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Particle track reconstruction is the most computationally intensive process in nuclear physics experiments. Traditional algorithms use a combinatorial approach that exhaustively tests track measurements ("hits") to identify those that form an actual particle trajectory. In this article, we describe the development of four machine learning (ML) models that assist the tracking algorithm by identifying valid track candidates from the measurements in drift chambers. Several types of machine learning models were tested, including: Convolutional Neural Networks (CNN), Multi-Layer Perceptrons (MLP), Extremely Randomized Trees (ERT) and Recurrent Neural Networks (RNN). As a result of this work, an MLP network classifier was implemented as part of the CLAS12 reconstruction software to provide the tracking code with recommended track candidates. The resulting software achieved accuracy of greater than 99\% and resulted in an end-to-end speedup of 35\% compared to existing algorithms.

Rent seeking leads to a misallocation of resources that worsens economic outcomes and reduces aggregate welfare. We conduct a quantitative examination of the distributional effects of rent extraction via the financial sector. Rent seeking introduces a possibility for insurance against idiosyncratic earnings risk that is more valuable for poorer households that are lacking in means of self insurance. However, it also creates a wedge that discourages savings, thus reducing self insurance via asset accumulation. When the model is calibrated to US data, the distorting effects dominate, implying welfare losses for all households, and an increase in wealth inequality. Nevertheless, welfare losses are bigger for households with higher initial wealth. Therefore, a policy reform to reduce rent seeking via the financial sector, despite being Pareto improving, will benefit predominantly wealthier households.

We consider a pure exchange economy with asymmetric information where individual behavior exhibits ambiguity aversion along the line of maximin expected utility decision making. For such economies, we introduce different notions of maximin value allocations. We also introduce a strong notion of incentive compatibility. We prove the existence and incentive compatibility of the maximin value allocation. We conclude that unlike the Bayesian value allocation approach in Krasa Yannelis (Econometrica 62(4):881–900, 1994), incentive compatibility is related to efficiency rather than to direct exchange of information.

The orthosymplectic extension of the Interacting Vector Boson Model (IVBM) is used for the simultaneous description of the spectra of different families of neighboring heavy nuclei. The structure of even-even nuclei is used as a core on which the collective excitations of the neighboring odd-mass and odd-odd nuclei are built on. Hence, the spectra of the odd-mass and odd-odd nuclei arise as a result of the consequent and self-consistent coupling of the fermion degrees of freedom of the odd particles, specified by the fermion sector $SO^{F}(2\Omega)\subset OSp(2\Omega/12,R)$, to the boson core which states belong to an $Sp^{B}(12,R)$ irreducible representation. The theoretical predictions for different low-lying collective bands with positive and negative parity for two sets of neighboring nuclei with distinct collective properties are compared with experiment and IBM/IBFM/IBFFM predictions. The obtained results reveal the applicability of the used dynamical symmetry of the model., Comment: 6 pages, 1 figure, A talk given at the 7th International Conference of the Balkan Physical Union, September 9-13, 2009, Alexandropoulos, Greece

In this work we show results of Monte Carlo modeling of electrons and heavy particles induced spatially resolved emission intensity or the Doppler profile in pure H2 discharge focusing on anode boundary. In particular we present study of fast H2 and fast H particles, scattered both at the surface and of the molecules. Since the anode boundary is characterized by a large electron flux, role of electron reflection and production of secondary electrons at the anode surface is part of the complete picture of spatial emission profile. In this work we verify our models of electron backscattering from the anode including both the reflection and the secondary electron production by making comparisons with the drift tube experiments. In order to achieve consistency with our previous results we select conditions of simulation appropriate for very high E/N (E‐electric field, N‐gas density) that are selected from experimental Townsend discharges in pure H2.

