Notes, summaries, assignments, exams, and problems for Other courses

Cancer Stem Cells vs. Normal Stem Cells

Both normal stem cells and cancer stem cells (CSCs) share the ability to self-renew through asymmetric division, allowing one daughter cell to remain a stem cell while the other differentiates. They both generate heterogeneous populations of mature cells: normal stem cells produce tissue-specific cell types, while CSCs produce diverse tumor cells. Both rely on similar regulatory signaling pathways such as Wnt, Notch, and Hedgehog, but these pathways are tightly controlled in normal stem cells and dysregulated in CSCs, promoting tumor formation. Both exist as rare subpopulations within tissues, depend on signals from their niche, and can remain quiescent for long periods. CSCs, however, show enhanced resistance... Continue reading "Cancer Stem Cells: Signaling Pathways and Therapeutic Potential" »

Fast File System (FFS)

Writes

Writes: Writes data to blocks chosen by cylinder groups. Tries to place related blocks near each other and rotationally optimize access. Metadata updates (inodes, directories) are also written in-place within the same group.

Reads

Reads: Very fast because data is grouped by cylinder, minimizing seeks. Sequential reads benefit from rotational optimization and large block sizes (4–8 KB). The first read goes through the inode, then the inode's data block pointers.

Appends

Appends: Allocates the next block near the previous one. Uses rotational delay tables to place the next block just in time for the disk head. Large blocks plus fragments allow efficient small-file appends.

Crash Recovery

Crash Recovery: Uses fsck to walk... Continue reading "File Systems, Kernels, and High-Performance Networking" »

ASME Code for Design of Shafts

The ASME (American Society of Mechanical Engineers) code provides standard guidelines for calculating the safe diameter of a shaft subjected to different types of loads. The code considers combined effects of bending moment, torsional moment, shock, and fatigue.

ASME Shaft Diameter Determination

According to the ASME code, the shaft diameter is determined using the following formula:

$$d = \left( \frac{16}{\pi\,\tau_{allow}} \sqrt{ (K_b M_b)^2 + (K_t T)^2 } \right)^{1/3}$$

Formula Variables:

• $M_b$ = Bending moment
• $T$ = Torque
• $\tau_{allow}$ = Allowable shear stress
• $K_b$ = Shock and fatigue factor for bending
• $K_t$ = Shock and fatigue factor for torsion

ASME Recommended Allowable Stresses

The allowable shear stress ($\tau_... Continue reading "ASME Shaft Design Standards and Calculations" »

Shipboard Crew Positions

The crew of a vessel is organized into a clear hierarchy, divided by department. Below is a summary of various positions.

Core Artificial Intelligence Concepts

Black Box Models

Black Box Models are systems where the inputs and outputs are known, but the internal process is not transparent. Example: Facial recognition software within a machine learning system.

Deepfakes

Deepfakes refer to AI-generated media, such as fake celebrity videos, created to appear authentic.

Generative AI

Generative AI is technology that changes or generates realistic images, videos, and text. Example: Chatbots.

Large Language Models (LLMs)

Large Language Models are AI systems trained on vast amounts of text to understand and generate human-like language. Example: Grammarly.

Automation and Interaction

Workforce Automation

Workforce Automation involves AI, robots, or software taking over repetitive... Continue reading "Essential Artificial Intelligence Terms and Definitions" »

A widely used mathematical framework for Gaussian plume model assumes that the concentration distribution of pollutants in cross-sections perpendicular to the wind direction follows a normal distribution in both vertical and horizontal directions. The model is applied under specific assumptions:

1. Point source emissions with low vertical velocities.
2. Emissions at temperature ($T$) equal to or slightly above ambient air.
3. Stable atmospheric conditions, at least over one-hour intervals.
4. Flat and uniform soil with little surface roughness.

Hypotheses for the Model

• Wind speed and direction: constants.
• Conditions of the parameters that characterize the dispersive properties of the atmosphere: constants.
• Soil: uniform and flat.

General Diffusion Equation

The general... Continue reading "Gaussian Plume Model: Pollutant Dispersion Fundamentals" »

Investment Analysis II: Key Cash Flow Components

Financial leverage is debt. "Unleveraged" Free Cash Flow (FCF) means we calculate FCF without regard to how the firm is financed. Ultimately, we are valuing the assets of the project. We achieve this by estimating how much cash is generated by the asset side of the balance sheet.

Capital Expenditure (CAPEX)

Capital Expenditure (CAPEX) is defined as the original cost of investment in property, plant, or equipment and other long-term assets.

Formula for CAPEX

NET PPE (current) - NET PPE (prior) + Depreciation

Depreciation and Asset Valuation

Depreciation: Depreciation charges are intended to represent the cost of wear and tear over the asset's life. The Straight-Line Depreciation method divides the asset’s... Continue reading "Capital Budgeting: Calculating Cash Flows and Valuation Metrics" »

SR Flip-Flop (Set-Reset Flip-Flop)

The SR flip-flop is one of the simplest sequential circuits and serves as a fundamental building block for more complex flip-flops. It is a 1-bit memory device with two inputs: Set (S) and Reset (R). It has two outputs, Q and its complement Q̅ (Q with overline).

Logic Diagram and Working

An SR flip-flop can be constructed using two cross-coupled NAND gates (or NOR gates). Below is the working principle for the NAND-gate implementation:

1. Set Condition (S = 0, R = 1):

   • When S = 0, the output of the top NAND gate (Q) is forced to 1 (since NAND is the inverse of AND).

   • This Q = 1 is fed into the bottom NAND gate with R = 1; the bottom gate's inputs become 1 and 1, so its output (Q̅) becomes 0.

   • The circuit is now in the

Complete List of English Irregular Verbs

Irregular Verbs: Part 1 (A–F)

• be – was/were – been → ser / estar

• become – became – become → convertirse / llegar a ser

• begin – began – begun → empezar / comenzar

• bite – bit – bitten → morder

• blow – blew – blown → soplar

• break – broke – broken → romper

• bring – brought – brought → traer

• build – built – built → construir

• buy – bought – bought → comprar

• can – could – been able (to) → poder / ser capaz

• catch – caught – caught → atrapar / coger

• choose – chose – chosen → elegir

• come – came – come → venir

• cost – cost – cost → costar

• cut – cut – cut → cortar

• do – did – done → hacer

• dive – dived/dove – dived → bucear

• draw –

National Disaster Management Plan (NDMP)

1. The National Disaster Management Plan (NDMP) was first released in 2016 by the Government of India.
2. It is prepared by the National Disaster Management Authority (NDMA).
3. It provides a framework for disaster prevention, mitigation, preparedness, response, and recovery.
4. The plan focuses on all types of disasters – *natural* (floods, earthquakes, cyclones) and *man-made* (industrial accidents, chemical disasters).
5. It aligns with the Sendai Framework for Disaster Risk Reduction (2015–2030), ensuring international best practices are followed.
6. The plan emphasizes a “Build Back Better” approach during recovery and reconstruction.
7. It assigns specific roles and responsibilities to central, state, and local authorities.