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Physics lab

Submitted by mduque on Fri, 03/02/2018 - 13:52

In this  lab we investigated the properties of magnetism and magnetic induction. We are using the knowledge that there is a magnetic field that mediates the force between magnetic objects. We were able to show  how magnetic fields can generate an electric current and how electric currents generate magnetic fields. First, we used a compass and magnet to show how magnets interact at opposite poles. Then, we utilized a magnet and coil combination to show how magnetic fields can generate current. Lastly, we used a two-coil system to prove there was a voltage across the terminals of the second coil.

Magnetic flux is basically the number of magnetic field lines that passes through a closed surface. Magnetic flux depends on and is also equal to the product of surface area and magnetic field. It depends on it changing with time. When a magnetic is near a compass and the south pole of the compass needle is pointing at the magnetic, the needle’s point must be at the north pole of the magnet (a compass needle is simply a small magnet balanced on a pin). We then can infer that when the compass needle is exposed to a magnetic field it will pivot (because it wants to  align with the field lines of the magnet). This is because the north pole will repel the north pole of the magnet and vise versa with south. On the other hand, the north pole will attract the south-pole (opposites attract).

Shannon index

Submitted by mduque on Fri, 03/02/2018 - 13:48

We decided to investigate tree species richness and diversity of a small hill in Thatcher way and on University Drive behind the school parking lot in Southwest. These two places are at least 1.5 miles away from each other meaning the areas are different enough to have different populations. The trees of interest on Thatcher way are on a hill in an isolated area in the Northeast residential area on campus, whereas the trees on University Drive are surrounded by parking lots and involve a larger surface area. The trees on University Drive appear to be more spread out, therefore receive sunlight and rain more directly than the trees on Thatcher way. Temperature is most likely the same in both areas. The trees in Thatcher way are in a steeper area compared to the trees in Southwest. We predicted there would be more species richness and diversity in the Southwest area. Our predictions were based on observations of Southwest receiving more direct water and sunlight. This would make it easier for them to create their own food and energy through photosynthesis. An increased space promotes growth and resistance to stress whereas a tighter space makes the trees more vulnerable to disease, fire, and droughts. If our predictions are correct, the Southwest area will have a higher Shannon Index, meaning a greater variety of species and a somewhat equal distribution. If we are wrong, this means we overlooked other factors that could contribute to a reduced diversity in the Southwest area.

Cancer Genetics

Submitted by mduque on Fri, 03/02/2018 - 13:27

The anti-apoptotic Bcl-2 family members interact to maintain mitochondrial integrity and regulate cellular commitment to apoptosis. Apoptosis, cell death, is crucial for development and homeostasis. These signals are normally tightly regulated in cells. An unbalance is needed for tumorigenesis to occur and becomes even greater when the tumor becomes resistant to the treatments. By specifically regulating these proteins and the pathways involved, it can be possible to have more control in the way cancer cells act.


Submitted by mduque on Fri, 03/02/2018 - 12:57

Inhibitory interneurons make it harder for action potential to fire. They work by allowing GABA to bind to transmembrane receptors that allow chloride ions into the cell. This binding makes the membrane potential more negative and the threshold for action potential harder to be achieved. If these were changed to excitatory in the stretch reflex, functions to maintain the muscle at a constant length would fail. As soon as the stretched muscle began to contract the antagonist muscle would stretch & both muscles would contract simultaneously.



Submitted by mduque on Fri, 02/23/2018 - 15:13

Optogenetics refers to the biological technique which involves the use of light to control neurons. These neurons are genetically modified to express light-sensitive ion channels. Precise neural control is achieved by using channelrhodopsin, halorhodopsin, and other similar opsins that function as light-gated ion channels. Channelrhodopsins excite neurons while halorhodopsin inhibits them.  This method has to act and operate precisely and quickly in order to allow addition or deletion of specific activity patterns within cells. In order to keep up with optical control, reporter proteins are used, enabling the fused fluorescent proteins to detect the selected neurons. This advancement is now giving humanity the ability to alter the activity of specific types of neurons. Depression, a huge problem in the U.S, for example can be possibly treated with optogenetics. MRI images have suggested parts the brains of people who have depression look different than those without it. Since dopamine and serotonin have shown to be important in cognition, motivation, drug addiction and psychiatric disorders, stimulation by LED light at the wavelength of blue light to activate channelrhodopsin expressed in targeted dopamine neurons in the mid-brain should be extensively studied. That is, it is now technically possible to study what the activation and deactivation of specific neurotransmitters in this part of the brain does.


