Progetto di un DLL ad aggancio multiplo per applicazioni in un time-to-digital converter ad alta risoluzione

Nei moderni sistemi elettronici, la capacità di trattare ed elaborare dati ad alta velocità è uno dei principali problemi che necessitano di essere risolti. Strumentazioni di misura e test, circuiti per le telecomunicazioni, militari o medicali sono solo alcuni esempi dei campi in cui l’uso di segnali di sincronia stabili e precisi, indipendenti da variazioni della temperatura o della tensione di alimentazione, è di fondamentale importanza per il raggiungimento di elevate prestazioni. Normalmente, in ognuna di queste applicazioni i riferimenti temporali devono avere un periodo di oscillazione spesso molto minore rispetto alla durata dell’impulso: ad esempio nei sistemi di ricezione che utilizzano oscillatori di tipo ring, la massima frequenza raggiungibile per il clock è di alcuni gigahertz e ciò implica che segnali che variano con una velocità maggiore non possono essere acquisiti correttamente. Per risolvere questo problema è possibile agire in due modi differenti: una prima soluzione consiste nell’impiego di tecnologie più performanti le quali, però, implicano spesso l’aumento dei costi di progettazione e realizzazione; una diversa soluzione, invece, è basata sull’uso di circuiti che moltiplicano il numero di fronti utili al campionamento. Il delay-locked-loop delay line (DLL) consente proprio di realizzare questa funzione. Il DLL è formato da una catena di celle a ritardo variabile, chiusa ad anello, in cui la differenza di fase fra il segnale in ingresso (il clock) e il segnale in uscita è nulla a regime; questo è possibile grazie alla presenza di un comparatore di fase che misura lo sfasamento delle tensioni ai due capi della catena e controlla, attraverso una apposita circuiteria, il ritardo delle celle. Le tensioni presenti all’uscita di ogni buffer possono essere utilizzate per campionare segnali di durata anche minore del periodo di clock. Le applicazioni che sfruttano il DLL sono molteplici, e vanno dai sistemi per il clock de-skewing ai convertitori tempo digitali ad alta velocità; in tutti questi casi, comunque, le prestazioni del sistema sono strettamente legate a quelle del DLL. Questo fatto rappresenta spesso un problema: infatti nel caso in cui la rotazione di fase dovuta alla linea di ritardo è pari a 2p, la distanza minima fra due fronti generati dal DLL è pari al minimo ritardo introdotto da ogni cella. Per aumentare la risoluzione del circuito è necessario, come sarà chiaro in seguito, aumentare il numero di celle, con un conseguente aumento dell’area totale del circuito, oppure aumentare la frequenza del clock e di conseguenza il consumo di potenza del circuito. Una soluzione a questi problemi può essere trovata nel fare in modo che la linea si agganci ad un numero di periodi maggiore di uno (metodo del “multiaggancio”). Come conseguenza, però, il DLL necessita, in questo caso, di una rete di controllo che consenta di acquisire e trattare i campioni in maniera corretta. Scopo di questa tesi è la progettazione di un DLL a shunt capacitor e della circuiteria necessaria affinché questo possa essere utilizzato come time-to-digital converter (TDC) con risoluzione dell’ordine della decina di picosecondi grazie all’impiego del metodo del “multiaggancio”. Dopo aver analizzato, nei primi due capitoli, i blocchi principali che costituiscono il DLL e le possibili realizzazioni presenti in letteratura di un TDC con linea di ritardo, passeremo all’analisi del principio di funzionamento del nuovo convertitore mettendo in evidenza quali sono le condizioni in cui la rete funziona correttamente e le implicazioni legate alla presenza di più periodi dell’oscillazione di riferimento all’interno della catena di buffer. Nel capitolo 4 sarà presentata la realizzazione degli inverter, delle capacità per il controllo digitale del ritardo e del comparatore di fase, riportando i dati sperimentali ottenuti dalle simulazioni al calcolatore. La linea è stata realizzata con un approccio full-custom sfruttando la tecnologia CMOS a 0.35 mm della AMS. Nel quinto capitolo si affronterà la realizzazione, con un criterio semicustom, della circuiteria di controllo del TDC, necessaria, come vedremo, per il corretto funzionamento del circuito. Anche in questo caso verranno riportate le simulazioni post-sintesi della rete. Infine, nel sesto e ultimo capitolo, saranno descritti i passi necessari per la realizzazione del layout finale del chip e sarà riportata un’ immagine del circuito ottenuto. Il progetto è stato svolto attraverso l’ambiente di programmazione CADENCE

