The application of semiconductor diode lasers to the soldering of electronic components

Work being carried out at the University of Hull into the application of high power laser diodes to the soldering process is described. The commercial availability of semiconductor diode lasers has brought an exciting new soldering tool to the manufacturers of electronics assemblies: trends in electronics assembly are to increasingly high-density interconnections and increasing device functionality. Packages are reducing in size and pin-out counts are increasing. Currently 0.010–0.016 inch lead pitch devices are being introduced by many manufacturers. Lasers can be used with advantage in the soldering of such fine and precise devices and high-power semiconductor laser diodes can be used to build compact, flexible and controllable soldering units. With computer control of the power and duration of the laser energy it is possible to ensure consistent and reliable soldering. To achieve this, however, the various parameters involved in the laser beam-solder assembly interaction need to be carefully defined. This paper reports on our identification of these parameters and the salient design features of an automated diode laser soldering system.     

Multiresidue analysis of pesticides in fresh fruits and vegetables using procedures developed by the Florida Department of Agriculture and Consumer Services

Improved quality and efficiency of pesticide residue analysis were achieved by examining all aspects of the laboratory process. In an effort to eliminate methylene chloride hazardous waste, an acetonitrile extraction method, originally developed by the California Department of Agriculture, was modified and adopted. Sample size and solvent consumption were reduced with the new method. Custom glassware racks and disposable supplies reduced overall analysis time. Gravity-fed, solid-phase extraction simplified sample preparation and provided cleaner extracts for gas chromatographic analyses. Modifications to the method were made to achieve the ruggedness needed to maintain quality objectives during routine analysis. Instrumental improvements, including new selective detectors, retention time locking, and mass spectrometry screening for all samples, provided the laboratory with efficient, reliable, and confirmed analytical results.     

Crystal structure of tris(triphenylsiloxy)borane·triphenylsilanol (1:1) adduct

The title compound crystallizes in the triclinic space group , with a = 14.458(6), b = 14.630(5), c = 14.721(8) Å, = 79.75(2), = 80.11(3), = 80.50(3)°, and Z = 2. The crystal structure consists of molecules of (Ph₃SiO)₃B and Ph₃SiOH linked by an weak B···(silanol) acceptor-donor bond, additionally stabilized by OH(silanol)···O(siloxy) hydrogen bonds. The average B–O, Si–O distances and B–O–Si angle are 1.369, 1.649 Å and 137.2°, respectively.     

Sonoelectrochemically enhanced determination of 5-aminosalicylic acid

The electrochemical detection of the anti-inflammatory drug 5-aminosalicylic acid (5-ASA) has been evaluated through the application of linear sweep, square wave and sonolinear sweep voltammetry. The introduction of ultrasound is shown to significantly enhance the oxidation signal intensity thereby enabling the detection of low concentrations with the linear range (1-57 muM) adequate for assessing free drug within physiological samples. Interference from ascorbic acid can be effectively negated through the introduction of cupric ion without any appreciable cost to the voltammetric response to 5-ASA. The efficacy of employing sonolinear sweep voltammetry to the determination of this compound within a compositionally complex tissue culture medium has been assessed with the recovery of 5 muM 5-ASA found to be 102% (RSD=5%, N=3).     

Synthesis and properties of aralkylamine C-nitroso dimers

The action of 3-chloroperbenzoic acid on eleven aralkylamines yielded the C-nitroso dimers; physical properties of the compounds, including UV, IR, NMR and MS data are reported. The stability of the nitroso dimers was investigated. The 2-nitroso-1-phenylpropane dimer was converted into its hydrazo-, azo- and azoxy-derivatives.     

The investigation of thyroid function.

The measurement of thyrotropin (TSH) by a third-generation assay (functional sensitivity 0.01-0.02 mU/L) offers the single best test of assessing thyroid status and is more cost effective than measurement of thyroxine (T4) as a first-line test. However, in certain situations, e.g., nonthyroidal illness (NTI), secondary thyroid disease, early treatment of hyperthyroidism, early pregnancy, and heterophilic antibody interference, TSH alone may be misleading, and thyroid hormone measurements are also required. The author's laboratory has found that the measurement of TSH together with free thyroxine (by a nonanalogue method) offers the most speedy and effective first-line strategy for thyroid function testing. Abnormalities in thyroid function tests in euthyroid patients are most likely found in NTI and the elderly. For this reason, thyroid function tests (TFTs) should not be requested in elderly or hospitalized patients unless the presenting complaint is considered to be because of a thyroid problem.     

Energy spectra for decaying 2D turbulence in a bounded domain

We use results derived in the framework of the replica approach to study the liquid-glass thermodynamic transition. The main results are derived without using replicas and applied to the study of the Lennard-Jones binary mixture introduced by Kob and Andersen. We find that there is a phase transition due to the entropy crisis. We compute both analytically and numerically the value of the phase transition point T(K) and the specific heat in the low temperature phase.