Submitted by mduque on Fri, 02/23/2018 - 15:01

CD44 is a cell surface adhesion receptor that is highly expressed in many cancers and appears to regulate metastasis. Its recruitment to the cell surface and its interaction with extracellular matrix ligands promote the migration and invasion processes involved in metastases. Therefore, elevated levels of soluble CD44 in the serum of cancer patients can be used as a marker for the existence of tumor cells. The over-expression of this receptor is particularly seen in breast cancer cells. This discovery may allow for specific cancer cells to be detected rather than invading healthy cells through chemotherapy to get rid of defective muted ones.


Submitted by mduque on Fri, 02/23/2018 - 14:51

Cells are normally searching for bacterial invaders and potential tumor cells, if they recognize one, they induce an immune response. However, healthy T-cell “checkpoints” can be muted by other proteins on the cell surface and can in turn weaken immune responses. This phenomenon is often seen in tumor cells where muted T-cell checkpoint molecules are expressed. To overcome this problem without the need of radiation, nontoxic nanoparticles can be used to sensitize the immune system. New antigens can be exposed to T cells which can prime those T cells to target other tumor cells that carry them as well. In order to get past the immune system, they need to be the appropriate size because small particles are more likely to get around macrophages. Prior to inducing them into the body, they have to be coated with polyethylene glycol shell which can help them survive longer in the bloodstream.


Submitted by mduque on Fri, 02/23/2018 - 14:45

The genus canis has showed an interesting phenomenon with the discovery of the “coywolf”; a hybrid canid exhibiting mostly Canis lupus and Canis dirus genes but also Canis lupus familiaris genes. Many have gone as far as to calling the coywolf a new species. However, this assumption might be a bit of a stretch. Genetic tests show this is not the first time intermixing takes place. The eastern coyote for example, is also a mix of the three. In my opinion, that is because coyotes, domestic dogs, and wolves are the same species “that would very much prefer not to breed with each other”. The fact that they have continuously mated with one another throughout history and created viable offspring suggests they are indeed the same species. This has resulted in genetic swapping and gene variations amongst the three. The gene differences may result in sexual “preferences” where wolves would rather mate with a wolf, coyotes with coyotes, and so on. Still, preference is not enough to deem them three separate species. “Gene flow continues in all directions, keeping things mixed up, and leading to continual variation over their range, with no discrete boundaries."  Instead of being called closely related species, it would be more accurate to call them subspecies.

Perfect Paragraph

Submitted by mduque on Fri, 02/23/2018 - 12:16

A study I recently analyzed for my sensory neurology course, aimed to find which mechanically-sensitive transducer channels allow hair cells to detect vibrations. The channels are believed to activate as a result of deflection towards the tallest stereociliary row. This is caused by a force applied by extracellular tip-links. Calcium signals in the first, second, and third stereociliar rows of a rat’s cochlear inner hair cells were visualized by using fast confocal imaging of fluorescence changes that reflect calcium entry during stereociliary bundle stimulation. Calcium was the ion of choice because hair cell channels have shown to be highly permeable to it. Individual stereocilia were imaged at the apical portion of the bundle and indicator dyes with a range of affinities were used. The results from these experiments indicated there are no channels in first row stereocilia therefore suggesting channels that detect vibrations of the stereociliary bundle are only present at the bottom of tip-links.


Optogenetic simulation of region of hippocampus thought to active fear memory recall

Submitted by mduque on Thu, 02/15/2018 - 11:11

Yesterday I went to a seminar held by Steve Ramirez from Boston University who is studying a way to artificially activate positive and negative memories in healthy and maladaptive states. He explained optogenetic reactivation of hippocampal dentate gyrus neurons activated during fear conditioning were sufficient to induce freezing behaviour.  That is, activating these neurons without actually presenting the mouse with the fear stimulus was sufficient for the mouse to show signs of fear. In a similar proportion of cells, the freezing was not detected upon light-stimulation on ChR2 in non-fear conditioned mice. The freezing, act of fear, was also not detected upon fear-conditioned mice with cells labeled by a different protein instead of ChR2. 


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