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Perm

Perm most commonly refers to a major city in Russia. It may also refer to:
  • '''Geographical locations:'''
    • Perm, Russia, a city on the Kama River in the Ural Mountains with a population of approximately 1.03 million (as of 2025)
    • Perm Krai, a federal subject of Russia of which the city is the capital
  • '''Scientific terms:'''
    • Permian, a geologic period in the Paleozoic era
    • Permutation, a mathematical concept involving rearrangements
    • Perm, a unit of permeance in electromagnetism
  • '''Cultural and technological terms:'''
    • Perm (hairstyle), a curled hairstyle achieved with chemicals
    • Permalloy, a nickel-iron alloy with high magnetic permeability
    • PERM, the labor certification process for permanent residency in the United States

Geographical Locations

Perm, Russia

Perm is a major city in Russia, serving as the administrative center of Perm Krai and situated on both banks of the Kama River in the western foothills of the Ural Mountains. The city covers an area of approximately 800 square kilometers and had a population of 1,034,002 as of the 2021 census, with estimates around 1,027,000 as of 2024, making it one of Russia's largest urban centers east of the Urals. Its strategic location along the Kama, a major tributary of the Volga and one of Europe's longest rivers (1,805 km), has historically facilitated trade and transportation, while the surrounding Ural terrain provides access to rich mineral resources. The name "Perm" derives from Uralic (Komi-Permyak) roots, possibly meaning "far-away land" or referring to a "forested hill," reflecting the region's natural landscape. The city's origins trace back to 1723, when it was founded as the settlement of Yagoshikha by the Russian-Dutch mining engineer Wilhelm de Gennin to support ironworks and copper smelting operations initiated under Peter the Great's industrialization efforts. By 1724, the Yegoshikha metal-smelting works were operational, marking the site's early industrial significance with around 112 households established. In 1781, under Empress Catherine II, the settlement was officially renamed and designated the capital of the newly formed Perm Governorate, with a formal city plan developed by architect Andrey Gruber. During the Soviet era, it was briefly renamed from 1940 to 1957 in honor of , before reverting to its historical name. The geological Permian period, spanning roughly 299 to 252 million years ago, was named after the Perm region due to extensive fossil-bearing strata identified there by British geologist in the 19th century.

Perm Krai, Russia

Perm Krai is a federal subject of Russia formed on December 1, 2005, through the merger of Perm Oblast and the Komi-Permyak Autonomous Okrug following a 2004 referendum. The krai covers an area of 160,236 km² and has its administrative center in the city of Perm, which serves as the region's economic and administrative core. It had a population of 2,532,405 as of the 2021 census, with estimates of 2,495,000 as of 2024. Geographically, Perm Krai spans the western slopes of the Ural Mountains, encompassing the Kama River basin and extensive boreal forests that dominate much of the landscape. The region is rich in natural resources, including significant deposits of oil and natural gas, potassium and magnesium salts, as well as timber from its vast forested areas. These resources form the backbone of the krai's extractive industries and contribute to its strategic importance in Russia's resource economy. The economy of is primarily driven by , , and , with the sector leveraging the region's mineral wealth. Key centers include and , where major operations focus on the extraction of salts and the of chemicals and fertilizers, supported by like . Agricultural activities, including crop cultivation and livestock farming, complement these industries, utilizing the fertile lands in the basin. Ethnically, the population is predominantly at about 89%, with notable minorities including (4%) and Komi-Permyaks (2.2%), according to the 2021 census, reflecting the krai's historical integration of the former autonomous . Administratively, is divided into 33 districts and urban , encompassing 25 cities and towns.

