426 research outputs found
Stability of cylindrical thin shell wormhole during evolution of universe from inflation to late time acceleration
In this paper, we consider the stability of cylindrical wormholes during
evolution of universe from inflation to late time acceleration epochs. We show
that there are two types of cylindrical wormholes. The first type is produced
at the corresponding point where k black F-strings are transited to BIon
configuration. This wormhole transfers energy from extra dimensions into our
universe, causes inflation, loses it's energy and vanishes. The second type of
cylindrical wormhole is created by a tachyonic potential and causes a new phase
of acceleration. We show that wormhole parameters grow faster than the scale
factor in this era, overtake it at ripping time and lead to the destruction of
universe at big rip singularity.Comment: 18 pages, 6 figures.v2, accepted in JHE
Electrophysiological characteristics of cationic single-channel formed by incorporation of amphotericin b in bilayer lipid membrane
BACKGROUND AND OBJECTIVE: Amphotericin B (AmB) is the main antibiotic of polyene type, which is widely used in the treatment of systemic fungal infections. One of the key mechanisms of this drug is the formation of ion channels and increasing permeability of the host cell membranes. This study was conducted to evaluate some of the electrophysiological characteristics of cationic single-channel formed by the incorporation of AmB in bilayer lipid membrane (BLM). METHODS: In this experimental study, phosphatidyl choline was extracted from fresh egg yolk. After the formation of BLM and the incorporation of AmB in the membrane, the channel activity was recorded through +40 to -40 millivolt (mV) voltages. Data analysis was conducted using PClamp10 software to determine the electrophysiological characteristics of the channel. FINDINGS: Reverse potential of Amphotericin B ion Channel was-36 mV. The Channel activity was more in such positive voltages. This means that in voltage -40 mV the current amplitude was 2 Pico Ampère but in voltage +40 mV reach to 30 Pico Ampère. In addition, the channel open probability at voltage -30 mV voltage was low (less than 0.15) but increased to 0.75 in voltage +40 mV. The channel conductance was also 157±4.9 Picoseimence. CONCLUSION: AmB forms cationic channels in BLMs with phosphatidylcholine and without cholesterol. This channel has voltage-dependent electrophysiological characteristics and behaviors. © 2016, Babol University of Medical Sciences. All rights reserved
Quercetin improved spatial memory dysfunctions in rat model of intracerebroventricular streptozotocin-induced sporadic Alzheimer’sdisease
Background: Alzheimer’s disease (AD) is one of the most common neurodegenerative syndromes characterized by a progressive decline in the spatial memory. There are convincing evidences on the neuroprotective effects of flavonoids against AD. Aims and Objective: To determine the effect of quercetin on the acquisition and retention of spatial memory in a rat model of AD. Materials and Methods: Twenty-four male Wistar rats were divided into four groups (six in each): group I: control rats receiving intracerebroventricular (ICV) injection of normal saline, group II: rats induced AD by ICV injection of streptozotocin (STZ; 3 mg/kg bilaterally; twice, on days 1 and 3), and groups III and IV: ICV-STZ AD rats treated intraperitoneally (IP) with 40 and 80 mg/kg/day quercetin, respectively, over a period of 12 days. Then, the rats were trained with four trials per day for five consecutive days in the Morris water maze (MWM). On the sixth day, the memory retention was evaluated. Result: The ICV-STZ AD groups showed a significant impairment in the acquisition and retrieval of spatial memory when compared with the control group (P < 0.001). In the AD groups, the escape latency during the training trials showed a significant decrease (P < 0.001). Meanwhile, during the MWM task, theseratsspentmoretimeinthetargetquadrant in probe trials when compared with the controls. Conclusion: Quercetin acted as a spatial memory enhancer in ICV-STZ–induced AD rats. Hence, this flavonoid can be considered potentially as a promising agent for developing prophylactic and therapeutic neuroprotection. This neuroprotective effect of quercetin may be attributed to its antioxidant and scavenging properties. © 2015 Hamid Sepehri
