Short communication: Thermal stability of the diazohydroborate [1‐N2B10H9]−: degradation to [B20H18]2− anion

The thermal stability of the monodiazohydroborate NMe₄[1‐N₂B₁₀H₉] was studied by thermogravimetric analysis. Under two different atmospheres (air and argon), the thermal decomposition starts at a temperature between 140 and 160 °C. The decomposition residue obtained was separated on a silica gel column. ¹¹B NMR, IR and electrospray mass spectroscopy analyses of the different fractions separated showed that the above decomposition produces (NMe₄)₂[B₂₀H₁₈] as major product (90%), along with smaller amounts of residual NMe₄[1‐N₂B₁₀H₉] (5%), (NMe₄)₂[B₁₂H₁₂] and boric acid. Copyright © 2003 John Wiley & Sons, Ltd.     

Generalization of Supersymmetric Quantum Mechanics

A generalization of supersymmetric quantummechanics can be obtained in two different ways usingthe theory of the q-deformation of the oscillatoralgebra, according to whether q is a root of unity ornot. In the first case the fractional supersymmetricquantum mechanic is between bosons and q-bosons. In thesecond case we obtain the deformed supersymmetricquantum mechanics by considering bosons and a deformed truncated oscillator algebra.     

Crystal structure of monomethylammonium tribromocadmate(II)

CH₃NH₃CdBr₃ crystallizes in the space group Ccm2₁, a = 13.693(1) Å, b = 7.906(1) Å, c = 6.886(1) Å, V = 745.46(15) ų, Z = 4, D _x = 3.42 Mg m^–3. The structure of the title compound is one-dimensional consisting of infinite chains made of face sharing CdBr₆ octahedra. The methylammonium groups are situated in the space between chains. The cations and anions are joined by hydrogen bonding.     

Effects of electromagnetic near-field stress on SiGe HBT’s reliability

In this paper, a reliability damage mechanism was presented in SiGe Heterojunction Bipolar Transistor (HBT). This new stress methodology differs from conventional SiGe, HBT device reliability associated with other stresses, since it was obtained by applying electromagnetic near-field aggression. The near-field set-up is used to disturb with electromagnetic field the Device Under test (DUT) on a localized area. Degradations in the base current and the current gain are identified. They are induced by a large base current leakage due to hot carrier which introduces generation/recombination trap centers at the silicon–oxide interface of the emitter–base spacer. By using the S-parameters measurements, we find that both forward transmission scattering parameter (S₂₁) and the input scattering parameter (S₁₁) are affected by this stress. In addition the power characteristics of DUT are also affected by stress. A Direct Power Injection (DPI) method is used to understand the near-field stress behaviour.     

Constructs of engagement emerging in an ethnomathematically-based teacher education course

This paper presents a case study, in which we apply and develop theoretical constructs to analyze motivating desires observed in an unconventional, culturally contextualized teacher education course. Participants, Israeli students from several different cultures and backgrounds (pre-service and in-service teachers, Arabs and Jews, religious and secular) together studied geometry through inquiry into geometric ornaments drawn from diverse cultures, and acquired knowledge and skills in multicultural education. To analyze affective behaviors in the course we applied the methodology of engagement structures recently proposed by Goldin and his colleagues. Our study showed that engagement structures were a powerful tool for examining motivating desires of the students. We found that the constructivist ethnomathematical approach highlighted the structures that matched our instructional goals and diminished those related to students’ feelings of dissatisfaction and inequity. We propose a new engagement structure “Acknowledge my culture” to embody motivating desires, arising from multicultural interactions, that foster mathematical learning.     

Efficient recursive least squares parameter estimation algorithm for accurate nanoCMOS variable gain amplifier performances

ABSTRACT

With the aggressive scaling of integrated circuit technology, parametric estimation is a critical task for designers who looked for solutions to the challenges of some Nanoscale CMOS parameters. This paper presented the prediction of primary parameters of CMOS transistor for 16 nm to 10 nm process nodes using both of Bisquare Weights (BW) method and a novel recursive least squares (RLS) parameter estimation algorithm. The proposed RLS algorithm consists of the minimisation of a quadratic criterion relating to the prediction error in order to attain the best estimated parameters of the developed mathematical model. The obtained results thanks to the proposed RLS algorithm were better than those reached using the BW method. Comparisons between Predictive Technology Model (PTM) data and parameters estimated with RLS algorithm were made to check the validity and the consistency of the proposed algorithm. These predicted primary parameters were helpful to estimate and to optimise the performances of the Variable Gain Amplifier (VGA) which was a basic circuit element with a key role in the design of new upcoming receivers.     

Crystal structure of pentakis ethylenediammonium bis undecachlorodiantimonate(III) tetrahydrate, (NH3(CH2)2NH3)5(Sb2Cl11)2·4H2O

The pentakis ethylenediammonium bis undecachlorodiantimonate(III) tetrahydrate salt is monoclinic with the following unit cell dimensions:a=16.271(5) Å,b=13.004(4) Å,c=13.932(4) Å, β=111.72(2)°, space groupP2₁/c withZ=2. The structure was solved by Patterson methods and refined to a finalR value of 0.023 for 4435 reflections withF ₀>4σ(F ₀). The structure shows a layer arrangement perpendicular to thea axis: planes of the [Sb₂Cl₁₁]⁵⁻ bioctahedra alternate with planes of [NH₃(CH₂)₂NH₃]²⁺ dications. The [Sb₂Cl₁₁]⁵⁻ bioctahedra are connected through O−H...Cl hydrogen bonds, such that infinite chains of composition [Sb₂Cl₁₁(H₂O]_n ⁵ⁿ⁻ are formed in the structure, parallel to the twofold axis. These chains are themselves interconnected by means of N−H...Cl and O−H...Cl bonds originating from the [NH₃(CH₂)₂NH₃]²⁺ entities and the water molecules, respectively, and form a threedimensional network.