What Is The Difference Between Accuracy And Precision in Chemistry?

What Is The Difference Between Accuracy And Precision in Chemistry?In chemistry, there is the difference between accuracy and precision. This difference is important because both can cause you to perform incorrect analyses of samples. The correct analysis requires a chemist to do their best, but a mistake can often lead to bad science.The issue is that many chemists may be too concerned with accuracy. With precision, they are able to get to work on samples quickly. They will also make more mistakes, which increases the chance that they will be caught. This leads to an inaccurate assessment of the nature of the sample.So, what is the difference between accuracy and precision? The answer lies in the fact that accuracy involves a whole system. It includes the accuracy of your work and your ability to implement the correct procedures. Precision involves different things such as setting up a proper sample analysis to get the measurements.If you have these two errors, then you will not be able to be an accurate scientist. Either of these can lead to the missing of a few relevant elements. The improper analysis of the sample can lead to the missing of a material that you were trying to detect.So it is not the case that you can work with precision. The problem comes from not making the necessary corrections when you are doing your calculations. This means that in this field, accuracy is not enough to ensure that you have a good test, but it is also important that you are taking proper measurements.With accuracy, you are more likely to get things right. With precision, you are less likely to get the measurement right, but it is the case that you will still get it right.These differences help explain why precision is more important than accuracy in chemistry. You need both accuracy and precision to be successful in your career.

Powerless or Powerful at Work. Its your choice. - Introvert Whisperer

Introvert Whisperer / Powerless or Powerful at Work. It’s your choice. - Introvert Whisperer Powerless or Powerful at Work. It’s your choice. I’m sure we all have experienced the moment when a co-worker (and maybe you as well) has been negatively impacted by decisions management has made. You might be very concerned the most for your friend.   Yet, you feel you should do something because of just how unfair the issue is or how serious the impact is.   But, you feel powerless to do anything. Many times things happen at work that negatively impacts us or those we work with.   We can feel powerless and out of control about a situation.   We feel victimized and frustrated because of this sense of powerlessness or we feel that for our co-worker/friends. What should you do? First, you can’t go fight for your friend.   You can help them, counsel with them but any actions done on behalf of your friend; need to be done by them.   Otherwise, you are going to muddy up the situation and if it’s already bad, making things worse isn’t helpful. Be a role model of what to do.   In other words, you can empower you to take whatever actions you need to do to help improve the situation.   Your co-workers can also do the same.   Remember, your parents couldn’t go fight your fights when you were a kid and the same thing applies now. Many people think when it comes to “management” that they are powerless to do anything but that’s simply not true.   We are more powerful than we realize and we don’t have to turn into a jerk to be that way.   Management is people like you and wants the same things out of life and career.   Also like you, they don’t always know everything they need to know about decisions they make including the impact to you.   You see, people are the single biggest resource any business has.   Without you and others, there would be no business.   That means you have to communicate with management.   They need to understand the implications and you can’t assume they always know. At the same time, you also have to understand that management has more information on the business and takes a broader view than you do.   It’s their job and with it may come unpopular decisions born out by conditions you know nothing about.   You may never know the entire scope of information that goes into any given decision.   That means that while a decision might be made that negatively impacts you or others, you do have to place a certain amount of trust that management is making the best decisions they can.   Nevertheless, it doesn’t mean you shouldn’t share your concerns because those concerns might not have been considered. You have to also keep in mind that even if you voice your concerns that the best you can hope for is for management to listen.   It may not change anything but they will gain insight from you stepping forward.   It’s okay to hope it influences change. You may not be comfortable being assertive like I’m suggesting.   I know many people aren’t but it’s like this:   Which is worse? The discomfort of feeling powerless and victimized or the discomfort of stepping forward? Go to top Do you know what your next career step is?  Many people don’t. I want to help you accelerate your career by connecting you with your Free Instant Access to my eBook on how to construct your Career SMART Goals â€" that will help you put together your actions and keep you accountable. Get your copy now and start your action plan today! Brought to you by Dorothy Tannahill-Moran â€" dedicated to unleashing your professional potential. Introvert Whisperer