Several modalities are currently utilized for diagnosis and therapy, by appropriate application of x‐rays. In diagnostic radiology, interventional radiology, radiotherapy, interventional cardiology, nuclear medicine and other specialties radiation protection of a pregnant woman as a patient, as well as a member of the operating personnel, is of outmost importance. Based on radiation risk, the termination of pregnancy is not justified if foetal doses are below 100 mGy. For foetal doses between 100 and 500 mGy, a decision is reached on a case by case basis. In Diagnostic Radiology, when a pregnant patient takes an abdomen CT, then an estimation of the foetus’ dose is necessary. However, it is extremely rare for the dose to be high enough to justify an abortion. Radiographs of the chest and extremities can be done at any period of pregnancy, provided that the equipment is functioning properly. Usually, the radiation risk is lower than the risk of not undergoing a radiological examination. Radiation exposure in uterus from diagnostic radiological examinations is unlikely to result in any deleterious effect on the child, but the possibility of a radiation‐induced effect can not be entirely ruled out. The effects of exposure to radiation on the foetus depend on the time of exposure, the date of conception and the absorbed dose. Finally, a pregnant worker can continue working in an x‐ray department, as long as there is reasonable assurance that the foetal dose can be kept below 1 mGy during the pregnancy. Nuclear Medicine diagnostic examinations using short‐lived radionuclides can be used for pregnant patient. Irradiation of the foetus results from placental transfer and distribution of radiopharmaceuticals in the foetal tissues, as well as from external irradiation from radioactivity in the mother’s organ and tissues. As a rule, a pregnant patient should not undergo therapy with radionuclide, unless it is crucial for her life. In Radiotherapy, the patient, treating oncologist, other team and family members should carefully discuss for the decision of abortion. Important factors must be considered such as the stage and aggressiveness of the tumour, the location of the tumour, the stage of pregnancy, various therapies etc.

In the present paper we examine some aspects of using of microscopic models‐simulations in the teaching of Physics. Specifically, the aim is to investigate the effect of the microscopic model of thermal conduction in explaining a thermal phenomenon and to investigate the effect of the microscopic model of polarization in predicting an electrostatic phenomenon. Twenty‐five lower secondary students in compulsory education and 12 university pre‐service primary education student‐teachers, in Thessaloniki, Greece participated in the model‐based units of thermal conduction and electric polarization respectively. In both cases students were involved in model exploration rather than in model construction, however in electric polarization the “predictive” use of models has been adopted while in the case of thermal conductivity the approach emphasized explanation. Results showed that students, to a certain extend, managed to use the microscopic models of thermal conduction and electric polarization in order to explain and predict, respectively, the phenomena.

We present the time distribution of a large number (7798) of Myocardial Infractions (MI) recorded at the General Hospital ‘St. Panteleimon’ of the city of Nikea (in Piraeus, Greece), during time interval 1997–2007. This data set consisted of 5160 NON‐STEACS (non‐ST) and 2638 STEACS (ST) infractions are examined along with the monthly numbers of solar flares and Coronal Mass Ejections (CMEs), solar wind parameters and the geomagnetic activity (Dst geomagnetic index and other). The mean monthly value of ST and non‐ST events is 20 and 40 respectively. The maximum monthly value of non‐ST events (72 and 73) are recorded in October 2002 and January 2003, as well as the one of ST events (32), while solar maximum, recorded in November 2002. This time interval is characterized by magnetic storms from August 2002 peaked in October 2002 and ended in February 2003. It is noticeable that August 2002 corresponds to the solar maximum of CMEs and strong solar flares monthly values. The maximum monthly value of ST events (40) is recorded in November 2005 almost simultaneously with a sudden absence of solar flares (October 2005). Increased values have been recorded during a period of extreme solar events of October–November 2003 and January–March 2005. It seems from this extensive statistical study that there is an association between the monthly values of MI and of CMEs; the non‐ST MI shows a better association with CMEs. Moreover, the MI yearly distribution is in accordance with the time distribution of magnetic storms (number and duration). The non‐ST distribution is also affected by intense magnetic storms.

