Papers by Cristina Hretcanu
We study the properties of the composition of two Riemannian immersions of codimension one. A Rie... more We study the properties of the composition of two Riemannian immersions of codimension one. A Riemannian immersion is an isometric immersion between two Riemannian manifolds. First, we establish the Gauss and Weingarten formulae of the composition in dependence on the second fundamental forms and the Weingarten maps (shape operators) of factors. Then, we apply these for particular Riemannian immersions (totally geodesic, totally umbilical, minimal) for obtaining information about their composition. The computations are done in local coordinates.
Heavy metals in cigarettes were determined considering that the number of smokers of both sexes i... more Heavy metals in cigarettes were determined considering that the number of smokers of both sexes is growing. Besides air, water, food raw materials, foodstuff, dietary supplements, the human body can accumulate heavy metals from tobacco. Tobacco samples from Romanian and Ukrainian market were analyzed using inductively coupled plasma mass spectrometry (ICPMS). The results showed that the Romanian samples have lower content of heavy metal than the Ukrainian samples. Tolerable weekly intake of cadmium was over in the case of two samples for minimum and maximum consumption and in the case of three samples for maximum consumption.
Facta Universitatis, Series: Mathematics and Informatics, 2018
We characterize the metallic structure on the product of two metallic manifolds in terms of metal... more We characterize the metallic structure on the product of two metallic manifolds in terms of metallic maps and provide a necessary and sufficient condition for the warped product of two locally metallic Riemannian manifolds to be locally metallic. The particular case of product manifolds is discussed and an example of metallic warped product Riemannian manifold is provided.
arXiv: Differential Geometry, Apr 15, 2018
We characterize the metallic structure on the product of two metallic manifolds in terms of metal... more We characterize the metallic structure on the product of two metallic manifolds in terms of metallic maps and provide a necessary and sufficient condition for the warped product of two locally metallic Riemannian manifolds to be locally metallic. The particular case of product manifolds is discussed and an example of metallic warped product Riemannian manifold is provided.
The main objective of the paper is the harmonization of instrumental testings of food texture wit... more The main objective of the paper is the harmonization of instrumental testings of food texture with methods of human sensory analysis as they are defined and described in reference standard ISO 11036. Lack of dual standardized system of advanced food texture characterization in admission of instrumental methods and means besides human sensory methods of characterization and the impossibility of numerical quantifying, with high-resolution of human perceptions, subjective assessment of texture characteristics and low reproducibility of testing, makes human sensory tests remain far behind those of texture establishing. The paper presents a concept of multifunctional electronic equipment, with force and displacement sensors and complex devices for an advanced characterization of food texture.
In this work it has searched the influence of storage conditions upon ascorbic acid content, in J... more In this work it has searched the influence of storage conditions upon ascorbic acid content, in Jonathan and Golden apples. The study of ascorbic acid content and pH evolutin for 16 weeks has been carried out using, as biological material, apple samples from Jonathan and Golden varieties, coming from the orchards in the area of Fălticeni. The apples were kept in containers of glass and wood, constituting, for each sample, variants of experiences, in the presence and in the absence of oxygen, at following thermal thresholds: 4°C, 8°C and 15°C. In order to keep the apples in the presence of oxygen, they were placed in wooden boxes. To store apples in an oxygen-free environment, it used glass containers where the fruits were introduced along with a small candle lit, and then the lid of the container was tightly closed. The extinguish of the candle has confirmed that the oxygen in the container was used. The chemical investigations have been carried out on freshly harvested material (we...
The aim of this paper was to study consumers' perception of three samples of soy-added beef h... more The aim of this paper was to study consumers' perception of three samples of soy-added beef hamburger in different percentages, using some helpful methods to capture consumers' perception sensory characteristics, such as free listing, check-all-that-apply (CATA) question and intensity scaling in order to determine the intensity of some sensorial characteristics (taste, odor, flavor and texture). For this purpose we prepared three samples of soy-added beef hamburger in different percentages (25%, 50% and 75% soy bean of total mass) and we study the effect of soy addition in beef hamburger on the sensory properties was studied.
In this paper we focus on the results of a study regarding the evaluation of the sensory characte... more In this paper we focus on the results of a study regarding the evaluation of the sensory characteristics and consumers’ acceptance of unsweetened yoghurt with carrot juice. The yoghurts were obtained considering three carrot juice levels (10%, 20% and 30%, respectively) and two starter cultures. Carrot yoghurt was prepared in the laboratory by adding carrot juice to milk and inoculated with a 3% yoghurt culture. The effects of the carrot juice on the sensory quality and consumers’ aceptance of the yoghurt samples were determined. The data obtained on various parameters were statistically analyzed.
This paper analyzes the total phenolic compounds and ascorbic acid in water, methanol extracts fr... more This paper analyzes the total phenolic compounds and ascorbic acid in water, methanol extracts from four selected wild fruits originally from the Bukovina area, namely, sea-buckthorn (Hippophaerhamnoides L), cranberry bush (Viburnum opulus L.), hawthorn (Crataegusmonogyna L.), and rosehip (Rosa Canina L.), used as tea beverages or as decoction for medicinal purposes. Ascorbic acid was separated, identified and dosed in fruit extracts by means of high-performance liquid chromatography (HPLC); the total phenolics were determined as gallic acid equivalents GAE/100 g FW, by the Folin-Ciocalteu method. The levels of berries mean ascorbic content in the four different families ranged from 112.87 (Viburnum opulus L) to 224.21 mg/kg of fresh weight (Crataegusmonogyna L.). The total phenolic content ranges from 4.38 mg GAE/kg FW (Hippophaerhamnoides L) to 11.09 mg GAE/kg FW (Crataegusmonogyna L.). These results suggest that the Crataegusmonogyna L. extract is a rich source of natural antioxi...
arXiv: Differential Geometry, 2018
In this paper, we study the existence of proper warped product submanifolds in metallic (or Golde... more In this paper, we study the existence of proper warped product submanifolds in metallic (or Golden) Riemannian manifolds and we discuss about semi-invariant, semi-slant and, respectively, hemi-slant warped product submanifolds in metallic and Golden Riemannian manifolds. Also, we provide some examples of warped product submanifolds in Euclidean spaces.
