133 research outputs found
A note on "A LP-based heuristic for a time-constrained routing problem"
In their paper, Avella et al. (2006) investigate a time-constrained routing problem. The core of the proposed solution approach is a large-scale linear program that grows both row- and column-wise when new variables are introduced. Thus, a column-and-row generation algorithm is proposed to solve this linear program optimally, and an optimality condition is presented to terminate the column-and-row generation algorithm. We demonstrate by using Lagrangian duality that this optimality condition is incorrect and may lead to a suboptimal solution at termination
A note on "A LP-based heuristic for a time-constrained routing problem"
Avella et al. (2006) [Avella, P., D'Auria, B., Salerno, S. (2006). A LP-based heuristic for a time-constrained routing problem. European Journal of Operational Research 173:120-124] investigate a time-constrained routing (TCR) problem. The core of the proposed solution approach is a large-scale linear program (LP) that grows both row- and column-wise when new variables are introduced. Thus, a column-and-row generation algorithm is proposed to solve this LP optimally, and an optimality condition is presented to terminate the column-and-row generation algorithm. We demonstrate that this optimality condition is incorrect and may lead to a suboptimal solution at termination. We identify the source of this error and discuss how the generic column-and-row generation algorithm proposed by Muter et al. (2010) may be applied to this TCR problem in order to solve the proposed large-scale LP correctly
Cognitive and emotional representations of terror attacks: A cross-cultural exploration
A questionnaire measuring cognitive and affective representations of terror risk was developed and tested in Turkey and Israel. Participants in the study were university students from the two countries (n = 351). Four equivalent factors explained terror risk cognitions in each sample: costs, vulnerability, trust, and control. A single negative emotionality factor explained the affective component of terror risk representations in both samples. All factors except control could be measured reliably. Results supported the validity of the questionnaire by showing expected associations between cognitions and emotions, as well as indicating gender differences and cultural variations. Current findings are discussed in relation to previous results, theoretical approaches, and practical implications. © 2007 Society for Risk Analysis
Cognitive-radio systems for spectrum, location, and environmental awareness
In order to perform reliable communications, a system needs to have sufficient information about its operational environment, such as spectral resources and propagation characteristics. Cognitive-radio technology has capabilities for acquiring accurate spectrum, location, and environmental information, due to its unique features such as spectrum, location, and environmental awareness. The goal of this paper is to give a comprehensive review of the implementation of these concepts. In addition, the dynamic nature of cognitive-radio systems - including dynamic spectrum utilization, transmission, the propagation channel, and reception - is discussed, along with performance limits, challenges, mitigation techniques, and open issues. The capabilities of cognitive-radio systems for accurate characterization of operational environments are emphasized. These are crucial for efficient communications, localization, and radar systems. © 2010 IEEE
Adaptation of two types of processing gains for UWB impulse radio wireless sensor networks
Ultrawideband impulse radio systems offer two kinds of processing gains that can be adapted based on the interference level in the system so that quality of service requirements are fulfilled. An adaptive assignment scheme for two types of multiple-access parameters in cluster-based wireless sensor networks is investigated. A mathematical framework is developed for asynchronous communications using a Gaussian approximation method to model the multiple-access interference in two cases: one with fixed frame duration, where the goal is to increase the average throughput, and the other with fixed symbol duration, where the goal is to increase the network lifetime. Extension of the analysis to multipath channels is carried out, and the validity of the Gaussian approximation is investigated using the Kullback-Leibler distance
Effects of cinnamon (Cinnamomum zeylanicum) bark oil on testicular antioxidant values, apoptotic germ cell and sperm quality
Cinnamon and its contents have multifactorial properties such as antioxidant,
anti-inflammatory and antidiabetic. Male infertility is one of the major health
problems in life. The aim of this study was to investigate the effects of longterm
cinnamon bark oil (CBO) ingestion on testicular antioxidant values,
apoptotic germ cell and sperm quality of adult rats. Twelve male healthy
Wistar rats were divided into two groups, each group containing six rats.
While olive oil was given to control group, 100 mg kg
1 CBO was administered
to the other group by gavage daily for 10 weeks. Body and reproductive
organ weights, sperm characteristics, testicular lipid peroxidation and antioxidant
enzyme activities, and testicular apoptosis via terminal deoxynucleotidyl
transferase–mediated dUTP nick end labelling (TUNEL) method were examined.