Scientific Terms

Permian geologic period

The Permian period spans from 298.9 to 251.9 million years ago, marking the final phase of the Era in Earth's geologic history. This era was formally named in 1841 by Scottish geologist , who identified distinctive rock strata in the Perm region of as the basis for defining the period, drawing from collaborative work with Russian geologists on post-Carboniferous beds. The period's timeline reflects a dynamic phase of continental assembly and climatic transition, culminating in profound biological upheaval. During the Permian, Earth's climate shifted from initially cool and humid conditions, reminiscent of the preceding Carboniferous, to increasingly warm and arid regimes, particularly in equatorial zones. This aridification was closely tied to the formation of the supercontinent Pangea, as crustal plates converged to fuse most landmasses into a single entity by the early Permian, altering global circulation patterns and promoting widespread dryness. Rock formations from this time prominently feature red beds indicative of oxidized sediments in terrestrial environments, extensive evaporites from restricted marine basins, and localized coal measures in remaining swampy areas, deposited amid fluctuating sea levels that produced cycles of shales, sandstones, limestones, and dolostones. These lithologies, observed in regions like the western United States and the Ural Mountains, underscore the period's transition to more seasonal and continental-scale aridity. Biologically, the Permian witnessed significant evolutionary developments, including the diversification of reptiles, with diapsids (ancestors of modern reptiles) and synapsids (mammal-like reptiles) proliferating across Pangea and adapting to varied terrestrial niches. However, the period ended catastrophically with the , known as the "Great Dying," around 251.9 million years ago, which eradicated approximately 96% of marine species and about 70% of terrestrial vertebrates through mechanisms including rapid , ocean anoxia, and volcanic activity from the . This event, the most severe mass extinction in Earth's history, reset ecosystems and facilitated the subsequent rise of archosauromorphs in the , precursors to dinosaurs and other ruling reptiles. The Permian is subdivided into the (early Permian, encompassing Asselian to Kungurian stages), (middle Permian), and (late Permian) series, reflecting progressive faunal and floral changes. Key fossil sites include the Perm region's strata in , such as the Kungurian deposits of the Basin, which preserve diverse terrestrial and assemblages like insects, , and early tetrapods, alongside exceptional reef complexes like the Capitan Reef in the Guadalupe Mountains of , renowned for well-preserved Permian fossils including brachiopods, , and fusulinids. Paleontologically, the period's significance lies in illuminating the drivers of mass extinctions—such as climate volatility and effects—and the pathways for post-extinction recovery, providing critical insights into life's resilience and the origins of dominance by archosaurs.

Permutation in mathematics

In mathematics, a permutation of a finite set is defined as a bijective function from the set to itself, which rearranges its elements while preserving the set's cardinality. For a set with n elements, such as \{1, 2, \dots, n\}, a permutation \sigma maps each element to a unique element in the set, ensuring every element is both mapped to and from exactly once. Permutations are often represented in two-line notation, showing the domain and image, or more compactly in cycle notation, where disjoint cycles describe the mapping. For example, the permutation that swaps 1 and 2 while fixing 3 on the set \{1, 2, 3\} is denoted as (1\ 2) in cycle notation, indicating $1 \mapsto 2, $2 \mapsto 1, and $3 \mapsto 3./05%3A_Permutation_Groups/5.01%3A_Definitions_and_Notation) The total number of distinct permutations of n elements is given by n!, the factorial of n, which counts all possible rearrangements. A key property of permutations is their , determined by the parity of the number of inversions—an inversion being a pair (i, j) with i < j but \sigma(i) > \sigma(j). A permutation is even if it has an even number of inversions and odd otherwise; this parity is well-defined and invariant under decomposition into transpositions. The set of all even permutations forms the A_n, a of index 2 in the S_n, which comprises all permutations of n elements under composition./04%3A_Families_of_Groups/4.04%3A_Alternating_Groups) Permutations find extensive applications across mathematical disciplines. In group theory, the S_n serves as a foundational structure, modeling symmetries and actions on sets. In , exponential generating functions enumerate permutations by cycle type, such as \exp\left(\sum_{k=1}^\infty \frac{x^k}{k}\right) = \sum_{n=0}^\infty \frac{n! x^n}{n!}, facilitating counts of restricted permutations. In , algorithms like efficiently generate all n! permutations through recursive swaps, achieving optimal for enumeration tasks. Historically, Leonhard Euler advanced the study in the with his work on —permutations without fixed points—deriving their count as !n \approx n!/e, influencing later developments. Modern applications extend to , where permutation ciphers rearrange blocks for , and probability, where permutations model uniform random arrangements to compute event likelihoods, such as the probability of a derangement approaching $1/e. In informal mathematical contexts, permutations are sometimes abbreviated as "perms."

