Missing energies at pair creation

Wilson cloud chamber measurements of the separated spectra of positrons and electrons produced by gamma quanta of 6.14 MeV differ considerably from the theoretically predicted spectra by BETHE and HEITLER, but are in good agreement with those of a modified theory of pair creation

The landscape context of planning for recreation: "the psycho- physiological approach to the design of open spaces"

The demand of modern living with social and economic tensions has created a society characterised by change. This constant change in most aspects of daily life has encouraged an increasing number of people to turn to recreation interests as a means of gaining inner satisfaction, self expression and personal fulfilment. Recreation has become an important component of the urban planning and design for societies.The research is devoted to the study of recreation as a vital component of life. Its importance stems from its maintenance of the physical and mental health for both society and individuals. The lack of satisfactory planning and design for recreation in a society would accordingly lead to slow disintegration

Towards a code of ethics for community psychology and community practice in the Arab world: Defining ethical values

In response to the need for ethical guidance in Arab community psychology and other forms of community practice, this thesis used mixed methods to explore the ethical values that are of relevance to community psychologists and other community practitioners in the Arab World. A total of 18 community practitioners in the Arab region were interviewed to share their views on the importance of Arab societal values, the values of community psychology, and the principles identified in globally dominant codes of ethics for psychologists in community practice in the Arab world. Using thematic analysis, 53 themes were identified in the collected qualitative data, portraying the most important and influential values in Arab community practice. Moreover, 211 community practitioners in the Arab world responded to a self-administered questionnaire on the extent to which certain values are beneficial or problematic for Arab community practice. Descriptive statistics were used to analyze the questionnaire, identifying the most beneficial values, controversial values and values that were sometimes viewed as irrelevant to Arab community practice. Based on the interview and questionnaire data, a list of recommended ethical values for Arab community practice is identified. Since codes of ethics are built on values, the results of this research are the first step towards building a comprehensive and culturally relevant code of ethics for community practitioners, including community psychologists, in the Arab region

Koeficijenti udarne ionizacije elektronom i šupljinom u poluvodičima s jakim poljem

We have fitted the soft lucky drift model of impact ionization of Ridley to experimental data for GaAs, InP, Si, Ge and In0.47Ga0.53As semiconductors. Excellent fits of the theory to experimental data were obtained by using least-squares fitting algorithm. A generalized Keldysh formula has been used to introduce a soft threshold factor. Generalized Keldysh formula originates from realistic energy bands in semiconductors at high electric field which reflects the density of states of energy bands. Keldysh factor and a new mean free path are calculated. A comparison with reported values of both Ridley and Marsland showed reasonable agreement for mean free path, but there are still large differences among Keldysh factors.Načinili smo prilagodbe Ridleyvog mekog sretno-posmičnog modela eksperimentalnim podacima za GaAs, InP, Si, Ge i In0.47Ga0.53As. Postigli smo odlično slaganje teorije i eksperimentalnih podataka primjenom metode najmanjih kvadrata. Primijenili smo poopćenu Keldyshevu formulu radi uvođenja mekog faktora praga. Poopćena Keldysheva formula proizlazi iz realnih razmatranja energijskih vrpci u poluvodičima s jakim električnim poljima što odražava gustoću stanja energijskih vrpci. Izračunali smo Keldyshev faktor i nove vrijednosti srednjih slobodnih puteva. Ridleyeve and Marslandove objavljene vrijednosti za srednje slobodne puteve u dobrom su skladu s našima, ali još uvijek nalazimo velike razlike među Keldyshevim faktorima

Koeficijenti udarne ionizacije elektronom i šupljinom u poluvodičima s jakim poljem

We have fitted the soft lucky drift model of impact ionization of Ridley to experimental data for GaAs, InP, Si, Ge and In0.47Ga0.53As semiconductors. Excellent fits of the theory to experimental data were obtained by using least-squares fitting algorithm. A generalized Keldysh formula has been used to introduce a soft threshold factor. Generalized Keldysh formula originates from realistic energy bands in semiconductors at high electric field which reflects the density of states of energy bands. Keldysh factor and a new mean free path are calculated. A comparison with reported values of both Ridley and Marsland showed reasonable agreement for mean free path, but there are still large differences among Keldysh factors.Načinili smo prilagodbe Ridleyvog mekog sretno-posmičnog modela eksperimentalnim podacima za GaAs, InP, Si, Ge i In0.47Ga0.53As. Postigli smo odlično slaganje teorije i eksperimentalnih podataka primjenom metode najmanjih kvadrata. Primijenili smo poopćenu Keldyshevu formulu radi uvođenja mekog faktora praga. Poopćena Keldysheva formula proizlazi iz realnih razmatranja energijskih vrpci u poluvodičima s jakim električnim poljima što odražava gustoću stanja energijskih vrpci. Izračunali smo Keldyshev faktor i nove vrijednosti srednjih slobodnih puteva. Ridleyeve and Marslandove objavljene vrijednosti za srednje slobodne puteve u dobrom su skladu s našima, ali još uvijek nalazimo velike razlike među Keldyshevim faktorima

