative ultrasonic naked gene delivery and its non-invasive assessment

The purpose of this study was to investigate practical, safe, easy-to-use, non-cytotoxic, and reliable parameters to apply to an ultrasound (US) naked gene therapy system. The ultrasound pressure at the point of cell exposure was measured using a calibrated hydrophone and the intensity calculated. An acoustic power meter calibrated using a hydrophone was used to measure the power of the transducer. Four cell types were exposed to US with different exposure times and intensities. Fluorescent microscopy, spectrophotometry, scanning electron microscope, laser scanning confocal microscopy, flow cytometry and histogram analysis were used to evaluate the results of the study. The plasmid of green fluorescent protein (GFP) served as the reporter gene. The energy accumulation E in US gene delivery for 90% cell survival was defined as the optimal parameters (E = 3.56 ± 0.06), and at 80% cell survival was defined as the damage threshold (E = 59.67 ± 3.54). US safely delivered GFP into S180 cells (35.1 kHz) at these optimal parameters without obvious damage or cytotoxity in vitro. Exposed cell function was proved normal in vivo. The transfection rate was 35.83 ± 2.53% (n = 6) in viable cells, corresponding to 90.17 ± 1.47% (n = 6) cell viability. The intensity of GFP expression showed a higher fluorescent peak in the group of adeno-associated virus GFP vector (AVV-GFP) than in the control group (P < 0.001). The effect of US gene delivery and cell viability correlated as a fifth order polynomial with US intensity and exposure time. With optimal parameters, US can safely deliver naked a gene into a cell without damage to cell function. Both optimal uptake and expression of gene depend on the energy E at 90% cell survival. E can be applied as a control factor for bioeffects when combined with other parameters. Stable caviation results in optimal parameters for gene delivery and the transient caviation may cause cell damage, which will bring about a sharp rise of permeabilization. The results may be applied to the development of a novel clinical gene therapeutic system.     

Ultrasound-intensified laccase production from Trametes versicolor

An efficient intermittent ultrasonic treatment strategy was developed to improve laccase production from Trametes versicolor mycelia cultures. The optimized strategy consisted of exposing 2-day-old mycelia cultures to 5-min ultrasonic treatments for two times with a 12-h interval at the fixed ultrasonic power and frequency (120 W, 40 kHz). After 5 days of culture, this strategy produced the highest extracellular laccase activity of 588.9 U/L among all treatments tested which was 1.8-fold greater than the control without ultrasound treatment. The ultrasonic treatment resulted in a higher pellet porosity that facilitated the mass transfer of nutrients and metabolites from the pellets to the surrounding liquid. Furthermore, the ultrasonic treatment induced the expression of the laccase gene (lcc), which correlated with a sharp increase in both extracellular and intracellular laccase activity. This is the first study to find positive effects of ultrasound on gene expression in fungal cells. These results provide a basis for understanding the stimulation of metabolite production and process intensification by ultrasonic treatment in filamentous fungal culture.     

Optimization of hydrostatic pressure at varied sonication conditions – power density,intensity, very low frequency – for isothermal ultrasonic sludge treatment

This work aims at investigating for the first time the key sonication (US) parameters: power density (D_US), intensity (I_US), and frequency (F_S) – down to audible range, under varied hydrostatic pressure (P_h) and low temperature isothermal conditions (to avoid any thermal effect).The selected application was activated sludge disintegration, a major industrial US process. For a rational approach all comparisons were made at same specific energy input (ES, US energy per solid weight) which is also the relevant economic criterion.The decoupling of power density and intensity was obtained by either changing the sludge volume or most often by changing probe diameter, all other characteristics being unchanged. Comprehensive results were obtained by varying the hydrostatic pressure at given power density and intensity. In all cases marked maxima of sludge disintegration appeared at optimum pressures, which values increased at increasing power intensity and density. Such optimum was expected due to opposite effects of increasing hydrostatic pressure: higher cavitation threshold then smaller and fewer bubbles, but higher temperature and pressure at the end of collapse.In addition the first attempt to lower US frequency down to audible range was very successful: at any operation condition (D_US, I_US, P_h, sludge concentration and type) higher sludge disintegration was obtained at 12 kHz than at 20 kHz. The same values of optimum pressure were observed at 12 and 20 kHz.At same energy consumption the best conditions – obtained at 12 kHz, maximum power density 720 W/L and 3.25 bar – provided about 100% improvement with respect to usual conditions (1 bar, 20 kHz). Important energy savings and equipment size reduction may then be expected.     