Behavioral and biochemical evidence of the role of acetaldehyde in the motivational effects of ethanol

Since Chevens' report, in the early 50's, that his patients under treatment with the aldehyde dehydrogenase inhibitor, antabuse, could experience beneficial effects when drinking small volumes of alcoholic beverages, the role of acetaldehyde (ACD) in the effects of ethanol has been thoroughly investigated on pre-clinical grounds. Thus, after more than 25 years of intense research, a large number of studies have been published on the motivational properties of ACD itself as well as on the role that ethanol-derived ACD plays in the effects of ethanol. Accordingly, in particular with respect to the motivational properties of ethanol, these studies were developed following two main strategies: on one hand, were aimed to challenge the suggestion that also ACD may exert motivational properties on its own, while, on the other, with the aid of enzymatic manipulations or ACD inactivation, were aimed to test the hypothesis that ethanol-derived ACD might have a role in ethanol motivational effects. Furthermore, recent evidence significantly contributed to highlight, as possible mechanisms of action of ACD, its ability to commit either dopaminergic and opioidergic transmission as well as to activate the Extracellular signal Regulated Kinase cascade transduction pathway in reward-related brain structures. In conclusion, and despite the observation that ACD seems also to have inherited the elusive nature of its parent compound, the behavioral and biochemical evidence reviewed points to ACD as a neuroactive molecule able, on its own and as ethanol metabolite, to exert motivational effects

The renaissance of acetaldehyde as a psychoactive compound: decades in the making

As with many events in the history of science, the development of the hypothesis that acetaldehyde is a plausible psychoactive substance with specific central effects (not related to its toxic- ity) has not been either incremental or progressive. Rather, it has evolved through a process of fits and starts. Initial clinical obser- vations suggesting that accumulation of acetaldehyde could be used as a therapy for alcoholism did not lead to a highly effective treatment, and in fact, it was noted early on that small amounts of ethanol consumed under these conditions (i.e., blockade of aldehyde dehydrogenase) could be perceived as being even more pleasurable ( Chevens, 1953 ). Although some laboratory data in animals appeared at that time ( Carpenter and Macleod, 1952), it took a decade for the pre-clinical studies to focus on the poten- tial importance of acetaldehyde. Since Myers proposed in the late 60’s that acetaldehyde could be a mediator of some of the effects of ethanol ( Myers and Veale, 1969), advances in this field have gone through a push-pull process

From Ethanol to Salsolinol: Role of Ethanol Metabolites in the Effects of Ethanol

In spite of the global reputation of ethanol as the psychopharmacologically active ingredient of alcoholic drinks, the neurobiological basis of the central effects of ethanol still presents some dark sides due to a number of unanswered questions related to both its precise mechanism of action and its metabolism. Accordingly, ethanol represents the interesting example of a compound whose actions cannot be explained as simply due to the involvement of a single receptor/neurotransmitter, a scenario further complicated by the robust evidence that two main metabolites, acetaldehyde and salsolinol, exert many effects similar to those of their parent compound. The present review recapitulates, in a perspective manner, the major and most recent advances that in the last decades boosted a significant growth in the understanding on the role of ethanol metabolism, in particular, in the neurobiological basis of its central effects

The standardized Withania somnifera Dunal root extract alters basal and morphine-induced opioid receptor gene expression changes in neuroblastoma cells.

BACKGROUND: Behavioral studies demonstrated that the administration of Withania somnifera Dunal roots extract (WSE), prolongs morphine-elicited analgesia and reduces the development of tolerance to the morphine's analgesic effect; however, little is known about the underpinning molecular mechanism(s). In order to shed light on this issue in the present paper we explored whether WSE promotes alterations of \u3bc (MOP) and nociceptin (NOP) opioid receptors gene expression in neuroblastoma SH-SY5Y cells. METHODS: A range of WSE concentrations was preliminarily tested to evaluate their effects on cell viability. Subsequently, the effects of 5 h exposure to WSE (0.25, 0.50 and 1.00 mg/ml), applied alone and in combination with morphine or naloxone, on MOP and NOP mRNA levels were investigated. RESULTS: Data analysis revealed that morphine decreased MOP and NOP receptor gene expression, whereas naloxone elicited their up-regulation. In addition, pre-treatment with naloxone prevented the morphine-elicited gene expression alterations. Interestingly, WSE was able to: a) alter MOP but not NOP gene expression; b) counteract, at its highest concentration, morphine-induced MOP down-regulation, and c) hamper naloxone-induced MOP and NOP up-regulation. CONCLUSION: Present in-vitro data disclose novel evidence about the ability of WSE to influence MOP and NOP opioid receptors gene expression in SH-SY5Y cells. Moreover, our findings suggest that the in-vivo modulation of morphine-mediated analgesia by WSE could be related to the hindering of morphine-elicited opioid receptors down-regulation here observed following WSE pre-treatment at its highest concentration