Perm as a unit of permeance

The perm is a unit of permeance used in to quantify the rate of transmission through materials, defined as the passage of 1 grain (approximately 64.8 mg) of per hour through 1 of material under a differential of 1 (approximately 3,386 ). In SI units, this equates to $5.72 \times 10^{-11} \, \mathrm{kg/(Pa \cdot s \cdot m^2)}, or equivalently 57.2 ng/(s·m²·Pa), providing a standardized measure for comparing moisture permeability across diverse materials such as building membranes, fabrics, and coatings. The unit originated in the 1940s through research by wood scientists at the U.S. Forest Products Laboratory (part of the Department of Agriculture), who developed it to address moisture-related issues in insulated wood-frame buildings, such as paint peeling due to vapor diffusion; this work built on early ASTM standards like E96 (first published in 1941) for testing water vapor transmission rates. A related metric perm, used in some international contexts, differs slightly and corresponds to approximately 1.52 U.S. perms or 86.8 ng/(s·m²·Pa), but the U.S. perm remains dominant in North American building codes and practices. In practice, perm ratings classify materials by their vapor permeability to guide selection in moisture control strategies: Class I materials (≤0.1 perm) act as vapor barriers, restricting diffusion to prevent in assemblies like exterior walls; Class II (0.1–1.0 perm) and Class III (1.0–10 perm) serve as vapor retarders, allowing controlled transmission; while materials exceeding 10 perms are considered vapor permeable, facilitating drying in humid climates. These classifications, outlined in codes like the International Residential Code, help avoid issues such as growth by balancing vapor flow with placement. Perm ratings are essential in applications like HVAC system design, where low-perm vapor retarders on chilled water piping minimize risks; in roofing, particularly low-slope assemblies, to control interior migration into layers; and in overall to enhance durability by preventing interstitial that could lead to structural degradation or proliferation.

Cultural and Technological Terms

Perm hairstyle

The perm, short for permanent wave, is a chemical hair treatment that creates lasting curls or waves by altering the hair's structure. The process begins with wrapping sections of hair around rods or curlers to define the desired . A , such as , is then applied to break the disulfide bonds in the hair's proteins, allowing the strands to be reshaped. After a time, a neutralizer like is used to reform and stabilize the bonds in their new configuration, locking in the curls. The effects typically last 3 to 6 months, depending on hair type, , and rate. The origins of the perm trace back to early 20th-century experiments by German hairdresser Karl Nessler, who demonstrated a machine-based permanent waving technique in in 1906 using heated brass rods and on his wife's . This innovation gained traction in the 1920s alongside the rise of the bob haircut, as women sought defined waves to complement shorter styles amid era's fashion shift. Perms surged in popularity again during the , embodying the decade's "big hair" trend with voluminous, teased curls that symbolized excess and boldness. Variations include acid perms, which use gentler solutions with a of 6 to 7 for finer or damaged to produce softer waves, and alkaline perms, featuring stronger levels around 9.5 for coarser, resistant to achieve tighter curls. Despite their appeal, perms carry health risks due to the harsh chemicals involved, including hair breakage, dryness, and weakened structure from repeated bond disruption. Allergic reactions can manifest as scalp irritation, redness, itching, or swelling, often requiring a beforehand. In severe cases, improper application may cause chemical burns on the or , leading to , , or even permanent follicle damage. Modern adaptations like digital perms mitigate some risks by combining chemical solutions with controlled heat from ceramic rods, creating natural-looking waves without traditional rod wrapping; this technique, popularized in and , emphasizes bounce and longevity while reducing processing time. In and culture, perms have influenced iconic looks, such as Dolly Parton's signature voluminous, permed blonde tresses in the , which amplified her glamorous persona and inspired widespread adoption of big, curly styles. The era's perms, blending short layered tops with long, curled backs, became a staple in pop culture, worn by figures from rock musicians to everyday trendsetters, reflecting the decade's rebellious and extravagant spirit.