Effect of ultrasound and high hydrostatic pressure (US/HHP) on the degradation of dextran catalyzed by dextranase

In our current research work, the effect of combination of ultrasonic irradiation and high hydrostatic pressure (US/HHP) on the enzymatic activity and enzymatic hydrolysis kinetic parameters of dextran catalytic by dextranase were investigated. Furthermore, the effects of US/HHP on the structure of dextranase were also discussed with the aid of fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The maximum hydrolysis of dextran was observed under US (40 W at 25 kHz for 15 min) combined with HHP (400 MPa for 25 min), in which the hydrolysis of dextran increased by 163.79% compared with the routine thermal incubation at 50 °C. Results also showed that, V_max and K_M values, as well as, k_cat of dextranase under US/HHP treatment were higher than that under US, HHP and thermal incubation at 50 °C, indicated that, the substrate is converted into the product at an increased rate when compared with the incubation at 50 °C. Compared to the enzymatic reaction under US, HHP, and routine thermal incubation, dextranase enzymatic reaction under US/HHP treatment showed decreases in Ea, ΔG and ΔH, however small increase in ΔS value was observed. In addition, fluorescence and CD spectra reflected that US/HHP treatment had increased the number of tryptophan on dextranase surface with increased α-helix by 19.80% and reduced random coil by 6.94% upon US/HHP-treated dextranase protein compared to the control, which were helpful for the improvement of its activity. These results indicated that, the combination of US and HHP treatments could be an effective method for improving the hydrolysis of dextran in many industrial applications including sugar manufacturing processes.     

Effects of phonophoresis with Arnica montana onto acute inflammatory process in rat skeletal muscles: An experimental study

This study aimed at verifying the effects of phonophoresis associated with Arnica montana on the acute phase of an inflammatory muscle lesion. Forty Wistar male rats (300 ± 50 g), of which the Tibialis Anterior muscle was surgically lesioned, were divided into four groups (n = 10 each): control group received no treatment; the ultrasound group (US) was treated in pulsed mode with 1-MHz frequency, 0.5 W/cm² intensity (spatial and temporal average – SATA), duty cycle of 1:2 (2 ms on, 4 ms off, 50%), time of application 3 min per session, one session per day, for 3 days; the phonophoresis or ultrasound plus arnica (US+A) group was treated with arnica with the same US parameters plus arnica gel; and the arnica group (A) was submitted to massage with arnica gel, also for 3 min, once a day, for 3 days. Treatment started 24 h after the surgical lesion. On the 4th day after lesion creation, animals were sacrificed and sections of the lesioned, inflamed muscle were removed for quantitative (mononuclear and polymorphonuclear cell count) and qualitative histological analysis. Collected data from the 4 groups were statistically analyzed and the significance level set at p < 0.05. Results show higher mononuclear cell density in all three treated groups with no significant difference between them, but values were significantly different (p < 0.0001) when compared to control group’s. As to polymorphonuclear cell density, significant differences were found between control group (p = 0.0134) and US, US+A and A groups; the arnica group presented lesser density of polymorphonuclear cells when compared (p = 0.0134) to the other groups. No significant difference was found between US and US+A groups. While the massage with arnica gel proved to be an effective anti-inflammatory on acute muscle lesion in topic use, these results point to ineffectiveness of Arnica montana phonophoresis, US having seemingly checked or minimized its anti-inflammatory effect.     