English Expressions with Speak and Speech - Intermediate Level English

English Expressions with Speak and Speech - Intermediate Level English In this post I would like to review the topic of speech and in particular English expressions with speak and speech.I was raised to believe that  freedom of speech is one of the cornerstones  (something of great importance)  of society.  However,  as I get older my belief is challenged time and time again.  Now I understand that in reality I have the right to freedom of speech  provided that I generally agree with what the general population now accepts. Unfortunately,  this is not my view of freedom.The following are English words and phrases connected with speech  and hopefully you will find something useful for you. English Expressions with Speak and Speech Going back to my earlier point we all have the right to  SPEAK OUR MIND (to say what we feel)  provided we do so with respect to other people’s feelings and beliefs. When we were young we were advised by teachers,  trainers and parents to learn to SPEAK UP FOR YOURSELF (  not to be afraid to put your hand up and give an opinion or view or simply get involved).  Alternatively,  if you were not able to speak up for yourself you tried to get someone  to SPEAK ON YOUR BEHALF  (someone to say what you want to say but cannot).There are many phrases and expressions connected with speech.  The following are the key and important expressions with examples.SPEAK CLEARLYEveryone can speak but not many speak clearly,  pronounce words  in a way that makes it clear to the listener exactly what you are saying. Some mumble (speak very quietly under their breath) and we have to ask them to PLEASE, SPEAK UP  (to raise their voice a little so that we can hear what they have said)  some SPEAK TOO QUI CKLY  (so quick that we have to ask the person to slow down or repeat what they have said). Some even speak so slow  that we are tempted to finish the sentence for them!Parents, grandparents and teachers are often heard to correct the tone and language of young people by chastising them  (complaining and correcting them)  when they speak perhaps rudely to them. DON’T SPEAK TO ANYONE LIKE THAT!!  (speak more mannerly) English Expressions with Speak - Infographic Enjoyed this infographic? Here's what you can do next: Collocations with Speak SPEAK THE TRUTHHow many times did you hear this as a kid. Don’t lie always tell the truth. (Of course,  when  we grow older it is not always the best policy.)Example: I believe if you want to be heard, you need to speak the truth.WELL SPOKENWe consider someone to be well spoken when the speak clearly, concisely and in an assured fashion. They do not have to raise their voice  (shout or scream), they do not use too many words but speak with authority and knowledge in an understandable way.Example: He is a very well spoken man he has a lot of life experience.SPEAK OUTIf we feel strongly about a topic we are often encouraged to speak out about it. This means to make ourselves heard.Example: Recently the “Me too” movement has raised the issue of women and sexual exploitation particularly in the movie and entertainment industries. Women have spoken out about their experiences and feelings.ACTIONS SPEAK LOUDER THAN WORDSEveryone can talk and tell you what they will or will not do but doing something is often seen as more productive. What somebody does is more important than what they say.Example: Don’t tell Auntie Paula that you miss her, just go and visit her. Actions speak louder than words! Collocations with Speak SPEAK OF THE DEVILWhen someone we are thinking of or talking about suddenly and unexpectedly appears then we can say ‘ah speak of the devil!’Example: You are discussing your friend David with another friend Susan. You are talking about something funny or interesting he did recently when you suddenly see him approaching you in the coffee shop. ‘Ah David, speak of the devil, we were just talking about you.’THINK BEFORE YOU SPEAKA great piece of advice at any age. We often speak our minds  but occasionally it might not sound the way we intended and someone might get offended  (be upset or hurt) so it is always a good idea to think before you speak.SPEAK WHEN YOU ARE SPOKEN TOAnother reminder of my childhood. How often did your  mother or father say this? It means that someone is only allowed to say something when they are asked for an opinion.Example: Speak when you are spoken to and not until!!SPEAK FOR YOURSELFThis is a way of reminding people that they are only expressing the ir own opinion and that other people might think differently.Example: ‘This year’s test was really easy.’ ‘Speak for yourself! I thought it was really difficult.’I have a much more relaxed attitude to communication these days and always encourage my younger students to express themselves in a calm and clear manner. Words can be easily misinterpreted so speaking clearly but never be afraid to speak.