Permalloy

Permalloy is a renowned for its exceptionally high magnetic permeability, making it a cornerstone material in soft magnetism applications. The name derives from "permeability" and "," reflecting its primary attribute of efficiently conducting with minimal energy loss. Discovered in 1914 by Gustav Elmen at Bell Laboratories during research into materials for improving long-distance transmission, permalloy was first detailed in a 1923 publication describing its superior performance over existing alloys like silicon steel. The standard composition consists of approximately 80% and 20% iron, though the original formulation was 78.5% and 21.5% iron, which exhibited a (μ_r) of up to 25,000 at low magnetizing fields of about 0.04 s—roughly 500 times that of pure iron. Commercial variants achieve even higher values, with μ_r reaching around 100,000, enabling amplification of weak magnetic fields. Key properties include low , typically below 1 , which allows easy magnetization and demagnetization with little magnetism; high of approximately 800 kA/m (or 1 T); and near-zero , minimizing mechanical stress under magnetic fields. These characteristics stem from the alloy's face-centered cubic , which reduces and losses to about one-third those of 4% silicon iron at 50 Hz and 10,000 gauss. Variants such as , which incorporates small additions of or (e.g., 80% , 15% , 5% ), further enhance shielding effectiveness by boosting permeability while improving for forming complex shapes. Manufacturing involves to minimize impurities like carbon and , followed by hot and cold rolling, annealing in at 1100–1200°C, and final stress-relief treatments to optimize magnetic properties. This process ensures high purity and uniformity, critical for achieving peak performance in sensitive devices. Permalloy's applications span soft magnetic devices, including cores for transformers and inductors where its high permeability reduces losses and enables compact, efficient designs; magnetic amplifiers for in early ; and toroidal cores in core memory systems of mid-20th-century computers, leveraging low for reliable and retrieval. Historically, it revolutionized by enabling permalloy-powder loading coils in transatlantic cables, increasing signal transmission speeds from 40 to 400 words per minute by compensating for at voice frequencies.

PERM labor certification process

The PERM labor certification process, formally known as the Program Electronic Review Management system, is a requirement administered by the U.S. Department of Labor (DOL) that allows employers to hire s for permanent positions in the United States by certifying that no qualified U.S. workers are available for the job opportunity and that hiring the foreign worker will not adversely affect the wages or working conditions of similarly employed U.S. workers. Employers must file Form ETA-9089, the Application for Permanent Employment Certification, electronically through the DOL's system to initiate the process. Introduced on March 28, 2005, PERM replaced the prior attestation-based system (Form ETA-750) to enhance efficiency and oversight in labor market testing. The process begins with the employer obtaining a prevailing wage determination (PWD) from the DOL's National Prevailing Wage Center, which establishes the for the position based on the occupational , geographic area, and other factors to ensure it matches or exceeds what U.S. workers earn in similar roles. Following the PWD, which is valid for 90 days to one year, the employer conducts to test the labor market, including placing a job with the State Workforce Agency for at least 30 days, running two Sunday newspaper advertisements (for professional positions, plus three additional recruitment steps such as job fairs or online postings), and documenting all U.S. worker applications, interviews, and lawful reasons for rejection. After completing recruitment—typically lasting 60 to 180 days—the employer files Form ETA-9089 within 180 days of the recruitment start date, attesting to and the unavailability of qualified U.S. workers. The DOL may conduct audits, either randomly or based on specific criteria, requiring the employer to submit supporting documentation within 30 days; failure to comply can result in denial, supervised recruitment, or debarment from the for up to two years. Processing times for PERM applications vary based on caseload and , with average taking 12 to 18 months as of late 2025, though audited cases can extend beyond 24 months. Certain occupations qualify for the Schedule A streamlined process, bypassing full ; Group I includes registered nurses and physical therapists, where employers file directly with the DOL using data from Schedule A , while Group II covers aliens of exceptional ability in the sciences or arts, requiring evidence of without labor market testing. In contrast, the standard PERM process applies to most other positions and mandates comprehensive . Common challenges include demonstrating the employer's ability to pay the proffered wage from the priority date (the filing date of the PERM application) through financial evidence such as annual reports, federal tax returns, or audited , which the DOL verifies during audits to prevent underpayment. Additionally, protections against displacing U.S. workers require employers to certify that no U.S. employees in similar positions were laid off within 180 days before or after the PERM filing date, with violations leading to application denial. An approved PERM certification serves as a prerequisite for the employer to file , Immigrant Petition for Alien Worker, with U.S. Citizenship and Immigration Services (USCIS) under the EB-2 (advanced degree or exceptional ability) or EB-3 (skilled workers, professionals, or other workers) employment-based preference categories, enabling the to pursue () via adjustment of status or consular processing. As of 2025, enhancements to the electronic filing system via FLAG include a 33-day grace period for PERM applications affected by the earlier in the year, allowing extensions for expired periods or PWDs to accommodate processing delays.