Synthesis of Mg-Al and Zn-Al-layered double hydroxide nanocrystals using laser ablation in water

In this paper, we report our results on the synthesis of Mg-Al and Zn-Al-layered double hydroxides using the laser ablation in the liquid technique. To prepare these layered double hydroxides (LDH) we first began with the laser generation of a Mg (or zinc) target submerged in deionized water and then ablated an aluminum target submerged in the previously prepared Mg-deionized water suspensions (Mg-dw) to produce Mg-Al LDH and in Zn-dw to prepare Zn-Al LDH. In these ablation tests, the Mg ablation duration was selected to vary from 5 to 60 min, while the Al ablation duration was kept constant at 30 min for all samples. The generated Mg-Al LDH was a gel-like and well crystallized nanoparticles of a rod-like shape and were arranged in a well-organized pattern. When the Mg ablation duration between 25 and 35 min, the synthesized nanocrystals were stoichiometric with a formula of Mg₆Al₂(OH)₁₈4.5(H₂O), the interlayer distance (d_(0 0 3)-spacing) was 7.8 Å and the average grain size was 8.0 nm. The synthesized Zn-Al LDH revealed various lamellar thin plate-like nanostructures of hexagonal morphologies. The average diameters of these structures was about 500 nm and the thickness of a single layer was approximately about 6.0 nm. The XRD diffraction peaks were indexed in hexagonal lattice with a_o=3.07 Å and c_o=15.12 Å. These indexes were (0 0 2), (0 0 4), and (0 0 8) and the corresponding interlayer distances, d-spacing (Å), were 7.56 (0 0 2), 3.782 (0 0 4), and 1.891 (0 0 8), respectively.     

Influence of rapid thermal annealing on electrical and structural properties of double metal structure Au/Ni/n-InP (1 1 1) diodes

The effect of rapid thermal annealing on the electrical and structural properties of Ni/Au Schottky contacts on n-InP have been investigated by current–voltage (I–V), capacitance–voltage (C–V), auger electron spectroscopy (AES) and X-ray diffraction (XRD) techniques. The Au/Ni/n-InP Schottky contacts are rapid thermally annealed in the temperature range of 200–500 °C for a duration of 1 min. The Schottky barrier height of as-deposited Ni/Au Schottky contact has been found to be 0.50 eV (I–V) and 0.86 eV (C–V), respectively. It has been found that the Schottky barrier height decreased with increasing annealing temperature as compared to as-deposited sample. The barrier height values obtained are 0.43 eV (I–V), 0.72 eV (C–V) for the samples annealed at 200 °C, 0.45 eV (I–V) and 0.73 eV (C–V) for those at 400 °C. Further increase in annealing temperature to 500 °C the barrier height slightly increased to 0.46 eV (I–V) and 0.78 eV (C–V) compared to the values obtained for the samples annealed at 200 °C and 400 °C. AES and XRD studies showed the formation of indium phases at the Ni/Au and InP interface and may be the reason for the increase in barrier height. The AFM results showed that there is no significant degradation in the surface morphology (rms roughness of 1.56 nm) of the contact even after annealing at 500 °C.     

Mechanism and dynamic study of reactive red X-3B dye degradation by ultrasonic-assisted ozone oxidation process

The effectiveness of ozone combined with ultrasound techniques in degrading reactive red X-3B is evaluated. A comparison among ozone (O₃), ultrasonic (US), ozone/ultrasonic (O₃/US) for degradation of reactive red X-3B has been performed. Results show that O₃/US system was the most effective and the optimally synergetic factor reaches to 1.42 in O₃/US system. The cavitation of ultrasound plays an important role during the degradation process. It is found that 99.2% of dye is degraded within 6 min of reaction at the initial concentration of 100 mg·L⁻¹, pH of 6.52, ozone flux of 40 L·h⁻¹ and ultrasonic intensity of 200 W·L⁻¹. Ozonation reactions in conjunction with sonolysis indicate that the decomposition followed pseudo-first-order reaction kinetics but the degradation efficiencies are affected by operating conditions, particularly initial pH and ultrasonic intensity. A kinetic model is established based on the reaction corresponding to operational parameters. In addition, the main reaction intermediates, such as p-benzoquinone, catechol, hydroquinone, phthalic anhydride and phthalic acid, are separated and identified using GC/MS and a possible degradation pathway is proposed during the O₃/US process.     

