Light Modulates Electric Phenomena in Hornet Cuticle¶

In the cuticle of live social hornets, such as Vespa orientalis (Hymenoptera, Vespinae), endogenous electric effects are encountered, i.e. voltages of 100–200 mV under illumination and currents amounting to several microamperes on its subjection to darkness—clearly a process of charging and discharging. Of the various wavelengths of sunlight, UV was found to be the most contributory to the active cuticular voltage generation. Throughout the warm season of the yearthe–the active period in colonies of social hornets and wasps—colony members exit from the dark nest during the daytime and fly to the field under the hot sun for various foraging purposes, ultimately returning to the nest. Thus, each hornet, be it queen, worker or drone, probably undergoes daily cyclical process of electric charge and discharge in the exterior part of their integument, cuticle, which lasts up to 30–40 min. Such photoelectric phenomenon was detected in both live, ether‐anaesthetized hornets and dead hornets, albeit in the latter the electric values recorded were lower. The present study addresses the possible impact of the phenomenon on vespan daily life and also compares it with a parallel occurrence in electric fish.     

Thermal characterization of social vespid silk

In this paper we try to establish a link between the microclimate in the wasp nest and the structure and thermal stability of vespid silk. We suggest that there are at least two types of water that is absorbed by the silk of Oriental hornets, namely, surface water and intrinsic structural water. The release of both types of water was found to be reversible. The enthalpy values of the endothermic peaks associated with the release of water from different silk samples do not differ substantially and are in the range of 106 to 130 J g^-1 for the Vespa orientalis male larvae silk (sample #1), Paravespula germanica (yellowjacket) worker larvae silk (#3) and Vespa orientalis nest envelope(#4). For the Vespa orientalis worker larvae silk (sample #2), however, it is twice as large (228 J g^-1). This is in agreement with the increased total amount of absorbed water. The silk studied has a fibrilar structure with interconnecting surfaces overlying entire regions. It is assumed that the initial water loss stems from water evaporation from the coat of the fibers - a daily occurrence in the hornets' nest. Heating to above 70°C may result in structural changes in the silk core. This revised version was published online in July 2006 with corrections to the Cover Date.     

Generating uniform random vectors over a simplex with implications to the volume of a certain polytope and to multivariate extremes

A uniform random vector over a simplex is generated. An explicit expression for the first moment of its largest spacing is derived. The result is used in a proposed diagnostic tool which examines the validity of random number generators. It is then shown that the first moment of the largest uniform spacing is related to the dependence measure of random vectors following any extreme value distribution. The main result is proved by a geometric proof as well as by a probabilistic one.     

Calix[4]arene derivatives monosubstituted at all four methylene bridges

The scope of the reaction of the tetrabromocalixarene derivative 2b with alcohols under solvolytic conditions in trifluoroethanol (TFE) or hexafluoroisopropanol (HFIP) was explored. The reaction proceeded readily with MeOH, EtOH, n-PrOH, ethylene glycol and i-PrOH affording preferentially the rccc isomer of the tetrasubstituted product. The methoxy derivative 6a undergoes isomerization upon attempted recrystallization from CHCl3/MeOH and its rcct and rctt forms were characterized by X-ray crystallography. Incorporation of hydroxy groups on the bridges was accomplished via solvolysis in AcOH, followed by LiAlH4 reduction of the acetoxy groups. Reaction of the tetra-(2-methylfuranyl)calixarene derivative 11 with benzyne followed by deoxygenation with Me3SiCl/NaI afforded in low yield the tetra-(4-methylnaphthyl)calix[4]arene derivative 12. Reaction of de-tert-butylated tetrabromo derivative 2a with m-xylene in HFIP followed by methylation of the crude product afforded the tetraxylyl derivative 14.     

A Note on the Distribution of the Distance from a Lattice

Let ℒ be an n-dimensional lattice, and let x be a point chosen uniformly from a large ball in ℝ ⁿ . In this note we consider the distribution of the distance from x to ℒ, normalized by the largest possible such distance (i.e., the covering radius of ℒ). By definition, the support of this distribution is [0,1]. We show that there exists a universal constant α ₂ that provides a natural “threshold” for this distribution in the following sense. For any ε>0, there exists a δ>0 such that for any lattice, this distribution has mass at least δ on [α ₂−ε,1]; moreover, there exist lattices for which the distribution is tightly concentrated around α ₂ (and so the mass on [α ₂+ε,1] can be arbitrarily small). We also provide several bounds on α ₂ and its extension to other ℓ _p norms. We end with an application from the area of computational complexity. Namely, we show that α ₂ is exactly the approximation factor of a certain natural protocol for the Covering Radius Problem. I. Haviv’s research was supported by the Binational Science Foundation and by the Israel Science Foundation. V. Lyubashevsky’s research was supported by NSF ITR 0313241. O. Regev’s research was supported by an Alon Fellowship, by the Binational Science Foundation, by the Israel Science Foundation, and by the European Commission under the Integrated Project QAP funded by the IST directorate as Contract Number 015848.     