A novel slurry‐based process for aluminizing nickel foams while improving the mechanical properties and conserving the excellent ductility is reported. Cellular unalloyed nickel foams with 92% porosity and uniform pore size and distribution were used as a starting material. Several slurries of different compositions were examined to investigate the possibility of developing an aluminide‐nickel intermetallic coating on a Ni foam without considerably degrading the original ductile properties of the foam. The process temperature was varying from 400 to 850° C and the process holding time was ranging between 2h to 6h. Scanning electron microscopy with an energy dispersive X‐ray spectrometry and X‐Ray diffraction were applied to assess the effectiveness of the aluminizing process and determine both the optimum parameters of the procedure (slurry composition, holding temperature and time) and the concentration profiles across the coating cross‐section. The mechanical behavior of the aluminized Ni‐foams was evaluated by the conduction of micro‐tension tests. The resulting Ni‐foams after aluminization retain the pore structure of original Ni‐foams and present a thick outer surface layer which consists of a range of aluminide phases. The mechanical properties of the Ni‐foams aluminized in low process temperature were insignificantly affected.

The study of Munella ores is based on four analysis (A, B, Cand cores). They represent different types of minerals in the Munella area. Cores were taken by the geologist of Puka Geological Enterprise. A Core: It represents an ore with pyrite and chalcopyrite where copper and sulfur contents are 0.77 and 8.2% respectively. B Core: This core represents an ore with spharelites and pyrite where zinc content is 1.5% and 2.9% sulfur one. C Core: It is a chalcopyrite ore, massive in nature, where copper content is 2.01% and 36% sulfur one. D Core: It also represents copper‐ zinc—sulfur ore where their content is 0.66, 1.00 and 4.28% respectively. Each core is studied individually by selective schema to have copper, zinc and pyrite concentrates. Copper and pyrite concentrates will be the first material for pyro‐ metallurgical industry.

This paper presents several simple experiments in thermodynamics that enable students to accept and understand the basic thermodynamics laws and their practical application in an obvious way, through active learning by solving problems.

Plasma polymerized hexamethyldisiloxane (PPHMDS) is a polymer frequently considered for biomedical application due to its easy fabrication, low cost and biocompatibility. However, a drawback of using PPHMDS in osteosubstitutive engineering is its high hydrophobicity, causing extremely low cellular interaction. Surface wettability can be altered in many ways such as plasma treatment, surface coating, introduction of hydrophilic or hydrophobic groups by self‐assembled monolayers, etc. Among all these methods plasma treatment is one of most effective and economical ways to modify surface wettability of a material. Here, we investigated three different PPHMDS layers prepared by plasma polymerization (PP) of HMDS on cover glass (CG) under two different technological regimes. In order to improve cellular interactions, PPHMDS films obtained by the second operating mode were further hydrophylized in NH3 plasma. Cell‐biomaterial interactions were characterized by human osteoblast‐like MG63 cell model, where overal...

Some chemical compound with fluorescence properties can be used as artificial tracers for water system studies. The problem in this case is dealt with in relation to applying Sulphorhodamine G Extra to trace and study underground communications between Prespa and Ohrid Lakes. The fluorescence intensity of Sulphorhodamine G Extra (SRG) in water samples depends on their chemical and physical properties, such as pH, presence of oxidants, temperature, etc. This paper presents the experience of the Center of Applied Nuclear Physics, Tirana, in this field. The method we have elaborated to this purpose made it possible to optimize procedures we use to analyze water samples for the presence of Sulphorhodamine G Extra and measure its content, even in trace levels, by the means of a Perkin Elmer LS 55 Luminiscence Spectrometer.

Cosmic ray detectors are widely used, for educational purposes, in order to motivate students to the physics of elementary particles and astrophysics. Using a “telescope” of scintillation counters, the directional characteristics, diurnal variation, correlation with solar activity, can be determined, and conclusions about the composition, origin and interaction of elementary particles with the magnetic field of earth can be inferred. A telescope was built from two rectangular scintillator panels with dimensions: 91.6×1.9×3.7 cm3. The scintillators are placed on top of each other, separated by a fixed distance of 34.6 cm. They are supported by a wooden frame which can be rotated around a horizontal axis. Direction is determined by the coincidence of the signals of the two PMTs. Standard NIM modules are used for readout. This device is to be used in the undergraduate nuclear and particle physics laboratory. The design and construction of the telescope as well as some preliminary results are presented.