Constructing warm inflationary model in brane-antibrane system
Recently, various observational data predict a possibility that inflation may
naturally occur in a warm region. In this scenario, radiation is produced
during the inflation epoch and reheating is avoided. The main question arises
that what is the origin of warm inflation in 4D universe? We answer to this
question in brane-antibrane system. We propose a model that allows all
cosmological parameters like the scale factor a, the Hubble parameter H and
phantom energy density depend on the equation of state parameter in transverse
dimension between two branes. Thus, an enhancement in these parameters can be a
signature of some evolutions in extra dimension. In our model, the expansion of
4D universe is controlled by the separation distance between branes and evolves
from non-phantom phase to phantom one. Consequently, phantom-dominated era of
the universe accelerates and ends up in big-rip singularity. Also, we show that
as the tachyon potential increases, the effect of interaction between branes on
the 4D universe expansion becomes systematically more effective, because at
higher energies there exists more channels for flowing energy from extra
dimension to other four dimensions. Finally, we test our model against WMAP and
Planck data and obtain the ripping time. According to experimental data,
case leads to , where \emph{N} and are
the number e-folds and the spectral index respectively. This standard case may
be found in , where is
the tensor-scalar ratio. At this point, the finite time that Big Rip
singularity occurs is .Comment: 16 pages, 3 figures, Accepted in Phys. Lett. B. arXiv admin note:
text overlap with arXiv:0708.3233 by other author
Efficient and Secure Data Sharing Using Attribute-based Cryptography
La crescita incontrollata di dati prodotti da molte sorgenti, eterogenee e di-
namiche, spinge molti possessori di tali dati a immagazzinarli su server nel cloud,
anche al fine di condividerli con terze parti. La condivisione di dati su server
(possibilmente) non fidati fonte di importanti e non banali questioni riguardanti
sicurezza, privacy, confidenzialit e controllo degli accessi. Al fine di prevenire
accessi incontrollati ai dati, una tipica soluzione consiste nel cifrare i dati stessi.
Seguendo tale strada, la progettazione e la realizzazione di politiche di accesso
ai dati cifrati da parte di terze parti (che possono avere differenti diritti sui
dati stessi) un compito complesso, che impone la presenza di un controllore
fidato delle politiche. Una possibile soluzione l\u2019impiego di un meccanismo per
il controllo degli accessi basato su schemi di cifratura attribute-base (ABE ),
che permette al possessore dei dati di cifrare i dati in funzione delle politiche
di accesso dei dati stessi. Di contro, l\u2019adozione di tali meccanismi di controllo
degli accessi presentano due problemi (i) privacy debole: le politiche di accesso
sono pubbliche e (ii) inefficienza: le politiche di accesso sono statiche e una loro
modifica richiede la ricifratura (o la cifratura multipla) di tutti i dati. Al fine
di porre rimedio a tali problemi, il lavoro proposto in questa tesi prende in con-
siderazione un particolare schema di cifratura attribute-based, chiamato inner
product encryption (IPE, che gode della propriet attribute-hiding e pertanto
riesce a proteggere la privatezza delle politiche di accesso) e lo combina con
le tecniche di proxy re-encryption, che introducono una maggiore flessibilit ed
efficienza.