Impact of Caffeine on Ethanol-Induced Stimulation and Sensitization: Changes in ERK and DARPP-32 Phosphorylation in Nucleus Accumbens

Background: Caffeine is frequently consumed with ethanol to reduce the impairing effects induced by ethanol, including psychomotor slowing or incoordination. Both drugs modulate dopamine (DA)-related markers in accumbens (Acb), and Acb DA is involved in voluntary locomotion and locomotor sensitization. The present study determined whether caffeine can affect locomotion induced by acute and repeated ethanol administration in adult male CD-1 mice. Methods: Acute administration of caffeine (7.5 to 30.0 mg/kg) was evaluated for its effects on acute ethanol-induced (1.5 to 3.5 g/kg) changes in open-field horizontal locomotion, supported rearing, and rearing not supported by the wall. DA receptor-dependent phosphorylation markers were assessed: extracellular signal-regulated kinase (pERK), and dopamine-and cAMP-regulated phosphoprotein Mr32kDa phosphorylated at threonine 75 site (pDARPP-32-Thr75) in Acb core and shell. Acutely administered caffeine was also evaluated in ethanol-sensitized (1.5 g/kg) mice. Results: Acute ethanol decreased both types of rearing. Caffeine increased supported rearing but did not block ethanol -induced decreases in rearing. Both substances increased horizontal locomotion in a biphasic manner, and caffeine potentiated ethanol-induced locomotion. Although ethanol administered repeatedly induced sensitization of locomotion and unsupported rearing, acute administration of caffeine to ethanol-sensitized mice in an ethanol-free state resulted in blunted stimulant effects compared with those seen in ethanol-naïve mice. Ethanol increased pERK immunoreactivity in both subregions of the Acb, but coadministration with caffeine blunted this increase. There were no effects on pDARPP-32(Thr75) immunoreactivity. Conclusions: The present results demonstrated that, after the first administration, caffeine potentiated the stimulating actions of ethanol, but did not counteract its suppressant or ataxic effects. Moreover, our results show that caffeine has less activating effects in ethanol-sensitized animals

Neuroprotective effect of (R)-(-)-linalool on oxidative stress in PC12 cells

Background: Oxidative stress plays an important role in neurodegeneration, pain and inflammation. (R)-(-)- linalool (LIN) is endowed with neuroprotective, anti-nociceptive and anti-inflammatory properties. Purpose: The present study aims at investigating the hypothesis that LIN’s neuroprotective, antinociceptive and anti-inflammatory properties descend from its ability to act as antioxidant. The study challenges this hypothesis by verifying whether LIN may counteract hydrogen peroxide (H 2 O 2 )-induced oxidative stress in PC12 cells. Methods: In H 2 O 2 -exposed PC12 cells, LIN was tested on a) cell viability, measured by 3-(4,5-dimethylthiazol-2- yl)-2,5-diphenyltetrazolium bromide (MTT), b) damage of plasma membrane, measured by lactate dehydrogenase (LDH) release, c) intracellular levels of reactive-oxygen-species (ROS), d) apoptosis and e) cell cycle distribution. Results: Under H 2 O 2 -induced cell viability reduction, LIN protects PC12 cells. Likewise, LIN protects cells from oxidative damage by preventing the H 2 O 2 -dependent increase of LDH release, counteracts intracellular ROS overproduction and reduces H 2 O 2 -induced apoptosis. Finally, the results of the cell cycle analysis from cells exposed to H 2 O 2 indicate that LIN incubation reduces the number of cells induced into quiescence by H 2 O 2 in the G2/M phase. Conclusions: These findings indicate that LIN protects PC12 cells from H 2 O 2 -induced oxidative stress. This mech- anism could justify the neuroprotective, anti-nociceptive and anti-inflammatory effects of this compound and suggest LIN as a potential therapeutic agent for the management oxidative stress-mediated pain

Advances in Sardinian Withania somnifera (L.) Dunal crops through phytochemical and biological approaches