References

  1. [1]
    Reference passport about the Perm region
    Apr 18, 2025 · The population of the region is 2,495.3 thousand people. The city of Perm has a population of 1,027.1 thousand people and is located 1,386 ...Missing: facts | Show results with:facts
  2. [2]
    Perm Travel Guide - Complete Russia Destination
    It sits on the banks of the Kama River near the Ural Mountains, covering an area of 799.68 square kilometres. With over one million residents Perm is the 15th- ...
  3. [3]
    History at a glance - Perm City, Russia official web-site
    Perm has 6 twin cities worldwide. Perm ranks fourth in Russia in terms of the area. The world's largest 20-inch cannon is located in Perm. Perm was the ...Missing: geography | Show results with:geography
  4. [4]
    Perm: Industrial and cultural center of the Urals - Russia Beyond
    Apr 7, 2015 · Located just on the European side of the Ural Mountains, the metropolis of Perm is both an industrial powerhouse and one of Russia's major cultural centers.Missing: geography | Show results with:geography
  5. [5]
    City of Perm
    About half of the industrial potential of the Perm region is concentrated in the city. Perm is located on the Kama river, the fifth largest river in Europe.Missing: geography | Show results with:geography
  6. [6]
    Perm Today - Perm City, Russia official web-site
    Perm is located on both banks of the Kama river which is Europe's fifth longest river after the Volga, the Danube, the Ural and the Dnieper.Missing: Mountains center Krai
  7. [7]
    Perm: Cost of Living, Salaries, Prices for Rent & food - LivingCost.org
    Oct 14, 2025 · Cost of Living in Perm. Updated: October 14, 2025 ... With an estimated population of 1.03M, Perm is the 15th largest city in Russia.<|separator|>
  8. [8]
    Permian Period—298.9 to 251.9 MYA (U.S. National Park Service)
    Apr 28, 2023 · In 1841 British geologist Roderick Impey Murchison named this system from the province of Perm in Russia, where it consists of a great thickness ...
  9. [9]
    Permskaya SDPP - Интер РАО – Электрогенерация
    Its economy relies on strong manufacturing sector, which is represented by oil, chemical, petrochemical, metallurgy, machinery and wood industries. Perm ...
  10. [10]
    Trans-Siberian Route Description - Russian Rail
    Perm. 1397 km. 20h 10min. Perm lies about 800 miles east of Moscow on the western slopes of the Ural Mountains ...
  11. [11]
    History of theater - Perm Opera and Ballet Theatre
    Theatre history · 1870 · 1880 · 1890 · 1900 · 1910 · 1920 · 1930 · 1940.
  12. [12]
    diaghilev festival - Official tourism site of Perm region - Visitperm.ru
    The International Diaghilev Festival, established in Perm, aims to maintain and develop the traditions of the outstanding impresario and agitator of Russian ...Missing: White Swan Cathedral Trans- Siberian Railway
  13. [13]
    Perm Territory
    The Perm Territory is where tourism began in the Urals, and the health resorts of the Kama region are well known all across Russia. The famous Ust-Kachka resort ...
  14. [14]
    Perm | Ural Mountains, Volga River, Kama River | Britannica
    Oct 25, 2025 · Three-fourths of the population is urban, reflecting Perm's position as part of the Urals industrial area. It is exceptionally rich in minerals, ...
  15. [15]
    [PDF] Investor's Guide Perm Territory
    Dec 1, 2005 · The region is rich in natural resources and has a powerful and diversified industrial complex (oil, chemicals and petrochemicals, ferrous and ...
  16. [16]
    News | PJSC Uralkali
    Oct 6, 2025 · The Company's assets consist of 5 mines and 7 ore treatment plants in the towns of Berezniki and Solikamsk (Perm Region, Russia).Missing: petrochemicals chemicals
  17. [17]
    Permian Period | Natural History Museum
    Oct 30, 2012 · *The Permian was named in 1841 by Murchison in collaboration with Russian Geologists for the beds lying above Carboniferous strata in the ...
  18. [18]
    The Permian Period
    The Permian period lasted from 299 to 251 million years ago and was the last period of the Paleozoic Era.
  19. [19]
    [PDF] The Permian System in Kansas
    West et al.—The Permian System in Kansas 57. Inferred History of the Permian Period. Cycles and Cycle Hierarchies. Wanless and Weller (1932) introduced the ...Missing: timeline | Show results with:timeline
  20. [20]