New Tutor Spotlight - Sam

New Tutor Spotlight - Sam Improving Academic Performance MyGuru is proud to announce that Sam Ribnick has joined its elite team of private tutors in Boston, MA. Sam is also a capable of providing online tutoring in Math, Physics, and the ACT and/or SAT. Sam holds a BS in Physics from MIT, and currently teaches high school physics in Boston Public Schools. His classes have outperformed on standardized tests, with a 90% passing rate vs. a 70% passing rate prior to his start date. At MIT, he tutored students in physics and various math subjects. He’s worked as a recitation instructor leading a section of multi-variable calculus. For 3 summers at the Center for Talent Development at Northwestern University, he was the TA for summer physics classes for gifted high school students. He has tutored students from many colleges around Boston and has a strong background in physics, chemistry, biology and all math subjects (algebra, geometry, trigonometry, calculus, etc). Furthermore, Sam has experience in the business world, having worked for the prestigious Boston Consulting Group after MIT and before returning to the world of education to become a high school physics teacher. Sam is a great example of the tutors we work with at MyGuru.

4 Things Every High School Freshman Should Do Now

4 Things Every High School Freshman Should Do Now Fullerton Tutoring Tips: 4 things every high school freshman should do now High School freshmen have survived the first half of the school year and are enjoying a couple of weeks off during winter break. Hopefully, they have settled into the responsibilities that being a high school student require and are getting used to the new workload in each class. Each student will have an individual experience and their adjustment period will vary depending on their circumstances but, there are some things every high school freshman can do now to ensure success through the end of the school year its not too early to sign up for your Spring Semester Fullerton tutoring. 1. Stay organized Its essential for freshmen to stay organized throughout the entire academic year. During winter break this means going through old notes and archiving assignments that are no longer important and saving important study tools like flashcards or test and quiz grades that they can use to study for midterms and finals drink spring semester. Students should also clean and organize their study space both at home and at school and should focus on making sure their digital study environment does not have any unnecessary distraction or clutter. 2. Take a look at final grades Its also important for newer high school students to take a look at all the grades they got on their final exams. They should determine which concepts or topics they need to work harder on and which ones they already know. Students who are having trouble with this step should consult their classroom teacher or a one-on-one tutor to help them go through old assignments. Final grades are an excellent indication of how a student has been doing over the entire semester and can give students great insight into what they need to focus on once they start back to school in January (READ: Irvine Tutoring Tips: Improve your Study Skills This Winter). 3. Make a game plan for spring semester Freshman should also make a detailed game plan to help them be successful throughout the spring semester. Students will need to take a look at what worked, and perhaps more importantly what didnt, during fall term to figure out what changes they need to make next semester. How efficient were the student’s study habits? How long did it take to finish the average homework assignment? Were test and quiz grades consistent? These are just a few of the questions students should ask themselves to improve grades next term. 4. Remember to take breaks With all of this studying, its also important for students to remember to take a break now and then. The first year of high-school requires a lot of responsibility and hard work, but students also deserve to have some time with friends, have some downtime so their brain can relax, and enjoy an overall work-life balance. Students who take adequate brakes are more likely to study efficiently, maintain a positive attitude and enjoy the love of learning throughout their entire high school career. How students feel about school now can effect how theyll feel about applying to college and determine how motivated they’ll be once they get into AP classes and test prep in upcoming years. Improve your grades in the winter and spring semesters with the help of private Fullerton tutoring. Call us today to book your Fullerton tutor. All blog entries, with the exception of guest bloggers, are written by Tutor Nerds. Are you an education professional? If so, email us at pr@tutornerds.com for guest blogging and collaborations. We want to make this the best free education resource in SoCal, so feel free to suggest what you would like to see us write.