Computer-aided elucidation of structures by carbon-13 nuclear magnetic resonance The DARC-EPIOS Method: Characterization of Ordered Substructures by Correlating the Chemical Shifts of Their Bonded Carbon Atoms

A reference substructure (SS) for which all spectral information (I) associated with each carbon atom is expressed as a function of the molecular environment is proposed. This information is expressed by topological relations, within this substructure, for which the spectral responses of its “bonded atoms” are linearly related to external alkyl effects. A correlation space (SS/I) is built with these topological relations (1–4 per carbon substructure). The resolving capacity of this SS/I space is greatly enhanced by introducing, in addition to all the reference substructures, some functions such as heteroatoms, cyclic structures, and stereochemical situations. The action of these functions is estimated by a statistical study of a large population of compounds from the DARC-PLURIDATA ¹³C-n.m.r. bank. This work introduces the notion of multiatom-centered substructure/multi-chemical shift relations, the discriminating ability of which compares very favorably to that of the notion of atom-centered substructure/monochemical shift relations. The generic reference subtructure defined as ELCO_b with its multichemical shifts constitutes a simple structural whole which is useful for critical improvement of the experimental reference data (distribution of spectral information and medium effects) and has proved to be excellent for the elucidation of new structures.     

Photovoltaic effects in hornets are correlated with the time of day

This study deals with voltage values recorded off the cuticle of live specimens of the Oriental hornet Vespa orientalis (Hymenoptera, Vespidae). The relevant measurements were taken between the two tips of their bodies at various hours of the day and were made on a total of 90 worker hornets. Recorded voltage values varied within a range of 60-180 mV, with the lower values measured during the morning hours and the afternoon and the highest values during the noon hours. Measurements were made by direct contact of the electrodes with the hornet cuticle and did not prove lethal to the measured specimens. An additional 60 live hornets were measured in the same fashion but in the dark. The values recorded in the dark varied between 40 and 70 mV and displayed considerable fluctuations but were not found to be dependent on the time of measurement. The distribution of the voltage values in hornets measured at various hours in the daytime closely resembled that of the global radiations (in W/m2) on the same days the measurements were taken.     

The reactivity of quaternary ammonium- versus potassium-fluorides supported on metal oxides: paving the way to an instantaneous detoxification of chemical warfare agents

The reactions of the chemical warfare agents (CWAs) 2,2'-dichloroethyl sulfide (HD), O-ethyl S-2-(diisopropylamino)-ethyl methylphosphonothioate (VX) and isopropyl methylphosphonofluoridate (GB) with various metal oxide-supported quaternary ammonium fluorides (QAF) and/or potassium fluoride (KF) reagents are described. These active sorbents, which were prepared by a modified procedure, include alumina, silica and titania, enriched with "available" (not bound to the surface) fluoride ions. Alumina-based fluoride reagents were found to be more active than their silica or titania counterparts. QAF/Al(2)O(3) reagents, compared to KF/Al(2)O(3), exhibit an exceptional reactivity toward HD, as demonstrated both in reaction rates and product identity. For example, with TBAF, t(1/2) is 15 min for the formation of the elimination product divinyl sulfide (DVS), while with KF, t(1/2) is 10 h for the formation of the hydrolysis product thiodiglycol (TDG). On the other hand, both sorbents reacted similarly against the nerve agents GB or VX. In order to increase the "available" fluoride content on the solid surface, the mixed active sorbent TBAF/KF/Al(2)O(3) (20/20/60) was developed. On this powder, all three CWAs were degraded instantaneously at the low loading of 1 wt% (t(1/2) < 2 min) and rapidly at the higher loadings of 5-10 wt% (t(1/2) of minutes scale). We assume that the relatively large amount of inorganic fluoride (KF) acts synergistically as a reservoir for the more reactive organic fluorides (TBAF). Moreover, the alumina surface hydroxyl groups may also operate as a water reservoir for the hydrolysis of VX or GB. Therefore, TBAF/KF/Al(2)O(3) might be considered as a promising destructive sorbent for CWAs.     

Hornet flight activity and its correlation with UVB radiation, temperature and relative humidity

During the active season, extending from June to October, hornets emerge from their nest in the field in all the daytime hours. In the beginning of the season, when the number of workers is relatively small, the number of exits from the nest is fairly uniform numerically throughout the day. However, with the increase in hornet population from July onwards, the number of workers emerging from the nest entrance around noon (1100-1300 h) is by 1-2 orders of magnitude greater than the number of those emerging in the morning or evening hours. This disparity persists till September or October, at which time the workers revert to behave as in the beginning of the season. It appears, therefore, that in this period hornet activities outside the nest are coordinated with the meteorological conditions, and in this regard, the highest correlation is with the ultra violet B (UVB) radiation level and to a lesser extent with the temperature. Presumably, also, the greater noon-hour activity in the nests of hornets in the field stems from the digging hornets benefiting from the greater availability of solar energy at noon, mainly that of UVB radiation. We assume that the hornets are able to utilize the UVB radiation, but what part of their body is "absorbing" the UVB energy is still a matter of further investigation.