Gustoća i viskoznost poluvodičkog spoja AgGaSe2 u čvrstom i tekućem stanju

The density and kinematic viscosity of AgGaSe2 were investigated in the solid and liquid states in the temperature range 690 - 930 °C. Density and dynamic viscosity measurements were carried out using the thermometer method and the rotating cylinder method. Experimental data show that the dependence of viscosity on temperature has an activation character and that logarithm of viscosity vs. reciprocal absolute temperature can be approximated by two straight lines corresponding to activation energies 0.36 eV and 0.19 eV in the solid and liquid states, respectively. The temperature dependence of the free volume was calculated and it was found that it decreases linearly with temperature. The results are explained on the basis of the free-volume model.Istraživali smo gustoću i kinematičku viskoznost AgGaSe2 u čvrstom i tekućem stanju na temperaturama 690 – 930 ◦C. U mjerenjima gustoće i viskoznosti primijenili smo termometrijsku metodu odnosno metodu rotirajućeg valjka. Mjerni podaci ukazuju da ovisnost viskoznosti η o temperaturi ima aktivacijske značajke, te se ovisnost log η o temperaturi može aproksimirati pravcima koji odgovaraju aktivacijskim energijama 0.36 eV and 0.19 eV za čvrsto odnosno tekuće stanje. Izveli smo i temperaturnu ovisnost slobodnog volumena i našli da se linerno smanjuje s temperaturom. Ishodi mjerenja tumače se na osnovi modela slobodnog volumena

Gustoća i viskoznost poluvodičkog spoja AgGaSe2 u čvrstom i tekućem stanju

The density and kinematic viscosity of AgGaSe2 were investigated in the solid and liquid states in the temperature range 690 - 930 °C. Density and dynamic viscosity measurements were carried out using the thermometer method and the rotating cylinder method. Experimental data show that the dependence of viscosity on temperature has an activation character and that logarithm of viscosity vs. reciprocal absolute temperature can be approximated by two straight lines corresponding to activation energies 0.36 eV and 0.19 eV in the solid and liquid states, respectively. The temperature dependence of the free volume was calculated and it was found that it decreases linearly with temperature. The results are explained on the basis of the free-volume model.Istraživali smo gustoću i kinematičku viskoznost AgGaSe2 u čvrstom i tekućem stanju na temperaturama 690 – 930 ◦C. U mjerenjima gustoće i viskoznosti primijenili smo termometrijsku metodu odnosno metodu rotirajućeg valjka. Mjerni podaci ukazuju da ovisnost viskoznosti η o temperaturi ima aktivacijske značajke, te se ovisnost log η o temperaturi može aproksimirati pravcima koji odgovaraju aktivacijskim energijama 0.36 eV and 0.19 eV za čvrsto odnosno tekuće stanje. Izveli smo i temperaturnu ovisnost slobodnog volumena i našli da se linerno smanjuje s temperaturom. Ishodi mjerenja tumače se na osnovi modela slobodnog volumena

Dielectric Function in Highly doped GaN Semiconductor

Inverse of Dielectric Function of highly doped  GaN has been calculated by using Lindhard formalism.  For simplicity collisional damping,  nonparabolicity and the coupling  between various  electrons and holes  were  neglected. The inverse of the dielectric function for both Fermi- Dirac and Maxwell Boltzman distribution showed antiscreening peak at small phonon wave vector. On the contrary, both Thomas Fermi and Debye inverse of dielectric function showed screening as expected at same phonon wave vector. There is a sharp growth in the antiscreening peak in the inverse of dielectric function at carrier temperature 77 K and 300K, accompanied with a singularity at carrier concentration greater than . Key words: dielectric function, GaN and screened optical phonon scattering rat

GENUS MICROMERIA: A REVIEW ARTICLE

Micromeria (Family Lamiaceae) is widespread across Europe, Asia, Africa and North America, with a center of diversity in the Mediterranean region and the Canary Islands. More than 78 species of Micromeria have been known, famous examples is: M. fruticose.Genus Micromeria comprises plants of different chemical nature. Based on previous studies, Micromeria species is considered as a rich source of essential oils, mainly; monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpenes hydrocarbons, and oxygenated sesquiterpenes. About ten species of Micromeria have been identified to grow widely in Lebanon, of which Micromeria fruticosa is the most common and abundant. Several pharmacological activities were reported including antimicrobial, antioxidant, anticancer, and antidepressant effect. This is a review article where we thoroughly discuss the chemical nature and classes of all isolated metabolites from Micomeria plant especially Micromeria fruticosa and their reported biological activities in an attempt to inspire the researchers to isolate and structural elucidate the compounds that could have valuable use in drug discovery and medical application