?? 5 Reasons Why You Should Invest In Piano Lessons For Your Children

?? 5 Reasons Why You Should Invest In Piano Lessons For Your Children 5 Reasons Why You Should Invest In Piano Lessons For Your Children 5 Reasons Why You Should Invest In Piano Lessons For Your ChildrenFor most parents, there’s often a conflict between wanting their children to have the opportunity to develop interests outside of school, and the fear of becoming a ‘pushy parent’After all is football, art camp, dance classes and then piano lessons a bit too much? It can so often become the activity that gets bumped down your priority list. So when it comes to prioritising after-school activities, it’s important to think about how each activity enriches their lives and helps them to develop skills which will become useful throughout life. Learning to play the piano can increase your child’s confidence and their ability to concentrate and maintain focus. It allows them to practice exercising patience and discipline. Plus, studies have indicated that learning to play the piano can have a positive impact on a child’s mental health.Read on to learn more about these benefits... The benefits of piano lessons for childrenHere are 5 reasons to find a piano tutor today!1. Learning the piano increases concentration, focus, discipline and patience!Talk to any pianist and they’ll tell you that learning the piano takes real patience, determination and perseverance - but also that the reward absolutely outweighs the commitment they’ve put in. Children will need to focus on the instructions given by their piano tutor, and this learning process teaches them fundamental skills that help them listen, comprehend and react to information. Effectively, your children will be listening in one language and translating those instructions into action in another language, which is pretty amazing! It’s no small feat, but being able to concentrate for longer periods of time and having an understanding of the benefits of practice and commitment means increased resilience to problems they face - not to mention the academic and social benefits. It’s a no-brainer really!Check out our handy beginner's guide to learning the piano to find some awesome resources that you can use to help your child with their piano lessons and practice.2. It has a positive impact on your child’s mental healthHelping your children foster good mental health can often be about as clear as mud for parents! Am I doing the right thing? Are my children happy? Do they know how to cope when they feel sad?It’s a countrywide issue and schools are starting to do their part in helping to establish good mental health, and indeed help to tackle children experiencing poor mental health. Journalling, children’s yoga and mindfulness sessions are slowly making their way into the classroom as ways of tackling increasingly poor mental health in children.For parents, it can be difficult to know what to do for the best - but don’t worry there are lots of things you can do at home, and encouraging them to learn an instrument is one. Playing a musical instrument like the piano is thought to improve self-esteem, relieve stress and reduce anxious feelings. Other studies (although mostly conducted on adults) found playing the piano to be a beneficial treatment for depression and stress.By getting your children piano lessons, you’re setting them up with a creative outlet that will help them now - while they continue to develop - but also throughout their whole adult life!3. It is a powerful confidence boosterLearning the piano can have a huge impact on a child’s confidence. It’s not just the sense of achievement they feel when they’ve mastered a new note, tricky chord or mastered their favourite song. It’s also the confidence it takes to perform in front of others. We’re not talking about debuting at the O2 Academy, we’re talking about standing in front of your family, your friends, the people who love you, ready to display your newfound skills. Learning the piano gives children tools to flourish in public speaking or performance, to be comfortable knowing t hat they might make a mistake, and the confidence to carry on when they do. It’s a skill most adults haven’t mastered. There is science behind it! In a 2004 study, children in Montreal who had piano lessons over 3 years had higher self-esteem than those who didn’t. 4. Practical Skills Which Come In HandyIt comes as no surprise that playing the piano is a great way to improve your hand-eye coordination, as well as the skill of independent coordination between your two hands. A study by Cardiff University found that playing the piano had the effect of changing cortical mapping in the brain, in order to increase finger movement speed across the keys. Hand-eye coordination comes in handy in almost everything we do, from writing to typing, to driving, to almost every sport ever invented.5. There are so many opportunities within music!Be honest, who hasn’t dreamed of being a professional musician? Starting an instrument at an early age opens the door to this being a real possibility. And why not? Even if you don’t reach the heights of Ed Sheeran, Arianna Grande or the Foo Fighters... There are a wealth of lucrative careers to choose from behind the scenes within music. Songwriting, recording, producing, music education, among others are all great options! It may not seem as glamorous as the lifestyles of the big stars, but playing smaller venues and for occasions like weddings can be a great and fulfilling career path and one that is not open to everyone. There are also growing industries such as music therapy, a truly worthwhile career that will allow you to help other people through music. Piano lessons are a fantastic investment for your children, from improving confidence to possible opening the door to an incredible career. Piano lessons can be the gift that keeps on giving for children, and one they will surely thank you for in the future! If you want to know more, you can find our comprehensive guide to starting piano lessons and our curated list of fantastic piano resources here We have thousands of great tutors here on Tutorful that are all ready to help get your child started along their musical journey. Click here to get started now