A significant decrease in malondialdehyde level and marked increases in
reduced glutathione level, glutathione peroxidase and catalase activities were
observed in rats treated with CBO compared with the control group. CBO
consumption provided a significant increase in weights of testes and epididymides,
epididymal sperm concentration, sperm motility and diameter of seminiferous
tubules when compared with the control group. However, CBO
consumption tended to decrease the abnormal sperm rate and apoptotic germ
cell count, but it did not reach statistical significance. It is concluded that CBO
has improvement effect on testicular oxidant–antioxidant balance and sperm
quality, and its consumption may be useful for asthenozoospermic men
Quercetin attenuates carbon tetrachloride-induced testicular damage in rats
This study was conducted to investigate the effect of quercetin on carbon tetrachloride
(CCl4)-induced sperm damages, testicular apoptosis and oxidative
stress in male rats. Group 1 served as control, group 2 was treated with only
quercetin, group 3 was treated with only CCl4 and group 4 received CCl4 +
quercetin. All administrations were performed by gavage and maintained for
10 weeks. CCl4 administration caused significant decreases in absolute and relative
reproductive organ weights, sperm motility, concentration and testicular
glutathione peroxidase (GSH-Px) and catalase (CAT) activities, and significant
increases in lipid peroxidation (LPO) level, abnormal sperm rate and testicular
apoptotic cell index, along with some histopathological damages when compared
to the control group. However, administration of CCl4 together with
quercetin provided statistically significant improvements in LPO level, abnormal
sperm rate, the degree of histopathological lesions and testicular apoptotic
cell index when compared to only CCl4 group. In addition, improvements
observed in absolute and relative weights of reproductive organs, sperm motility
and concentration, and testicular GSH-Px and CAT activities in group 4
were statistically insignificant when compared to only CCl4 group. In conclusion,
quercetin has antiperoxidative effect, and its oral administration attenuates
the CCl4-induced some damages in male reproductive organs and cells by
decreasing the LPO
Effectiveness of cinnamon (Cinnamomum zeylanicum) bark oil in the prevention of carbon tetrachloride-induced damages on male reproductive system
In this study, it was aimed to investigate the likelihood of detrimental effects
of carbon tetrachloride (CCl4) on male reproductive system through oxidative
stress mechanism and also protective effects of cinnamon bark oil (CBO). For
this purpose, 28 healthy male Wistar rats were divided into four groups, seven
rats in each. Group 1 received only olive oil daily; group 2 was treated with
100 mg kg
1 CBO daily; group 3 was treated with only 0.25 ml kg
1 CCl4
weekly; and group 4 received weekly CCl4 + daily CBO. All administrations
were made by intragastric catheter and maintained for 10 weeks. Body and
reproductive organ weights, sperm characteristics, testicular oxidative stress
markers and testicular apoptosis were examined. CCl4 administration caused
significant decreases in body and reproductive organ weights, testicular catalase
(CAT) activity, sperm motility and concentration, and significant increases in
lipid peroxidation (LPO) level, abnormal sperm rate and apoptotic index along
with some histopathological damages compared with the control group. However,
significant improvements were observed in absolute weights of testis and
epididymis, all sperm quality parameters, LPO level, apoptotic index and testicular
histopathological structure following the administration of CCl4 together
with CBO when compared to group given CCl4 only. The findings of this
study clearly suggest that CBO has protective effect against damages in male
reproductive organs and cells induced by CCl4
Effect of cinnamon (Cinnamomum zeylanicum) bark oil on heat stress-induced changes in sperm production, testicular lipid peroxidation, testicular apoptosis, and androgenic receptor density in developing Japanese quails
The aim of this study was to investigate the effect of cinnamon bark oil (CBO) on heat stress
(HS)-induced changes in sperm production, testicular lipid peroxidation, testicular apoptosis,
and androgenic receptor (AR) density in developing Japanese quails. Fifteen-day-old 90 male
chicks were assigned to two main groups. The first group (45 chicks) was kept in a thermoneutral
room at 22 C for 24 h/day. The second group (45 chicks) was kept in a roomwith high
ambient temperature at 34 C for 8 h/day (from9AM–5 PM) and at 22 C for 16 h/day. Each of
these two main groups was then divided into three subgroups (CBO groups 0, 250, 500 ppm)
consisting of 15 chicks (six treatment groups in 2 3 factorial order). Each of subgroups was
replicated for three times and each replicate included five chicks. Heat stress caused significant
decreases in body weight, spermatid and testicular sperm numbers, the density of testicular
Bcl-2 (antiapoptotic marker) and AR immunopositivity, and significant increases in testicular
lipid peroxidation level, the density of testicular Bax (apoptoticmarker) immunopositivity, and a
Bax/Bcl-2 ratio along with some histopathologic damages. However, 250 and 500 ppm CBO
supplementation provided significant improvements inHS-induced increased level of testicular
lipid peroxidation, decreased number of spermatid and testicular sperm, decreased densities of
Bcl-2 and AR immunopositivity, and some deteriorated testicular histopathologic lesions. In
addition, although HS did not significantly affect the testicular glutathione level, addition of both
250 and 500 ppm CBO to diet of quails reared in both HS and thermoneutral conditions caused a
significant increase when compared with quails without any consumption of CBO. In conclusion,
HS-induced lipid peroxidation causes testicular damage in developing male Japanese quails and,
consumption of CBO, which has antiperoxidative effect, protects their testes against HS
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