Structural and permeability sensitivity of cells to low intensity ultrasound: Infrared and fluorescence evidence in vitro

This work is focused on the in vitro study of the effects induced by medical ultrasound (US) in murine fibroblast cells (NIH-3T3) at a low-intensity of exposure (spatial peak temporal average intensity I_ta < 0.1 W cm⁻²). Conventional 1 MHz and 3 MHz US devices of therapeutic relevance were employed with varying intensity and exposure time parameters. In this framework, upon cells exposure to US, structural changes at the molecular level were evaluated by infrared spectroscopy; alterations in plasma membrane permeability were monitored in terms of uptake efficiency of small cell-impermeable model drug molecules, as measured by fluorescence microscopy and flow cytometry. The results were related to the cell viability and combined with the statistical PCA analysis, confirming that NIH-3T3 cells are sensitive to therapeutic US, mainly at 1 MHz, with time-dependent increases in both efficiency of uptake, recovery of wild-type membrane permeability, and the size of molecules entering 3T3. On the contrary, the exposures from US equipment at 3 MHz show uptakes comparable with untreated samples.     

Ultrasound-assisted adsorption of 4-dodecylbenzene sulfonate from aqueous solutions by corn cob activated carbon

This study was aimed at removal of 4-dodecylbenzene sulfonate (DBS) ions from aqueous solutions by ultrasound-assisted adsorption onto the carbonized corn cob (AC). The main attention was focused on modeling the equilibrium and kinetics of adsorption of DBS onto the AC. The AC was prepared from ground dried corn cob by carbonization and activation by carbon dioxide at 880 °C for 2 h in a rotary furnace. The adsorption isotherm data were fitted by the Langmuir model in both the absence and the presence of ultrasound (US). The maximum adsorption capacities of the adsorbent for DBS, calculated from the Langmuir isotherms, were 29.41 mg/g and 27.78 mg/g in the presence of US and its absence, respectively. The adsorption process in the absence and the presence of US obeyed the pseudo second-order kinetics. The intraparticular diffusion model indicated that the adsorption of DBS ions on the AC was diffusion controlled as well as that US promoted intraparticular diffusion. The ΔG° values, ?24.03 kJ/mol, ?25.78 kJ/mol and ?27.78 kJ/mol, were negative at all operating temperatures, verifying that the adsorption of DBS ions was spontaneous and thermodynamically favorable. The positive value of ΔS° = 187 J/mol K indicated the increased randomness at the adsorbent–adsorbate interface during the adsorption of DBS ions by the AC.     

Quick response PZT/P(VDF-TrFE) composite film pyroelectric infrared sensor with patterned polyimide thermal isolation layer

The fabrication method and the pyroelectric response of a single element infrared sensor based lead zirconate titanate (PZT) particles and polyvinylidene fluoride P(VDF-TrFE) copolymer composite thick film is reported in this paper. A special thermal insulation structure, including polyimide (PI) thermal insulation layer and thermal insulation tanks, was used in this device. The thermal insulation tanks were fabricated by laser micro-etching technique. Voltage responsivity (R_V), noise voltage (V_noise), noise equivalent power (NEP), and detectivity (D^*) of the PZT/P(VDF-TrFE) based infrared sensor are 1.2 × 10³ V/W, 1.25 × 10⁻⁶ V Hz^1/2, 1.1 × 10⁻⁹ W and 1.9 × 10⁸ cm Hz^1/2 W⁻¹ at 137.3 Hz modulation frequency, respectively. The thermal time constant of the infrared sensor τ_T was about 15 ms. The results demonstrate that the composite infrared sensor show a high detectivity at high chopper frequency, which is an essential advantage in infrared detectors and some other devices.     

