Signaling

Cell Communication and Signaling (CCS) is an open access journal that encompasses all basic and translational aspects of cellular communications and signaling pathways in normal and pathological conditions. The journal encourages submissions of original papers, review papers, short reports, and commentaries pertaining to both eukaryotic and prokaryotic intracellular and intercellular signal transduction, including but not limited to:

signaling

In contract theory, signalling (or signaling; see spelling differences) is the idea that one party (the agent) credibly conveys some information about itself to another party (the principal).

In Spence's job-market signaling model, (potential) employees send a signal about their ability level to the employer by acquiring education credentials. The informational value of the credential comes from the fact that the employer believes the credential is positively correlated with having the greater ability and difficulty for low ability employees to obtain. Thus the credential enables the employer to reliably distinguish low ability workers from high ability workers.[1] The concept of signaling is also applicable in competitive altruistic interaction, where the capacity of the receiving party is limited.[3]

Due to the nature of international relations and foreign policy, signaling has long been a topic of interest when analyzing the actions of the agents involved. This study of signaling regarding foreign policy has further allowed economists and academics to understand the actions and reactions of foreign bodies when presented with varying information. Typically when interacting with one another, the actions of these foreign parties are heavily dependent on the proposed actions and reactions of each other.[37] In many cases however, there is an asymmetry of information between the two parties with both looking to aid their own non-mutually beneficial interests.

Theoretically both sinking costs and tying hands are valid forms of costly signaling however they have garnered much criticism due to differing beliefs regarding the overall effectiveness of the methods in altering the likelihood of war. Recent studies such as the Journal of Conflict Resolution suggest that sinking costs and tying hands are both effective in increasing credibility. This was done by finding how the change in the costs of costly signals vary their credibility. Prior to this research studies conducted were binary and static by nature, limiting the capability of the model.[39] This increased the validity of the use of these signaling mechanisms in foreign diplomacy.

The initial research into signaling suggested that it was an effective tool in order to manage foreign economic and military affairs however, with time and more thorough analysis problems began to present themselves, these being:

Investigation into the mechanism of cytokine signaling led to the discovery of the JAK/STAT pathway. Following the binding of cytokines to their cognate receptor, signal transducers and activators of transcription (STATs) are activated by members of the janus activated kinase (JAK) family of tyrosine kinases. Once activated, they dimerize and translocate to the nucleus and modulate the expression of target genes. During the past several years significant progress has been made in the characterization of the JAK/STAT signaling cascade, including the identification of multiple STATs and regulatory proteins. Seven STATs have been identified in mammals. The vital role these STATs play in the biological response to cytokines has been demonstrated through the generation of murine 'knockout' models. These mice will be invaluable in carefully elucidating the role STATs play in regulating the host response to various stresses. Similarly, the solution of the crystal structure of two STATs has and will continue to facilitate our understanding of how STATs function. This review will highlight these exciting developments in JAK/STAT signaling.

Increases in the intracellular concentration of calcium ([Ca2+]i) activate various signaling pathways that lead to the expression of genes that are essential for dendritic development, neuronal survival, and synaptic plasticity. The mode of Ca2+ entry into a neuron plays a key role in determining which signaling pathways are activated and thus specifies the cellular response to Ca2+. Ca2+ influx through L-type voltage-activated channels (LTCs) is particularly effective at activating transcription factors such as CREB and MEF-2. We developed a functional knock-in technique to investigate the features of LTCs that specifically couple them to the signaling pathways that regulate gene expression. We found that an isoleucine-glutamine ("IQ") motif in the carboxyl terminus of the LTC that binds Ca2+-calmodulin (CaM) is critical for conveying the Ca2+ signal to the nucleus. Ca2+-CaM binding to the LTC was necessary for activation of the Ras/mitogen-activated protein kinase (MAPK) pathway, which conveys local Ca2+ signals from the mouth of the LTC to the nucleus. CaM functions as a local Ca2+ sensor at the mouth of the LTC that activates the MAPK pathway and leads to the stimulation of genes that are essential for neuronal survival and plasticity.

WebRTC allows real-time, peer-to-peer, media exchange between two devices. A connection is established through a discovery and negotiation process called signaling. This tutorial will guide you through building a two-way video-call.

WebRTC is a fully peer-to-peer technology for the real-time exchange of audio, video, and data, with one central caveat. A form of discovery and media format negotiation must take place, as discussed elsewhere, in order for two devices on different networks to locate one another. This process is called signaling and involves both devices connecting to a third, mutually agreed-upon server. Through this third server, the two devices can locate one another, and exchange negotiation messages.

Establishing a WebRTC connection between two devices requires the use of a signaling server to resolve how to connect them over the internet. A signaling server's job is to serve as an intermediary to let two peers find and establish a connection while minimizing exposure of potentially private information as much as possible. How do we create this server and how does the signaling process actually work?

First we need the signaling server itself. WebRTC doesn't specify a transport mechanism for the signaling information. You can use anything you like, from WebSocket to XMLHttpRequest to carrier pigeons to exchange the signaling information between the two peers.

It's important to note that the server doesn't need to understand or interpret the signaling data content. Although it's SDP, even this doesn't matter so much: the content of the message going through the signaling server is, in effect, a black box. What does matter is when the ICE subsystem instructs you to send signaling data to the other peer, you do so, and the other peer knows how to receive this information and deliver it to its own ICE subsystem. All you have to do is channel the information back and forth. The contents don't matter at all to the signaling server.

To allow the server to support signaling and ICE negotiation, we need to update the code. We'll have to allow directing messages to one specific user instead of broadcasting to all connected users, and ensure unrecognized message types are passed through and delivered, without the server needing to know what they are. This lets us send signaling messages using this same server, instead of needing a separate server.

As the existing code allows the sending of arbitrary message types, no additional changes are required. Our clients can now send messages of unknown types to any specific user, letting them send signaling messages back and forth as desired.

Now that we've built a mechanism for exchanging messages, we need a protocol defining how those messages will look. This can be done in a number of ways; what's demonstrated here is just one possible way to structure signaling messages.

This example's server uses stringified JSON objects to communicate with its clients. This means our signaling messages will be in JSON format, with contents which specify what kind of messages they are as well as any additional information needed in order to handle the messages properly.

When starting the signaling process, an offer is created by the user initiating the call. This offer includes a session description, in SDP format, and needs to be delivered to the receiving user, which we'll call the callee. The callee responds to the offer with an answer message, also containing an SDP description. Our signaling server will use WebSocket to transmit offer messages with the type "video-offer", and answer messages with the type "video-answer". These messages have the following fields:

The SDP candidate string, describing the proposed connection method. You typically don't need to look at the contents of this string. All your code needs to do is route it through to the remote peer using the signaling server.

Note: The important thing to note is this: the only thing your code is responsible for during ICE negotiation is accepting outgoing candidates from the ICE layer and sending them across the signaling connection to the other peer when your onicecandidate handler is executed, and receiving ICE candidate messages from the signaling server (when the "new-ice-candidate" message is received) and delivering them to your ICE layer by calling RTCPeerConnection.addIceCandidate(). That's it.

Note: The onicecandidate Event and createAnswer() Promise are both async calls which are handled separately. Be sure that your signaling does not change order! For example addIceCandidate() with the server's ice candidates must be called after setting the answer with setRemoteDescription(). 041b061a72