La prima parte di questa tesi discute l\u2019adeguatezza dell\u2019introduzione di un
meccanismo di controllo degli accessi fondato su schema basato su inner product
e proxy re-encryption (IPPRE ) al fine di garantire la condivisione sicura di dati
immagazzinati su cloud server non fidati. Pi specificamente, proponiamo due
proponiamo due versioni di IPE : in prima istanza, presentiamo una versione es-
tesa con proxy re-encryption di un noto schema basato su inner product [1]. In
seguito, usiamo tale schema in uno scenario in cui vengono raccolti e gestiti dati
medici. In tale scenario, una volta che i dati sono stati raccolti, le politiche di ac-
cesso possono variare al variare delle necessit dei diversi staff medici. Lo schema
proposto delega il compito della ricifratura dei dati a un server proxy parzial-
mente fidato, che pu trasformare la cifratura dei dati (che dipende da una polit-
ica di accesso) in un\u2019altra cifratura (che dipende da un\u2019altra politica di accesso)
senza per questo avere accesso ai dati in chiaro o alla chiave segreta utilizzata
dal possessore dei dati. In tal modo, il possessore di una chiave di decifratura
corrispondente alla seconda politica di accesso pu accedere ai dati senza intera-
gire con il possessore dei dati (richiedendo cio una chiave di decifratura associata
alla propria politica di accesso). Presentiamo un\u2019analisi relativa alle prestazioni
di tale schema implementato su curve ellittiche appartenenti alle classi SS, MNT
e BN e otteniamo incoraggianti risultati sperimentali. Dimostriamo inoltre che
lo schema proposto sicuro contro attacchi chosen plaintext sotto la nota ipotesi
DLIN. In seconda istanza, presentiamo una versione ottimizzata dello schema
proposto in precedenza (E-IPPRE ), basata su un ben noto schema basato suinner product, proposto da Kim [2]. Lo schema E-IPPRE proposto richiede un
numero costante di operazioni di calcolo di pairing e ci garantisce che gli oggetti
prodotti dall esecuzione dello schema (chiavi di decifratura, chiavi pubbliche
e le cifrature stesse) sono di piccole rispetto ai parametri di sicurezza e sono
efficientemente calcolabili. Testiamo sperimentalmente l\u2019efficienza dello schema
proposto e lo proviamo (selettivamente nei confronti degli attributi) sicuro nei
confronti di attacchi chosen plaintext sotto la nota ipotesi BDH. In altri termini,
lo schema proposto non rivela alcuna informazione riguardante le politiche di
accesso.
La seconda parte di questa tesi presenta uno schema crittografico per la
condivisione sicura dei dati basato su crittografia attribute-based e adatto per
scenari basati su IoT. Come noto, il problema principale in tale ambito riguarda
le limitate risorse computazionali dei device IoT coinvolti. A tal proposito,
proponiamo uno schema che combina la flessibilit di E-IPPRE con l\u2019efficienza
di uno schema di cifratura simmetrico quale AES, ottenendo uno schema di
cifratura basato su inner product, proxy-based leggero (L-IPPRE ). I risultati
sperimentali confermano l\u2019adeguatezza di tale schema in scenari IoT.Riferimenti
[1] Jong Hwan Park. Inner-product encryption under standard assumptions.
Des. Codes Cryptography, 58(3):235\u2013257, March 2011.
[2] Intae Kim, Seong Oun Hwang, Jong Hwan Park, and Chanil Park. An effi-
cient predicate encryption with constant pairing computations and minimum
costs. IEEE Trans. Comput., 65(10):2947\u20132958, October 2016.With the ever-growing production of data coming from multiple, scattered, and
highly dynamical sources, many providers are motivated to upload their data
to the cloud servers and share them with other persons for different purposes.
However, storing data on untrusted cloud servers imposes serious concerns in
terms of security, privacy, data confidentiality, and access control. In order to
prevent privacy and security breaches, it is vital that data is encrypted first
before it is outsourced to the cloud. However, designing access control mod-
els that enable different users to have various access rights to the shared data
is the main challenge. To tackle this issue, a possible solution is to employ
a cryptographic-based data access control mechanism such as attribute-based
encryption (ABE ) scheme, which enables a data owner to take full control over
data access. However, access control mechanisms based on ABE raise two chal-
lenges: (i) weak privacy: they do not conceal the attributes associated with the
ciphertexts, and therefore they do not satisfy attribute-hiding security, and (ii)
inefficiency: they do not support efficient access policy change when data is
required to be shared among multiple users with different access policies. To
address these issues, this thesis studies and enhances inner-product encryption
(IPE ), a type of public-key cryptosystem, which supports the attribute-hiding
property as well as the flexible fine-grained access control based payload-hiding
property, and combines it with an advanced cryptographic technique known as
proxy re-encryption (PRE ).