Withania somnifera (L.) Dunal is widely used in the Indian traditional system of medicine to promote general health, wellness, and longevity. Its pharmacological properties are attributed to a group of molecules called withanolides, among which Withaferin A holds great interest for its anti-carcinogenic action. For this reason, numerous studies in recent years have focused on different metabolic or genetic engineering solutions to increase its yield. Here, we present the Sardinian chemotype of Withania somnifera as a potential crop for the extraction of Withaferin A. W. somnifera was cultivated from Sardinian wild germplasm collected in the northeast of the island. After 18 months, the leaves and the roots were collected and their methanolic extract was analyzed by HPLC. 0.3 mg/g DW of Withanolide A (WA), 1.0 mg/g DW of Withanolide B (WB) and 17.7 mg/g DW of Withaferin A (WF) were detected in the leaf sample, while lower values were detected in the roots (0.1 mg/g WF, 0.3 WA mg/g, 0.1 mg/g WB, 0.2 mg/g WO). This research not only confirms the high Withaferin A content found in the wild population leaves, but shows how they are reproducible in cultivated specimens, highlighting Sardinian W. somnifera leaves as a potential source of high-content Withaferin A products. Finally, we focused on the leaves extract by characterizing the phenolic and flavonoid content, as well as the in-vitro antioxidant capacity by DPPH and ABTS assays, revealing a significant amount of phenolic compounds and a related free radical scavenging activity. The leaves extract was further characterized for its anti-aging properties for potential cosmetic application, by the inhibition of tyrosinase, elastase, and collagenase enzymes

Ethanol-Dependent Synthesis of Salsolinol in the Posterior Ventral Tegmental Area as Key Mechanism of Ethanol’s Action on Mesolimbic Dopamine

Abnormal consumption of ethanol, the ingredient responsible for alcoholic drinks’ addictive liability, causes millions of deaths yearly. Ethanol’s addictive potential is triggered through activation, by a still unknown mechanism, of the mesolimbic dopamine (DA) system, part of a key motivation circuit, DA neurons in the posterior ventral tegmental area (pVTA) projecting to the ipsilateral nucleus accumbens shell (AcbSh). The present in vivo brain microdialysis study, in dually-implanted rats with one probe in the pVTA and another in the ipsilateral or contralateral AcbSh, demonstrates this mechanism. As a consequence of the oral administration of a pharmacologically relevant dose of ethanol, we simultaneously detect a) in the pVTA, a substance, 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol), untraceable under control conditions, product of condensation between DA and ethanol’s first by-product, acetaldehyde; and b) in the AcbSh, a significant increase of DA release. Moreover, such newly generated salsolinol in the pVTA is responsible for increasing AcbSh DA release via m opioid receptor (mOR) stimulation. In fact, inhibition of salsolinol’s generation in the pVTA or blockade of pVTA mORs prevents ethanol-increased ipsilateral, but not contralateral, AcbSh DA release. This evidence discloses the long-sought key mechanism of ethanol’s addictive potential and suggests the grounds for developing preventive and therapeutic strategies against abnormal consumption

Role of nucleus accumbens μ opioid receptors in the effects of morphine on ERK1/2 phosphorylation

Rationale: Despite the critical role attributed to phosphorylated extracellular signal regulated kinase (pERK1/2) in the nucleus accumbens (Acb) in the actions of addictive drugs, the effects of morphine on ERK1/2 phosphorylation in this area are still controversial. Objectives: In order to investigate further this issue, we studied (1) the ability of morphine to affect ERK1/2 phosphorylation in the shell (AcbSh) and core (AcbC) of Sprague-Dawley and Wistar rats and of CD-1 and C57BL/6J mice and (2) the role of dopamine D1 and μ-opioid receptors in Sprague-Dawley rats and CD-1 mice. Methods: The pERK1/2 expression was assessed by immunohistochemistry. Results: In rats, morphine decreased AcbSh and AcbC pERK1/2 expression, whereas in mice, increased it preferentially in the AcbSh compared with the AcbC. Systemic SCH 39166 decreased pERK1/2 expression on its own in the AcbSh and AcbC of Sprague-Dawley rats and CD-1 mice; furthermore, in rats, SCH 39166 disclosed the ability of morphine to stimulate pERK1/2 expression. Systemic (rats and mice) and intra-Acb (rats) naltrexone prevented both decreases, in rats, and increases, in mice. Conclusions: These findings confirm the differential effects of morphine in rats and mice Acb and that D1 receptors exert a facilitatory role on ERK1/2 phosphorylation; furthermore, they indicate that, in rats, removal of the D1-dependent pERK1/2 expression discloses the stimulatory influence of morphine on ERK1/2 phosphorylation and that the morphine’s ability to decrease pERK1/2 expression is mediated by Acb μ-opioid receptors. Future experiments may disentangle the psychopharmacological significance of the effects of morphine on pERK1/2 in the Acb