A fractal distribution requires that the number of objects larger than a specific size r has a power‐law dependence on the size N(r) = C/rD∝r−D where D is the fractal dimension. Usually the correlation integral is calculated to estimate the correlation fractal dimension of epicentres. A ‘box‐counting’ procedure could also be applied giving the ‘capacity’ fractal dimension. The fractal dimension can be an integer and then it is equivalent to a Euclidean dimension (it is zero of a point, one of a segment, of a square is two and of a cube is three). In general the fractal dimension is not an integer but a fractional dimension and there comes the origin of the term ‘fractal’. The use of a power‐law to statistically describe a set of events or phenomena reveals the lack of a characteristic length scale, that is fractal objects are scale invariant.Scaling invariance and chaotic behavior constitute the base of a lot of natural hazards phenomena. Many studies of earthquakes reveal that their occurrence exhibits s...

The thermostimulated discharge current method (TSDC) is widely used for the study of charge storage mechanisms in electrets. A new discharged technique, called differential, which consists in discharging a charged sample through an otherwise identical but uncharged one, has been proposed by J.‐P. Reboul and A. Toureille. In the present paper a new version of the differential thermostimulated discharge current method is advanced. In contrast to the differential technique described earlier, the measuring cell allows to realize typical differential technique. In this case the measuring system records the difference of the thermostimulated currents of two samples which have been preliminary charged (or thermally treated) under the same or different conditions. Samples of 0.85 mm thick polymethylmethacrylate are used to demonstrate an operation of the developed differential TSDC method.

Study of the linear harmonic oscillator confined in the square well with impenetrable walls is of great interest since its application for modeling parabolic quantum well semiconductor heterostructures. Fisher information and Shannon entropy, as a complexity measure for its ground and some excited energy levels are reported here.

Thin AuAgOx films with prolonged lifetimes (up to 1 1/2years) were produced by reactive sputtering in a magnetron allowing a smooth variation of the degree of ion assistance by an external solenoid. The film specific electric resistivity and the film lifetimes were found to be single power functions of a combined parameter representing a product of solenoid current and oxygen gas pressure divided by magnetron discharge power.

The design of alloys, that economize strategic element as chromium requires detailed physical investigations of their structure and phase composition. In the search for new materials in the last two decades a new class of Fe alloys was composed—the so‐called nitrogen steels. The contemporary achievements in the casting technology—the use of nitrogen under high preasure above the melt—made possible the production of Fe alloys with nitrogen concentration even above 0.4 wt%. The wide application of investigated alloy system is connected with creation of alloys without presence of strong carbides‐forming elements. The microstructure and phase formation of these new materials are insufficiently studied. The aim of this work is to characterize the microstructure and phase composition of two series Fe‐alloys casted with and without nitrogen pressure above the melt. The so cast steels appear as experimental ones and they are directed to demonstrate the possibility for nitrogen doping of steels without presence of...

In this study, response of the cofacial bis‐ phthalocyanine film to vapor of Volatile Organic Compounds (VOCs) was investigated. Test gases were vapors of acetone, toluene, ethanol and ammonia. Measurements were carried out between the temperatures of 293 K–423 K. Bis‐phthalocyanine was dissolved in chloroform. Thin film of bis‐phthalocyanine was deposited by spraying method on glass substrate patterned with Interdigital Transducer (IDT). During the measurements 0.5 volts were applied to the IDT. Response characteristics of the film were determined by means of change in dc conductivity as a function of gas concentration and temperature. Gas concentrations were controlled by mass flow controller. Dry nitrogen was used as carrier gas. Vapor pressure of the VOCs was calculated using Antoine equation. Response characteristics of the film were determined in a wide range of gas concentration (0.25%–18%). The film showed good sensitivity to the VOCs vapors in the measurement range. The responses of the film were...

We use the three‐species cyclic competition model (Rock‐Paper‐Scissors), described by reactions A+B→2B, B+C→2C, C+A→2A, for emulating a computer network with e‐mail viruses. Different topologies of the network bring about different dynamics of the epidemics. When the parameters of the network are varied, it is observed that very high clustering coefficients are necessary for a pandemics to happen. The differences between the networks of computer users, e‐mail networks, and social networks, as well as their role in determining the nature of epidemics are also discussed.

