An investigation of metal/GaAs(100) interfaces by deep level transient spectroscopy

In this work we investigate the ability of DLTS to detect the presence of interface states at metal/GaAs(100) (n-type) interfaces where the semiconductor surface has been prepared by two different procedures. A correlation is observed between the magnitude of the ideality parameter determined from the current-voltage (I-V) characteristic of the diode and presence in the DLTS spectrum of a feature attributable to interface states. Schottky diodes have been fabricated with both gold and iron contacts which exhibit near ideal behaviour (n<1.1). No interface states were detected by DLTS on either of these diodes. However, diodes fabricated on oxidised GaAs surfaces, with higher idealities (1.5 <n < 2), exhibit additional electron trap levels in the DLTS spectrum. For the case of iron, a deep level of activation energy 0.55 eV is observed in the conventional reverse bias pulse sequence mode of DLTS operation. In addition, for both gold and iron diodes, a spectral feature which can be attributed to a broad distribution of interface states within the deplation region is observed during a forward bias pulse sequence.     

Community Health Care in Rochdale Family Health Services Authority

The National Health Service and the Social Services are engaged on a massive transfer of resources in which, wherever possible, care will be delivered to vulnerable patients in their own homes. This paper deals with two pilot medical practices in Rochdale. The needs of patients are considered on a subjective scale in five categories. It was confirmed that there was a consistency of subjective measurement between the nurses involved but there was no relation between these particular measures and the amount of nursing care being delivered. However, there was a strong relationship between age and the probability of being on the nursing care list, with a significant difference between the sexes. The model can lead to the identification of categories of patients who might have slipped through the net and also to estimates of the total home care nursing list in a practice.     

The thermal decomposition of peroxyacetic nitric anhydride (PAN) and peroxymethacrylic nitric anhydride (MPAN)

The rate coefficients of thermal decomposition of peroxyacetic nitric anhydride (PAN) and peroxymethacrylic nitric anhydride (MPAN) were measured over the temperature range 302–323 K. The resulting Arrhenius expressions were k = 10^17.4±0.4 exp(?28.5 ± 0.5/RT) for PAN, and k = 10^16.2±0.7 exp(?26.8 ± 1.0/RT) for MPAN, where the activation energy is in Kcal/mol. These results are in good agreement with previous studies of PAN and other PAN-type compounds, and imply that energies of RC(O)OO? NO₂ bonds are relatively independent of the nature of R.     

Counting the microstates of a Kerr black hole in M theory

We show that an extremal Kerr black hole, appropriately lifted to M theory, can be transformed to a Kaluza-Klein black hole in M theory, or a D0-D6 charged black hole in string theory. Since all the microstates of the latter have recently been identified, one can exactly reproduce the entropy of an extremal Kerr black hole. We also show that the topology of the event horizon is not well defined in M theory.     

Ultrasound pasteurization: the effects of temperature, soluble solids, organic acids and pH on the inactivation of Escherichia coli ATCC 25922

The objectives of this research were to study the effects of temperature, sugar concentration (8, 12, and 16 g/100ml), organic acids (citric and malic acids) and pH (2.5 and 4.0) on ultrasound pasteurization. The model organism used for the research was Escherichia coli ATCC 25922, and ultrasound treatment times were conducted to achieve a 5 log (base 10) reduction. Ultrasound generates heat, therefore the study involved removing the heat using a jacketed beaker with refrigerant (-30 degrees C) to maintain processing temperature at or below 30 degrees C and eliminate the thermal inactivation effects. Overall, ultrasound increased the sensitivity of E. coli to thermal inactivation. The presence of soluble solids had a protective effect where the sonication time requirement increased. Similar to heat sensitivity, the lower pH environment resulted in E. coli having less resistance to sonication. The type of organic acid had the least significant effect on ultrasound inactivation of E. coli.     

Scalable subspace methods for derivative-free nonlinear least-squares optimization

Mathematical Programming - We introduce a general framework for large-scale model-based derivative-free optimization based on iterative minimization within random subspaces. We present a...     

A study of pulsating flow in automotive catalyst systems

Conversion efficiency, durability and pressure drop of automotive exhaust catalysts are dependent on the flow distribution within the substrate. This study examines the effect of pulsating flow on the flow distribution within these systems. The flow distribution was measured for a range of flow rates at pulsation frequencies of 16, 32, 64 and 100 Hz. It was shown that the flow uniformity at 16 Hz was similar to the steady equivalent whereas improved uniformity was seen at the higher frequencies resulting in a reduced pressure drop. It was further found that flow maldistribution under pulsating conditions was less sensitive to increases in flow rate compared to steady-state flow. Downstream of the monolith strong pulses were observed although the pulse shapes changed across the substrate diameter. Flow maldistribution correlated well with a non-dimensional parameter derived from the inlet flow velocity, pulsation frequency and diffuser length.     

Ammonia Activation by a Nickel NCN‐Pincer Complex featuring a Non‐Innocent N‐Heterocyclic Carbene: Ammine and Amido Complexes in Equilibrium

A Ni⁰‐NCN pincer complex featuring a six‐membered N‐heterocyclic carbene (NHC) central platform and amidine pendant arms was synthesized by deprotonation of its Ni^II precursor. It retained chloride in the square‐planar coordination sphere of nickel and was expected to be highly susceptible to oxidative addition reactions. The Ni⁰ complex rapidly activated ammonia at room temperature, in a ligand‐assisted process where the carbene carbon atom played the unprecedented role of proton acceptor. For the first time, the coordinated (ammine) and activated (amido) species were observed together in solution, in a solvent‐dependent equilibrium. A structural analysis of the Ni complexes provided insight into the highly unusual, non‐innocent behavior of the NHC ligand.     

Synthesis of an [(NHC)2Pd(SiMe3)2] Complex and Catalytic cis‐Bis(silyl)ations of Alkynes with Unactivated Disilanes

The novel complex cis‐[(ITMe)₂Pd(SiMe₃)₂ (ITMe=1,3,4,5‐tetramethylimidazol‐2‐ylidene) has been synthesized by mild oxidative cleavage of Me₃SiSiMe₃ using [(ITMe)₂Pd⁰]. The use of this complex as precatalyst for the cis‐bis(silyl)ation of alkynes using unactivated disilanes is reported.     

Ultraviolet Absorption Induces Hydrogen‐Atom Transfer in G⋅C Watson–Crick DNA Base Pairs in Solution

Ultrafast deactivation pathways bestow photostability on nucleobases and hence preserve the structural integrity of DNA following absorption of ultraviolet (UV) radiation. One controversial recovery mechanism proposed to account for this photostability involves electron‐driven proton transfer (EDPT) in Watson–Crick base pairs. The first direct observation is reported of the EDPT process after UV excitation of individual guanine–cytosine (G?C) Watson–Crick base pairs by ultrafast time‐resolved UV/visible and mid‐infrared spectroscopy. The formation of an intermediate biradical species (G[?H]?C[+H]) with a lifetime of 2.9 ps was tracked. The majority of these biradicals return to the original G?C Watson–Crick pairs, but up to 10 % of the initially excited molecules instead form a stable photoproduct G*?C* that has undergone double hydrogen‐atom transfer. The observation of these sequential EDPT mechanisms across intermolecular hydrogen bonds confirms an important and long debated pathway for the deactivation of photoexcited base pairs, with possible implications for the UV photochemistry of DNA.