In September 2016 and 2017, Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae), the striped mealybug, was collected on Lantana camara (Verbenaceae) in Khezama City (Governorate Sousse, Tunisia). ...The mealybug was observed on leaves and shoots and also on the flowers. This is the first record of F. virgata in Tunisia and in North Africa. Brief information about its worldwide distribution and biology is presented.
Ferrisia virgata Cockerell (Hemiptera : Pseudococcidae): premier signalement en Tunisie
Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae) a été collecté dans la région Khezama (Sousse, Tunisie) sur Lantana camara (Verbenaceae). L'infestation a été observée en septembre 2016 et 2017 au niveau des feuilles, des jeunes pousses et des fleurs. Ceci constitue le premier signalement de F. virgata en Tunisie et au Nord de l'Afrique. Un aperçu bref sur sa distribution et sa biologie est donné.
Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae): первое сообщение из Туниса
В сентябре 2016 и 2017 гг. на Lantana camara (Verbenaceae) в городе Хезама (провинция Сусс, Тунис) был собран полосатый червец Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae). Полосатый червец был обнаружен на листьях, побегах, а также на цветах. Это первое сообщение о F. virgata для Туниса и для Северной Африки. Представлена краткая информация о его распространении в мире и его биологии.
The Aphidiinae (Hymenoptera: Braconidae) are solitary endoparasitoids and koinobionts which are frequently used as biological control agents against aphids. Six aphidiine genera and 15 parasitoid ...species from 18 aphid taxa occurring on 42 plant taxa belonging to 18 botanic families were identified and 49 parasitoid-aphid associations are reported. In addition, this survey exhibits two species which are Aphidius platensis (Brethes, 1913) and Praon barbatum (Mackauer, 1967) and they are reported for the first time in Tunisia.
Structural, magnetic and magnetocaloric properties of La
0.6
Ca
0.4
Mn
1−
x
Fe
x
O
3
(0 ≤
x
≤ 0.3) manganites, synthesized using the sol-gel method, were investigated. Rietveld refinement of the ...X-ray diffraction patterns show that all our samples have single phase and crystallize in the orthorhombic structure with the Pnma space group. The unit cell volume increases when increasing the Fe content. Fe doping leads to a weakening of the ferromagnetic (FM) ordering at low temperature, the Curie temperature
T
C
decreases from 260 K for
x
= 0 to 44 K for
x
= 0.2. The magnetocaloric effect (MCE) was estimated, in terms of isothermal magnetic entropy change (−
ΔS
M
), using the
M
(
T
,
μ
0
H
) data and employing the thermodynamic Maxwell equation. The maximum value of the magnetic entropy change, (−
ΔS
M
max
) decreases from 3.66 J/kg K for
x
= 0 to 2.38 J/kg K for
x
= 0.1 under an applied magnetic field change of 5T. The magnetic-entropy change is 1.67 J/kg K at
T
C
(260 K) for a magnetic field of 2T and the RCP is 65 J/kg, which suggests the La
0.6
Ca
0.4
MnO
3
compound as a possible candidate for magnetic refrigerants near room temperature.
We report the synthesis and structural study of mixed oxides in the Ln2ScNbO7 series. New phases with Ln = Pr, Eu, Gd and Dy are obtained. All crystallize in the cubic pyrochlore structure type, ...space group F-d3m, with no Sc-Nb ordering on the B site. The structures are determined by Rietveld refinement. The evolution of cell parameters, interatomic distances and angles as a function of lanthanide cation size is discussed. Magnetic measurements show the absence of ordering down to 2 K, in agreement with the presence of strong geometric frustration in the lanthanide sublattice. The europium phase shows a peculiar magnetic behaviour; its magnetic susceptibility becomes constant below ca 50 K. This feature confirms the behaviour observed previously on Eu2Ti2O7 and is ascribed to crystal field effects.
We report in this paper the physico-chemical properties of Pr
0.6
La
0.1
Ba
0.3
Mn
1−
x
Fe
x
O
3
(with 0 ≤
x
≤ 0.3 compounds. Our manganites were prepared using the sol-gel method. Structural studies ...showed that our compounds are single-phase ones and they crystallize in the orthorhombic system with the Pnma space group. The substitution of Mn by Fe induces a ferromagnetic phase at low temperatures. From isothermal magnetization
versus
magnetic applied field we deduced the magnetic entropy change. The maximum value |
ΔS
M
Max
| of our parent compound reached 1.43 J/kg · K and 2.92 J/kg · K under magnetic field of 2 and 5T, respectively. Our results suggest that these materials may be suitable candidates in magnetic refrigeration at low temperature.
In this paper we consider finite \beta-expansions in the field of
formal series with Pisot basis \beta. We are studying the arithmetic
operations on \beta-expansions and provide bounds on the number ...of
fractional digits arising in multiplication for arbitrary
\beta-polynomials noted L_\odot. This value is given explicitly
for families of Pisot basis. The last part of this paper is devoted to
quadratic Pisot series where we will give the exact value for
L_\odot.
The objective of this study was to follow the crack propagation in the tooth foot of a spur gear by using Linear Elastic Fracture Mechanics (LEFM) and the Finite Element Method (FEM). The tooth foot ...crack propagation is a function of Stress Intensity Factors (SIF) that play a very crucial role in the life span of the gear. A two-dimensional quasi-static analysis is carried out using a program that determines the gear geometry, coupled with the Finite Element Code (ANSYS). The study estimates the stress intensity factors and monitors their variations on the tooth foot according to crack depth, crack propagation angle, and the crack position. An appropriate methodology for predicting the crack propagation path is applied by considering gear tooth behavior in bending fatigue. The results are used to predict/prevent catastrophic rim fracture failure modes from occurring in critical components.PUBLICATION ABSTRACT
.
Structural, magnetic and magnetocaloric properties of La
0.7
Sr
0.3
MnO
3
sample have been investigated. Powder sample has been elaborated by the ball milling method. The Rietveld analysis of the ...powder X-ray diffraction shows that the sample crystallizes in the orthorhombic structure with
Pnma
space group. Magnetic measurements showed that the sample exhibits a ferromagnetic-to-paramagnetic transition at a Curie temperature close to 370 K. The magnetic entropy change (
) has been deduced by the Maxwell relation method. The maximum value of the magnetic entropy change
is found to be 1.1 J/kgK for an applied magnetic field of 2T. At this value of magnetic field the relative cooling power (RCP) is 49 J/kg. At high temperature, large change in magnetic entropy has been observed in the sample. Our result on magnetocaloric properties suggests that La
0.7
Sr
0.3
MnO
3
nanopowder is attractive as a possible refrigerant for high temperature magnetic refrigeration.
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