    [PDF] Paleotectonic Investigations of the Permian System in the United ...
    Each chapter discusses, in order, rocks that underlie the Permian, the several intervals or divisions of the Permian (from oldest to youngest (table. 1, in ...
  21. [21]
    Paleozoic | U.S. Geological Survey - USGS.gov
    The Permian Period: 299 to 252 million years ago · Media. Trek through Time Graphics, Permian. Sources/Usage: Public Domain. View Media Details. Artist's ...
  22. [22]
    Mass Extinctions Through Geologic Time - National Park Service
    Feb 28, 2025 · The End-Permian extinction at approximately 251.9 million years ago was the largest extinction event in the history of life when 96% of species, ...Coral Reefs and Mass... · End-Permian Extinction · End-Triassic ExtinctionMissing: details | Show results with:details
  23. [23]
    The rise of the ruling reptiles and ecosystem recovery from the ... - NIH
    Jun 13, 2018 · Our analyses support a multiphase model of early archosauromorph diversification, largely in response to the events of the PT mass extinction.
  24. [24]
    [PDF] Permian Triassic - Geologic TimeScale Foundation
    Guadalupian. Permian. Cisuralian. 240. Lopingian. Age. ICS. Period. Standard ... Permian / Triassic (236-273 Ma time-slice). Updated by James G. Ogg (Purdue ...
  25. [25]
    [PDF] Geology of the Volga-Ural Petroleum Province and detailed ...
    The upper Kungurian beds mark the beginning of the fourth and final Paleozoic cycle of deposition. Fourth Paleozoic Cycle (latest Early Permian and Late Permian).
  26. [26]
    Geology of Guadalupe Mountains National Park - USGS.gov
    The Capitan Reef complex makes up the Guadalupe Mountains and is one of the best-preserved Permian fossil reefs in the world.
  27. [27]
    [PDF] Permutation - OU Math
    Permutations. 1. Definition (Permutation). A permutation of a set A is a bijective function f : A → A. The set of all permutations of A is denoted by Perm(A).
  28. [28]
    Combinations and permutations - Mathplanet
    The number of permutations of n objects taken r at a time is determined by the following formula: P(n,r)=n! (n−r)! n! is read n factorial and means all numbers ...
  29. [29]
    [PDF] Inversions of Permutations in Symmetric, Alternating, and Dihedral ...
    This establishes the theorem. A permutation σ is said to be even if N(σ) is even, otherwise it is said to be odd. Let. An ...
  30. [30]
    [PDF] The symmetric group
    Definition 1.3. The symmetric group Sn is the group Perm({1,...,n}) of all permutations on the first n integers. Lemma 1.2. If |S| = n then Perm(S) ≈ Sn.
  31. [31]
    [PDF] Generating functions in probability and combinatorics - Penn Math
    To use the exponential formula, one needs exponential generating functions to input. Example 2.5 (egf for permutations). The number of permutations of [n] is n!
  32. [32]
    Heap's Algorithm for generating permutations - GeeksforGeeks
    Dec 14, 2022 · Heap's algorithm is used to generate all permutations of n objects. The idea is to generate each permutation from the previous permutation ...
  33. [33]
    [PDF] 1. Introduction - Enumerative Combinatorics and Applications
    Jan 1, 2021 · As happened with several topics, Euler returned to derangements much later in his career. He presented. E738 in 1779—he died in 1783 and there ...
  34. [34]
    Permutation Cipher - Crypto Corner - Interactive Maths
    The Permutation Cipher is another form of Transposition Cipher. It is similar to Columnar Transposition in some ways, in that the columns are written in the ...
  35. [35]
    7.6 Probability with Permutations and Combinations - OpenStax
    Mar 22, 2023 · Recall that we can use permutations to count how many ways there are to put a number of items from a list in order.
  36. [36]
    What is a Vapor Perm? - GreenBuildingAdvisor
    Jun 19, 2019 · 1 grain of water moving through 1 square foot of a material in 1 hour at a vapor pressure difference of 1 inch of mercury was the right measure.
  37. [37]
    Perm | UpCodes
    Unit of measurement of the water vapor permeance of materials. Value of one perm is equal to one grain of water vapor per square foot hour per inch of mercury ...Missing: history | Show results with:history
  38. [38]
    Perm (US Grain·h⁻¹·ft⁻²·inHg⁻¹): Measuring Water Vapor Permeance
