Sequential flow analysis coupled with ACSV for on-line monitoring of cobalt in the marine environment

The development of a compact instrument for on-line measurement of trace metals in seawater is described. The system is based on adsorptive cathodic stripping voltammetry (ACSV), and on the concept of sequential flow analysis, to perform on-line measurements with controlled perturbation of natural equilibria of the element. The design combines a low volume flow cell with a miniature solenoid pump and valves to achieve low power consumption. The flow segmentation is time-controlled and the detection step takes place in a well-defined part of the flow stream where reagent and sample occur mixed. The system was tested on the determination of cobalt in seawater but it is likely that the same technique can be used to determine other metals detectable by CSV. The determination range was 6–1050 pmol/L cobalt with a detection limit (3σ) of 6 pmol/L. The measurement rate was about 60 h^–1. Comparative measurements were carried out using continuous flow analysis. The apparatus was used continuously on board a ship to determine the distribution pattern of cobalt in surface waters off the coast of California.     

Analytic mappings between two ultrahyperelliptic surfaces

Aequationes mathematicae -     

A 5/4 algorithm for two-dimensional packing

This paper proposes a new algorithm for a two-dimensional packing problem first studied by Baker, Coffman, and Rivest (SIAM J. Comput. 9, No. 4(1980), 846–855). In their model, a finite list of rectangles is to be packed into a rectangular bin of finite width but infinite height. The model has applications to certain scheduling and stock-cutting problems. Since the problem of finding an optimal packing is NP-hard, previous work has been directed at finding polynomial approximation algorithms for the problem, i.e., algorithms which come within a constant times the height used by an optimal packing. For the algorithm proposed in this paper, the ratio of the height obtained by the algorithm and the height used by an optimal packing is asymptotically bounded by 5/4. This bound is an improvement over the bound of 4/3 achieved by the best previous algorithm.     

A cheap versatile ultraviolet photoelectron spectrometer

The design, construction and operation of an ultraviolet photoelectron spectrometer are reported. It has a readily accessible target chamber and a versatile inlet system, which can cope with a rapid throughput of relatively involatile samples. The electrons emerging from the target chamber pass through two slits which are subject to a variable electric field, into a magnetic field. Thus the spectrum is linear. The resolution based on argon ²P_{$\text{3}\text{2}$} peak is 18 meV. The instrument is easy to make and operate. It is proving adequate for many chemical and analytical purposes and may be coupled directly to a gas-liquid chromatograph. Problems encountered during construction and optimization are discussed.     

Soldier defense secretions of the south american termites Cortaritermes Silvestri, Nasutitermes SP N.D and Nasutitermes Kemneri

The defense secretions of the soldiers of the South American termites Cortaritermes silvestri, Nasutitermes sp. n.D. and Nasutitermes kemneri have been investigated. The secretion of C. silvestri was shown to contain α-pinene, β-pinene, limonene and cis-pin-3-en-yl acetate. Three of the four diterpenes in this secretion were identified as the triacetate, diacetate propionate and acetate dipropionate of 3α, 9β, 12α-trihydroxy-11(12), 15(17-trinervitadiene. The soldier secreation of Nasutitermes sp. n.D. and Nasutitermes kemneri were found to contain a mixture of monoterpene hydrocarbons and diterpenes. The major monoterpene in these two species was shown to be β-phellandrene and terpinolene, respectively. The major diterpene in Nasutitermes sp. n.D. was identified as 9β-hydroxy-1(15), 8(19)-trinervitadiene and, for Nasutitermes kemneri, 2α, 3β-dihydroxy-1(15), 8(9)- and 1(15), 8(19)-trinervitadiene were the major components.     

207Pb(p,p') measurements at 135 and 61 MeV,the effective interaction and core polarization

Data at Einp = 61 and 135 MeV for neutron-hole transitions are used to study the proton-neutron part of the assumed NN force. Collective core-polarization strengths (A_L) from the present fits at 135 MeV are consistent with those extracted from the (e, e') reaction for two L = 2 transitions and one L = 4 transition. This is not the case at 61 MeV where the A_L values needed to fit the (p, p') data are much smaller for transitions to the $\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{and}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ hole states. A fully microscopic DWBA fit is successful for the L = 3 transition to the doublet at 2.64 MeV of excitation at E_p = 61 MeV, but fails at 135 MeV; a fully microscopic DWIA calculation provides a reasonable fit to the data at 135 MeV.     

Preparation of beryllium hydride by an improved pyrolysis technique

Beryllium hydride has been produced in purities of 90–98 wt% by the controlled pyrolysis of di-t-butylberyllium etherate in hot oil. It was obtained as an amorphous solid, remarkably stable at elevated temperatures and resistant to attack by water and common organic solvents. The source of residual impurities was shown by deuterium labeling to be derived largely from incomplete pyrolysis and ether cleavage. A series of alkylberyllium homologs was subjected to the pyrolysis reaction; of these t-Bu₂Be · Et₂O gave the highest purity BeH₂.