内圧

WordNet

the force applied to a unit area of surface; measured in pascals (SI unit) or in dynes (cgs unit); "the compressed gas exerts an increased pressure" (同)pressure level, force per unit area
an oppressive condition of physical or mental or social or economic distress
the somatic sensation that results from applying force to an area of skin; "the sensitivity of his skin to pressure and temperature was normal" (同)pressure_sensation
a force that compels; "the public brought pressure to bear on the government"
work as an intern; "The young doctor is interning at the Medical Center this year"
an advanced student or graduate in medicine gaining supervised practical experience (`houseman is a British term) (同)interne, houseman, medical intern
deprive of freedom; "During WW II, Japanese were interned in camps in the West"
happening or arising or located within some limits or especially surface; "internal organs"; "internal mechanism of a toy"; "internal party maneuvering"
occurring within an institution or community; "intragroup squabbling within the corporation" (同)intragroup

PrepTutorEJDIC

〈U〉『押すこと』,『押しつけること』,圧搾,圧縮;〈C〉〈U〉『圧力』,圧力の強さ / 〈U〉『圧迫』,『強制』 / 〈U〉(不快な)圧迫感 / 〈C〉〈U〉(精神的な)重荷,苦脳;(時間・金銭的)切迫 / 〈U〉多忙,あわただしさ / 《おもに米》…‘に'圧力をかける,強制する(《英》pressurise)
(特に戦時中)〈人・船など〉‘を'強制収容する,抑留する
『内側の』,内部にある / 『国内の』(domestic) / 内からとる,内用の

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/04/29 21:30:53」(JST)

wiki en

Internal pressure is a measure of how the internal energy of a system changes when it expands or contracts at constant temperature. It has the same dimensions as pressure, the SI unit of which is the pascal.

Internal pressure is usually given the symbol . It is defined as a partial derivative of internal energy with respect to volume at constant temperature:

Thermodynamic equation of state

Internal pressure can be expressed in terms of temperature, pressure and their mutual dependence:

This equation is known as the thermodynamic equation of state for it expresses pressure in terms of thermodynamic properties of the system.

Derivation of the thermodynamic equation of state

Internal energy is a state function, therefore its differential is exact. We can take it to be a function of other state functions, namely entropy S and volume V:

.

Dividing this equation by at constant temperature gives:

Comparing the above differential with the fundamental thermodynamic equation

gives

and .

This, and the definition of internal pressure, leads to

One of the Maxwell relations states that

Inserting this into the above relation completes the proof.

Perfect gas

In a perfect gas, there are no potential energy interactions between the particles, so any change in the internal energy of the gas is directly proportional to the change in the kinetic energy of its constituent species and therefore also to the change in temperature:

.

The internal pressure is taken to be at constant temperature, therefore

, which implies and finally ,

i.e. the internal energy of a perfect gas is independent of the volume it occupies. The above relation can be used as a definition of a perfect gas.

The relation can be proved without the need to invoke any molecular arguments. It follows directly from the thermodynamic equation of state if we use the ideal gas law .

Real gases

Plot of internal energy vs. volume for gases with different internal pressures

Real gases have non-zero internal pressures because their internal energy changes as the gases expand isothermally - it can increase on expansion (, signifying presence of dominant attractive forces between the particles of the gas) or decrease (,dominant repulsion).

In the limit of infinite volume these internal pressures reach the value of zero:

,

corresponding to the fact that all real gases can be approximated to be perfect in the limit of a suitably large volume. The above considerations are summarized on the graph on the right.

If a real gas can be described by the van der Waals equation of state

it follows from the thermodynamic equation of state that

Since the parameter is always positive, so is its internal pressure: internal energy of a van der Waals gas always increases when it expands isothermally.

The Joule experiment

James Joule tried to measure the internal pressure of air in his expansion experiment by isothermally pumping high pressure air from one metal vessel into another evacuated one. The water bath in which the system was immersed did not change its temperature, signifying that that no change in the internal energy occurred, the internal pressure of the air was equal to zero and the air was a perfect gas. The actual deviations from the perfect behaviour were not observed since they are very small and the specific heat capacity of water is relatively high.

References

Peter Atkins and Julio de Paula, Physical Chemistry 8th edition, pp. 60–61

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 頸動脈内膜剥離術および頸動脈ステント留置術の麻酔 anesthesia for carotid endarterectomy and carotid stenting
2. 成人における頭蓋内圧亢進の評価およびマネージメント evaluation and management of elevated intracranial pressure in adults
3. 小児における頭蓋内圧亢進（ICP） elevated intracranial pressure icp in children
4. 成人における24時間携帯血圧および家庭血圧測定ならびに白衣高血圧症 ambulatory and home blood pressure monitoring and white coat hypertension in adults
5. 正常圧水頭症 normal pressure hydrocephalus

English Journal

Assessment of central blood pressure in patients with type 2 diabetes: a comparison between sphygmocor and invasively measured values.