Ultrasonic and DFT study of intermolecular association through hydrogen bonding in aqueous solutions of d(−)-arabinose

The experimental measurements of density, viscosity and ultrasonic velocity of aqueous d-arabinose solutions were carried out as functions of concentration (0.1 ≤ m [mol kg^? 1] ≤ 1.0) and temperature (303.15 ≤ T [K] ≤ 323.15). The isentropic compressibility (β_s), acoustic impedance (Z), hydration number (H_n), intermolecular free length (L_f), classical sound absorption (α/f²)_class and shear relaxation time (τ) were calculated by using the measured data. These parameters have been interpreted in terms of solute–solvent interactions. The quantum chemical calculations were performed to study the hydrogen bonding in interacting complex formed between α-D-arabinopyranose in ¹C₄ conformation and water molecules. Computations have been done by using Density Functional Theory (DFT) method at B3LYP/6-31+g(d) level of theory to study the equilibrium structure of α-d-arabinose, α-D-arabinopyranose–water interacting complex and vibrational frequencies. The solution phase study was carried out using Onsager's reaction field model in water solvent. The computed and scaled vibrational frequencies are in good agreement with the main features of the experimental spectrum when seven water molecules are considered explicitly with α-D-arabinopyranose in ¹C₄ conformation. The interaction energy (E_total), hydrogen bond lengths and dipole moment (μ_m) of the interacting complex are also presented and discussed with in the light of solute–solvent interactions.     

Microfabrication of solenoid-type RF SMD chip inductors with an Al2O3 core

We investigated micron size, high-performance, and solenoid-type radio-frequency surface-mounted device (SMD) chip inductors with a low-loss Al₂O₃ core for a GHz drive microwave circuit application. Copper coils with a diameter of 27 μm were used and the chip inductors fabricated in this study are 0.86 × 0.46 × 0.45 mm³. The high-frequency characteristics of the inductance (L), quality factor (Q), and impedance (Z) of the developed inductors were measured using a RF impedance/material analyzer (HP4291B with HP16193A test fixture). The developed inductors have a self-resonant frequency of 3.7–5.2 GHz and exhibit L of 15–34 nH. The inductors have Q of 38–49 over the frequency ranges of 900 MHz–1.7 GHz. The calculated data obtained from the equivalent circuit and the derived equation of Q described the high-frequency data of L, Q, and Z of the inductors developed quite well.     

Synergism between ultrasonic pretreatment and white rot fungal enzymes on biodegradation of wheat chaff

Lignocellulosic biomass samples (wheat chaff) were pretreated by ultrasound (US) (40 kHz/0.5 W cm⁻²/10 min and 400 kHz/0.5 W cm⁻²/10 min applied sequentially) prior to digestion by enzyme extracts obtained from fermentation of the biomass with white rot fungi (Phanerochaete chrysosporium or Trametes sp.). The accessibility of the cellulosic components in wheat chaff was increased, as demonstrated by the increased concentration of sugars produced by exposure to the ultrasound treatment prior to enzyme addition. Pretreatment with ultrasound increased the concentration of lignin degradation products (guaiacol and syringol) obtained from wheat chaff after enzyme addition. In vitro digestibility of wheat chaff was also enhanced by the ultrasonics pretreatment in combination with treatment with enzyme extracts. Degradation was enhanced with the use of a mixture of the enzyme extracts compared to that for a single enzyme extract.     

Combined of ultrasound irradiation with high hydrostatic pressure (US/HHP) as a new method to improve immobilization of dextranase onto alginate gel