Is it Time to Quit Your Job 8 Red Flags

Is it Time to Quit Your Job 8 Red Flags via Pixabay You dread going to work This isn’t the feeling that you would rather be doing something else that day instead of going to work every so often. It is an almost painful feeling every single day before you go to work. Thinking about walking into your office feels like there is a rock in your stomach. The feeling is so overwhelming that you may just want to break down and cry because you don’t want to go into work. If you wake up every morning and have absolutely nothing to look forward to at work, then it may be time to quit your job. You complain about your job constantly It’s all you talk about with your friends and family. When you get together for brunch with your friends on the weekends, all you contribute to the conversation is how awful your week at work was and what a terrible person your boss is. Everyone complains about their job at some point, but if you find that the only thing you talk about is how much you despise going into work, then maybe it is time for you to quit your job. You justify staying Quitting your job is like breaking up with someone. You know it’s the right thing to do, but you hate confrontation so you’re going to put it off for just a little longer in the hopes that maybe it’ll get better. If you find yourself saying something along the lines of, “I hate my job, but it offers stability and a nice paycheck,” then you are absolutely justifying you staying at your job. You must look past what your current job offers you and instead look at what new opportunities can offer you. When the cons outweigh the pros, then it is time to quit your job. via Pixabay Your health is declining First of all, you should never jeopardize your health for a job. Some people may not know that stress can take a toll on your body physically. Some of these effects include insomnia, headaches, stomach problems, frequent colds, and many other painful effects. Try to take some time off from your job to relax and relieve your stress. If you find that your job is stressing you out to the point that you are experiencing these effects and taking a few personal days off to relax is not helping, it may be time to quit your job. via Pixabay You’re bored Everyone gets a little bored at work sometimes. It may be a slow couple of weeks and you don’t have much to do, but once work picks up you’re excited to be busy. It is when you are bored at work all day no matter what is going on that it becomes a problem. Being consistently bored at work means that you are not fulfilling your potential and have lost all interest in your job. When you find that absolutely nothing excites you about your job, then it may be time to quit your job. via Pixabay You daydream about other opportunities It’s not uncommon for people to get lost in their thoughts while at work. Maybe they’re thinking about the next vacation they will take or what they will be having for dinner that night. If you find yourself daydreaming of other job opportunities and pursuing another time, then it may be a sign that it’s time to quit your job. via Pixabay Your skills aren’t being used One factor that contributes to becoming bored at work is that your special skills are not being used at your job. This holds you back from working to your full potential, especially if these skills are hard to come across. It’s important to feel like you are challenging yourself and cultivating your skills so you can advance later on in the company. If you find that basic skills are needed for your position and your company is not taking advantage of the special skills you have, then it may be time to quit your job. You don’t picture yourself there in the future Take a minute and try to imagine yourself 10 years from now. Are you still working for your company? Do you see the possibility of advancing to another position? Or are you still sitting at your same desk doing the same things you are now? You may see yourself doing working in a completely different field or at another company. If you don’t plan to stay at your company, then it may be time to quit your job.

italki now supports Google Hangouts, FaceTime and QQ!

italki now supports Google Hangouts, FaceTime and QQ! We are very happy to announce that italki now supports Google Hangouts, FaceTime and QQ as alternative VOIP / Instant Messenger / Chat software programs. Why should I add Google Hangouts, FaceTime or QQ? italki wants to provide our users with the greatest, most widely accepted range of VOIP / Instant Messenger / Chat software programs. While SKYPE is the most popular choice, we want to give our users the full benefit of choice so that they are not limited to just SKYPE. We also know that in some regions, certain chat software have better connectivity than others. For example, when trying to call Chinese users, QQ is the software that has the best connectivity. So go ahead and update your communication software choices and connect with the world! italki supports the following Voice Over IP /  IM / Chat software: SKYPE The preferred method of communicating on italki.   Download SKYPE here Google Hangouts Googles default messaging service offering video and voice chat. Download Google Hangouts here FaceTime Apples iOS   Video Conferencing Service.   FaceTime is pre-installed in  all iOS products QQ Chinas most popular IM Service.   Download QQ here (International Version) To add different  Voice Over IP /  IM / Chat programs 1. Hover over your small Profile Picture icon on the upper right hand corner of the screen and click on Edit Profile 2. Scroll down the page to the  Contact Information section.   Click on it which will open up the sections where you can  input different Voice Over IP /  IM / Chat user account information. 3. Enter your Voice Over IP /  IM / Chat user account information for the programs or services which you use. italki now supports Google Hangouts, FaceTime and QQ! We are very happy to announce that italki now supports Google Hangouts, FaceTime and QQ as alternative VOIP / Instant Messenger / Chat software programs. Why should I add Google Hangouts, FaceTime or QQ? italki wants to provide our users with the greatest, most widely accepted range of VOIP / Instant Messenger / Chat software programs. While SKYPE is the most popular choice, we want to give our users the full benefit of choice so that they are not limited to just SKYPE. We also know that in some regions, certain chat software have better connectivity than others. For example, when trying to call Chinese users, QQ is the software that has the best connectivity. So go ahead and update your communication software choices and connect with the world! italki supports the following Voice Over IP /  IM / Chat software: SKYPE The preferred method of communicating on italki.   Download SKYPE here Google Hangouts Googles default messaging service offering video and voice chat. Download Google Hangouts here FaceTime Apples iOS   Video Conferencing Service.   FaceTime is pre-installed in  all iOS products QQ Chinas most popular IM Service.   Download QQ here (International Version) To add different  Voice Over IP /  IM / Chat programs 1. Hover over your small Profile Picture icon on the upper right hand corner of the screen and click on Edit Profile 2. Scroll down the page to the  Contact Information section.   Click on it which will open up the sections where you can  input different Voice Over IP /  IM / Chat user account information. 3. Enter your Voice Over IP /  IM / Chat user account information for the programs or services which you use.