Laugesen E, Rossen NB, Peters CD, Mæng M, Ebbehøj E, Knudsen ST, Hansen KW, Bøtker HE, Poulsen PL.Author information Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark.AbstractBACKGROUND: The SphygmoCor is used for noninvasive assessment of ascending aortic blood pressure (BP). However, the validity of the SphygmoCor transfer function has not been tested in an exclusively type 2 diabetic patient sample. Calibration with systolic (SBP) and diastolic (DBP) brachial BP has previously been associated with substantial imprecision of central BP estimates. We hypothesized that different noninvasive calibration strategies might improve the accuracy of the estimated ascending aortic BPs.
American journal of hypertension.Am J Hypertens.2014 Feb;27(2):169-76. doi: 10.1093/ajh/hpt195. Epub 2013 Dec 4.
BACKGROUND: The SphygmoCor is used for noninvasive assessment of ascending aortic blood pressure (BP). However, the validity of the SphygmoCor transfer function has not been tested in an exclusively type 2 diabetic patient sample. Calibration with systolic (SBP) and diastolic (DBP) brachial BP has p
PMID 24304654

Response to cold pressor test predicts long-term changes in pulse wave velocity in men.

Bellinazzi VR, Sposito AC, Schreiber R, Mill JG, Krieger JE, Pereira AC, Nadruz W Jr.Author information Department of Internal Medicine, University of Campinas, Campinas, Brazil.AbstractBACKGROUND: Aortic stiffness is associated with increased cardiovascular mortality. However, the determinants of aortic stiffness progression are not fully established. This study evaluated the predictive value of blood pressure (BP) response to cold pressor test (CPT) in the progression of carotid-femoral pulse wave velocity (PWV) in men and women.
American journal of hypertension.Am J Hypertens.2014 Feb;27(2):157-61. doi: 10.1093/ajh/hpt213. Epub 2013 Nov 12.
BACKGROUND: Aortic stiffness is associated with increased cardiovascular mortality. However, the determinants of aortic stiffness progression are not fully established. This study evaluated the predictive value of blood pressure (BP) response to cold pressor test (CPT) in the progression of carotid-
PMID 24222667

Assessment of volume status and arterial stiffness in chronic kidney disease.

Akdam H, Oğünç H, Alp A, Ozbek O, Omürlü IK, Yeniçerioğlu Y, Akar H.Author information Division of Nephrology, Department of Internal Medicine, Faculty of Medicine, Adnan Menderes University , Aydın , Turkey .AbstractAbstract Aim: There is limited information about arterial stiffness in chronic kidney disease (CKD) which is an independent risk factor for cardiovascular events. Pulse wave velocity (PWV), augmentation index (AIx) are using to determine arterial stiffness. We aimed to study PWV, AIx, volume status in patients with stage 3B-5 CKD and continuous ambulatory peritoneal dialysis (CAPD). Methods: Sixty-six stage 3B-5 CKD patients, 21 CAPD patients, 34 healthy controls were included. Pulse wave velocity, AIx, volume status was evaluated by Mobil-O-Graph®, and bioimpedance spectroscopy, respectively. Results: The Median PWV was 7.5 m/s in CKD, 6.2 m/s in CAPD, 5.9 m/s in healthy controls, and while PWV was found to have increased significantly in CKD patients (p = 0.002), the Alx values were similar in all groups. The median extracellular fluid excess was higher in both the CKD and, CAPD patients when compared with healthy controls (1.26 and 1.21 L, respectively). Overhydration was more prevalent in CKD and CAPD patients (p < 0.001). Age, central systolic blood pressure, body mass index, fat mass, overhydration, CKD, eGFR were the major determinants of PWV. Conclusion: Increased PWV was found in stage 3B-5 CKD patients. Overhydration may contribute this increment.
Renal failure.Ren Fail.2014 Feb;36(1):28-34. doi: 10.3109/0886022X.2013.830224. Epub 2013 Sep 13.
Abstract Aim: There is limited information about arterial stiffness in chronic kidney disease (CKD) which is an independent risk factor for cardiovascular events. Pulse wave velocity (PWV), augmentation index (AIx) are using to determine arterial stiffness. We aimed to study PWV, AIx, volume status
PMID 24028203