    Oct 30, 2025 · The perm quantifies water vapor permeance through a material. In the US customary system, 1 perm equals the passage of one grain of water per ...
  39. [39]
    What is the unit called a perm? - Sizes
    Apr 26, 2017 · Vapour permeance is a measure of the ease of vapour flow through a material layer, in units of perms (equal to 1 ng/Pa s m2 or 1 grain/(hr·in Hg ...<|separator|>
  40. [40]
    Definitions of Units for the Permeation, Permeance, Water Vapor ...
    1 metric perm = 1.51735 US perms ≈ 86.8127 ng·s⁻¹·m⁻²·Pa⁻¹. The equivalent SI measure is the nanogram per second per square meter per pascal. 1 ng·s⁻¹·m⁻²·Pa⁻¹ ...
  41. [41]
    Vapor Barriers or Vapor Retarders - Department of Energy
    The ability of a material to retard the diffusion of water vapor is measured in units known as "perms" or permeability. The International Residential Code ...
  42. [42]
    Moisture Control | Vapor Retarders- Installing, Perm Ratings
    Class I – Very low permeability vapor retarders – rated at 0.1 perms or less. · Class II – Low permeability vapor retarders – rated greater than 0.1 perms and ...
  43. [43]
    The Importance of Vapor Retarders on Chilled Water Insulation ...
    May 12, 2020 · A lower perm value indicates better water vapor resistance. A vapor retarder with a perm rating of 0.0 perms would provide undetectable moisture ...Missing: construction | Show results with:construction
  44. [44]
    [PDF] A Guide to Vapor Retarder Design In Low-Slope Roof Systems ...
    Vapor retarders are commonly used in low-slope roof assemblies to prevent moisture-laden air in a building's interior from moving into the roof assembly where ...
  45. [45]
    [PDF] Moisture Control Guidance for Building Design, Construction and ...
    or foam board insulation, non-vented low-slope roofs may need a vapor retarder with a lower perm rating than that of the roofing membrane. Special analysis ...
  46. [46]
    Permanent Hair Wave - Chemistry LibreTexts
    Jul 4, 2022 · In the permanent wave process, a basic reducing substance (usually ammonium thioglycolate) is first added to reduce and rupture some of the ...
  47. [47]
    How does a perm work? - Yale Scientific Magazine
    Apr 24, 2010 · In a standard “cold” perm, hair is put into curlers and the reducing agent ammonium thioglycolate is added. The disulfide bonds break and keratin molecules are ...Missing: treatment | Show results with:treatment
  48. [48]
    How Long Does a Perm Last? And 12 Other FAQs on ... - Healthline
    Dec 17, 2018 · A perm typically lasts three to six months, depending on your hair type and how well you take care of it.Overview · Contributing factors · Types · Preparation
  49. [49]
    Hair Historians Celebrate 100 Years of the Perm - NPR
    Mar 16, 2006 · Nessler applied sodium hydroxide to his wife's hair and wrapped it in heated brass rods connected to a chandelier. As the story goes, his wife ...
  50. [50]
    A History of the Perm Hairstyle - Glamour Daze
    Mar 26, 2018 · A wave machine, producing even longer lasting results was premiered by Swiss hairdresser Karl Nessler ( Charles Nestle) in 1906 in England.
  51. [51]
    Perm Hairstyle: The Favorite Hairdo of Young Women in the 1980s
    Nov 1, 2018 · The “perm” or permanent wave was the hair to have in the 80s. The perm transitioned everyone from updos and straight to full out curl.
  52. [52]
    Ultimate guide to different types of perms - Verb Products
    Mar 4, 2025 · Most perms last between three and six months, but this can vary based on many factors like the type of perm you get and the length of your hair.What is a perm? · How do perms work? · Types of perms
  53. [53]
    https://vtda.org/pubs/BSTJ/vol02-1923/articles/bstj2-3-101.pdf
  54. [54]
    [PDF] Permanent Waving - California Board of Barbering and Cosmetology
    Burns: Chemicals in some perm solutions can cause burns if they get on your skin or in your eyes.
  55. [55]
    What is a digital hair perm? How to replicate K-pop idols' dreamy ...
    Sep 7, 2025 · Originating in Japan and perfected in South Korea, the technique uses heated ceramic rods alongside a chemical solution that restructures the ...
  56. [56]
    Dolly Parton's Iconic Hair Through the Years - SheKnows
    Jan 19, 2025 · 1989: Gorgeous Perm. Okay, but this ultra-long, perm hairdo that Dolly Parton wowed in on the Tonight Show in 1989 needs to be talked about more ...Dolly Parton's Most Dramatic... · 1978: Curled Bob · 2023: Curling Updo