The first part of this thesis discusses the necessity of applying the inner-
product proxy re-encryption (IPPRE ) scheme to guarantee secure data sharing
on untrusted cloud servers. More specifically, we propose two extended schemes
of IPE : in the first extended scheme, we propose an inner-product proxy re-
encryption (IPPRE ) protocol derived from a well-known inner-product encryp-
tion scheme [1]. We deploy this technique in the healthcare scenario where data,
collected by medical devices according to some access policy, has to be changed
afterwards for sharing with other medical staffs. The proposed scheme delegates
the re-encryption capability to a semi-trusted proxy who can transform a dele-
gator\u2019s ciphertext associated with an attribute vector to a new ciphertext associ-
ated with delegatee\u2019s attribute vector set, without knowing the underlying data
and private key. Our proposed policy updating scheme enables the delegatee to
decrypt the shared data with its own key without requesting a new decryption
key. We analyze the proposed protocol in terms of its performance on three dif-
ferent types of elliptic curves such as the SS curve, the MNT curve, and the BN
curve, respectively. Hereby, we achieve some encouraging experimental results.
We show that our scheme is adaptive attribute-secure against chosen-plaintext
under standard Decisional Linear (D-Linear ) assumption. To improve the per-
formance of this scheme in terms of storage, communication, and computation
costs, we propose an efficient inner-product proxy re-encryption (E-IPPRE )
scheme using the transformation of Kim\u2019s inner-product encryption method [2].
The proposed E-IPPRE scheme requires constant pairing operations for its al-
gorithms and ensures a short size of the public key, private key, and ciphertext,making it the most efficient and practical compared to state of the art schemes
in terms of computation and communication overhead. We experimentally as-
sess the efficiency of our protocol and show that it is selective attribute-secure
against chosen-plaintext attacks in the standard model under Asymmetric De-
cisional Bilinear Diffie-Hellman assumption. Specifically, our proposed schemes
do not reveal any information about the data owner\u2019s access policy to not only
the untrusted servers (e.g, cloud and proxy) but also to the other users.
The second part of this thesis presents a new lightweight secure data sharing
scheme based on attribute-based cryptography for a specific IoT -based health-
care application. To achieve secure data sharing on IoT devices while preserving
data confidentiality, the IoT devices encrypt data before it is outsourced to the
cloud and authorized users, who have corresponding decryption keys, can ac-
cess the data. The main challenge, in this case, is on the one hand that IoT
devices are resource-constrained in terms of energy, CPU, and memory. On the
other hand, the existing public-key encryption mechanisms (e.g., ABE ) require
expensive computation. We address this issue by combining the flexibility and
expressiveness of the proposed E-IPPRE scheme with the efficiency of symmet-
ric key encryption technique (AES ) and propose a light inner-product proxy
re-encryption (L-IPPRE ) scheme to guarantee secure data sharing between dif-
ferent entities in the IoT environment. The experimental results confirm that
the proposed L-IPPRE scheme is suitable for resource-constrained IoT scenar-
ios.References
[1] Jong Hwan Park. Inner-product encryption under standard assumptions.
Des. Codes Cryptography, 58(3):235\u2013257, March 2011.