Revista de la Unión Matemática Argentina, 2017
Properties of metallic conjugate connections are stated by pointing out their relation to product... more Properties of metallic conjugate connections are stated by pointing out their relation to product conjugate connections. We define the analogous in metallic geometry of the structural and the virtual tensors from the almost product geometry and express the metallic conjugate connections in terms of these tensors. From an applied point of view we consider invariant distributions with respect to the metallic structure and for a natural pair of complementary distributions, the above structural and virtual tensors are expressed in terms of O'Neill–Gray tensor fields.
Journal of Function Spaces, 2018
The aim of our paper is to focus on some properties of slant and semi-slant submanifolds of metal... more The aim of our paper is to focus on some properties of slant and semi-slant submanifolds of metallic Riemannian manifolds. We give some characterizations for submanifolds to be slant or semi-slant submanifolds in metallic or Golden Riemannian manifolds and we obtain integrability conditions for the distributions involved in the semi-slant submanifolds of Riemannian manifolds endowed with metallic or Golden Riemannian structures. Examples of semi-slant submanifolds of the metallic and Golden Riemannian manifolds are given.
Journal of Function Spaces, 2018
The aim of our paper is to focus on some properties of slant and semi-slant submanifolds of metal... more The aim of our paper is to focus on some properties of slant and semi-slant submanifolds of metallic Riemannian manifolds. We give some characterizations for submanifolds to be slant or semi-slant submanifolds in metallic or Golden Riemannian manifolds and we obtain integrability conditions for the distributions involved in the semi-slant submanifolds of Riemannian manifolds endowed with metallic or Golden Riemannian structures. Examples of semi-slant submanifolds of the metallic and Golden Riemannian manifolds are given.
Novi Sad Journal of Mathematics, 2018
Properties of invariant, anti-invariant and slant isometrically immersed submanifolds of metallic... more Properties of invariant, anti-invariant and slant isometrically immersed submanifolds of metallic Riemannian manifolds are given with a special view towards the induced Σ-structure. Examples of such metallic manifolds are also given.
International Journal of Food Properties, 2016
The aim of this study was to determine the heavy metals (As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and ... more The aim of this study was to determine the heavy metals (As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) from honeys (acacia, sunflower, tilia, and polyfloral) from different counties (Suceava, Botosani, and Vaslui) of the northeast region of Romania. The data were analyzed using principal component analysis and linear discriminate analysis in order to achieve useful models for classification of honeys according to their botanical and geographical origin using the heavy metals content. The heavy metals content can be used as a suitable tool for the classification of honeys according to their botanical origin (80.8% were correctly classified), but not for the geographical origin (only 21.2% were correctly classified). None of the 10 heavy metals analyzed exceeded the maximum allowable level.
International Journal of Geometric Methods in Modern Physics, 2013
We define two classes of hypersurfaces in real space forms, golden- and product-shaped, respectiv... more We define two classes of hypersurfaces in real space forms, golden- and product-shaped, respectively, by imposing the shape operator to be of golden or product type. We obtain the whole families of above hypersurfaces, based on the classification of isoparametric hypersurfaces, as follows: in the golden case all are hyperspheres, a hyperbolic space and a generalized Clifford torus, while for the product case we obtain the unit hypersphere, the hyperplane, a hypersphere and its associated Clifford torus, respectively, according to the type of the ambient space form namely parabolic, hyperbolic or elliptic, respectively.
Differential Geometry-Dynamical Systems, 2006
Abstract. We study the properties of the composition of two Riemannian immersions of codimension ... more Abstract. We study the properties of the composition of two Riemannian immersions of codimension one. A Riemannian immersion is an isometric immersion between two Riemannian manifolds. First, we establish the Gauss and Weingarten formulae of the ...
Mathematics, 2021
In the present paper, we study some properties of warped product pointwise semi-slant and hemi-sl... more In the present paper, we study some properties of warped product pointwise semi-slant and hemi-slant submanifolds in Golden Riemannian manifolds, and we construct examples in Euclidean spaces. Additionally, we study some properties of proper warped product pointwise semi-slant (and, respectively, hemi-slant) submanifolds in a locally Golden Riemannian manifold.
Arxiv preprint math/0608533, 2006
We give some fundamental properties of the induced structures on submanifolds immersed in almost ... more We give some fundamental properties of the induced structures on submanifolds immersed in almost product or locally product Riemannian manifolds. We study the induced structure by the composition of two isometric immersions on submanifolds in an almost product Riemannian manifold. We give an effective construction for some induced structures on submanifolds of codimension 1 or 2 in Euclidean space.
Our aim in this paper is to give some examples of (a, 1)f Riemannian structures (a generalization... more Our aim in this paper is to give some examples of (a, 1)f Riemannian structures (a generalization of an r-paracontact structure) induced on product of spheres of codimension r (r ∈ {1, 2}) in an mdimensional Euclidean space (m > 2), endowed with an almost product structure.
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Papers by Cristina Hretcanu