How to Find an Organic Chemistry Tutor For Your Classes

How to Find an Organic Chemistry Tutor For Your ClassesThere are so many ways to find a chemistry tutor these days, so it can be very hard to sift through all the information. Even if you have an idea of what you want from a tutor, you may not know which ones are right for you.If you are in college or your spouse is and you need a chemistry tutor, you can seek out these options over the internet. However, the best thing to do is talk to someone in your chemistry department that knows the various options. They may be able to recommend a tutor that they used.Whether you choose online tutoring or in person, the goal is always the same. You want to make sure that you learn as much as possible in your class. Plus, when you go into a real class you can ask questions. But online tutoring does help you learn much faster.The first thing you need to think about when you look at an online chemistry tutor is whether or not you want them to talk to you directly or just use the computer to interac t with you. If you want a tutor that will actually sit down and talk to you face to face then you might want to consider one that uses voice recognition software. With this, you don't have to speak the entire time. All you do is type and they will speak.If you want a good chemistry tutor, you want to find one that has experience. Find someone who has a lot of books to refer to and can teach you all the different types of classes that you can take. Most students today are taking more than one type of class. So, look for someone who can teach you everything.It may be difficult to find an organic chemistry tutor for all the classes that you have taken. The reason is because many schools now offer accelerated programs, like AP chemistry. This means that you can take up to two more classes without having to retake the course. That is a huge benefit and one that you may want to take advantage of.Online tutoring is definitely the way to go for many students who are not able to get a tutor from a university. A lot of people may find this a bit daunting, but it can be done. Plus, with chemistry courses are becoming so popular these days, online chemistry tutors are always in demand.

How to Become a Tutor in College

How to Become a Tutor in CollegeHow to become a tutor in the college is very simple. Most high schools and community colleges will offer tutoring programs for students who are interested in improving their grades. There are several programs available, and most have a set amount of money a student must pay before they can begin their college programs. In other words, if you are not willing to pay the tuition fees, you cannot receive help.There are a lot of people interested in taking advantage of tutoring, so the best place to look is online. These sites list different colleges, and many of them will provide programs. The big advantage to this method is that you can find a tutor at a school of your choice.When it comes to college students, this is an especially good opportunity. Many courses at community colleges will require work experience, such as physical education or writing classes. The student may not be able to get their work done in time for a scheduled exam, but they can sti ll learn by getting the job done themselves.If a college student already has some experience working with tutors, there is another option. These programs will not require any study time and will likely be more affordable. Most programs are actually designed for students who have less than six months of experience working with a tutor.It is a matter of how much the student wants to pay for the program, and how much he or she wants to learn from it. If the student is looking to earn a scholarship, then they might want to choose a program that will help them improve their grade point average, rather than one that will allow them to earn extra credits.The student should be aware that some tutors can help the student study without any pressure, but most of them will expect the student to perform well in class. A student might want to look into a program where they can practice their class work without having to rely on a teacher.The basics for becoming a tutor in college will help studen ts who are not sure what kind of program they should take. Some tutors are very interested in helping students, while others simply want to earn a living. It is best to think about the program first, and then select the program that fits with your own needs.