In this research work, dextranase was immobilized onto calcium alginate beads by the combination of ultrasonic irradiation and high hydrostatic pressure (US/HHP) treatments. Effects of US/HHP treatments on loading efficiency and immobilization yield of dextranase enzyme onto calcium alginate beads were investigated. Furthermore, the activities of immobilized enzymes prepared with and without US/HHP treatments and that prepared with ultrasonic irradiation (US) and high hydrostatic pressure (HHP), as a function of pH, temperature, recyclability and enzyme kinetic parameters, were compared with that for free enzyme. The maximum loading efficiency and the immobilization yield were observed when the immobilized dextranase was prepared with US (40 W at 25 kHz for 15 min) combined with HHP (400 MPa for 15 min), under which the loading efficiency and the immobilization yield increased by 88.92% and 80.86%, respectively, compared to immobilized enzymes prepared without US/HHP treatment. On the other hand, immobilized enzyme prepared with US/HHP treatment showed V_max, K_M, catalytic and specificity constants values higher than that for the immobilized enzyme prepared with HHP treatment, indicated that, this new US/HHP method improved the catalytic kinetics activity of immobilized dextranase at all the reaction conditions studied. Compared to immobilized enzyme prepared either with US or HHP, the immobilized enzymes prepared with US/HHP method exhibited a higher: pH optimum, optimal reaction temperature, thermal stability and recyclability, and lower activation energy, which, illustrating the effectiveness of the US/HHP method. These results indicated that, the combination of US and HHP treatments could be an effective method for improving the immobilization of enzymes in polymers.     

Conductive diamond sono-electrochemical disinfection (CDSED) for municipal wastewater reclamation

In the present work, the disinfection of actual effluents from a municipal wastewater treatment plant (WWTP) by a conductive diamond sono-electrochemical process was assessed. First, efficiency of single electrodisinfection process with diamond anodes (without the contribution of ultrasounds) was studied, finding that the total disinfection can be attained at current charges applied below 0.02 kA h m⁻³. It was also found that the main disinfection mechanism is the attack of Escherichia coli (E. coli) by the disinfectants produced in the electrochemical cell and that the production of chlorates is avoided when working at current densities not higher than 1.27 A m⁻². Next, a marked synergistic effect was found when coupling ultrasound (US) irradiation to the electrochemical system (sono-electrochemical disinfection). This increase in the disinfection rate was found to be related to the suppression of the agglomeration of E. coli cells and the enhancement in the production of disinfectant species.     

Synthesis of TiO2 nanoparticles and spectroscopic upconversion luminescence of Nd3+-doped TiO2–SiO2 composite glass

Nd³⁺-doped TiO₂–SiO₂ composites were prepared by sol–gel method. Optical properties such as radiative life-time (τ), stimulated emission cross-section (σ_p) and branching ratio (β) were calculated using Judd–Ofelt theory. Violet to blue upconversion emissions at 380 nm (⁴D_3/2→⁴I_11/2), 399 nm (²P_3/2→⁴I_11/2), 420 nm (²D_5/2→⁴I_9/2) and 452 nm (²P_3/2→⁴I_13/2) were obtained under 578 nm xenon-lamp excitation. The choice of 578 nm is justified by the absorption spectra of the same samples, which shows a strong absorption peak at 578 nm. This 578 nm excitation pump produces upconversion in Nd³⁺ by a sequential two-photon absorption process.     

Effect of doping on cohesive and thermophysical properties of MgB2

The effects of doping Al and Mn on the cohesive and thermophysical properties of MgB₂ have been investigated using a Rigid Ion Model (RIM). The interatomic potential of this model includes contributions from the long-range Coulomb attraction and the short-range overlap repulsion and the van der Waals attraction. This model has been applied to describe the temperature dependence of the specific heat of MgB₂, Mg_1−xAl_xB₂ (x = 0.1–0.9) and Mg_1−xMn_xB₂ (x = 0.01–0.04) in the temperature range 5 K ⩽ T ⩽ 1000 K. The calculated results on cohesive energy (ϕ), Bulk modulus (B_T), molecular force constant (f), Restrahalen frequency (ν₀), Debye temperature (Θ_D) and Gruneisen parameter (γ) are also reported for these materials. Our results on Bulk modulus, Restrahalen frequency and Debye temperature are closer to the available experimental data. The comparison between our calculated and available experimental results on the specific heat at constant volume for MgB₂ and Mg_1−xAl_xB₂ (x = 0.1–0.4), particularly, at lower temperatures has shown almost an excellent agreement. The trend of variation of the specific heat with temperature is more or less similar in pure and doped MgB₂.     

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.