  57. [57]
    Exploring 1980s Hairstyles: From the Mullet to the Perm - wellbrick
    Feb 8, 2024 · From pop stars like Madonna to TV icons like Dolly Parton, big hair was everywhere in the '80s, symbolizing excess and extravagance. 4. The ...
  58. [58]
    Permalloy - Soft Magnetic Alloys
    After a prolonged search, Permalloy was discovered in 1914 by Gustav Elmen of Bell Laboratories, who found it had higher permeability than silicon steel.Missing: historical | Show results with:historical
  59. [59]
    Permalloy, A New Magnetic Material of Very High Permeability - 1923
    The magnetic alloy described in this paper is a composition of about 78.5% nickel and 21.5% iron and at magnetizing fields in the neighborhood of .04 gauss.Missing: summary | Show results with:summary
  60. [60]
    [PDF] Permalloy, A New Magnetic Material of Very High Permeability
    SYNOPSIS: The magnetic alloy described in this paper is a composition of about 78.5% nickel and 21.5% iron and at magnetizing fields in the neighborhood of .04 ...Missing: 1914 applications
  61. [61]
    Permalloy Composition Explained: Properties, Uses, Sourcing Tips
    Feb 18, 2025 · A permalloy composition, which is primarily made up of 80% nickel (Ni) and 20% iron (Fe), offers outstanding permeability and low coercivity ...Missing: 1914 | Show results with:1914
  62. [62]
    Tailoring magnetic hysteresis of additive manufactured Fe-Ni ...
    Jun 12, 2023 · The Fe-Ni permalloy has been widely studied in recent decades owing to its extraordinary magnetic permeability, low coercivity, high saturation ...
  63. [63]
    Mu 80-Mumetal-Permalloy 80 | NiWire Industries Co., Ltd.
    This vacuum-melted product also offers the advantages of small size and weight in magnetic core and shielding materials. Due to its high magnetic ...Missing: metal variant
  64. [64]
    Permalloy 80 - ESPI Metals
    This vacuum-melted product also offers the advantages of small size and weight in magnetic core and shielding materials for the applications shown below.Missing: mu- | Show results with:mu-
  65. [65]
    Permalloy: A Versatile Magnetic Alloy for Wide-Ranging Applications
    Apr 13, 2025 · Permalloy, an alloy primarily composed of nickel and iron, possesses high permeability and low coercivity, making it an indispensable material in various ...Missing: discovery 1914 composition historical
  66. [66]
    The Vacuum Tube's Forgotten Rival - IEEE Spectrum
    Mar 27, 2022 · The 1950s and '60s saw a renaissance for magnetic amplifiers, during which they were used extensively in the military, aerospace, and other industries.Missing: WWII | Show results with:WWII
  67. [67]
    Switching Properties of Permalloy Cores of Varying Coercivity
    In attempting to develop a 4–79 molybdenum Permalloy core for use in a memory with nondestructive readout, studies have been made of switching properties of
  68. [68]
    [PDF] Molypermalloy sends clear signals
    Permalloy wrapping increased the cable's transmission speed from 40 to 400 words per minute. During the early 20th century, loading coils found new ...
  69. [69]
    Permanent Labor Certification | U.S. Department of Labor
    A permanent labor certification issued by the Department of Labor (DOL) allows an employer to hire a foreign worker to work permanently in the United States.
  70. [70]
    Permanent Labor Certification (PERM) | Flag.dol.gov
    A PERM is a DOL certification allowing a U.S. employer to hire a foreign worker permanently, requiring a valid FEIN and a location for U.S. workers.
  71. [71]
    PERM Processing Times Explained: What to Expect in 2025
    Understand PERM processing times in 2025. Learn how long each stage takes, what causes delays, and strategies to help clients plan for Green Card success.<|control11|><|separator|>
  72. [72]
    Chapter 4 - Ability to Pay - USCIS
    Mar 15, 2023 · Many employers satisfy the ability to pay requirement by submitting the initial required evidence described below together with payroll records ...
  73. [73]
    Permanent Workers | USCIS
    Jan 24, 2025 · In these cases, the immigrant petition must include a signed Form ETA-9089, Application for Permanent Employment Certification, approved by DOL, ...
  74. [74]
    https://www.fragomen.com/insights/united-states-dol-announces-accommodations-for-perm-and-other-filings-impacted-by-the-government-shutdown.html