Many ``real-world'' networks are clearly defined while most ``social'' networks are to some extent subjective. Indeed, the accuracy of empirically-determined social networks is a question of some concern because individuals may have distinct perceptions of what constitutes a social link. One unambiguous type of connection is sexual contact. Here we analyze data on the sexual behavior of a random sample of individuals, and find that the cumulative distributions of the number of sexual partners during the twelve months prior to the survey decays as a power law with similar exponents $\alpha \approx 2.4$ for females and males. The scale-free nature of the web of human sexual contacts suggests that strategic interventions aimed at preventing the spread of sexually-transmitted diseases may be the most efficient approach.

The Web of Human Sexual Contacts

Conventional approaches to chemical sensors have
traditionally made use of a “lock-and-key” design,
wherein a specific receptor is synthesized in order to
strongly and highly selectively bind the analyte of
interest.1-6 A related approach involves exploiting a
general physicochemical effect selectively toward a
single analyte, such as the use of the ionic effect in
the construction of a pH electrode. In the first
approach, selectivity is achieved through recognition
of the analyte at the receptor site, and in the second,
selectivity is achieved through the transduction
process in which the method of detection dictates
which species are sensed. Such approaches are appropriate
when a specific target compound is to be
identified in the presence of controlled backgrounds
and interferences. However, this type of approach
requires the synthesis of a separate, highly selective
sensor for each analyte to be detected. In addition,
this type of approach is not particularly useful for
analyzing, classifying, or assigning human value
judgments to the composition of complex vapor
mixtures such as perfumes, beers, foods, mixtures of
solvents, etc.

/pdf/cross-reactive-chemical-sensor-arrays-38dz1buu0b.pdf

Cross-reactive chemical sensor arrays.

GEMS (Gamma Energy Marine Spectrometer) is a prototype of an autonomous radioactivity sensor for underwater measurements, developed in the framework for a development of a submarine telescope for neutrino detection (KM3NeT Design Study Project). The spectrometer is highly sensitive to gamma rays produced by 40 K decays but it can detect other natural (e.g., 238 U, 232 Th) and anthropogenic radio-nuclides (e.g., 137 Cs). GEMS was firstly tested and calibrated in the laboratory using known sources and it was successfully deployed for a long-term (6 months) monitoring at a depth of 3200 m in the Ionian Sea (Capo Passero, offshore Eastern Sicily). The instrument recorded data for the whole deployment period within the expected specifications. This monitoring provided, for the first time, a continuous time-series of radioactivity in deep-sea.

/pdf/gems-underwater-spectrometer-for-long-term-radioactivity-38x0f1k4b3.pdf

GEMS: Underwater spectrometer for long-term radioactivity measurements

The abundance of solar thermal energy and the widespread demands for waste heat recovery make thermoelectric generators (TEGs) very attractive in harvesting low-cost energy resources. Meanwhile, thermoelectric refrigeration is promising for local cooling and niche applications. In this context there is currently a growing interest in developing organic thermoelectric materials which are flexible, cost-effective, eco-friendly and potentially energy-efficient. In particular, the past several years have witnessed remarkable progress in organic thermoelectric materials and devices. In this review, thermoelectric properties of conducting polymers and small molecules are summarized, with recent progresses in materials, measurements and devices highlighted. Prospects and suggestions for future research efforts are also presented. The organic thermoelectric materials are emerging candidates for green energy conversion.

Organic Thermoelectric Materials: Emerging Green Energy Materials Converting Heat to Electricity Directly and Efficiently

Interaction of nanostructured metal overlayers with oxide surfaces

Simulated annealing for optimal ship routing

The effect of humidity on tin-oxide thick-film gas sensors has been studied in the case of carbon monoxide, methane, methanol, butane and propane. The results are qualitatively explained under the assumption that water molecules dissociate on the tin-oxide surface and produce hydroxyl species capable of acting as electron donors. Moreover, palladium and vanadium, when used as additives, affect the overall behaviour of sensors in the presence of water vapour. To reduce the effect of humidity, thin organometallic films have been deposited on top of thick tin-oxide-based sensors in order to act as filters. The results show that both the sensitivity of these sensors and the effect of humidity are decreased.

The effect of humidity on tin-oxide thick-film gas sensors in the presence of reducing and combustible gases

Reactively sputtered SnOx and InOx thin films, plain and surface doped with Pt, have been covered with layers of various insulating films and catalysts Test gases used are carbon monoxide, methane, ethanol, butane and propane Filters used are alumina (Al2O3), silicon oxide (SiO2) and tungsten trioxide (WO3) Palladium has also been added on the surface of alumina filters, while platinum is added on the surface of metal-oxide sensor films Response to hydrocarbons, and especially to butane and propane is found to be enhanced with the addition of noble metals on the sensing film or on the filter It is also found that a WO3 filter improves the carbon monoxide sensitivity at low working temperatures and reduces the sensor response to ethanol with respect to other test gases The behaviour of indium-oxide-based sensors is qualitatively very similar to that of tin-oxide-based sensors

Comparative study of various metal-oxide-based gas-sensor architectures

In this paper an exponential fitted partitioned linear multistep method is developed for the long term integration of the N-body problem. The new method integrates exactly any linear combination of the functions 1, x, x2, x3 ,…, x2k–1, exp(±wx) for the coordinates and any linear combination of the functions 1, x, x2, x3,…, x2k–3, exp(±wx) for the velocities. Numerical results are produced and compared with a set of well known symplectic and single step methods. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Partitioned Linear Multistep Method for Long Term Integration of the N‐Body Problem

Long term performance of tin and indium oxide thin films with palladium and platinum deposited on their surface as catalysts was studied using a standardization method proposed recently by other researchers. A simple gas classification algorithm was used to investigate the validity of the standardization method proposed and to study the effect of doping type and thickness onto the surface of SnO x and InO x films on their selectivity and stability characteristics. It was found that: (a) the proposed method is reliable for the assessment of sensor degradation; and (b) sensors with relatively thick additive layer are more reliable.

Dimitrios Vlachos

Papers

Simulated annealing for optimal ship routing

The effect of humidity on tin-oxide thick-film gas sensors in the presence of reducing and combustible gases

Comparative study of various metal-oxide-based gas-sensor architectures

Partitioned Linear Multistep Method for Long Term Integration of the N‐Body Problem

Effect of surface catalysts on the long-term performance of reactively sputtered tin and indium oxide gas sensors