In the context of the European Project on Material Science we have developed a Teaching Learning Sequence (TLS), which is composed by units for teaching thermal conductivity in depth to students. The scientific content has been adapted to students’ conceptions taking into account research results. Units follow the Predict‐Observe‐Explain strategy and students conduct guided investigations using an enriched learning environment, which consists of extensive use of ICT based tools. Didactically transformed microscopic models depict thermal interactions in iconic, graphic and symbolic forms. Students working in groups, solve problems, explore models and are engaged in classroom discussion on the problem under study, constructing links between evidence and explanations. In this paper the structure of such innovative units is presented and results showing students’ development in scientific understanding are reported.

The electronic structure and magnetic properties of FexPt1−x disordered alloys have been studied by means of the tight‐binding linear muffin‐tin orbital method in the atomic sphere approximation and in conjunction with the coherent potential approximation. The iron magnetic moment depends linearly on composition. As the pressure increases there are phase transitions from magnetic to nonmagnetic states. The volume magnetostriction is evaluated within disordered local moment formalism. A good agreement with the experimental results is obtained in the Invar composition range. The volume magnetostriction rapidly decreases with increasing Pt content.

Series of relatively large earthquakes in different regions of the Earth are studied. The regions chooses are of a high seismic activity and has a good contemporary network for recording of the seismic events along them. The main purpose of this investigation is the attempt to describe analytically the seismic process in the space and time. We are considering the statistical distributions the distances and the times between consecutive earthquakes (so called pair analysis). Studies conducted on approximating the statistical distribution of the parameters of consecutive seismic events indicate the existence of characteristic functions that describe them best. Such a mathematical description allows the distributions of the examined parameters to be compared to other model distributions.

Polycrystalline silicon (poly‐Si) layers were functionalized through the growth of biomimetic hydroxyapatite (HA) on their surface. HA is the mineral component of bones and teeth and thus possesses excellent bioactivity and biocompatibility. MG‐63 osteoblast‐like cells were cultured on both HA‐coated and un‐coated poly‐Si surfaces for 1, 3, 5 and 7 days and toxicity, proliferation and cell morphology were investigated. The results revealed that the poly‐Si layers were bioactive and compatible with the osteoblast‐like cells. Nevertheless, the HA coating improved the cell interactions with the poly‐Si surfaces based on the cell affinity to the specific chemical composition of the bone‐like HA and/or to the higher HA roughness.

In this article we present an alternative explanation of the phenomenon of wire fragmentation under high transient currents based on classical electromagnetism. We also explain how this phenomenon can be utilized as a primitive example of low energy‐high power disruptive phenomena that can affect even nuclear matter.

A tunable electro‐optical switching is reported for single‐layered polymer‐dispersed liquid crystal (PDLC) films, controlled by the film thickness. Thin planar film of two‐dimensional layer of thickness continuously varying from a few micrometers to several tens of micrometers is examined. The wedge‐confined PDLC single layer contains E7 liquid‐crystal microdroplets dispersed in a transparent polymer matrix of NOA65. The diameters of the droplets with a linear‐gradient size distribution along the wedge slope reach several tens of micrometers, defined by the wedge geometry of the film. The electro‐optical switching of the single‐layered PDLC film is linked to its microstructure and droplet organization.

From May 2004, in the Institute of Nuclear Physics is installed Albanian Radiological Monitoring Network, in the framework of emergency monitoring in the territory of Albania. In this network, this is unique monitoring on‐line system in our country. are included 5(five) monitoring stations, respectively in Tirane, Shkoder, Kukes, Korce and Vlore. The last four stations are near Albanian borders The network performs measures of ambient dose rate in a range from 5 nSv/h up to 10 Sv/h. For measurements are used detector of type VACUTEC 70045 A, which are calibrated in the Centre of Applied Nuclear Physics, University of Tirana, using standard radiation source Cs‐137. This monitoring help to warn in real time the relative authorities, in case of radiological accidents of 5th degree (for example accidents in nuclear power plants, near Albanian territory).