[2] Intae Kim, Seong Oun Hwang, Jong Hwan Park, and Chanil Park. An effi-
cient predicate encryption with constant pairing computations and minimum
costs. IEEE Trans. Comput., 65(10):2947\u20132958, October 2016
Comparison of psychosexual problems between substance dependence patients
زمینه و هدف: نارضایتی جنسی یکی از مشکلات شایع در بیماران وابسته به مواد مخدر به شمار می آید. این مطالعه با هدف بررسی مقایسه ای ابعاد روانشناختی مشکلات جنسی در مردان متاهل و مصرف کننده کراک، شیشه و تریاک و مقایسه گروه ها با افراد غیر مصرف کننده انجام شده است. روش بررسی: در این مطالعه توصیفی- تحلیلی، تعداد 56 نفر بیمار مرد مراجعه کننده به مرکز ترک اعتیاد، به صورت نمونه گیری در دسترس در قالب چهار گروه قرار گرفتند. گروه های نمونه شامل (20 نفر تریاک، 18 نفر کراک و 18 نفر شیشه) و یک گروه شاهد (20 نفر) بودند. آزمودنی ها اقدام به تکمیل پرسشنامه چند وجهی مسایل جنسی نمودند. یافته ها: از بین خرده مقیاس های آزمون، تفاوت معناداری در میانگین نمرات سه گروه مصرف کننده با یکدیگر و نیز با گروه شاهد در خرده مقیاسهای اشتغال ذهن جنسی، انگیزش جنسی، اضطراب جنسی، قاطعیت جنسی، افسردگی جنسی، کنترل جنسی بیرونی، نظارت جنسی، ترس از رابطهی جنسی و رضایت جنسی مشاهده شد (05/0>P). تفاوت بین گروه شیشه و کراک / تریاک و شیشه در خرده مقیاسهای اشتغال ذهن جنسی، انگیزش جنسی، اضطراب جنسی، افسردگی جنسی، کنترل جنسی بیرونی، نظارت جنسی، ترس از رابطهی جنسی و رضایت جنسی معنادار بوده است (01/0
Study of prophenoloxidase activating system of freshwater crayfish (Pontastacus leptodactylus)
Phenoloxidase (Po) activity was measusred spectrophotometrically in serum, plasma and haemocytes (HLS) of the freshwater crayfish (Pontastacus leptodactylus). The highest activity was found in HLS suggesting that the haemocytes are the major source of the Po or its proform prophenoloxidase (proPO) in crayfish. Furthermore, the enzyme activity in serum samples was reduced after freezing the samples for 20 days at -20˚C. Po activity was cation-dependent and the peak of enzyme activity obtained using 5mM of CaCl2 or MgCl2 .Also, the Po activity in the HLS samples treated with different elicitors of 10% sodium dodecyl sulphate (10%SDS), b 1-3-glucan, Aeromonas hydrophila lipopolysaccharids (LPS) and trypsin resulted in variable activities with the highest and the lowest activities measured in samples treated with trypsin and 10% SDS, respectively. The marked enhancement induced by trypsin suggests the role of an endogenous proteinase which is probably able to promote the enzyme activity. To confirm the role of the proteinase on the proPO activating system, trypsin activity was also measured in the crayfish HLS
Modulation of the hepatocyte rough endoplasmic reticulum single chloride channel by nucleotide-Mg 2+ interaction
The effect of nucleotides on single chloride channels derived from rat hepatocyte rough endoplasmic reticulum vesicles incorporated into bilayer lipid membrane was investigated. The single chloride channel currents were measured in 200/50 mmol/l KCl cis/trans solutions. Adding 2.5 mM adenosine triphosphate (ATP) and adenosine diphosphate (ADP) did not influence channel activity. However, MgATP addition inhibited the chloride channels by decreasing the channel open probability (Po) and current amplitude, whereas mixture of Mg 2+ and ADP activated the chloride channel by increasing the Po and unitary current amplitude. According to the results, there is a novel regulation mechanism for rough endoplasmic reticulum (RER) Cl - channel activity by intracellular MgATP and mixture of Mg 2+ and ADP that would result in significant inhibition by MgATP and activation by mixture of Mg 2+ and ADP. These modulatory effects of nucleotide-Mg 2+ complexes on chloride channels may be dependent on their chemical structure configuration. It seems that Mg-nucleotide-ion channel interactions are involved to produce a regulatory response for RER chloride channels. © Springer-Verlag 2012
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